feat(server): count which T3 MCP tools agents use

[juliusmarminge]

We have no data on which T3 MCP tools agents call, whether those calls work, or how agents hand work to each other (for example a GPT model delegating to Claude, and whether that delegation succeeds).

This adds two anonymous PostHog events.

mcp.tool.invoked: one per T3 MCP tool call

Emitted from a single wrapper around tool registration in McpHttpServer.ts, so it covers every toolkit plus the hand-registered image tools.

Property	When
tool, callerProvider, outcome (ok/error), errorCode, durationMs	every call
callerModel, callerOrigin (user/agent/system/scheduler), callerDepth (0 = top level, capped at 5)	handoff tools
targetProvider, targetModel, targetRuntimeMode, targetInteractionMode, crossProvider	handoff tools, one event per receiving thread
targetChosen, mode, waitTimedOut, delivery, workspace, batchSize, bindToCurrentThread	handoff tools, where the tool has that setting

• Handoff tools: delegate_task, create_threads, t3_thread_launch, t3_thread_send, t3_thread_send_attachments, t3_thread_fork, t3_thread_merge_back, t3_queue_edit, t3_queue_promote_to_steer, t3_pending_request_respond, schedule_task, run_scheduled_task_now.
• Receiving threads are read from the tool result (childThreadId, targetThreadId, boundThreadId, threadId, or each entry of threads). A create_threads batch across two providers therefore emits two events. t3_queue_edit, t3_queue_promote_to_steer and t3_pending_request_respond return only a sequence, so they take the target from the input threadId, and only after the call succeeded.
• crossProvider is sent only when both providers resolve. If either side is unknown (a removed instance, for example), it's left out.
• errorCode is the closed OrchestratorMcpFailure.code (or the preview/device error tag). T3 tool failures don't always set isError, so the outcome is read from the result.
• targetChosen tells whether the agent picked the target explicitly or inherited the parent's.
• callerOrigin: scheduler comes from the run's starting message, because scheduled runs keep the task creator's provenance.
• Non-handoff tools don't look up any threads.

mcp.delegated_task.finished: one per app-owned delegated task

A small DelegatedTaskAnalytics service listens to subagent.updated domain events. When a task reaches completed, failed, cancelled or interrupted, it records the status, parent and child provider and model, crossProvider, completionWake, and durationSeconds.

Anonymity

• Driver kinds only (codex, claudeAgent, …). Instance ids are user-named, so they're never sent.
• A model is sent only when it's a non-custom entry from a vendor catalog (Codex, Claude, Cursor, Grok, Antigravity). OpenCode, Pi and ACP models come from user configuration, so they're dropped.
• Settings come only from closed enums, booleans and counts. Rejected calls are recorded with their raw input, so input strings (mode, workspaceStrategy.type) are sent only when they match a schema literal. No ids, prompts, titles, arguments or results are sent. Thread ids are only used for lookups on the server, which is also why there's no per-thread call sequence.
• T3CODE_TELEMETRY_ENABLED=false still disables everything. docs/internals/product-analytics.md states the rule.

Tests

• A registration test runs a real t3_thread_fork from a Codex subagent into a Claude thread, checks the full event, and asserts that no id leaks into it. It also runs t3_queue_edit on another thread and checks the target dimensions.
• ProviderDimensions.test.ts covers batching, crossProvider with an unresolved side, dropping input strings outside the schema literals, non-handoff tools, the anonymization rules, handoff settings, failure codes without isError, and origin.
• DelegatedTaskAnalytics.test.ts covers final-status filtering, dedup and dimensions.
• The existing MCP and server suites still pass.

Done by Claude Opus 5.5 in Claude Code (via T3 Code).

🤖 Generated with Claude Code

[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: 9077e81 · PR result: e9e0aa1 · 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

Updated in place by a trusted workflow. PR artifacts are strictly validated and never executed.

[macroscopeapp]

Approvability

Verdict: Needs Human Approval

Macroscope's review found this PR requires human approval — This PR adds cross-cutting production telemetry for every MCP tool invocation and delegated-task completion, including new provider/thread classification logic and a background orchestration subscriber. Because the behavior is active on existing paths and introduces substantial new runtime and external-data side effects, the change merits human review.

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

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📝 Walkthrough

MCP tool calls now record outcome and duration data, with provider and handoff dimensions when available. A server runtime service also records analytics events for app-owned delegated tasks that reach final statuses.

Changes: Agent tool analytics

Layer / File(s)	Summary
Provider dimensions and event properties apps/server/src/telemetry/ProviderDimensions.ts, apps/server/src/telemetry/ProviderDimensions.test.ts, docs/internals/product-analytics.md	Provider dimensions use driver names and include model slugs only for eligible non-custom vendor-catalog models. Agent tool properties include caller and target details, outcome, and applicable handoff settings. Tests cover provider fallback, outcomes, origins, and settings. The documentation states which data is and is not reported.
MCP invocation and handoff recording apps/server/src/mcp/McpHttpServer.ts, apps/server/src/mcp/toolkits/core.test.ts	MCP tool registrations record invocation outcomes and durations. Handoff events can include caller and target details, bounded depth, scheduled-run status, and handoff settings. The integration test checks a cross-provider t3_thread_fork event.
Delegated-task completion analytics apps/server/src/telemetry/DelegatedTaskAnalytics.ts, apps/server/src/telemetry/DelegatedTaskAnalytics.test.ts, apps/server/src/server.ts	A server runtime service consumes orchestration events and records one event per app-owned task that reaches a listed final status. The event includes available provider and model dimensions and optional completion-wake and duration data.

Priority: ⬇️ Low

Estimated code review effort: 3 (Moderate) | ~25 minutes

Change: Feature

Sequence Diagram(s)

sequenceDiagram
  participant McpServer
  participant ToolHandler
  participant ThreadManagementService
  participant ProviderRegistry
  participant AnalyticsService
  McpServer->>ToolHandler: Invoke registered tool
  ToolHandler-->>McpServer: Return result or failure
  McpServer->>ThreadManagementService: Resolve handoff threads
  McpServer->>ProviderRegistry: Resolve provider dimensions
  McpServer->>AnalyticsService: Record mcp.tool.invoked

Loading

sequenceDiagram
  participant Orchestration
  participant DelegatedTaskAnalytics
  participant ProviderRegistry
  participant AnalyticsService
  Orchestration->>DelegatedTaskAnalytics: Emit subagent.updated event
  DelegatedTaskAnalytics->>ProviderRegistry: Resolve caller and target provider dimensions
  DelegatedTaskAnalytics->>AnalyticsService: Record mcp.delegated_task.finished

Loading

Suggested reviewers: t3dotgg

Merge Risk: 🔵 Low · up to 0055b

A transient lookup failure can omit a delegated-task analytics event even when the task later receives another terminal update. The impact is limited to analytics reporting; the PR is otherwise mergeable with this small correction noted.

Pre-merge checks: 4

Check name	Status	Explanation
Title check		The title is concise, clear, and directly describes the main change: adding analytics for T3 MCP tool usage.
Description check		The description clearly explains the problem, implementation, telemetry fields, anonymity rules, and verification. It does not include an explicit Scope and approval section or issue/maintainer approv…
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: Description check

Explanation

The description clearly explains the problem, implementation, telemetry fields, anonymity rules, and verification. It does not include an explicit Scope and approval section or issue/maintainer approval link, but it is otherwise substantially complete.

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Actionable comments posted: 2

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Inline comments:
Review comments at @apps/server/src/mcp/OrchestratorMcpService.ts:
- Line 1454: Update the caller model selection in the delegate_task event and
each create_threads event to use the active run’s dimensions from
parentRun.modelSelection instead of the thread’s parent.thread.modelSelection.
Make the change at both affected sites in
apps/server/src/mcp/OrchestratorMcpService.ts:1454 and
apps/server/src/mcp/OrchestratorMcpService.ts:1727.

Review comments at @apps/server/src/mcp/toolkits/project/handlers.ts:
- Around line 49-60: Move the provider lookup and analytics recording from
recordLaunch into a domain service method for MCP thread launches, then have the
transport handler call that method while retaining only request decoding and
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• apps/server/src/mcp/McpHttpServer.ts
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Inline comments:
Review comments at @apps/server/src/mcp/McpHttpServer.ts:
- Around line 764-768: Update the handoff target resolution around
`resultThreadIds` and `targetIds` so successful `t3_queue_edit`,
`t3_queue_promote_to_steer`, and `t3_pending_request_respond` calls fall back to
the explicit `threadId` argument only when the result contains no target ID.
Keep this fallback limited to those tools and successful results, and retain the
existing filtering that excludes the invocation thread.

Review comments at @apps/server/src/telemetry/DelegatedTaskAnalytics.ts:
- Line 29: Expose DelegatedTaskAnalytics.make as a Context.Service and provide a
module-owned layer that constructs the service while preserving its start and
onSubagent operations. Update DelegatedTaskAnalyticsLive to obtain the service
through that layer and start it during registration.

Review comments at @apps/server/src/telemetry/ProviderDimensions.ts:
- Around line 84-118: In handoffSettings, whitelist delegate_task’s mode to the
supported values async and wait, mapping any other supplied string to a safe
fallback. Apply the same allowlist approach to t3_thread_launch’s
workspaceStrategy.type, permitting root, existing_worktree, and worktree;
preserve the existing defaults when values are absent and leave
t3_thread_send.delivery unchanged.

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- Around line 926-935: Detach analytics recording from the MCP response path in
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⚠️ Outside diff range comments (1)

🟡 Minor · Mark the task as reported only after recording succeeds. · DelegatedTaskAnalytics.ts:43-81

apps/server/src/telemetry/DelegatedTaskAnalytics.ts:43-81
🗄️ Data Integrity & Integration | 🟡 Minor | ⚡ Quick win

Mark the task as reported only after recording succeeds.

getThreadShell can fail before analytics.record. The handler ignores that failure after adding the task ID to reported. streamDomainEvents is live-tail only, and forkParked does not retry the handler. A later final update can therefore be skipped permanently.

Suggested fix

-      reported.add(task.id);
       const parent = yield* orchestrator.getThreadShell(task.threadId);
       const providers = yield* registry.getProviders;
@@
       yield* analytics.record("mcp.delegated_task.finished", {
@@
         ...(durationSeconds === undefined ? {} : { durationSeconds }),
       });
+      reported.add(task.id);

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Review comment at @apps/server/src/telemetry/DelegatedTaskAnalytics.ts around
lines 43 - 81:
In the onSubagent handler, add task.id to reported only after analytics.record
succeeds; keep the existing duplicate check before processing so failures in
getThreadShell or recording do not permanently suppress later final updates.

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Outside diff comments:
Review comments at @apps/server/src/telemetry/DelegatedTaskAnalytics.ts:
- Around line 43-81: In the onSubagent handler, add task.id to reported only
after analytics.record succeeds; keep the existing duplicate check before
processing so failures in getThreadShell or recording do not permanently
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[juliusmarminge]

Fixed CodeRabbit's outside-diff finding on DelegatedTaskAnalytics.ts in e9e0aa1: the task id is added to reported only after mcp.delegated_task.finished is recorded, so a failed parent lookup no longer drops that task permanently. The test now fails the first lookup and checks that the next final update reports the task exactly once. It fails without the fix.