spec-kit-tracer

A Spec-Kit extension that adds tracer bullet (vertical slice) support to your spec-driven development workflow.

What is a Tracer Bullet?

A tracer bullet is the thinnest possible end-to-end path through your system that proves every integration boundary works. Named after the military concept of tracer rounds that show where bullets are going, a tracer bullet in software:

• Implements one complete path from entry point to persistence and back
• Touches every layer in the architecture with minimal code at each
• Produces production-quality skeleton code (not a prototype — every line stays)
• Reveals integration risks before you invest in full implementation

Commands

/speckit.tracer.trace

The main command. Analyzes your spec artifacts (plan.md, tasks.md, spec.md), identifies the thinnest vertical slice, implements it bottom-up (or in the order that retires the most risk), verifies it with a real smoke test, and produces a tracer.md report.

/speckit.tracer.verify

Re-verifies an existing tracer after code changes. Checks that the integration path still works, re-runs the smoke test, and updates the report. Use before starting full implementation.

/speckit.tracer.expand

Analyzes the completed tracer and generates parallelizable work tracks from everything it deferred. Produces a phased plan showing which tracks can run concurrently.

Installation

speckit extensions install tracer

Or from this repository:

speckit extensions install https://github.com/chris-haveard/spec-kit-tracer

Configuration

After installation, optionally customize .specify/extensions/tracer/tracer-config.yml:

• construction_order — bottom-up (default), outside-in, or middle-out
• require_smoke_test — whether a passing smoke test is required (default: true)
• verification_mode — real-infrastructure or static-only
• layers — define your project's architecture layers
• scope_overrides — force-include or force-exclude specific scope items

Workflow

/speckit.specify  →  /speckit.plan  →  /speckit.tasks  →  /speckit.tracer.trace
                                                              ↓
                                                        /speckit.tracer.verify
                                                              ↓
                                                        /speckit.tracer.expand
                                                              ↓
                                                        /speckit.implement

Lifecycle Hooks

• after_tasks — suggests running a tracer after task breakdown
• before_implement — checks for an existing tracer report before full implementation

Prerequisites

This extension requires the following Spec-Kit artifacts to exist before running:

• spec.md — feature specification
• plan.md — implementation plan with architecture details
• tasks.md — task breakdown
• constitution.md — project constitution

License

MIT