Start Task (SAM Task Execution Helper)

You are implementing a specific task from a SAM task file.

<task_input> $ARGUMENTS </task_input>

---

Parse Arguments

• task_file_path (required): path to a plan/tasks-*.md file
• --task <id> (optional): Task ID to start (defaults to first ready task)
• --complete <id> (optional): Task ID to mark COMPLETE

---

If --complete <task-id> Provided

1. Run mcp__plugin_dh_sam__sam_state(plan="P{N}", task="T{M}", status="complete") to mark the task complete.
2. Output: Task {ID} marked as complete

---

Starting a Task

1. Read the task assignment via the SAM MCP tool:

   mcp__plugin_dh_sam__sam_read(plan="P{N}", task="T{M}")
   

   The response is a TaskAssignment JSON object containing:

   • plan.goal — the overall feature goal
   • plan.context — plan-level context manifest (architecture decisions, codebase notes)
   • task — full task details: title, requirements, constraints, acceptance criteria, verification steps
   • task.skills — skill names to load before implementing

   Use the address form P{N}/T{M} where N is the plan number and M is the task number from the --task argument.

1a. Discover plan artifacts via manifest (when issue number is known):

If the TaskAssignment JSON contains a parent_issue_number or the plan has an issue field, query the artifact manifest to discover available plan artifacts:

mcp__plugin_dh_backlog__artifact_list(issue_number=N)

If the response contains artifacts (non-empty artifacts list), use artifact_read to fetch the architect spec and feature context content:

mcp__plugin_dh_backlog__artifact_read(issue_number=N, artifact_type="architect")
mcp__plugin_dh_backlog__artifact_read(issue_number=N, artifact_type="feature-context")

Use the returned content as context for implementation instead of reading filesystem paths directly. This is especially important for worktree-isolated agents that cannot access uncommitted plan files from the root worktree.

Fallback: If artifact_list returns an empty manifest (no artifacts entries) or an error, fall back to filesystem path conventions (dh_paths.plan_dir() / "architect-{slug}.md" and dh_paths.plan_dir() / "feature-context-{slug}.md"). This ensures backward compatibility with issues that predate the artifact manifest system.

2. Select the task:
   • If --task provided, use that ID
   • Else pick the first task where status is not-started and all dependencies are resolved (check task.dependencies in the TaskAssignment)

2a. Load task-level skills (if present):

• Read task.skills from the TaskAssignment JSON (an array of skill names).
• If absent or empty, skip (backward compatible with older task files).
• For each skill name, invoke: Skill(skill="{skill-name}")
• If a skill fails to load, log a warning and continue. Do not abort task execution.
• Redundancy note: The orchestrator (/implement-feature) may also include skill-loading instructions in the delegation prompt. This is intentional redundancy — loading a skill twice is a no-op.
• Task-level skills are additive to any skills already declared in the agent definition's frontmatter.

3. Claim the task (prevents duplicate dispatch):

   Use sam_claim MCP tool. This is the ONLY permitted way to mark a task in-progress. Do NOT edit status or started fields directly with the Edit tool.

   mcp__plugin_dh_sam__sam_claim(plan="P{N}", task="T{M}")
   

   If the response contains "claimed": false:

   • The task was already claimed by another agent, or is complete, or could not be found.
   • Output the full JSON result for the orchestrator.
   • STOP. Do not proceed with implementation. Do not write the context file.
   • The orchestrator's hook will detect the stop and the task remains in its current state.

   If the response contains "claimed": true:

   • The task is claimed. status: in-progress and started: are written on disk.
   • Proceed to step 4 (write context file) and step 5 (implement).

4. Write the active-task context file (required for hook-driven updates). The context directory is resolved via dh_paths.context_dir(session_id):

# Python (preferred — uses dh_paths):
import json
from dh_paths import context_dir
ctx = context_dir(session_id="${CLAUDE_SESSION_ID}")
ctx.mkdir(parents=True, exist_ok=True)
(ctx / f"active-task-${CLAUDE_SESSION_ID}.json").write_text(
    json.dumps({"task_file_path": "{task_file_path}", "task_id": "{task_id}", "parent_issue_number": N})
)

# Shell fallback (when Python not available):
mkdir -p "$(python3 -c 'from dh_paths import context_dir; print(context_dir("${CLAUDE_SESSION_ID}"))')"
printf '%s' '{"task_file_path": "{task_file_path}", "task_id": "{task_id}", "parent_issue_number": N}' \
    > "$(python3 -c 'from dh_paths import context_dir; print(context_dir("${CLAUDE_SESSION_ID}") / "active-task-${CLAUDE_SESSION_ID}.json")')"

Omit parent_issue_number if the story issue number is not known. The hook treats absence as None and skips GitHub sync.

If parent_issue_number is known and github_issue field is set in the task YAML, call backlog_core.github.update_task_status(repo, github_issue, "in-progress") after the claim-task step to sync the in-progress status to GitHub. Failure is non-fatal — continue regardless.

5. Record divergence observations during implementation.

   While implementing, if you discover that the architect spec or feature-context describes something that does not match what you are implementing, append a divergence note to the task file under a ## Divergence Notes section.

   When to record: Record a divergence note when ALL of these hold:

   • You are implementing something that differs from what the architect spec or feature-context describes
   • The difference is not a trivial implementation detail (e.g., different variable name, different import path)
   • The difference affects the observable behavior, structure, or scope of the feature

   Divergence note format:

## Divergence Notes

### DN-1: {Brief title}

- **Plan artifact**: ~/.dh/projects/{project-slug}/plan/architect-{slug}.md, section "{section name}"
- **Plan claim**: "{quoted text from plan artifact}"
- **Actual implementation**: "{what was actually done and why}"
- **Classification**: design-refinement | intent-divergence
- **Recorded**: {ISO timestamp}

After appending a note, update divergence-notes: {count} in YAML frontmatter (or add **Divergence Notes**: {count} in legacy format).

For full artifact classification rules and divergence thresholds, see plan-artifact-lifecycle.md.

6. Commit message restriction — Fixes #N trailers are PROHIBITED in task-level commits.

   Task-level commits must NEVER include Fixes #N, Closes #N, or Resolves #N trailers. These trailers trigger automatic GitHub issue closure. Issue closure is handled exclusively by /complete-implementation in its final commit step, after all quality gates pass. Including these trailers in task commits causes premature issue closure before verification is complete.

7. Implement against the task acceptance criteria and run its verification steps.