Constrain where a worktree may live and skip it under headless dispatch

create-dev-loop.md

@@ -173,7 +173,7 @@ git log --oneline -10
 - **Check for a stuck mid-revert first.** If the PR's {{EXTERNAL_SIGNAL_LABEL}} is red on the final run *and* the HEAD commit message starts with `TEMP:` (the fallback-ladder rung 1 marker in Phase 4), do not treat this as ordinary red {{EXTERNAL_SIGNAL_LABEL}} — a prior session was killed mid-ladder between pushing the temporary revert and restoring the fix. Read the `TEMP:` message for the verified-good SHA it names, `git reset --hard <that-sha>` and force-push to restore the fix, confirm {{EXTERNAL_SIGNAL_LABEL}} is green again, then continue triage as normal.
 - If the PR is still valid ({{EXTERNAL_SIGNAL_LABEL}} green, no conflicts), **first confirm a Phase 4 self-review was actually posted** (a carried-over PR from a prior cycle may never have completed it). If none is recorded, perform the Phase 4 self-review now ({{EXTERNAL_SIGNAL_LABEL}} must be green first) before jumping to Phase 5. Otherwise jump to Phase 5 to re-poll for review.
 - If the PR is stale or conflicted, close it with a comment explaining why, then proceed with triage.
-- **If the open PR was authored by a concurrent session/another author** (not this loop), do not misread "don't open a new PR" as "do nothing": adopt it — bring it current with `{{DEFAULT_BRANCH}}`, re-run full {{EXTERNAL_SIGNAL_LABEL}}, review, and merge if green (or close it with a reason). Under a `git worktree` workflow the main checkout stays on `{{DEFAULT_BRANCH}}` to avoid colliding with the other session's tree.
+- **If the open PR was authored by a concurrent session/another author** (not this loop), do not misread "don't open a new PR" as "do nothing": adopt it — bring it current with `{{DEFAULT_BRANCH}}`, re-run full {{EXTERNAL_SIGNAL_LABEL}}, review, and merge if green (or close it with a reason). Under a `git worktree` workflow the main checkout stays on `{{DEFAULT_BRANCH}}` to avoid colliding with the other session's tree — see the concurrent-session entry in Edge cases for where the worktree must live, and why a headless dispatch should not create one at all.
 
 Do not open a new PR while one is already open against the same repo.
 
@@ -541,7 +541,7 @@ Return to Phase 1.
 **The external anchor cannot run (tool/interpreter absent or broken in the sandbox, or the sandbox restricts filesystem/tool access to only the target repo's own working directory — common in gardener-dispatched sessions, and possibly extending to blocking creation of a *new* directory inside that allowed root, which rules out cloning a fixture locally as a workaround):** do not claim it green and do not iterate on the sandbox. Flag **UNVERIFIED** and gate on scope (Phase 4): anchor-relevant files changed → mark UNVERIFIED + do-not-auto-merge + hand to CI/human (prefer the CI check on the exact head SHA); no anchor-relevant files (docs-only) → record UNVERIFIED-not-applicable and continue, stating it in the PR body.
 **An issue requires a harness-blocked operation (editing `CLAUDE.md`/agent-loaded config, registering an external submodule):** recognize it at triage (Phase 1) — surface to the user for explicit authorization rather than attempting it mid-cycle; never remove a path while `CLAUDE.md` still references it.
 **Autonomous multi-cycle batch (`/<loop> until …`):** skip/cap the Phase-5 human-review wait (rubric + green anchor is the gate); still hand off do-not-auto-merge/charter PRs. Stop when only blocked, charter-gated, or too-large work remains, or a cycle yields no scoped work.
-**A concurrent session holds the tree or an open PR:** adopt its PR (bring current with `{{DEFAULT_BRANCH}}`, re-run the anchor, review, merge if green) rather than doing nothing; work in a `git worktree` to avoid colliding, and treat a harmless local `--delete-branch` failure as success once `gh pr view --json state` confirms the merge.
+**A concurrent session holds the tree or an open PR:** adopt its PR (bring current with `{{DEFAULT_BRANCH}}`, re-run the anchor, review, merge if green) rather than doing nothing; work in a `git worktree` to avoid colliding, and treat a harmless local `--delete-branch` failure as success once `gh pr view --json state` confirms the merge. **Put the worktree inside the repository checkout** (e.g. `.worktrees/<branch>`, added to `.git/info/exclude` so an untracked directory doesn't pollute `git status`), never in `/tmp` or anywhere else outside it: a path-restricted sandbox refuses every read and edit outside the checkout, so a worktree placed there locks the session out of its own working tree one file operation at a time. **In a headless dispatch (e.g. `gardener tend`), do not create a worktree at all** — the run already owns a clone dedicated to it, so there is no concurrent session to collide with, and the checkout can be used directly.
 **A test fails intermittently (suspected flake):** re-run the test command once. If the same test fails again, treat it as a real failure and investigate. If it passes on the second run, note the flake in the PR body and proceed — do not suppress or `@Ignore` a test without understanding why it is flaky.
 **A review comment is a false positive:** reply with evidence, do not apply the change.
 **A `gh` command fails with a transient network/transport error (`http2: client conn could not be established`, `unexpected EOF`):** retry once or twice before treating it as blocked — do not treat the first failure as terminal and silently drop a self-review, commit, or comment.