docs(ai): note handoff coverage for new providers

AGENTS.md

@@ -106,7 +106,9 @@ Create provider file exporting:
 - Map to standardized `Model` interface
 
 ### 5. Tests (`packages/ai/test/`)
-Add provider to: `stream.test.ts`, `tokens.test.ts`, `abort.test.ts`, `empty.test.ts`, `context-overflow.test.ts`, `image-limits.test.ts`, `unicode-surrogate.test.ts`, `tool-call-without-result.test.ts`, `image-tool-result.test.ts`, `total-tokens.test.ts`
+Add provider to: `stream.test.ts`, `tokens.test.ts`, `abort.test.ts`, `empty.test.ts`, `context-overflow.test.ts`, `image-limits.test.ts`, `unicode-surrogate.test.ts`, `tool-call-without-result.test.ts`, `image-tool-result.test.ts`, `total-tokens.test.ts`, `cross-provider-handoff.test.ts`.
+
+For `cross-provider-handoff.test.ts`, add at least one provider/model pair. If the provider exposes multiple model families (for example GPT and Claude), add at least one pair per family.
 
 For non-standard auth, create utility (e.g., `bedrock-utils.ts`) with credential detection.
 

packages/ai/README.md

@@ -1100,6 +1100,9 @@ Create or update test files to cover the new provider:
 - `tool-call-without-result.test.ts` - Orphaned tool calls
 - `image-tool-result.test.ts` - Images in tool results
 - `total-tokens.test.ts` - Token counting accuracy
+- `cross-provider-handoff.test.ts` - Cross-provider context replay
+
+For `cross-provider-handoff.test.ts`, add at least one provider/model pair. If the provider exposes multiple model families (for example GPT and Claude), add at least one pair per family.
 
 For providers with non-standard auth (AWS, Google Vertex), create a utility like `bedrock-utils.ts` with credential detection helpers.