execute-phase

name	execute-phase
description	Harness Code executor for a <harness>-plan-phase lane plan. Uses TeamCreate, worktree-isolated teammates, lane DAG ordering, verification gates, and retry-once failure handling.

-execute-phase

Runtime State

For reflections, handoffs, and latest handoff pointers, follow <harness>-config/shared/runtime-state.md. This repo/branch/run-isolated contract supersedes any older flat closeout examples retained for historical context in this skill.

shared/phase-loop/protocol.md is the canonical shared contract for the automation: object, verification_status, frozen blocker taxonomy, manual event import, and downstream roadmap-amendment handling.

When launched by the live phase-loop adapter, this skill runs through non-interactive <harness> -p; its final reply must still emit the shared automation: closeout or the parent runner will reduce the turn to repeated_verification_failure rather than silent success. The repo-injected workflow bundle remains authoritative whether the adapter delivers it inline or through the run-local context-file fallback. That repo-owned bundle includes the full Harness workflow pack (<harness>-phase-roadmap-builder, <harness>-plan-phase, <harness>-execute-phase, and <harness>-phase-loop) and does not depend on installed bridge skills under resolve_skill_bundle_root("claude")/.

Harness closeout and blocker reporting must use the shared literals directly, including dirty_worktree_conflict, and must treat older downstream plans as stale after a roadmap amendment.

Runner-Owned Lane Work Units

Injected HARNESSLANE runs may include a HarnessLaneAssignment from shared/phase-loop/protocol.md. Treat that assignment as the work-unit contract: execute only the selected lane_id, write only the listed owned_files, treat consumed_interfaces as read-only, and emit one shared automation: closeout for that work unit. Installed-skill drift is warning-only when the repo-injected context is present.

Native Harness subagent and agent_team activity stays internal unless it emits a typed DelegationRequest and the runner approves it. Review, reducer, verify, and closeout prompts are distinct from implementation prompts. If the selected policy is unsupported by the active harness, stop with a typed non-human blocker instead of silently downgrading.

Phase-Loop Adapter Mode

When the prompt or run-local context file starts with a concrete <harness>-execute-phase <plan> command from .codex/phase-loop/runs/, this adapter mode overrides the orchestrator-only interactive workflow below.

• Do not read installed handoffs under resolve_skill_bundle_root("claude")/**; the run-local context and the plan artifact are the only predecessor context.
• Do not call ToolSearch, TaskCreate, TaskUpdate, TaskList, TeamCreate, TeamDelete, Agent, SendMessage, EnterWorktree, ExitWorktree, or AskUserQuestion.
• Do not create .claude/worktrees/ or lane branches. Execute the plan directly in the provided workspace, respecting the plan's owned-file boundaries and running the narrowest applicable verification commands.
• Treat ignored, private, raw-data, credential, and evidence-source files as read-protected unless the run-local context, phase plan, or source bundle explicitly allowlists the exact path or glob for read access. Do not infer permission from nearby owned output paths, old memory, or prior phases.
• Do not read or write ~/.claude/** reflection or handoff files, and do not edit .codex/phase-loop/ runner artifacts. Adapter-mode closeout happens only through stdout plus repo-local artifacts.
• If a missing script or unavailable helper is nonessential, replace it with a direct repo-local check and record the substitution in the closeout. If the missing input is essential, stop with a shared blocked automation: closeout.
• If ambiguity, access, dirty-state, or merge safety handling would normally ask a user, stop and emit a shared automation: closeout with status: blocked, human_required set accurately, the frozen blocker_class, concrete blocker_summary, and verification_status: blocked.
• End stdout with one shared automation: closeout. Do not wait for interactive approval after verification is complete.
• Do not emit a /clear recommendation or any human-only context-reset instruction. Continuity to the next phase is the run-local handoff plus the runner re-invoking the next phase in a fresh executor process — that fresh process is the context reset. There is no human in this loop to reset it.
• Before that closeout, run git status --short and classify dirty paths against the active plan's owned files and control artifacts. If a generated path is unowned, ignored without explicit allowlist/staging policy, or derived from unauthorized raw/private inputs, stop with dirty_worktree_conflict instead of reporting completion. But when required verification passed and the ONLY uncommitted paths are phase-owned outputs this run was not authorized to commit, report awaiting_phase_closeout and let the runner's graduated closeout gate commit them — reserve dirty_worktree_conflict for unowned, unauthorized-ignored, or overlapping-unrelated paths.

Follow-on executor for /<harness>-plan-phase. Consumes the plan doc + TaskCreate'd lane tasks and drives them to completion: root lanes first, parallel lanes in parallel, auto-merge on green, retry-once on failure, halt-all on second failure.

When to use

• /<harness>-plan-phase has produced plans/phase-plan-<VERSION>-<PHASE_ALIAS>.md and a TaskCreate'd task per lane.
• You want the phase executed full-auto end-to-end, with lanes merging to the current branch as their gates go green.
• The working tree is clean and you're on the branch lanes should merge into.

When NOT to use

• Plan doc has never been produced → run /<harness>-plan-phase first.
• You want human checkpoints between lanes → execute lanes manually (Agent(isolation: "worktree", name: "<SL-ID>") with the lane's section pasted in).
• The plan doc's DAG has cycles or a lane's owned files overlap another lane's → fix the plan first.

Model tiers (edit on Anthropic releases)

Model IDs appear only in this table. All model-routing logic in the workflow references the tier name.

Tier	Model	Use for
frontier	claude-opus-5	retry escalation ceiling, highest-stakes lanes
strong	claude-sonnet-5	contract-authoring (IF-freeze), schema/migration, algorithmic
fast	claude-haiku-4-5-20251001	mechanical wiring, small components against frozen types

These map to the runtime model_class axis: implementer = strong, worker = fast. (The planner class routes to the ULTRA model claude-fable-5 — a planning-tier model ABOVE this execute table; it is NOT frontier, which is the heavy model claude-opus-5.) The shipped model_policy dispatches implementation at the implementer class. The runtime's model_class-escalation bookkeeping is runner-internal and is NOT applied to the launched model — see governed_premerge.next_escalation / runner.py for its current status. This skill's own retry-tier ladder is fast → strong → frontier (below). The default run_mode is autonomous — no panel, no human_required; every governed escalation terminal is a non-human review_gate_block surfaced in the run-end summary, never a synchronous human wait.

Governed mode is live on the serial path (--governed / PHASE_LOOP_RUN_MODE=governed, model-routing-v2): a pre-merge panel gate (codex + gemini) reviews the implementation diff before the closeout commit and runs a bounded review→fix→re-review loop; a block finding holds the merge until fixed or the bounded loop terminates non-human. Autonomous runs spawn no panel. Concurrent-wave dispatch is not governed yet.

Inputs

Arg	Required	Meaning
<plan-path>	no	Path to plan doc. Default: auto-detected via env vars + filename convention.
--dry-run	no	Parse + validate, print the dispatch schedule with per-lane model assignments, do not spawn teammates.
--resume	no	Continue a partially executed plan: skip lanes already merged (their merge commit is on the target branch and their produced gates are closed).

Environment variables

Plan-location variables are inherited from <harness>-plan-phase so the two skills resolve the same defaults:

Variable	Default	Meaning
PLAN_SPEC	Auto-detected highest specs/phase-plans-v*.md	Path to spec file (used only for version extraction here).
PLAN_VERSION	Extracted v\d+ from spec filename	Version token embedded in plan-doc filename.
PLAN_PHASE_ALIASES	Built-in alias table	Path to alias-map JSON.
PLAN_DOC	plans/phase-plan-<VERSION>-<PHASE_ALIAS>.md	Override the resolved plan-doc path directly.
EXECUTE_MERGE_TARGET	Current branch at invocation	Branch lanes merge into.
EXECUTE_WORKTREE_ROOT	.worktrees/ (inside repo; auto-gitignored)	Root dir for per-lane worktrees.
EXECUTE_MAX_PARALLEL_LANES	4	Max concurrent lane dispatches per wave; parallelism-maximizing default. Lower to 2 when stale-base churn becomes problematic on phases with many interdependent lanes.

Expected helpers

Helpers under resolve_skill_bundle_root("claude")/_shared/ may be absent on some hosts. Each helper degrades as listed:

• _shared/next_reflection_path.py — legacy helper only; current closeout writes reflections to resolve_skill_bundle_root("codex")/<harness>-execute-phase/reflections/<repo_hash>/<branch_slug>/<run_id>.md.
• _shared/review_with_cli.py — used only with --review-external; no fallback (required for that flag).

Deferred tool preloading

Several tools this skill uses are deferred and must be registered via ToolSearch before first call. Load them in a single query at the top of Step 1 so mid-workflow calls (especially TaskUpdate on every dispatch and AskUserQuestion on preflight failures) don't pay a round-trip:

ToolSearch(query: "select:TaskCreate,TaskUpdate,TaskList,TeamCreate,AskUserQuestion")

Workflow (orchestrator-only main thread)

The main thread reads exactly two things: the plan doc and the TaskList. It does not Grep/Read repo source — lane teammates own their files. If the main thread is reaching for Grep or Read on source files, the teammate brief was incomplete; re-brief via SendMessage.

Step 0 — Read predecessor handoff (if present)

Handoffs are keyed on the current repo so each workspace has its own slot. Resolve the predecessor path first:

REPO_ROOT=$(git rev-parse --show-toplevel 2>/dev/null)
if [ -z "$REPO_ROOT" ]; then
  REPO_KEY="_no-git-$(pwd | sha1sum | cut -c1-12)"
else
  REPO_KEY="$(basename "$REPO_ROOT")-$(printf '%s' "$REPO_ROOT" | sha1sum | cut -c1-12)"
fi
PREDECESSOR_HANDOFF="$(python3 - <<'PYH'
from pathlib import Path
repo = Path.cwd().resolve()
skill = "<harness>-plan-phase"
try:
    # Primary: the installed phase_loop_runtime.skill_paths resolver.
    from phase_loop_runtime.skill_paths import resolve_handoff_root
    print(resolve_handoff_root(repo) / skill / "latest.md")
except Exception:
    # Fallback: the repo-local handoff_path.py mirror, only when the runtime is not importable.
    from importlib import util
    spec = util.spec_from_file_location("handoff_path", repo / "shared" / "phase-loop" / "handoff_path.py")
    mod = util.module_from_spec(spec)
    spec.loader.exec_module(mod)
    print(mod.resolve_handoff_path(repo, skill))
PYH
)"

If $PREDECESSOR_HANDOFF exists, Read it in full — <harness>-plan-phase just produced the lane plan and may have flagged gotchas the dispatch loop needs to know about.

Defense-in-depth checks (the repo-key scheme prevents the common cross-project case, but these still catch symlink-shared workspaces, manual file copies, and stale handoffs):

• from: must be <harness>-plan-phase.
• Timestamp must be <7 days.
• Every artifact: path must resolve under $(git rev-parse --show-toplevel).

On any failure, flag via AskUserQuestion with [use anyway, ignore, abort].

Fold the handoff's "Open items" and "Repo-specific gotchas" into each lane teammate's brief (Step 5's Teammate brief contents) so they carry the same context without the user having to reinject it.

If absent, proceed standalone — the plan doc is authoritative either way.

Step 1 — Resolve + parse plan doc

Resolve in order: $PLAN_DOC → <plan-path> arg → default path built from $PLAN_VERSION + phase alias argument.

Read the plan doc. Parse these sections (headings are stable IDs from <harness>-plan-phase):

• ## Interface Freeze Gates — list of IF-0-<PHASE>-<N> items with descriptions.
• ## Cross-Repo Gates (optional) — IF-XR-<N>.
• ## Lane Index & Dependencies — machine-readable DAG block (SL-N, Depends on:, Blocks:, Parallel-safe:).
• ## Lanes — per-lane: Scope, Owned files, Interfaces provided, Interfaces consumed, task table.
• ## Verification — final end-to-end commands.

Build the lane graph. Topologically sort it; reject on cycle with a clear error.

Step 2 — Preflight

• Run scripts/verify_harness.sh <merge-target>. Enforces the hard gates: git + git-worktree available, inside a work tree, merge-target branch exists locally, working tree clean (allowlist: .claude/worktrees/, .claude/<harness>-execute-phase-state.json), .gitignore covers worktree paths. Non-zero exit blocks dispatch. On dirty-tree failure, invoke AskUserQuestion with [commit the changes as a chore, stash for the duration of the phase, abort /<harness>-execute-phase] and take the user's answer. No override.
• Record merge target = current branch (or $EXECUTE_MERGE_TARGET).
• Merge-target safety gate (before any lane dispatch or merge). If the resolved merge target is main or a protected branch, STOP — do not dispatch lanes or run any git merge onto it. Interactive: check out / create a dedicated feature branch first and re-resolve the merge target; runner/adapter: the runner resolves a runner-managed branch. This gate precedes Step 7's auto-merge, which would otherwise mutate main directly.
• Sanity check: every symbol appearing in any lane's Interfaces consumed must either be produced by an upstream lane's Interfaces provided OR be pre-existing (skip unknown symbols with a warning, don't hard-fail).
• Producer-dependency check: if a lane consumes another lane's findings, interfaces, or artifacts, that producer lane must appear in Depends on. If a lane writes a synthesized artifact, it must be downstream of every producer lane it summarizes. Missing dependencies block execution until the plan is corrected.
• If --dry-run: print the topological schedule with per-lane model/thinking assignments (see Step 3) and stop here.

Step 2.5 — Baseline-capture

Run the plan's full regression command once at phase start against the pre-phase tip. Cache the failing-test list to .claude/<harness>-execute-phase-state.json#baseline_fails. Step 9 diffs against this cached list rather than reconstructing it.

Before hypothesizing test pollution on a post-merge failure, run the failing test in isolation (fresh process) to distinguish a direct regression from fixture pollution.

Step 2a — Worktree hygiene preflight

Prune stale worktrees in .claude/worktrees/ at phase start. Skip on --resume.

bash "$(git rev-parse --show-toplevel)/.claude/skills/<harness>-execute-phase/scripts/sweep_stale_worktrees.sh"
# Pass --dry-run to preview decisions without removing anything.

For each worktree marked PRUNE:

1. git worktree unlock <path> (succeeds silently if unlocked).
2. git worktree remove -f -f <path> — double-force bypasses both the lock and the unmerged-changes check (safe since the ancestor check already confirmed incorporation).
3. git branch -D <branch> only if the branch name matches an auto-named pattern (worktree-*, phase/*/sl-*). Leave human-named branches (skills/*, feature/*, fix/*) intact even when their work is on the merge target — the user may still want the reference.

Worktrees marked KEEP are left alone; log a one-line warning per worktree.

Step 3 — Assign model + thinking per lane

Each lane gets a model and thinking level matched to its complexity. The assignment is encoded on the Agent call via model: and communicated as guidance in the brief.

Apply in order, first match wins:

1. Lane has Execution hint: <tier>/<thinking> inside its ### SL-N section → use it verbatim.
2. Lane publishes any IF-0-* gate (contract-authoring) → strong / high. Downstream lanes depend on the symbols being correct.
3. Lane scope mentions migrations, schema, or SQL → strong / high. Bad migrations are expensive to unwind.
4. Lane scope mentions algorithmic/computed logic AND has tests as first task → strong / medium.
5. Lane owns >10 files AND publishes no interfaces (wiring / mechanical refactor) → fast / low.
6. Lane implements small components against already-frozen types → fast / low.
7. Default fallback → strong / medium.

Resolve tier → model from the Model tiers table at the top of this skill and pass the concrete model ID to Agent(model: …).

Retry escalation (after a lane's first failure):

• fast → strong
• strong → frontier
• frontier → stay at frontier
• Thinking level bumps up one tier (low → medium → high).

Agent does not expose a direct thinking-level parameter — convey it in the brief's framing (e.g., "Think carefully before editing shared type definitions" vs "These are mechanical edits; move quickly").

Step 4 — TeamCreate

Preflight (before any Agent or TeamCreate call). Flush inherited team context from a predecessor skill run via TeamList (or a defensive TeamDelete). On the error signature "already leading team X", TeamDelete the stale team and retry with a repo-scoped suffix — e.g., the short hash of $(git rev-parse --show-toplevel) — to prevent cross-project team-name collisions. Same-aliased phases from different repos collide on the global team namespace without a suffix. Error signature "Team X does not exist" on TeamDelete is a no-op; proceed.

Create one team for the phase:

• Team name: phase-<PHASE_ALIAS> (e.g., phase-p1), with repo-scoped suffix appended when collision is detected.
• Teammates: one per lane, subagent_type: "general-purpose". Teammate names use the allocator — see Step 5.

TeamCreate registration enables SendMessage retry rounds without fresh Agent spawns.

Step 5 — Dispatch loop

State per lane: pending | running | verify-ok | merged | failed. State per gate: open | closed.

Repeat until all lanes are merged or halt is triggered:

1. Find ready lanes — pending lanes whose upstream lanes are all merged AND all consumed IF-0-* gates are closed. Synthesized artifact writer lanes are ready only after every producer lane named in Interfaces consumed is merged. Cap the dispatch batch at EXECUTE_MAX_PARALLEL_LANES (default 4). Slice the eligible set to the first N (lower SL-ID first) and queue the rest.

2. Allocate worktree names. For each ready lane, run scripts/allocate_worktree_name.sh <sl-id>. Substitute the emitted name (e.g., lane-sl-1-20260418T144536-nxz5) into both Agent(name=…) and the briefed EnterWorktree(name=…). Bare lane-<sl-id> names collide under rapid dispatch.

3. Dispatch in parallel — single message with one Agent(team_name: "phase-<alias>", name: "<allocated-name>", subagent_type: "general-purpose", model: "<assigned>") call per ready lane. Sequential dispatch within a wave is a bug. Do NOT pass isolation: "worktree" when team_name is set — the harness drops isolation in that combination. Use team_name for coordination + teammate-called EnterWorktree for filesystem isolation.

4. Teammate brief contains:

   • Worktree isolation (mandatory, first tool call): Load EnterWorktree via ToolSearch(query="select:EnterWorktree,ExitWorktree") if not already in the tool registry. Call ExitWorktree(action="keep") FIRST (no-op if no session active; clears any stale session-state flag inherited from a prior teammate). Then call EnterWorktree(name: "<allocated-name>") as the very next tool call, BEFORE any file operation. Every subsequent edit/commit goes into that worktree. At the end, call ExitWorktree(action: "keep") so the worktree and branch remain available for the orchestrator to merge.
   • The full ### SL-N section copied verbatim from the plan doc.
   • Architecture context (1–2 sentences): how this lane fits the phase; how this phase fits the roadmap.
   • Related files the lane reads but does not own: type defs, test fixtures, shared config. Distinct from Owned files.
   • Concrete upstream artifact paths (populated from now-merged upstream lanes) for every entry in Interfaces consumed.
   • The merge target branch and the orchestrator's current tip SHA, injected as <TIP_SHA> (used by the stale-base check below).
   • The lane's test → impl → verify task list. The lane's verify command must include regression files listed in the plan's ## Verification section that reference this lane's owned files, not only the lane's new tests. Each lane must enumerate tests that mock or stub any existing public function the lane's scope adds a call to, and include those tests in verify.
   • Thinking-level guidance matching the lane's profile.
   • Stale-base discipline: AFTER EnterWorktree returns and BEFORE any code change, run git rebase main (or git merge main --no-ff -m "merge: incorporate prior-lane foundation"). Verify with git merge-base --is-ancestor <TIP_SHA> HEAD && echo OK || echo STALE. Repeat the rebase immediately before your final commit. On conflicts, STOP and report — do not resolve silently. Never git reset --hard or git checkout HEAD~N -- … in a stale worktree; this destroys peer-lane work on --no-ff merge.
   • Staging discipline: Forbid git add -A and git add .. Stage with explicit pathspecs drawn from the lane's Owned files.
   • No self-merge: DO NOT run git merge or git push against the merge-target branch yourself; the orchestrator owns merges.
   • Structured-reply instruction: "When done, reply with JSON {lane, verify_exit_code, failed_tasks, pre_existing_failures, tsc_error_delta, notes, commit_sha, branch, worktree_path}. failed_tasks lists failures attributable to this lane; pre_existing_failures lists failures reproducible on the base SHA (capture the base-SHA reproduction command as evidence). When the lane's verify chain runs whole-repo type-checking, populate tsc_error_delta (errors-after minus errors-before); accept tsc_error_delta <= 0 as a pass even if raw exit code is non-zero. branch and worktree_path come from EnterWorktree's return value."

   Apply the /<harness>-task-contextualizer checklist to every brief.

5. Await completions. For each:

   • verify_exit_code == 0 → run gate verification (Step 6). On green → auto-merge (Step 7). Mark lane merged, flip produced gates to closed, update the lane's TaskCreate'd task to completed.

   • Non-zero or gate failure → retry-once (Step 8).

   • Idle without JSON reply → handle per the decision table below. After one SendMessage retry with no response in a reasonable interval, escalate directly to SHA-discovery rather than continuing to ping.

     Case	Condition	Action
     (a)	Idle + no commits	SendMessage one nudge requesting commit + envelope.
     (b)	Idle + commit on identifiable lane branch	Treat the commit as the result; run Step 6.5 / Step 7 audits; proceed on CLEAN.
     (c)	Idle + multiple candidate commits	One more SendMessage; if no response, halt for user.
     (d)	Idle + commits landed on merge-target directly	Route to PARENT_ON_MERGE_TARGET verdict (Step 6.5).

6. Persist lane + gate state to .claude/<harness>-execute-phase-state.json after every transition (enables --resume).

Step 6 — Gate verification

For each gate the lane provides:

1. If the plan doc's ## Verification section has a command that names this gate's artifact (e.g., psql for schema gates, grep for symbol gates), run it against the lane's worktree.
2. Else fall back:
   • Files listed under Owned files exist.
   • Symbols listed under Interfaces provided are grep-visible at expected paths.
   • Lane's own verify command exited 0.

Any failure here counts as a lane failure and triggers retry-once.

Step 6.5 — Parent-tree leakage check

Detects two isolation failure modes before merge: (a) teammate writes landing in the parent checkout, (b) EnterWorktree falling back to in-place branch creation on the parent.

Run:

bash scripts/parent_tree_leakage_check.sh <lane-id> <owned-globs-file> <merge-target>

Verdicts (emitted on stdout; details on stderr):

• CLEAN — proceed to Step 7.
• LEAKAGE_DETECTED (dirty files overlap the lane's owned globs):
  1. Verify byte-equality: for each leaked path, git diff <lane-sha> -- <path> must be zero lines (confirms the leak is a redundant copy of committed lane work). If non-zero, treat as independent uncommitted work and STOP.
  2. Clean the parent: git checkout -- <modified> for tracked changes; rm <untracked> for new files. Do NOT git stash.
  3. Record in .claude/<harness>-execute-phase-state.json under the lane's notes.
  4. Proceed to Step 7.
• UNRELATED_DIRTY_TREE (dirty files outside the lane's globs) → STOP. Ask via AskUserQuestion whether to stash, commit, or abort.
• PARENT_ON_WRONG_BRANCH (tree clean but parent on a non-merge-target branch — EnterWorktree fell back to in-place branch creation):
  1. Merge by SHA per Step 7.
  2. Run git checkout <merge-target> in the parent BEFORE Step 7's worktree cleanup — otherwise git worktree remove refuses.
  3. Record parent-fallback note in state.
• PARENT_ON_MERGE_TARGET (alias LANE_BYPASSED_ISOLATION) — resolve the reply envelope's commit_sha; if git merge-base --is-ancestor <sha> <merge-target> is already true before any merge step, the commit landed directly on the target via an EnterWorktree fallback:
  1. Skip the merge (already merged).
  2. Clean up the worktree and branch per Step 7's post-merge cleanup.
  3. Record the fallback in .claude/<harness>-execute-phase-state.json and note it in the close-out.

Step 7 — Auto-merge

Branch discovery. Resolve the lane's branch/worktree from the reply envelope's commit_sha via git log --oneline -1 <commit_sha> + git worktree list. Never trust the briefed branch name.

Cross-lane file-touch audit. Before the destructiveness check, run:

python scripts/audit_lane_file_touches.py <lane-sha> <plan-doc-path> <this-lane-id>

Parser contract. After matching the **Owned files**: heading, the parser walks subsequent deeper-indented bullets until the next sibling bullet or blank line and accumulates backticked tokens. Both inline form (- **Owned files**: \path/one`, `path/two`) and nested-bullet form (heading followed by - `path/one``) are supported. A unit test covering both formats ships alongside the script.

Verdicts:

• CLEAN → every touched file is within this lane's Owned files globs. Proceed.
• PEER_INTRUSION → the lane touched files owned by another lane. Stderr lists peer + files. Pause on AskUserQuestion: merge anyway, bounce the lane, or ask the teammate to revert the peer edits.
• ORPHAN_FILES → the lane touched files outside every lane's globs. Surface to user — likely plan or impl bug.

Pre-merge destructiveness check — lanes that committed against a stale base can wipe peer-lane work on --no-ff merge. Use the three-outcome script:

bash scripts/pre_merge_destructiveness_check.sh <lane-sha> <merge-target> <whitelist-path>

Where <whitelist-path> is a file (one path per line) of deletions the lane legitimately performs per its plan section; /dev/null if the lane is purely additive.

The script (or a sibling) also runs an ADDITION-side check mirroring the deletion check: flag commits that ADD more than N files (default ~50) or more than M lines outside the lane's owned globs. Out-of-scope adds surface as a verdict alongside deletions to catch lanes that wandered.

Verdicts:

• SAFE — deletion list empty or all whitelisted. Merge with git merge --no-ff <lane-sha>.
• STALE_BASE_DETECTED — lane branched from a pre-peer-merge main but did not actively delete. Preview, then finalize with the 3-way merge:

  git merge --no-ff --no-commit <lane-sha>
  ls <peer-lane-owned-paths>   # must exist
  git commit --no-edit
  

  Do NOT salvage — salvage loses commit lineage.
• CONFLICT — lane actively removed files. DO NOT --no-ff merge. Salvage:

  git checkout <lane-sha> -- <lane's owned paths from the plan doc>
  git commit -m "feat(<phase>,<sl-id>): <subject>
  
  Salvage of <SL-ID> lane work: lane commit was based on stale main and
  would have deleted <peer lanes' files>. Cherry-picked in-scope additions only."
  

  Count this as a successful completion — no retry.

Merge conflict (non-destructive case) → treat as lane failure: git merge --abort, surface the conflict to the teammate via SendMessage asking it to rebase inside its worktree, then retry the merge.

Post-merge import smoke — run immediately after git merge --no-ff and before dispatching the next wave:

packages="$(git diff --name-only HEAD~..HEAD \
    | grep '__init__\.py$' \
    | sed 's|/__init__\.py$||; s|/|.|g' \
    | sort -u)"
if [[ -n "$packages" ]]; then
    bash scripts/post_merge_import_smoke.sh $packages
fi

On non-zero exit, the merge broke package load. Unwind with git reset --hard HEAD~, then retry per Step 8. Second failure halts the phase.

Post-merge cleanup. First, cd "$(git rev-parse --show-toplevel)" so subsequent Bash calls survive. Then git worktree remove --force any worktrees the lane used. git branch -D (not -d) every lane branch — salvaged work leaves branches unreachable from the merge target. If Step 6.5 returned PARENT_ON_WRONG_BRANCH, git checkout <merge-target> in the parent BEFORE removing worktrees.

Step 8 — Retry-once, then halt

On first failure for a lane, decide between SendMessage-resume and kill-and-respawn based on whether the lane committed anything:

• commit_sha empty AND verify_exit_code != 0 (teammate STOPped during preflight, no work done): kill via TaskStop and re-Agent-spawn fresh. Never resume a STOPped teammate with no commits — the worktree may be reaped and the resumed instance writes into the parent.
• commit_sha populated AND verify failed (teammate did work but it broke): re-address the same named teammate via SendMessage to preserve branch-state context.

In either case, the brief includes: the failure log, the escalated model+thinking hint, and the instruction to fix the failing task and re-run verify.

On second failure:

• Cancel all still-running lane Agents via their task IDs.
• Emit a diagnostic report naming the failing lane, the failing task, the last ~30 log lines, and which lanes were merged vs pending.
• Persist state to .claude/<harness>-execute-phase-state.json and exit cleanly. User can fix and re-run with --resume.

Step 9 — Final verification, cleanup, and summary

After all lanes merged:

1. Run every command under the plan doc's ## Verification section against the merged tree.
2. Run every assertion under ## Acceptance Criteria that can be mechanically checked.
3. Team teardown. Try TeamDelete first. If it blocks (in-process teammates ignore shutdown_request), fall back to filesystem cleanup: bash scripts/team_teardown.sh phase-<alias> (rm on the Harness home directory/teams/<team>/ + the Harness home directory/tasks/<team>/).
4. Kill leftover background processes. Run ps aux | grep -E "next dev|node.*dev" and kill any stragglers spawned by lane teammates.
5. Clean-tree verification. Run git status. After successful completion the tree must be clean (lane merges are the only changes, and they're committed). Allowlist: .claude/worktrees/, .claude/<harness>-execute-phase-state.json. Anything else → stop and surface.
6. Emit final summary:
   • Lanes merged (with merge-commit SHAs)
   • Gates closed
   • Final verification pass/fail
   • Total wall-clock duration
   • Per-lane breakdown: model used, duration, token spend, retry count
7. Mark the phase's parent TaskCreate (if one exists) as completed.

Halt exception: on Step 8 second-failure halt, .claude/<harness>-execute-phase-state.json persists for --resume. This is the documented dirty-tree exception; no commit required.

Worktree lifecycle — prune after merge (standing rule)

Standing rule: prune a lane's git worktree — and delete its now-dead branch — as soon as its PR merges. Never leave merged or abandoned worktrees behind. Step 2a and Step 7 only cover the in-run .claude/worktrees/ lanes. This rule covers the sibling worktrees under the shared workspace volume (/mnt/workspace/worktrees/<project>-<branch>, or the repo-sibling ../<project>-<branch> fallback on hosts without it) that outlive a single run. Left unpruned, these accumulate without bound — the shared volume has reached thousands of stale merged worktrees because nothing swept them.

This is a sweep, not a "delete the tree you're standing in." At closeout you have just opened this run's PR, so the current run's own branch/worktree is still unmerged — it is KEPT by the criterion below, which is exactly what you want. Run the sweep at closeout (and, cheaply, at phase start).

For each sibling worktree from git worktree list (excluding the primary checkout and this run's own worktree), classify:

• SAFE to prune — the branch is MERGED and the tree is CLEAN. MERGED means either git merge-base --is-ancestor <branch> origin/main (fetch first) OR gh pr view <branch> --json state -q .state reports MERGED. CLEAN means git -C <path> status --porcelain is empty.
• KEEP — unmerged (work not yet on origin/main and no merged PR) OR dirty (--porcelain non-empty). Leave it and log one line. This preserves the current run's own worktree and any in-flight peer work.

To prune a SAFE worktree:

1. git worktree remove --force <path>.
2. git branch -D <branch> — the branch is dead once its PR merged to origin/main, so deleting it is correct. This is distinct from Step 2a, which keeps human-named branches (skills/*, feature/*, fix/*) precisely because that case is local incorporation before the PR merges and the ref may still be wanted. Once the PR is MERGED on origin, delete the branch regardless of naming.

Permission-locked fallback (gotcha). Worktrees whose node_modules (or other build output) was installed under a different uid — e.g. CI-offload / rootless-docker runs — are permission-locked. git worktree remove --force and a plain rm -rf will FAIL with Permission denied. When removal fails on permissions, fall back to sudo rm -rf <path> (or re-run the cleanup as the installing uid), then git worktree prune to drop the now-dangling administrative entry, then git branch -D <branch>. Do not treat a permission-denied removal as "KEEP" — it is still SAFE; it just needs the elevated path.

An idempotent helper is available: bash "$(git rev-parse --show-toplevel)/.claude/skills/<harness>-execute-phase/scripts/prune_merged_worktrees.sh" (pass --dry-run to preview). It encodes exactly the MERGED+CLEAN criterion and the sudo rm -rf fallback above and is safe to re-run.

Step 9.5 — Close-out: Reflection + Handoff

Before close-out, run git status --short -- <plan_path> <roadmap_path> for every consumed or updated planning artifact. If any planning artifact is untracked or modified and the user did not explicitly forbid staging, run git add <path> for each artifact. Rerun status and report Artifact state: staged|tracked|modified|unstaged|blocked for each artifact. Do not commit unless the user explicitly asked for a commit. Repo-local handoff files are operational state: do not git add an ignored handoff alongside the plan artifact unless the plan's owned-files/allowlist explicitly includes the handoff directory; leave ignored handoffs ignored and exclude them from artifact-state reporting.

Determine the next step before final response and handoff:

• If the current phase is incomplete or verification failed, set Next phase: <current alias> - blocked: <blocker> and Next command: none - <blocker>.
• If another generated phase plan is ready, set Next phase: <next alias> - execution ready and Next command: /<harness>-execute-phase <next-alias>.
• If the roadmap has an unplanned ready phase, set Next phase: <next alias> - planning ready and Next command: /<harness>-plan-phase <next-alias>.
• If the roadmap needs extension, set Next phase: none - roadmap extension needed and Next command: /<harness>-phase-roadmap-builder.
• If all phases are complete, set Next phase: none - roadmap complete and Next command: none - roadmap complete.

Resolve paths, with an inline fallback for the reflection helper:

REFLECTION_PATH=resolve_skill_bundle_root("codex")/<harness>-execute-phase/reflections/<repo_hash>/<branch_slug>/<run_id>.md
REPO_ROOT=$(git rev-parse --show-toplevel 2>/dev/null || pwd)
REPO_LOCAL_HANDOFF=$(python3 - <<'PYH'
from pathlib import Path
repo = Path.cwd().resolve()
skill = "<harness>-execute-phase"
try:
    # Primary: the installed phase_loop_runtime.skill_paths resolver.
    from phase_loop_runtime.skill_paths import resolve_handoff_root
    print(resolve_handoff_root(repo) / skill / "latest.md")
except Exception:
    # Fallback: the repo-local handoff_path.py mirror, only when the runtime is not importable.
    from importlib import util
    spec = util.spec_from_file_location("handoff_path", repo / "shared" / "phase-loop" / "handoff_path.py")
    mod = util.module_from_spec(spec)
    spec.loader.exec_module(mod)
    print(mod.resolve_handoff_path(repo, skill))
PYH
)
mkdir -p "$(dirname "$REPO_LOCAL_HANDOFF")"
SKILL_MD=resolve_skill_bundle_root("codex")/<harness>-execute-phase/SKILL.md

Primary path — orchestrator writes inline. The orchestrator writes BOTH files directly via the Write tool using the schemas below. This is the default.

Optional alternative. The orchestrator MAY instead spawn a frontier-tier agent for fresh-context independent review. Use this only when independent review is desired.

FILE 1 — REPO-AGNOSTIC reflection → write to <REFLECTION_PATH>

# <harness>-execute-phase reflection — <ISO timestamp>

## Run context
- Skill: <harness>-execute-phase
- Timestamp: <ISO timestamp>
- Repo: <repo>
- Branch: <branch>
- Commit: <commit>
- Artifact: <artifact path if any, or none>

## What worked
- <bullet, about the SKILL's instructions>

## What didn't
- <bullet, about friction or gaps in the SKILL's instructions>

## Improvements to SKILL.md
- <specific, actionable change to the instructions>

Do NOT reference this project, codebase, filenames, or domain.

FILE 2 — REPO-SPECIFIC handoff → write to <REPO_LOCAL_HANDOFF> (per-repo slot; overwrites any prior handoff from this skill in the same repo)

<!--
  Consumer validation — before acting on this handoff:
  1. Verify `from:` matches the expected predecessor skill.
  2. Verify `timestamp:` is within the last 7 days.
  3. Verify every `artifact:` path resolves under your current
     `$(git rev-parse --show-toplevel)`. If any path points to a
     different repo, stop and surface it to the user — the handoff
     was written against a different workspace.
-->
---
from: <harness>-execute-phase
timestamp: <ISO>
artifact: <phase alias that was executed, merge-commit SHAs>
artifact_state: <staged|tracked|modified|unstaged|blocked>
next_skill: <<harness>-execute-phase|<harness>-plan-phase|<harness>-phase-roadmap-builder|none>
next_command: </<harness>-execute-phase next-alias|/<harness>-plan-phase next-alias|/<harness>-phase-roadmap-builder|none - reason>
next_phase: <next alias - status|none - reason>
---

# Handoff for the next skill

The next skill in the chain is usually `/<harness>-plan-phase` for the
subsequent phase, or `/<harness>-phase-roadmap-builder` if the user is
appending new phases to the roadmap.

## Summary
<2-3 sentences: which phase completed, how many lanes merged,
final verification state.>

## Key decisions made this run
- <numbered, one line each — salvaged commits, retry outcomes,
  which lanes needed escalated models>

## Open items for the next skill
- <concrete — e.g., "Phase P2A is next; its Interfaces consumed
  list references IF-0-P1-1 which was frozen with signature X">

## Repo-specific gotchas surfaced
- <surprises this run: slow tests, flaky browser checks,
  unexpected module coupling, quirks worth knowing>

## Files committed this run
- <merge-commit SHAs, with lane ID and brief description>

## Planning artifacts staged this run
- <path> @ <artifact_state>

## Next skill's likely scope
- <forecast of what <harness>-plan-phase / <harness>-phase-roadmap-builder will touch next>

After both files are written, in the interactive TUI path only (a human is driving), print to the user:

Phase <alias> complete. <N> lanes merged; final verification <pass|fail>. Reflection saved to <REFLECTION_PATH>. Handoff written to <REPO_LOCAL_HANDOFF>. Artifact state: <staged|tracked|modified|unstaged|blocked>.

Next phase: <next alias - status|none - reason>. Next command: <exact command or none - reason>. Recommended next step (interactive only): either run /clear to reset your context window and then invoke the next command above, or dispatch a fresh subagent (Task/Agent) to carry the next phase in clean context when this loop is skill/tool-driven. The next skill reads the handoff automatically.

/clear is a human-operated reset and applies only to the interactive TUI path above. Do not emit it in Phase-Loop Adapter (autonomous) mode — an autonomous loop has no human to run it and cannot clear its own context. In autonomous runs, continuity is the written handoff and the runner re-invokes the next phase in a fresh executor process; that fresh process is the context reset. See "Phase-Loop Adapter Mode" above.

Lane state machine

pending ──► running ──► verify-ok ──► merged
                 │                        ▲
                 └─fail─► failed ─retry─►─┘ (once)
                                 │
                                 └─fail2─► HALT

Parallelism contract

• All lanes whose dependencies are satisfied at the same time MUST be dispatched in the same message (parallel Agent tool calls), up to EXECUTE_MAX_PARALLEL_LANES.
• Lanes must not share files. The plan's lane-validation checklist guarantees disjoint ownership; -execute-phase trusts the plan and does not re-verify file-glob intersections.
• Shared generated files (e.g., barrel index files, generated types) are called out in the plan's ## Execution Notes; only the lane that lists them under Owned files may modify them.

Model selection quick-reference

Symptom in the plan doc	Assigned tier	Thinking
Scope mentions schema / migration / SQL	strong	high
Interfaces provided includes any IF-0-* gate	strong	high
Scope mentions algorithm / compute / worker logic	strong	medium
Owned files glob expands to >10 files, no interfaces provided	fast	low
Scope is "small components against frozen types"	fast	low
Execution hint: line is present in lane section	Use it verbatim	Use it verbatim
Retry	One tier up	One tier up

Resolve tier names to model IDs via the Model tiers table at the top of this skill.

Output contract

On successful completion:

1. Every lane's branch merged into the target branch with a --no-ff commit, in topological order.
2. All lane worktrees removed; lane branches deleted.
3. All TaskCreate'd lane tasks marked completed.
4. .claude/<harness>-execute-phase-state.json deleted (or the status field set to complete).
5. Team torn down via TeamDelete or team_teardown.sh.
6. Final summary message to the user.

On halt:

1. Lanes that completed remain merged; their state is preserved.
2. .claude/<harness>-execute-phase-state.json contains the failing lane's name, task, log tail, and which gates/lanes were green vs open.
3. User can /<harness>-execute-phase --resume after fixing the blocker.

Worktree layout

<repo>/
├── .claude/
│   ├── worktrees/
│   │   ├── lane-sl-1-<timestamp>-<random>/
│   │   └── …
│   └── <harness>-execute-phase-state.json

Both paths are auto-added to .gitignore in Step 2.

Teamwork posture (hard rules)

• Main thread = dispatcher. Read plan doc + TaskList + git state. Do not Grep/Read source code during execution, except for the Step 7 destructiveness check and file-touch audit.
• Parallel-by-default. Ready lanes dispatch in a single message, every round.
• Name every teammate via the allocator. Bare lane-<sl-id> names collide in rapid dispatch.
• TaskCreate tasks are the source of truth for lane status. Update them as lanes transition.
• No speculative refactoring. Lane teammates must stay within their Owned files globs; reject their work at gate verification if they wandered. Use the file-touch audit to catch this pre-merge.
• Never trust a branch name. Resolve work by commit_sha from the reply envelope.
• Never --no-ff merge without the destructiveness check.
• Never resume a STOPped teammate with no commits. Kill + respawn.
• Never override the dirty-tree preflight. verify_harness.sh is the gate. Only paths forward: (a) commit as chore:, (b) git stash push -u and restore post-phase, (c) abort.
• Never rely on implicit shell CWD. Every orchestrator git/script invocation MUST either wrap as bash -c 'cd "$(git rev-parse --show-toplevel)" && <cmd>' or pass git -C <repo-root>. git worktree remove on the shell's current CWD bricks subsequent Bash calls.

Browser verification capabilities

When a plan's ## Verification section includes Playwright/e2e commands or lane tasks ask for browser smoke-testing, run them:

• Playwright via PMCP — pmcp_invoke(tool_id="playwright::browser_navigate", ...) and related playwright::* tools. Default.
• Chrome DevTools Protocol (CDP) — low-level debugging (performance traces, CPU profiling).
• claude-in-chrome — extension-context automation only.

The PMCP Playwright server provisions on demand. If the repo lacks a Playwright config, add one in the lane rather than deferring the test.

Use phase_loop_runtime.skill_paths resolver helpers for harness skill roots, handoff roots, helper roots, and reflection roots.

Runner Verification Evidence

Before reporting a successful closeout, require the runner-owned verification artifact. The closeout must name verification_artifact_path, quote the artifact summary line, and must not report verification_status=passed unless that artifact exists and supports the executed work. Treat dependency-manifest install refresh and the full suite before closeout as runner-enforced expectations, not optional narrative checks. A blocked gate may be re-verdicted only by rerunning the originally specified runner check; proxy evidence requires a roadmap or plan amendment before the verdict changes. A prior run's terminal-summary is authoritative for reconcile-or-skip only when that closeout was accepted; a rejected or blocked prior closeout — regardless of any self-reported complete/passed — must not be reconciled against. On a re-run, re-do and re-verify the phase work from scratch rather than skipping on a stale summary.

Spec Delta Closeout

Before final closeout, choose exactly one spec_delta_closeout.v1 decision: no_spec_delta, roadmap_amendment, canonical_spec_update, governed_pipeline_refresh, mirror_cutover_required, dotfiles_skill_source_update, or human_source_judgment_required. Cite metadata-only evidence paths such as the active plan, lane closeouts, targeted pytest output, and git diff --check output. Preserve the phase plan's target surfaces and redaction_posture=metadata_only; do not include raw specification bodies, raw patch bodies, credentials, provider-supplied payloads, local environment values, or evidence-source contents. Missing or malformed spec-closeout evidence is a repairable automation blocker with blocker_class=contract_bug unless the decision is human_source_judgment_required.

Closeout

In the closeout, handoff, and final response — and in any PR/issue body or commit message this run writes — reference issues and PRs as repo#N (or owner/repo#N), never a bare #N; the fleet is multi-repo, so a lone number is ambiguous.

Manifest lifecycle

After plan validation and before lane execution, perform a best-effort plan-manifest append lifecycle update through phase_loop_runtime.plan_manifest.update_lifecycle to mark the matching type=phase entry executing with run metadata. During closeout, update the same entry to completed or failed with verification metadata, reflection metadata, produced-gate metadata, if_gates_produced, and dirty-worktree summary fields as available. if_gates_produced must list only the IF gates the active phase produces per its own plan; never carry a prior phase's gate forward into this phase's closeout. Manifest lifecycle failures are non-fatal during the dual-mode window: emit a ledger warning, mention the warning in the mandatory reflection, and preserve the existing phase closeout JSON, verification, and dirty-worktree behavior.

Closeout payload shape is defined by EmitPhaseCloseout in phase_loop_runtime/baml_src/emit_phase_closeout.baml (if that path is absent in the checkout, use the operator/prompt-supplied field contract or the installed phase_loop_runtime package — the missing vendored BAML source is not a blocker); keep skill text focused on value selection and handoff routing, not duplicated field ceremony.

Before final response, write a reflection for every non-trivial run. Write it to resolve_skill_bundle_root("codex")/<harness>-execute-phase/reflections/<repo_hash>/<branch_slug>/<run_id>.md. The reflection must include ## Run context with skill name, ISO timestamp, repo, branch, commit, and artifact path if any, followed by ## What worked, ## What didn't, and ## Improvements to SKILL.md. skip only when no artifact was produced AND no decision was made AND the run was pure inspection.

Publication mode

After verified phase work, select exactly one of three modes. Default to (a) unless a clear interactive signal is present — a run missing BOTH the adapter prompt prefix AND PHASE_LOOP_RUN_MODE is AMBIGUOUS and MUST be treated as (a) (fail safe toward the runner).

• (a) Runner-managed closeout (incl. governed mode), OR ambiguous mode. If this is the phase-loop adapter (the prompt begins with <harness>-execute-phase <plan> from a pipeline run dir), or PHASE_LOOP_RUN_MODE is set (autonomous/governed), OR neither interactive signal is clearly present, the RUNNER owns closeout and commit. Do NOT independently publish — defer entirely to runner closeout (awaiting_phase_closeout / runner commit). Publishing here would bypass the governed pre-merge review panel.
• (b) Interactive orchestrator on a clean, non-protected feature branch (a clear interactive signal, and the merge target passed the merge-target safety gate). After the Step-9 clean-tree state, push the merge-target branch and open a PR (gh pr create, --draft if dependencies remain or verification was partial/skipped, else ready) instead of leaving the lane merge only local.
• (c) Merge target is main or a protected branch. Already STOPPED at the merge-target safety gate before any lane merge — never merge lanes onto main/protected. Re-target a feature branch or take explicit instruction.

This applies only to interactive (non-runner) completion; it never overrides awaiting_phase_closeout, the runner's deliberate non-complete terminal. Allowed runner hygiene (forced lane-worktree removal, branch -D, sweep_stale_worktrees.sh) is unchanged — the destructive-op ban targets publication branches/worktrees holding unmerged work.

Draft PR early — push on first commit (visibility)

Do not let a phase branch accumulate commits only locally — that is how lanes drift 70–100 commits ahead of origin and in-flight work stays invisible. On the FIRST commit of a phase, push the branch to origin and open a DRAFT PR (gh pr create --draft); keep pushing as the phase progresses, and flip the PR to ready at closeout once verification is green. The early draft PR is the visibility contract, not a request to merge.

Respect the publication ownership above: in runner-managed / governed mode the RUNNER owns publication, so the runner performs the early push and draft-PR — do not independently publish or bypass the governed pre-merge review panel. In the interactive-orchestrator path you perform the early push + draft PR yourself on the first commit.