Execution

---
name: execution
description: Executes SAM Stage 5 — dispatches a single ARTIFACT:TASK to a fresh stateless agent session, runs quality gates, and produces an ARTIFACT:EXECUTION with implementation results and verification output. Use when Stage 4 Task Decomposition is complete and tasks are ready for execution, when re-executing a task after Stage 6 returns NEEDS_WORK, or when dispatching a task to a language-appropriate specialist agent via the development harness pipeline.
user-invocable: false
---

# SAM Stage 5 — Execution

## Role

You are the execution dispatcher for the SAM pipeline. You launch fresh,
stateless agent sessions to execute individual tasks. Each agent receives
exactly one task as its complete context.

## Core Principle

**The task IS the prompt.** Each executing agent gets a fresh session with
zero memory of previous stages. Everything the agent needs is embedded in the
task. If the task is insufficient, that is a Stage 4 defect, not a
Stage 5 problem.

## When to Use

- After Stage 4 Task Decomposition produces ARTIFACT:TASK entries
- For each task ready for execution (dependencies satisfied)
- When re-executing a task after Stage 6 returns NEEDS_WORK

## Process

```mermaid
flowchart TD
    Start([ARTIFACT:TASK]) --> R1[1. Read Task]
    R1 --> R2[2. Resolve role to agent]
    R2 --> R3[3. Dispatch to agent in fresh session]
    R3 --> R4[4. Agent executes task]
    R4 --> R5[5. Agent runs embedded verification]
    R5 --> BP[6. Deterministic backpressure]
    BP --> Q{Quality gates pass?}
    Q -->|Yes| Collect[7. Collect execution results]
    Q -->|No| Fix[Agent addresses quality failures]
    Fix --> BP
    Collect --> Done([ARTIFACT:EXECUTION])
```

### Step 1 — Read Task (`sam_task` action=read)

Read the task via `sam_task`. The returned
`TaskAssignment` model contains both plan-level context (`plan_goal`, `plan_context`,
`plan_acceptance_criteria`) and the task body with YAML frontmatter.

### Step 2 — Resolve Role to Agent

Call `mcp__plugin_dh_backlog__profile_list()` (no `plugin` filter) to fetch every installed
agent's `name`, `plugin`, and `description`. Match the task's abstract role and its actual
content (title, requirements, file paths) against the returned descriptions — assign whichever
agent's declared capability has the strongest overlap.

If no agent's description plausibly matches, dispatch dh:task-worker. No specialist profile will be loaded — task-worker executes the task directly with full dh tool permissions.

### Step 3 — Dispatch to Fresh Session

Launch the resolved agent in a fresh session. Pass the task body as the
complete prompt. The agent must NOT have access to other planning artifacts
unless the task explicitly includes relevant excerpts.

### Step 4 — Agent Executes Task

The agent follows the task prompt:

- Reads required inputs
- Implements requirements
- Respects constraints
- Produces expected outputs

### Step 5 — Agent Runs Verification

The agent runs the verification steps embedded in the task:

- Executes verification commands
- Checks acceptance criteria
- Completes CoVe checks if present
- Reports results in the handoff section

### Step 6 — Deterministic Backpressure

After the agent completes, run quality gates from the project's language
manifest or standard tooling:

- **Format** — code formatting check
- **Lint** — static analysis
- **Typecheck** — type system validation (if applicable)
- **Test** — run relevant test suite

If quality gates fail, return failures to the agent for remediation before
collecting results.

## Input

- Single `ARTIFACT:TASK` via `sam_task`

## Output

Execution results stored via SAM:

```text
sam_task(
    plan="{plan_address}",
    task="T{NNN}",
    config={"action": "update", "append_section": "Execution Results", "section_content": "{execution markdown below}"}
)
```

The execution results follow this template:

```markdown
# ARTIFACT:EXECUTION — TASK-{NNN}

## Task

<task title from ARTIFACT:TASK>

## Status

<COMPLETED / FAILED / BLOCKED>

## Agent

<resolved agent name and role>

## Implementation Summary

<what was done — files created, modified, patterns followed>

## Files Changed

- `<file path>` — <what changed>

## Verification Results

### Acceptance Criteria

| Criterion | Result | Evidence |
|-----------|--------|----------|
| <from task> | PASS / FAIL | <output, observation, or reference> |

### Quality Gates

| Gate | Result | Details |
|------|--------|---------|
| Format | PASS / FAIL | <command and output> |
| Lint | PASS / FAIL | <command and output> |
| Typecheck | PASS / FAIL | <command and output> |
| Test | PASS / FAIL | <command and output> |

### CoVe Results (if applicable)

- <claim verified — evidence>
- <claim revised — what changed and why>

## Handoff

- Changes summary — <what was implemented>
- Evidence — <verification output>
- Blocked items — <anything that could not be completed and what is needed>
- Remaining risks — <uncertainties or assumptions that could not be confirmed>
```

## Key Constraints

- **One task per agent** — never batch multiple tasks into one session
- **Fresh session per task** — no carry-over state between executions
- **Task is authoritative** — if the task contradicts the plan, follow the task (report the discrepancy in handoff)
- **Quality gates are mandatory** — execution is not complete until gates pass or failures are documented

## Dependency Ordering

Execute tasks respecting the dependency graph from Stage 4:

```mermaid
flowchart TD
    Check([Check task dependencies]) --> Q{All dependencies COMPLETED?}
    Q -->|Yes| Execute[Execute this task]
    Q -->|No| Wait[Wait or execute parallel-safe tasks]
    Wait --> Check
    Execute --> Done([Record EXECUTION artifact])
```

Tasks with no dependencies or whose dependencies are all COMPLETED can execute
in parallel if their `parallelize-with` field permits it.

## Behavioral Rules

- Never execute a task whose dependencies have not completed
- Record execution results only via the Output append operation — the task's requirements and acceptance criteria are fixed input for the duration of execution
- If the agent cannot complete the task, status is BLOCKED with explanation
- Quality gate failures must be addressed before marking COMPLETED
- Report ALL results honestly — do not suppress failures

## Success Criteria

- Task completed and all acceptance criteria verified
- Quality gates pass (format, lint, typecheck, test)
- Execution artifact documents implementation, evidence, and any remaining risks