Workflow Executor

Workflow Executor Skill (v0.6.9)

Execute looplia workflows defined in workflows/*.md files using the skills-first architecture.

When to Use

Use this skill when:

• Handling /run commands
• Executing workflow-as-markdown definitions
• Orchestrating multi-step skill workflows

CRITICAL: Task Invocation with general-purpose Subagent

v0.6.9: Using built-in general-purpose subagent for ALL workflow steps (all providers).

When executing a step with skill: {name} and mission::

{
  "subagent_type": "general-purpose",
  "description": "Execute step: {step.id}",
  "prompt": "Execute skill '{step.skill}' for step '{step.id}'.\n\n## Mission\n{step.mission}\n\n## Execution Protocol\n1. Read input files (if provided)\n2. Invoke the skill using Skill tool\n3. Execute the mission with skill context\n4. Write JSON output to the specified path using Write tool\n\n## CRITICAL: Output Writing is MANDATORY\nYOU MUST CALL THE WRITE TOOL before completing. If you don't write the file, the workflow fails.\n\n## Rules\n- ALWAYS invoke the specified skill using Skill tool\n- ALWAYS write output to the exact path using Write tool\n- NEVER return results as text - always write JSON to output file\n- NEVER spawn Task subagents - execute skills directly\n- ALWAYS include contentId in JSON outputs\n\nInput: {resolved input path}\nOutput: {step.output}\nValidation: {step.validate JSON}"
}

Example:

- id: analyze-content
  skill: media-reviewer
  mission: |
    Deep analysis of video transcript. Extract key themes,
    important quotes, and narrative structure.
  input: ${{ sandbox }}/inputs/content.md
  output: ${{ sandbox }}/outputs/analysis.json

Task tool call:

{
  "subagent_type": "general-purpose",
  "description": "Execute step: analyze-content",
  "prompt": "Execute skill 'media-reviewer' for step 'analyze-content'.\n\n## Mission\nDeep analysis of video transcript. Extract key themes, important quotes, and narrative structure.\n\n## Execution Protocol\n1. Read input files (if provided)\n2. Invoke the skill using Skill tool\n3. Execute the mission with skill context\n4. Write JSON output to the specified path using Write tool\n\n## CRITICAL: Output Writing is MANDATORY\nYOU MUST CALL THE WRITE TOOL before completing. If you don't write the file, the workflow fails.\n\n## Rules\n- ALWAYS invoke the specified skill using Skill tool\n- ALWAYS write output to the exact path using Write tool\n- NEVER return results as text - always write JSON to output file\n- NEVER spawn Task subagents - execute skills directly\n- ALWAYS include contentId in JSON outputs\n\nInput: sandbox/video-2025-01-15-abc123/inputs/content.md\nOutput: sandbox/video-2025-01-15-abc123/outputs/analysis.json\nValidation: {\"required_fields\":[\"contentId\",\"headline\",\"keyThemes\"]}"
}

Rules

• ALWAYS use subagent_type: "general-purpose" for ALL workflow steps
• NEVER use custom subagent_type per step (removed in v0.6.1)
• VALIDATE that step has both skill: and mission: fields
• REJECT steps using deprecated run: syntax

Why Per-Step Task Calls (Context Isolation)

Each Task(general-purpose) creates a separate context window:

• Isolates step processing from main agent context
• Prevents context pollution across steps
• Enables focused execution with only relevant inputs

NEVER batch multiple steps - this defeats context isolation.

Anti-Patterns

❌ WRONG - Delegating entire workflow:

{
  "description": "Execute workflow: writing-kit",
  "prompt": "Run all workflow steps..."
}

This pollutes the subagent context with ALL steps.

✅ CORRECT - One step per Task:

{
  "description": "Execute step: summary",
  "prompt": "Execute skill 'media-reviewer' for step 'summary'..."
}

Each step gets a fresh, focused context window.

Step Field Validation (v0.6.3)

Before executing a step, validate:

Input-less Capable Skills

These skills can operate without an input field:

• search - Executes search missions autonomously

Example input-less step:

- id: find-news
  skill: search
  mission: |
    Search Hacker News for today's top 3 AI stories.
    Extract title, URL, points, and brief summary.
  output: ${{ sandbox }}/outputs/news.json
  # No input field - search operates autonomously

Execution Protocol

Phase 1: Sandbox Setup

New Sandbox with Named Inputs (v0.6.3 - when --input provided):

1. Generate sandbox ID:

   {first-input-name}-{YYYY-MM-DD}-{random4chars}
   Example: video-transcript-2025-12-18-xk7m
   

2. Create folder structure:

   sandbox/{sandbox-id}/
   ├── inputs/
   │   ├── video-transcript.md  # Named input files
   │   └── user-notes.md
   ├── outputs/             # Step outputs go here
   ├── logs/                # Session logs
   └── validation.json      # Validation state
   

3. Copy each input file to inputs/{name}.md

New Sandbox with Single File (legacy - when --file provided):

1. Generate sandbox ID:

   {content-slug}-{YYYY-MM-DD}-{random4chars}
   Example: my-article-2025-12-18-xk7m
   

2. Create folder structure and copy to inputs/content.md

Input-less Sandbox (v0.6.3 - no inputs required):

For workflows using only input-less capable skills (e.g., search):

1. Generate sandbox ID from workflow name:

   {workflow-slug}-{YYYY-MM-DD}-{random4chars}
   Example: hn-reporter-2025-12-18-xk7m
   

2. Create folder structure with empty inputs/ directory

Resume Sandbox (when --sandbox-id provided):

1. Verify sandbox exists
2. Load validation.json to see completed steps
3. Continue from first incomplete step

Phase 2: Workflow Parsing

1. Read workflow file: workflows/{workflow-id}.md

2. Parse YAML frontmatter:

   name: workflow-name
   version: 1.0.0
   description: ...
   steps:
     - id: step-one
       skill: skill-name
       mission: |
         Task description...
       input: ...
       output: ...
   

3. Validate each step has skill: and mission: (reject run:)

4. Build dependency graph from needs: fields

Phase 3: Validation State

Generate validation.json (new sandbox):

{
  "workflow": "writing-kit",
  "version": "2.0.0",
  "sandboxId": "article-2025-12-18-xk7m",
  "createdAt": "2025-12-18T10:30:00Z",
  "steps": {
    "analyze-content": {
      "output": "outputs/analysis.json",
      "validated": false
    },
    "generate-ideas": {
      "output": "outputs/ideas.json",
      "validated": false
    },
    "build-writing-kit": {
      "output": "outputs/writing-kit.json",
      "validated": false
    }
  }
}

Phase 4: Dependency Resolution

Compute execution order using topological sort:

Input:
  analyze-content: { needs: [] }
  generate-ideas: { needs: [analyze-content] }
  build-writing-kit: { needs: [analyze-content, generate-ideas] }

Computed order: [analyze-content, generate-ideas, build-writing-kit]

Phase 5: Step Execution Loop

Execute steps ONE AT A TIME (context isolation):

1. Get first unvalidated step from dependency order
2. Make ONE Task(general-purpose) call for THIS step only
3. WAIT for Task completion before proceeding
4. Validate output, update validation.json
5. REPEAT for next unvalidated step
6. STOP when ALL steps are validated

MANDATORY: Each step = separate context window = separate Task call.

FOR EACH step in dependency order:
    │
    ▼
┌─────────────────────────────────────────┐
│ Check: output exists AND validated?      │
└────────────────┬────────────────────────┘
                 │
         ┌───────┴───────┐
         │               │
         ▼ YES           ▼ NO
    ┌─────────┐    ┌─────────────────────────────┐
    │ SKIP    │    │ 1. INVOKE Task tool:        │
    │ (done)  │    │    subagent_type:           │
    └─────────┘    │      "general-purpose"      │
                   │                              │
                   │ 2. Subagent invokes the      │
                   │    specified skill           │
                   │                              │
                   │ 3. VALIDATE output           │
                   │                              │
                   │ 4. UPDATE validation.json    │
                   │                              │
                   │ 5. IF FAILED: retry (max 2x) │
                   └─────────────────────────────┘

Phase 6: Task Tool Invocation

For step:

- id: analyze-content
  skill: media-reviewer
  mission: |
    Deep analysis of video transcript. Extract key themes,
    important quotes with timestamps, and narrative structure.
  input: ${{ sandbox }}/inputs/content.md
  output: ${{ sandbox }}/outputs/analysis.json
  validate:
    required_fields: [contentId, headline, keyThemes]

Invoke Task tool:

{
  "subagent_type": "general-purpose",
  "description": "Execute step: analyze-content",
  "prompt": "Execute skill 'media-reviewer' for step 'analyze-content'.\n\n## Mission\nDeep analysis of video transcript. Extract key themes, important quotes with timestamps, and narrative structure.\n\n## Execution Protocol\n1. Read input files (if provided)\n2. Invoke the skill using Skill tool\n3. Execute the mission with skill context\n4. Write JSON output to the specified path using Write tool\n\n## CRITICAL: Output Writing is MANDATORY\nYOU MUST CALL THE WRITE TOOL before completing.\n\n## Rules\n- ALWAYS invoke the specified skill using Skill tool\n- ALWAYS write output to the exact path using Write tool\n- NEVER return results as text - always write JSON to output file\n- ALWAYS include contentId in JSON outputs\n\nInput: sandbox/article-2025-12-18-xk7m/inputs/content.md\nOutput: sandbox/article-2025-12-18-xk7m/outputs/analysis.json\nValidation: {\"required_fields\":[\"contentId\",\"headline\",\"keyThemes\"]}"
}

Phase 7: Validation

After step output is written:

1. Use workflow-validator skill

2. Run validation script:

   bun .claude/skills/workflow-validator/scripts/validate.ts \
     sandbox/{id}/outputs/analysis.json \
     '{"required_fields":["contentId","headline","keyThemes"]}'
   

3. Parse result:

   {
     "passed": true,
     "checks": [
       { "name": "has_contentId", "passed": true }
     ]
   }
   

4. If passed: Update validation.json with validated: true

5. If failed: Retry step with feedback (max 2 retries)

Phase 8: Return Final Output

When step with final: true passes validation:

1. Read final artifact from sandbox/{id}/outputs/{artifact}
2. Return structured result:

   {
     "status": "success",
     "sandboxId": "article-2025-12-18-xk7m",
     "workflow": "writing-kit",
     "artifact": { ... }
   }
   

Variable Substitution (v0.6.9)

Resolve variables before passing to general-purpose subagent:

Named Inputs (v0.6.3)

Workflows can declare named inputs in their frontmatter:

inputs:
  - name: video-transcript
    required: true
    description: The video transcript to analyze
  - name: user-notes
    required: false
    description: Optional user notes

Steps reference inputs via ${{ inputs.name }}:

steps:
  - id: analyze
    skill: media-reviewer
    mission: Analyze the video content
    input: ${{ inputs.video-transcript }}
    output: ${{ sandbox }}/outputs/analysis.json

CLI provides inputs via --input:

looplia run writing-kit --input video-transcript=video.md --input user-notes=notes.md

Step Output References

input: ${{ steps.analyze-content.output }}
# Resolves to: sandbox/article-2025-12-18-xk7m/outputs/analysis.json

Error Handling

Example Execution Trace

/run writing-kit --file article.md

1. [SANDBOX] Created: sandbox/article-2025-12-18-xk7m/
   - inputs/content.md (copied)
   - validation.json (generated)

2. [WORKFLOW] Loaded: workflows/writing-kit.md
   - version: 2.0.0
   - steps: [analyze-content, generate-ideas, build-writing-kit]

3. [VALIDATE] Schema check passed
   - All steps have skill: field ✓
   - All steps have mission: field ✓
   - No deprecated run: syntax ✓

4. [ORDER] Computed: [analyze-content, generate-ideas, build-writing-kit]

5. [STEP] analyze-content
   - Task tool: subagent_type="general-purpose"
   - Skill: media-reviewer
   - Output: outputs/analysis.json
   - Validate: PASSED
   - Update: validation.json (analyze-content.validated = true)

6. [STEP] generate-ideas
   - Task tool: subagent_type="general-purpose"
   - Skill: idea-synthesis
   - Output: outputs/ideas.json
   - Validate: PASSED
   - Update: validation.json (generate-ideas.validated = true)

7. [STEP] build-writing-kit
   - Task tool: subagent_type="general-purpose"
   - Skill: writing-kit-assembler
   - Output: outputs/writing-kit.json
   - Validate: PASSED
   - Update: validation.json (build-writing-kit.validated = true)

8. [COMPLETE] Final output: writing-kit.json

File References

• Workflow definitions: workflows/*.md
• Subagent: Built-in general-purpose agent (v0.6.9)
• Skill definitions: plugins/*/skills/*/SKILL.md
• Sandbox storage: sandbox/{sandbox-id}/
• Validator script: .claude/skills/workflow-validator/scripts/validate.ts