fm-spawn writes claude's per-task hooks into the project worktree, dirtying it and leaving permanent .git/info/exclude residue

[AlexAgenCheck]

Summary

bin/fm-spawn.sh wires a claude crewmate's per-task busy-state hooks by writing
<worktree>/.claude/settings.local.json inside the project worktree, then adding that path to the
worktree's .git/info/exclude. Two consequences follow:

1. Firstmate writes into a project checkout, which AGENTS.md hard rule 1 otherwise forbids.
2. Every spawn leaves a residue line in the clone's .git/info/exclude. Nothing retires those lines, and
   cleaning them would itself require firstmate to write into the clone.

On a project that tracks .claude/settings.local.json the write is worse than untidy: the worktree ends
up dirty, so teardown needs --force on work that is otherwise perfectly landed, which collides with the
"never tear down unlanded work" directive because the operator learns to reach for --force routinely.

At origin/main (dc0172c) the behaviour is still present - bin/fm-spawn.sh around lines 2284, 2358 and
2361 writes the file and calls exclude_path '.claude/settings.local.json'.

Suggested direction

The harness already accepts a settings file by path, so the hooks never need to live in the project tree:
pass --settings <firstmate-home>/state/<id>.claude-settings.json at launch and have teardown remove that
state file. The worktree then stays clean, no exclude residue accumulates, and teardown needs no --force.

Care is needed in three places we hit while doing this locally:

• The same wiring path covers other harnesses (codex writes project hooks too), so a gate that only
  considers claude leaves the sibling case behind.
• Relaunch must settle whether out-of-tree wiring is feasible before retiring the prior wiring,
  otherwise a failed relaunch leaves a task with neither.
• A spawn abort should release its worktree-pool lease, and must not force-discard a dirty worktree while
  doing so.

Patch available

We carry a working fix locally (13 files, +921/-35, including a live end-to-end hooks test and teardown
coverage). We have no push access to this repository, so we cannot open a pull request. Happy to attach the
patch or the individual commits here if that is useful to you - say the word and we will paste them.

We are also carrying it as our only local deviation from upstream, and would rather drop it the moment an
upstream fix lands.

[kunchenguid]

Speaking as Kun's firstmate:

Triage on current main (dc0172c48b36a6303501af25d0915ad6e7d04192). Author is AlexAgenCheck, not automation. No comments in the thread. Report cited dc0172c; the spawn wiring path is unchanged on this SHA.

VISION

• The first mate reads projects but does not change them; project changes belong to workers in isolated copies — aligns. fm-spawn writes <worktree>/.claude/settings.local.json and appends that path to the clone's .git/info/exclude. That is firstmate mutating the project checkout, not a worker shipping through the project's selected path.
• Unlanded work is never torn down; a refusal to discard is a finding, not an obstacle — aligns. On a project that tracks .claude/settings.local.json, the write dirties the worktree, so teardown needs --force on otherwise landed work. Training operators to reach for --force routinely is the collision the report names.
• Peace of mind / nothing falls through the cracks when attention leaves — aligns. Exclude residue is permanent and nothing retires it. Cleaning it would itself require another write into the clone.

Real, still present. Labeling ready-for-pr and leaving open. Pi already wires out of tree (state/<id>.pi-ext.ts); Claude (and OpenCode plugin / grok-kimi token pointers) still go through the worktree plus exclude_path.

Inspected on main

• bin/fm-spawn.sh exclude_path (lines 2282-2288): resolves the worktree's .git/info/exclude and appends the relative path; nothing later removes the line.
• bin/fm-spawn.sh claude arm (lines 2351-2361): mkdir -p "$WT/.claude", writes $WT/.claude/settings.local.json with UserPromptSubmit/Stop/StopFailure/SessionEnd hooks, then exclude_path '.claude/settings.local.json'.
• Same function also writes OpenCode's plugin into $WT/.opencode/plugins/fm-busy-state.js (2414) and token pointers .fm-grok-turnend / .fm-kimi-turnend. A Claude-only gate would leave siblings behind, as the report notes.
• Pi is the contrast case (2416-2447): extension is written under state/, cleaned by teardown, never via exclude_path.