feat: add toolbox contract shell and testkit

2026-07-20 17:53:56 +02:00
commit ce9bddb218
53 changed files with 8950 additions and 0 deletions
--- a/.gitignore
+++ b/.gitignore
@@ -0,0 +1,5 @@
+node_modules/
+dist/
+coverage/
+*.tsbuildinfo
+.DS_Store
--- a/.npmrc
+++ b/.npmrc
@@ -0,0 +1 @@
+@add-ideas:registry=https://git.add-ideas.de/api/packages/zemion/npm/
--- a/.prettierignore
+++ b/.prettierignore
@@ -0,0 +1,4 @@
+dist
+coverage
+node_modules
+package-lock.json
--- a/.prettierrc.json
+++ b/.prettierrc.json
@@ -0,0 +1,4 @@
+{
+  "proseWrap": "always",
+  "trailingComma": "all"
+}
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -0,0 +1,21 @@
+# Changelog
+
+All notable changes to the independently versioned Toolbox SDK packages are
+recorded here. The packages currently share one release version.
+
+## 0.1.0 — 2026-07-20
+
+### Added
+
+- `@add-ideas/toolbox-contract` with v1 app and catalog types, published JSON
+  Schemas, strict forward-compatible runtime parsing, same-origin context
+  discovery, hydrated catalog loading, resolved URL helpers, and graceful result
+  types.
+- `@add-ideas/toolbox-shell-react` with the standalone-safe `AppShell`, built-in
+  light/dark/system theme, app metadata and privacy display, actions, toolbox
+  home, and accessible full-page app switching.
+- `@add-ideas/toolbox-testkit` with the `toolbox-check` CLI for manifest/assets,
+  unsafe-path detection, nested-prefix resource checks, and standalone/context
+  HTTP smoke tests.
+- React integration and manifest/catalog examples, Vitest/jsdom coverage, and
+  workspace build, typecheck, lint, formatting, and package scripts.
--- a/192
+++ b/192
@@ -0,0 +1,192 @@
+                                 Apache License
+                           Version 2.0, January 2004
+                        http://www.apache.org/licenses/
+
+   TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION
+
+   1. Definitions.
+
+      "License" shall mean the terms and conditions for use, reproduction,
+      and distribution as defined by Sections 1 through 9 of this document.
+
+      "Licensor" shall mean the copyright owner or entity authorized by
+      the copyright owner that is granting the License.
+
+      "Legal Entity" shall mean the union of the acting entity and all
+      other entities that control, are controlled by, or are under common
+      control with that entity. For the purposes of this definition,
+      "control" means (i) the power, direct or indirect, to cause the
+      direction or management of such entity, whether by contract or
+      otherwise, or (ii) ownership of fifty percent (50%) or more of the
+      outstanding shares, or (iii) beneficial ownership of such entity.
+
+      "You" (or "Your") shall mean an individual or Legal Entity
+      exercising permissions granted by this License.
+
+      "Source" form shall mean the preferred form for making modifications,
+      including but not limited to software source code, documentation
+      source, and configuration files.
+
+      "Object" form shall mean any form resulting from mechanical
+      transformation or translation of a Source form, including but
+      not limited to compiled object code, generated documentation,
+      and conversions to other media types.
+
+      "Work" shall mean the work of authorship, whether in Source or
+      Object form, made available under the License, as indicated by a
+      copyright notice that is included in or attached to the work
+      (an example is provided in the Appendix below).
+
+      "Derivative Works" shall mean any work, whether in Source or Object
+      form, that is based on (or derived from) the Work and for which the
+      editorial revisions, annotations, elaborations, or other modifications
+      represent, as a whole, an original work of authorship. For the purposes
+      of this License, Derivative Works shall not include works that remain
+      separable from, or merely link (or bind by name) to the interfaces of,
+      the Work and Derivative Works thereof.
+
+      "Contribution" shall mean any work of authorship, including
+      the original version of the Work and any modifications or additions
+      to that Work or Derivative Works thereof, that is intentionally
+      submitted to Licensor for inclusion in the Work by the copyright owner
+      or by an individual or Legal Entity authorized to submit on behalf of
+      the copyright owner. For the purposes of this definition, "submitted"
+      means any form of electronic, verbal, or written communication sent
+      to the Licensor or its representatives, including but not limited to
+      communication on electronic mailing lists, source code control systems,
+      and issue tracking systems that are managed by, or on behalf of, the
+      Licensor for the purpose of discussing and improving the Work, but
+      excluding communication that is conspicuously marked or otherwise
+      designated in writing by the copyright owner as "Not a Contribution."
+
+      "Contributor" shall mean Licensor and any individual or Legal Entity
+      on behalf of whom a Contribution has been received by Licensor and
+      subsequently incorporated within the Work.
+
+   2. Grant of Copyright License. Subject to the terms and conditions of
+      this License, each Contributor hereby grants to You a perpetual,
+      worldwide, non-exclusive, no-charge, royalty-free, irrevocable
+      copyright license to reproduce, prepare Derivative Works of,
+      publicly display, publicly perform, sublicense, and distribute the
+      Work and such Derivative Works in Source or Object form.
+
+   3. Grant of Patent License. Subject to the terms and conditions of
+      this License, each Contributor hereby grants to You a perpetual,
+      worldwide, non-exclusive, no-charge, royalty-free, irrevocable
+      (except as stated in this section) patent license to make, have made,
+      use, offer to sell, sell, import, and otherwise transfer the Work,
+      where such license applies only to those patent claims licensable
+      by such Contributor that are necessarily infringed by their
+      Contribution(s) alone or by combination of their Contribution(s)
+      with the Work to which such Contribution(s) was submitted. If You
+      institute patent litigation against any entity (including a
+      cross-claim or counterclaim in a lawsuit) alleging that the Work
+      or a Contribution incorporated within the Work constitutes direct
+      or contributory patent infringement, then any patent licenses
+      granted to You under this License for that Work shall terminate
+      as of the date such litigation is filed.
+
+   4. Redistribution. You may reproduce and distribute copies of the
+      Work or Derivative Works thereof in any medium, with or without
+      modifications, and in Source or Object form, provided that You
+      meet the following conditions:
+
+      (a) You must give any other recipients of the Work or
+          Derivative Works a copy of this License; and
+
+      (b) You must cause any modified files to carry prominent notices
+          stating that You changed the files; and
+
+      (c) You must retain, in the Source form of any Derivative Works
+          that You distribute, all copyright, patent, trademark, and
+          attribution notices from the Source form of the Work,
+          excluding those notices that do not pertain to any part of
+          the Derivative Works; and
+
+      (d) If the Work includes a "NOTICE" text file as part of its
+          distribution, then any Derivative Works that You distribute must
+          include a readable copy of the attribution notices contained
+          within such NOTICE file, excluding those notices that do not
+          pertain to any part of the Derivative Works, in at least one
+          of the following places: within a NOTICE text file distributed
+          as part of the Derivative Works; within the Source form or
+          documentation, if provided along with the Derivative Works; or,
+          within a display generated by the Derivative Works, if and
+          wherever such third-party notices normally appear. The contents
+          of the NOTICE file are for informational purposes only and
+          do not modify the License. You may add Your own attribution
+          notices within Derivative Works that You distribute, alongside
+          or as an addendum to the NOTICE text from the Work, provided
+          that such additional attribution notices cannot be construed
+          as modifying the License.
+
+      You may add Your own copyright statement to Your modifications and
+      may provide additional or different license terms and conditions
+      for use, reproduction, or distribution of Your modifications, or
+      for any such Derivative Works as a whole, provided Your use,
+      reproduction, and distribution of the Work otherwise complies with
+      the conditions stated in this License.
+
+   5. Submission of Contributions. Unless You explicitly state otherwise,
+      any Contribution intentionally submitted for inclusion in the Work
+      by You to the Licensor shall be under the terms and conditions of
+      this License, without any additional terms or conditions.
+      Notwithstanding the above, nothing herein shall supersede or modify
+      the terms of any separate license agreement you may have executed
+      with Licensor regarding such Contributions.
+
+   6. Trademarks. This License does not grant permission to use the trade
+      names, trademarks, service marks, or product names of the Licensor,
+      except as required for reasonable and customary use in describing the
+      origin of the Work and reproducing the content of the NOTICE file.
+
+   7. Disclaimer of Warranty. Unless required by applicable law or
+      agreed to in writing, Licensor provides the Work (and each
+      Contributor provides its Contributions) on an "AS IS" BASIS,
+      WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
+      implied, including, without limitation, any warranties or conditions
+      of TITLE, NON-INFRINGEMENT, MERCHANTABILITY, or FITNESS FOR A
+      PARTICULAR PURPOSE. You are solely responsible for determining the
+      appropriateness of using or redistributing the Work and assume any
+      risks associated with Your exercise of permissions under this License.
+
+   8. Limitation of Liability. In no event and under no legal theory,
+      whether in tort (including negligence), contract, or otherwise,
+      unless required by applicable law (such as deliberate and grossly
+      negligent acts) or agreed to in writing, shall any Contributor be
+      liable to You for damages, including any direct, indirect, special,
+      incidental, or consequential damages of any character arising as a
+      result of this License or out of the use or inability to use the
+      Work (including but not limited to damages for loss of goodwill,
+      work stoppage, computer failure or malfunction, or any and all
+      other commercial damages or losses), even if such Contributor
+      has been advised of the possibility of such damages.
+
+   9. Accepting Warranty or Additional Liability. While redistributing
+      the Work or Derivative Works thereof, You may choose to offer,
+      and charge a fee for, acceptance of support, warranty, indemnity,
+      or other liability obligations and/or rights consistent with this
+      License. However, in accepting such obligations, You may act only
+      on Your own behalf and on Your sole responsibility, not on behalf
+      of any other Contributor, and only if You agree to indemnify,
+      defend, and hold each Contributor harmless for any liability
+      incurred by, or claims asserted against, such Contributor by reason
+      of your accepting any such warranty or additional liability.
+
+   END OF TERMS AND CONDITIONS
+
+   APPENDIX: How to apply the Apache License to your work.
+
+      Copyright 2026 ADD Ideas
+
+      Licensed under the Apache License, Version 2.0 (the "License");
+      you may not use this file except in compliance with the License.
+      You may obtain a copy of the License at
+
+          http://www.apache.org/licenses/LICENSE-2.0
+
+      Unless required by applicable law or agreed to in writing, software
+      distributed under the License is distributed on an "AS IS" BASIS,
+      WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+      See the License for the specific language governing permissions and
+      limitations under the License.
--- a/README.md
+++ b/README.md
@@ -0,0 +1,231 @@
+# Toolbox SDK
+
+Toolbox SDK defines a small, versioned contract for independently deployed web
+tools. An app always works by itself. When it receives a trusted same-origin
+catalog URL, the same app gains a toolbox home link and an app switcher without
+becoming coupled to a portal or client-side router.
+
+Version `0.1.0` contains three publish-ready packages:
+
+- `@add-ideas/toolbox-contract` — types, strict v1 runtime parsing, context
+  discovery/loading, resolved URLs, and contextual link helpers.
+- `@add-ideas/toolbox-shell-react` — `AppShell` plus the v1 CSS theme.
+- `@add-ideas/toolbox-testkit` — the `toolbox-check <dist>` build validation and
+  nested-path smoke-test CLI.
+
+The project is licensed under Apache-2.0. That permissive license was chosen in
+particular for its explicit patent grant.
+
+## Install
+
+The repository includes a token-free `.npmrc` pointing the `@add-ideas` scope at
+the ADD Ideas package registry. Supply registry credentials through your normal
+user/CI npm configuration; never add them to this repository.
+
+```sh
+npm install @add-ideas/toolbox-contract @add-ideas/toolbox-shell-react
+npm install --save-dev @add-ideas/toolbox-testkit
+```
+
+React and ReactDOM are peer dependencies of the shell (`>=18 <20`).
+
+## Application manifest v1
+
+Deploy `toolbox-app.json` beside the application entry. The canonical schema is
+[`schemas/toolbox-app.v1.schema.json`](./schemas/toolbox-app.v1.schema.json).
+
+```json
+{
+  "$schema": "https://git.add-ideas.de/zemion/toolbox-sdk/raw/branch/main/schemas/toolbox-app.v1.schema.json",
+  "schemaVersion": 1,
+  "id": "de.add-ideas.pdf-tools",
+  "name": "PDF Workbench",
+  "version": "0.3.4",
+  "description": "Page-level PDF operations performed locally in the browser.",
+  "entry": "./",
+  "icon": "./favicon.svg",
+  "categories": ["documents", "pdf"],
+  "tags": ["merge", "split", "rotate"],
+  "integration": {
+    "contextVersion": 1,
+    "launchModes": ["navigate", "new-tab"],
+    "embedding": "unsupported"
+  },
+  "requirements": {
+    "secureContext": true,
+    "workers": true,
+    "indexedDb": true,
+    "crossOriginIsolated": false
+  },
+  "privacy": {
+    "processing": "local",
+    "fileUploads": false,
+    "telemetry": false
+  },
+  "source": {
+    "repository": "https://git.add-ideas.de/zemion/pdf-tools",
+    "license": "AGPL-3.0-only"
+  }
+}
+```
+
+`source`, `privacy.label`, `privacy.url`, `requirements.topLevelContext`,
+`actions`, and `assets` are optional v1 additions. `toolbox-check` verifies the
+entry, icon, and every declared asset. Runtime parsers validate every known
+field, require `schemaVersion: 1`, and deliberately discard unknown fields so
+future optional additions do not break v1 consumers.
+
+For typed source definitions, use the literal-preserving identity helper:
+
+```ts
+import { defineToolboxApp } from "@add-ideas/toolbox-contract";
+
+export const manifest = defineToolboxApp({
+  // The same fields as toolbox-app.json.
+});
+```
+
+Use `parseToolboxApp(unknownValue)` at trust boundaries; `defineToolboxApp()` is
+compile-time only and does not replace runtime parsing.
+
+## Catalog v1
+
+The canonical schema is
+[`schemas/toolbox-catalog.v1.schema.json`](./schemas/toolbox-catalog.v1.schema.json).
+A catalog owns its home and theme. Manifest references resolve relative to the
+catalog. An external entry may be declared inline when no toolbox manifest is
+available.
+
+```json
+{
+  "schemaVersion": 1,
+  "id": "de.add-ideas.toolbox",
+  "name": "add·ideas Toolbox",
+  "home": "./",
+  "theme": { "mode": "system", "brand": "add·ideas" },
+  "apps": [
+    { "manifest": "./apps/pdf/toolbox-app.json", "enabled": true },
+    {
+      "name": "Documentation",
+      "entry": "https://docs.example.org/",
+      "launch": "new-tab",
+      "enabled": true
+    }
+  ]
+}
+```
+
+Disabled entries remain in the parsed catalog but are not fetched or exposed in
+the resolved app list. `loadToolboxCatalog()` fetches enabled manifests and
+returns resolved manifest, entry, icon, asset, action, privacy, home, and
+external-entry URLs.
+
+## Context discovery and security
+
+An app discovers context in this order:
+
+1. `?toolbox=/toolbox.catalog.json`
+2. `<meta name="toolbox" content="/toolbox.catalog.json">`
+3. standalone mode when neither exists
+
+The query parameter takes precedence. Discovered catalog URLs and their manifest
+documents must share the current page origin; cross-origin values are rejected
+before fetch. Credential-bearing and non-HTTP(S) URLs are rejected. Unknown,
+invalid, or unavailable context is returned as a discriminated error, not an
+uncaught rejection:
+
+```ts
+import { loadToolboxContext } from "@add-ideas/toolbox-contract";
+
+const result = await loadToolboxContext();
+if (result.status === "ready") {
+  console.log(result.context.catalog.apps);
+} else if (result.status === "standalone") {
+  console.log("No toolbox requested");
+} else {
+  console.warn(result.error.code, result.error.message);
+}
+```
+
+`contextualizeToolboxLink(target, catalog, { location })` (also exported as
+`createContextualLink`) adds the context parameter only to same-origin targets.
+External targets are resolved but never decorated with the context URL.
+
+## React shell
+
+```tsx
+import { AppShell } from "@add-ideas/toolbox-shell-react";
+import "@add-ideas/toolbox-shell-react/styles.css";
+
+<AppShell
+  app={manifest}
+  manifestUrl="/toolbox-app.json"
+  appActions={<a href="./help/">Help</a>}
+  onContextError={(error) => console.warn(error)}
+>
+  <Application />
+</AppShell>;
+```
+
+The shell always renders app identity as an `h1`, version, derived privacy
+facts, manifest actions, and `appActions`. With valid context it additionally
+renders the catalog brand/home and a switcher at the accessible navigation
+landmark `Toolbox applications`. Destinations are ordinary links, so switching
+performs full-page navigation. On missing, cross-origin, invalid, or unavailable
+context the shell quietly remains usable in standalone mode; `onContextError` is
+optional observability.
+
+CSS custom properties prefixed with `--toolbox-` are the v1 theme surface. The
+catalog `light`, `dark`, or `system` mode selects the built-in palette.
+
+## Validate a build
+
+```json
+{
+  "scripts": {
+    "toolbox:check": "toolbox-check dist"
+  }
+}
+```
+
+`toolbox-check` strictly parses `dist/toolbox-app.json`, checks its id and
+SemVer version, rejects absolute/traversing/escaping local asset paths, verifies
+the entry/icon/assets, serves the build from a deep nested prefix, and
+smoke-fetches both standalone and `?toolbox=/toolbox.catalog.json` modes. It
+also follows local script, stylesheet, image, icon, and web-manifest references
+in the entry HTML (including web-manifest icons), rejecting root-absolute
+references that would break a nested deployment. It uses Node fetch and a
+temporary in-process HTTP server; browser behavior is covered by the shell's
+jsdom tests.
+
+## Contract API
+
+The main exports are:
+
+- Definitions: `ToolboxAppManifest`, `ToolboxCatalog`, their nested and resolved
+  types, `defineToolboxApp()`, and `defineToolboxCatalog()`.
+- Validation: `parseToolboxApp()`, `parseToolboxCatalog()`,
+  `ToolboxValidationError`, and `ToolboxError`.
+- Discovery/loading: `discoverToolboxCatalog()`, `fetchToolboxAppManifest()`,
+  `fetchToolboxCatalog()`, `loadToolboxCatalog()`, and `loadToolboxContext()`.
+- URLs: `resolveWebUrl()`, `resolveToolboxApp()`, `requireSameOrigin()`, and
+  `contextualizeToolboxLink()`.
+
+See each emitted `.d.ts` file for the complete signatures.
+
+## Develop
+
+Requires Node 20 or newer.
+
+```sh
+npm install
+npm run check
+```
+
+`npm run check` runs strict TypeScript checks, ESLint, Prettier verification,
+Vitest/jsdom tests, and all package builds. The workspace uses current versions
+aligned with the consuming apps: React 19.2, TypeScript 6, Vitest 4, and
+ESLint 10.
+
+Package publication is intentionally separate from the build. Authenticate in
+the caller environment, then use npm workspace publishing commands after review.
--- a/eslint.config.js
+++ b/eslint.config.js
@@ -0,0 +1,31 @@
+import eslint from "@eslint/js";
+import reactHooks from "eslint-plugin-react-hooks";
+import globals from "globals";
+import tseslint from "typescript-eslint";
+
+export default tseslint.config(
+  {
+    ignores: ["**/dist/**", "**/coverage/**", "**/node_modules/**"],
+  },
+  eslint.configs.recommended,
+  ...tseslint.configs.recommended,
+  {
+    files: ["**/*.{ts,tsx}"],
+    languageOptions: {
+      globals: {
+        ...globals.browser,
+        ...globals.node,
+      },
+    },
+    rules: {
+      "@typescript-eslint/consistent-type-imports": "error",
+    },
+  },
+  {
+    files: ["**/*.tsx"],
+    plugins: {
+      "react-hooks": reactHooks,
+    },
+    rules: reactHooks.configs.recommended.rules,
+  },
+);
--- a/examples/react-app/README.md
+++ b/examples/react-app/README.md
@@ -0,0 +1,15 @@
+# React integration example
+
+The source files show the intended integration points for an existing React
+application. Copy `public/toolbox-app.json` into the build unchanged (or inject
+the package version during the build), import the shell CSS once, and wrap the
+application in `AppShell`.
+
+In the built application, run:
+
+```sh
+toolbox-check dist
+```
+
+The adjacent example catalog is illustrative. A production catalog normally
+lives at the toolbox home and points to each deployed app manifest.
--- a/examples/react-app/public/icon.svg
+++ b/examples/react-app/public/icon.svg
@@ -0,0 +1,4 @@
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 64 64" role="img" aria-label="Example Tool">
+  <rect width="64" height="64" rx="14" fill="#3156d3" />
+  <path d="M18 20h28v7H18zm0 12h28v7H18zm0 12h18v7H18z" fill="#fff" />
+</svg>
--- a/examples/react-app/public/toolbox-app.json
+++ b/examples/react-app/public/toolbox-app.json
@@ -0,0 +1,32 @@
+{
+  "$schema": "https://git.add-ideas.de/zemion/toolbox-sdk/raw/branch/main/schemas/toolbox-app.v1.schema.json",
+  "schemaVersion": 1,
+  "id": "de.add-ideas.example-tool",
+  "name": "Example Tool",
+  "version": "0.1.0",
+  "description": "A minimal toolbox-compatible React application.",
+  "entry": "./",
+  "icon": "./icon.svg",
+  "categories": ["examples"],
+  "tags": ["react", "toolbox"],
+  "integration": {
+    "contextVersion": 1,
+    "launchModes": ["navigate", "new-tab"],
+    "embedding": "unsupported"
+  },
+  "requirements": {
+    "secureContext": false,
+    "workers": false,
+    "indexedDb": false,
+    "crossOriginIsolated": false
+  },
+  "privacy": {
+    "processing": "local",
+    "fileUploads": false,
+    "telemetry": false
+  },
+  "source": {
+    "repository": "https://git.add-ideas.de/zemion/toolbox-sdk",
+    "license": "Apache-2.0"
+  }
+}
--- a/examples/react-app/public/toolbox.catalog.json
+++ b/examples/react-app/public/toolbox.catalog.json
@@ -0,0 +1,23 @@
+{
+  "$schema": "https://git.add-ideas.de/zemion/toolbox-sdk/raw/branch/main/schemas/toolbox-catalog.v1.schema.json",
+  "schemaVersion": 1,
+  "id": "de.add-ideas.example-toolbox",
+  "name": "Example Toolbox",
+  "home": "./",
+  "theme": {
+    "mode": "system",
+    "brand": "Example Toolbox"
+  },
+  "apps": [
+    {
+      "manifest": "./toolbox-app.json",
+      "enabled": true
+    },
+    {
+      "name": "ADD Ideas",
+      "entry": "https://add-ideas.de/",
+      "launch": "new-tab",
+      "enabled": true
+    }
+  ]
+}
--- a/examples/react-app/src/App.tsx
+++ b/examples/react-app/src/App.tsx
@@ -0,0 +1,19 @@
+import { AppShell } from "@add-ideas/toolbox-shell-react";
+import "@add-ideas/toolbox-shell-react/styles.css";
+
+import { toolboxApp } from "./toolbox-app.js";
+
+export function App() {
+  return (
+    <AppShell app={toolboxApp} appActions={<a href="./help/">Help</a>}>
+      <section>
+        <h2>Ready</h2>
+        <p>
+          Open this app directly for standalone mode, or add
+          <code>?toolbox=/toolbox.catalog.json</code> to connect it to a
+          same-origin catalog.
+        </p>
+      </section>
+    </AppShell>
+  );
+}
--- a/examples/react-app/src/main.tsx
+++ b/examples/react-app/src/main.tsx
@@ -0,0 +1,13 @@
+import { StrictMode } from "react";
+import { createRoot } from "react-dom/client";
+
+import { App } from "./App.js";
+
+const root = document.querySelector("#root");
+if (!root) throw new Error("Missing #root element");
+
+createRoot(root).render(
+  <StrictMode>
+    <App />
+  </StrictMode>,
+);
--- a/examples/react-app/src/toolbox-app.ts
+++ b/examples/react-app/src/toolbox-app.ts
@@ -0,0 +1,33 @@
+import { defineToolboxApp } from "@add-ideas/toolbox-contract";
+
+export const toolboxApp = defineToolboxApp({
+  schemaVersion: 1,
+  id: "de.add-ideas.example-tool",
+  name: "Example Tool",
+  version: "0.1.0",
+  description: "A minimal toolbox-compatible React application.",
+  entry: "./",
+  icon: "./icon.svg",
+  categories: ["examples"],
+  tags: ["react", "toolbox"],
+  integration: {
+    contextVersion: 1,
+    launchModes: ["navigate", "new-tab"],
+    embedding: "unsupported",
+  },
+  requirements: {
+    secureContext: false,
+    workers: false,
+    indexedDb: false,
+    crossOriginIsolated: false,
+  },
+  privacy: {
+    processing: "local",
+    fileUploads: false,
+    telemetry: false,
+  },
+  source: {
+    repository: "https://git.add-ideas.de/zemion/toolbox-sdk",
+    license: "Apache-2.0",
+  },
+});
--- a/package-lock.json
+++ b/package-lock.json
--- a/package.json
+++ b/package.json
@@ -0,0 +1,49 @@
+{
+  "name": "@add-ideas/toolbox-sdk-workspace",
+  "version": "0.1.0",
+  "private": true,
+  "description": "A small, framework-neutral toolbox contract with a React application shell.",
+  "license": "Apache-2.0",
+  "repository": {
+    "type": "git",
+    "url": "git+https://git.add-ideas.de/zemion/toolbox-sdk.git"
+  },
+  "type": "module",
+  "workspaces": [
+    "packages/*"
+  ],
+  "engines": {
+    "node": ">=20"
+  },
+  "scripts": {
+    "build": "npm run build -w @add-ideas/toolbox-contract && npm run build -w @add-ideas/toolbox-shell-react && npm run build -w @add-ideas/toolbox-testkit",
+    "clean": "npm run clean --workspaces --if-present",
+    "typecheck": "npm run typecheck --workspaces --if-present",
+    "test": "vitest run",
+    "test:watch": "vitest",
+    "lint": "eslint . --max-warnings=0",
+    "format": "prettier --check .",
+    "format:write": "prettier --write .",
+    "check": "npm run typecheck && npm run lint && npm run format && npm test && npm run build"
+  },
+  "devDependencies": {
+    "@eslint/js": "^10.0.1",
+    "@testing-library/jest-dom": "^6.9.1",
+    "@testing-library/react": "^16.3.2",
+    "@types/node": "^25.8.0",
+    "@types/react": "^19.2.14",
+    "@types/react-dom": "^19.2.3",
+    "ajv": "^8.20.0",
+    "eslint": "^10.4.0",
+    "eslint-plugin-react-hooks": "^7.1.1",
+    "globals": "^17.6.0",
+    "jsdom": "^29.1.1",
+    "prettier": "^3.8.3",
+    "react": "^19.2.6",
+    "react-dom": "^19.2.6",
+    "typescript": "^6.0.3",
+    "typescript-eslint": "^8.59.3",
+    "vitest": "^4.1.6"
+  },
+  "packageManager": "npm@11.17.0"
+}
--- a/packages/contract/LICENSE
+++ b/packages/contract/LICENSE
@@ -0,0 +1,192 @@
+                                 Apache License
+                           Version 2.0, January 2004
+                        http://www.apache.org/licenses/
+
+   TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION
+
+   1. Definitions.
+
+      "License" shall mean the terms and conditions for use, reproduction,
+      and distribution as defined by Sections 1 through 9 of this document.
+
+      "Licensor" shall mean the copyright owner or entity authorized by
+      the copyright owner that is granting the License.
+
+      "Legal Entity" shall mean the union of the acting entity and all
+      other entities that control, are controlled by, or are under common
+      control with that entity. For the purposes of this definition,
+      "control" means (i) the power, direct or indirect, to cause the
+      direction or management of such entity, whether by contract or
+      otherwise, or (ii) ownership of fifty percent (50%) or more of the
+      outstanding shares, or (iii) beneficial ownership of such entity.
+
+      "You" (or "Your") shall mean an individual or Legal Entity
+      exercising permissions granted by this License.
+
+      "Source" form shall mean the preferred form for making modifications,
+      including but not limited to software source code, documentation
+      source, and configuration files.
+
+      "Object" form shall mean any form resulting from mechanical
+      transformation or translation of a Source form, including but
+      not limited to compiled object code, generated documentation,
+      and conversions to other media types.
+
+      "Work" shall mean the work of authorship, whether in Source or
+      Object form, made available under the License, as indicated by a
+      copyright notice that is included in or attached to the work
+      (an example is provided in the Appendix below).
+
+      "Derivative Works" shall mean any work, whether in Source or Object
+      form, that is based on (or derived from) the Work and for which the
+      editorial revisions, annotations, elaborations, or other modifications
+      represent, as a whole, an original work of authorship. For the purposes
+      of this License, Derivative Works shall not include works that remain
+      separable from, or merely link (or bind by name) to the interfaces of,
+      the Work and Derivative Works thereof.
+
+      "Contribution" shall mean any work of authorship, including
+      the original version of the Work and any modifications or additions
+      to that Work or Derivative Works thereof, that is intentionally
+      submitted to Licensor for inclusion in the Work by the copyright owner
+      or by an individual or Legal Entity authorized to submit on behalf of
+      the copyright owner. For the purposes of this definition, "submitted"
+      means any form of electronic, verbal, or written communication sent
+      to the Licensor or its representatives, including but not limited to
+      communication on electronic mailing lists, source code control systems,
+      and issue tracking systems that are managed by, or on behalf of, the
+      Licensor for the purpose of discussing and improving the Work, but
+      excluding communication that is conspicuously marked or otherwise
+      designated in writing by the copyright owner as "Not a Contribution."
+
+      "Contributor" shall mean Licensor and any individual or Legal Entity
+      on behalf of whom a Contribution has been received by Licensor and
+      subsequently incorporated within the Work.
+
+   2. Grant of Copyright License. Subject to the terms and conditions of
+      this License, each Contributor hereby grants to You a perpetual,
+      worldwide, non-exclusive, no-charge, royalty-free, irrevocable
+      copyright license to reproduce, prepare Derivative Works of,
+      publicly display, publicly perform, sublicense, and distribute the
+      Work and such Derivative Works in Source or Object form.
+
+   3. Grant of Patent License. Subject to the terms and conditions of
+      this License, each Contributor hereby grants to You a perpetual,
+      worldwide, non-exclusive, no-charge, royalty-free, irrevocable
+      (except as stated in this section) patent license to make, have made,
+      use, offer to sell, sell, import, and otherwise transfer the Work,
+      where such license applies only to those patent claims licensable
+      by such Contributor that are necessarily infringed by their
+      Contribution(s) alone or by combination of their Contribution(s)
+      with the Work to which such Contribution(s) was submitted. If You
+      institute patent litigation against any entity (including a
+      cross-claim or counterclaim in a lawsuit) alleging that the Work
+      or a Contribution incorporated within the Work constitutes direct
+      or contributory patent infringement, then any patent licenses
+      granted to You under this License for that Work shall terminate
+      as of the date such litigation is filed.
+
+   4. Redistribution. You may reproduce and distribute copies of the
+      Work or Derivative Works thereof in any medium, with or without
+      modifications, and in Source or Object form, provided that You
+      meet the following conditions:
+
+      (a) You must give any other recipients of the Work or
+          Derivative Works a copy of this License; and
+
+      (b) You must cause any modified files to carry prominent notices
+          stating that You changed the files; and
+
+      (c) You must retain, in the Source form of any Derivative Works
+          that You distribute, all copyright, patent, trademark, and
+          attribution notices from the Source form of the Work,
+          excluding those notices that do not pertain to any part of
+          the Derivative Works; and
+
+      (d) If the Work includes a "NOTICE" text file as part of its
+          distribution, then any Derivative Works that You distribute must
+          include a readable copy of the attribution notices contained
+          within such NOTICE file, excluding those notices that do not
+          pertain to any part of the Derivative Works, in at least one
+          of the following places: within a NOTICE text file distributed
+          as part of the Derivative Works; within the Source form or
+          documentation, if provided along with the Derivative Works; or,
+          within a display generated by the Derivative Works, if and
+          wherever such third-party notices normally appear. The contents
+          of the NOTICE file are for informational purposes only and
+          do not modify the License. You may add Your own attribution
+          notices within Derivative Works that You distribute, alongside
+          or as an addendum to the NOTICE text from the Work, provided
+          that such additional attribution notices cannot be construed
+          as modifying the License.
+
+      You may add Your own copyright statement to Your modifications and
+      may provide additional or different license terms and conditions
+      for use, reproduction, or distribution of Your modifications, or
+      for any such Derivative Works as a whole, provided Your use,
+      reproduction, and distribution of the Work otherwise complies with
+      the conditions stated in this License.
+
+   5. Submission of Contributions. Unless You explicitly state otherwise,
+      any Contribution intentionally submitted for inclusion in the Work
+      by You to the Licensor shall be under the terms and conditions of
+      this License, without any additional terms or conditions.
+      Notwithstanding the above, nothing herein shall supersede or modify
+      the terms of any separate license agreement you may have executed
+      with Licensor regarding such Contributions.
+
+   6. Trademarks. This License does not grant permission to use the trade
+      names, trademarks, service marks, or product names of the Licensor,
+      except as required for reasonable and customary use in describing the
+      origin of the Work and reproducing the content of the NOTICE file.
+
+   7. Disclaimer of Warranty. Unless required by applicable law or
+      agreed to in writing, Licensor provides the Work (and each
+      Contributor provides its Contributions) on an "AS IS" BASIS,
+      WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
+      implied, including, without limitation, any warranties or conditions
+      of TITLE, NON-INFRINGEMENT, MERCHANTABILITY, or FITNESS FOR A
+      PARTICULAR PURPOSE. You are solely responsible for determining the
+      appropriateness of using or redistributing the Work and assume any
+      risks associated with Your exercise of permissions under this License.
+
+   8. Limitation of Liability. In no event and under no legal theory,
+      whether in tort (including negligence), contract, or otherwise,
+      unless required by applicable law (such as deliberate and grossly
+      negligent acts) or agreed to in writing, shall any Contributor be
+      liable to You for damages, including any direct, indirect, special,
+      incidental, or consequential damages of any character arising as a
+      result of this License or out of the use or inability to use the
+      Work (including but not limited to damages for loss of goodwill,
+      work stoppage, computer failure or malfunction, or any and all
+      other commercial damages or losses), even if such Contributor
+      has been advised of the possibility of such damages.
+
+   9. Accepting Warranty or Additional Liability. While redistributing
+      the Work or Derivative Works thereof, You may choose to offer,
+      and charge a fee for, acceptance of support, warranty, indemnity,
+      or other liability obligations and/or rights consistent with this
+      License. However, in accepting such obligations, You may act only
+      on Your own behalf and on Your sole responsibility, not on behalf
+      of any other Contributor, and only if You agree to indemnify,
+      defend, and hold each Contributor harmless for any liability
+      incurred by, or claims asserted against, such Contributor by reason
+      of your accepting any such warranty or additional liability.
+
+   END OF TERMS AND CONDITIONS
+
+   APPENDIX: How to apply the Apache License to your work.
+
+      Copyright 2026 ADD Ideas
+
+      Licensed under the Apache License, Version 2.0 (the "License");
+      you may not use this file except in compliance with the License.
+      You may obtain a copy of the License at
+
+          http://www.apache.org/licenses/LICENSE-2.0
+
+      Unless required by applicable law or agreed to in writing, software
+      distributed under the License is distributed on an "AS IS" BASIS,
+      WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+      See the License for the specific language governing permissions and
+      limitations under the License.
--- a/packages/contract/README.md
+++ b/packages/contract/README.md
@@ -0,0 +1,21 @@
+# @add-ideas/toolbox-contract
+
+Typed, runtime-validated toolbox application manifests and catalogs, plus safe
+same-origin context discovery and URL resolution.
+
+```ts
+import {
+  loadToolboxContext,
+  parseToolboxApp,
+} from "@add-ideas/toolbox-contract";
+
+const app = parseToolboxApp(await response.json());
+const result = await loadToolboxContext();
+```
+
+See the workspace [README](https://git.add-ideas.de/zemion/toolbox-sdk#readme)
+for the v1 document formats and full API.
+
+The canonical schemas are also published at
+`@add-ideas/toolbox-contract/schemas/toolbox-app.v1.schema.json` and
+`@add-ideas/toolbox-contract/schemas/toolbox-catalog.v1.schema.json`.
--- a/packages/contract/package.json
+++ b/packages/contract/package.json
@@ -0,0 +1,48 @@
+{
+  "name": "@add-ideas/toolbox-contract",
+  "version": "0.1.0",
+  "description": "Runtime-validated manifests, catalogs, discovery, and URL helpers for toolbox applications.",
+  "license": "Apache-2.0",
+  "repository": {
+    "type": "git",
+    "url": "git+https://git.add-ideas.de/zemion/toolbox-sdk.git",
+    "directory": "packages/contract"
+  },
+  "homepage": "https://git.add-ideas.de/zemion/toolbox-sdk",
+  "keywords": [
+    "toolbox",
+    "manifest",
+    "catalog",
+    "typescript"
+  ],
+  "type": "module",
+  "sideEffects": false,
+  "engines": {
+    "node": ">=20"
+  },
+  "files": [
+    "dist",
+    "README.md",
+    "LICENSE"
+  ],
+  "exports": {
+    ".": {
+      "types": "./dist/index.d.ts",
+      "import": "./dist/index.js"
+    },
+    "./schemas/toolbox-app.v1.schema.json": "./dist/schemas/toolbox-app.v1.schema.json",
+    "./schemas/toolbox-catalog.v1.schema.json": "./dist/schemas/toolbox-catalog.v1.schema.json",
+    "./package.json": "./package.json"
+  },
+  "types": "./dist/index.d.ts",
+  "scripts": {
+    "build": "tsc -p tsconfig.build.json && node -e \"const fs=require('node:fs');fs.mkdirSync('dist/schemas',{recursive:true});for(const name of ['toolbox-app.v1.schema.json','toolbox-catalog.v1.schema.json'])fs.copyFileSync('../../schemas/'+name,'dist/schemas/'+name);fs.copyFileSync('../../LICENSE','LICENSE')\"",
+    "clean": "node -e \"require('node:fs').rmSync('dist', { recursive: true, force: true })\"",
+    "prepack": "npm run build",
+    "typecheck": "tsc -p tsconfig.json --noEmit"
+  },
+  "publishConfig": {
+    "access": "public",
+    "registry": "https://git.add-ideas.de/api/packages/zemion/npm/"
+  }
+}
--- a/packages/contract/src/discovery.ts
+++ b/packages/contract/src/discovery.ts
@@ -0,0 +1,110 @@
+import {
+  TOOLBOX_META_NAME,
+  TOOLBOX_QUERY_PARAMETER,
+  ToolboxError,
+  type ToolboxDiscovery,
+} from "./types.js";
+import { requireSameOrigin, resolveWebUrl } from "./urls.js";
+
+interface MetaElementLike {
+  getAttribute(name: string): string | null;
+}
+
+interface DocumentLike {
+  querySelector(selector: string): MetaElementLike | null;
+}
+
+export interface ToolboxDiscoveryOptions {
+  location?: string | URL;
+  document?: DocumentLike;
+  queryParameter?: string;
+  metaName?: string;
+}
+
+function browserLocation(): string | undefined {
+  return typeof globalThis.location === "undefined"
+    ? undefined
+    : globalThis.location.href;
+}
+
+function browserDocument(): DocumentLike | undefined {
+  return typeof globalThis.document === "undefined"
+    ? undefined
+    : globalThis.document;
+}
+
+export function discoverToolboxCatalog(
+  options: ToolboxDiscoveryOptions = {},
+): ToolboxDiscovery {
+  const locationReference = options.location ?? browserLocation();
+  if (locationReference === undefined) return { status: "none" };
+
+  let location: URL;
+  try {
+    location = resolveWebUrl(locationReference);
+  } catch (error) {
+    return {
+      status: "error",
+      error:
+        error instanceof ToolboxError
+          ? error
+          : new ToolboxError("invalid-url", "The page URL is invalid", {
+              cause: error,
+            }),
+    };
+  }
+
+  const parameter = options.queryParameter ?? TOOLBOX_QUERY_PARAMETER;
+  const queryValue = location.searchParams.get(parameter);
+  const document = options.document ?? browserDocument();
+  let metaValue: string | null | undefined;
+  try {
+    const metaName = (options.metaName ?? TOOLBOX_META_NAME)
+      .replaceAll("\\", "\\\\")
+      .replaceAll('"', '\\"');
+    metaValue = document
+      ?.querySelector(`meta[name="${metaName}"]`)
+      ?.getAttribute("content");
+  } catch (error) {
+    return {
+      status: "error",
+      error: new ToolboxError("invalid-url", "Toolbox meta discovery failed", {
+        cause: error,
+      }),
+    };
+  }
+  const candidate = queryValue ?? metaValue;
+  if (candidate === null || candidate === undefined) return { status: "none" };
+  if (candidate.trim().length === 0) {
+    return {
+      status: "error",
+      error: new ToolboxError(
+        "invalid-url",
+        `The ${queryValue === null ? "meta" : "query"} toolbox URL is empty`,
+      ),
+    };
+  }
+
+  try {
+    const catalogUrl = requireSameOrigin(
+      resolveWebUrl(candidate, location),
+      location,
+      "Discovered toolbox catalog",
+    );
+    return {
+      status: "found",
+      source: queryValue === null ? "meta" : "query",
+      catalogUrl,
+    };
+  } catch (error) {
+    return {
+      status: "error",
+      error:
+        error instanceof ToolboxError
+          ? error
+          : new ToolboxError("invalid-url", "The toolbox URL is invalid", {
+              cause: error,
+            }),
+    };
+  }
+}
--- a/packages/contract/src/index.ts
+++ b/packages/contract/src/index.ts
@@ -0,0 +1,60 @@
+export {
+  TOOLBOX_META_NAME,
+  TOOLBOX_QUERY_PARAMETER,
+  TOOLBOX_SCHEMA_VERSION,
+  ToolboxError,
+  ToolboxValidationError,
+} from "./types.js";
+export type {
+  ResolvedToolboxAction,
+  ResolvedToolboxApp,
+  ResolvedToolboxCatalog,
+  ResolvedToolboxCatalogEntry,
+  ResolvedToolboxCatalogExternalEntry,
+  ResolvedToolboxCatalogManifestEntry,
+  ResolvedToolboxPrivacy,
+  ToolboxAction,
+  ToolboxAppManifest,
+  ToolboxCatalog,
+  ToolboxCatalogEntry,
+  ToolboxCatalogExternalEntry,
+  ToolboxCatalogManifestEntry,
+  ToolboxCatalogTheme,
+  ToolboxContext,
+  ToolboxContextResult,
+  ToolboxDiscovery,
+  ToolboxDiscoverySource,
+  ToolboxErrorCode,
+  ToolboxIntegration,
+  ToolboxLaunchMode,
+  ToolboxPrivacy,
+  ToolboxRequirements,
+  ToolboxSource,
+} from "./types.js";
+export {
+  createContextualLink,
+  contextualizeToolboxLink,
+  requireSameOrigin,
+  resolveToolboxApp,
+  resolveWebUrl,
+} from "./urls.js";
+export type { ContextualLinkOptions } from "./urls.js";
+export {
+  defineToolboxApp,
+  defineToolboxCatalog,
+  parseToolboxApp,
+  parseToolboxCatalog,
+} from "./parse.js";
+export { discoverToolboxCatalog } from "./discovery.js";
+export type { ToolboxDiscoveryOptions } from "./discovery.js";
+export {
+  fetchToolboxAppManifest,
+  fetchToolboxCatalog,
+  loadToolboxCatalog,
+  loadToolboxContext,
+} from "./load.js";
+export type {
+  ToolboxContextLoadOptions,
+  ToolboxFetch,
+  ToolboxLoadOptions,
+} from "./load.js";
--- a/packages/contract/src/load.ts
+++ b/packages/contract/src/load.ts
@@ -0,0 +1,245 @@
+import {
+  discoverToolboxCatalog,
+  type ToolboxDiscoveryOptions,
+} from "./discovery.js";
+import { parseToolboxApp, parseToolboxCatalog } from "./parse.js";
+import {
+  ToolboxError,
+  type ResolvedToolboxCatalog,
+  type ToolboxAppManifest,
+  type ToolboxCatalog,
+  type ToolboxContextResult,
+  type ToolboxDiscoverySource,
+} from "./types.js";
+import { requireSameOrigin, resolveToolboxApp, resolveWebUrl } from "./urls.js";
+
+export type ToolboxFetch = (
+  input: string | URL | Request,
+  init?: RequestInit,
+) => Promise<Response>;
+
+export interface ToolboxLoadOptions {
+  fetch?: ToolboxFetch;
+  signal?: AbortSignal;
+  baseUrl?: string | URL;
+  expectedOrigin?: string | URL;
+}
+
+function defaultFetch(): ToolboxFetch {
+  if (typeof globalThis.fetch !== "function") {
+    throw new ToolboxError(
+      "fetch-failed",
+      "No fetch implementation is available",
+    );
+  }
+  return globalThis.fetch.bind(globalThis);
+}
+
+function absoluteUrl(reference: string | URL, base?: string | URL): URL {
+  if (base !== undefined) return resolveWebUrl(reference, base);
+  if (typeof reference !== "string" || /^[a-z][a-z\d+.-]*:/i.test(reference)) {
+    return resolveWebUrl(reference);
+  }
+  if (typeof globalThis.location !== "undefined") {
+    return resolveWebUrl(reference, globalThis.location.href);
+  }
+  throw new ToolboxError(
+    "invalid-url",
+    `A base URL is required for relative URL: ${reference}`,
+  );
+}
+
+async function fetchJson(
+  url: URL,
+  options: ToolboxLoadOptions,
+): Promise<unknown> {
+  let response: Response;
+  try {
+    response = await (options.fetch ?? defaultFetch())(url, {
+      headers: { accept: "application/json" },
+      redirect: "error",
+      ...(options.signal === undefined ? {} : { signal: options.signal }),
+    });
+  } catch (cause) {
+    throw new ToolboxError("fetch-failed", `Could not fetch ${url.href}`, {
+      cause,
+    });
+  }
+  if (typeof response.url === "string" && response.url !== "") {
+    requireSameOrigin(
+      resolveWebUrl(response.url),
+      url,
+      `Final response for ${url.href}`,
+    );
+  }
+  if (!response.ok) {
+    throw new ToolboxError(
+      "fetch-failed",
+      `Could not fetch ${url.href}: HTTP ${response.status}`,
+    );
+  }
+  try {
+    return await response.json();
+  } catch (cause) {
+    throw new ToolboxError("fetch-failed", `${url.href} is not valid JSON`, {
+      cause,
+    });
+  }
+}
+
+export async function fetchToolboxAppManifest(
+  manifestUrl: string | URL,
+  options: ToolboxLoadOptions = {},
+): Promise<ToolboxAppManifest> {
+  const url = absoluteUrl(manifestUrl, options.baseUrl);
+  if (options.expectedOrigin !== undefined) {
+    requireSameOrigin(
+      url,
+      absoluteUrl(options.expectedOrigin),
+      "Application manifest",
+    );
+  }
+  return parseToolboxApp(await fetchJson(url, options));
+}
+
+export async function fetchToolboxCatalog(
+  catalogUrl: string | URL,
+  options: ToolboxLoadOptions = {},
+): Promise<ToolboxCatalog> {
+  const url = absoluteUrl(catalogUrl, options.baseUrl);
+  if (options.expectedOrigin !== undefined) {
+    requireSameOrigin(
+      url,
+      absoluteUrl(options.expectedOrigin),
+      "Toolbox catalog",
+    );
+  }
+  return parseToolboxCatalog(await fetchJson(url, options));
+}
+
+export async function loadToolboxCatalog(
+  catalogReference: string | URL,
+  options: ToolboxLoadOptions = {},
+): Promise<ResolvedToolboxCatalog> {
+  const catalogUrl = absoluteUrl(catalogReference, options.baseUrl);
+  const expectedOrigin =
+    options.expectedOrigin === undefined
+      ? catalogUrl
+      : absoluteUrl(options.expectedOrigin);
+  requireSameOrigin(catalogUrl, expectedOrigin, "Toolbox catalog");
+
+  const catalog = await fetchToolboxCatalog(catalogUrl, {
+    ...options,
+    expectedOrigin,
+  });
+  const apps = await Promise.all(
+    catalog.apps
+      .filter((entry) => entry.enabled)
+      .map(async (entry) => {
+        if ("entry" in entry) {
+          return {
+            kind: "external" as const,
+            enabled: entry.enabled,
+            name: entry.name,
+            entryUrl: resolveWebUrl(entry.entry, catalogUrl),
+            launch: entry.launch,
+          };
+        }
+        const manifestUrl = requireSameOrigin(
+          resolveWebUrl(entry.manifest, catalogUrl),
+          expectedOrigin,
+          "Catalog application manifest",
+        );
+        const manifest = await fetchToolboxAppManifest(manifestUrl, {
+          ...options,
+          expectedOrigin,
+        });
+        return {
+          kind: "manifest" as const,
+          enabled: entry.enabled,
+          app: resolveToolboxApp(manifest, manifestUrl, expectedOrigin),
+        };
+      }),
+  );
+  const homeUrl = requireSameOrigin(
+    resolveWebUrl(catalog.home, catalogUrl),
+    expectedOrigin,
+    "Toolbox home",
+  );
+
+  return {
+    catalog,
+    catalogUrl,
+    apps,
+    homeUrl,
+  };
+}
+
+export interface ToolboxContextLoadOptions
+  extends
+    ToolboxDiscoveryOptions,
+    Omit<ToolboxLoadOptions, "baseUrl" | "expectedOrigin"> {
+  catalogUrl?: string | URL;
+}
+
+function asToolboxError(error: unknown): ToolboxError {
+  return error instanceof ToolboxError
+    ? error
+    : new ToolboxError(
+        "fetch-failed",
+        "The toolbox context could not be loaded",
+        {
+          cause: error,
+        },
+      );
+}
+
+export async function loadToolboxContext(
+  options: ToolboxContextLoadOptions = {},
+): Promise<ToolboxContextResult> {
+  let source: ToolboxDiscoverySource;
+  let catalogUrl: URL;
+  let pageUrl: URL;
+
+  if (options.catalogUrl !== undefined) {
+    source = "explicit";
+    try {
+      pageUrl = resolveWebUrl(
+        options.location ??
+          (typeof globalThis.location === "undefined"
+            ? options.catalogUrl
+            : globalThis.location.href),
+      );
+      catalogUrl = requireSameOrigin(
+        resolveWebUrl(options.catalogUrl, pageUrl),
+        pageUrl,
+        "Toolbox catalog",
+      );
+    } catch (error) {
+      return { status: "error", error: asToolboxError(error) };
+    }
+  } else {
+    const discovery = discoverToolboxCatalog(options);
+    if (discovery.status === "none") return { status: "standalone" };
+    if (discovery.status === "error") return discovery;
+    source = discovery.source;
+    catalogUrl = discovery.catalogUrl;
+    pageUrl = resolveWebUrl(
+      options.location ??
+        (typeof globalThis.location === "undefined"
+          ? catalogUrl
+          : globalThis.location.href),
+    );
+  }
+
+  try {
+    const catalog = await loadToolboxCatalog(catalogUrl, {
+      ...(options.fetch === undefined ? {} : { fetch: options.fetch }),
+      ...(options.signal === undefined ? {} : { signal: options.signal }),
+      expectedOrigin: pageUrl,
+    });
+    return { status: "ready", context: { source, catalog } };
+  } catch (error) {
+    return { status: "error", error: asToolboxError(error) };
+  }
+}
--- a/packages/contract/src/parse.ts
+++ b/packages/contract/src/parse.ts
@@ -0,0 +1,528 @@
+import {
+  TOOLBOX_SCHEMA_VERSION,
+  ToolboxValidationError,
+  type ToolboxAction,
+  type ToolboxAppManifest,
+  type ToolboxCatalog,
+  type ToolboxCatalogEntry,
+  type ToolboxCatalogExternalEntry,
+  type ToolboxCatalogManifestEntry,
+  type ToolboxCatalogTheme,
+  type ToolboxIntegration,
+  type ToolboxLaunchMode,
+  type ToolboxPrivacy,
+  type ToolboxRequirements,
+  type ToolboxSource,
+} from "./types.js";
+
+type UnknownRecord = Record<string, unknown>;
+
+const ID_PATTERN = /^[a-z0-9]+(?:[._-][a-z0-9]+)*$/;
+const WEB_PROTOCOLS = new Set(["http:", "https:"]);
+const REFERENCE_BASE = "https://toolbox.invalid/";
+
+function recordAt(
+  value: unknown,
+  path: string,
+  issues: string[],
+): UnknownRecord {
+  if (typeof value !== "object" || value === null || Array.isArray(value)) {
+    issues.push(`${path} must be an object`);
+    return {};
+  }
+  return value as UnknownRecord;
+}
+
+function stringAt(
+  object: UnknownRecord,
+  key: string,
+  path: string,
+  issues: string[],
+  options: { optional?: boolean; allowEmpty?: boolean } = {},
+): string | undefined {
+  if (!(key in object) && options.optional) return undefined;
+  const value = object[key];
+  if (typeof value !== "string") {
+    issues.push(`${path}.${key} must be a string`);
+    return undefined;
+  }
+  if (!options.allowEmpty && value.trim().length === 0) {
+    issues.push(`${path}.${key} must not be empty`);
+    return undefined;
+  }
+  return value;
+}
+
+function booleanAt(
+  object: UnknownRecord,
+  key: string,
+  path: string,
+  issues: string[],
+  optional = false,
+): boolean | undefined {
+  if (!(key in object) && optional) return undefined;
+  const value = object[key];
+  if (typeof value !== "boolean") {
+    issues.push(`${path}.${key} must be a boolean`);
+    return undefined;
+  }
+  return value;
+}
+
+function enumAt<const T extends string>(
+  object: UnknownRecord,
+  key: string,
+  allowed: readonly T[],
+  path: string,
+  issues: string[],
+): T | undefined {
+  const value = stringAt(object, key, path, issues);
+  if (value === undefined) return undefined;
+  if (!allowed.includes(value as T)) {
+    issues.push(`${path}.${key} must be one of ${allowed.join(", ")}`);
+    return undefined;
+  }
+  return value as T;
+}
+
+function idAt(
+  object: UnknownRecord,
+  key: string,
+  path: string,
+  issues: string[],
+): string | undefined {
+  const value = stringAt(object, key, path, issues);
+  if (value !== undefined && !ID_PATTERN.test(value)) {
+    issues.push(`${path}.${key} must be a lowercase toolbox id`);
+    return undefined;
+  }
+  return value;
+}
+
+function referenceAt(
+  object: UnknownRecord,
+  key: string,
+  path: string,
+  issues: string[],
+  optional = false,
+): string | undefined {
+  const value = stringAt(object, key, path, issues, { optional });
+  if (value === undefined) return undefined;
+  if (value.includes("\\")) {
+    issues.push(`${path}.${key} must use URL path separators`);
+    return undefined;
+  }
+  try {
+    const url = new URL(value, REFERENCE_BASE);
+    if (!WEB_PROTOCOLS.has(url.protocol) || url.username || url.password) {
+      issues.push(`${path}.${key} must be an HTTP(S) URL reference`);
+      return undefined;
+    }
+  } catch {
+    issues.push(`${path}.${key} must be a valid URL reference`);
+    return undefined;
+  }
+  return value;
+}
+
+function absoluteReferenceAt(
+  object: UnknownRecord,
+  key: string,
+  path: string,
+  issues: string[],
+): string | undefined {
+  const value = referenceAt(object, key, path, issues);
+  if (value === undefined) return undefined;
+  try {
+    const url = new URL(value);
+    if (!WEB_PROTOCOLS.has(url.protocol) || url.username || url.password) {
+      throw new Error("Unsupported URL");
+    }
+  } catch {
+    issues.push(`${path}.${key} must be an absolute HTTP(S) URL`);
+    return undefined;
+  }
+  return value;
+}
+
+function schemaVersionAt(
+  object: UnknownRecord,
+  path: string,
+  issues: string[],
+): void {
+  if (object.schemaVersion !== TOOLBOX_SCHEMA_VERSION) {
+    issues.push(`${path}.schemaVersion must be ${TOOLBOX_SCHEMA_VERSION}`);
+  }
+}
+
+function stringListAt(
+  object: UnknownRecord,
+  key: string,
+  path: string,
+  issues: string[],
+): readonly string[] {
+  const value = object[key];
+  if (!Array.isArray(value)) {
+    issues.push(`${path}.${key} must be an array`);
+    return [];
+  }
+  const seen = new Set<string>();
+  return value.flatMap((item, index) => {
+    if (typeof item !== "string" || item.trim().length === 0) {
+      issues.push(`${path}.${key}[${index}] must be a non-empty string`);
+      return [];
+    }
+    if (seen.has(item)) {
+      issues.push(`${path}.${key}[${index}] must be unique`);
+      return [];
+    }
+    seen.add(item);
+    return [item];
+  });
+}
+
+function parsePrivacy(
+  value: unknown,
+  path: string,
+  issues: string[],
+): ToolboxPrivacy | undefined {
+  const object = recordAt(value, path, issues);
+  const processing = enumAt(
+    object,
+    "processing",
+    ["local", "remote", "mixed"] as const,
+    path,
+    issues,
+  );
+  const fileUploads = booleanAt(object, "fileUploads", path, issues);
+  const telemetry = booleanAt(object, "telemetry", path, issues);
+  const label = stringAt(object, "label", path, issues, { optional: true });
+  const url = referenceAt(object, "url", path, issues, true);
+  if (
+    processing === undefined ||
+    fileUploads === undefined ||
+    telemetry === undefined
+  ) {
+    return undefined;
+  }
+  return {
+    processing,
+    fileUploads,
+    telemetry,
+    ...(label === undefined ? {} : { label }),
+    ...(url === undefined ? {} : { url }),
+  };
+}
+
+function parseIntegration(
+  value: unknown,
+  path: string,
+  issues: string[],
+): ToolboxIntegration | undefined {
+  const object = recordAt(value, path, issues);
+  if (object.contextVersion !== 1) {
+    issues.push(`${path}.contextVersion must be 1`);
+  }
+  const launchModes = object.launchModes;
+  const modes: ToolboxLaunchMode[] = [];
+  if (!Array.isArray(launchModes) || launchModes.length === 0) {
+    issues.push(`${path}.launchModes must be a non-empty array`);
+  } else {
+    const seen = new Set<string>();
+    launchModes.forEach((mode, index) => {
+      if (mode !== "navigate" && mode !== "new-tab") {
+        issues.push(`${path}.launchModes[${index}] is invalid`);
+      } else if (seen.has(mode)) {
+        issues.push(`${path}.launchModes[${index}] must be unique`);
+      } else {
+        seen.add(mode);
+        modes.push(mode);
+      }
+    });
+  }
+  const embedding = enumAt(
+    object,
+    "embedding",
+    ["unsupported", "supported"] as const,
+    path,
+    issues,
+  );
+  return object.contextVersion === 1 &&
+    modes.length > 0 &&
+    embedding !== undefined
+    ? { contextVersion: 1, launchModes: modes, embedding }
+    : undefined;
+}
+
+function parseRequirements(
+  value: unknown,
+  path: string,
+  issues: string[],
+): ToolboxRequirements | undefined {
+  const object = recordAt(value, path, issues);
+  const secureContext = booleanAt(object, "secureContext", path, issues);
+  const workers = booleanAt(object, "workers", path, issues);
+  const indexedDb = booleanAt(object, "indexedDb", path, issues);
+  const crossOriginIsolated = booleanAt(
+    object,
+    "crossOriginIsolated",
+    path,
+    issues,
+  );
+  const topLevelContext = booleanAt(
+    object,
+    "topLevelContext",
+    path,
+    issues,
+    true,
+  );
+  if (
+    secureContext === undefined ||
+    workers === undefined ||
+    indexedDb === undefined ||
+    crossOriginIsolated === undefined
+  ) {
+    return undefined;
+  }
+  return {
+    secureContext,
+    workers,
+    indexedDb,
+    crossOriginIsolated,
+    ...(topLevelContext === undefined ? {} : { topLevelContext }),
+  };
+}
+
+function parseSource(
+  value: unknown,
+  path: string,
+  issues: string[],
+): ToolboxSource | undefined {
+  const object = recordAt(value, path, issues);
+  const repository = absoluteReferenceAt(object, "repository", path, issues);
+  const license = stringAt(object, "license", path, issues);
+  return repository === undefined || license === undefined
+    ? undefined
+    : { repository, license };
+}
+
+function parseActions(
+  value: unknown,
+  path: string,
+  issues: string[],
+): readonly ToolboxAction[] {
+  if (!Array.isArray(value)) {
+    issues.push(`${path} must be an array`);
+    return [];
+  }
+  const ids = new Set<string>();
+  return value.flatMap((item, index) => {
+    const itemPath = `${path}[${index}]`;
+    const object = recordAt(item, itemPath, issues);
+    const id = idAt(object, "id", itemPath, issues);
+    const label = stringAt(object, "label", itemPath, issues);
+    const url = referenceAt(object, "url", itemPath, issues);
+    if (id !== undefined) {
+      if (ids.has(id)) issues.push(`${itemPath}.id must be unique`);
+      ids.add(id);
+    }
+    return id === undefined || label === undefined || url === undefined
+      ? []
+      : [{ id, label, url }];
+  });
+}
+
+function parseAssets(
+  value: unknown,
+  path: string,
+  issues: string[],
+): readonly string[] {
+  if (!Array.isArray(value)) {
+    issues.push(`${path} must be an array`);
+    return [];
+  }
+  const seen = new Set<string>();
+  return value.flatMap((item, index) => {
+    const holder = { value: item };
+    const reference = referenceAt(holder, "value", `${path}[${index}]`, issues);
+    if (reference === undefined) return [];
+    if (seen.has(reference)) {
+      issues.push(`${path}[${index}] must be unique`);
+      return [];
+    }
+    seen.add(reference);
+    return [reference];
+  });
+}
+
+export function parseToolboxApp(value: unknown): ToolboxAppManifest {
+  const issues: string[] = [];
+  const object = recordAt(value, "$", issues);
+  schemaVersionAt(object, "$", issues);
+  const id = idAt(object, "id", "$", issues);
+  const name = stringAt(object, "name", "$", issues);
+  const version = stringAt(object, "version", "$", issues);
+  const description = stringAt(object, "description", "$", issues, {
+    allowEmpty: true,
+  });
+  const entry = referenceAt(object, "entry", "$", issues);
+  const icon = referenceAt(object, "icon", "$", issues);
+  const categories = stringListAt(object, "categories", "$", issues);
+  const tags = stringListAt(object, "tags", "$", issues);
+  const integration = parseIntegration(
+    object.integration,
+    "$.integration",
+    issues,
+  );
+  const requirements = parseRequirements(
+    object.requirements,
+    "$.requirements",
+    issues,
+  );
+  const privacy = parsePrivacy(object.privacy, "$.privacy", issues);
+  const source =
+    "source" in object
+      ? parseSource(object.source, "$.source", issues)
+      : undefined;
+  const actions =
+    "actions" in object
+      ? parseActions(object.actions, "$.actions", issues)
+      : undefined;
+  const assets =
+    "assets" in object
+      ? parseAssets(object.assets, "$.assets", issues)
+      : undefined;
+
+  if (
+    issues.length > 0 ||
+    id === undefined ||
+    name === undefined ||
+    version === undefined ||
+    description === undefined ||
+    entry === undefined ||
+    icon === undefined ||
+    integration === undefined ||
+    requirements === undefined ||
+    privacy === undefined
+  ) {
+    throw new ToolboxValidationError("invalid-app", issues);
+  }
+  return {
+    schemaVersion: TOOLBOX_SCHEMA_VERSION,
+    id,
+    name,
+    version,
+    description,
+    entry,
+    icon,
+    categories,
+    tags,
+    integration,
+    requirements,
+    privacy,
+    ...(source === undefined ? {} : { source }),
+    ...(actions === undefined ? {} : { actions }),
+    ...(assets === undefined ? {} : { assets }),
+  };
+}
+
+function parseCatalogEntry(
+  value: unknown,
+  path: string,
+  issues: string[],
+): ToolboxCatalogEntry | undefined {
+  const object = recordAt(value, path, issues);
+  const enabled = booleanAt(object, "enabled", path, issues);
+  if ("manifest" in object) {
+    const manifest = referenceAt(object, "manifest", path, issues);
+    if ("entry" in object) {
+      issues.push(`${path} cannot contain both manifest and entry`);
+    }
+    return manifest === undefined || enabled === undefined
+      ? undefined
+      : ({ manifest, enabled } satisfies ToolboxCatalogManifestEntry);
+  }
+  const name = stringAt(object, "name", path, issues);
+  const entry = referenceAt(object, "entry", path, issues);
+  const launch = enumAt(
+    object,
+    "launch",
+    ["navigate", "new-tab"] as const,
+    path,
+    issues,
+  );
+  return name === undefined ||
+    entry === undefined ||
+    launch === undefined ||
+    enabled === undefined
+    ? undefined
+    : ({ name, entry, launch, enabled } satisfies ToolboxCatalogExternalEntry);
+}
+
+function parseTheme(
+  value: unknown,
+  path: string,
+  issues: string[],
+): ToolboxCatalogTheme | undefined {
+  const object = recordAt(value, path, issues);
+  const mode = enumAt(
+    object,
+    "mode",
+    ["light", "dark", "system"] as const,
+    path,
+    issues,
+  );
+  const brand = stringAt(object, "brand", path, issues);
+  return mode === undefined || brand === undefined
+    ? undefined
+    : { mode, brand };
+}
+
+export function parseToolboxCatalog(value: unknown): ToolboxCatalog {
+  const issues: string[] = [];
+  const object = recordAt(value, "$", issues);
+  schemaVersionAt(object, "$", issues);
+  const id = idAt(object, "id", "$", issues);
+  const name = stringAt(object, "name", "$", issues);
+  const home = referenceAt(object, "home", "$", issues);
+  const theme = parseTheme(object.theme, "$.theme", issues);
+  const appsValue = object.apps;
+  let apps: readonly ToolboxCatalogEntry[] = [];
+  if (!Array.isArray(appsValue)) {
+    issues.push("$.apps must be an array");
+  } else {
+    apps = appsValue.flatMap((entry, index) => {
+      const parsed = parseCatalogEntry(entry, `$.apps[${index}]`, issues);
+      return parsed === undefined ? [] : [parsed];
+    });
+  }
+  if (
+    issues.length > 0 ||
+    id === undefined ||
+    name === undefined ||
+    home === undefined ||
+    theme === undefined
+  ) {
+    throw new ToolboxValidationError("invalid-catalog", issues);
+  }
+  return {
+    schemaVersion: TOOLBOX_SCHEMA_VERSION,
+    id,
+    name,
+    home,
+    theme,
+    apps,
+  };
+}
+
+export function defineToolboxApp<const T extends ToolboxAppManifest>(
+  app: T,
+): T {
+  return app;
+}
+
+export function defineToolboxCatalog<const T extends ToolboxCatalog>(
+  catalog: T,
+): T {
+  return catalog;
+}
--- a/packages/contract/src/types.ts
+++ b/packages/contract/src/types.ts
@@ -0,0 +1,178 @@
+export const TOOLBOX_SCHEMA_VERSION = 1 as const;
+export const TOOLBOX_QUERY_PARAMETER = "toolbox" as const;
+export const TOOLBOX_META_NAME = "toolbox" as const;
+
+export interface ToolboxAction {
+  id: string;
+  label: string;
+  url: string;
+}
+
+export interface ToolboxPrivacy {
+  processing: "local" | "remote" | "mixed";
+  fileUploads: boolean;
+  telemetry: boolean;
+  label?: string;
+  url?: string;
+}
+
+export type ToolboxLaunchMode = "navigate" | "new-tab";
+
+export interface ToolboxIntegration {
+  contextVersion: 1;
+  launchModes: readonly ToolboxLaunchMode[];
+  embedding: "unsupported" | "supported";
+}
+
+export interface ToolboxRequirements {
+  secureContext: boolean;
+  workers: boolean;
+  indexedDb: boolean;
+  crossOriginIsolated: boolean;
+  topLevelContext?: boolean;
+}
+
+export interface ToolboxSource {
+  repository: string;
+  license: string;
+}
+
+export interface ToolboxAppManifest {
+  schemaVersion: typeof TOOLBOX_SCHEMA_VERSION;
+  id: string;
+  name: string;
+  version: string;
+  description: string;
+  entry: string;
+  icon: string;
+  categories: readonly string[];
+  tags: readonly string[];
+  integration: ToolboxIntegration;
+  requirements: ToolboxRequirements;
+  privacy: ToolboxPrivacy;
+  source?: ToolboxSource;
+  actions?: readonly ToolboxAction[];
+  assets?: readonly string[];
+}
+
+export interface ToolboxCatalogManifestEntry {
+  manifest: string;
+  enabled: boolean;
+}
+
+export interface ToolboxCatalogExternalEntry {
+  name: string;
+  entry: string;
+  launch: ToolboxLaunchMode;
+  enabled: boolean;
+}
+
+export type ToolboxCatalogEntry =
+  ToolboxCatalogManifestEntry | ToolboxCatalogExternalEntry;
+
+export interface ToolboxCatalogTheme {
+  mode: "light" | "dark" | "system";
+  brand: string;
+}
+
+export interface ToolboxCatalog {
+  schemaVersion: typeof TOOLBOX_SCHEMA_VERSION;
+  id: string;
+  name: string;
+  home: string;
+  theme: ToolboxCatalogTheme;
+  apps: readonly ToolboxCatalogEntry[];
+}
+
+export interface ResolvedToolboxAction extends Omit<ToolboxAction, "url"> {
+  url: URL;
+}
+
+export interface ResolvedToolboxPrivacy extends Omit<ToolboxPrivacy, "url"> {
+  url?: URL;
+}
+
+export interface ResolvedToolboxApp {
+  manifest: ToolboxAppManifest;
+  manifestUrl: URL;
+  entryUrl: URL;
+  actions: readonly ResolvedToolboxAction[];
+  assetUrls: readonly URL[];
+  iconUrl: URL;
+  privacy: ResolvedToolboxPrivacy;
+}
+
+export interface ResolvedToolboxCatalogManifestEntry {
+  kind: "manifest";
+  enabled: boolean;
+  app: ResolvedToolboxApp;
+}
+
+export interface ResolvedToolboxCatalogExternalEntry {
+  kind: "external";
+  enabled: boolean;
+  name: string;
+  entryUrl: URL;
+  launch: ToolboxLaunchMode;
+}
+
+export type ResolvedToolboxCatalogEntry =
+  ResolvedToolboxCatalogManifestEntry | ResolvedToolboxCatalogExternalEntry;
+
+export interface ResolvedToolboxCatalog {
+  catalog: ToolboxCatalog;
+  catalogUrl: URL;
+  apps: readonly ResolvedToolboxCatalogEntry[];
+  homeUrl: URL;
+}
+
+export type ToolboxDiscoverySource = "query" | "meta" | "explicit";
+
+export interface ToolboxContext {
+  source: ToolboxDiscoverySource;
+  catalog: ResolvedToolboxCatalog;
+}
+
+export type ToolboxErrorCode =
+  | "invalid-app"
+  | "invalid-catalog"
+  | "invalid-url"
+  | "cross-origin"
+  | "fetch-failed";
+
+export class ToolboxError extends Error {
+  readonly code: ToolboxErrorCode;
+
+  constructor(code: ToolboxErrorCode, message: string, options?: ErrorOptions) {
+    super(message, options);
+    this.name = "ToolboxError";
+    this.code = code;
+  }
+}
+
+export class ToolboxValidationError extends ToolboxError {
+  readonly issues: readonly string[];
+
+  constructor(
+    code: Extract<ToolboxErrorCode, "invalid-app" | "invalid-catalog">,
+    issues: readonly string[],
+  ) {
+    super(code, `Invalid toolbox document: ${issues.join("; ")}`);
+    this.name = "ToolboxValidationError";
+    this.issues = issues;
+  }
+}
+
+export type ToolboxDiscovery =
+  | { status: "none" }
+  | {
+      status: "found";
+      source: Exclude<ToolboxDiscoverySource, "explicit">;
+      catalogUrl: URL;
+    }
+  | { status: "error"; error: ToolboxError };
+
+export type ToolboxContextResult =
+  | { status: "standalone" }
+  | { status: "ready"; context: ToolboxContext }
+  | { status: "error"; error: ToolboxError };
--- a/packages/contract/src/urls.ts
+++ b/packages/contract/src/urls.ts
@@ -0,0 +1,131 @@
+import {
+  TOOLBOX_QUERY_PARAMETER,
+  ToolboxError,
+  type ResolvedToolboxAction,
+  type ResolvedToolboxApp,
+  type ResolvedToolboxPrivacy,
+  type ToolboxAppManifest,
+} from "./types.js";
+
+const WEB_PROTOCOLS = new Set(["http:", "https:"]);
+
+export function resolveWebUrl(
+  reference: string | URL,
+  base?: string | URL,
+): URL {
+  let url: URL;
+  try {
+    url = base === undefined ? new URL(reference) : new URL(reference, base);
+  } catch (cause) {
+    throw new ToolboxError("invalid-url", `Invalid URL: ${String(reference)}`, {
+      cause,
+    });
+  }
+  if (!WEB_PROTOCOLS.has(url.protocol) || url.username || url.password) {
+    throw new ToolboxError(
+      "invalid-url",
+      `Only credential-free HTTP(S) URLs are supported: ${url.href}`,
+    );
+  }
+  return url;
+}
+
+export function requireSameOrigin(
+  url: URL,
+  expected: URL,
+  label = "Toolbox URL",
+): URL {
+  if (url.origin !== expected.origin) {
+    throw new ToolboxError(
+      "cross-origin",
+      `${label} must share the page origin (${expected.origin})`,
+    );
+  }
+  return url;
+}
+
+export function resolveToolboxApp(
+  manifest: ToolboxAppManifest,
+  manifestUrl: string | URL,
+  expectedOrigin?: string | URL,
+): ResolvedToolboxApp {
+  const resolvedManifestUrl = resolveWebUrl(manifestUrl);
+  const origin =
+    expectedOrigin === undefined
+      ? resolvedManifestUrl
+      : resolveWebUrl(expectedOrigin);
+
+  requireSameOrigin(resolvedManifestUrl, origin, "Application manifest");
+
+  const localUrl = (reference: string, label: string): URL =>
+    requireSameOrigin(
+      resolveWebUrl(reference, resolvedManifestUrl),
+      origin,
+      label,
+    );
+  const externalUrl = (reference: string): URL =>
+    resolveWebUrl(reference, resolvedManifestUrl);
+
+  const actions: readonly ResolvedToolboxAction[] = (
+    manifest.actions ?? []
+  ).map((action) => ({
+    ...action,
+    url: externalUrl(action.url),
+  }));
+  const privacy: ResolvedToolboxPrivacy = {
+    processing: manifest.privacy.processing,
+    fileUploads: manifest.privacy.fileUploads,
+    telemetry: manifest.privacy.telemetry,
+    ...(manifest.privacy.label === undefined
+      ? {}
+      : { label: manifest.privacy.label }),
+    ...(manifest.privacy.url === undefined
+      ? {}
+      : { url: externalUrl(manifest.privacy.url) }),
+  };
+
+  return {
+    manifest,
+    manifestUrl: resolvedManifestUrl,
+    entryUrl: localUrl(manifest.entry, "Application entry"),
+    actions,
+    assetUrls: (manifest.assets ?? []).map((asset) =>
+      localUrl(asset, "Application asset"),
+    ),
+    iconUrl: localUrl(manifest.icon, "Application icon"),
+    privacy,
+  };
+}
+
+export interface ContextualLinkOptions {
+  location?: string | URL;
+  parameter?: string;
+}
+
+export function contextualizeToolboxLink(
+  target: string | URL,
+  catalog: string | URL,
+  options: ContextualLinkOptions = {},
+): string {
+  const location = resolveWebUrl(
+    options.location ??
+      (typeof globalThis.location === "undefined"
+        ? "http://localhost/"
+        : globalThis.location.href),
+  );
+  const targetUrl = resolveWebUrl(target, location);
+  if (targetUrl.origin !== location.origin) return targetUrl.href;
+
+  const catalogUrl = requireSameOrigin(
+    resolveWebUrl(catalog, location),
+    location,
+    "Toolbox catalog",
+  );
+  targetUrl.searchParams.set(
+    options.parameter ?? TOOLBOX_QUERY_PARAMETER,
+    catalogUrl.href,
+  );
+  return targetUrl.href;
+}
+
+export const createContextualLink = contextualizeToolboxLink;
--- a/packages/contract/test/contract.test.ts
+++ b/packages/contract/test/contract.test.ts
@@ -0,0 +1,288 @@
+import {
+  ToolboxValidationError,
+  contextualizeToolboxLink,
+  discoverToolboxCatalog,
+  loadToolboxContext,
+  parseToolboxApp,
+  parseToolboxCatalog,
+  type ToolboxAppManifest,
+} from "../src/index.js";
+import { describe, expect, it, vi } from "vitest";
+
+const app = (
+  overrides: Record<string, unknown> = {},
+): Record<string, unknown> => ({
+  schemaVersion: 1,
+  id: "de.add-ideas.pdf-tools",
+  name: "PDF Workbench",
+  version: "1.2.3",
+  description: "Local PDF tools",
+  entry: "./index.html",
+  icon: "./icon.svg",
+  categories: ["documents", "pdf"],
+  tags: ["merge", "split"],
+  integration: {
+    contextVersion: 1,
+    launchModes: ["navigate", "new-tab"],
+    embedding: "unsupported",
+  },
+  requirements: {
+    secureContext: true,
+    workers: true,
+    indexedDb: true,
+    crossOriginIsolated: false,
+  },
+  privacy: {
+    processing: "local",
+    fileUploads: false,
+    telemetry: false,
+  },
+  source: {
+    repository: "https://git.example.test/pdf-tools",
+    license: "AGPL-3.0-only",
+  },
+  ...overrides,
+});
+
+const catalog = (
+  overrides: Record<string, unknown> = {},
+): Record<string, unknown> => ({
+  schemaVersion: 1,
+  id: "de.add-ideas.toolbox",
+  name: "Toolbox",
+  home: "./",
+  theme: { mode: "system", brand: "add·ideas" },
+  apps: [{ manifest: "./pdf/toolbox-app.json", enabled: true }],
+  ...overrides,
+});
+
+const json = (value: unknown, init: ResponseInit = {}): Response =>
+  new Response(JSON.stringify(value), {
+    status: 200,
+    headers: { "content-type": "application/json" },
+    ...init,
+  });
+
+describe("v1 runtime parsing", () => {
+  it("parses the full app contract and drops unknown optional fields", () => {
+    const parsed = parseToolboxApp(
+      app({
+        futureField: "ignored",
+        privacy: {
+          processing: "local",
+          fileUploads: false,
+          telemetry: false,
+          futurePrivacyField: true,
+        },
+      }),
+    );
+
+    expect(parsed).toMatchObject({
+      schemaVersion: 1,
+      id: "de.add-ideas.pdf-tools",
+      privacy: { processing: "local", fileUploads: false, telemetry: false },
+    });
+    expect(parsed).not.toHaveProperty("futureField");
+    expect(parsed.privacy).not.toHaveProperty("futurePrivacyField");
+  });
+
+  it("rejects unsupported versions and malformed known optional fields", () => {
+    expect(() => parseToolboxApp(app({ schemaVersion: 2 }))).toThrow(
+      ToolboxValidationError,
+    );
+    expect(() =>
+      parseToolboxApp(
+        app({
+          requirements: {
+            secureContext: true,
+            workers: true,
+            indexedDb: true,
+            crossOriginIsolated: false,
+            topLevelContext: "sometimes",
+          },
+        }),
+      ),
+    ).toThrow(/topLevelContext must be a boolean/u);
+  });
+
+  it("accepts omitted source metadata but validates it when supplied", () => {
+    const withoutSource = app();
+    delete withoutSource.source;
+    expect(parseToolboxApp(withoutSource)).not.toHaveProperty("source");
+    expect(() =>
+      parseToolboxApp(
+        app({ source: { repository: "../repository", license: "MIT" } }),
+      ),
+    ).toThrow(/absolute HTTP\(S\) URL/u);
+  });
+
+  it("parses manifest references and external inline catalog entries", () => {
+    const parsed = parseToolboxCatalog(
+      catalog({
+        futureField: 1,
+        apps: [
+          { manifest: "./pdf/toolbox-app.json", enabled: true, future: true },
+          {
+            name: "External docs",
+            entry: "https://docs.example.test/",
+            launch: "new-tab",
+            enabled: true,
+          },
+        ],
+      }),
+    );
+
+    expect(parsed.apps).toHaveLength(2);
+    expect(parsed.apps[1]).toEqual({
+      name: "External docs",
+      entry: "https://docs.example.test/",
+      launch: "new-tab",
+      enabled: true,
+    });
+    expect(parsed).not.toHaveProperty("futureField");
+  });
+});
+
+describe("same-origin discovery", () => {
+  it("prefers a same-origin query context over meta context", () => {
+    const result = discoverToolboxCatalog({
+      location: "https://tools.example.test/pdf/?toolbox=%2Fcatalog.json",
+      document: {
+        querySelector: () => ({
+          getAttribute: () => "/meta-catalog.json",
+        }),
+      },
+    });
+
+    expect(result.status).toBe("found");
+    if (result.status === "found") {
+      expect(result.source).toBe("query");
+      expect(result.catalogUrl.href).toBe(
+        "https://tools.example.test/catalog.json",
+      );
+    }
+  });
+
+  it("rejects a cross-origin query without falling through to meta", () => {
+    const result = discoverToolboxCatalog({
+      location:
+        "https://tools.example.test/pdf/?toolbox=https%3A%2F%2Fevil.test%2Fcatalog.json",
+      document: {
+        querySelector: () => ({ getAttribute: () => "/safe.json" }),
+      },
+    });
+
+    expect(result.status).toBe("error");
+    if (result.status === "error")
+      expect(result.error.code).toBe("cross-origin");
+  });
+});
+
+describe("loading and links", () => {
+  it("loads a catalog, resolves manifests and URLs, and supports external apps", async () => {
+    const fetch = vi.fn(
+      async (input: string | URL | Request, init?: RequestInit) => {
+        void init;
+        const url = new URL(input instanceof Request ? input.url : input);
+        if (url.pathname === "/catalog.json") {
+          return json(
+            catalog({
+              apps: [
+                { manifest: "./pdf/toolbox-app.json", enabled: true },
+                { manifest: "./disabled/toolbox-app.json", enabled: false },
+                {
+                  name: "Documentation",
+                  entry: "https://docs.example.test/",
+                  launch: "new-tab",
+                  enabled: true,
+                },
+              ],
+            }),
+          );
+        }
+        if (url.pathname === "/pdf/toolbox-app.json") return json(app());
+        if (url.pathname === "/disabled/toolbox-app.json") {
+          throw new Error("Disabled manifests must not be fetched");
+        }
+        return new Response("Not found", { status: 404 });
+      },
+    );
+
+    const result = await loadToolboxContext({
+      location: "https://tools.example.test/pdf/?toolbox=/catalog.json",
+      fetch,
+    });
+
+    for (const [, init] of fetch.mock.calls) {
+      expect(init).toMatchObject({ redirect: "error" });
+    }
+
+    expect(result.status).toBe("ready");
+    if (result.status === "ready") {
+      expect(result.context.catalog.homeUrl.href).toBe(
+        "https://tools.example.test/",
+      );
+      expect(result.context.catalog.apps[0]?.kind).toBe("manifest");
+      const first = result.context.catalog.apps[0];
+      if (first?.kind === "manifest") {
+        expect(first.app.entryUrl.href).toBe(
+          "https://tools.example.test/pdf/index.html",
+        );
+      }
+      expect(result.context.catalog.apps[1]).toMatchObject({
+        kind: "external",
+        launch: "new-tab",
+      });
+    }
+  });
+
+  it("returns a graceful error result for invalid JSON and fetch failure", async () => {
+    const invalid = await loadToolboxContext({
+      location: "https://tools.example.test/?toolbox=/catalog.json",
+      fetch: async () => json(catalog({ schemaVersion: 2 })),
+    });
+    expect(invalid.status).toBe("error");
+
+    const unavailable = await loadToolboxContext({
+      location: "https://tools.example.test/?toolbox=/catalog.json",
+      fetch: async () => new Response("No", { status: 503 }),
+    });
+    expect(unavailable.status).toBe("error");
+    if (unavailable.status === "error") {
+      expect(unavailable.error.code).toBe("fetch-failed");
+    }
+  });
+
+  it("rejects a fetch redirected to a cross-origin response URL", async () => {
+    const response = json(catalog());
+    Object.defineProperty(response, "url", {
+      value: "https://evil.example/toolbox.catalog.json",
+    });
+    const result = await loadToolboxContext({
+      location: "https://tools.example.test/?toolbox=/catalog.json",
+      fetch: async () => response,
+    });
+
+    expect(result.status).toBe("error");
+    if (result.status === "error")
+      expect(result.error.code).toBe("cross-origin");
+  });
+
+  it("adds context to same-origin links but leaves external links alone", () => {
+    expect(
+      new URL(
+        contextualizeToolboxLink("./other/", "/catalog.json", {
+          location: "https://tools.example.test/pdf/",
+        }),
+      ).searchParams.get("toolbox"),
+    ).toBe("https://tools.example.test/catalog.json");
+
+    expect(
+      contextualizeToolboxLink("https://docs.example.test/", "/catalog.json", {
+        location: "https://tools.example.test/pdf/",
+      }),
+    ).toBe("https://docs.example.test/");
+  });
+});
+
+export const validAppFixture = app() as unknown as ToolboxAppManifest;
--- a/packages/contract/test/schema-parity.test.ts
+++ b/packages/contract/test/schema-parity.test.ts
@@ -0,0 +1,261 @@
+// @vitest-environment node
+
+import { readFileSync } from "node:fs";
+
+import Ajv2020, { type ValidateFunction } from "ajv/dist/2020.js";
+import { describe, expect, it } from "vitest";
+
+import { parseToolboxApp, parseToolboxCatalog } from "../src/index.js";
+
+const appSchema = JSON.parse(
+  readFileSync(
+    new URL("../../../schemas/toolbox-app.v1.schema.json", import.meta.url),
+    "utf8",
+  ),
+) as object;
+const catalogSchema = JSON.parse(
+  readFileSync(
+    new URL("../../../schemas/toolbox-catalog.v1.schema.json", import.meta.url),
+    "utf8",
+  ),
+) as object;
+
+const ajv = new Ajv2020({
+  allErrors: true,
+  strict: true,
+  // `not: { required: [...] }` intentionally names the opposite union arm.
+  strictRequired: false,
+});
+const validateApp = ajv.compile(appSchema);
+const validateCatalog = ajv.compile(catalogSchema);
+
+type Parser = (value: unknown) => unknown;
+
+function runtimeAccepts(parser: Parser, value: unknown): boolean {
+  try {
+    parser(value);
+    return true;
+  } catch {
+    return false;
+  }
+}
+
+function expectParity(
+  validate: ValidateFunction,
+  parser: Parser,
+  value: unknown,
+  expected: boolean,
+): void {
+  const schemaAccepted = validate(value);
+  expect(
+    schemaAccepted,
+    ajv.errorsText(validate.errors, { separator: "\n" }),
+  ).toBe(expected);
+  expect(runtimeAccepts(parser, value)).toBe(expected);
+}
+
+const validApp = (): Record<string, unknown> => ({
+  schemaVersion: 1,
+  id: "de.add-ideas.example",
+  name: "Example",
+  version: "1.2.3",
+  description: "Example application",
+  entry: "./",
+  icon: "./icon.svg",
+  categories: ["documents"],
+  tags: ["example"],
+  integration: {
+    contextVersion: 1,
+    launchModes: ["navigate"],
+    embedding: "unsupported",
+  },
+  requirements: {
+    secureContext: false,
+    workers: false,
+    indexedDb: false,
+    crossOriginIsolated: false,
+  },
+  privacy: {
+    processing: "local",
+    fileUploads: false,
+    telemetry: false,
+  },
+  source: {
+    repository: "https://example.test/source",
+    license: "MIT",
+  },
+});
+
+const validCatalog = (): Record<string, unknown> => ({
+  schemaVersion: 1,
+  id: "de.add-ideas.toolbox",
+  name: "Example Toolbox",
+  home: "./",
+  theme: { mode: "system", brand: "Example" },
+  apps: [{ manifest: "./apps/example/toolbox-app.json", enabled: true }],
+});
+
+describe("canonical schema and runtime parser parity", () => {
+  const acceptedApps: Array<[string, () => Record<string, unknown>]> = [
+    ["the baseline app", validApp],
+    [
+      "relative references containing spaces and path @ signs",
+      () => ({
+        ...validApp(),
+        entry: " ./nested app/?mode=1#result ",
+        actions: [{ id: "docs", label: "Docs", url: "./people/@me" }],
+      }),
+    ],
+    [
+      "case-insensitive and compact absolute HTTP URLs",
+      () => ({
+        ...validApp(),
+        source: { repository: "HTTPS:example.test", license: "MIT" },
+      }),
+    ],
+  ];
+
+  it.each(acceptedApps)("accepts %s", (_label, fixture) => {
+    expectParity(validateApp, parseToolboxApp, fixture(), true);
+  });
+
+  const rejectedApps: Array<[string, () => Record<string, unknown>]> = [
+    ["a whitespace-only name", () => ({ ...validApp(), name: " \t " })],
+    [
+      "a whitespace-only list item",
+      () => ({ ...validApp(), categories: ["documents", " \n "] }),
+    ],
+    [
+      "a non-web entry scheme",
+      () => ({ ...validApp(), entry: "javascript:alert(1)" }),
+    ],
+    ["a backslash path", () => ({ ...validApp(), icon: ".\\icon.svg" })],
+    ["an empty HTTP authority", () => ({ ...validApp(), entry: "https://" })],
+    [
+      "a credential-bearing privacy URL",
+      () => ({
+        ...validApp(),
+        privacy: {
+          processing: "local",
+          fileUploads: false,
+          telemetry: false,
+          url: "https://user:secret@example.test/privacy",
+        },
+      }),
+    ],
+    [
+      "a relative source repository",
+      () => ({
+        ...validApp(),
+        source: { repository: "../source", license: "MIT" },
+      }),
+    ],
+    [
+      "a compact credential-bearing source repository",
+      () => ({
+        ...validApp(),
+        source: { repository: "https:user@example.test", license: "MIT" },
+      }),
+    ],
+    [
+      "a whitespace-only action label",
+      () => ({
+        ...validApp(),
+        actions: [{ id: "docs", label: "  ", url: "./docs" }],
+      }),
+    ],
+  ];
+
+  it.each(rejectedApps)("rejects %s", (_label, fixture) => {
+    expectParity(validateApp, parseToolboxApp, fixture(), false);
+  });
+
+  const acceptedCatalogs: Array<[string, () => Record<string, unknown>]> = [
+    ["the baseline catalog", validCatalog],
+    [
+      "an uppercase HTTPS manifest URL",
+      () => ({
+        ...validCatalog(),
+        apps: [
+          {
+            manifest: "HTTPS://example.test/apps/example/toolbox-app.json",
+            enabled: true,
+          },
+        ],
+      }),
+    ],
+  ];
+
+  it.each(acceptedCatalogs)("accepts %s", (_label, fixture) => {
+    expectParity(validateCatalog, parseToolboxCatalog, fixture(), true);
+  });
+
+  const rejectedCatalogs: Array<[string, () => Record<string, unknown>]> = [
+    [
+      "a whitespace-only catalog name",
+      () => ({ ...validCatalog(), name: " " }),
+    ],
+    [
+      "a whitespace-only brand",
+      () => ({
+        ...validCatalog(),
+        theme: { mode: "system", brand: "\t" },
+      }),
+    ],
+    [
+      "a non-web home URL",
+      () => ({ ...validCatalog(), home: "file:///tmp/toolbox" }),
+    ],
+    [
+      "a backslash manifest path",
+      () => ({
+        ...validCatalog(),
+        apps: [{ manifest: ".\\apps\\toolbox-app.json", enabled: true }],
+      }),
+    ],
+    [
+      "a credential-bearing manifest URL",
+      () => ({
+        ...validCatalog(),
+        apps: [
+          {
+            manifest: "https://user:secret@example.test/toolbox-app.json",
+            enabled: true,
+          },
+        ],
+      }),
+    ],
+    [
+      "a non-web external entry",
+      () => ({
+        ...validCatalog(),
+        apps: [
+          {
+            name: "External",
+            entry: "data:text/html,hello",
+            launch: "new-tab",
+            enabled: true,
+          },
+        ],
+      }),
+    ],
+    [
+      "a whitespace-only external name",
+      () => ({
+        ...validCatalog(),
+        apps: [
+          {
+            name: " ",
+            entry: "https://example.test/",
+            launch: "new-tab",
+            enabled: true,
+          },
+        ],
+      }),
+    ],
+  ];
+
+  it.each(rejectedCatalogs)("rejects %s", (_label, fixture) => {
+    expectParity(validateCatalog, parseToolboxCatalog, fixture(), false);
+  });
+});
--- a/packages/contract/tsconfig.build.json
+++ b/packages/contract/tsconfig.build.json
@@ -0,0 +1,7 @@
+{
+  "extends": "./tsconfig.json",
+  "compilerOptions": {
+    "noEmit": false
+  },
+  "exclude": ["test"]
+}
--- a/packages/contract/tsconfig.json
+++ b/packages/contract/tsconfig.json
@@ -0,0 +1,8 @@
+{
+  "extends": "../../tsconfig.base.json",
+  "compilerOptions": {
+    "rootDir": "src",
+    "outDir": "dist"
+  },
+  "include": ["src"]
+}
--- a/packages/shell-react/LICENSE
+++ b/packages/shell-react/LICENSE
@@ -0,0 +1,192 @@
+                                 Apache License
+                           Version 2.0, January 2004
+                        http://www.apache.org/licenses/
+
+   TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION
+
+   1. Definitions.
+
+      "License" shall mean the terms and conditions for use, reproduction,
+      and distribution as defined by Sections 1 through 9 of this document.
+
+      "Licensor" shall mean the copyright owner or entity authorized by
+      the copyright owner that is granting the License.
+
+      "Legal Entity" shall mean the union of the acting entity and all
+      other entities that control, are controlled by, or are under common
+      control with that entity. For the purposes of this definition,
+      "control" means (i) the power, direct or indirect, to cause the
+      direction or management of such entity, whether by contract or
+      otherwise, or (ii) ownership of fifty percent (50%) or more of the
+      outstanding shares, or (iii) beneficial ownership of such entity.
+
+      "You" (or "Your") shall mean an individual or Legal Entity
+      exercising permissions granted by this License.
+
+      "Source" form shall mean the preferred form for making modifications,
+      including but not limited to software source code, documentation
+      source, and configuration files.
+
+      "Object" form shall mean any form resulting from mechanical
+      transformation or translation of a Source form, including but
+      not limited to compiled object code, generated documentation,
+      and conversions to other media types.
+
+      "Work" shall mean the work of authorship, whether in Source or
+      Object form, made available under the License, as indicated by a
+      copyright notice that is included in or attached to the work
+      (an example is provided in the Appendix below).
+
+      "Derivative Works" shall mean any work, whether in Source or Object
+      form, that is based on (or derived from) the Work and for which the
+      editorial revisions, annotations, elaborations, or other modifications
+      represent, as a whole, an original work of authorship. For the purposes
+      of this License, Derivative Works shall not include works that remain
+      separable from, or merely link (or bind by name) to the interfaces of,
+      the Work and Derivative Works thereof.
+
+      "Contribution" shall mean any work of authorship, including
+      the original version of the Work and any modifications or additions
+      to that Work or Derivative Works thereof, that is intentionally
+      submitted to Licensor for inclusion in the Work by the copyright owner
+      or by an individual or Legal Entity authorized to submit on behalf of
+      the copyright owner. For the purposes of this definition, "submitted"
+      means any form of electronic, verbal, or written communication sent
+      to the Licensor or its representatives, including but not limited to
+      communication on electronic mailing lists, source code control systems,
+      and issue tracking systems that are managed by, or on behalf of, the
+      Licensor for the purpose of discussing and improving the Work, but
+      excluding communication that is conspicuously marked or otherwise
+      designated in writing by the copyright owner as "Not a Contribution."
+
+      "Contributor" shall mean Licensor and any individual or Legal Entity
+      on behalf of whom a Contribution has been received by Licensor and
+      subsequently incorporated within the Work.
+
+   2. Grant of Copyright License. Subject to the terms and conditions of
+      this License, each Contributor hereby grants to You a perpetual,
+      worldwide, non-exclusive, no-charge, royalty-free, irrevocable
+      copyright license to reproduce, prepare Derivative Works of,
+      publicly display, publicly perform, sublicense, and distribute the
+      Work and such Derivative Works in Source or Object form.
+
+   3. Grant of Patent License. Subject to the terms and conditions of
+      this License, each Contributor hereby grants to You a perpetual,
+      worldwide, non-exclusive, no-charge, royalty-free, irrevocable
+      (except as stated in this section) patent license to make, have made,
+      use, offer to sell, sell, import, and otherwise transfer the Work,
+      where such license applies only to those patent claims licensable
+      by such Contributor that are necessarily infringed by their
+      Contribution(s) alone or by combination of their Contribution(s)
+      with the Work to which such Contribution(s) was submitted. If You
+      institute patent litigation against any entity (including a
+      cross-claim or counterclaim in a lawsuit) alleging that the Work
+      or a Contribution incorporated within the Work constitutes direct
+      or contributory patent infringement, then any patent licenses
+      granted to You under this License for that Work shall terminate
+      as of the date such litigation is filed.
+
+   4. Redistribution. You may reproduce and distribute copies of the
+      Work or Derivative Works thereof in any medium, with or without
+      modifications, and in Source or Object form, provided that You
+      meet the following conditions:
+
+      (a) You must give any other recipients of the Work or
+          Derivative Works a copy of this License; and
+
+      (b) You must cause any modified files to carry prominent notices
+          stating that You changed the files; and
+
+      (c) You must retain, in the Source form of any Derivative Works
+          that You distribute, all copyright, patent, trademark, and
+          attribution notices from the Source form of the Work,
+          excluding those notices that do not pertain to any part of
+          the Derivative Works; and
+
+      (d) If the Work includes a "NOTICE" text file as part of its
+          distribution, then any Derivative Works that You distribute must
+          include a readable copy of the attribution notices contained
+          within such NOTICE file, excluding those notices that do not
+          pertain to any part of the Derivative Works, in at least one
+          of the following places: within a NOTICE text file distributed
+          as part of the Derivative Works; within the Source form or
+          documentation, if provided along with the Derivative Works; or,
+          within a display generated by the Derivative Works, if and
+          wherever such third-party notices normally appear. The contents
+          of the NOTICE file are for informational purposes only and
+          do not modify the License. You may add Your own attribution
+          notices within Derivative Works that You distribute, alongside
+          or as an addendum to the NOTICE text from the Work, provided
+          that such additional attribution notices cannot be construed
+          as modifying the License.
+
+      You may add Your own copyright statement to Your modifications and
+      may provide additional or different license terms and conditions
+      for use, reproduction, or distribution of Your modifications, or
+      for any such Derivative Works as a whole, provided Your use,
+      reproduction, and distribution of the Work otherwise complies with
+      the conditions stated in this License.
+
+   5. Submission of Contributions. Unless You explicitly state otherwise,
+      any Contribution intentionally submitted for inclusion in the Work
+      by You to the Licensor shall be under the terms and conditions of
+      this License, without any additional terms or conditions.
+      Notwithstanding the above, nothing herein shall supersede or modify
+      the terms of any separate license agreement you may have executed
+      with Licensor regarding such Contributions.
+
+   6. Trademarks. This License does not grant permission to use the trade
+      names, trademarks, service marks, or product names of the Licensor,
+      except as required for reasonable and customary use in describing the
+      origin of the Work and reproducing the content of the NOTICE file.
+
+   7. Disclaimer of Warranty. Unless required by applicable law or
+      agreed to in writing, Licensor provides the Work (and each
+      Contributor provides its Contributions) on an "AS IS" BASIS,
+      WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
+      implied, including, without limitation, any warranties or conditions
+      of TITLE, NON-INFRINGEMENT, MERCHANTABILITY, or FITNESS FOR A
+      PARTICULAR PURPOSE. You are solely responsible for determining the
+      appropriateness of using or redistributing the Work and assume any
+      risks associated with Your exercise of permissions under this License.
+
+   8. Limitation of Liability. In no event and under no legal theory,
+      whether in tort (including negligence), contract, or otherwise,
+      unless required by applicable law (such as deliberate and grossly
+      negligent acts) or agreed to in writing, shall any Contributor be
+      liable to You for damages, including any direct, indirect, special,
+      incidental, or consequential damages of any character arising as a
+      result of this License or out of the use or inability to use the
+      Work (including but not limited to damages for loss of goodwill,
+      work stoppage, computer failure or malfunction, or any and all
+      other commercial damages or losses), even if such Contributor
+      has been advised of the possibility of such damages.
+
+   9. Accepting Warranty or Additional Liability. While redistributing
+      the Work or Derivative Works thereof, You may choose to offer,
+      and charge a fee for, acceptance of support, warranty, indemnity,
+      or other liability obligations and/or rights consistent with this
+      License. However, in accepting such obligations, You may act only
+      on Your own behalf and on Your sole responsibility, not on behalf
+      of any other Contributor, and only if You agree to indemnify,
+      defend, and hold each Contributor harmless for any liability
+      incurred by, or claims asserted against, such Contributor by reason
+      of your accepting any such warranty or additional liability.
+
+   END OF TERMS AND CONDITIONS
+
+   APPENDIX: How to apply the Apache License to your work.
+
+      Copyright 2026 ADD Ideas
+
+      Licensed under the Apache License, Version 2.0 (the "License");
+      you may not use this file except in compliance with the License.
+      You may obtain a copy of the License at
+
+          http://www.apache.org/licenses/LICENSE-2.0
+
+      Unless required by applicable law or agreed to in writing, software
+      distributed under the License is distributed on an "AS IS" BASIS,
+      WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+      See the License for the specific language governing permissions and
+      limitations under the License.
--- a/packages/shell-react/README.md
+++ b/packages/shell-react/README.md
@@ -0,0 +1,15 @@
+# @add-ideas/toolbox-shell-react
+
+```tsx
+import { AppShell } from "@add-ideas/toolbox-shell-react";
+import "@add-ideas/toolbox-shell-react/styles.css";
+
+<AppShell app={manifest} appActions={<a href="/help">Help</a>}>
+  <App />
+</AppShell>;
+```
+
+`AppShell` discovers `?toolbox=...` or `<meta name="toolbox">`, but continues in
+standalone mode if context is absent, unavailable, cross-origin, or invalid. Its
+app switcher is exposed as the accessible navigation landmark
+`Toolbox applications` and all destinations use ordinary document navigation.
--- a/packages/shell-react/package.json
+++ b/packages/shell-react/package.json
@@ -0,0 +1,53 @@
+{
+  "name": "@add-ideas/toolbox-shell-react",
+  "version": "0.1.0",
+  "description": "A lightweight React application shell for toolbox-compatible browser applications.",
+  "license": "Apache-2.0",
+  "repository": {
+    "type": "git",
+    "url": "git+https://git.add-ideas.de/zemion/toolbox-sdk.git",
+    "directory": "packages/shell-react"
+  },
+  "homepage": "https://git.add-ideas.de/zemion/toolbox-sdk",
+  "keywords": [
+    "toolbox",
+    "react",
+    "application-shell",
+    "typescript"
+  ],
+  "type": "module",
+  "sideEffects": [
+    "**/*.css"
+  ],
+  "files": [
+    "dist",
+    "README.md",
+    "LICENSE"
+  ],
+  "exports": {
+    ".": {
+      "types": "./dist/index.d.ts",
+      "import": "./dist/index.js"
+    },
+    "./styles.css": "./dist/styles.css",
+    "./package.json": "./package.json"
+  },
+  "types": "./dist/index.d.ts",
+  "peerDependencies": {
+    "react": ">=18 <20",
+    "react-dom": ">=18 <20"
+  },
+  "dependencies": {
+    "@add-ideas/toolbox-contract": "0.1.0"
+  },
+  "scripts": {
+    "build": "tsc -p tsconfig.build.json && node -e \"const fs=require('node:fs');fs.copyFileSync('src/styles.css','dist/styles.css');fs.copyFileSync('../../LICENSE','LICENSE')\"",
+    "clean": "node -e \"require('node:fs').rmSync('dist', { recursive: true, force: true })\"",
+    "prepack": "npm run build",
+    "typecheck": "tsc -p tsconfig.json --noEmit"
+  },
+  "publishConfig": {
+    "access": "public",
+    "registry": "https://git.add-ideas.de/api/packages/zemion/npm/"
+  }
+}
--- a/packages/shell-react/src/AppShell.tsx
+++ b/packages/shell-react/src/AppShell.tsx
@@ -0,0 +1,231 @@
+import {
+  contextualizeToolboxLink,
+  loadToolboxContext,
+  resolveWebUrl,
+  type ToolboxAppManifest,
+  type ToolboxContext,
+  type ToolboxContextLoadOptions,
+  type ToolboxError,
+} from "@add-ideas/toolbox-contract";
+import { useEffect, useMemo, useRef, useState, type ReactNode } from "react";
+
+export interface AppShellProps {
+  app: ToolboxAppManifest;
+  children: ReactNode;
+  appActions?: ReactNode;
+  className?: string;
+  manifestUrl?: string | URL;
+  contextOptions?: Omit<ToolboxContextLoadOptions, "signal">;
+  onContextError?: (error: ToolboxError) => void;
+}
+
+function currentHref(): string {
+  return typeof globalThis.location === "undefined"
+    ? "http://localhost/"
+    : globalThis.location.href;
+}
+
+function safeHref(reference: string, base: string | URL): string | undefined {
+  try {
+    return resolveWebUrl(reference, base).href;
+  } catch {
+    return undefined;
+  }
+}
+
+function privacyText(app: ToolboxAppManifest): string {
+  if (app.privacy.label) return app.privacy.label;
+  const processing =
+    app.privacy.processing === "local"
+      ? "Local processing"
+      : app.privacy.processing === "remote"
+        ? "Remote processing"
+        : "Local and remote processing";
+  const details = [
+    app.privacy.fileUploads ? "uploads files" : "no file uploads",
+    app.privacy.telemetry ? "uses telemetry" : "no telemetry",
+  ];
+  return `${processing} · ${details.join(" · ")}`;
+}
+
+export function AppShell({
+  app,
+  children,
+  appActions,
+  className,
+  manifestUrl,
+  contextOptions,
+  onContextError,
+}: AppShellProps) {
+  const [context, setContext] = useState<ToolboxContext | null>(null);
+  const [contextState, setContextState] = useState<"standalone" | "connected">(
+    "standalone",
+  );
+  const errorHandler = useRef(onContextError);
+
+  useEffect(() => {
+    errorHandler.current = onContextError;
+  }, [onContextError]);
+
+  const contextCatalog = contextOptions?.catalogUrl;
+  const contextDocument = contextOptions?.document;
+  const contextFetch = contextOptions?.fetch;
+  const contextLocation = contextOptions?.location;
+  const contextMetaName = contextOptions?.metaName;
+  const contextQueryParameter = contextOptions?.queryParameter;
+
+  useEffect(() => {
+    const controller = new AbortController();
+    void loadToolboxContext({
+      ...(contextCatalog === undefined ? {} : { catalogUrl: contextCatalog }),
+      ...(contextDocument === undefined ? {} : { document: contextDocument }),
+      ...(contextFetch === undefined ? {} : { fetch: contextFetch }),
+      ...(contextLocation === undefined ? {} : { location: contextLocation }),
+      ...(contextMetaName === undefined ? {} : { metaName: contextMetaName }),
+      ...(contextQueryParameter === undefined
+        ? {}
+        : { queryParameter: contextQueryParameter }),
+      signal: controller.signal,
+    }).then((result) => {
+      if (controller.signal.aborted) return;
+      if (result.status === "ready") {
+        setContext(result.context);
+        setContextState("connected");
+      } else {
+        setContext(null);
+        setContextState("standalone");
+        if (result.status === "error") errorHandler.current?.(result.error);
+      }
+    });
+    return () => {
+      controller.abort();
+    };
+  }, [
+    contextCatalog,
+    contextDocument,
+    contextFetch,
+    contextLocation,
+    contextMetaName,
+    contextQueryParameter,
+  ]);
+
+  const pageUrl = contextLocation ?? currentHref();
+  const appManifestUrl = useMemo(
+    () =>
+      manifestUrl ??
+      safeHref("toolbox-app.json", pageUrl) ??
+      "http://localhost/toolbox-app.json",
+    [manifestUrl, pageUrl],
+  );
+  const privacyHref = app.privacy.url
+    ? safeHref(app.privacy.url, appManifestUrl)
+    : undefined;
+  const enabledApps =
+    context?.catalog.apps.filter((entry) => entry.enabled) ?? [];
+  const theme = context?.catalog.catalog.theme.mode ?? "system";
+  const rootClassName = ["toolbox-shell", className].filter(Boolean).join(" ");
+
+  return (
+    <div
+      className={rootClassName}
+      data-toolbox-context={contextState}
+      data-toolbox-theme={theme}
+    >
+      <header className="toolbox-shell__header">
+        <div className="toolbox-shell__bar">
+          {context ? (
+            <a
+              className="toolbox-shell__home"
+              href={context.catalog.homeUrl.href}
+            >
+              {context.catalog.catalog.theme.brand}
+            </a>
+          ) : null}
+
+          <div className="toolbox-shell__identity">
+            <img
+              className="toolbox-shell__icon"
+              src={safeHref(app.icon, appManifestUrl)}
+              alt=""
+              width="32"
+              height="32"
+            />
+            <div>
+              <h1 className="toolbox-shell__name">{app.name}</h1>
+              <span className="toolbox-shell__description">
+                {app.description}
+              </span>
+            </div>
+          </div>
+
+          <div className="toolbox-shell__actions">
+            {app.actions?.map((action) => {
+              const href = safeHref(action.url, appManifestUrl);
+              return href ? (
+                <a key={action.id} href={href}>
+                  {action.label}
+                </a>
+              ) : null;
+            })}
+            {appActions}
+          </div>
+
+          <div className="toolbox-shell__meta">
+            <span aria-label={`Version ${app.version}`}>v{app.version}</span>
+            {privacyHref ? (
+              <a href={privacyHref}>{privacyText(app)}</a>
+            ) : (
+              <span>{privacyText(app)}</span>
+            )}
+          </div>
+
+          {context && enabledApps.length > 0 ? (
+            <details className="toolbox-shell__switcher">
+              <summary>Apps</summary>
+              <nav aria-label="Toolbox applications">
+                <ul>
+                  {enabledApps.map((entry) => {
+                    if (entry.kind === "external") {
+                      return (
+                        <li
+                          key={`external:${entry.name}:${entry.entryUrl.href}`}
+                        >
+                          <a
+                            href={entry.entryUrl.href}
+                            {...(entry.launch === "new-tab"
+                              ? { target: "_blank", rel: "noreferrer" }
+                              : {})}
+                          >
+                            {entry.name}
+                          </a>
+                        </li>
+                      );
+                    }
+                    const manifest = entry.app.manifest;
+                    return (
+                      <li key={manifest.id}>
+                        <a
+                          href={contextualizeToolboxLink(
+                            entry.app.entryUrl,
+                            context.catalog.catalogUrl,
+                            { location: pageUrl },
+                          )}
+                          aria-current={
+                            manifest.id === app.id ? "page" : undefined
+                          }
+                        >
+                          {manifest.name}
+                        </a>
+                      </li>
+                    );
+                  })}
+                </ul>
+              </nav>
+            </details>
+          ) : null}
+        </div>
+      </header>
+      <main className="toolbox-shell__main">{children}</main>
+    </div>
+  );
+}
--- a/packages/shell-react/src/index.ts
+++ b/packages/shell-react/src/index.ts
@@ -0,0 +1,2 @@
+export { AppShell } from "./AppShell.js";
+export type { AppShellProps } from "./AppShell.js";
--- a/packages/shell-react/src/styles.css
+++ b/packages/shell-react/src/styles.css
@@ -0,0 +1,202 @@
+:root {
+  --toolbox-font:
+    Inter, ui-sans-serif, system-ui, -apple-system, BlinkMacSystemFont,
+    "Segoe UI", sans-serif;
+  --toolbox-background: #f5f7fa;
+  --toolbox-surface: #ffffff;
+  --toolbox-text: #172033;
+  --toolbox-muted: #657086;
+  --toolbox-border: #dce2ea;
+  --toolbox-accent: #3156d3;
+  --toolbox-accent-contrast: #ffffff;
+  --toolbox-radius: 0.65rem;
+  --toolbox-shadow: 0 1px 2px rgb(18 28 45 / 8%);
+}
+
+[data-toolbox-theme="dark"] {
+  --toolbox-background: #111722;
+  --toolbox-surface: #192130;
+  --toolbox-text: #edf1f7;
+  --toolbox-muted: #aab4c5;
+  --toolbox-border: #303b4d;
+  --toolbox-accent: #9db2ff;
+  --toolbox-accent-contrast: #111722;
+}
+
+@media (prefers-color-scheme: dark) {
+  [data-toolbox-theme="system"] {
+    --toolbox-background: #111722;
+    --toolbox-surface: #192130;
+    --toolbox-text: #edf1f7;
+    --toolbox-muted: #aab4c5;
+    --toolbox-border: #303b4d;
+    --toolbox-accent: #9db2ff;
+    --toolbox-accent-contrast: #111722;
+  }
+}
+
+.toolbox-shell {
+  min-height: 100vh;
+  color: var(--toolbox-text);
+  background: var(--toolbox-background);
+  font-family: var(--toolbox-font);
+}
+
+.toolbox-shell *,
+.toolbox-shell *::before,
+.toolbox-shell *::after {
+  box-sizing: border-box;
+}
+
+.toolbox-shell__header {
+  position: relative;
+  z-index: 10;
+  border-bottom: 1px solid var(--toolbox-border);
+  background: var(--toolbox-surface);
+  box-shadow: var(--toolbox-shadow);
+}
+
+.toolbox-shell__bar {
+  display: flex;
+  min-height: 4.25rem;
+  align-items: center;
+  gap: 1rem;
+  max-width: 90rem;
+  margin: 0 auto;
+  padding: 0.75rem 1rem;
+}
+
+.toolbox-shell a {
+  color: var(--toolbox-accent);
+  text-decoration: none;
+}
+
+.toolbox-shell a:hover {
+  text-decoration: underline;
+}
+
+.toolbox-shell__home {
+  flex: none;
+  font-weight: 700;
+}
+
+.toolbox-shell__identity {
+  display: flex;
+  min-width: 12rem;
+  align-items: center;
+  gap: 0.65rem;
+}
+
+.toolbox-shell__identity > div {
+  display: grid;
+  gap: 0.1rem;
+}
+
+.toolbox-shell__icon {
+  flex: none;
+  border-radius: 0.35rem;
+}
+
+.toolbox-shell__name {
+  margin: 0;
+  font-size: 1rem;
+  line-height: 1.2;
+}
+
+.toolbox-shell__description {
+  color: var(--toolbox-muted);
+  font-size: 0.8rem;
+  line-height: 1.25;
+}
+
+.toolbox-shell__actions {
+  display: flex;
+  align-items: center;
+  gap: 0.75rem;
+  margin-left: auto;
+}
+
+.toolbox-shell__meta {
+  display: grid;
+  flex: none;
+  gap: 0.15rem;
+  color: var(--toolbox-muted);
+  font-size: 0.75rem;
+  text-align: right;
+}
+
+.toolbox-shell__switcher {
+  position: relative;
+  flex: none;
+}
+
+.toolbox-shell__switcher summary {
+  padding: 0.45rem 0.7rem;
+  border: 1px solid var(--toolbox-border);
+  border-radius: var(--toolbox-radius);
+  cursor: pointer;
+  font-weight: 600;
+  list-style: none;
+}
+
+.toolbox-shell__switcher summary::-webkit-details-marker {
+  display: none;
+}
+
+.toolbox-shell__switcher nav {
+  position: absolute;
+  top: calc(100% + 0.5rem);
+  right: 0;
+  width: max-content;
+  min-width: 12rem;
+  padding: 0.4rem;
+  border: 1px solid var(--toolbox-border);
+  border-radius: var(--toolbox-radius);
+  background: var(--toolbox-surface);
+  box-shadow: 0 0.75rem 2rem rgb(18 28 45 / 14%);
+}
+
+.toolbox-shell__switcher ul {
+  display: grid;
+  gap: 0.15rem;
+  margin: 0;
+  padding: 0;
+  list-style: none;
+}
+
+.toolbox-shell__switcher a {
+  display: block;
+  padding: 0.45rem 0.6rem;
+  border-radius: 0.4rem;
+}
+
+.toolbox-shell__switcher a[aria-current="page"] {
+  color: var(--toolbox-accent-contrast);
+  background: var(--toolbox-accent);
+}
+
+.toolbox-shell__main {
+  width: min(100%, 90rem);
+  margin: 0 auto;
+  padding: 1rem;
+}
+
+@media (max-width: 52rem) {
+  .toolbox-shell__bar {
+    flex-wrap: wrap;
+  }
+
+  .toolbox-shell__identity {
+    flex: 1;
+  }
+
+  .toolbox-shell__actions {
+    order: 3;
+    width: 100%;
+    margin-left: 0;
+  }
+
+  .toolbox-shell__meta {
+    display: none;
+  }
+}
--- a/packages/shell-react/test/AppShell.test.tsx
+++ b/packages/shell-react/test/AppShell.test.tsx
@@ -0,0 +1,202 @@
+import { render, screen, waitFor } from "@testing-library/react";
+import type { ToolboxAppManifest } from "@add-ideas/toolbox-contract";
+import { describe, expect, it, vi } from "vitest";
+
+import { AppShell } from "../src/index.js";
+
+const currentApp: ToolboxAppManifest = {
+  schemaVersion: 1,
+  id: "de.add-ideas.pdf-tools",
+  name: "PDF Workbench",
+  version: "1.2.3",
+  description: "Local PDF tools",
+  entry: "./index.html",
+  icon: "./icon.svg",
+  categories: ["documents", "pdf"],
+  tags: ["merge"],
+  integration: {
+    contextVersion: 1,
+    launchModes: ["navigate", "new-tab"],
+    embedding: "unsupported",
+  },
+  requirements: {
+    secureContext: true,
+    workers: true,
+    indexedDb: true,
+    crossOriginIsolated: false,
+  },
+  privacy: {
+    processing: "local",
+    fileUploads: false,
+    telemetry: false,
+  },
+  source: {
+    repository: "https://git.example.test/pdf-tools",
+    license: "AGPL-3.0-only",
+  },
+};
+
+const otherApp: ToolboxAppManifest = {
+  ...currentApp,
+  id: "de.add-ideas.xslt-tools",
+  name: "XSLT Workbench",
+  entry: "./index.html",
+  source: {
+    repository: "https://git.example.test/xslt-tools",
+    license: "AGPL-3.0-only",
+  },
+};
+
+const catalog = {
+  schemaVersion: 1,
+  id: "de.add-ideas.toolbox",
+  name: "Toolbox",
+  home: "./",
+  theme: { mode: "system", brand: "add·ideas" },
+  apps: [
+    { manifest: "./pdf/toolbox-app.json", enabled: true },
+    { manifest: "./xslt/toolbox-app.json", enabled: true },
+  ],
+};
+
+const json = (value: unknown, status = 200): Response =>
+  new Response(JSON.stringify(value), {
+    status,
+    headers: { "content-type": "application/json" },
+  });
+
+function catalogFetch() {
+  return vi.fn(async (input: string | URL | Request) => {
+    const url = new URL(input instanceof Request ? input.url : input);
+    if (url.pathname === "/toolbox.catalog.json") return json(catalog);
+    if (url.pathname === "/pdf/toolbox-app.json") return json(currentApp);
+    if (url.pathname === "/xslt/toolbox-app.json") return json(otherApp);
+    return json({}, 404);
+  });
+}
+
+describe("AppShell", () => {
+  it("renders identity, privacy, version, actions, and content standalone", async () => {
+    const fetch = vi.fn();
+    render(
+      <AppShell
+        app={currentApp}
+        appActions={<a href="/help">Help</a>}
+        contextOptions={{
+          location: "https://tools.example.test/pdf/",
+          fetch,
+        }}
+      >
+        <p>Application content</p>
+      </AppShell>,
+    );
+
+    expect(
+      screen.getByRole("heading", { level: 1, name: "PDF Workbench" }),
+    ).toBeInTheDocument();
+    expect(screen.getByLabelText("Version 1.2.3")).toBeInTheDocument();
+    expect(screen.getByText(/Local processing/u)).toBeInTheDocument();
+    expect(screen.getByRole("link", { name: "Help" })).toHaveAttribute(
+      "href",
+      "/help",
+    );
+    expect(screen.getByText("Application content")).toBeInTheDocument();
+    await waitFor(() => expect(fetch).not.toHaveBeenCalled());
+    expect(
+      document.querySelector("[data-toolbox-context='standalone']"),
+    ).toBeInTheDocument();
+    expect(
+      screen.queryByRole("navigation", { name: "Toolbox applications" }),
+    ).not.toBeInTheDocument();
+  });
+
+  it("loads same-origin context and creates full-page contextual switch links", async () => {
+    const fetch = catalogFetch();
+    render(
+      <AppShell
+        app={currentApp}
+        manifestUrl="https://tools.example.test/pdf/toolbox-app.json"
+        contextOptions={{
+          location:
+            "https://tools.example.test/pdf/?toolbox=/toolbox.catalog.json",
+          fetch,
+        }}
+      >
+        PDF
+      </AppShell>,
+    );
+
+    const navigation = await screen.findByRole("navigation", {
+      name: "Toolbox applications",
+    });
+    expect(navigation).toBeInTheDocument();
+    const current = screen.getByRole("link", { name: "PDF Workbench" });
+    expect(current).toHaveAttribute("aria-current", "page");
+    const other = screen.getByRole("link", { name: "XSLT Workbench" });
+    const destination = new URL(other.getAttribute("href") as string);
+    expect(destination.pathname).toBe("/xslt/index.html");
+    expect(destination.searchParams.get("toolbox")).toBe(
+      "https://tools.example.test/toolbox.catalog.json",
+    );
+    expect(screen.getByRole("link", { name: "add·ideas" })).toHaveAttribute(
+      "href",
+      "https://tools.example.test/",
+    );
+    expect(
+      document.querySelector("[data-toolbox-context='connected']"),
+    ).toBeInTheDocument();
+  });
+
+  it("rejects cross-origin context and remains standalone", async () => {
+    const fetch = vi.fn();
+    const onContextError = vi.fn();
+    render(
+      <AppShell
+        app={currentApp}
+        contextOptions={{
+          location:
+            "https://tools.example.test/pdf/?toolbox=https://evil.example/catalog.json",
+          fetch,
+        }}
+        onContextError={onContextError}
+      >
+        PDF
+      </AppShell>,
+    );
+
+    await waitFor(() => expect(onContextError).toHaveBeenCalledOnce());
+    expect(onContextError.mock.calls[0]?.[0]).toMatchObject({
+      code: "cross-origin",
+    });
+    expect(fetch).not.toHaveBeenCalled();
+    expect(
+      screen.queryByRole("navigation", { name: "Toolbox applications" }),
+    ).not.toBeInTheDocument();
+  });
+
+  it.each([
+    ["invalid catalog", async () => json({ schemaVersion: 2 })],
+    ["fetch failure", async () => json({}, 503)],
+  ])("survives %s in standalone mode", async (_label, fetchImplementation) => {
+    const onContextError = vi.fn();
+    render(
+      <AppShell
+        app={currentApp}
+        contextOptions={{
+          location:
+            "https://tools.example.test/pdf/?toolbox=/toolbox.catalog.json",
+          fetch: fetchImplementation,
+        }}
+        onContextError={onContextError}
+      >
+        Still usable
+      </AppShell>,
+    );
+
+    await waitFor(() => expect(onContextError).toHaveBeenCalledOnce());
+    expect(screen.getByText("Still usable")).toBeInTheDocument();
+    expect(
+      document.querySelector("[data-toolbox-context='standalone']"),
+    ).toBeInTheDocument();
+  });
+});
--- a/packages/shell-react/tsconfig.build.json
+++ b/packages/shell-react/tsconfig.build.json
@@ -0,0 +1,9 @@
+{
+  "extends": "../../tsconfig.base.json",
+  "compilerOptions": {
+    "jsx": "react-jsx",
+    "rootDir": "src",
+    "outDir": "dist"
+  },
+  "include": ["src"]
+}
--- a/packages/shell-react/tsconfig.json
+++ b/packages/shell-react/tsconfig.json
@@ -0,0 +1,11 @@
+{
+  "extends": "../../tsconfig.base.json",
+  "compilerOptions": {
+    "jsx": "react-jsx",
+    "noEmit": true,
+    "paths": {
+      "@add-ideas/toolbox-contract": ["../contract/src/index.ts"]
+    }
+  },
+  "include": ["src"]
+}
--- a/packages/testkit/LICENSE
+++ b/packages/testkit/LICENSE
@@ -0,0 +1,192 @@
+                                 Apache License
+                           Version 2.0, January 2004
+                        http://www.apache.org/licenses/
+
+   TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION
+
+   1. Definitions.
+
+      "License" shall mean the terms and conditions for use, reproduction,
+      and distribution as defined by Sections 1 through 9 of this document.
+
+      "Licensor" shall mean the copyright owner or entity authorized by
+      the copyright owner that is granting the License.
+
+      "Legal Entity" shall mean the union of the acting entity and all
+      other entities that control, are controlled by, or are under common
+      control with that entity. For the purposes of this definition,
+      "control" means (i) the power, direct or indirect, to cause the
+      direction or management of such entity, whether by contract or
+      otherwise, or (ii) ownership of fifty percent (50%) or more of the
+      outstanding shares, or (iii) beneficial ownership of such entity.
+
+      "You" (or "Your") shall mean an individual or Legal Entity
+      exercising permissions granted by this License.
+
+      "Source" form shall mean the preferred form for making modifications,
+      including but not limited to software source code, documentation
+      source, and configuration files.
+
+      "Object" form shall mean any form resulting from mechanical
+      transformation or translation of a Source form, including but
+      not limited to compiled object code, generated documentation,
+      and conversions to other media types.
+
+      "Work" shall mean the work of authorship, whether in Source or
+      Object form, made available under the License, as indicated by a
+      copyright notice that is included in or attached to the work
+      (an example is provided in the Appendix below).
+
+      "Derivative Works" shall mean any work, whether in Source or Object
+      form, that is based on (or derived from) the Work and for which the
+      editorial revisions, annotations, elaborations, or other modifications
+      represent, as a whole, an original work of authorship. For the purposes
+      of this License, Derivative Works shall not include works that remain
+      separable from, or merely link (or bind by name) to the interfaces of,
+      the Work and Derivative Works thereof.
+
+      "Contribution" shall mean any work of authorship, including
+      the original version of the Work and any modifications or additions
+      to that Work or Derivative Works thereof, that is intentionally
+      submitted to Licensor for inclusion in the Work by the copyright owner
+      or by an individual or Legal Entity authorized to submit on behalf of
+      the copyright owner. For the purposes of this definition, "submitted"
+      means any form of electronic, verbal, or written communication sent
+      to the Licensor or its representatives, including but not limited to
+      communication on electronic mailing lists, source code control systems,
+      and issue tracking systems that are managed by, or on behalf of, the
+      Licensor for the purpose of discussing and improving the Work, but
+      excluding communication that is conspicuously marked or otherwise
+      designated in writing by the copyright owner as "Not a Contribution."
+
+      "Contributor" shall mean Licensor and any individual or Legal Entity
+      on behalf of whom a Contribution has been received by Licensor and
+      subsequently incorporated within the Work.
+
+   2. Grant of Copyright License. Subject to the terms and conditions of
+      this License, each Contributor hereby grants to You a perpetual,
+      worldwide, non-exclusive, no-charge, royalty-free, irrevocable
+      copyright license to reproduce, prepare Derivative Works of,
+      publicly display, publicly perform, sublicense, and distribute the
+      Work and such Derivative Works in Source or Object form.
+
+   3. Grant of Patent License. Subject to the terms and conditions of
+      this License, each Contributor hereby grants to You a perpetual,
+      worldwide, non-exclusive, no-charge, royalty-free, irrevocable
+      (except as stated in this section) patent license to make, have made,
+      use, offer to sell, sell, import, and otherwise transfer the Work,
+      where such license applies only to those patent claims licensable
+      by such Contributor that are necessarily infringed by their
+      Contribution(s) alone or by combination of their Contribution(s)
+      with the Work to which such Contribution(s) was submitted. If You
+      institute patent litigation against any entity (including a
+      cross-claim or counterclaim in a lawsuit) alleging that the Work
+      or a Contribution incorporated within the Work constitutes direct
+      or contributory patent infringement, then any patent licenses
+      granted to You under this License for that Work shall terminate
+      as of the date such litigation is filed.
+
+   4. Redistribution. You may reproduce and distribute copies of the
+      Work or Derivative Works thereof in any medium, with or without
+      modifications, and in Source or Object form, provided that You
+      meet the following conditions:
+
+      (a) You must give any other recipients of the Work or
+          Derivative Works a copy of this License; and
+
+      (b) You must cause any modified files to carry prominent notices
+          stating that You changed the files; and
+
+      (c) You must retain, in the Source form of any Derivative Works
+          that You distribute, all copyright, patent, trademark, and
+          attribution notices from the Source form of the Work,
+          excluding those notices that do not pertain to any part of
+          the Derivative Works; and
+
+      (d) If the Work includes a "NOTICE" text file as part of its
+          distribution, then any Derivative Works that You distribute must
+          include a readable copy of the attribution notices contained
+          within such NOTICE file, excluding those notices that do not
+          pertain to any part of the Derivative Works, in at least one
+          of the following places: within a NOTICE text file distributed
+          as part of the Derivative Works; within the Source form or
+          documentation, if provided along with the Derivative Works; or,
+          within a display generated by the Derivative Works, if and
+          wherever such third-party notices normally appear. The contents
+          of the NOTICE file are for informational purposes only and
+          do not modify the License. You may add Your own attribution
+          notices within Derivative Works that You distribute, alongside
+          or as an addendum to the NOTICE text from the Work, provided
+          that such additional attribution notices cannot be construed
+          as modifying the License.
+
+      You may add Your own copyright statement to Your modifications and
+      may provide additional or different license terms and conditions
+      for use, reproduction, or distribution of Your modifications, or
+      for any such Derivative Works as a whole, provided Your use,
+      reproduction, and distribution of the Work otherwise complies with
+      the conditions stated in this License.
+
+   5. Submission of Contributions. Unless You explicitly state otherwise,
+      any Contribution intentionally submitted for inclusion in the Work
+      by You to the Licensor shall be under the terms and conditions of
+      this License, without any additional terms or conditions.
+      Notwithstanding the above, nothing herein shall supersede or modify
+      the terms of any separate license agreement you may have executed
+      with Licensor regarding such Contributions.
+
+   6. Trademarks. This License does not grant permission to use the trade
+      names, trademarks, service marks, or product names of the Licensor,
+      except as required for reasonable and customary use in describing the
+      origin of the Work and reproducing the content of the NOTICE file.
+
+   7. Disclaimer of Warranty. Unless required by applicable law or
+      agreed to in writing, Licensor provides the Work (and each
+      Contributor provides its Contributions) on an "AS IS" BASIS,
+      WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
+      implied, including, without limitation, any warranties or conditions
+      of TITLE, NON-INFRINGEMENT, MERCHANTABILITY, or FITNESS FOR A
+      PARTICULAR PURPOSE. You are solely responsible for determining the
+      appropriateness of using or redistributing the Work and assume any
+      risks associated with Your exercise of permissions under this License.
+
+   8. Limitation of Liability. In no event and under no legal theory,
+      whether in tort (including negligence), contract, or otherwise,
+      unless required by applicable law (such as deliberate and grossly
+      negligent acts) or agreed to in writing, shall any Contributor be
+      liable to You for damages, including any direct, indirect, special,
+      incidental, or consequential damages of any character arising as a
+      result of this License or out of the use or inability to use the
+      Work (including but not limited to damages for loss of goodwill,
+      work stoppage, computer failure or malfunction, or any and all
+      other commercial damages or losses), even if such Contributor
+      has been advised of the possibility of such damages.
+
+   9. Accepting Warranty or Additional Liability. While redistributing
+      the Work or Derivative Works thereof, You may choose to offer,
+      and charge a fee for, acceptance of support, warranty, indemnity,
+      or other liability obligations and/or rights consistent with this
+      License. However, in accepting such obligations, You may act only
+      on Your own behalf and on Your sole responsibility, not on behalf
+      of any other Contributor, and only if You agree to indemnify,
+      defend, and hold each Contributor harmless for any liability
+      incurred by, or claims asserted against, such Contributor by reason
+      of your accepting any such warranty or additional liability.
+
+   END OF TERMS AND CONDITIONS
+
+   APPENDIX: How to apply the Apache License to your work.
+
+      Copyright 2026 ADD Ideas
+
+      Licensed under the Apache License, Version 2.0 (the "License");
+      you may not use this file except in compliance with the License.
+      You may obtain a copy of the License at
+
+          http://www.apache.org/licenses/LICENSE-2.0
+
+      Unless required by applicable law or agreed to in writing, software
+      distributed under the License is distributed on an "AS IS" BASIS,
+      WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+      See the License for the specific language governing permissions and
+      limitations under the License.
--- a/packages/testkit/README.md
+++ b/packages/testkit/README.md
@@ -0,0 +1,17 @@
+# @add-ideas/toolbox-testkit
+
+Validate and smoke-check a built toolbox application:
+
+```sh
+toolbox-check dist
+```
+
+The checker validates `toolbox-app.json`, its id and SemVer version, verifies
+the entry, icon, and declared assets, rejects unsafe local paths, serves the
+build under a deep nested prefix, and fetches it both standalone and with
+`?toolbox=/toolbox.catalog.json`. It also fetches local scripts, stylesheets,
+images, icons, linked web manifests, and their icons from the entry HTML, so
+root-absolute references fail the nested-deployment check. It does not launch a
+browser.
+
+The same behavior is available programmatically as `checkToolboxDist()`.
--- a/packages/testkit/package.json
+++ b/packages/testkit/package.json
@@ -0,0 +1,52 @@
+{
+  "name": "@add-ideas/toolbox-testkit",
+  "version": "0.1.0",
+  "description": "Manifest, asset, and nested-deployment smoke checks for built toolbox applications.",
+  "license": "Apache-2.0",
+  "repository": {
+    "type": "git",
+    "url": "git+https://git.add-ideas.de/zemion/toolbox-sdk.git",
+    "directory": "packages/testkit"
+  },
+  "homepage": "https://git.add-ideas.de/zemion/toolbox-sdk",
+  "keywords": [
+    "toolbox",
+    "manifest",
+    "smoke-test",
+    "cli"
+  ],
+  "type": "module",
+  "sideEffects": false,
+  "engines": {
+    "node": ">=20"
+  },
+  "files": [
+    "dist",
+    "README.md",
+    "LICENSE"
+  ],
+  "bin": {
+    "toolbox-check": "./dist/cli.js"
+  },
+  "exports": {
+    ".": {
+      "types": "./dist/index.d.ts",
+      "import": "./dist/index.js"
+    },
+    "./package.json": "./package.json"
+  },
+  "types": "./dist/index.d.ts",
+  "dependencies": {
+    "@add-ideas/toolbox-contract": "0.1.0"
+  },
+  "scripts": {
+    "build": "tsc -p tsconfig.build.json && node -e \"const fs=require('node:fs');fs.chmodSync('dist/cli.js',0o755);fs.copyFileSync('../../LICENSE','LICENSE')\"",
+    "clean": "node -e \"require('node:fs').rmSync('dist', { recursive: true, force: true })\"",
+    "prepack": "npm run build",
+    "typecheck": "tsc -p tsconfig.json --noEmit"
+  },
+  "publishConfig": {
+    "access": "public",
+    "registry": "https://git.add-ideas.de/api/packages/zemion/npm/"
+  }
+}
--- a/packages/testkit/src/check.ts
+++ b/packages/testkit/src/check.ts
@@ -0,0 +1,482 @@
+import {
+  loadToolboxContext,
+  parseToolboxApp,
+  type ToolboxAppManifest,
+} from "@add-ideas/toolbox-contract";
+import { createReadStream } from "node:fs";
+import { lstat, readFile, realpath, stat } from "node:fs/promises";
+import { createServer, type Server } from "node:http";
+import { extname, relative, resolve, sep } from "node:path";
+
+const DEEP_PREFIX = "/__toolbox-check__/deep/nested/app/";
+const CATALOG_PATH = "/toolbox.catalog.json";
+const SEMVER_PATTERN =
+  /^(?:0|[1-9]\d*)\.(?:0|[1-9]\d*)\.(?:0|[1-9]\d*)(?:-[0-9A-Za-z-]+(?:\.[0-9A-Za-z-]+)*)?(?:\+[0-9A-Za-z-]+(?:\.[0-9A-Za-z-]+)*)?$/;
+
+export class ToolboxCheckError extends Error {
+  constructor(message: string, options?: ErrorOptions) {
+    super(message, options);
+    this.name = "ToolboxCheckError";
+  }
+}
+
+export interface ToolboxCheckOptions {
+  manifestName?: string;
+}
+
+export interface ToolboxCheckReport {
+  root: string;
+  manifestPath: string;
+  app: ToolboxAppManifest;
+  checkedFiles: readonly string[];
+  smoke: {
+    standaloneUrl: string;
+    contextualUrl: string;
+    fetchedUrls: readonly string[];
+  };
+}
+
+interface CheckedReference {
+  reference: string;
+  path: string;
+}
+
+function decodedReference(reference: string, label: string): string {
+  let decoded = reference;
+  try {
+    for (let count = 0; count < 3; count += 1) {
+      const next = decodeURIComponent(decoded);
+      if (next === decoded) break;
+      decoded = next;
+    }
+  } catch (cause) {
+    throw new ToolboxCheckError(`${label} contains invalid URL encoding`, {
+      cause,
+    });
+  }
+  return decoded;
+}
+
+function localReference(
+  root: string,
+  reference: string,
+  label: string,
+): CheckedReference {
+  const decoded = decodedReference(reference, label);
+  const pathPart = decoded.split(/[?#]/u, 1)[0] ?? "";
+  if (
+    pathPart.startsWith("/") ||
+    pathPart.includes("\\") ||
+    /^[a-z][a-z\d+.-]*:/iu.test(pathPart) ||
+    pathPart.split("/").includes("..") ||
+    pathPart.includes("\0")
+  ) {
+    throw new ToolboxCheckError(`${label} uses an unsafe path: ${reference}`);
+  }
+
+  let filePath = resolve(root, pathPart || ".");
+  if (pathPart.endsWith("/") || pathPart === "." || pathPart === "./") {
+    filePath = resolve(filePath, "index.html");
+  }
+  const fromRoot = relative(root, filePath);
+  if (fromRoot === ".." || fromRoot.startsWith(`..${sep}`)) {
+    throw new ToolboxCheckError(`${label} escapes the distribution directory`);
+  }
+  return { reference, path: filePath };
+}
+
+async function assertRegularContainedFile(
+  root: string,
+  item: CheckedReference,
+  label: string,
+): Promise<string> {
+  try {
+    await lstat(item.path);
+  } catch (cause) {
+    throw new ToolboxCheckError(`${label} does not exist: ${item.reference}`, {
+      cause,
+    });
+  }
+  const [realRoot, realFile] = await Promise.all([
+    realpath(root),
+    realpath(item.path),
+  ]);
+  const fromRealRoot = relative(realRoot, realFile);
+  if (fromRealRoot === ".." || fromRealRoot.startsWith(`..${sep}`)) {
+    throw new ToolboxCheckError(`${label} resolves outside the distribution`);
+  }
+  const info = await stat(realFile);
+  if (!info.isFile()) {
+    throw new ToolboxCheckError(`${label} is not a file: ${item.reference}`);
+  }
+  return item.path;
+}
+
+function contentType(path: string): string {
+  switch (extname(path).toLowerCase()) {
+    case ".html":
+      return "text/html; charset=utf-8";
+    case ".json":
+      return "application/json; charset=utf-8";
+    case ".css":
+      return "text/css; charset=utf-8";
+    case ".js":
+    case ".mjs":
+      return "text/javascript; charset=utf-8";
+    case ".svg":
+      return "image/svg+xml";
+    case ".png":
+      return "image/png";
+    default:
+      return "application/octet-stream";
+  }
+}
+
+function encodedPath(path: string): string {
+  return path.split("/").map(encodeURIComponent).join("/");
+}
+
+function catalogDocument(manifestName: string): object {
+  return {
+    schemaVersion: 1,
+    id: "de.add-ideas.toolbox-check",
+    name: "Toolbox check",
+    home: "/",
+    theme: { mode: "system", brand: "Toolbox check" },
+    apps: [
+      {
+        manifest: `${DEEP_PREFIX}${encodedPath(manifestName)}`,
+        enabled: true,
+      },
+    ],
+  };
+}
+
+function staticServer(root: string, manifestName: string): Server {
+  return createServer((request, response) => {
+    void (async () => {
+      const requestUrl = new URL(request.url ?? "/", "http://localhost");
+      if (requestUrl.pathname === CATALOG_PATH) {
+        response.writeHead(200, {
+          "content-type": "application/json; charset=utf-8",
+        });
+        response.end(JSON.stringify(catalogDocument(manifestName)));
+        return;
+      }
+      if (!requestUrl.pathname.startsWith(DEEP_PREFIX)) {
+        response.writeHead(404).end("Not found");
+        return;
+      }
+      let relativePath: string;
+      try {
+        relativePath = decodeURIComponent(
+          requestUrl.pathname.slice(DEEP_PREFIX.length),
+        );
+      } catch {
+        response.writeHead(400).end("Bad path");
+        return;
+      }
+      const checked = localReference(
+        root,
+        relativePath || "./",
+        "Request path",
+      );
+      try {
+        await assertRegularContainedFile(root, checked, "Requested file");
+      } catch {
+        response.writeHead(404).end("Not found");
+        return;
+      }
+      response.writeHead(200, { "content-type": contentType(checked.path) });
+      createReadStream(checked.path).pipe(response);
+    })().catch(() => {
+      if (!response.headersSent) response.writeHead(500);
+      response.end("Server error");
+    });
+  });
+}
+
+async function listen(server: Server): Promise<number> {
+  await new Promise<void>((resolvePromise, reject) => {
+    server.once("error", reject);
+    server.listen(0, "127.0.0.1", () => resolvePromise());
+  });
+  const address = server.address();
+  if (address === null || typeof address === "string") {
+    throw new ToolboxCheckError("Could not determine smoke-test server port");
+  }
+  return address.port;
+}
+
+async function close(server: Server): Promise<void> {
+  await new Promise<void>((resolvePromise, reject) => {
+    server.close((error) => (error ? reject(error) : resolvePromise()));
+  });
+}
+
+async function requireOk(url: URL, label: string): Promise<Response> {
+  const response = await fetch(url);
+  if (!response.ok) {
+    throw new ToolboxCheckError(`${label} returned HTTP ${response.status}`);
+  }
+  return response;
+}
+
+interface HtmlResource {
+  kind: "icon" | "image" | "manifest" | "script" | "stylesheet";
+  reference: string;
+}
+
+function attributes(source: string): Map<string, string> {
+  const result = new Map<string, string>();
+  const pattern = /([:\w-]+)\s*=\s*(?:"([^"]*)"|'([^']*)'|([^\s"'=<>`]+))/gu;
+  for (const match of source.matchAll(pattern)) {
+    const name = match[1]?.toLowerCase();
+    const value = match[2] ?? match[3] ?? match[4];
+    if (name !== undefined && value !== undefined) result.set(name, value);
+  }
+  return result;
+}
+
+function htmlResources(html: string): readonly HtmlResource[] {
+  const resources: HtmlResource[] = [];
+  const tagPattern = /<(script|link|img)\b([^>]*)>/giu;
+  for (const match of html.matchAll(tagPattern)) {
+    const tag = match[1]?.toLowerCase();
+    const values = attributes(match[2] ?? "");
+    if (tag === "script") {
+      const reference = values.get("src");
+      if (reference) resources.push({ kind: "script", reference });
+    } else if (tag === "img") {
+      const reference = values.get("src");
+      if (reference) resources.push({ kind: "image", reference });
+    } else if (tag === "link") {
+      const reference = values.get("href");
+      const relationships = new Set(
+        (values.get("rel") ?? "").toLowerCase().split(/\s+/u).filter(Boolean),
+      );
+      if (!reference) continue;
+      if (relationships.has("manifest")) {
+        resources.push({ kind: "manifest", reference });
+      } else if (relationships.has("stylesheet")) {
+        resources.push({ kind: "stylesheet", reference });
+      } else if (
+        relationships.has("icon") ||
+        relationships.has("apple-touch-icon")
+      ) {
+        resources.push({ kind: "icon", reference });
+      } else if (
+        relationships.has("modulepreload") ||
+        relationships.has("preload")
+      ) {
+        resources.push({ kind: "script", reference });
+      }
+    }
+  }
+  return resources;
+}
+
+function nestedLocalUrl(
+  reference: string,
+  base: URL,
+  label: string,
+): URL | undefined {
+  let url: URL;
+  try {
+    url = new URL(reference, base);
+  } catch (cause) {
+    throw new ToolboxCheckError(`${label} has an invalid URL: ${reference}`, {
+      cause,
+    });
+  }
+  if (url.protocol !== "http:" && url.protocol !== "https:") return undefined;
+  if (url.origin !== base.origin) return undefined;
+  if (!url.pathname.startsWith(DEEP_PREFIX)) {
+    throw new ToolboxCheckError(
+      `${label} is not relocatable under the nested prefix: ${reference}`,
+    );
+  }
+  return url;
+}
+
+async function inspectWebManifest(
+  response: Response,
+  manifestUrl: URL,
+): Promise<readonly string[]> {
+  let document: unknown;
+  try {
+    document = await response.json();
+  } catch (cause) {
+    throw new ToolboxCheckError("Linked web manifest is not valid JSON", {
+      cause,
+    });
+  }
+  if (typeof document !== "object" || document === null) return [];
+  const icons = (document as { icons?: unknown }).icons;
+  if (icons === undefined) return [];
+  if (!Array.isArray(icons)) {
+    throw new ToolboxCheckError("Linked web manifest icons must be an array");
+  }
+  const fetched: string[] = [];
+  for (const [index, icon] of icons.entries()) {
+    if (typeof icon !== "object" || icon === null) {
+      throw new ToolboxCheckError(
+        `Web manifest icon ${index} must be an object`,
+      );
+    }
+    const source = (icon as { src?: unknown }).src;
+    if (typeof source !== "string" || source.length === 0) {
+      throw new ToolboxCheckError(`Web manifest icon ${index} needs a src`);
+    }
+    const iconUrl = nestedLocalUrl(source, manifestUrl, "Web manifest icon");
+    if (iconUrl !== undefined) {
+      await requireOk(iconUrl, "Web manifest icon");
+      fetched.push(iconUrl.href);
+    }
+  }
+  return fetched;
+}
+
+async function inspectEntryHtml(
+  html: string,
+  entryUrl: URL,
+): Promise<readonly string[]> {
+  const fetched: string[] = [];
+  for (const resource of htmlResources(html)) {
+    const label = `HTML ${resource.kind}`;
+    const url = nestedLocalUrl(resource.reference, entryUrl, label);
+    if (url === undefined) continue;
+    const response = await requireOk(url, label);
+    fetched.push(url.href);
+    if (resource.kind === "manifest") {
+      fetched.push(...(await inspectWebManifest(response, url)));
+    }
+  }
+  return fetched;
+}
+
+async function smokeCheck(
+  root: string,
+  manifest: ToolboxAppManifest,
+  manifestName: string,
+): Promise<ToolboxCheckReport["smoke"]> {
+  const server = staticServer(root, manifestName);
+  const port = await listen(server);
+  try {
+    const appBase = new URL(DEEP_PREFIX, `http://127.0.0.1:${port}/`);
+    const standaloneUrl = new URL(manifest.entry, appBase);
+    const standaloneResponse = await requireOk(
+      standaloneUrl,
+      "Standalone entry",
+    );
+    const fetchedUrls = await inspectEntryHtml(
+      await standaloneResponse.text(),
+      standaloneUrl,
+    );
+    const standalone = await loadToolboxContext({ location: standaloneUrl });
+    if (standalone.status !== "standalone") {
+      throw new ToolboxCheckError(
+        "The standalone smoke URL discovered a toolbox",
+      );
+    }
+
+    const contextualUrl = new URL(standaloneUrl);
+    contextualUrl.searchParams.set("toolbox", CATALOG_PATH);
+    await requireOk(contextualUrl, "Contextual entry");
+    const contextual = await loadToolboxContext({ location: contextualUrl });
+    if (contextual.status !== "ready") {
+      const reason =
+        contextual.status === "error" ? `: ${contextual.error.message}` : "";
+      throw new ToolboxCheckError(
+        `Toolbox context smoke check failed${reason}`,
+      );
+    }
+    const loaded = contextual.context.catalog.apps.find(
+      (entry) => entry.kind === "manifest",
+    );
+    if (loaded?.kind !== "manifest" || loaded.app.manifest.id !== manifest.id) {
+      throw new ToolboxCheckError(
+        "Smoke catalog did not resolve the built app",
+      );
+    }
+    return {
+      standaloneUrl: standaloneUrl.href,
+      contextualUrl: contextualUrl.href,
+      fetchedUrls,
+    };
+  } finally {
+    await close(server);
+  }
+}
+
+export async function checkToolboxDist(
+  dist: string,
+  options: ToolboxCheckOptions = {},
+): Promise<ToolboxCheckReport> {
+  const root = resolve(dist);
+  let rootInfo;
+  try {
+    rootInfo = await stat(root);
+  } catch (cause) {
+    throw new ToolboxCheckError(
+      `Distribution directory does not exist: ${root}`,
+      {
+        cause,
+      },
+    );
+  }
+  if (!rootInfo.isDirectory()) {
+    throw new ToolboxCheckError(
+      `Distribution path is not a directory: ${root}`,
+    );
+  }
+
+  const manifestName = options.manifestName ?? "toolbox-app.json";
+  const manifestReference = localReference(root, manifestName, "Manifest");
+  const manifestPath = await assertRegularContainedFile(
+    root,
+    manifestReference,
+    "Manifest",
+  );
+  let document: unknown;
+  try {
+    document = JSON.parse(await readFile(manifestPath, "utf8"));
+  } catch (cause) {
+    throw new ToolboxCheckError(`Manifest is not valid JSON: ${manifestPath}`, {
+      cause,
+    });
+  }
+  let app: ToolboxAppManifest;
+  try {
+    app = parseToolboxApp(document);
+  } catch (cause) {
+    throw new ToolboxCheckError("Manifest does not satisfy toolbox app v1", {
+      cause,
+    });
+  }
+  if (!SEMVER_PATTERN.test(app.version)) {
+    throw new ToolboxCheckError(
+      `Manifest version is not SemVer: ${app.version}`,
+    );
+  }
+
+  const references: Array<[string, string]> = [
+    [app.entry, "Application entry"],
+    [app.icon, "Application icon"],
+    ...(app.assets ?? []).map((asset): [string, string] => [
+      asset,
+      "Application asset",
+    ]),
+  ];
+  const checkedFiles = await Promise.all(
+    references.map(([reference, label]) =>
+      assertRegularContainedFile(
+        root,
+        localReference(root, reference, label),
+        label,
+      ),
+    ),
+  );
+  const smoke = await smokeCheck(root, app, manifestName);
+  return { root, manifestPath, app, checkedFiles, smoke };
+}
--- a/packages/testkit/src/cli.ts
+++ b/packages/testkit/src/cli.ts
@@ -0,0 +1,28 @@
+#!/usr/bin/env node
+
+import { checkToolboxDist } from "./check.js";
+
+function usage(): void {
+  console.log("Usage: toolbox-check <dist>");
+}
+
+const arguments_ = process.argv.slice(2);
+if (arguments_.includes("--help") || arguments_.includes("-h")) {
+  usage();
+} else if (arguments_.length !== 1) {
+  usage();
+  process.exitCode = 2;
+} else {
+  checkToolboxDist(arguments_[0] as string)
+    .then((report) => {
+      console.log(
+        `toolbox-check: ${report.app.id}@${report.app.version} passed (${report.checkedFiles.length} files, standalone + contextual smoke checks)`,
+      );
+    })
+    .catch((error: unknown) => {
+      console.error(
+        `toolbox-check: ${error instanceof Error ? error.message : String(error)}`,
+      );
+      process.exitCode = 1;
+    });
+}
--- a/packages/testkit/src/index.ts
+++ b/packages/testkit/src/index.ts
@@ -0,0 +1,2 @@
+export { checkToolboxDist, ToolboxCheckError } from "./check.js";
+export type { ToolboxCheckOptions, ToolboxCheckReport } from "./check.js";
--- a/packages/testkit/test/check.test.ts
+++ b/packages/testkit/test/check.test.ts
@@ -0,0 +1,118 @@
+// @vitest-environment node
+
+import { mkdtemp, rm, writeFile } from "node:fs/promises";
+import { tmpdir } from "node:os";
+import { join } from "node:path";
+
+import { afterEach, describe, expect, it } from "vitest";
+
+import { checkToolboxDist } from "../src/index.js";
+
+const temporaryDirectories: string[] = [];
+
+const manifest = (overrides: Record<string, unknown> = {}) => ({
+  schemaVersion: 1,
+  id: "de.add-ideas.example",
+  name: "Example",
+  version: "1.2.3",
+  description: "Example app",
+  entry: "./",
+  icon: "./icon.svg",
+  categories: ["example"],
+  tags: ["test"],
+  integration: {
+    contextVersion: 1,
+    launchModes: ["navigate"],
+    embedding: "unsupported",
+  },
+  requirements: {
+    secureContext: false,
+    workers: false,
+    indexedDb: false,
+    crossOriginIsolated: false,
+  },
+  privacy: {
+    processing: "local",
+    fileUploads: false,
+    telemetry: false,
+  },
+  source: {
+    repository: "https://git.example.test/example",
+    license: "MIT",
+  },
+  assets: ["./app.js"],
+  ...overrides,
+});
+
+async function fixture(document = manifest()): Promise<string> {
+  const root = await mkdtemp(join(tmpdir(), "toolbox-check-"));
+  temporaryDirectories.push(root);
+  await Promise.all([
+    writeFile(join(root, "toolbox-app.json"), JSON.stringify(document)),
+    writeFile(
+      join(root, "index.html"),
+      '<!doctype html><link rel="manifest" href="./site.webmanifest"><link rel="icon" href="./icon.svg"><link rel="stylesheet" href="./style.css"><img src="./image.png" alt=""><script type="module" src="./app.js"></script><title>Example</title>',
+    ),
+    writeFile(
+      join(root, "icon.svg"),
+      '<svg xmlns="http://www.w3.org/2000/svg"/>',
+    ),
+    writeFile(join(root, "app.js"), "console.log('ok')"),
+    writeFile(join(root, "style.css"), "body { color: black; }"),
+    writeFile(join(root, "image.png"), "not-a-real-png"),
+    writeFile(
+      join(root, "site.webmanifest"),
+      JSON.stringify({ icons: [{ src: "./icon.svg" }] }),
+    ),
+  ]);
+  return root;
+}
+
+afterEach(async () => {
+  await Promise.all(
+    temporaryDirectories
+      .splice(0)
+      .map((path) => rm(path, { recursive: true, force: true })),
+  );
+});
+
+describe("toolbox-check", () => {
+  it("validates files and smoke-fetches nested standalone and context URLs", async () => {
+    const report = await checkToolboxDist(await fixture());
+
+    expect(report.app.id).toBe("de.add-ideas.example");
+    expect(report.checkedFiles).toHaveLength(3);
+    expect(new URL(report.smoke.standaloneUrl).pathname).toBe(
+      "/__toolbox-check__/deep/nested/app/",
+    );
+    expect(
+      new URL(report.smoke.contextualUrl).searchParams.get("toolbox"),
+    ).toBe("/toolbox.catalog.json");
+    expect(report.smoke.fetchedUrls).toEqual(
+      expect.arrayContaining([
+        expect.stringContaining("/site.webmanifest"),
+        expect.stringContaining("/style.css"),
+        expect.stringContaining("/app.js"),
+      ]),
+    );
+  });
+
+  it("rejects traversal in declared assets", async () => {
+    const root = await fixture(manifest({ assets: ["../secret.txt"] }));
+    await expect(checkToolboxDist(root)).rejects.toThrow(/unsafe path/u);
+  });
+
+  it("rejects a non-SemVer manifest version", async () => {
+    const root = await fixture(manifest({ version: "next" }));
+    await expect(checkToolboxDist(root)).rejects.toThrow(/not SemVer/u);
+  });
+
+  it("rejects root-absolute HTML assets that break nested deployment", async () => {
+    const root = await fixture();
+    await writeFile(
+      join(root, "index.html"),
+      '<!doctype html><script src="/app.js"></script>',
+    );
+    await expect(checkToolboxDist(root)).rejects.toThrow(/not relocatable/u);
+  });
+});
--- a/packages/testkit/tsconfig.build.json
+++ b/packages/testkit/tsconfig.build.json
@@ -0,0 +1,9 @@
+{
+  "extends": "../../tsconfig.base.json",
+  "compilerOptions": {
+    "rootDir": "src",
+    "outDir": "dist",
+    "types": ["node"]
+  },
+  "include": ["src"]
+}
--- a/packages/testkit/tsconfig.json
+++ b/packages/testkit/tsconfig.json
@@ -0,0 +1,11 @@
+{
+  "extends": "../../tsconfig.base.json",
+  "compilerOptions": {
+    "noEmit": true,
+    "types": ["node"],
+    "paths": {
+      "@add-ideas/toolbox-contract": ["../contract/src/index.ts"]
+    }
+  },
+  "include": ["src"]
+}
--- a/schemas/toolbox-app.v1.schema.json
+++ b/schemas/toolbox-app.v1.schema.json
@@ -0,0 +1,219 @@
+{
+  "$schema": "https://json-schema.org/draft/2020-12/schema",
+  "$id": "https://git.add-ideas.de/zemion/toolbox-sdk/raw/branch/main/schemas/toolbox-app.v1.schema.json",
+  "title": "Toolbox application manifest v1",
+  "type": "object",
+  "required": [
+    "schemaVersion",
+    "id",
+    "name",
+    "version",
+    "description",
+    "entry",
+    "icon",
+    "categories",
+    "tags",
+    "integration",
+    "requirements",
+    "privacy"
+  ],
+  "properties": {
+    "schemaVersion": {
+      "const": 1
+    },
+    "id": {
+      "type": "string",
+      "pattern": "^[a-z0-9]+(?:[._-][a-z0-9]+)*$"
+    },
+    "name": {
+      "$ref": "#/$defs/nonEmptyString"
+    },
+    "version": {
+      "$ref": "#/$defs/nonEmptyString"
+    },
+    "entry": {
+      "$ref": "#/$defs/urlReference"
+    },
+    "description": {
+      "type": "string"
+    },
+    "icon": {
+      "$ref": "#/$defs/urlReference"
+    },
+    "privacy": {
+      "type": "object",
+      "required": ["processing", "fileUploads", "telemetry"],
+      "properties": {
+        "processing": {
+          "enum": ["local", "remote", "mixed"]
+        },
+        "fileUploads": {
+          "type": "boolean"
+        },
+        "telemetry": {
+          "type": "boolean"
+        },
+        "label": {
+          "$ref": "#/$defs/nonEmptyString"
+        },
+        "url": {
+          "$ref": "#/$defs/urlReference"
+        }
+      },
+      "additionalProperties": true
+    },
+    "categories": {
+      "$ref": "#/$defs/stringList"
+    },
+    "tags": {
+      "$ref": "#/$defs/stringList"
+    },
+    "integration": {
+      "type": "object",
+      "required": ["contextVersion", "launchModes", "embedding"],
+      "properties": {
+        "contextVersion": {
+          "const": 1
+        },
+        "launchModes": {
+          "type": "array",
+          "minItems": 1,
+          "uniqueItems": true,
+          "items": {
+            "enum": ["navigate", "new-tab"]
+          }
+        },
+        "embedding": {
+          "enum": ["unsupported", "supported"]
+        }
+      },
+      "additionalProperties": true
+    },
+    "requirements": {
+      "type": "object",
+      "required": [
+        "secureContext",
+        "workers",
+        "indexedDb",
+        "crossOriginIsolated"
+      ],
+      "properties": {
+        "secureContext": {
+          "type": "boolean"
+        },
+        "workers": {
+          "type": "boolean"
+        },
+        "indexedDb": {
+          "type": "boolean"
+        },
+        "crossOriginIsolated": {
+          "type": "boolean"
+        },
+        "topLevelContext": {
+          "type": "boolean"
+        }
+      },
+      "additionalProperties": true
+    },
+    "source": {
+      "type": "object",
+      "required": ["repository", "license"],
+      "properties": {
+        "repository": {
+          "$ref": "#/$defs/absoluteWebUrl"
+        },
+        "license": {
+          "$ref": "#/$defs/nonEmptyString"
+        }
+      },
+      "additionalProperties": true
+    },
+    "actions": {
+      "type": "array",
+      "items": {
+        "type": "object",
+        "required": ["id", "label", "url"],
+        "properties": {
+          "id": {
+            "type": "string",
+            "pattern": "^[a-z0-9]+(?:[._-][a-z0-9]+)*$"
+          },
+          "label": {
+            "$ref": "#/$defs/nonEmptyString"
+          },
+          "url": {
+            "$ref": "#/$defs/urlReference"
+          }
+        },
+        "additionalProperties": true
+      }
+    },
+    "assets": {
+      "type": "array",
+      "items": {
+        "$ref": "#/$defs/urlReference"
+      },
+      "uniqueItems": true
+    }
+  },
+  "$defs": {
+    "urlReference": {
+      "type": "string",
+      "allOf": [
+        {
+          "$ref": "#/$defs/nonEmptyString"
+        },
+        {
+          "type": "string",
+          "description": "Backslashes are not URL path separators in toolbox documents.",
+          "pattern": "^[^\\\\]*$"
+        },
+        {
+          "type": "string",
+          "description": "Explicit schemes are limited to HTTP and HTTPS; relative references remain valid.",
+          "pattern": "^[\\t\\n\\r ]*(?:[Hh][Tt][Tt][Pp][Ss]?:|(?!(?:[A-Za-z][A-Za-z0-9+.-]*):))"
+        },
+        {
+          "type": "string",
+          "description": "An explicit HTTP(S) authority must not be empty.",
+          "pattern": "^(?![\\t\\n\\r ]*[Hh][Tt][Tt][Pp][Ss]?:/+(?:[?#]|$))"
+        },
+        {
+          "type": "string",
+          "description": "HTTP(S) authority references must not contain credentials.",
+          "pattern": "^[\\t\\n\\r ]*(?!(?:[Hh][Tt][Tt][Pp]:/*|[Hh][Tt][Tt][Pp][Ss]:/+|/+)[^/?#]*@)"
+        }
+      ]
+    },
+    "absoluteWebUrl": {
+      "allOf": [
+        {
+          "$ref": "#/$defs/urlReference"
+        },
+        {
+          "type": "string",
+          "description": "Repository URLs must be absolute HTTP(S) URLs.",
+          "pattern": "^[\\t\\n\\r ]*[Hh][Tt][Tt][Pp][Ss]?:/*[^\\s/?#]"
+        },
+        {
+          "type": "string",
+          "description": "Absolute repository URLs must not contain credentials.",
+          "pattern": "^[\\t\\n\\r ]*(?![Hh][Tt][Tt][Pp][Ss]?:/*[^/?#]*@)"
+        }
+      ]
+    },
+    "nonEmptyString": {
+      "type": "string",
+      "pattern": "\\S"
+    },
+    "stringList": {
+      "type": "array",
+      "uniqueItems": true,
+      "items": {
+        "$ref": "#/$defs/nonEmptyString"
+      }
+    }
+  },
+  "additionalProperties": true
+}
--- a/schemas/toolbox-catalog.v1.schema.json
+++ b/schemas/toolbox-catalog.v1.schema.json
@@ -0,0 +1,115 @@
+{
+  "$schema": "https://json-schema.org/draft/2020-12/schema",
+  "$id": "https://git.add-ideas.de/zemion/toolbox-sdk/raw/branch/main/schemas/toolbox-catalog.v1.schema.json",
+  "title": "Toolbox catalog v1",
+  "type": "object",
+  "required": ["schemaVersion", "id", "name", "home", "theme", "apps"],
+  "properties": {
+    "schemaVersion": {
+      "const": 1
+    },
+    "id": {
+      "type": "string",
+      "pattern": "^[a-z0-9]+(?:[._-][a-z0-9]+)*$"
+    },
+    "name": {
+      "$ref": "#/$defs/nonEmptyString"
+    },
+    "home": {
+      "$ref": "#/$defs/urlReference"
+    },
+    "theme": {
+      "type": "object",
+      "required": ["mode", "brand"],
+      "properties": {
+        "mode": {
+          "enum": ["light", "dark", "system"]
+        },
+        "brand": {
+          "$ref": "#/$defs/nonEmptyString"
+        }
+      },
+      "additionalProperties": true
+    },
+    "apps": {
+      "type": "array",
+      "items": {
+        "oneOf": [
+          {
+            "type": "object",
+            "required": ["manifest", "enabled"],
+            "not": {
+              "required": ["entry"]
+            },
+            "properties": {
+              "manifest": {
+                "$ref": "#/$defs/urlReference"
+              },
+              "enabled": {
+                "type": "boolean"
+              }
+            },
+            "additionalProperties": true
+          },
+          {
+            "type": "object",
+            "required": ["name", "entry", "launch", "enabled"],
+            "not": {
+              "required": ["manifest"]
+            },
+            "properties": {
+              "name": {
+                "$ref": "#/$defs/nonEmptyString"
+              },
+              "entry": {
+                "$ref": "#/$defs/urlReference"
+              },
+              "launch": {
+                "enum": ["navigate", "new-tab"]
+              },
+              "enabled": {
+                "type": "boolean"
+              }
+            },
+            "additionalProperties": true
+          }
+        ]
+      }
+    }
+  },
+  "$defs": {
+    "urlReference": {
+      "type": "string",
+      "allOf": [
+        {
+          "$ref": "#/$defs/nonEmptyString"
+        },
+        {
+          "type": "string",
+          "description": "Backslashes are not URL path separators in toolbox documents.",
+          "pattern": "^[^\\\\]*$"
+        },
+        {
+          "type": "string",
+          "description": "Explicit schemes are limited to HTTP and HTTPS; relative references remain valid.",
+          "pattern": "^[\\t\\n\\r ]*(?:[Hh][Tt][Tt][Pp][Ss]?:|(?!(?:[A-Za-z][A-Za-z0-9+.-]*):))"
+        },
+        {
+          "type": "string",
+          "description": "An explicit HTTP(S) authority must not be empty.",
+          "pattern": "^(?![\\t\\n\\r ]*[Hh][Tt][Tt][Pp][Ss]?:/+(?:[?#]|$))"
+        },
+        {
+          "type": "string",
+          "description": "HTTP(S) authority references must not contain credentials.",
+          "pattern": "^[\\t\\n\\r ]*(?!(?:[Hh][Tt][Tt][Pp]:/*|[Hh][Tt][Tt][Pp][Ss]:/+|/+)[^/?#]*@)"
+        }
+      ]
+    },
+    "nonEmptyString": {
+      "type": "string",
+      "pattern": "\\S"
+    }
+  },
+  "additionalProperties": true
+}
--- a/tsconfig.base.json
+++ b/tsconfig.base.json
@@ -0,0 +1,18 @@
+{
+  "compilerOptions": {
+    "target": "ES2022",
+    "module": "NodeNext",
+    "moduleResolution": "NodeNext",
+    "lib": ["ES2022", "DOM", "DOM.Iterable"],
+    "strict": true,
+    "noUncheckedIndexedAccess": true,
+    "exactOptionalPropertyTypes": true,
+    "useUnknownInCatchVariables": true,
+    "verbatimModuleSyntax": true,
+    "forceConsistentCasingInFileNames": true,
+    "skipLibCheck": true,
+    "declaration": true,
+    "declarationMap": true,
+    "sourceMap": true
+  }
+}
--- a/vitest.config.ts
+++ b/vitest.config.ts
@@ -0,0 +1,26 @@
+import { fileURLToPath } from "node:url";
+
+import { defineConfig } from "vitest/config";
+
+const fromRoot = (path: string): string =>
+  fileURLToPath(new URL(path, import.meta.url));
+
+export default defineConfig({
+  resolve: {
+    alias: {
+      "@add-ideas/toolbox-contract": fromRoot(
+        "./packages/contract/src/index.ts",
+      ),
+      "@add-ideas/toolbox-shell-react": fromRoot(
+        "./packages/shell-react/src/index.ts",
+      ),
+    },
+  },
+  test: {
+    environment: "jsdom",
+    setupFiles: [fromRoot("./vitest.setup.ts")],
+    coverage: {
+      reporter: ["text", "html"],
+    },
+  },
+});
--- a/vitest.setup.ts
+++ b/vitest.setup.ts
@@ -0,0 +1,8 @@
+import "@testing-library/jest-dom/vitest";
+
+import { cleanup } from "@testing-library/react";
+import { afterEach } from "vitest";
+
+afterEach(() => {
+  cleanup();
+});
				`@@ -0,0 +1 @@`
				`@add-ideas:registry=https://git.add-ideas.de/api/packages/zemion/npm/`