[ThomasK33]

Why

The advisor on #315 found two gaps in the RPC error response caps:

1. RpcRequestSchema accepts a request id of any length, and the server echoes the id in every response. So the size invariant that fix: keep the host running when an RPC error response cannot be built #315 added for error responses did not cover the id.
2. sendableMessage cuts a long error message at a fixed index. That index can fall between the two halves of a surrogate pair. Then the message ends with a lone high surrogate.

What changed

• src/protocol/messages.ts: RpcRequestSchema accepts an id of at most MAX_RPC_REQUEST_ID_CHARS (128) characters. sendRpc sends a UUID, which has 36.
• src/host/rpcServer.ts:
  • extractRequestId returns unknown for an id over the cap. So the error response for such a request does not echo the id.
  • The module-load size invariant now counts the id at its cap, at 6 characters per escaped character.
  • sendableMessage steps back one character when the cut would keep a high surrogate without its low surrogate.
• Docs: src/protocol/README.md and src/host/README.md.

Behavior changes for CLI and JSON users

None for the CLI, which always sends a UUID. A raw client that sends an id over 128 characters gets RPC_ERROR with the id unknown. A shortened message never ends with half of an emoji or another character outside the Basic Multilingual Plane.

Verification

• Red first (814ef21), on main 36ff4d1 (fix: keep the host running when an RPC error response cannot be built #315 merged):
  • test/unit/protocol/messages.test.ts: RpcRequestSchema accepts a 129-character id.
  • test/unit/host/rpcServer.test.ts: the server accepts a raw socket request with a 129-character id and echoes that id in its response.
  • A message of a plus 40,000 😀 ends with a lone \ud83d before [message truncated].
• Green (cf826bf, docs 78ac00b): those tests pass. vitest run test/unit: 1956 passed. tsc --noEmit, oxlint src test vitest.config.ts and oxfmt --check pass.

Refs #315

---

Generated with xum • Model: anthropic:claude-opus-5-5 • Thinking: xhigh

[ThomasK33]

@codex review

[chatgpt-codex-connector]

Codex Review Summary

This comment shows the latest Codex review activity on this pull request.

Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-11-04T03:14:20.198389Z	78ac00b	Manual request

ℹ️ About Codex in GitHub

Your team has set up Codex to review pull requests in this repo. Reviews are triggered when you

• Open a pull request for review
• Mark a draft as ready
• Comment "@codex review" or "@codex security review".

Codex reacts with 👀 while any review is running, comments if it has suggestions, and reacts with 👍 once all reviews finish with no findings.

[chatgpt-codex-connector]

Codex Review: Didn't find any major issues. Swish!

Reviewed commit: 78ac00b878

ℹ️ About Codex in GitHub

Your team has set up Codex to review pull requests in this repo. Reviews are triggered when you

• Open a pull request for review
• Mark a draft as ready
• Comment "@codex review".

If Codex has suggestions, it will comment; otherwise it will react with 👍.

Codex can also answer questions or update the PR. Try commenting "@codex address that feedback".