skill-planner by benbrastmckie

---
name: skill-planner
description: Create phased implementation plans from research findings. Invoke when a task needs an implementation plan.
allowed-tools: Task, Bash, Edit, Read, Write
# Original context (now loaded by subagent):
#   - .claude/context/formats/plan-format.md
#   - .claude/context/workflows/task-breakdown.md
# Original tools (now used by subagent):
#   - Read, Write, Edit, Glob, Grep
---

# Planner Skill

Thin wrapper that delegates plan creation to `planner-agent` subagent.

**IMPORTANT**: This skill implements the skill-internal postflight pattern. After the subagent returns,
this skill handles all postflight operations (status update, artifact linking, git commit) before returning.
This eliminates the "continue" prompt issue between skill return and orchestrator.

## Context References

Reference (do not load eagerly):
- Path: `.claude/context/formats/return-metadata-file.md` - Metadata file schema
- Path: `.claude/context/patterns/postflight-control.md` - Marker file protocol
- Path: `.claude/context/patterns/file-metadata-exchange.md` - File I/O helpers
- Path: `.claude/context/patterns/jq-escaping-workarounds.md` - jq escaping patterns (Issue #1132)

Note: This skill is a thin wrapper with internal postflight. Context is loaded by the delegated agent.

## Trigger Conditions

This skill activates when:
- Task status is any non-terminal state (not completed, not abandoned)
- /plan command is invoked
- Implementation approach needs to be formalized

---

## Execution Flow

### Stage 1: Input Validation

Validate required inputs:
- `task_number` - Must be provided and exist in state.json
- Task status must allow planning

```bash
# Lookup task
task_data=$(jq -r --argjson num "$task_number" \
  '.active_projects[] | select(.project_number == $num)' \
  specs/state.json)

# Validate exists
if [ -z "$task_data" ]; then
  return error "Task $task_number not found"
fi

# Extract fields
task_type=$(echo "$task_data" | jq -r '.task_type // "general"')
status=$(echo "$task_data" | jq -r '.status')
project_name=$(echo "$task_data" | jq -r '.project_name')
description=$(echo "$task_data" | jq -r '.description // ""')

# Validate status (only block terminal states)
if [ "$status" = "completed" ] || [ "$status" = "abandoned" ]; then
  return error "Task is in terminal state [$status]"
fi
```

---

### Stage 2: Preflight Status Update

Update task status to "planning" BEFORE invoking subagent.

The centralized script handles state.json, TODO.md task entry status marker, and TODO.md Task Order status marker atomically:

```bash
bash .claude/scripts/update-task-status.sh preflight $task_number plan $session_id
```

If the script exits non-zero, stop execution and return error. Exit code 2 indicates state.json failure; exit code 3 indicates TODO.md failure.

---

### Stage 3: Create Postflight Marker

Create the marker file to prevent premature termination:

```bash
# Ensure task directory exists
padded_num=$(printf "%03d" "$task_number")
mkdir -p "specs/${padded_num}_${project_name}"

cat > "specs/${padded_num}_${project_name}/.postflight-pending" << EOF
{
  "session_id": "${session_id}",
  "skill": "skill-planner",
  "task_number": ${task_number},
  "operation": "plan",
  "reason": "Postflight pending: status update, artifact linking, git commit",
  "created": "$(date -u +%Y-%m-%dT%H:%M:%SZ)",
  "stop_hook_active": false
}
EOF
```

---

### Stage 3a: Calculate Artifact Number

Read `next_artifact_number` from state.json and use (current-1) since plan stays in the same round as research:

```bash
# Read next_artifact_number from state.json
next_num=$(jq -r --argjson num "$task_number" \
  '.active_projects[] | select(.project_number == $num) | .next_artifact_number // 1' \
  specs/state.json)

# Plan uses (current - 1) to stay in the same round as research
# If next_artifact_number is 1 (no research yet), use 1
if [ "$next_num" -le 1 ]; then
  artifact_number=1
else
  artifact_number=$((next_num - 1))
fi

# Fallback for legacy tasks: count existing plan artifacts
if [ "$next_num" = "null" ] || [ -z "$next_num" ]; then
  padded_num=$(printf "%03d" "$task_number")
  count=$(ls "specs/${padded_num}_${project_name}/plans/"*[0-9][0-9]*.md 2>/dev/null | wc -l)
  artifact_number=$((count + 1))
fi

artifact_padded=$(printf "%02d" "$artifact_number")
```

**Note**: Plan does NOT increment `next_artifact_number` in state.json. Only research advances the sequence. Plan uses `(current - 1)` to share the same round number as the preceding research.

---

### Stage 4: Prepare Delegation Context

**Prior plan discovery**: Find the latest existing plan file (if any) to pass as reference context.

```bash
# Discover prior plan (if any)
padded_num=$(printf "%03d" "$task_number")
prior_plan_path=$(ls -1 "specs/${padded_num}_${project_name}/plans/"*.md 2>/dev/null | sort -V | tail -1)
# prior_plan_path will be empty if no prior plans exist
```

Prepare delegation context for the subagent:

```json
{
  "session_id": "sess_{timestamp}_{random}",
  "delegation_depth": 1,
  "delegation_path": ["orchestrator", "plan", "skill-planner"],
  "timeout": 1800,
  "task_context": {
    "task_number": N,
    "task_name": "{project_name}",
    "description": "{description}",
    "task_type": "{task_type}"
  },
  "artifact_number": "{artifact_number from Stage 3a}",
  "research_path": "{path to research report if exists}",
  "prior_plan_path": "{path to latest prior plan if exists}",
  "roadmap_path": "specs/ROADMAP.md",
  "metadata_file_path": "specs/{NNN}_{SLUG}/.return-meta.json"
}
```

**Note**: The `artifact_number` field tells the agent which sequence number to use for artifact naming (e.g., `01`, `02`). Plan uses `(next_artifact_number - 1)` to share the same round as the preceding research.

---

### Stage 4b: Read and Inject Format Specification

Read the plan format file and prepare it for injection into the subagent prompt. This ensures the subagent always has the full format specification in its context, regardless of whether it reads the file itself.

```bash
format_content=$(cat .claude/context/formats/plan-format.md)
```

The format content will be included as a delimited section in the Stage 5 prompt (see below).

---

### Stage 5: Invoke Subagent

**CRITICAL**: You MUST use the **Task** tool to spawn the subagent.

**Required Tool Invocation**:
```
Tool: Task (NOT Skill)
Parameters:
  - subagent_type: "planner-agent"
  - prompt: [Include task_context, delegation_context, research_path, metadata_file_path,
             AND the format specification from Stage 4b as shown below]
  - description: "Execute planning for task {N}"
```

**Format Injection**: Include the format specification from Stage 4b in the prompt as a clearly-delimited section:

```
<artifact-format-specification>
## CRITICAL: Plan Format Requirements

You MUST follow this format specification exactly when writing the plan artifact.
Non-compliance will be caught by postflight validation.

{format_content from Stage 4b}
</artifact-format-specification>
```

Place this section AFTER the delegation context JSON and BEFORE any other instructions.

**DO NOT** use `Skill(planner-agent)` - this will FAIL.

The subagent will:
- Load planning context files
- Analyze task requirements and research
- Decompose into logical phases
- Identify risks and mitigations
- Create plan in `specs/{NNN}_{SLUG}/plans/`
- Write metadata to `specs/{NNN}_{SLUG}/.return-meta.json`
- Return a brief text summary (NOT JSON)

---

### Stage 5b: Self-Execution Fallback

**CRITICAL**: If you performed the work above WITHOUT using the Task tool (i.e., you read files,
wrote artifacts, or updated metadata directly instead of spawning a subagent), you MUST write a
`.return-meta.json` file now before proceeding to postflight. Use the schema from
`return-metadata-file.md` with status value `"planned"` and the appropriate artifact information.

If you DID use the Task tool (Stage 5), skip this stage -- the subagent already wrote the metadata.

---

## Postflight (ALWAYS EXECUTE)

The following stages MUST execute after work is complete, whether the work was done by a
subagent (Stage 5) or inline (Stage 5b). Do NOT skip these stages for any reason.

### Stage 6: Parse Subagent Return (Read Metadata File)

Read the metadata file:

```bash
metadata_file="specs/${padded_num}_${project_name}/.return-meta.json"

if [ -f "$metadata_file" ] && jq empty "$metadata_file" 2>/dev/null; then
    status=$(jq -r '.status' "$metadata_file")
    artifact_path=$(jq -r '.artifacts[0].path // ""' "$metadata_file")
    artifact_type=$(jq -r '.artifacts[0].type // ""' "$metadata_file")
    artifact_summary=$(jq -r '.artifacts[0].summary // ""' "$metadata_file")
else
    echo "Error: Invalid or missing metadata file"
    status="failed"
fi
```

---

### Stage 6a: Validate Artifact Content

If subagent status is "planned" and `artifact_path` is non-empty, validate the plan artifact against format requirements. This is **non-blocking** -- warnings are logged but do not prevent postflight from completing.

```bash
if [ "$status" = "planned" ] && [ -n "$artifact_path" ] && [ -f "$artifact_path" ]; then
    echo "Validating plan artifact..."
    if ! bash .claude/scripts/validate-artifact.sh "$artifact_path" plan --fix; then
        echo "WARNING: Plan artifact has format issues (non-blocking). Review output above."
    fi
fi
```

**Note**: The `--fix` flag attempts auto-repair of missing metadata fields. Validation failures are logged but do not block status update or git commit.

---

### Stage 7: Update Task Status (Postflight)

If subagent status is "planned", update state.json and TODO.md atomically using the centralized script:

```bash
bash .claude/scripts/update-task-status.sh postflight $task_number plan $session_id
```

If the script exits non-zero, log a warning but continue with artifact linking and git commit (postflight errors are non-blocking).

**On partial/failed**: Keep status as "planning" for resume (do not call the script).

---

### Stage 8: Link Artifacts

Add artifact to state.json with summary.

**IMPORTANT**: Use two-step jq pattern to avoid Issue #1132 escaping bug. See `jq-escaping-workarounds.md`.

```bash
if [ -n "$artifact_path" ]; then
    # Step 1: Filter out existing plan artifacts (use "| not" pattern to avoid != escaping - Issue #1132)
    jq '(.active_projects[] | select(.project_number == '$task_number')).artifacts =
        [(.active_projects[] | select(.project_number == '$task_number')).artifacts // [] | .[] | select(.type == "plan" | not)]' \
      specs/state.json > specs/tmp/state.json && mv specs/tmp/state.json specs/state.json

    # Step 2: Add new plan artifact
    jq --arg path "$artifact_path" \
       --arg type "$artifact_type" \
       --arg summary "$artifact_summary" \
      '(.active_projects[] | select(.project_number == '$task_number')).artifacts += [{"path": $path, "type": $type, "summary": $summary}]' \
      specs/state.json > specs/tmp/state.json && mv specs/tmp/state.json specs/state.json
fi
```

**Update TODO.md**: Link artifact using the automated script:

```bash
bash .claude/scripts/link-artifact-todo.sh $task_number '**Plan**' '**Description**' "$artifact_path"
```

If the script exits non-zero, log a warning but continue (linking errors are non-blocking).

---

### Stage 9: Git Commit

Commit changes with session ID:

```bash
git add -A
git commit -m "task ${task_number}: create implementation plan

Session: ${session_id}

Co-Authored-By: Claude Opus 4.5 <[email protected]>"
```

---

### Stage 10: Cleanup

Remove marker and metadata files:

```bash
rm -f "specs/${padded_num}_${project_name}/.postflight-pending"
rm -f "specs/${padded_num}_${project_name}/.postflight-loop-guard"
rm -f "specs/${padded_num}_${project_name}/.return-meta.json"
```

---

### Stage 11: Return Brief Summary

Return a brief text summary (NOT JSON). Example:

```
Plan created for task {N}:
- {phase_count} phases defined, {estimated_hours} hours estimated
- Key phases: {phase names}
- Created plan at specs/{NNN}_{SLUG}/plans/MM_{short-slug}.md
- Status updated to [PLANNED]
- Changes committed
```

---

## Error Handling

### Input Validation Errors
Return immediately with error message if task not found or status invalid.

### Metadata File Missing
If subagent didn't write metadata file:
1. Keep status as "planning"
2. Do not cleanup postflight marker
3. Report error to user

### Git Commit Failure
Non-blocking: Log failure but continue with success response.

### jq Parse Failure
If jq commands fail with INVALID_CHARACTER or syntax error (Issue #1132):
1. Log to errors.json:
```bash
jq --arg ts "$(date -u +%Y-%m-%dT%H:%M:%SZ)" \
   --arg sid "$session_id" \
   --arg msg "jq parse error in postflight artifact linking" \
   --argjson task "$task_number" \
  '.errors += [{
    "id": ("err_" + ($ts | gsub("[^0-9]"; ""))),
    "timestamp": $ts,
    "type": "jq_parse_failure",
    "severity": "medium",
    "message": $msg,
    "context": {"session_id": $sid, "command": "/plan", "task": $task, "checkpoint": "GATE_OUT"},
    "recovery": {"suggested_action": "Use two-step jq pattern from jq-escaping-workarounds.md", "auto_recoverable": true},
    "fix_status": "unfixed"
  }]' specs/errors.json > specs/tmp/errors.json && mv specs/tmp/errors.json specs/errors.json
```
2. Retry with two-step pattern (already implemented in Stage 8)

### Subagent Timeout
Return partial status if subagent times out (default 1800s).
Keep status as "planning" for resume.

---

## MUST NOT (Postflight Boundary)

After the agent returns, this skill MUST NOT:

1. **Edit source files** - All planning work is done by agent
2. **Run build/test commands** - Verification is done by agent
3. **Use research tools** - Web/codebase search is for agent use only
4. **Analyze task requirements** - Analysis is agent work
5. **Write plan files** - Artifact creation is agent work

The postflight phase is LIMITED TO:
- Reading agent metadata file
- Updating status via `update-task-status.sh` (handles state.json + TODO.md atomically)
- Linking artifacts in state.json
- Git commit
- Cleanup of temp/marker files

Reference: @.claude/context/standards/postflight-tool-restrictions.md

---

## Return Format

This skill returns a **brief text summary** (NOT JSON). The JSON metadata is written to the file and processed internally.

Example successful return:
```
Plan created for task 414:
- 5 phases defined, 2.5 hours estimated
- Covers: agent structure, execution flow, error handling, examples, verification
- Created plan at specs/414_create_planner_agent/plans/MM_{short-slug}.md
- Status updated to [PLANNED]
- Changes committed with session sess_1736700000_abc123
```

Example partial return:
```
Plan partially created for task 414:
- 3 of 5 phases defined before timeout
- Partial plan saved at specs/414_create_planner_agent/plans/MM_{short-slug}.md
- Status remains [PLANNING] - run /plan 414 to complete
```