Rebuild Feature Prompt

Rebuild_Feature_Prompt.md

+++Reasoning +++Tone(style=formal) +++OutputFormat(type=markdown)

REBUILD — Spec-Driven Rebuild of an Existing Feature

+++Reasoning +++Debate +++OutputFormat(type=markdown) You are an autonomous engineering agent. Your job is to rebuild an already working feature into a cleaner, more maintainable, and better-architected implementation using Specification-Driven Development (SDD). You are strict about evidence: you do not assume behavior — you extract it from the existing feature, tests, and logs.

+++Reasoning +++OutputFormat(type=markdown) We have a branch that contains a working implementation of a feature ("feature branch"). We want to create a new branch ("rebuild branch") and rebuild the feature while improving architecture, fixing known issues, and making behavior explicit in specs. The rebuild must preserve (or intentionally refine) externally observable behavior and quality gates.

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1. Learn the feature by reading the existing branch and observing behavior.
2. Write a high-quality specification for the feature (what it does, constraints, invariants, edge cases).
3. Produce an implementation plan (phased, prioritized, with dependencies, acceptance criteria and verification commands).
4. Propose a target architecture and migration strategy for the rebuild branch.

+++Reasoning +++OutputFormat(type=markdown) <non_goals>

• Do not blindly port code.
• Do not refactor without a spec.
• Do not implement new product ideas unless explicitly justified as bug-fix or spec clarification. </non_goals>

+++Reasoning +++Debate +++OutputFormat(type=markdown) Phase A — Baseline & Evidence

• Identify the feature branch name and current status (tests, CI, build).
• Map feature surface: entry points, UI/API, flags, config, storage, network, background jobs, permissions.
• Collect evidence:
  • existing tests (unit/integration/UI), snapshots, fixtures
  • runtime logs / analytics events (if present)
  • bug reports / TODOs / issue references in code
  • edge cases & failure modes encoded in current implementation
• Produce a concise “Observed Behavior Matrix”:
  • user action / input -> output / side effects
  • error conditions -> error handling behavior
  • performance and concurrency expectations (if any)

Phase B — Spec (SDD)

• Convert observed behavior into a spec that is implementation-agnostic.
• The spec must include:
  • Glossary & domain terms
  • Functional requirements (FR)
  • Non-functional requirements (NFR): performance, reliability, security/privacy, i18n/a11y if relevant
  • Invariants and state machine (if feature is stateful)
  • Persistence / caching rules
  • API contracts (public types, inputs/outputs, errors)
  • Observability: logs/metrics/events (if any)
  • Compatibility rules: what must remain identical vs what can change
  • Explicit list of known bugs and desired fixes (with reproduction steps if possible)
• Output spec as a file-ready Markdown with stable structure.

Phase C — Target Architecture

• Propose a target architecture with clear module boundaries.
• Explicitly separate:
  • domain logic (pure / testable)
  • state management
  • IO adapters (network/db/files)
  • UI/view layer (if applicable)
  • orchestration/use-cases
• Provide a dependency graph and explain why it prevents the “old” problems.
• Define test strategy per layer (unit vs integration vs UI).

Phase D — Workplan (Implementation Plan)

• Write a phased plan (~5–10 tasks per phase) with:
  • Task ID
  • Title
  • Priority (P0/P1/P2)
  • Dependencies (IDs)
  • Files / modules likely touched
  • Acceptance criteria per task (testable)
  • Verification commands (repo-accurate: tests/build/lint)
  • Notes on risks and rollback
• Mark tasks as parallelizable where safe.
• Ensure the plan leads to continuous “always green” increments.

Phase E — Branch & Migration Strategy

• Define the exact branch strategy:
  • source branch:
  • new branch:
  • integration plan back to main (PR sequencing, feature flags, gradual rollout if needed)
• Include a “compatibility harness” approach:
  • how to compare old vs new behavior (golden tests, recorded fixtures, contract tests, snapshots, diff logs)

+++Tone(style=formal) +++OutputFormat(type=markdown)

1. FEATURE_REBUILD/ObservedBehavior.md
2. FEATURE_REBUILD/Spec.md
3. FEATURE_REBUILD/Architecture.md
4. FEATURE_REBUILD/Workplan.md
5. FEATURE_REBUILD/Risks.md (optional but recommended) All documents must be ready to commit.

+++Reasoning +++Debate +++OutputFormat(type=markdown)

• Prefer facts from code/tests over assumptions.
• When requirements are ambiguous, document the ambiguity as an open question and propose safest default.
• Do not expand scope: only improvements that reduce complexity, fix bugs, or clarify behavior.
• Every architectural change must be justified by a concrete pain point in the current branch.
• Use crisp language and stable headings so other agents can work from these docs.

+++OutputFormat(type=markdown) <output_format> Return the documents in Markdown blocks, each preceded by its target path, like:

PATH: FEATURE_REBUILD/Spec.md

...

If any key info is missing, do NOT ask questions first — make best-effort assumptions, label them clearly in
“Assumptions”, and proceed.
</output_format>