Document MCP protocol migration requirement

[tim-smart]

Summary

• document the required MCP protocol adapter configuration for v3 migrations
• add guidance for the layerHttp and layerStdio stable API IDs
• regenerate the migration reference at the current main SHA

Testing

• pnpm api-diff --write-doc migration/v3-to-v4.md --check
• pnpm lint-fix
• pnpm api-diff --check
• git diff --check

Closes EFF-128

Summary by CodeRabbit

• Documentation
  • Updated v3-to-v4 migration guidance for MCP server APIs.
  • Documented the move to effect/unstable/ai/McpServer.
  • Clarified that MCP server utilities require a non-empty protocol adapter list.
  • Documented the consolidation of layerHttpRouter into layerHttp using the unified HTTP router.
  • Clarified runtime wiring and protocol requirements for MCP server runners.

[changeset-bot]

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Latest commit: 740ad2f

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[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Repository UI

Review profile: CHILL

Plan: Pro Plus

Run ID: ed152f13-7512-4782-971d-1dbc62e61199

📥 Commits

Reviewing files that changed from the base of the PR and between 0a532e5 and 740ad2f.

📒 Files selected for processing (2)

• migration/annotations/effect__ai__McpServer.yaml
• migration/v3-to-v4.md

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📝 Walkthrough

Walkthrough

The MCP server migration annotations and v3-to-v4 guide now reference effect/unstable/ai/McpServer, require non-empty protocols arrays, document layerHttp router consolidation, and clarify RpcServer.Protocol execution.

Changes

MCP migration guidance

Layer / File(s)	Summary
API mappings and migration contract migration/annotations/effect__ai__McpServer.yaml, migration/v3-to-v4.md	MCP server exports now map to effect/unstable/ai/McpServer, require non-empty McpProtocol adapter arrays, and document layerHttpRouter consolidation into layerHttp with the unified HttpRouter. The migration document head identifier was also updated.

Estimated code review effort: 2 (Simple) | ~10 minutes

Possibly related PRs

• Effect-TS/effect#6625: Introduces the MCP server API contract reflected by these migration updates.
• Effect-TS/effect#6663: Also updates v3-to-v4 MCP server migration guidance.

Suggested labels: 4.0

Suggested reviewers: gcanti

🚥 Pre-merge checks | ✅ 2

✅ Passed checks (2 passed)

Check name	Status	Explanation
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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[github-actions]

Bundle Size Analysis

File Name	Current Size	Previous Size	Difference
basic.ts	6.63 KB	6.63 KB	0.00 KB (0.00%)
batching.ts	9.37 KB	9.37 KB	0.00 KB (0.00%)
brand.ts	6.26 KB	6.26 KB	0.00 KB (0.00%)
cache.ts	10.12 KB	10.12 KB	0.00 KB (0.00%)
config.ts	19.21 KB	19.21 KB	0.00 KB (0.00%)
differ.ts	18.42 KB	18.42 KB	0.00 KB (0.00%)
http-client.ts	20.76 KB	20.76 KB	0.00 KB (0.00%)
logger.ts	10.28 KB	10.28 KB	0.00 KB (0.00%)
metric.ts	8.55 KB	8.55 KB	0.00 KB (0.00%)
optic.ts	7.41 KB	7.41 KB	0.00 KB (0.00%)
pubsub.ts	14.20 KB	14.20 KB	0.00 KB (0.00%)
queue.ts	11.08 KB	11.08 KB	0.00 KB (0.00%)
schedule.ts	10.28 KB	10.28 KB	0.00 KB (0.00%)
schema-class.ts	18.16 KB	18.16 KB	0.00 KB (0.00%)
schema-fromJsonSchemaDocument.ts	28.02 KB	28.02 KB	0.00 KB (0.00%)
schema-representation-roundtrip.ts	24.33 KB	24.33 KB	0.00 KB (0.00%)
schema-string-transformation.ts	12.69 KB	12.69 KB	0.00 KB (0.00%)
schema-string.ts	10.35 KB	10.35 KB	0.00 KB (0.00%)
schema-template-literal.ts	14.49 KB	14.49 KB	0.00 KB (0.00%)
schema-toArbitraryLazy.ts	20.93 KB	20.93 KB	0.00 KB (0.00%)
schema-toCodeDocument.ts	23.38 KB	23.38 KB	0.00 KB (0.00%)
schema-toCodecJson.ts	18.32 KB	18.32 KB	0.00 KB (0.00%)
schema-toEquivalence.ts	18.00 KB	18.00 KB	0.00 KB (0.00%)
schema-toFormatter.ts	17.88 KB	17.88 KB	0.00 KB (0.00%)
schema-toJsonSchemaDocument.ts	21.51 KB	21.51 KB	0.00 KB (0.00%)
schema-toRepresentation.ts	18.55 KB	18.55 KB	0.00 KB (0.00%)
schema.ts	17.43 KB	17.43 KB	0.00 KB (0.00%)
stm.ts	12.05 KB	12.05 KB	0.00 KB (0.00%)
stream.ts	9.36 KB	9.36 KB	0.00 KB (0.00%)