<purpose>
Execute all plans in a phase using wave-based parallel execution. Orchestrator stays lean — delegates plan execution to subagents.
</purpose>

<core_principle>
Orchestrator coordinates, not executes. Each subagent loads the full execute-plan context. Orchestrator: discover plans → analyze deps → group waves → spawn agents → handle checkpoints → collect results.
</core_principle>

<required_reading>
Read STATE.md before any operation to load project context.
</required_reading>

<process>

<step name="initialize" priority="first">
Load all context in one call:

```bash
INIT=$(node ~/.claude/get-shit-done/bin/gsd-tools.js init execute-phase "${PHASE_ARG}")
```

Parse JSON for: `executor_model`, `verifier_model`, `commit_docs`, `parallelization`, `branching_strategy`, `branch_name`, `phase_found`, `phase_dir`, `phase_number`, `phase_name`, `phase_slug`, `plans`, `incomplete_plans`, `plan_count`, `incomplete_count`, `state_exists`, `roadmap_exists`.

**If `phase_found` is false:** Error — phase directory not found.
**If `plan_count` is 0:** Error — no plans found in phase.
**If `state_exists` is false but `.planning/` exists:** Offer reconstruct or continue.

When `parallelization` is false, plans within a wave execute sequentially.
</step>

<step name="handle_branching">
Check `branching_strategy` from init:

**"none":** Skip, continue on current branch.

**"phase" or "milestone":** Use pre-computed `branch_name` from init:
```bash
git checkout -b "$BRANCH_NAME" 2>/dev/null || git checkout "$BRANCH_NAME"
```

All subsequent commits go to this branch. User handles merging.
</step>

<step name="validate_phase">
From init JSON: `phase_dir`, `plan_count`, `incomplete_count`.

Report: "Found {plan_count} plans in {phase_dir} ({incomplete_count} incomplete)"
</step>

<step name="discover_and_group_plans">
Load plan inventory with wave grouping in one call:

```bash
PLAN_INDEX=$(node ~/.claude/get-shit-done/bin/gsd-tools.js phase-plan-index "${PHASE_NUMBER}")
```

Parse JSON for: `phase`, `plans[]` (each with `id`, `wave`, `autonomous`, `objective`, `files_modified`, `task_count`, `has_summary`), `waves` (map of wave number → plan IDs), `incomplete`, `has_checkpoints`.

**Filtering:** Skip plans where `has_summary: true`. If `--gaps-only`: also skip non-gap_closure plans. If all filtered: "No matching incomplete plans" → exit.

Report:
```
## Execution Plan

**Phase {X}: {Name}** — {total_plans} plans across {wave_count} waves

| Wave | Plans | What it builds |
|------|-------|----------------|
| 1 | 01-01, 01-02 | {from plan objectives, 3-8 words} |
| 2 | 01-03 | ... |
```
</step>

<step name="execute_waves">
Execute each wave in sequence. Within a wave: parallel if `PARALLELIZATION=true`, sequential if `false`.

**For each wave:**

1. **Describe what's being built (BEFORE spawning):**

   Read each plan's `<objective>`. Extract what's being built and why.

   ```
   ---
   ## Wave {N}

   **{Plan ID}: {Plan Name}**
   {2-3 sentences: what this builds, technical approach, why it matters}

   Spawning {count} agent(s)...
   ---
   ```

   - Bad: "Executing terrain generation plan"
   - Good: "Procedural terrain generator using Perlin noise — creates height maps, biome zones, and collision meshes. Required before vehicle physics can interact with ground."

2. **Spawn executor agents:**

   Pass paths only — executors read files themselves with their fresh 200k context.
   This keeps orchestrator context lean (~10-15%).

   ```
   Task(
     subagent_type="gsd-executor",
     model="{executor_model}",
     prompt="
       <objective>
       Execute plan {plan_number} of phase {phase_number}-{phase_name}.
       Commit each task atomically. Create SUMMARY.md. Update STATE.md.
       </objective>

       <execution_context>
       @~/.claude/get-shit-done/workflows/execute-plan.md
       @~/.claude/get-shit-done/templates/summary.md
       @~/.claude/get-shit-done/references/checkpoints.md
       @~/.claude/get-shit-done/references/tdd.md
       </execution_context>

       <files_to_read>
       Read these files at execution start using the Read tool:
       - Plan: {phase_dir}/{plan_file}
       - State: .planning/STATE.md
       - Config: .planning/config.json (if exists)
       </files_to_read>

       <success_criteria>
       - [ ] All tasks executed
       - [ ] Each task committed individually
       - [ ] SUMMARY.md created in plan directory
       - [ ] STATE.md updated with position and decisions
       </success_criteria>
     "
   )
   ```

3. **Wait for all agents in wave to complete.**

4. **Report completion — spot-check claims first:**

   For each SUMMARY.md:
   - Verify first 2 files from `key-files.created` exist on disk
   - Check `git log --oneline --all --grep="{phase}-{plan}"` returns ≥1 commit
   - Check for `## Self-Check: FAILED` marker

   If ANY spot-check fails: report which plan failed, route to failure handler — ask "Retry plan?" or "Continue with remaining waves?"

   If pass:
   ```
   ---
   ## Wave {N} Complete

   **{Plan ID}: {Plan Name}**
   {What was built — from SUMMARY.md}
   {Notable deviations, if any}

   {If more waves: what this enables for next wave}
   ---
   ```

   - Bad: "Wave 2 complete. Proceeding to Wave 3."
   - Good: "Terrain system complete — 3 biome types, height-based texturing, physics collision meshes. Vehicle physics (Wave 3) can now reference ground surfaces."

5. **Handle failures:**

   **Known Claude Code bug (classifyHandoffIfNeeded):** If an agent reports "failed" with error containing `classifyHandoffIfNeeded is not defined`, this is a Claude Code runtime bug — not a GSD or agent issue. The error fires in the completion handler AFTER all tool calls finish. In this case: run the same spot-checks as step 4 (SUMMARY.md exists, git commits present, no Self-Check: FAILED). If spot-checks PASS → treat as **successful**. If spot-checks FAIL → treat as real failure below.

   For real failures: report which plan failed → ask "Continue?" or "Stop?" → if continue, dependent plans may also fail. If stop, partial completion report.

6. **Execute checkpoint plans between waves** — see `<checkpoint_handling>`.

7. **Proceed to next wave.**
</step>

<step name="checkpoint_handling">
Plans with `autonomous: false` require user interaction.

**Flow:**

1. Spawn agent for checkpoint plan
2. Agent runs until checkpoint task or auth gate → returns structured state
3. Agent return includes: completed tasks table, current task + blocker, checkpoint type/details, what's awaited
4. **Present to user:**
   ```
   ## Checkpoint: [Type]

   **Plan:** 03-03 Dashboard Layout
   **Progress:** 2/3 tasks complete

   [Checkpoint Details from agent return]
   [Awaiting section from agent return]
   ```
5. User responds: "approved"/"done" | issue description | decision selection
6. **Spawn continuation agent (NOT resume)** using continuation-prompt.md template:
   - `{completed_tasks_table}`: From checkpoint return
   - `{resume_task_number}` + `{resume_task_name}`: Current task
   - `{user_response}`: What user provided
   - `{resume_instructions}`: Based on checkpoint type
7. Continuation agent verifies previous commits, continues from resume point
8. Repeat until plan completes or user stops

**Why fresh agent, not resume:** Resume relies on internal serialization that breaks with parallel tool calls. Fresh agents with explicit state are more reliable.

**Checkpoints in parallel waves:** Agent pauses and returns while other parallel agents may complete. Present checkpoint, spawn continuation, wait for all before next wave.
</step>

<step name="aggregate_results">
After all waves:

```markdown
## Phase {X}: {Name} Execution Complete

**Waves:** {N} | **Plans:** {M}/{total} complete

| Wave | Plans | Status |
|------|-------|--------|
| 1 | plan-01, plan-02 | ✓ Complete |
| CP | plan-03 | ✓ Verified |
| 2 | plan-04 | ✓ Complete |

### Plan Details
1. **03-01**: [one-liner from SUMMARY.md]
2. **03-02**: [one-liner from SUMMARY.md]

### Issues Encountered
[Aggregate from SUMMARYs, or "None"]
```
</step>

<step name="offer_next">

**Route based on execution mode:**

**If `--gaps-only` (gap closure execution):**

```
━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
 GSD ► GAP FIXES EXECUTED
━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

Phase {X}: {Name} — gap closure plans executed.

───────────────────────────────────────────────────────────────

## ▶ Next Up

**Re-verify fixes** — confirm gaps are closed

`/clear` then `/gsd:verify-work {X}`

───────────────────────────────────────────────────────────────
```

**If normal execution (no flags):**

```
━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
 GSD ► EXECUTION COMPLETE
━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

Phase {X}: {Name} — all plans executed.

───────────────────────────────────────────────────────────────

## ▶ Next Up

**Verify what was built** — manual acceptance testing

`/clear` then `/gsd:verify-work {X}`

───────────────────────────────────────────────────────────────

**Also available:**
- `/gsd:plan-phase {X+1}` — skip verification, plan next phase
- `/gsd:complete-milestone` — if all phases done
```
</step>

</process>

<context_efficiency>
Orchestrator: ~10-15% context. Subagents: fresh 200k each. No polling (Task blocks). No context bleed.
</context_efficiency>

<failure_handling>
- **classifyHandoffIfNeeded false failure:** Agent reports "failed" but error is `classifyHandoffIfNeeded is not defined` → Claude Code bug, not GSD. Spot-check (SUMMARY exists, commits present) → if pass, treat as success
- **Agent fails mid-plan:** Missing SUMMARY.md → report, ask user how to proceed
- **Dependency chain breaks:** Wave 1 fails → Wave 2 dependents likely fail → user chooses attempt or skip
- **All agents in wave fail:** Systemic issue → stop, report for investigation
- **Checkpoint unresolvable:** "Skip this plan?" or "Abort phase execution?" → record partial progress in STATE.md
</failure_handling>

<resumption>
Re-run `/gsd:execute-phase {phase}` → discover_plans finds completed SUMMARYs → skips them → resumes from first incomplete plan → continues wave execution.

STATE.md tracks: last completed plan, current wave, pending checkpoints.
</resumption>