/arn-code-execute-task

name: arn-code-execute-task
description: >-
  This skill should be used when the user says "execute task N", "run task N",
  "implement task N", "re-run task N", "retry task N", "run single task",
  or wants to execute a single specific task from the task list with optional
  review. This is for ONE task only — for executing the full plan (all tasks),
  use arn-code-execute-plan instead.
version: 0.4.0
argument-hint: "[task-number-or-description]"

Arness Execute Task

Execute a single task from the task list by spawning a `arn-code-task-executor` agent. Optionally run a `arn-code-task-reviewer` to validate the implementation before marking the task complete.

Pipeline position (this is an alternative entry point, not in the main pipeline):

arn-code-taskify -> arn-code-execute-task (single task) -> [optional] arn-code-review-implementation

Use cases:

• Re-running a failed task after manual intervention
• Testing a single phase independently
• Implementing one task without the full pipeline
• Retrying a task that was escalated during arn-code-execute-plan

Prerequisites

If no `## Arness` section exists in the project's CLAUDE.md, inform the user: "Arness is not configured for this project yet. Run `/arn-implementing` to get started — it will set everything up automatically." Do not proceed without it. Task list must exist (run `/arn-code-taskify` first).

Workflow

Step 1: Load Configuration

1. Read the project's CLAUDE.md and extract the `## Arness` section to find:

• **Plans directory** -- base path where project plans are saved
• **Code patterns** -- path to the directory containing stored pattern documentation
• **Template path** -- path to the report template set (JSON templates)
• **Template version** -- plugin version the templates were copied from (if present)
• **Template updates** -- user preference: `ask`, `auto`, or `manual` (if present)
• **Specs directory** -- path to the directory containing specification files (if present)

**Template version check:** If `Template version` and `Template updates` fields are present, run the template version check procedure documented in arn-code-save-plan Step 1 (Template Version Check) before proceeding. If `## Arness` does not contain these fields, treat as legacy and skip.

---

Step 2: Identify the Task

• If user provided a task ID or number: verify it exists in TaskList
• If user provided a description: search TaskList for a matching task
• If no task specified: show all available tasks (pending, unblocked) and ask user to choose
• Show the selected task: ID, description, status, dependencies
• If task is blocked: warn user that dependencies haven't completed, ask if they want to proceed anyway

---

Step 3: Choose Review Option

Ask (using `AskUserQuestion`):

**"Run with review gate after execution?"**

Options: 1. **Yes, review after execution** (Recommended) -- Spawn reviewer to validate 2. **No, execute only** -- Skip review, mark complete after executor finishes

If review chosen, also ask:

Ask (using `AskUserQuestion`):

**"How should Arness handle critical review findings?"**

Options: 1. **Resume executor with feedback** (Recommended) -- Resumes the original agent with its full implementation context 2. **Dispatch fresh executor with review report** -- Spawns a new executor with the review report as context

Store the choice for the execution session.

---

Step 4: Execute the Task

1. Ask the user for `PROJECT_NAME` if not provided in the trigger message 2. Verify the project directory exists:

   <plans-dir>/<PROJECT_NAME>/
   ├── INTRODUCTION.md
   ├── TASKS.md
   ├── PROGRESS_TRACKER.json
   ├── plans/PHASE_*.md
   └── reports/

If `PROGRESS_TRACKER.json` is missing, warn that progress tracking will not be available. Execution can still proceed. 3. Mark task as `in_progress` via TaskUpdate 4. Check if the project has `### Visual Testing` configured in the `## Arness` section of CLAUDE.md. If found, extract: capture script path, compare script path, baseline directory, diff threshold.

Note: Extract only the top-level fields (implicit Layer 1). Do NOT parse `#### Layer N:` subsections — multi-layer visual validation runs during `/arn-code-review-implementation`, not per-task.

5. **Determine the executor model.** First check the per-phase upgrade override:

• Read PROGRESS_TRACKER.json. Find the phase entry whose `implementation.taskId` matches the current task ID.
• If `phase.implementation.modelOverride` is non-null (e.g., `"opus"`), use that value as the `model` parameter for this dispatch. Skip the standard agent-models lookup. Emit a one-line status to the user: `Phase <N> (<phaseTitle>) executor model: <override> (upgraded — complex phase per pipeline.complex-phase-upgrade)`.
• If `phase.implementation.modelOverride` is null or the field is missing, fall through to the standard lookup: pass the model from `.arness/agent-models/code.md` as the `model` parameter (see `${CLAUDE_PLUGIN_ROOT}/skills/arn-code-ensure-config/references/ensure-config.md` "Dispatch convention" for fallback).

Then spawn `arn-code-task-executor` via the Agent tool with the determined model. Full context:

• Task ID and full task description
• Project name: `<PROJECT_NAME>`
• Project folder path: `<plans-dir>/<PROJECT_NAME>/`
• Phase plan file path (extracted from the task description)
• INTRODUCTION.md path: `<project-folder>/INTRODUCTION.md`
• Code patterns directory path: `<code-patterns-dir>/`
• Specs directory path: `<specs-dir>/` (if relevant to the task)
• Report template path: `<template-path>/`
• Visual testing config (if configured): capture script path, compare script path, baseline directory, diff threshold

6. Record the agent ID returned by the Agent tool (needed for resume mode) 7. Wait for executor to complete

---

Step 5: Review (if requested)

1. Read the executor's output to extract:

• Report file path