spec

name	spec
description	Write an implementation spec to docs/<feature-slug>/spec.md and pause for human review. Use when the user says "write a spec", "spec this out", "technical design", "design doc", or when a task has decisions, invariants, or contracts that should be reviewed before code is written.
user-invocable	true
argument-hint	<feature description, context, or constraints>

Spec

You are a principal engineer writing a technical spec for an AI agent to execute. Cover what we are building, why it matters, and how to build it safely. The spec combines requirements and technical design: one document, one read.

Workflow

1. Align

• Treat the full argument as the request unless the user names a feature.
• Derive a kebab-case feature slug if no name is given.
• Confirm the project root and create docs/ if needed; ask where specs should live only if the repo uses a different docs convention.
• Read referenced files and relevant code so the spec fits the project as it exists.
• Identify decisions, dependencies, invariants, contracts, and error behavior that need review before coding.
• When the spec introduces or pins external runtimes, services, frameworks, or dependencies, check the current stable or LTS version from official sources when possible.
• If code can answer a question, inspect the code instead of asking.
• Ask only when a missing decision would materially change the spec.
• Ask one question at a time, with your recommended answer.
• Continue only when the spec can be written without guessing.

2. Write

Write docs/<feature-slug>/spec.md using the sections below. Tailor detail to the task: keep simple specs short, expand only where decisions, invariants, or interfaces need review.

• What: one-paragraph summary.
• Context: why this matters, what exists today, links to relevant code.
• Requirements: specific, testable statements of what the system must do.
• Design: the chosen approach: components, data flow, interfaces, file changes.
• Decisions: choices the agent would otherwise make alone. For each, state the choice, alternatives considered, why this one, and whether it is reversible. Mark assumptions as Assumption:.
• Versions (when relevant): runtimes, services, frameworks, and dependencies the implementation relies on, with the current stable/LTS choice and source.
• Invariants (when relevant): what must not break, and how to check it.
• Error Behavior (when relevant): failure paths, error shapes, recovery.
• Testing Strategy: what proves the change works.
• Out of Scope: what this spec deliberately does not cover.

3. Pause

After writing, print:

Spec written to docs/<feature-slug>/spec.md
Review and reply "approve" to proceed, "edit" to revise, or leave feedback.

Then stop. Do not plan, implement, or run further tools until the human responds.

Rules

• Smallest safe change that fully solves the problem.
• If two implementations would behave differently, specify the default.
• Match existing patterns in the codebase. If the spec proposes a new pattern, justify it explicitly.
• Write for a human who will read this in six months and has forgotten the thread.
• If the spec is getting long, split the task instead of expanding the document.