Release Subtitle Tools 0.2.0

.gitea/workflows/verify.yml

@@ -0,0 +1,39 @@
+name: Verify
+
+on:
+  push:
+    branches: [main]
+  pull_request:
+  workflow_dispatch:
+
+concurrency:
+  group: verify-${{ gitea.repository }}-${{ gitea.ref }}
+  cancel-in-progress: true
+
+permissions:
+  contents: read
+
+jobs:
+  verify:
+    runs-on: ubuntu-latest
+    timeout-minutes: 45
+    env:
+      CI: "true"
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-node@v4
+        with:
+          node-version: "22"
+          cache: npm
+      - name: Select declared npm version
+        run: npm install --global npm@11.17.0
+      - name: Install dependencies
+        run: npm ci
+      - name: Audit runtime dependencies
+        run: npm audit --omit=dev --audit-level=moderate
+      - name: Check, test, and build
+        run: npm run check
+      - name: Install browser engines
+        run: npx playwright install --with-deps chromium firefox webkit
+      - name: Browser tests
+        run: npm run test:browser

CHANGELOG.md

@@ -1,5 +1,14 @@
 # Changelog
 
+## 0.2.0 - 2026-09-02
+
+- Added bounded flat-profile TTML import/export, timeline cue insertion,
+  duplication, split/merge/delete, text transforms and frame snapping.
+- Added immediate media playback plus cancellable background waveform extraction,
+  click/keyboard waveform navigation and stale-result suppression.
+- Declared accurate subtitle/media input, export and optional browser capability
+  profiles for Toolbox handoff.
+
 ## 0.1.0 - 2026-09-01
 
 - Added bounded SRT, WebVTT and ASS parsing, cue editing and explicit conversion.

README.md

@@ -4,25 +4,30 @@ Edit, validate, synchronize, compare, and convert subtitle files locally in the
 browser. Subtitle Tools is an independently versioned application in the
 [add·ideas Toolbox](https://git.add-ideas.de/lotobo/toolbox-portal).
 
-## Version 0.1 scope
+## Version 0.2 scope
 
-- Bounded SRT, WebVTT, ASS and legacy SSA-compatible dialogue parsing
+- Bounded SRT, WebVTT, ASS/SSA and flat-profile TTML/DFXP parsing
-- Cue timeline, direct text/timestamp editing and configurable diagnostics for
+- Cue timeline, add/duplicate/split/merge/delete operations, direct
+  text/timestamp editing, cue text transforms and configurable diagnostics for
   overlaps, order, duration, reading speed, line count and line length
-- Shift and anchor-based stretch operations, negative-time protection and
+- Shift and anchor-based stretch operations, negative-time protection,
-  explicit source/target frame-rate conversion
+  source/target frame-rate conversion and frame-grid snapping
-- SRT, WebVTT and ASS serialization with format-specific preservation where
+- SRT, WebVTT, ASS and safe flat TTML serialization with format-specific preservation where
   possible and a visible cross-format loss warning
 - Deterministic index-aligned revision comparison
-- Immediate browser-native audio/video playback plus bounded local waveform peak
+- Immediate browser-native audio/video playback while cancellable, worker-based
-  extraction and subtitle-start markers
+  waveform peak extraction continues; failed or stale jobs retain the last
+  valid waveform; the scrollable waveform provides zoom, cue selection,
+  previous/next navigation and a live playhead
 - UTF-8, UTF-16 LE/BE and ISO-8859-1 file decoding
 
 All source, media and generated output stays in the current browser. The app
 makes no external request. Validation is configurable editorial guidance, not a
-broadcast, accessibility, or legal compliance certificate. Version 0.1 does not
+broadcast, accessibility, or legal compliance certificate. Version 0.2 does not
 perform speech recognition, automatic alignment, semantic revision matching, or
-pixel-perfect ASS rendering.
+pixel-perfect ASS rendering. TTML regions, styling definitions and inherited
+timing are not laid out; cue-level references are inspected and export is a
+flat, resource-free profile.
 
 ## Development
 
@@ -37,7 +42,7 @@ npm run test:browser
 ## Release
 
 `npm run release:artifact` creates the deterministic
-`release/subtitle-tools-0.1.0.zip` and checksum sidecar.
+`release/subtitle-tools-0.2.0.zip` and checksum sidecar.
 
 ## Licence
 

SOURCE.md

@@ -1,7 +1,7 @@
 # Corresponding source
 
-The corresponding source for Subtitle Tools 0.1.0 is available at:
+The corresponding source for Subtitle Tools 0.2.0 is available at:
 
-https://git.add-ideas.de/lotobo/subtitle-tools/src/tag/v0.1.0
+https://git.add-ideas.de/lotobo/subtitle-tools/src/tag/v0.2.0
 
 Build with Node.js 22, npm 11, `npm ci`, and `npm run release:artifact`.

THIRD_PARTY_NOTICES.md

@@ -1,12 +1,12 @@
 # Third-party notices
 
-Subtitle Tools 0.1.0 directly depends on these runtime packages:
+Subtitle Tools 0.2.0 directly depends on these runtime packages:
 
 | Package                          | Pinned version | Declared licence |
 | -------------------------------- | -------------: | ---------------- |
-| `@add-ideas/toolbox-contract`    |          0.2.3 | Apache-2.0       |
+| `@add-ideas/toolbox-contract`    |          0.3.0 | Apache-2.0       |
-| `@add-ideas/toolbox-helpers`     |          0.1.0 | GPL-3.0-or-later |
+| `@add-ideas/toolbox-helpers`     |          0.2.0 | GPL-3.0-or-later |
-| `@add-ideas/toolbox-shell-react` |          0.2.3 | Apache-2.0       |
+| `@add-ideas/toolbox-shell-react` |          0.3.0 | Apache-2.0       |
 | `react`                          |         19.2.8 | MIT              |
 | `react-dom`                      |         19.2.8 | MIT              |
 

docs/ACCESSIBILITY.md

@@ -1,6 +1,6 @@
 # Accessibility
 
-The application uses labelled native controls, keyboard-reachable tabs and cue
+The application uses labelled native controls, keyboard-reachable pressed-state workspace buttons and cue
 buttons, visible focus indicators, text alternatives for waveform content, and
 light, dark and system themes. Colour is not the only carrier for issue level.
 The cue and issue views cap rendered rows to keep navigation responsive while

docs/ARCHITECTURE.md

@@ -2,16 +2,24 @@
 
 Subtitle Tools is a relocatable React application with a framework-independent
 TypeScript subtitle model. The parser first applies byte/text and line bounds,
-then produces one normalized cue model for SRT, WebVTT and ASS. Operations return
+then produces one normalized cue model for SRT, WebVTT, ASS and a bounded flat
-new documents instead of mutating parser state. Serializers are format-specific;
+TTML profile. XML document types/entities are rejected; TTML resources,
-cross-format export deliberately exposes its preservation boundary.
+inherited timing and layout are never resolved. Cue structure/text/timing
+operations return new documents instead of mutating parser state. Serializers
+are format-specific; cross-format export deliberately exposes its preservation
+boundary.
 
-Parsing and timing transformations are synchronous in v0.1 and therefore capped
+Parsing and timing transformations are synchronous in v0.2 and therefore capped
 at 4,000,000 UTF-16 units, 250,000 units per physical line and 100,000 cues. The
 editor renders at most 10,000 cue rows and 2,000 issue rows, while validation and
 export still cover the complete bounded document. Revision comparison is
 index-aligned and linear rather than an unbounded semantic diff.
 
-The optional waveform component uses browser-native media decoding, keeps at
+The optional waveform component creates a browser-native playback URL as soon as
-most 2,000 peak buckets and accepts no more than 128 MiB or four decoded hours.
+media is selected. Decoding continues independently and transfers one PCM
-It does not run a codec, speech-recognition model or network service.
+channel to a disposable module worker, which produces at most 2,000 peak
+buckets. Replacement and cancellation terminate the worker, suppress stale
+results and retain the last valid waveform. Zoom/navigation changes only the
+bounded peak view and native playback position. Inputs remain capped at 128 MiB
+and four decoded hours; no codec, speech-recognition model or network service
+runs.

docs/PRIVACY-SECURITY.md

@@ -6,9 +6,12 @@ other network destination exists. The production policy uses
 `connect-src 'self'`; browser tests fail on non-local requests.
 
 Subtitle text is rendered by React as text, not interpreted as HTML. ASS override
-codes and WebVTT tags are preserved as inert source. Exports are downloads chosen
+codes and WebVTT tags are preserved as inert source. TTML import rejects document
-by the user. Browser-native media playback and Web Audio decoding inherit browser
+types and entity declarations and reads a deliberately flat, bounded profile; it
-codec support and may allocate substantial memory inside the documented bounds.
+does not fetch referenced styles, images, fonts or other resources. Exports are
+downloads chosen by the user. Browser-native media playback and Web Audio
+decoding inherit browser codec support and may allocate substantial memory inside
+the documented bounds.
 
 Validation findings are editorial signals. They are not proof of accessibility,
 broadcast conformance, synchronization quality or legal compliance. Cross-format

package-lock.json

@@ -1,22 +1,22 @@
 {
   "name": "subtitle-tools",
-  "version": "0.1.0",
+  "version": "0.2.0",
   "lockfileVersion": 3,
   "requires": true,
   "packages": {
     "": {
       "name": "subtitle-tools",
-      "version": "0.1.0",
+      "version": "0.2.0",
       "license": "GPL-3.0-or-later",
       "dependencies": {
-        "@add-ideas/toolbox-contract": "0.2.3",
+        "@add-ideas/toolbox-contract": "0.3.0",
-        "@add-ideas/toolbox-helpers": "0.1.0",
+        "@add-ideas/toolbox-helpers": "0.2.0",
-        "@add-ideas/toolbox-shell-react": "0.2.3",
+        "@add-ideas/toolbox-shell-react": "0.3.0",
         "react": "19.2.8",
         "react-dom": "19.2.8"
       },
       "devDependencies": {
-        "@add-ideas/toolbox-testkit": "0.2.3",
+        "@add-ideas/toolbox-testkit": "0.3.0",
         "@eslint/js": "10.0.1",
         "@playwright/test": "1.62.1",
         "@testing-library/jest-dom": "6.9.1",
@@ -42,24 +42,24 @@
       }
     },
     "node_modules/@add-ideas/toolbox-contract": {
-      "version": "0.2.3",
+      "version": "0.3.0",
-      "license": "Apache-2.0",
+      "resolved": "https://git.add-ideas.de/api/packages/lotobo/npm/%40add-ideas%2Ftoolbox-contract/-/0.3.0/toolbox-contract-0.3.0.tgz",
-      "engines": {
+      "integrity": "sha512-dKrK7BjOFwqJaBfJuhKxZKIld4sH0AKjEn6a0yLnbdMUFY+fFv4VSLGV2tNSBD016gumc2iNqOjUj/ld7x4rtA==",
-        "node": ">=20"
+      "license": "Apache-2.0"
-      }
     },
     "node_modules/@add-ideas/toolbox-helpers": {
-      "version": "0.1.0",
+      "version": "0.2.0",
-      "license": "GPL-3.0-or-later",
+      "resolved": "https://git.add-ideas.de/api/packages/lotobo/npm/%40add-ideas%2Ftoolbox-helpers/-/0.2.0/toolbox-helpers-0.2.0.tgz",
-      "engines": {
+      "integrity": "sha512-SdOqkw+P+3J3fa5iVkzb5P15rVepB001GNV21Oh8w0CZcVL+YRltgD/s+MVcTyrNijWQf3E5vtQON/3N2LLyKg==",
-        "node": ">=22"
+      "license": "GPL-3.0-or-later"
-      }
     },
     "node_modules/@add-ideas/toolbox-shell-react": {
-      "version": "0.2.3",
+      "version": "0.3.0",
+      "resolved": "https://git.add-ideas.de/api/packages/lotobo/npm/%40add-ideas%2Ftoolbox-shell-react/-/0.3.0/toolbox-shell-react-0.3.0.tgz",
+      "integrity": "sha512-74p6JzAOG0YCAKdlc1hLofV4ZIko7vb448S75cIiM88PKm93EHl5VD7g8YVyfM56Ui97UY9dmy+Whiq4sGzpsg==",
       "license": "Apache-2.0",
       "dependencies": {
-        "@add-ideas/toolbox-contract": "0.2.3"
+        "@add-ideas/toolbox-contract": "0.3.0"
       },
       "peerDependencies": {
         "react": ">=18 <20",
@@ -67,17 +67,16 @@
       }
     },
     "node_modules/@add-ideas/toolbox-testkit": {
-      "version": "0.2.3",
+      "version": "0.3.0",
+      "resolved": "https://git.add-ideas.de/api/packages/lotobo/npm/%40add-ideas%2Ftoolbox-testkit/-/0.3.0/toolbox-testkit-0.3.0.tgz",
+      "integrity": "sha512-4Fk+oSvZFspOMIXr8Xy040nhAaBsIQAzsGyXWSpjn3+k3yBKq7nB1r5zCHhsXzfdLzvPDAx2KcmSNOhM330D9w==",
       "dev": true,
       "license": "Apache-2.0",
       "dependencies": {
-        "@add-ideas/toolbox-contract": "0.2.3"
+        "@add-ideas/toolbox-contract": "0.3.0"
       },
       "bin": {
         "toolbox-check": "dist/cli.js"
-      },
-      "engines": {
-        "node": ">=20"
       }
     },
     "node_modules/@adobe/css-tools": {

package.json

@@ -1,6 +1,6 @@
 {
   "name": "subtitle-tools",
-  "version": "0.1.0",
+  "version": "0.2.0",
   "description": "Edit, validate, synchronize, compare, and convert subtitles locally in the browser.",
   "license": "GPL-3.0-or-later",
   "author": "Albrecht Degering",
@@ -39,14 +39,14 @@
     "release:artifact": "npm run check && npm run test:browser && npm run package:release -- --force"
   },
   "dependencies": {
-    "@add-ideas/toolbox-contract": "0.2.3",
+    "@add-ideas/toolbox-contract": "0.3.0",
-    "@add-ideas/toolbox-helpers": "0.1.0",
+    "@add-ideas/toolbox-helpers": "0.2.0",
-    "@add-ideas/toolbox-shell-react": "0.2.3",
+    "@add-ideas/toolbox-shell-react": "0.3.0",
     "react": "19.2.8",
     "react-dom": "19.2.8"
   },
   "devDependencies": {
-    "@add-ideas/toolbox-testkit": "0.2.3",
+    "@add-ideas/toolbox-testkit": "0.3.0",
     "@eslint/js": "10.0.1",
     "@playwright/test": "1.62.1",
     "@testing-library/jest-dom": "6.9.1",

playwright.config.ts

@@ -15,7 +15,25 @@ export default defineConfig({
     timeout: 180_000,
   },
   projects: [
-    { name: "chromium", use: { ...devices["Desktop Chrome"] } },
+    {
-    { name: "firefox", use: { ...devices["Desktop Firefox"] } },
+      name: "chromium",
+      testIgnore: /responsive\.spec\.ts/,
+      use: { ...devices["Desktop Chrome"] },
+    },
+    {
+      name: "firefox",
+      testIgnore: /responsive\.spec\.ts/,
+      use: { ...devices["Desktop Firefox"] },
+    },
+    {
+      name: "webkit",
+      testIgnore: /responsive\.spec\.ts/,
+      use: { ...devices["Desktop Safari"] },
+    },
+    {
+      name: "mobile-chromium",
+      testMatch: /responsive\.spec\.ts/,
+      use: { ...devices["Pixel 5"] },
+    },
   ],
 });

public/CHANGELOG.md

@@ -1,5 +1,14 @@
 # Changelog
 
+## 0.2.0 - 2026-09-02
+
+- Added bounded flat-profile TTML import/export, timeline cue insertion,
+  duplication, split/merge/delete, text transforms and frame snapping.
+- Added immediate media playback plus cancellable background waveform extraction,
+  click/keyboard waveform navigation and stale-result suppression.
+- Declared accurate subtitle/media input, export and optional browser capability
+  profiles for Toolbox handoff.
+
 ## 0.1.0 - 2026-09-01
 
 - Added bounded SRT, WebVTT and ASS parsing, cue editing and explicit conversion.

public/LICENSES/npm-runtime-licenses.txt

@@ -1,5 +1,5 @@
 ==============================================================================
-@add-ideas/toolbox-contract@0.2.3
+@add-ideas/toolbox-contract@0.3.0
 Declared licence: Apache-2.0
 ==============================================================================
 --- LICENSE ---
@@ -198,7 +198,7 @@ Declared licence: Apache-2.0
 
 
 ==============================================================================
-@add-ideas/toolbox-helpers@0.1.0
+@add-ideas/toolbox-helpers@0.2.0
 Declared licence: GPL-3.0-or-later
 ==============================================================================
 --- LICENSE ---
@@ -879,7 +879,7 @@ Public License instead of this License.  But first, please read
 
 
 ==============================================================================
-@add-ideas/toolbox-shell-react@0.2.3
+@add-ideas/toolbox-shell-react@0.3.0
 Declared licence: Apache-2.0
 ==============================================================================
 --- LICENSE ---

public/README.md

@@ -4,25 +4,30 @@ Edit, validate, synchronize, compare, and convert subtitle files locally in the
 browser. Subtitle Tools is an independently versioned application in the
 [add·ideas Toolbox](https://git.add-ideas.de/lotobo/toolbox-portal).
 
-## Version 0.1 scope
+## Version 0.2 scope
 
-- Bounded SRT, WebVTT, ASS and legacy SSA-compatible dialogue parsing
+- Bounded SRT, WebVTT, ASS/SSA and flat-profile TTML/DFXP parsing
-- Cue timeline, direct text/timestamp editing and configurable diagnostics for
+- Cue timeline, add/duplicate/split/merge/delete operations, direct
+  text/timestamp editing, cue text transforms and configurable diagnostics for
   overlaps, order, duration, reading speed, line count and line length
-- Shift and anchor-based stretch operations, negative-time protection and
+- Shift and anchor-based stretch operations, negative-time protection,
-  explicit source/target frame-rate conversion
+  source/target frame-rate conversion and frame-grid snapping
-- SRT, WebVTT and ASS serialization with format-specific preservation where
+- SRT, WebVTT, ASS and safe flat TTML serialization with format-specific preservation where
   possible and a visible cross-format loss warning
 - Deterministic index-aligned revision comparison
-- Immediate browser-native audio/video playback plus bounded local waveform peak
+- Immediate browser-native audio/video playback while cancellable, worker-based
-  extraction and subtitle-start markers
+  waveform peak extraction continues; failed or stale jobs retain the last
+  valid waveform; the scrollable waveform provides zoom, cue selection,
+  previous/next navigation and a live playhead
 - UTF-8, UTF-16 LE/BE and ISO-8859-1 file decoding
 
 All source, media and generated output stays in the current browser. The app
 makes no external request. Validation is configurable editorial guidance, not a
-broadcast, accessibility, or legal compliance certificate. Version 0.1 does not
+broadcast, accessibility, or legal compliance certificate. Version 0.2 does not
 perform speech recognition, automatic alignment, semantic revision matching, or
-pixel-perfect ASS rendering.
+pixel-perfect ASS rendering. TTML regions, styling definitions and inherited
+timing are not laid out; cue-level references are inspected and export is a
+flat, resource-free profile.
 
 ## Development
 
@@ -37,7 +42,7 @@ npm run test:browser
 ## Release
 
 `npm run release:artifact` creates the deterministic
-`release/subtitle-tools-0.1.0.zip` and checksum sidecar.
+`release/subtitle-tools-0.2.0.zip` and checksum sidecar.
 
 ## Licence
 

public/SOURCE.md

@@ -1,7 +1,7 @@
 # Corresponding source
 
-The corresponding source for Subtitle Tools 0.1.0 is available at:
+The corresponding source for Subtitle Tools 0.2.0 is available at:
 
-https://git.add-ideas.de/lotobo/subtitle-tools/src/tag/v0.1.0
+https://git.add-ideas.de/lotobo/subtitle-tools/src/tag/v0.2.0
 
 Build with Node.js 22, npm 11, `npm ci`, and `npm run release:artifact`.

public/THIRD_PARTY_NOTICES.md

@@ -1,12 +1,12 @@
 # Third-party notices
 
-Subtitle Tools 0.1.0 directly depends on these runtime packages:
+Subtitle Tools 0.2.0 directly depends on these runtime packages:
 
 | Package                          | Pinned version | Declared licence |
 | -------------------------------- | -------------: | ---------------- |
-| `@add-ideas/toolbox-contract`    |          0.2.3 | Apache-2.0       |
+| `@add-ideas/toolbox-contract`    |          0.3.0 | Apache-2.0       |
-| `@add-ideas/toolbox-helpers`     |          0.1.0 | GPL-3.0-or-later |
+| `@add-ideas/toolbox-helpers`     |          0.2.0 | GPL-3.0-or-later |
-| `@add-ideas/toolbox-shell-react` |          0.2.3 | Apache-2.0       |
+| `@add-ideas/toolbox-shell-react` |          0.3.0 | Apache-2.0       |
 | `react`                          |         19.2.8 | MIT              |
 | `react-dom`                      |         19.2.8 | MIT              |
 

public/docs/ACCESSIBILITY.md

@@ -1,6 +1,6 @@
 # Accessibility
 
-The application uses labelled native controls, keyboard-reachable tabs and cue
+The application uses labelled native controls, keyboard-reachable pressed-state workspace buttons and cue
 buttons, visible focus indicators, text alternatives for waveform content, and
 light, dark and system themes. Colour is not the only carrier for issue level.
 The cue and issue views cap rendered rows to keep navigation responsive while

public/docs/ARCHITECTURE.md

@@ -2,16 +2,24 @@
 
 Subtitle Tools is a relocatable React application with a framework-independent
 TypeScript subtitle model. The parser first applies byte/text and line bounds,
-then produces one normalized cue model for SRT, WebVTT and ASS. Operations return
+then produces one normalized cue model for SRT, WebVTT, ASS and a bounded flat
-new documents instead of mutating parser state. Serializers are format-specific;
+TTML profile. XML document types/entities are rejected; TTML resources,
-cross-format export deliberately exposes its preservation boundary.
+inherited timing and layout are never resolved. Cue structure/text/timing
+operations return new documents instead of mutating parser state. Serializers
+are format-specific; cross-format export deliberately exposes its preservation
+boundary.
 
-Parsing and timing transformations are synchronous in v0.1 and therefore capped
+Parsing and timing transformations are synchronous in v0.2 and therefore capped
 at 4,000,000 UTF-16 units, 250,000 units per physical line and 100,000 cues. The
 editor renders at most 10,000 cue rows and 2,000 issue rows, while validation and
 export still cover the complete bounded document. Revision comparison is
 index-aligned and linear rather than an unbounded semantic diff.
 
-The optional waveform component uses browser-native media decoding, keeps at
+The optional waveform component creates a browser-native playback URL as soon as
-most 2,000 peak buckets and accepts no more than 128 MiB or four decoded hours.
+media is selected. Decoding continues independently and transfers one PCM
-It does not run a codec, speech-recognition model or network service.
+channel to a disposable module worker, which produces at most 2,000 peak
+buckets. Replacement and cancellation terminate the worker, suppress stale
+results and retain the last valid waveform. Zoom/navigation changes only the
+bounded peak view and native playback position. Inputs remain capped at 128 MiB
+and four decoded hours; no codec, speech-recognition model or network service
+runs.

public/docs/PRIVACY-SECURITY.md

@@ -6,9 +6,12 @@ other network destination exists. The production policy uses
 `connect-src 'self'`; browser tests fail on non-local requests.
 
 Subtitle text is rendered by React as text, not interpreted as HTML. ASS override
-codes and WebVTT tags are preserved as inert source. Exports are downloads chosen
+codes and WebVTT tags are preserved as inert source. TTML import rejects document
-by the user. Browser-native media playback and Web Audio decoding inherit browser
+types and entity declarations and reads a deliberately flat, bounded profile; it
-codec support and may allocate substantial memory inside the documented bounds.
+does not fetch referenced styles, images, fonts or other resources. Exports are
+downloads chosen by the user. Browser-native media playback and Web Audio
+decoding inherit browser codec support and may allocate substantial memory inside
+the documented bounds.
 
 Validation findings are editorial signals. They are not proof of accessibility,
 broadcast conformance, synchronization quality or legal compliance. Cross-format

public/sw.js

@@ -1,5 +1,5 @@
 const CACHE_PREFIX = "subtitle-tools-shell-";
-const CACHE_NAME = CACHE_PREFIX + "0.1.0";
+const CACHE_NAME = CACHE_PREFIX + "0.2.0";
 const CORE = ["./", "./manifest.webmanifest", "./favicon.svg"];
 self.addEventListener("install", (event) => {
   event.waitUntil(

public/toolbox-app.json

@@ -3,12 +3,12 @@
   "schemaVersion": 1,
   "id": "de.add-ideas.subtitle-tools",
   "name": "Subtitle Tools",
-  "version": "0.1.0",
+  "version": "0.2.0",
-  "description": "Edit, validate, synchronize, compare, and convert subtitles locally.",
+  "description": "Edit, navigate, synchronize and convert subtitles locally.",
   "entry": "./",
   "icon": "./favicon.svg",
   "categories": ["media", "text", "productivity"],
-  "tags": ["subtitles", "captions", "srt", "webvtt", "ass", "timing"],
+  "tags": ["subtitles", "captions", "srt", "webvtt", "ass", "ttml", "timing"],
   "integration": {
     "contextVersion": 1,
     "launchModes": ["navigate", "new-tab"],
@@ -21,6 +21,27 @@
     "crossOriginIsolated": false,
     "topLevelContext": false
   },
+  "io": {
+    "accepts": [
+      { "mediaType": "text/plain", "extensions": [".srt", ".ass", ".ssa"] },
+      { "mediaType": "text/vtt", "extensions": [".vtt"] },
+      {
+        "mediaType": "application/ttml+xml",
+        "extensions": [".ttml", ".dfxp", ".xml"]
+      },
+      { "mediaType": "audio/*", "extensions": [] },
+      { "mediaType": "video/*", "extensions": [] }
+    ],
+    "produces": [
+      { "mediaType": "text/plain", "extensions": [".srt", ".ass"] },
+      { "mediaType": "text/vtt", "extensions": [".vtt"] },
+      { "mediaType": "application/ttml+xml", "extensions": [".ttml"] }
+    ]
+  },
+  "capabilities": {
+    "required": [],
+    "optional": ["workers", "web-audio", "media-playback"]
+  },
   "privacy": {
     "processing": "local",
     "fileUploads": true,

src/components/HelpDialog.tsx

@@ -32,8 +32,8 @@ export function HelpDialog({
         </button>
       </div>
       <p>
-        Edit, validate, synchronize, compare, and convert SRT, WebVTT, and ASS
+        Edit, validate, synchronize, compare, and convert SRT, WebVTT, ASS, and
-        subtitles locally in the browser.
+        flat-profile TTML subtitles locally in the browser.
       </p>
       <p>
         Subtitle and optional media inputs are bounded and remain on this

src/components/Waveform.tsx

@@ -1,28 +1,63 @@
 import { useEffect, useRef, useState } from "react";
+import { DEFAULT_PEAK_COUNT, extractPeaks } from "../media/peaks";
 import type { Cue } from "../subtitle/model";
 
+interface MediaData {
+  id: number;
+  name: string;
+  url: string;
+}
+
 interface WaveformData {
+  mediaId: number;
   duration: number;
   peaks: Float32Array;
-  url: string;
+}
+
+interface ExtractionJob {
+  id: number;
+  cancelled: boolean;
+  context?: AudioContext;
+  worker?: Worker;
+  rejectPeaks?: (reason: DOMException) => void;
 }
 
 const MAX_AUDIO_BYTES = 128 * 1024 * 1024;
 const MAX_DURATION_SECONDS = 4 * 60 * 60;
-const PEAK_COUNT = 2_000;
 
-export function Waveform({ cues }: { cues: readonly Cue[] }) {
+export function Waveform({
+  cues,
+  selectedIndex,
+  onSelectCue,
+}: {
+  cues: readonly Cue[];
+  selectedIndex: number;
+  onSelectCue: (index: number) => void;
+}) {
   const canvas = useRef<HTMLCanvasElement>(null);
   const audio = useRef<HTMLAudioElement>(null);
+  const mediaRef = useRef<MediaData | undefined>(undefined);
+  const jobRef = useRef<ExtractionJob | undefined>(undefined);
+  const sequence = useRef(0);
+  const [media, setMedia] = useState<MediaData>();
   const [waveform, setWaveform] = useState<WaveformData>();
   const [error, setError] = useState("");
   const [busy, setBusy] = useState(false);
+  const [zoom, setZoom] = useState(1);
+  const [currentTime, setCurrentTime] = useState(0);
 
   useEffect(
     () => () => {
-      if (waveform) URL.revokeObjectURL(waveform.url);
+      const job = jobRef.current;
+      if (job) {
+        job.cancelled = true;
+        job.worker?.terminate();
+        job.rejectPeaks?.(abortError());
+        void job.context?.close().catch(() => undefined);
+      }
+      if (mediaRef.current) URL.revokeObjectURL(mediaRef.current.url);
     },
-    [waveform],
+    [],
   );
 
   useEffect(() => {
@@ -39,6 +74,14 @@ export function Waveform({ cues }: { cues: readonly Cue[] }) {
     const style = getComputedStyle(node);
     context.fillStyle = style.getPropertyValue("--wave-bg") || "#f1f2f7";
     context.fillRect(0, 0, width, height);
+    const selectedCue = cues[selectedIndex];
+    if (selectedCue) {
+      const x = (selectedCue.startMs / 1000 / waveform.duration) * width;
+      const end = (selectedCue.endMs / 1000 / waveform.duration) * width;
+      context.fillStyle =
+        style.getPropertyValue("--cue-selected") || "rgba(91,78,196,.18)";
+      context.fillRect(x, 0, Math.max(1, end - x), height);
+    }
     context.strokeStyle = style.getPropertyValue("--wave-line") || "#5b4ec4";
     context.beginPath();
     waveform.peaks.forEach((peak, index) => {
@@ -57,7 +100,78 @@ export function Waveform({ cues }: { cues: readonly Cue[] }) {
       context.lineTo(x, height);
       context.stroke();
     }
-  }, [cues, waveform]);
+    const playhead = (currentTime / waveform.duration) * width;
+    if (playhead >= 0 && playhead <= width) {
+      context.globalAlpha = 1;
+      context.strokeStyle = style.getPropertyValue("--playhead") || "#111827";
+      context.beginPath();
+      context.moveTo(playhead, 0);
+      context.lineTo(playhead, height);
+      context.stroke();
+    }
+  }, [cues, waveform, selectedIndex, currentTime, zoom]);
+
+  const isCurrent = (job: ExtractionJob) =>
+    !job.cancelled && jobRef.current === job;
+
+  const stopJob = (message?: string) => {
+    const job = jobRef.current;
+    if (!job) return;
+    job.cancelled = true;
+    job.worker?.terminate();
+    job.rejectPeaks?.(abortError());
+    void job.context?.close().catch(() => undefined);
+    jobRef.current = undefined;
+    setBusy(false);
+    if (message) setError(message);
+  };
+
+  const calculatePeaks = (
+    samples: Float32Array,
+    job: ExtractionJob,
+  ): Promise<Float32Array> => {
+    if (typeof Worker === "undefined")
+      return Promise.resolve(extractPeaks(samples, DEFAULT_PEAK_COUNT));
+    return new Promise((resolve, reject) => {
+      const worker = new Worker(
+        new URL("../media/peaks.worker.ts", import.meta.url),
+        { type: "module" },
+      );
+      job.worker = worker;
+      job.rejectPeaks = reject;
+      worker.onmessage = (
+        event: MessageEvent<{
+          id: number;
+          peaks?: ArrayBuffer;
+          error?: string;
+        }>,
+      ) => {
+        if (event.data.id !== job.id || !isCurrent(job)) return;
+        worker.terminate();
+        job.worker = undefined;
+        job.rejectPeaks = undefined;
+        if (event.data.error) reject(new Error(event.data.error));
+        else if (event.data.peaks) resolve(new Float32Array(event.data.peaks));
+        else reject(new Error("Peak worker returned no result."));
+      };
+      worker.onerror = () => {
+        worker.terminate();
+        job.worker = undefined;
+        job.rejectPeaks = undefined;
+        reject(new Error("Peak worker failed."));
+      };
+      const transferable = samples.slice();
+      worker.postMessage(
+        {
+          id: job.id,
+          samples: transferable.buffer,
+          length: transferable.length,
+          count: DEFAULT_PEAK_COUNT,
+        },
+        [transferable.buffer],
+      );
+    });
+  };
 
   const open = async (file: File | undefined) => {
     if (!file) return;
@@ -65,8 +179,20 @@ export function Waveform({ cues }: { cues: readonly Cue[] }) {
       setError("Audio exceeds the 128 MiB waveform limit.");
       return;
     }
+
+    stopJob();
+    const id = ++sequence.current;
+    const nextMedia = { id, name: file.name, url: URL.createObjectURL(file) };
+    const previous = mediaRef.current;
+    mediaRef.current = nextMedia;
+    setMedia(nextMedia);
+    setCurrentTime(0);
+    if (previous) URL.revokeObjectURL(previous.url);
     setBusy(true);
     setError("");
+    const job: ExtractionJob = { id, cancelled: false };
+    jobRef.current = job;
+
     try {
       const AudioContextConstructor =
         globalThis.AudioContext ??
@@ -78,51 +204,71 @@ export function Waveform({ cues }: { cues: readonly Cue[] }) {
       if (!AudioContextConstructor)
         throw new Error("Web Audio is unavailable.");
       const context = new AudioContextConstructor();
-      try {
+      job.context = context;
-        const decoded = await context.decodeAudioData(await file.arrayBuffer());
+      const decoded = await context.decodeAudioData(await file.arrayBuffer());
-        if (
+      if (!isCurrent(job)) return;
-          !Number.isFinite(decoded.duration) ||
+      if (
-          decoded.duration > MAX_DURATION_SECONDS
+        !Number.isFinite(decoded.duration) ||
-        )
+        decoded.duration <= 0 ||
-          throw new Error(
+        decoded.duration > MAX_DURATION_SECONDS
-            "Decoded audio exceeds the four-hour waveform limit.",
+      )
-          );
+        throw new Error(
-        const channel = decoded.getChannelData(0);
+          "Decoded audio must have a positive duration within the four-hour waveform limit.",
-        const peaks = new Float32Array(Math.min(PEAK_COUNT, channel.length));
+        );
-        const stride = Math.max(1, Math.floor(channel.length / peaks.length));
+      const peaks = await calculatePeaks(decoded.getChannelData(0), job);
-        for (let bucket = 0; bucket < peaks.length; bucket += 1) {
+      if (!isCurrent(job)) return;
-          let peak = 0;
+      setWaveform({ mediaId: id, duration: decoded.duration, peaks });
-          const end = Math.min(channel.length, (bucket + 1) * stride);
-          for (let index = bucket * stride; index < end; index += 1)
-            peak = Math.max(peak, Math.abs(channel[index] ?? 0));
-          peaks[bucket] = peak;
-        }
-        const url = URL.createObjectURL(file);
-        setWaveform((current) => {
-          if (current) URL.revokeObjectURL(current.url);
-          return { duration: decoded.duration, peaks, url };
-        });
-      } finally {
-        await context.close();
-      }
     } catch (reason) {
-      setError(
+      if (isCurrent(job))
-        reason instanceof Error ? reason.message : "Audio decode failed.",
+        setError(
-      );
+          reason instanceof Error ? reason.message : "Audio decode failed.",
+        );
     } finally {
-      setBusy(false);
+      void job.context?.close().catch(() => undefined);
+      job.context = undefined;
+      if (isCurrent(job)) {
+        jobRef.current = undefined;
+        setBusy(false);
+      }
     }
   };
 
+  const waveformMatchesMedia = Boolean(
+    media && waveform && media.id === waveform.mediaId,
+  );
   const seek = (event: React.MouseEvent<HTMLCanvasElement>) => {
-    if (!waveform || !audio.current) return;
+    if (!waveform || !waveformMatchesMedia || !audio.current) return;
     const bounds = event.currentTarget.getBoundingClientRect();
-    audio.current.currentTime =
+    const time =
       ((event.clientX - bounds.left) / Math.max(1, bounds.width)) *
       waveform.duration;
+    audio.current.currentTime = time;
+    setCurrentTime(time);
+    const containing = cues.findIndex(
+      (cue) => cue.startMs / 1000 <= time && cue.endMs / 1000 >= time,
+    );
+    const nearest = cues.reduce(
+      (best, cue, index) =>
+        Math.abs(cue.startMs / 1000 - time) < best.distance
+          ? { index, distance: Math.abs(cue.startMs / 1000 - time) }
+          : best,
+      { index: -1, distance: Number.POSITIVE_INFINITY },
+    ).index;
+    if (containing >= 0 || nearest >= 0)
+      onSelectCue(containing >= 0 ? containing : nearest);
     void audio.current.play();
   };
 
+  const jumpToCue = (index: number) => {
+    const cue = cues[index];
+    if (!cue) return;
+    onSelectCue(index);
+    if (audio.current) {
+      audio.current.currentTime = cue.startMs / 1000;
+      setCurrentTime(cue.startMs / 1000);
+    }
+  };
+
   return (
     <section className="waveform-workspace">
       <div className="panel-heading">
@@ -130,39 +276,128 @@ export function Waveform({ cues }: { cues: readonly Cue[] }) {
           <p className="eyebrow">Optional local media</p>
           <h2>Waveform synchronization</h2>
         </div>
-        <label className="file-button">
+        <div className="button-row">
-          {busy ? "Decoding…" : "Open audio"}
+          <label className="file-button">
-          <input
+            {media ? "Replace media" : "Open media"}
-            type="file"
+            <input
-            accept="audio/*,video/*"
+              type="file"
-            disabled={busy}
+              accept="audio/*,video/*"
-            onChange={(event) => void open(event.target.files?.[0])}
+              onChange={(event) => void open(event.target.files?.[0])}
-          />
+            />
-        </label>
+          </label>
+          {busy ? (
+            <button
+              type="button"
+              onClick={() =>
+                stopJob(
+                  "Waveform extraction cancelled. Playback remains available.",
+                )
+              }
+            >
+              Cancel waveform
+            </button>
+          ) : null}
+        </div>
       </div>
       <p className="muted">
-        Native playback is available immediately. Peak extraction is bounded and
+        Native playback is attached as soon as a file is chosen. Decoding and
-        stays in this browser; it is not speech recognition or automatic
+        bounded peak extraction continue separately and never replace the last
-        alignment.
+        valid waveform with an empty or failed result.
       </p>
+      {busy ? (
+        <p role="status">
+          <progress aria-label="Waveform extraction" /> Extracting waveform for{" "}
+          {media?.name}…
+        </p>
+      ) : null}
       {error && (
         <p className="error" role="alert">
           {error}
         </p>
       )}
+      {media ? (
+        <audio
+          ref={audio}
+          src={media.url}
+          controls
+          preload="metadata"
+          onTimeUpdate={(event) =>
+            setCurrentTime(event.currentTarget.currentTime)
+          }
+        />
+      ) : null}
       {waveform ? (
         <>
-          <audio ref={audio} src={waveform.url} controls preload="metadata" />
+          {media && !waveformMatchesMedia ? (
-          <canvas
+            <p className="muted">
-            ref={canvas}
+              Showing the previous valid waveform until the new one is ready.
-            className="waveform"
+            </p>
-            aria-label="Audio waveform with subtitle start markers"
+          ) : null}
-            onClick={seek}
+          <div className="waveform-navigation">
-          />
+            <button
+              type="button"
+              disabled={!waveformMatchesMedia || selectedIndex <= 0}
+              onClick={() => jumpToCue(selectedIndex - 1)}
+            >
+              Previous cue
+            </button>
+            <button
+              type="button"
+              disabled={
+                !waveformMatchesMedia || selectedIndex + 1 >= cues.length
+              }
+              onClick={() => jumpToCue(selectedIndex + 1)}
+            >
+              Next cue
+            </button>
+            <label>
+              Waveform zoom
+              <input
+                type="range"
+                min="1"
+                max="8"
+                step="0.5"
+                value={zoom}
+                onChange={(event) => setZoom(event.target.valueAsNumber)}
+              />
+              <output>{zoom.toFixed(1)}×</output>
+            </label>
+            <output aria-label="Playback time">
+              {currentTime.toFixed(2)} s
+            </output>
+          </div>
+          <div className="waveform-scroll">
+            <canvas
+              ref={canvas}
+              className="waveform"
+              style={{ width: `${zoom * 100}%` }}
+              aria-label="Audio waveform with subtitle start markers"
+              aria-disabled={!waveformMatchesMedia}
+              tabIndex={waveformMatchesMedia ? 0 : -1}
+              onClick={seek}
+              onKeyDown={(event) => {
+                if (event.key === "ArrowLeft") {
+                  event.preventDefault();
+                  jumpToCue(Math.max(0, selectedIndex - 1));
+                } else if (event.key === "ArrowRight") {
+                  event.preventDefault();
+                  jumpToCue(Math.min(cues.length - 1, selectedIndex + 1));
+                }
+              }}
+            />
+          </div>
         </>
+      ) : media ? (
+        <p className="empty">
+          Playback is ready; waveform extraction is still pending.
+        </p>
       ) : (
         <p className="empty">Choose a browser-decodable audio or video file.</p>
       )}
     </section>
   );
 }
+
+function abortError(): DOMException {
+  return new DOMException("Waveform extraction cancelled.", "AbortError");
+}

src/components/Workbench.tsx

@@ -9,10 +9,16 @@ import {
   compareDocuments,
   convertFrameRate,
   documentSummary,
+  insertCue,
+  mergeCueWithNext,
   parseSubtitle,
+  removeCue,
   replaceCue,
   serializeSubtitle,
+  snapCuesToFrames,
   sortCues,
+  splitCue,
+  transformCueText,
   transformTiming,
   validateDocument,
   type SubtitleDocument,
@@ -223,7 +229,7 @@ export function Workbench() {
           <h1>Subtitle Tools</h1>
           <p>
             Inspect, edit, synchronize, validate, compare, and convert SRT,
-            WebVTT, and ASS captions without uploading media or text.
+            WebVTT, ASS, and TTML captions without uploading media or text.
           </p>
         </div>
         <span className="privacy-pill">No network requests</span>
@@ -252,13 +258,12 @@ export function Workbench() {
         </div>
       </section>
 
-      <nav className="tabs" role="tablist" aria-label="Subtitle workspaces">
+      <nav className="tabs" aria-label="Subtitle workspaces">
         {tabs.map(([value, label]) => (
           <button
             key={value}
             type="button"
-            role="tab"
+            aria-pressed={tab === value}
-            aria-selected={tab === value}
             onClick={() => setTab(value)}
           >
             {label}
@@ -284,7 +289,7 @@ export function Workbench() {
                 Open file
                 <input
                   type="file"
-                  accept=".srt,.vtt,.ass,.ssa,text/plain,text/vtt"
+                  accept=".srt,.vtt,.ass,.ssa,.ttml,.dfxp,.xml,text/plain,text/vtt,application/ttml+xml"
                   onChange={(event) => void open(event.target.files?.[0])}
                 />
               </label>
@@ -302,6 +307,7 @@ export function Workbench() {
                   <option value="srt">SubRip (SRT)</option>
                   <option value="vtt">WebVTT</option>
                   <option value="ass">ASS / SSA</option>
+                  <option value="ttml">TTML / DFXP</option>
                 </select>
               </label>
               <label className="field">
@@ -351,6 +357,7 @@ export function Workbench() {
                 <option value="srt">SubRip (SRT)</option>
                 <option value="vtt">WebVTT</option>
                 <option value="ass">Advanced SubStation Alpha</option>
+                <option value="ttml">TTML</option>
               </select>
             </label>
             {exportFormat !== document.format && (
@@ -378,12 +385,55 @@ export function Workbench() {
                 <p className="eyebrow">Timeline</p>
                 <h2>Cues</h2>
               </div>
-              <button
+              <div className="button-row">
-                type="button"
+                <button
-                onClick={() => setDocument(sortCues(document))}
+                  type="button"
-              >
+                  onClick={() => setDocument(sortCues(document))}
-                Sort by start
+                >
-              </button>
+                  Sort by start
+                </button>
+                <button
+                  type="button"
+                  onClick={() => {
+                    try {
+                      setDocument(insertCue(document, selected + 1));
+                      setSelected(Math.min(selected + 1, document.cues.length));
+                      setError("");
+                    } catch (reason) {
+                      setError(
+                        reason instanceof Error
+                          ? reason.message
+                          : String(reason),
+                      );
+                    }
+                  }}
+                >
+                  Add cue
+                </button>
+              </div>
+            </div>
+            <div className="timeline-strip" aria-label="Editable cue timeline">
+              {document.cues.slice(0, 2_000).map((cue, index) => {
+                const start = summary.firstMs;
+                const span = Math.max(1, summary.lastMs - start);
+                const left = ((cue.startMs - start) / span) * 100;
+                const width = ((cue.endMs - cue.startMs) / span) * 100;
+                return (
+                  <button
+                    type="button"
+                    key={`timeline-${cue.sourceLine}-${index}`}
+                    className={selected === index ? "selected" : ""}
+                    style={{
+                      left: `${Math.max(0, Math.min(100, left))}%`,
+                      width: `${Math.max(0.2, Math.min(100 - left, width))}%`,
+                      top: `${(index % 4) * 1.35 + 0.3}rem`,
+                    }}
+                    title={`Cue ${index + 1}: ${clock(cue.startMs)} to ${clock(cue.endMs)}`}
+                    aria-label={`Select cue ${index + 1} on timeline`}
+                    onClick={() => setSelected(index)}
+                  />
+                );
+              })}
             </div>
             <ol>
               {document.cues.slice(0, 10_000).map((cue, index) => (
@@ -421,6 +471,91 @@ export function Workbench() {
               </div>
               {selectedCue ? (
                 <>
+                  <div className="button-row cue-actions">
+                    <button
+                      type="button"
+                      onClick={() => {
+                        try {
+                          setDocument(
+                            insertCue(document, selected + 1, {
+                              startMs: selectedCue.startMs,
+                              endMs: selectedCue.endMs,
+                              text: selectedCue.text,
+                            }),
+                          );
+                          setSelected(selected + 1);
+                          setError("");
+                        } catch (reason) {
+                          setError(
+                            reason instanceof Error
+                              ? reason.message
+                              : String(reason),
+                          );
+                        }
+                      }}
+                    >
+                      Duplicate
+                    </button>
+                    <button
+                      type="button"
+                      onClick={() => {
+                        try {
+                          setDocument(splitCue(document, selected));
+                          setError("");
+                        } catch (reason) {
+                          setError(
+                            reason instanceof Error
+                              ? reason.message
+                              : String(reason),
+                          );
+                        }
+                      }}
+                    >
+                      Split midpoint
+                    </button>
+                    <button
+                      type="button"
+                      disabled={selected + 1 >= document.cues.length}
+                      onClick={() => {
+                        try {
+                          setDocument(mergeCueWithNext(document, selected));
+                          setError("");
+                        } catch (reason) {
+                          setError(
+                            reason instanceof Error
+                              ? reason.message
+                              : String(reason),
+                          );
+                        }
+                      }}
+                    >
+                      Merge next
+                    </button>
+                    <button
+                      type="button"
+                      onClick={() => {
+                        try {
+                          const next = removeCue(document, selected);
+                          setDocument(next);
+                          setSelected(
+                            Math.max(
+                              0,
+                              Math.min(selected, next.cues.length - 1),
+                            ),
+                          );
+                          setError("");
+                        } catch (reason) {
+                          setError(
+                            reason instanceof Error
+                              ? reason.message
+                              : String(reason),
+                          );
+                        }
+                      }}
+                    >
+                      Delete
+                    </button>
+                  </div>
                   <div className="form-grid">
                     <NumberField
                       label="Start (ms)"
@@ -456,6 +591,31 @@ export function Workbench() {
                       }
                     />
                   </label>
+                  <div
+                    className="button-row cue-actions"
+                    aria-label="Cue formatting actions"
+                  >
+                    {(
+                      [
+                        ["trim", "Trim"],
+                        ["strip-markup", "Strip markup"],
+                        ["upper", "Uppercase"],
+                        ["lower", "Lowercase"],
+                      ] as const
+                    ).map(([transform, label]) => (
+                      <button
+                        key={transform}
+                        type="button"
+                        onClick={() =>
+                          setDocument(
+                            transformCueText(document, transform, [selected]),
+                          )
+                        }
+                      >
+                        {label}
+                      </button>
+                    ))}
+                  </div>
                 </>
               ) : (
                 <p className="empty">No cue selected.</p>
@@ -599,6 +759,21 @@ export function Workbench() {
             <button className="primary" type="button" onClick={applyFrameRate}>
               Convert frame rate
             </button>
+            <button
+              type="button"
+              onClick={() => {
+                try {
+                  setDocument(snapCuesToFrames(document, targetFps));
+                  setError("");
+                } catch (reason) {
+                  setError(
+                    reason instanceof Error ? reason.message : String(reason),
+                  );
+                }
+              }}
+            >
+              Snap cues to target frames
+            </button>
           </article>
         </section>
       )}
@@ -631,7 +806,7 @@ export function Workbench() {
               </div>
             </div>
             <p className="muted">
-              v0.1 compares cue positions deterministically. Insertions can
+              v0.2 compares cue positions deterministically. Insertions can
               shift later matches; no semantic alignment is claimed.
             </p>
             {revisionDocument ? (
@@ -667,7 +842,11 @@ export function Workbench() {
 
       {tab === "waveform" && (
         <section className="panel">
-          <Waveform cues={document.cues} />
+          <Waveform
+            cues={document.cues}
+            selectedIndex={selected}
+            onSelectCue={setSelected}
+          />
         </section>
       )}
 
@@ -676,7 +855,9 @@ export function Workbench() {
           Parsing and media decoding stay local. Validation is configurable
           guidance, not a broadcaster, accessibility, or legal compliance
           verdict. ASS round trips retain parsed dialogue fields; cross-format
-          exports explicitly discard unsupported styling.
+          exports explicitly discard unsupported styling. TTML support is a
+          bounded flat cue profile; inherited timing/layout and external
+          resources are not interpreted.
         </p>
       </section>
     </main>

src/media/peaks.ts

@@ -0,0 +1,25 @@
+export const DEFAULT_PEAK_COUNT = 2_000;
+
+/** Collapse PCM samples into deterministic absolute-amplitude buckets. */
+export function extractPeaks(
+  samples: Float32Array,
+  requestedCount = DEFAULT_PEAK_COUNT,
+): Float32Array {
+  if (!Number.isSafeInteger(requestedCount) || requestedCount < 1)
+    throw new RangeError("Peak count must be a positive whole number.");
+  if (samples.length === 0) return new Float32Array();
+  const count = Math.min(requestedCount, samples.length);
+  const peaks = new Float32Array(count);
+  for (let bucket = 0; bucket < count; bucket += 1) {
+    const start = Math.floor((bucket * samples.length) / count);
+    const end = Math.max(
+      start + 1,
+      Math.floor(((bucket + 1) * samples.length) / count),
+    );
+    let peak = 0;
+    for (let index = start; index < end; index += 1)
+      peak = Math.max(peak, Math.abs(samples[index] ?? 0));
+    peaks[bucket] = peak;
+  }
+  return peaks;
+}

src/media/peaks.worker.ts

@@ -0,0 +1,28 @@
+/// <reference lib="webworker" />
+
+import { extractPeaks } from "./peaks";
+
+interface PeakRequest {
+  id: number;
+  samples: ArrayBuffer;
+  length: number;
+  count: number;
+}
+
+declare const self: DedicatedWorkerGlobalScope;
+
+self.onmessage = (event: MessageEvent<PeakRequest>) => {
+  const { id, samples, length, count } = event.data;
+  try {
+    const peaks = extractPeaks(new Float32Array(samples, 0, length), count);
+    self.postMessage({ id, peaks: peaks.buffer }, [peaks.buffer]);
+  } catch (reason) {
+    self.postMessage({
+      id,
+      error:
+        reason instanceof Error ? reason.message : "Peak extraction failed.",
+    });
+  }
+};
+
+export {};

src/styles.css

@@ -22,6 +22,8 @@
   --wave-bg: #eeedf7;
   --wave-line: #5b4ec4;
   --cue-line: #ce3d59;
+  --cue-selected: rgb(91 78 196 / 18%);
+  --playhead: #171522;
 }
 
 :root[data-toolbox-theme="dark"] {
@@ -39,6 +41,8 @@
   --wave-bg: #292634;
   --wave-line: #aa9cff;
   --cue-line: #ff8195;
+  --cue-selected: rgb(169 156 255 / 24%);
+  --playhead: #fff;
 }
 
 @media (prefers-color-scheme: dark) {
@@ -57,6 +61,8 @@
     --wave-bg: #292634;
     --wave-line: #aa9cff;
     --cue-line: #ff8195;
+    --cue-selected: rgb(169 156 255 / 24%);
+    --playhead: #fff;
   }
 }
 
@@ -237,7 +243,7 @@ h2 {
   white-space: nowrap;
 }
 
-.tabs button[aria-selected="true"] {
+.tabs button[aria-pressed="true"] {
   border-color: var(--accent);
   background: var(--surface-muted);
   color: var(--accent-dark);
@@ -364,6 +370,51 @@ h2 {
   margin-top: 0.2rem;
 }
 
+.button-row,
+.waveform-navigation {
+  display: flex;
+  flex-wrap: wrap;
+  align-items: center;
+  gap: 0.45rem;
+}
+
+.cue-actions {
+  margin-bottom: 0.75rem;
+}
+
+.timeline-strip {
+  position: relative;
+  height: 5.9rem;
+  overflow: hidden;
+  margin-bottom: 0.75rem;
+  border: 1px solid var(--line);
+  border-radius: 0.72rem;
+  background:
+    linear-gradient(
+        90deg,
+        transparent 24.8%,
+        var(--line) 25%,
+        transparent 25.2%
+      )
+      0 0 / 25% 100%,
+    var(--surface-muted);
+}
+
+.timeline-strip button {
+  position: absolute;
+  min-width: 0.2rem;
+  min-height: 1rem;
+  border-radius: 0.25rem;
+  padding: 0;
+  background: color-mix(in srgb, var(--accent) 55%, var(--surface));
+}
+
+.timeline-strip button.selected {
+  z-index: 1;
+  border-color: var(--danger);
+  background: var(--accent);
+}
+
 .cue-list {
   max-height: 52rem;
   overflow: auto;
@@ -469,7 +520,23 @@ h2 {
   margin-bottom: 0.7rem;
 }
 
+.waveform-navigation {
+  margin: 0.65rem 0;
+}
+
+.waveform-navigation label {
+  display: flex;
+  align-items: center;
+  gap: 0.4rem;
+}
+
+.waveform-scroll {
+  max-width: 100%;
+  overflow-x: auto;
+}
+
 .waveform {
+  min-width: 100%;
   height: 180px;
   border: 1px solid var(--line);
   border-radius: 0.75rem;

src/subtitle/model.ts

@@ -1,4 +1,4 @@
-export type SubtitleFormat = "srt" | "vtt" | "ass";
+export type SubtitleFormat = "srt" | "vtt" | "ass" | "ttml";
 
 export interface Cue {
   id: string;
@@ -7,6 +7,7 @@ export interface Cue {
   text: string;
   settings?: string;
   assFields?: Record<string, string>;
+  ttmlAttributes?: Record<string, string>;
   sourceLine: number;
 }
 
@@ -58,6 +59,7 @@ export function detectFormat(source: string): SubtitleFormat {
   const head = source.replace(/^\uFEFF/u, "").slice(0, 16_384);
   if (/^WEBVTT(?:[ \t]|$)/mu.test(head)) return "vtt";
   if (/^\s*\[(?:Script Info|Events|V4\+? Styles)\]/imu.test(head)) return "ass";
+  if (/^\s*<\?xml[\s\S]*?<tt\b|^\s*<tt\b/iu.test(head)) return "ttml";
   return "srt";
 }
 
@@ -280,6 +282,139 @@ function parseAss(source: string): SubtitleDocument {
   return { format: "ass", cues, preamble, assFormat: format, warnings };
 }
 
+function parseTtmlTime(value: string, frameRate: number): number {
+  const clock = /^(\d{1,6}):(\d{2}):(\d{2})(?:[.](\d{1,3})|:(\d{1,4}))?$/u.exec(
+    value.trim(),
+  );
+  if (clock) {
+    const hours = Number(clock[1]),
+      minutes = Number(clock[2]),
+      seconds = Number(clock[3]);
+    if (minutes > 59 || seconds > 59)
+      throw new Error(
+        `TTML timestamp component is outside its range: ${value}`,
+      );
+    const fraction = clock[4]
+      ? Number(clock[4]!.padEnd(3, "0"))
+      : clock[5]
+        ? Math.round((Number(clock[5]) / frameRate) * 1000)
+        : 0;
+    const result = ((hours * 60 + minutes) * 60 + seconds) * 1000 + fraction;
+    if (!Number.isSafeInteger(result))
+      throw new Error("Timestamp is too large.");
+    return result;
+  }
+  const offset = /^(-?(?:\d+(?:\.\d+)?|\.\d+))(h|m|s|ms|f)$/u.exec(
+    value.trim(),
+  );
+  if (!offset) throw new Error(`Invalid TTML time expression: ${value}`);
+  const amount = Number(offset[1]),
+    multiplier =
+      offset[2] === "h"
+        ? 3_600_000
+        : offset[2] === "m"
+          ? 60_000
+          : offset[2] === "s"
+            ? 1000
+            : offset[2] === "f"
+              ? 1000 / frameRate
+              : 1,
+    result = Math.round(amount * multiplier);
+  if (!Number.isSafeInteger(result)) throw new Error("Timestamp is too large.");
+  return result;
+}
+
+function ttmlCueText(node: Element): string {
+  const visit = (current: Node): string => {
+    if (current.nodeType === 3 || current.nodeType === 4)
+      return current.nodeValue ?? "";
+    if (current.nodeType !== 1) return "";
+    const element = current as Element;
+    if (element.localName.toLowerCase() === "br") return "\n";
+    return [...element.childNodes].map((child) => visit(child)).join("");
+  };
+  return [...node.childNodes]
+    .map((child) => visit(child))
+    .join("")
+    .replace(/[ \t]+/gu, " ")
+    .replace(/ *\n */gu, "\n")
+    .trim();
+}
+
+function parseTtml(source: string): SubtitleDocument {
+  if (/<!DOCTYPE|<!ENTITY/iu.test(source))
+    throw new Error("TTML document types and entities are not supported.");
+  const xml = new DOMParser().parseFromString(source, "application/xml");
+  const parserError = xml.getElementsByTagName("parsererror")[0];
+  if (parserError) throw new Error("TTML is not well-formed XML.");
+  if (xml.documentElement.localName.toLowerCase() !== "tt")
+    throw new Error("TTML root element must be <tt>.");
+  const frameRateText =
+      xml.documentElement.getAttribute("ttp:frameRate") ??
+      [...xml.documentElement.attributes].find(
+        (attribute) => attribute.localName === "frameRate",
+      )?.value,
+    frameRate = frameRateText ? Number(frameRateText) : 30;
+  if (!Number.isFinite(frameRate) || frameRate <= 0 || frameRate > 1000)
+    throw new Error("TTML frameRate must be in (0, 1000].");
+  const cues: Cue[] = [],
+    warnings: string[] = [];
+  const paragraphs = [...xml.getElementsByTagNameNS("*", "p")];
+  for (const [index, paragraph] of paragraphs.entries()) {
+    try {
+      const begin = paragraph.getAttribute("begin");
+      if (!begin) throw new Error("cue has no begin time");
+      const startMs = parseTtmlTime(begin, frameRate),
+        end = paragraph.getAttribute("end"),
+        duration = paragraph.getAttribute("dur"),
+        endMs = end
+          ? parseTtmlTime(end, frameRate)
+          : duration
+            ? startMs + parseTtmlTime(duration, frameRate)
+            : Number.NaN;
+      if (!Number.isSafeInteger(endMs))
+        throw new Error("cue has no end/dur time");
+      const attributes = Object.fromEntries(
+        [...paragraph.attributes]
+          .filter(
+            (attribute) =>
+              !["begin", "end", "dur"].includes(attribute.localName) &&
+              attribute.name.length <= 128 &&
+              attribute.value.length <= 4_096,
+          )
+          .slice(0, 32)
+          .map((attribute) => [attribute.name, attribute.value]),
+      );
+      cues.push({
+        id:
+          paragraph.getAttribute("xml:id") ??
+          paragraph.getAttribute("id") ??
+          String(index + 1),
+        startMs,
+        endMs,
+        text: ttmlCueText(paragraph),
+        ttmlAttributes: attributes,
+        sourceLine: index + 1,
+      });
+    } catch (reason) {
+      warnings.push(
+        `Ignored TTML cue ${index + 1}: ${reason instanceof Error ? reason.message : "invalid timing"}.`,
+      );
+    }
+    if (cues.length > MAX_CUES)
+      throw new Error("Subtitle exceeds 100,000 cues.");
+  }
+  return {
+    format: "ttml",
+    cues,
+    preamble: [],
+    warnings: [
+      "TTML styling, regions and inherited timing are inspected only at cue-reference level; export uses a safe flat TTML profile.",
+      ...warnings,
+    ],
+  };
+}
+
 export function parseSubtitle(
   source: string,
   requested: SubtitleFormat | "auto" = "auto",
@@ -291,7 +426,9 @@ export function parseSubtitle(
       ? parseVtt(normalized)
       : format === "ass"
         ? parseAss(normalized)
-        : parseSrt(normalized);
+        : format === "ttml"
+          ? parseTtml(normalized)
+          : parseSrt(normalized);
   if (!document.cues.length)
     document.warnings.push("No valid subtitle cues were found.");
   return document;
@@ -518,6 +655,172 @@ export function replaceCue(
   return cloneDocument(document, cues);
 }
 
+export function insertCue(
+  document: SubtitleDocument,
+  index: number,
+  cue?: Partial<Pick<Cue, "startMs" | "endMs" | "text">>,
+): SubtitleDocument {
+  if (!Number.isSafeInteger(index) || index < 0 || index > document.cues.length)
+    throw new Error("Cue insertion index is outside the document.");
+  if (document.cues.length >= MAX_CUES)
+    throw new Error("Subtitle exceeds 100,000 cues.");
+  const previous = document.cues[index - 1],
+    next = document.cues[index],
+    startMs =
+      cue?.startMs ??
+      (previous
+        ? previous.endMs + 1
+        : next
+          ? Math.max(0, next.startMs - 2_000)
+          : 0),
+    endMs =
+      cue?.endMs ?? Math.max(startMs + 1_000, next?.startMs ?? startMs + 2_000);
+  if (
+    ![startMs, endMs].every(Number.isSafeInteger) ||
+    startMs < 0 ||
+    endMs <= startMs
+  )
+    throw new Error(
+      "Inserted cue requires safe, non-negative increasing times.",
+    );
+  const cues = [...document.cues];
+  cues.splice(index, 0, {
+    id: `cue-${index + 1}`,
+    startMs,
+    endMs,
+    text: cue?.text ?? "",
+    sourceLine: 0,
+  });
+  return cloneDocument(document, cues);
+}
+
+export function removeCue(
+  document: SubtitleDocument,
+  index: number,
+): SubtitleDocument {
+  if (
+    !Number.isSafeInteger(index) ||
+    index < 0 ||
+    index >= document.cues.length
+  )
+    throw new Error("Cue index is outside the document.");
+  return cloneDocument(
+    document,
+    document.cues.filter((_, cueIndex) => cueIndex !== index),
+  );
+}
+
+export function splitCue(
+  document: SubtitleDocument,
+  index: number,
+  atMs?: number,
+): SubtitleDocument {
+  const cue = document.cues[index];
+  if (!cue) throw new Error("Cue index is outside the document.");
+  if (document.cues.length >= MAX_CUES)
+    throw new Error("Subtitle exceeds 100,000 cues.");
+  const splitAt = atMs ?? Math.round((cue.startMs + cue.endMs) / 2);
+  if (
+    !Number.isSafeInteger(splitAt) ||
+    splitAt <= cue.startMs ||
+    splitAt >= cue.endMs
+  )
+    throw new Error("Split time must be strictly inside the cue.");
+  const parts = splitText(cue.text),
+    cues = [...document.cues];
+  cues.splice(
+    index,
+    1,
+    { ...cue, endMs: splitAt, text: parts[0] },
+    {
+      ...cue,
+      id: `${cue.id || index + 1}-b`,
+      startMs: splitAt,
+      text: parts[1],
+      sourceLine: 0,
+    },
+  );
+  return cloneDocument(document, cues);
+}
+
+export function mergeCueWithNext(
+  document: SubtitleDocument,
+  index: number,
+): SubtitleDocument {
+  const cue = document.cues[index],
+    next = document.cues[index + 1];
+  if (!cue || !next) throw new Error("A following cue is required to merge.");
+  const cues = [...document.cues];
+  cues.splice(index, 2, {
+    ...cue,
+    endMs: Math.max(cue.endMs, next.endMs),
+    text: [cue.text.trim(), next.text.trim()].filter(Boolean).join("\n"),
+  });
+  return cloneDocument(document, cues);
+}
+
+export type CueTextTransform = "trim" | "strip-markup" | "upper" | "lower";
+export function transformCueText(
+  document: SubtitleDocument,
+  transform: CueTextTransform,
+  indices?: readonly number[],
+): SubtitleDocument {
+  const selected = indices ? new Set(indices) : undefined;
+  const cues = document.cues.map((cue, index) => {
+    if (selected && !selected.has(index)) return cue;
+    const text =
+      transform === "trim"
+        ? cue.text
+            .split("\n")
+            .map((line) => line.trim())
+            .join("\n")
+            .trim()
+        : transform === "strip-markup"
+          ? plainText(cue.text)
+          : transform === "upper"
+            ? cue.text.toLocaleUpperCase()
+            : cue.text.toLocaleLowerCase();
+    return { ...cue, text };
+  });
+  return cloneDocument(document, cues);
+}
+
+export function snapCuesToFrames(
+  document: SubtitleDocument,
+  framesPerSecond: number,
+): SubtitleDocument {
+  if (
+    !Number.isFinite(framesPerSecond) ||
+    framesPerSecond <= 0 ||
+    framesPerSecond > 1000
+  )
+    throw new Error("Frame rate must be in (0, 1000].");
+  const frameMs = 1000 / framesPerSecond;
+  return cloneDocument(
+    document,
+    document.cues.map((cue) => {
+      const startMs = Math.max(0, Math.round(cue.startMs / frameMs) * frameMs),
+        endMs = Math.max(
+          startMs + 1,
+          Math.round(cue.endMs / frameMs) * frameMs,
+        );
+      return { ...cue, startMs: Math.round(startMs), endMs: Math.round(endMs) };
+    }),
+  );
+}
+
+function splitText(value: string): [string, string] {
+  const lines = value.split("\n");
+  if (lines.length > 1) {
+    const middle = Math.ceil(lines.length / 2);
+    return [lines.slice(0, middle).join("\n"), lines.slice(middle).join("\n")];
+  }
+  const words = value.trim().split(/\s+/u);
+  if (words.length < 2) return [value, ""];
+  const middle = Math.ceil(words.length / 2);
+  return [words.slice(0, middle).join(" "), words.slice(middle).join(" ")];
+}
+
 function formatTimestamp(milliseconds: number, separator: "," | "."): string {
   if (!Number.isSafeInteger(milliseconds) || milliseconds < 0)
     throw new Error("Cannot serialize a negative or unsafe timestamp.");
@@ -626,6 +929,26 @@ function serializeAss(document: SubtitleDocument): string {
   return `${preamble.join("\n").replace(/\n+$/u, "")}\n${dialogue.join("\n")}\n`;
 }
 
+function serializeTtml(document: SubtitleDocument): string {
+  const body = document.cues
+    .map((cue) => {
+      const attributes = Object.entries(cue.ttmlAttributes ?? {})
+        .filter(
+          ([name, value]) =>
+            !["begin", "end", "dur", "xml:id", "id"].includes(name) &&
+            /^[A-Za-z_][A-Za-z0-9_.:-]*$/u.test(name) &&
+            value.length <= 4_096,
+        )
+        .slice(0, 32)
+        .map(([name, value]) => ` ${name}="${xml(value)}"`)
+        .join("");
+      const id = cue.id ? ` xml:id="${xmlId(cue.id)}"` : "";
+      return `      <p${id} begin="${formatTimestamp(cue.startMs, ".")}" end="${formatTimestamp(cue.endMs, ".")}"${attributes}>${xml(cue.text).replaceAll("\n", "<br/>")}</p>`;
+    })
+    .join("\n");
+  return `<?xml version="1.0" encoding="UTF-8"?>\n<tt xmlns="http://www.w3.org/ns/ttml">\n  <body>\n    <div>\n${body}\n    </div>\n  </body>\n</tt>\n`;
+}
+
 export function serializeSubtitle(
   document: SubtitleDocument,
   format: SubtitleFormat,
@@ -636,7 +959,23 @@ export function serializeSubtitle(
     ? serializeVtt(document)
     : format === "ass"
       ? serializeAss(document)
-      : serializeSrt(document);
+      : format === "ttml"
+        ? serializeTtml(document)
+        : serializeSrt(document);
+}
+
+function xml(value: string): string {
+  return value
+    .replaceAll("&", "&amp;")
+    .replaceAll("<", "&lt;")
+    .replaceAll(">", "&gt;")
+    .replaceAll('"', "&quot;")
+    .replaceAll("'", "&apos;");
+}
+
+function xmlId(value: string): string {
+  const safe = value.replace(/[^A-Za-z0-9_.-]+/gu, "-").slice(0, 128);
+  return /^[A-Za-z_]/u.test(safe) ? safe : `cue-${safe || "1"}`;
 }
 
 export interface RevisionChange {

src/toolbox/manifest.source.json

@@ -3,12 +3,12 @@
   "schemaVersion": 1,
   "id": "de.add-ideas.subtitle-tools",
   "name": "Subtitle Tools",
-  "version": "0.1.0",
+  "version": "0.2.0",
-  "description": "Edit, validate, synchronize, compare, and convert subtitles locally.",
+  "description": "Edit, navigate, synchronize and convert subtitles locally.",
   "entry": "./",
   "icon": "./favicon.svg",
   "categories": ["media", "text", "productivity"],
-  "tags": ["subtitles", "captions", "srt", "webvtt", "ass", "timing"],
+  "tags": ["subtitles", "captions", "srt", "webvtt", "ass", "ttml", "timing"],
   "integration": {
     "contextVersion": 1,
     "launchModes": ["navigate", "new-tab"],
@@ -21,6 +21,27 @@
     "crossOriginIsolated": false,
     "topLevelContext": false
   },
+  "io": {
+    "accepts": [
+      { "mediaType": "text/plain", "extensions": [".srt", ".ass", ".ssa"] },
+      { "mediaType": "text/vtt", "extensions": [".vtt"] },
+      {
+        "mediaType": "application/ttml+xml",
+        "extensions": [".ttml", ".dfxp", ".xml"]
+      },
+      { "mediaType": "audio/*", "extensions": [] },
+      { "mediaType": "video/*", "extensions": [] }
+    ],
+    "produces": [
+      { "mediaType": "text/plain", "extensions": [".srt", ".ass"] },
+      { "mediaType": "text/vtt", "extensions": [".vtt"] },
+      { "mediaType": "application/ttml+xml", "extensions": [".ttml"] }
+    ]
+  },
+  "capabilities": {
+    "required": [],
+    "optional": ["workers", "web-audio", "media-playback"]
+  },
   "privacy": {
     "processing": "local",
     "fileUploads": true,

src/version.ts

@@ -1 +1 @@
-export const APP_VERSION = "0.1.0";
+export const APP_VERSION = "0.2.0";

tests/browser/app.spec.ts

@@ -1,4 +1,5 @@
 import { expect, test, type Page } from "@playwright/test";
+import { Buffer } from "node:buffer";
 
 const ORIGIN = "http://127.0.0.1:4197";
 async function localOnly(page: Page) {
@@ -36,10 +37,10 @@ test("parses, validates, edits and converts the example", async ({ page }) => {
   const external = await localOnly(page);
   await page.goto("/deep/nested/subtitle/");
   await expect(page.getByText("SRT", { exact: true })).toBeVisible();
-  await page.getByRole("tab", { name: "Cues & checks" }).click();
+  await page.getByRole("button", { name: "Cues & checks" }).click();
   await expect(page.getByText("overlap", { exact: true })).toBeVisible();
   await page.getByLabel("Text").fill("Edited locally");
-  await page.getByRole("tab", { name: "Source & export" }).click();
+  await page.getByRole("button", { name: "Source & export" }).click();
   await page.getByLabel("Output format").selectOption("vtt");
   await expect(page.getByLabel("Export preview")).toHaveValue(/WEBVTT/u);
   await expect(page.getByLabel("Export preview")).toHaveValue(
@@ -50,13 +51,57 @@ test("parses, validates, edits and converts the example", async ({ page }) => {
 
 test("applies a bounded timing shift", async ({ page }) => {
   await page.goto("/deep/nested/subtitle/");
-  await page.getByRole("tab", { name: "Timing" }).click();
+  await page.getByRole("button", { name: "Timing" }).click();
   await page.getByLabel("Shift (ms)").fill("500");
   await page.getByRole("button", { name: "Apply timing transform" }).click();
-  await page.getByRole("tab", { name: "Cues & checks" }).click();
+  await page.getByRole("button", { name: "Cues & checks" }).click();
   await expect(page.getByText(/00:00:01\.500/u).first()).toBeVisible();
 });
 
+test("imports flat TTML and performs timeline edits", async ({ page }) => {
+  await page.goto("/deep/nested/subtitle/");
+  await page
+    .getByLabel("Subtitle source")
+    .fill(
+      `<tt xmlns="http://www.w3.org/ns/ttml"><body><div><p begin="1s" end="3s">One<br/>line</p></div></body></tt>`,
+    );
+  await page.getByRole("button", { name: "Parse source" }).click();
+  await expect(
+    page.getByLabel("Subtitle summary").getByText("TTML", { exact: true }),
+  ).toBeVisible();
+  await page.getByRole("button", { name: "Cues & checks" }).click();
+  await page.getByRole("button", { name: "Duplicate" }).click();
+  await expect(
+    page
+      .getByLabel("Subtitle summary")
+      .locator(":scope > div")
+      .filter({ hasText: /^Cues2$/u })
+      .locator("strong"),
+  ).toHaveText("2");
+  await page.getByRole("button", { name: "Uppercase" }).click();
+  await page.getByRole("button", { name: "Source & export" }).click();
+  await page.getByLabel("Output format").selectOption("ttml");
+  await expect(page.getByLabel("Export preview")).toHaveValue(/<tt/u);
+  await expect(page.getByLabel("Export preview")).toHaveValue(/ONE/u);
+});
+
+test("attaches playback before completing worker waveform extraction", async ({
+  page,
+}) => {
+  await page.goto("/deep/nested/subtitle/");
+  await page.getByRole("button", { name: "Waveform" }).click();
+  await page.getByLabel("Open media").setInputFiles({
+    name: "tone.wav",
+    mimeType: "audio/wav",
+    buffer: wavFixture(),
+  });
+  await expect(page.locator("audio")).toBeVisible();
+  await expect(
+    page.getByLabel("Audio waveform with subtitle start markers"),
+  ).toBeVisible();
+  await expect(page.getByRole("alert")).toHaveCount(0);
+});
+
 test("serves release identity and hardened local-only headers", async ({
   request,
 }) => {
@@ -72,8 +117,32 @@ test("serves release identity and hardened local-only headers", async ({
   const manifest = await request.get("/deep/nested/subtitle/toolbox-app.json");
   await expect(manifest.json()).resolves.toMatchObject({
     id: "de.add-ideas.subtitle-tools",
-    version: "0.1.0",
+    version: "0.2.0",
     entry: "./",
     privacy: { processing: "local", telemetry: false },
   });
 });
+
+function wavFixture(): Buffer {
+  const sampleRate = 8_000;
+  const samples = sampleRate / 4;
+  const output = Buffer.alloc(44 + samples * 2);
+  output.write("RIFF", 0);
+  output.writeUInt32LE(output.length - 8, 4);
+  output.write("WAVEfmt ", 8);
+  output.writeUInt32LE(16, 16);
+  output.writeUInt16LE(1, 20);
+  output.writeUInt16LE(1, 22);
+  output.writeUInt32LE(sampleRate, 24);
+  output.writeUInt32LE(sampleRate * 2, 28);
+  output.writeUInt16LE(2, 32);
+  output.writeUInt16LE(16, 34);
+  output.write("data", 36);
+  output.writeUInt32LE(samples * 2, 40);
+  for (let index = 0; index < samples; index += 1)
+    output.writeInt16LE(
+      Math.round(Math.sin((index / sampleRate) * Math.PI * 2 * 440) * 12_000),
+      44 + index * 2,
+    );
+  return output;
+}

tests/browser/responsive.spec.ts

@@ -0,0 +1,18 @@
+import { expect, test } from "@playwright/test";
+
+test("keeps the primary workspace inside a narrow viewport", async ({
+  page,
+}) => {
+  await page.goto("/deep/nested/subtitle/");
+  await expect(page.locator("main").first()).toBeVisible();
+  await expect(
+    page.locator("main .loading, main .workbench-loading"),
+  ).toHaveCount(0);
+
+  const widths = await page.evaluate(() => ({
+    content: document.documentElement.scrollWidth,
+    viewport: document.documentElement.clientWidth,
+  }));
+  expect(widths.viewport).toBeLessThanOrEqual(430);
+  expect(widths.content).toBeLessThanOrEqual(widths.viewport + 1);
+});

tests/components/app.test.tsx

@@ -13,6 +13,6 @@ describe("Subtitle Tools", () => {
       await screen.findByRole("heading", { name: "Subtitle Tools" }),
     ).toBeVisible();
     expect(await screen.findByText("No network requests")).toBeVisible();
-    expect(screen.getByRole("tab", { name: "Timing" })).toBeVisible();
+    expect(screen.getByRole("button", { name: "Timing" })).toBeVisible();
   });
 });

tests/media/peaks.test.ts

@@ -0,0 +1,15 @@
+import { describe, expect, it } from "vitest";
+import { extractPeaks } from "../../src/media/peaks";
+
+describe("waveform peak extraction", () => {
+  it("covers every sample when bucket sizes are uneven", () => {
+    const peaks = extractPeaks(Float32Array.of(0.1, -0.8, 0.2, 0.4, -1), 2);
+    expect(peaks[0]).toBeCloseTo(0.8);
+    expect(peaks[1]).toBe(1);
+  });
+
+  it("rejects invalid bounds and handles empty PCM", () => {
+    expect(extractPeaks(new Float32Array(), 5)).toHaveLength(0);
+    expect(() => extractPeaks(Float32Array.of(1), 0)).toThrow(/positive/u);
+  });
+});

tests/subtitle/model.test.ts

@@ -2,8 +2,14 @@ import { describe, expect, it } from "vitest";
 import {
   compareDocuments,
   convertFrameRate,
+  insertCue,
+  mergeCueWithNext,
   parseSubtitle,
+  removeCue,
   serializeSubtitle,
+  snapCuesToFrames,
+  splitCue,
+  transformCueText,
   transformTiming,
   validateDocument,
 } from "../../src/subtitle/model";
@@ -85,6 +91,47 @@ describe("subtitle model", () => {
     ]);
   });
 
+  it("imports and exports a bounded flat TTML profile", () => {
+    const source = `<?xml version="1.0"?><tt xmlns="http://www.w3.org/ns/ttml" xmlns:ttp="http://www.w3.org/ns/ttml#parameter" ttp:frameRate="25"><body><div><p xml:id="one" begin="00:00:01.000" end="00:00:02.500" style="caption">Hello<br/>world</p><p begin="75f" dur="1s">Frames</p></div></body></tt>`;
+    const document = parseSubtitle(source);
+    expect(document.format).toBe("ttml");
+    expect(document.cues).toMatchObject([
+      { id: "one", startMs: 1000, endMs: 2500, text: "Hello\nworld" },
+      { startMs: 3000, endMs: 4000, text: "Frames" },
+    ]);
+    const exported = serializeSubtitle(document, "ttml");
+    expect(exported).toContain('xml:id="one"');
+    expect(exported).toContain("Hello<br/>world");
+    expect(parseSubtitle(exported).cues).toHaveLength(2);
+    expect(() =>
+      parseSubtitle(
+        '<!DOCTYPE tt [<!ENTITY x SYSTEM "file:///etc/passwd">]><tt/>',
+        "ttml",
+      ),
+    ).toThrow(/entities/iu);
+  });
+
+  it("edits cue structure, text and frame timing without mutating input", () => {
+    const original = parseSubtitle(SRT);
+    const inserted = insertCue(original, 1, {
+      startMs: 2600,
+      endMs: 3000,
+      text: " New ",
+    });
+    expect(original.cues).toHaveLength(2);
+    expect(inserted.cues).toHaveLength(3);
+    const cleaned = transformCueText(inserted, "trim", [1]);
+    expect(cleaned.cues[1]?.text).toBe("New");
+    const split = splitCue(cleaned, 0, 1500);
+    expect(split.cues).toHaveLength(4);
+    const merged = mergeCueWithNext(split, 0);
+    expect(merged.cues).toHaveLength(3);
+    const removed = removeCue(merged, 1);
+    expect(removed.cues).toHaveLength(2);
+    const snapped = snapCuesToFrames(removed, 25);
+    expect(snapped.cues.every((cue) => cue.startMs % 40 === 0)).toBe(true);
+  });
+
   it("rejects pathological input bounds", () => {
     expect(() => parseSubtitle("x".repeat(4_000_001))).toThrow(/4,000,000/u);
     expect(() =>

tsconfig.app.json

@@ -4,7 +4,7 @@
     "target": "ES2023",
     "lib": ["ES2023", "DOM", "DOM.Iterable"],
     "module": "ESNext",
-    "types": ["vite/client"],
+    "types": ["vite/client", "node"],
     "allowArbitraryExtensions": true,
     "skipLibCheck": true,
     "moduleResolution": "Bundler",