feat(mcp): configure existing conversations

[juliusmarminge]

Problem

Agents could inspect thread activity but could not discover or change an existing thread's provider, model options, runtime mode, or interaction mode through the built-in MCP server.

Change

Add current-project t3_thread_configuration and t3_thread_configure tools backed by a focused service, existing V2 commands, provider-switch planning, typed receipts, provider capability discovery, and caller permission ceilings.

Behavior

All requested fields are validated before the first new command. Omitted fields retain committed values except that a provider-only change selects that provider's default model; omitted options are otherwise preserved, an explicit empty list clears them, and provider or model changes never inherit incompatible options. Durable accepted and rejected command legs replay under the same client request ID; resolving a rejected leg requires a new ID. Results separate committed settings from requested detach/restart and next-turn handoff effects.

Focused validation

• 18 contract, root-schema, service, production MCP, and real V2/provider-adapter behavior tests
• durable no-op/replay, cross-provider retry, concurrent selection, and caller-downgrade race coverage
• vp run --filter t3 typecheck
• vp run --filter @t3tools/contracts typecheck
• targeted formatting and git diff --check

Dependency

Standalone PR based on t3code/codex-turn-mapping at the pinned rollout target. It is not a member of a native GitHub stack.

Implemented by GPT-5.6-Sol via Codex in T3 Code.

Note

Add t3_thread_configuration and t3_thread_configure MCP tools for existing conversations

• Adds ConversationConfigurationMcpService with read and configure operations that let MCP callers inspect and change a thread's provider/model selection, runtime mode, and interaction mode
• Registers t3_thread_configuration (read-only, idempotent) and t3_thread_configure (destructive) tools in the orchestrator toolkit, with handlers delegating to the new service
• Adds contracts in conversationControlMcp.ts covering configuration inputs/outputs, option omission vs. empty array, durable command receipts, change behaviors, and retry guidance
• Extends OrchestrationV2Command variants with optional policy ceilings and expected-selection guards; the orchestrator now loads the caller thread, enforces mode ceilings, rejects stale partial selections, and dispatches policy-bounded commands under nested caller+target thread locks
• Retried requests with the same clientRequestId replay accepted or rejected durable receipts instead of re-dispatching; mode reductions below the caller's ceiling are prioritized over other pending changes
• Fix: EventSink now assigns the thread's latest sequence to command receipts for accepted commands that produce no events, instead of failing
• Risk: policy-bounded configuration dispatches in makeOrchestrator now acquire nested locks over sorted caller+target thread IDs via dispatchLockKeys; commands without a caller thread still use the single target lock, but any deadlock-prone lock ordering assumptions should be reviewed there

^{Macroscope summarized 26d25cb.}

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[macroscopeapp]

Effect service conventions review of the new ConversationConfigurationMcpService and its touched call sites. One convention violation found; dependency acquisition (yield* ThreadManagementService / ProviderRegistry / ProviderSwitchServiceV2), the make + layer pair, and the absence of ManagedRuntime/runPromise in the service all look correct.

^{Posted via Macroscope — Effect Service Conventions}

[github-actions]

Thread transfer impact

⚠️ The latest CI run did not produce a thread transfer result for 26d25cb.

This comment will update automatically after the next completed run.

[macroscopeapp]

Approvability

Verdict: Not approved

Macroscope's review found this PR not approvable — This PR adds production MCP controls that can change conversation providers, models, runtime policies, and interaction modes, including effects such as provider-session detachment. It also modifies shared orchestration locking, policy enforcement, and durable receipt behavior, making human review appropriate.

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

[macroscopeapp]

UI Consistency: 1 issue found

ChatMarkdown is a shared renderer used by chat threads, review annotations, and the pull request panel. At this head it resolves the environment for its editor RPC and capability read from the globally active environment instead of the markdown's own scope, and the explicit environmentId prop that let non-thread call sites supply that scope was removed. Details inline.

^{Posted via Macroscope — UI Consistency}

[macroscopeapp]

Macroscope skipped reviewing this pull request. Per-review cost limit exceeded (workspace setting).

This review would cost an estimated $246.91, which exceeds your per-review limit of $10.00.

The top 3 files driving up this estimate:

File	Diff Size	Estimate
apps/server/src/orchestration-v2/Orchestrator.ts	280.58KB	$14.03
apps/server/src/orchestration-v2/Adapters/AcpAdapterV2.ts	271.74KB	$13.59
apps/server/src/orchestration-v2/Adapters/CodexAdapterV2.ts	215.40KB	$10.77

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[cursor]

Cursor Bugbot has reviewed your changes using high effort and found 1 potential issue.

^{Bugbot Autofix is ON, but a cloud agent failed to start.}

^{Reviewed by Cursor Bugbot for commit 363abe5. Configure here.}

[juliusmarminge]

Superseded as the active MCP proposal by #10557 in the rebuilt MCP stack, following the maintainer request to review thin service wrappers separately from service hardening.

This is not a full feature-parity replacement. This intentionally limits writes to the caller. Permission-mode changes, cross-thread configuration and multi-command retry transactions are separate work. Provider/model discovery already exists in orchestrator_capabilities.

Closing this mixed proposal without merging. The remote branch agents/mcp-conversations/configuration and exact head 26d25cba6e28d34bd0139f25e29cb9d48ebdd1ba are retained so the service changes can be extracted for separate review later.