[chuks-qua]

What

Before this change, the server read the user's message to decide whether a turn got Mcode thread control. isExplicitMcodeThreadRequest matched wording such as "mcode thread" plus an action verb and rejected messages with a nearby negation. Requests like "Farm this out to Codex" or "Call delegate_task once. Do not call any other tool." got no lease, and the tool call failed with "Internal thread-control MCP request denied".

Now no turn depends on its wording. isExplicitMcodeThreadRequest and its regexes are deleted. Every turn on a provider that supports internal thread control (claude, codex, cursor, copilot) gets an active lease, and the lease still revokes at turn end.

The limit is ADR-0032's permission-mode ceiling. A supervised Coordinator cannot request a full child, and a child with no named mode inherits the Coordinator's. delegated-task-service.ts and thread-control-service.ts enforce it.

A denied call now carries a reason, invalid_tool_call or no_active_turn, with a message the model and the user can act on.

Codex no longer restarts its session when threadControlEligible changes between turns. The flag is now constant per provider, so it never changes.

The fix round also:

• Activates the lease on turns a provider starts by itself, such as Claude continuing after a background task. These turns never got a lease before.
• Grants the lease the turn's effective permission mode. A "default" turn on a thread saved as Full now gets a Full lease. Before, it got Supervised.
• Rewrites the model guidance in packages/thread-orchestration/src/mcode-instructions.ts. "Hand work to another provider or model" now uses delegate_task without naming Mcode threads. Native sub-agents stay the default for "sub-agent" requests, and the model never launches a thread just because the user said "sub-agent".

Verification:

• Targeted vitest runs pass: thread-orchestration (20 tests), and server agent-service-gate, mcode-session-authority, thread-control-toolkit, and agent-service-container (75 tests).
• Typecheck passes for thread-orchestration, contracts, server, and providers. bun run lint exits 0.
• Main was merged in, which added thread_launch. Main's new gate tests in src/mcode-instructions.test.ts were removed along with the gate.
• Not verified on a live provider turn.

Why

The wording check guarded the wrong thing. It read the user's words, not what the delegated work may do, and it refused ordinary requests with an error that gave no cause. ADR-0032 replaces it with the permission-mode ceiling.

Fixes #2267. Part of #2218.

Review Notes

• Behavior change: a message such as "Do not create an Mcode thread" no longer blocks thread control on the server. The model's guidance now carries that case, and the permission-mode ceiling still bounds what any child may do.
• Not in this PR: stepping inherited modes down to the target provider. feat: offer Delegation without the wording gate, bounded by a runtime-mode ceiling #2218 stays open for it.
• Follow-up: consider deleting the now-constant threadControlEligible plumbing.
• Open questions for later issues, not fixed here:
  • Thread-control reads (thread_search, thread_get, thread_wait, workspace_search) are not bounded by the permission ceiling, and they are now available on every turn.
  • Delegation has no depth or concurrency cap, and a Full child can stop its Full Coordinator.
  • A replayed delegate_task with the same clientRequestId launches its saved plan before the ceiling check. This predates this PR.
• No UI change, so no screenshots.

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