SKILL.md
Adopt better-result
Start with evidence, then work at the scale named by the user.
Choose the branch
- Audit branch: Use when the user requests a repository-wide audit or proposal, or has not named an implementation slice. Complete the audit branch before changing production code.
- Named-slice branch: Use when the user explicitly requests implementation of a function, module, boundary, or previously proposed slice. Limit evidence collection to that slice and its propagation path.
An approved slice from the audit branch continues through the named-slice branch.
Audit branch: repository-wide proposal
1. Establish the repository and API facts
Read the repository instructions, package manifests, source layout, test commands, and architecture documentation. Determine whether better-result is installed and which version/API is available. Prefer installed types and source over remembered APIs.
Map every production-code area before studying individual failures. Exclude generated and vendored code from the audit; inspect tests for intended behavior.
Complete when: every production-code area is listed, the validation commands are known, and the available better-result API has been verified.
2. Audit every production-code area
Follow [references/repository-audit.md](references/repository-audit.md). Trace search evidence into end-to-end failure paths, keep grouped sites accountable with counts, and record obscured paths as unknown.
Write the audit to the repository's established documentation or planning location, falling back to docs/better-result-adoption.md.
Complete when: the report satisfies the coverage and completion requirements in repository-audit.md.
3. Design the target model
Apply the failure taxonomy in [references/tagged-errors.md](references/tagged-errors.md) and make each boundary decision with [references/result-boundaries.md](references/result-boundaries.md). Add the proposed dispositions, user-facing mappings, boundary decisions, and ranked vertical migration slices to the report.
Recommend the best first slice and explain why it is bounded and valuable.
Complete when: every catalogued failure has a disposition, every boundary has a recorded codec decision, and one first slice is recommended.
4. Present the approval gate
Present the report and recommendation. The audit branch's only repository change is the report.
Complete when: the report is presented. An explicit approval of one named vertical slice starts the implementation branch; otherwise the run ends here.
Named-slice branch: implementation
1. Establish the slice and API facts
Read the repository instructions, validation commands, installed better-result API, relevant production code, and tests. Trace the named failure source through its immediate callers to its handling or transport boundary. Reuse an existing adoption report when present; otherwise retain the evidence for the implementation summary.
Complete when: the slice boundary, current behavior, failure variants, callers, side effects, and transport boundaries are accounted for, and the available API is verified.
2. Implement one vertical slice
Follow [references/vertical-slice-migration.md](references/vertical-slice-migration.md), using [references/tagged-errors.md](references/tagged-errors.md) for failure dispositions and [references/result-boundaries.md](references/result-boundaries.md) for boundary contracts. Keep the implementation within the named propagation path.
Complete when: the path is consistently Result-based from failure source to its chosen handling boundary, with every error variant handled and every control-flow seam accounted for.
3. Verify and report
Run the repository's applicable format, lint, type-check, and relevant test commands. Update an existing adoption report with completed work, deviations, discoveries, and validation evidence; otherwise include them in the user-facing summary. End after recommending the next slice.
Complete when: all applicable checks pass, or every failure is reported with evidence, and the report or summary accurately describes the repository's current state.