Task Implementation Skill

Role: Domain-agnostic workflow skill for executing implementation tasks (profile=implementation). Loaded by plan-marshall:phase-5-execute-agent when task.profile is implementation.

Key Pattern: Agent loads this skill via resolve-workflow-skill --domain {domain} --phase implementation. Skill executes a generic workflow: understand context → plan → implement → verify. Domain-specific knowledge comes from task.skills (loaded by agent).

Contract Compliance

MANDATORY: Follow the execution contract defined in:

Contract	Location	Purpose
Task Contract	plan-marshall:manage-tasks/standards/task-contract.md	Task structure and fields
Task Format	plan-marshall:manage-tasks/standards/task-format.md	TOON file format specification

Two-Tier Skill Loading

See ref-workflow-architecture:skill-loading for the complete two-tier skill loading pattern with visual diagrams.

Summary: Agent loads Tier 1 (system skills) automatically, then Tier 2 (domain skills from task.skills). This workflow skill defines HOW the agent executes.

Input

Parameter	Type	Required	Description
plan_id	string	Yes	Plan identifier
task_number	number	Yes	Task number to execute

Output

status: success | error
plan_id: {echo}
task_number: {echo}
execution_summary:
  steps_completed: N
  steps_total: M
  files_modified: [paths]
verification:
  passed: true | false
  command: "{cmd}"
next_action: task_complete | requires_attention
message: {error message if status=error}

Workflow

Step 1: Load Task Context

Read the task file to understand what needs to be done:

python3 .plan/execute-script.py plan-marshall:manage-tasks:manage-tasks get \
  --plan-id {plan_id} \
  --number {task_number}

Extract key fields:

• domain: Domain for this task
• profile: Should be implementation
• skills: Domain skills to apply (already loaded by agent)
• description: What to implement
• steps: File paths to work on
• verification: How to verify success
• depends_on: Dependencies (should be complete)

Step 1.5: Read Compatibility Strategy

Read the compatibility approach from marshal.json project configuration:

python3 .plan/execute-script.py plan-marshall:manage-config:manage-config \
  plan phase-2-refine get --field compatibility --trace-plan-id {plan_id}

No fallback — if field not found, fail with error and abort task. This ensures project is configured correctly.

Extract compatibility from the output. Apply throughout all subsequent steps:

• breaking: Make changes directly. Remove old code, rename freely, no backward compatibility.
• deprecation: Keep old APIs/methods with @Deprecated markers. Add new code alongside old. Provide migration notes in commit messages.
• smart_and_ask: For each change that could break consumers, evaluate impact. If uncertain, ask user via AskUserQuestion before proceeding.

Step 2: Understand Context

Before implementing, understand the codebase context:

Read affected files (from steps):

# For each step (file path)
Read {step.target}  # If file exists

Read related files:

# Find related components
Grep "{component_name}" --type {language}
Glob {pattern}
Read {related_file}

Apply domain knowledge:

• Reference patterns from loaded domain skills
• Understand project conventions
• Identify dependencies and integration points

Step 3: Plan Implementation

For each step (file path), determine:

• What changes are needed
• How to apply domain skill patterns
• Order of modifications
• Integration considerations

Note: Steps are executed sequentially. No explicit "in_progress" marker needed - proceed directly to implementation.

Step 4: Implement Changes

For each step (file path):

Create new file:

Write {file_path}
# Apply patterns from domain skills
# Follow project conventions

Modify existing file:

Edit {file_path}
# Apply changes following domain skill patterns
# Maintain existing code style

Apply domain patterns:

• Use patterns from loaded skills (java-core, javascript-core, etc.)
• Follow CDI/injection patterns if applicable
• Add proper logging, error handling
• Include documentation comments

Step 5: Mark Step Complete

After each step:

python3 .plan/execute-script.py plan-marshall:manage-tasks:manage-tasks finalize-step \
  --plan-id {plan_id} \
  --task {task_number} \
  --step {N} \
  --outcome done

Step 6: Run Verification

After all steps complete, run task verification:

# Execute verification commands from task
{verification.commands[0]}
{verification.commands[1]}
...

Verification (implementation tasks verify compilability only — full test execution belongs to module_testing profile):

Execute the verification commands from task.verification.commands. Every task SHOULD have commands populated by the plan phase (copied from the deliverable).

Safety net (should never trigger in normal operation): If verification commands are missing, log a WARN and resolve from architecture:

python3 .plan/execute-script.py plan-marshall:manage-logging:manage-log \
  work --plan-id {plan_id} --level WARN --message "[VERIFY] (plan-marshall:task-implementation) TASK-{N} missing verification — falling back to architecture resolve"

python3 .plan/execute-script.py plan-marshall:manage-architecture:architecture \
  resolve --command compile --name {module} \
  --trace-plan-id {plan_id}

Step 7: Handle Verification Results

If verification passes:

python3 .plan/execute-script.py plan-marshall:manage-tasks:manage-tasks update \
  --plan-id {plan_id} \
  --number {task_number} \
  --status done

If verification fails:

1. Analyze error output
2. Identify failing component
3. Fix the issue
4. Re-run verification
5. Iterate until pass (max 3 iterations)

If still failing after 3 iterations:

python3 .plan/execute-script.py plan-marshall:manage-tasks:manage-tasks update \
  --plan-id {plan_id} \
  --number {task_number} \
  --status blocked

Note: Record details in work.log using manage-log.

Step 8: Record Lessons

On issues or unexpected patterns:

python3 .plan/execute-script.py plan-marshall:manage-lessons:manage-lesson add \
  --component "plan-marshall:task-implementation" \
  --category improvement \
  --title "{issue summary}" \
  --detail "{context and resolution}"

Valid categories: bug, improvement, anti-pattern

Step 9: Return Results

status: success
plan_id: {plan_id}
task_number: {task_number}
execution_summary:
  steps_completed: {N}
  steps_total: {M}
  files_modified:
    - {path1}
    - {path2}
verification:
  passed: true
  command: "{verification command}"
next_action: task_complete

Implementation Patterns

File Creation Pattern

1. Determine target path from step
2. Check if parent directory exists
3. Create file with proper structure
4. Apply domain patterns:
   - Package/module declaration
   - Imports/dependencies
   - Class/function structure
   - Documentation
5. Format according to project style

File Modification Pattern

1. Read existing file
2. Identify modification points
3. Apply changes using Edit tool
4. Preserve existing style
5. Update related components if needed
6. Update documentation if needed

Verification Iteration Pattern

1. Run verification command
2. If pass → complete
3. If fail → analyze output
4. Identify failing assertion/error
5. Fix specific issue
6. Re-run verification
7. Repeat (max 3 times)
8. If still failing → block task

Error Handling

Missing Dependency

If a file depends on code not yet implemented:

• Check if dependency is in later step
• If yes, reorder steps
• If no, create minimal stub and note

Verification Timeout

If verification command hangs:

• Kill after 5 minutes
• Record timeout in notes
• Try with reduced scope

Conflicting Changes

If changes conflict with existing code:

• Analyze conflict
• Prefer preserving existing behavior
• Ask for clarification if needed

Integration

Invoked by: plan-marshall:phase-5-execute-agent (when task.profile = implementation)

Skill Loading: Agent loads this skill via resolve-task-executor --profile implementation

Script Notations (use EXACTLY as shown):

• plan-marshall:manage-tasks:manage-tasks - Task operations (get, update, finalize-step)
• plan-marshall:manage-config:manage-config - Read compatibility from project config
• plan-marshall:manage-lessons:manage-lesson - Record lessons (add)

Domain Skills Applied (loaded by agent from task.skills):

• Java: pm-dev-java:java-core, pm-dev-java:java-cdi, etc.
• JavaScript: pm-dev-frontend:cui-javascript, etc.
• Apply patterns from whatever domain skills are listed in task.skills