fix(server,web,mobile): thread links reference the thread id, not a baked title

[juliusmarminge]

#16782 had thread tools return a ready link with the thread's title and environment id baked in. The label went stale as soon as a thread was renamed, and agents copied it around as if it were the source of truth.

What changed

Thread links are now [title](t3-thread://v1/<threadId>). The id is the only reference. It resolves in the environment of the message that holds it, the same way the composer's thread references do. The label is just a fallback for a thread the client can't see.

• Server: removed the link field from t3_thread_list, t3_thread_read, and t3_thread_launch. Those tool descriptions and the orchestration instructions now give agents the exact format and say not to URL-encode the id. In a real run without that, the agent invented t3://thread/<encoded id>. Snooze state from feat(server,web,mobile): agents see snooze state and link to threads #16782 is unchanged.
• Web: MarkdownThreadLink keeps feat(server,web,mobile): agents see snooze state and link to threads #16782's project icon, but its label is the thread's live title from the thread shell, so a rename reaches every message that links to it. It opens the thread in the app, and copying it gives back an id link with a sanitized label.
• Mobile: links are relabeled from the environment's live thread titles before rendering, in both markdown renderers. Links inside code spans and fences are left alone. A tap opens the thread in the feed's environment. The title atom only emits when a title changes, so shell updates don't re-render every message.
• Shared: threadLinks drops the environment segment and adds formatThreadLink and relabelThreadLinks. Both clients also accept a percent-encoded id when the id as written names no thread.
• migrate-dev-db: it used to VACUUM INTO a full copy of ~/.t3 before pruning: 68 GB and about 8 minutes on a long-lived install, almost all of it events from deleted, archived, and settled threads. It now attaches the source read-only and copies only visible thread families in one read transaction. Same result, about 10 seconds, no full-size temp file.

Links in the old t3-thread://v1/<environmentId>/<threadId> form have only been on nightly since this morning. They now resolve to no thread and show their old label.

#15975 (Home) imports the old formatThreadLink(thread) signature and will need to update when it rebases.

Made with Claude Opus 5.5 (1M context) in Claude Code, running in T3 Code.

🤖 Generated with Claude Code

[macroscopeapp]

Approvability

Verdict: Not approved

Macroscope's review found this PR not approvable — This PR changes the thread-link protocol and MCP response schemas across server, web, and mobile, while adding live title resolution and a substantial development database-copy path. It also leaves an unresolved concern about whether unavailable thread links should remain navigable.

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[github-actions]

Thread transfer impact

✅ Thread transfer remains within every enforced ceiling.

Provider	Metric	Main baseline	This PR	Impact	PR ceiling
Codex	Total thread wire	5.0 KiB	5.0 KiB	0 B (0.0%)	6.8 KiB	✅
Codex	Thread snapshot wire	3.8 KiB	3.8 KiB	0 B (0.0%)	4.9 KiB	✅
Codex	Live turn WebSocket wire	1.2 KiB	1.2 KiB	0 B (0.0%)	2.0 KiB	✅
Codex	Live turn WebSocket decoded	20.9 KiB	20.9 KiB	0 B (0.0%)	29.3 KiB	✅
Codex	Live turn messages	2	2	0 (0.0%)	8	✅
Claude	Total thread wire	5.0 KiB	5.0 KiB	0 B (0.0%)	6.8 KiB	✅
Claude	Thread snapshot wire	3.8 KiB	3.8 KiB	0 B (0.0%)	4.9 KiB	✅
Claude	Live turn WebSocket wire	1.2 KiB	1.2 KiB	0 B (0.0%)	2.0 KiB	✅
Claude	Live turn WebSocket decoded	21.2 KiB	21.2 KiB	0 B (0.0%)	29.3 KiB	✅
Claude	Live turn messages	2	2	0 (0.0%)	8	✅

Baseline: d720210 · PR result: 156a1a3 · Source CI: success

Scenario and decoded snapshot size

10 historical turns, 5 command tools per turn, 878.9 KiB retained MCP result per historical turn, and a 1.05 MiB retained result in the measured turn.

• Codex decoded thread snapshot: 108.5 KiB
• Claude decoded thread snapshot: 108.8 KiB

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📝 Walkthrough

Walkthrough

Thread links now identify threads by ID and resolve within the environment of the message that contains them. MCP thread list, read, and launch responses no longer include generated links. Mobile and web clients resolve current thread titles. Development database migration copies selected source data before pruning.

Changes

Thread Link Flow

Layer / File(s)	Summary
Thread-link syntax and relabeling packages/shared/src/threadLinks.ts, packages/shared/src/threadLinks.test.ts, apps/server/src/provider/T3OrchestrationInstructions.ts, docs/orchestration-v2/orchestrator-mcp-server.md	Thread-link utilities parse IDs from the ID-only URI, sanitize labels, and update labels from title lookups. Instructions and documentation describe the URI format and resolution in the message environment.
Remove generated links from MCP responses packages/contracts/src/orchestratorMcp.ts, apps/server/src/mcp/OrchestratorMcpService.ts, apps/server/src/mcp/toolkits/project/*, apps/server/src/mcp/toolkits/orchestrator/tools.ts, apps/server/src/mcp/OrchestratorMcpToolkit.integration.test.ts	Thread list, detail, and launch responses no longer include generated links. The schemas, tool descriptions, and tests reflect these changes.
Client thread-link rendering and navigation apps/mobile/src/state/entities.ts, apps/mobile/src/features/threads/ThreadFeed.tsx, apps/mobile/src/lib/nativeMarkdownText.test.ts, apps/web/src/components/ChatMarkdown.tsx, apps/web/src/components/chat/MarkdownThreadLink.tsx	Mobile markdown resolves titles from the current environment and navigates using that environment and the parsed thread ID. Web markdown renders links with the current title or supplied label.

Development Database Migration

Layer / File(s)	Summary
Copy and verify the filtered source slice apps/server/scripts/migrate-dev-db.ts, apps/server/scripts/migrate-dev-db.test.ts	The migration copies schema and selected rows from a read-only source, excluding invisible thread families and cleared tables. Tests check that settled-thread rows are excluded, the event sequence is preserved, and migration 55 runs from a source initialized through migration 54.

Priority: ➖ Normal

Estimated code review effort: 4 (Complex) | ~60 minutes

Change: Bug fix

Sequence Diagram(s)

sequenceDiagram
  participant ThreadFeed
  participant useLiveThreadLinkLabels
  participant ThreadTitleAtom as Environment-scoped thread-title atom
  participant relabelThreadLinks
  ThreadFeed->>useLiveThreadLinkLabels: Provide markdown and environment ID
  useLiveThreadLinkLabels->>ThreadTitleAtom: Read titles when markdown contains thread links
  ThreadTitleAtom-->>useLiveThreadLinkLabels: Return titles for the environment
  useLiveThreadLinkLabels->>relabelThreadLinks: Resolve link labels from current titles
  relabelThreadLinks-->>useLiveThreadLinkLabels: Return relabeled markdown
  useLiveThreadLinkLabels-->>ThreadFeed: Return markdown for rendering

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Suggested reviewers: t3dotgg

Merge Risk: ⚪ Minimal · up to 156a1

No actionable merge-blocking risk remains from the assessed thread-link or database-copy behavior.

🚥 Pre-merge checks | ✅ 3 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Description check	⚠️ Warning	The description clearly explains the problem and the main changes across server, web, mobile, shared code, and migration handling. However, it omits the required Scope and approval section and does no…	Add a Scope and approval section with the relevant issue or explicit maintainer approval, or explain why this focused fix qualifies for an exemption. Add a Verification section with the focused tests or manual checks performed, observed res…

✅ Passed checks (3 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and concisely describes the main change: thread links now reference the thread ID instead of a baked title. It is specific and covers the affected server, web, and mobile areas.
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.

Full details: Description check

Explanation

The description clearly explains the problem and the main changes across server, web, mobile, shared code, and migration handling. However, it omits the required Scope and approval section and does not provide focused verification results or state what could not be checked.

Resolution

Add a Scope and approval section with the relevant issue or explicit maintainer approval, or explain why this focused fix qualifies for an exemption. Add a Verification section with the focused tests or manual checks performed, observed results, and any checks that were not run.

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Inline comments:
Review comments at @apps/web/src/components/ChatMarkdown.tsx:
- Line 3181: Update the ThreadContextChip copyMarkdown value to use the chip’s
resolved title, shell.title, while preserving the existing title as the fallback
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• apps/server/src/mcp/toolkits/project/handlers.test.ts
• apps/server/src/mcp/toolkits/project/handlers.ts
• apps/server/src/mcp/toolkits/project/tools.ts
• apps/server/src/provider/T3OrchestrationInstructions.ts
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• apps/web/src/components/chat/MarkdownThreadLink.tsx
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• packages/contracts/src/orchestratorMcp.ts
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Review comments at @packages/shared/src/threadLinks.ts:
- Around line 66-67: Update the thread ID resolution loop around title(threadId)
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only try the decoded ID when the written ID’s title is undefined, and retain the
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