diff --git a/docs/CONCEPT.md b/docs/CONCEPT.md
index 7874b0c..39defa1 100644
--- a/docs/CONCEPT.md
+++ b/docs/CONCEPT.md
@@ -25,6 +25,20 @@ Detailed follow-up documents:
 - [OpenProject connector concept](OPENPROJECT_CONNECTOR.md)
 - [OpenDesk integration map](OPENDESK_INTEGRATION_MAP.md)
 
+## Shared runtime boundary
+
+Connector transports use the versioned Core runtime contract for bounded dry
+runs and diagnostics. Connectors owns endpoint discovery, authentication
+hand-off, protocol reads, retry/backoff, and source health. A consuming module
+owns domain mappings and mutations: Addresses, for example, owns contact and
+vCard semantics even when Connectors supplies reusable LDAP, CardDAV, Exchange,
+or Google transport patterns.
+
+Dry runs carry an immutable input hash, source revision and fingerprint,
+redacted effects, diagnostics, truncation state, and an apply token. Apply must
+reject a changed input or source revision. URLs and diagnostics never contain
+credential material; they retain only credential-envelope references.
+
 ## Ownership
 
 The module owns:
diff --git a/src/govoplan_connectors/backend/manifest.py b/src/govoplan_connectors/backend/manifest.py
index d153cfe..319e8c4 100644
--- a/src/govoplan_connectors/backend/manifest.py
+++ b/src/govoplan_connectors/backend/manifest.py
@@ -71,6 +71,7 @@ TABULAR_SOURCE_INTERFACE_VERSION = "0.1.0"
 DATASOURCE_ORIGIN_INTERFACE_VERSION = "0.1.0"
 SANCTIONS_SNAPSHOT_INTERFACE_VERSION = "1.0.0"
 FEED_INTERFACE_VERSION = "0.1.0"
+CONNECTOR_RUNTIME_INTERFACE_VERSION = "1.0.0"
 
 ARCHITECTURE = ModuleArchitectureDeclaration(
     layer="data_reporting_integration",
@@ -358,6 +359,10 @@ manifest = ModuleManifest(
             name="connectors.feeds",
             version=FEED_INTERFACE_VERSION,
         ),
+        ModuleInterfaceProvider(
+            name="connectors.runtime_contract",
+            version=CONNECTOR_RUNTIME_INTERFACE_VERSION,
+        ),
     ),
     permissions=PERMISSIONS,
     role_templates=ROLE_TEMPLATES,
@@ -424,6 +429,22 @@ manifest = ModuleManifest(
             related_modules=("datasources", "dataflow", "ops", "policy", "audit"),
             order=39,
         ),
+        DocumentationTopic(
+            id="connectors.runtime-preview-contract",
+            title="Connector previews and diagnostics",
+            summary="Use one bounded, redacted dry-run shape across external transports.",
+            body=(
+                "Connectors owns endpoint discovery, authentication hand-off, transport limits, retries, and protocol health. "
+                "Domain modules own field mapping, validation, reconciliation, and record mutation. The shared Core runtime "
+                "contract reports redacted effects and diagnostics with source revisions, fingerprints, and immutable input hashes. "
+                "A commit must reject stale, truncated, conflicting, or error-bearing previews, and credentials never appear in URLs or samples."
+            ),
+            layer="available",
+            documentation_types=("admin", "user"),
+            audience=("operator", "module_admin", "power_user"),
+            related_modules=("addresses", "datasources", "dataflow", "policy", "audit"),
+            order=40,
+        ),
         DocumentationTopic(
             id="connectors.tabular-sources",
             title="Governed tabular sources",