Trellis:prep

Prep

Prepare a feature for implementation by decomposing its plan into ordered, verifiable tasks.

When to use

• "prep this for implementation", "prepare tasks", "break this into tasks"
• "what do I build first", "generate work items", "create task breakdown"
• Any request to decompose a technical plan into actionable steps or prepare work items for execution
• Called automatically by /trellis:build when tasks.json doesn't exist yet

Create an ordered task breakdown at .specs/<feature-name>/tasks.json.

Recommended effort: medium. Mechanical decomposition of the plan into ordered tasks.

Re-running this skill overwrites tasks.json, resetting all task statuses to "pending". This is how you reset an implementation.

Pre-flight

Run python3 ${CLAUDE_PLUGIN_ROOT}/scripts/validate-prereqs.py prep <feature-name> and use the specsDir value from the JSON output. Abort if the output reports missing prerequisites.

What to ask the user

If the user runs /prep without additional context:

1. Are there any ordering constraints beyond what the plan implies? (e.g., "I need the API working before the MCP layer so I can demo it")
2. Should tasks be sized for a human developer or for an AI coding agent? (This affects granularity. Agent tasks can be smaller and more mechanical. Human tasks should be more self-contained.)

Always ask these questions, even when invoked automatically from /trellis:build — the user is present and should have the chance to provide input.

Generation

After gathering all user input, spawn the task-writer agent. Pass it: the feature name, specs directory path, and all user-provided context. The agent will read prerequisite files (plan.md, spec.md, guidelines.md) and generate tasks.json.

Quality gate

After the agent completes, verify the generated tasks.json:

• Valid JSON that conforms to schemas/tasks.schema.json
• Every plan section maps to at least one task
• Every spec interface has at least one task that implements it
• Every task has a concrete "verify" field
• Tasks are ordered so that each task's dependencies are completed in earlier tasks
• No task requires reading the full plan to understand (it references specific sections)
• The first phase produces something runnable (even if minimal)
• The check field is populated from guidelines.md (or empty string if not available)