[saphid]

Problem

When an agent calls create_threads with a prompt and no title, the server makes a default title from the prompt. It cuts the prompt to 77 UTF-16 units and adds .... If an emoji (or another character outside the BMP) sits across units 76–77, the cut keeps only half of it. SQLite stores the leftover lone surrogate as U+FFFD, so the thread shows up as …aaa�... on every client, and the broken character can't be undone.

Long agent prompts with emoji are common, so anyone whose agent fans out threads can hit this.

Change

threadTitle in apps/server/src/mcp/OrchestratorMcpService.ts now moves the cut back one unit when it would land between a high and a low surrogate. This uses the same check, limits, and ... suffix as sanitizeThreadTitle (#27483). Titles that don't end in a split character are unchanged.

Scope and approval

Very small, focused fix for an obvious bug, so no prior issue: it changes one expression in one function, and merged PRs #27273, #27483, #27497, and #27841 fixed the same kind of bug in other places.

Overlap search: #28831 (open) fixes the same kind of cut in scheduleTask's default title in this file. Its diff touches only that code and the scheduled-task tests, not threadTitle, so the two PRs don't conflict. If maintainers would rather land both fixes together, that's fine. #27483 fixed only provider-core sanitizeThreadTitle. #24611 (open) changes only the shared truncate helper, which isn't used here. A search for "create_threads title" found no other PRs.

Verification

• Red on main: I added one more createThreads call with an emoji at the cut, plus a title assertion, to the existing case "replays accepted creation on the $name without authorizing new disabled work". Both parameterized rows fail:
  Expected: "aaaa…aaaa..." / Received: "aaaa…aaaa�..."
• Green: vp test run src/mcp/OrchestratorMcpService.test.ts: 57 passed (57).
• vp run check:changed: format, lint, knip, graphql, typecheck (3 packages), tests (62) all pass.
• Not checked: a live dev server run. The test reads the title back from the SQLite-backed projection, which is where the U+FFFD showed up.

Reviewed with sol-loop: 1 round with GPT-6.1 Sol on high. Sol verdict: approved, no actionable findings.

Created with Claude Opus 5.5 in Claude Code (T3 Code).

🤖 Generated with Claude Code

[macroscopeapp]

Approvability

Verdict: Approved at 0a67f22

Macroscope's review found this PR approvable — This change prevents truncated MCP thread titles from ending with half of a Unicode character. Its impact is confined to title formatting for newly created threads, with existing defaults and execution behavior unchanged.

^{You can add or adjust custom eligibility rules. Learn more.}

[coderabbitai]

No actionable comments were generated in the recent review.

Recent review info

Run configuration

• Source mode: Auto
• Repository: pingdotgg/t3code
• Branch: main
• File: .coderabbit.config.ts
• Commit: d01b92c
• Layers: Repository TS config
• Review profile: CHILL
• Plan: Advanced
• Run ID: 768f3e57-2230-4382-8191-5774bc922a33

Commits

Reviewing files that changed from the base of the PR and between d01b92c and 0a67f22.

Files selected for processing: 2

• apps/server/src/mcp/OrchestratorMcpService.test.ts
• apps/server/src/mcp/OrchestratorMcpService.ts

Included review availability: This review used your included allowance. Your plan provides up to 10 included reviews per hour; 6 remain after this review.

Walkthrough

Thread title truncation now avoids splitting a UTF-16 surrogate pair before appending an ellipsis. A thread-creation test checks the title when an emoji occurs at the truncation boundary.

Changes: Thread title truncation

Layer / File(s)	Summary
Unicode-safe title truncation apps/server/src/mcp/OrchestratorMcpService.ts, apps/server/src/mcp/OrchestratorMcpService.test.ts	threadTitle moves the cut point back one code unit when it would split a surrogate pair. A test checks the title for a prompt with an emoji at the boundary.

Estimated code review effort: 2 (Simple) | ~5 minutes

Change: Bug fix

Suggested labels: bugfix, size:XS

Suggested reviewers: juliusmarminge, macroscopeapp

Merge Risk: Minimal · up to 0a67f

The Unicode-safe title truncation fix is ready to merge.

Pre-merge checks: 4

Check name	Status	Explanation
Title check		The title "fix(server): create_threads titles no longer end in a broken character" matches the main change. The PR changes the default title truncation in threadTitle so it no longer splits a UTF-16 s…
Description check		The description follows the repository template. It has a Problem section that explains the surrogate-pair truncation bug, its effect on SQLite storage, and reproduction context. The Change section ex…
Linked Issues check		Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check		Check skipped because no linked issues were found for this pull request.

Full details: Title check

Explanation

The title "fix(server): create_threads titles no longer end in a broken character" matches the main change. The PR changes the default title truncation in threadTitle so it no longer splits a UTF-16 surrogate pair, which would otherwise store U+FFFD. The title is a conventional commit, specific, and under 72 characters.

Full details: Description check

Explanation

The description follows the repository template. It has a Problem section that explains the surrogate-pair truncation bug, its effect on SQLite storage, and reproduction context. The Change section explains the fix in threadTitle and its reuse of the sanitizeThreadTitle check. The Scope and approval section explains why no prior issue is needed for this small fix and lists overlapping open PRs. The Verification section gives the red test before the fix, the green test run, the check:changed results, and what was not checked. The model and harness line is present at the end.

Finishing Touches

Generate unit tests (beta)

• Create a new PR

• Autofix · Keep fixing CodeRabbit findings and required CI, and resolving merge conflicts

[maria-rcks]

Note

Written by gpt-6.1-sol on behalf of Maria

Verified in a real dev environment

verified unchanged head 0a67f227e14bfb980730dae659df438e0127f81f on linux using the repository's playwright and /usr/bin/google-chrome, with real codex gpt-6.1-sol turns through the local proxy. a real git project was added through the web app. no mock provider or fixture data was used for this scenario.

on github/main (84537c4dd9), a parent agent called create_threads with no title and a prompt beginning with 76 a characters followed by 😀. the child title contained a replacement character; read-only sqlite inspection confirmed UTF-8 EFBFBD before .... the parent also received Deserialize error: unexpected end of hex escape, although the children ran.

on this pr, the same flow returned successfully to the parent. the title was exactly 76 a characters plus ..., and the child completed with CHILD_OK. a full browser reload preserved the title and reply. neighboring cases passed: an explicit Explicit title 😀 and a short prompt-derived title remained intact, and their real child turns returned EXPLICIT_OK and SHORT_OK.

short server transcript:

$ timeout 30 node apps/server/src/bin.ts thread list --base-dir /home/user/t3code/.t3 --project /home/user/title-verification --json
boundary title: 76 a characters + ... | completed | codex/gpt-6.1-sol
explicit title: Explicit title 😀    | completed | codex/gpt-6.1-sol
short title: Reply with exactly SHORT_OK. Do not call tools.
                                      completed | codex/gpt-6.1-sol
$ timeout 30 node apps/server/src/bin.ts thread show --base-dir /home/user/t3code/.t3 <boundary-thread-id> --json
assistant: CHILD_OK

vp run check:changed d01b92c0613936e5204ea2787a9ed6bf7d1ff547 passed through blacksmith-check: format, lint, knip, graphql, typechecks for three packages, and 62 tests. the explicit base was needed because the worker checkout was shallow. all 31 reported pr checks were successful. no source changes were needed.

full runtime transcript

before, main:

after, pr:

Not verified

native ios/android, electron desktop, macos/windows, other providers, and relay/tunnel connections were not exercised. this pass verified the linux web client and the codex provider path. the recording shows completed child threads and navigation, not the original turn streaming.