brownfield-onboarding

name	brownfield-onboarding
description	Onboard an existing Spring codebase into the spec-driven workflow without blocking day one. Establish a `_baseline.json`, ratchet rules, and produce a starter design doc that reflects what the code actually looks like.
when_to_use	["User runs `/onboard` or asks \"add this workflow to my existing project\".","First feature on a repo that has no `.specs/` folder."]
authoritative_references	["docs/methodology.md",".github/skills/maven-harness-pom/SKILL.md",".github/scripts/detect-stack.sh"]

Brownfield onboarding

Goal

Reach a state where /spec works on the next feature, the harness runs green (or with documented baseline drift), and the team is not blocked by years of accumulated lint/coverage debt.

Steps

1. Detect the stack. Run .github/scripts/detect-stack.sh > .specs/_stack.json. Record:

   • Java version, Spring Boot version
   • DB engine (Postgres/MySQL/H2/…)
   • Migration tool (Flyway/Liquibase/none/both)
   • Test stack (JUnit 4 vs 5, Testcontainers presence)
   • Build tool (Maven only for now)
   • OpenAPI spec presence

2. Run the harness once, capture baselines.

   .github/scripts/harness.sh --baseline > .specs/_baseline.json
   

   Result is committed:

   {
     "captured_at": "2026-04-18T10:00:00Z",
     "git_sha": "abc1234",
     "checkstyle": { "violations": 412 },
     "spotbugs": { "high": 3, "medium": 27, "low": 88 },
     "jacoco": { "overall_line": 0.71, "overall_branch": 0.58 },
     "pit": { "kill_rate": 0.46, "scope": "incremental" },
     "archunit": { "violations": 18 },
     "openapi": { "present": false },
     "dependency_check": { "high": 1, "critical": 0 }
   }
   

3. Add missing harness layers to the POM. Use maven-harness-pom skill. Pin to current values, not the targets:

   • JaCoCo <minimum> set to current minus 1% (ratchet).
   • PIT enabled in a profile (-Ppit), incremental scope only.
   • ArchUnit rules added with FreezingArchRule.freeze(...).
   • Spotless added in check mode for new code only initially (use <ratchetFrom>origin/main</ratchetFrom>).

4. Generate a starter design. spring-architect reads the codebase and writes .specs/_starter-design.md describing modules-as-they-are, the dominant patterns, and notable deviations. This is the reference for future feature designs ("we already do X, so a new feature should follow X unless an ADR says otherwise").

5. Document the gaps. Write .specs/_known-debt.md listing the things that fail or barely pass:

   - 18 ArchUnit violations frozen.
   - Coverage at 71% (target 90%); ratchet by +1% per feature.
   - 1 High-severity CVE waived: CVE-2024-XXXX in com.example:legacy-lib until upgrade ticket SHOP-123.
   - Field injection in 47 places; freeze ArchUnit rule, fix incrementally.
   

6. First feature. Run /spec against a small ticket. The agent reads .specs/_baseline.json and .specs/_starter-design.md and never proposes work that breaks them silently.

Ratchet policy

• Coverage: per-package thresholds raised by 1% per merged PR that touches the package.
• ArchUnit: frozen violations decrease only; never add a new violation.
• Mutation: incremental scope from day one; full-scope nightly run is informational.
• CVE waivers: every waiver has an expiry date and a tracker ticket.

Anti-patterns

• "We'll fix coverage later" without setting a ratchet number.
• Disabling a harness layer because it's noisy → lower the threshold instead, log the debt.
• Editing baselines downward without an ADR.
• Committing _baseline.json changes that lower a metric without explanation.