Fleet Coordination — ThumbGate

ThumbGate is worked by several agents (Claude Code, Codex, grok, Gemini,
Hermes) fed from the same broadcast prompt, on the same checkout host.
Coordination is not optional: the repo ruleset and single-writer lease exist
because two agents once mutated the same checkout concurrently and wiped each
other's work (incident 2026-08-11, see AGENTS.md "Single-Writer Checkout Lease").

The contract

Before ANY state mutation (git checkout/clean/reset, branch/worktree creation,
push, PR open/merge, vault write), complete these checks:

1. Checkout lease — only one live session owns a checkout.
   Claim: THUMBGATE_SESSION_AGENT=<session-id> node scripts/session-lease.js claim
   Verify: node scripts/session-lease.js check
   Exit 1 = another live agent owns it. Use git worktree add instead.
2. Vault claims — ~/Documents/AI-Agent-Sync/Agent-Jobs/running/*.md
   touching ThumbGate belong to other agents unless stale (>7d, dead PID).
3. Vault dirty state — 180+ uncommitted files is normal; never git add -A
   there. Stage only your own file.
4. Linear ownership — issues in In Progress/In Review with a ThumbGate
   title are claimed. Do not start overlapping work; claim your own issue first.
5. Herdr live panes — when the gateway is up, same-cwd agents are live
   collision risk.
6. Open PR census — never duplicate an open PR or its review threads.

The one-command sweep

bash .claude/scripts/session-bootstrap/fleet-coordination-check.sh

Prints every surface above in one pass (read-only). SessionStart hook already
runs it; if you did not see its output this session, run it before the first
mutation.

Write-back rules (your own file only)

• Vault state: Agent-State/<agent>.md may be shared by every instance of that
  agent kind — check its mtime first. Prefer a dated file under
  Handoffs/<date>-<topic>.md when in doubt. Commit only your file with
  git add <your-file> and open a PR (branch protection applies there too).
• Linear: claim via the Linear bridge or API before long-running work so
  another agent can see ownership.
• This repo: never git add -A in a shared checkout. Stage explicit paths.

Failure mode this prevents

Two agents, same repo, both "helpful": one force-checkouts main and cleans,
wiping the other's untracked work; the other git add -As the debris into the
wrong branch. The lease + claim + census above make that collision visible
before it happens.

Concurrent Agent-State writes (HARD)

Never write to Agent-State/<other-agent>.md. Each session appends only its own Agent-State/<this-agent>.md (or Handoffs/*<this-agent>*). Two same-kind sessions must use distinct filenames (e.g. grok.md vs grok-<session>.md) or an atomic claim/lease before overwrite.