[Bug]: t3_thread_list includeSubagents:false still lists tasks delegated from a linked environment, and omits delegatedFrom #36956

Before submitting

• I searched existing issues and did not find a duplicate.
• I included enough detail to reproduce or investigate the problem.

Area

apps/server

Steps to reproduce

1. Link environment A to environment B (Linked environments on).
2. From a thread on A, run delegate_task with target.environmentId = B, and let it finish. Don't settle it on B.
3. On B, call the MCP tool t3_thread_list with allProjects: true, includeSubagents: false.
4. Call t3_thread_read on that same task thread on B.

Expected behavior

includeSubagents: false leaves the delegated task out, as the desktop and mobile apps do when they nest it under its parent. At the least, t3_thread_list and t3_thread_read should return delegatedFrom, so a caller can tell the task is not an ordinary top-level thread.

Actual behavior

The task is returned as an ordinary top-level thread: threadId: "mcp:launch:…", createdBy: "agent", creationSource: "mcp", parentThreadId: null, relationshipToParent: null. delegatedFrom is not in either tool's output. The parent thread on A records the task as a remote delegate.

The apps and the MCP tools classify the same thread differently:

• packages/contracts/src/orchestrationV2.ts has isDelegatedAppThread (relationshipToParent === "subagent" || delegatedFrom != null), which treats it as delegated.
• ThreadManagementService.listProjectThreads (apps/server/src/orchestration-v2/ThreadManagementService.ts) filters with isListedThreadLineage, which only checks relationshipToParent and sideChat, so the task passes as listed.
• The thread shell mapping in apps/server/src/mcp/OrchestratorMcpService.ts never outputs delegatedFrom (no reference in that file).

As a result, agents and outside tools that read thread state through MCP can't tell a cross-machine delegated task from a thread an agent launched itself. In our case, two separate agents wrongly concluded that an orchestrator had misused t3_thread_launch, and a status tool that already passes includeSubagents: false still showed every remote task as unread top-level work.

Related issues (why this isn't a duplicate)

• iPhone app lists cross-machine delegated tasks as top-level threads; desktop nests them under their parent #26854 / feat(server): delegate_task to a linked environment #16719 and Delegated tasks show as top-level sidebar threads when their parent is an older settled thread #35263 / fix(server): a task on a linked environment stays under its parent in trimmed shell snapshots #34870 fixed how the desktop and mobile apps nest these tasks. This issue is about the MCP thread tools, which neither fix touched.
• Agent-launched thread on a linked environment is hidden from the sidebar and missing from the parent's Lineage panel when t3_thread_launch gets delegatedFrom #27004 covers t3_thread_launch with delegatedFrom being hidden in the apps. One comment there notes in passing that t3_thread_list and t3_thread_read don't return delegatedFrom. This issue is the delegate_task path and the MCP list filter.

Impact

Minor bug or occasional failure

Version or commit

0.1.10-nightly.20261114.4695 on both machines (server and desktop). Code paths checked on main @ ed101ef.

Environment

Two macOS (arm64) machines running T3 Code servers, linked as environments with full access over Tailscale. Delegates ran OpenCode (opencode-go/deepseek-v4.1-flash).

Logs or stack traces

# t3_thread_list on B, includeSubagents: false (trimmed)
{"threadId":"mcp:launch:9229a46d…","title":"AGENTS.md Reddit split (B)",
 "createdBy":"agent","creationSource":"mcp","status":"completed",
 "parentThreadId":null,"relationshipToParent":null, ...}

# delegate_task call on A, same second the thread above was created (trimmed)
{"toolName":"mcp__t3-code__delegate_task",
 "input":{"title":"AGENTS.md Reddit split (B)",
  "target":{"environmentId":"<B>","providerInstanceId":"opencode", ...}}}
# A's parent thread then shows a subagent item: node:delegated-task:…:remote-delegate:…

Screenshots, recordings, or supporting files

No response

Workaround

Filter client-side on threadId starting with mcp:launch: + createdBy: "agent" + creationSource: "mcp" + parentThreadId: null. This also hides threads an agent was asked to open with t3_thread_launch, so it's only a heuristic.

Posted by Claude Opus 5.5, an agent, on behalf of the user.