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

<core_principle>
The orchestrator's job is coordination, not execution. Each subagent loads the full execute-plan context itself. Orchestrator discovers plans, analyzes dependencies, groups into waves, spawns agents, handles checkpoints, collects results.
</core_principle>

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

<process>

<step name="load_project_state" priority="first">
Before any operation, read project state:

```bash
cat .planning/STATE.md 2>/dev/null
```

**If file exists:** Parse and internalize:
- Current position (phase, plan, status)
- Accumulated decisions (constraints on this execution)
- Blockers/concerns (things to watch for)

**If file missing but .planning/ exists:**
```
STATE.md missing but planning artifacts exist.
Options:
1. Reconstruct from existing artifacts
2. Continue without project state (may lose accumulated context)
```

**If .planning/ doesn't exist:** Error - project not initialized.
</step>

<step name="validate_phase">
Confirm phase exists and has plans:

```bash
# Match both zero-padded (05-*) and unpadded (5-*) folders
PADDED_PHASE=$(printf "%02d" ${PHASE_ARG} 2>/dev/null || echo "${PHASE_ARG}")
PHASE_DIR=$(ls -d .planning/phases/${PADDED_PHASE}-* .planning/phases/${PHASE_ARG}-* 2>/dev/null | head -1)
if [ -z "$PHASE_DIR" ]; then
  echo "ERROR: No phase directory matching '${PHASE_ARG}'"
  exit 1
fi

PLAN_COUNT=$(ls -1 "$PHASE_DIR"/*-PLAN.md 2>/dev/null | wc -l | tr -d ' ')
if [ "$PLAN_COUNT" -eq 0 ]; then
  echo "ERROR: No plans found in $PHASE_DIR"
  exit 1
fi
```

Report: "Found {N} plans in {phase_dir}"
</step>

<step name="discover_plans">
List all plans and extract metadata:

```bash
# Get all plans
ls -1 "$PHASE_DIR"/*-PLAN.md 2>/dev/null | sort

# Get completed plans (have SUMMARY.md)
ls -1 "$PHASE_DIR"/*-SUMMARY.md 2>/dev/null | sort
```

For each plan, read frontmatter to extract:
- `wave: N` - Execution wave (pre-computed)
- `autonomous: true/false` - Whether plan has checkpoints
- `gap_closure: true/false` - Whether plan closes gaps from verification/UAT

Build plan inventory:
- Plan path
- Plan ID (e.g., "03-01")
- Wave number
- Autonomous flag
- Gap closure flag
- Completion status (SUMMARY exists = complete)

**Filtering:**
- Skip completed plans (have SUMMARY.md)
- If `--gaps-only` flag: also skip plans where `gap_closure` is not `true`

If all plans filtered out, report "No matching incomplete plans" and exit.
</step>

<step name="group_by_wave">
Read `wave` from each plan's frontmatter and group by wave number:

```bash
# For each plan, extract wave from frontmatter
for plan in $PHASE_DIR/*-PLAN.md; do
  wave=$(grep "^wave:" "$plan" | cut -d: -f2 | tr -d ' ')
  autonomous=$(grep "^autonomous:" "$plan" | cut -d: -f2 | tr -d ' ')
  echo "$plan:$wave:$autonomous"
done
```

**Group plans:**
```
waves = {
  1: [plan-01, plan-02],
  2: [plan-03, plan-04],
  3: [plan-05]
}
```

**No dependency analysis needed.** Wave numbers are pre-computed during `/gsd:plan-phase`.

Report wave structure with context:
```
## 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} |
| 2 | 01-03 | {from plan objectives} |
| 3 | 01-04 [checkpoint] | {from plan objectives} |

```

The "What it builds" column comes from skimming plan names/objectives. Keep it brief (3-8 words).
</step>

<step name="execute_waves">
Execute each wave in sequence. Autonomous plans within a wave run in parallel.

**For each wave:**

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

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

   **Output:**
   ```
   ---

   ## Wave {N}

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

   **{Plan ID}: {Plan Name}** (if parallel)
   {same format}

   Spawning {count} agent(s)...

   ---
   ```

   **Examples:**
   - 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 all autonomous agents in wave simultaneously:**

   Use Task tool with multiple parallel calls. Each agent gets prompt from subagent-task-prompt template:

   ```
   <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>

   <context>
   Plan: @{plan_path}
   Project state: @.planning/STATE.md
   Config: @.planning/config.json (if exists)
   </context>

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

2. **Wait for all agents in wave to complete:**

   Task tool blocks until each agent finishes. All parallel agents return together.

3. **Report completion and what was built:**

   For each completed agent:
   - Verify SUMMARY.md exists at expected path
   - Read SUMMARY.md to extract what was built
   - Note any issues or deviations

   **Output:**
   ```
   ---

   ## Wave {N} Complete

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

   **{Plan ID}: {Plan Name}** (if parallel)
   {same format}

   {If more waves: brief note on what this enables for next wave}

   ---
   ```

   **Examples:**
   - 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."

4. **Handle failures:**

   If any agent in wave fails:
   - Report which plan failed and why
   - Ask user: "Continue with remaining waves?" or "Stop execution?"
   - If continue: proceed to next wave (dependent plans may also fail)
   - If stop: exit with partial completion report

5. **Execute checkpoint plans between waves:**

   See `<checkpoint_handling>` for details.

6. **Proceed to next wave**

</step>

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

**Detection:** Check `autonomous` field in frontmatter.

**Execution flow for checkpoint plans:**

1. **Spawn agent for checkpoint plan:**
   ```
   Task(prompt="{subagent-task-prompt}", subagent_type="general-purpose")
   ```

2. **Agent runs until checkpoint:**
   - Executes auto tasks normally
   - Reaches checkpoint task (e.g., `type="checkpoint:human-verify"`) or auth gate
   - Agent returns with structured checkpoint (see checkpoint-return.md template)

3. **Agent return includes (structured format):**
   - Completed Tasks table with commit hashes and files
   - Current task name and blocker
   - Checkpoint type and details for user
   - What's awaited from user

4. **Orchestrator presents checkpoint to user:**

   Extract and display the "Checkpoint Details" and "Awaiting" sections from agent return:
   ```
   ## Checkpoint: [Type]

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

   [Checkpoint Details section from agent return]

   [Awaiting section from agent return]
   ```

5. **User responds:**
   - "approved" / "done" → spawn continuation agent
   - Description of issues → spawn continuation agent with feedback
   - Decision selection → spawn continuation agent with choice

6. **Spawn continuation agent (NOT resume):**

   Use the continuation-prompt.md template:
   ```
   Task(
     prompt=filled_continuation_template,
     subagent_type="general-purpose"
   )
   ```

   Fill template with:
   - `{completed_tasks_table}`: From agent's checkpoint return
   - `{resume_task_number}`: Current task from checkpoint
   - `{resume_task_name}`: Current task name from checkpoint
   - `{user_response}`: What user provided
   - `{resume_instructions}`: Based on checkpoint type (see continuation-prompt.md)

7. **Continuation agent executes:**
   - Verifies previous commits exist
   - Continues from resume point
   - May hit another checkpoint (repeat from step 4)
   - Or completes plan

8. **Repeat until plan completes or user stops**

**Why fresh agent instead of resume:**
Resume relies on Claude Code's internal serialization which breaks with parallel tool calls.
Fresh agents with explicit state are more reliable and maintain full context.

**Checkpoint in parallel context:**
If a plan in a parallel wave has a checkpoint:
- Spawn as normal
- Agent pauses at checkpoint and returns with structured state
- Other parallel agents may complete while waiting
- Present checkpoint to user
- Spawn continuation agent with user response
- Wait for all agents to finish before next wave
</step>

<step name="aggregate_results">
After all waves complete, aggregate results:

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

**Waves executed:** {N}
**Plans completed:** {M} of {total}

### Wave Summary

| Wave | Plans | Status |
|------|-------|--------|
| 1 | plan-01, plan-02 | ✓ Complete |
| CP | plan-03 | ✓ Verified |
| 2 | plan-04 | ✓ Complete |
| 3 | plan-05 | ✓ Complete |

### Plan Details

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

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

<step name="verify_phase_goal">
Verify phase achieved its GOAL, not just completed its TASKS.

**Spawn verifier:**

```
Task(
  prompt="Verify phase {phase_number} goal achievement.

Phase directory: {phase_dir}
Phase goal: {goal from ROADMAP.md}

Check must_haves against actual codebase. Create VERIFICATION.md.
Verify what actually exists in the code.",
  subagent_type="gsd-verifier"
)
```

**Read verification status:**

```bash
grep "^status:" "$PHASE_DIR"/*-VERIFICATION.md | cut -d: -f2 | tr -d ' '
```

**Route by status:**

| Status | Action |
|--------|--------|
| `passed` | Continue to update_roadmap |
| `human_needed` | Present items to user, get approval or feedback |
| `gaps_found` | Present gap summary, offer `/gsd:plan-phase {phase} --gaps` |

**If passed:**

Phase goal verified. Proceed to update_roadmap.

**If human_needed:**

```markdown
## ✓ Phase {X}: {Name} — Human Verification Required

All automated checks passed. {N} items need human testing:

### Human Verification Checklist

{Extract from VERIFICATION.md human_verification section}

---

**After testing:**
- "approved" → continue to update_roadmap
- Report issues → will route to gap closure planning
```

If user approves → continue to update_roadmap.
If user reports issues → treat as gaps_found.

**If gaps_found:**

Present gaps and offer next command:

```markdown
## ⚠ Phase {X}: {Name} — Gaps Found

**Score:** {N}/{M} must-haves verified
**Report:** {phase_dir}/{phase}-VERIFICATION.md

### What's Missing

{Extract gap summaries from VERIFICATION.md gaps section}

---

## ▶ Next Up

**Plan gap closure** — create additional plans to complete the phase

`/gsd:plan-phase {X} --gaps`

<sub>`/clear` first → fresh context window</sub>

---

**Also available:**
- `cat {phase_dir}/{phase}-VERIFICATION.md` — see full report
- `/gsd:verify-work {X}` — manual testing before planning
```

User runs `/gsd:plan-phase {X} --gaps` which:
1. Reads VERIFICATION.md gaps
2. Creates additional plans (04, 05, etc.) with `gap_closure: true` to close gaps
3. User then runs `/gsd:execute-phase {X} --gaps-only`
4. Execute-phase runs only gap closure plans (04-05)
5. Verifier runs again after new plans complete

User stays in control at each decision point.
</step>

<step name="update_roadmap">
Update ROADMAP.md to reflect phase completion:

```bash
# Mark phase complete
# Update completion date
# Update status
```

Commit phase completion (roadmap, state, verification):
```bash
git add .planning/ROADMAP.md .planning/STATE.md .planning/phases/{phase_dir}/*-VERIFICATION.md
git add .planning/REQUIREMENTS.md  # if updated
git commit -m "docs(phase-{X}): complete phase execution"
```
</step>

<step name="offer_next">
Present next steps based on milestone status:

**If more phases remain:**
```
## Next Up

**Phase {X+1}: {Name}** — {Goal}

`/gsd:plan-phase {X+1}`

<sub>`/clear` first for fresh context</sub>
```

**If milestone complete:**
```
MILESTONE COMPLETE!

All {N} phases executed.

`/gsd:complete-milestone`
```
</step>

</process>

<context_efficiency>
**Why this works:**

Orchestrator context usage: ~10-15%
- Read plan frontmatter (small)
- Analyze dependencies (logic, no heavy reads)
- Fill template strings
- Spawn Task calls
- Collect results

Each subagent: Fresh 200k context
- Loads full execute-plan workflow
- Loads templates, references
- Executes plan with full capacity
- Creates SUMMARY, commits

**No polling.** Task tool blocks until completion. No TaskOutput loops.

**No context bleed.** Orchestrator never reads workflow internals. Just paths and results.
</context_efficiency>

<failure_handling>
**Subagent fails mid-plan:**
- SUMMARY.md won't exist
- Orchestrator detects missing SUMMARY
- Reports failure, asks user how to proceed

**Dependency chain breaks:**
- Wave 1 plan fails
- Wave 2 plans depending on it will likely fail
- Orchestrator can still attempt them (user choice)
- Or skip dependent plans entirely

**All agents in wave fail:**
- Something systemic (git issues, permissions, etc.)
- Stop execution
- Report for manual investigation

**Checkpoint fails to resolve:**
- User can't approve or provides repeated issues
- Ask: "Skip this plan?" or "Abort phase execution?"
- Record partial progress in STATE.md
</failure_handling>

<resumption>
**Resuming interrupted execution:**

If phase execution was interrupted (context limit, user exit, error):

1. Run `/gsd:execute-phase {phase}` again
2. discover_plans finds completed SUMMARYs
3. Skips completed plans
4. Resumes from first incomplete plan
5. Continues wave-based execution

**STATE.md tracks:**
- Last completed plan
- Current wave
- Any pending checkpoints
</resumption>
