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build-feature

Build the requested feature as the narrowest complete vertical slice, preserving existing behavior outside the agreed scope.

This prompt follows Misbah Khursheed's Build Like This workflow: establish the user outcome and reasoning before generating implementation, then preserve that reasoning in contracts, boundaries, tests, and documentation.

Project identity and sources of truth

The repository where this prompt is installed is the host project being built. Build Like This is the engineering method used to build it, while mstack only installs and reconciles the method's resources. Do not mistake mstack or Build Like This for the host product unless project-owned sources explicitly say this repository develops mstack itself.

Project-owned docs/, decisions, executable code, and tests are the sources of truth. .mstack/templates/ are reference scaffolds that may be copied and adapted into project-owned documents; they are not requirements and do not replace docs/.

Treat the invocation arguments and current repository state as task input. Discover local instructions and relevant product, architecture, decision, contract, and test context before making material assumptions.

Method

1. Restate the user outcome, evidence/assumptions, scope, non-goals, acceptance criteria, and affected actors.
2. Inspect current behavior and identify contract, data, authorization, security, accessibility, operational, and documentation impact.
3. Resolve or expose decisions that materially change the implementation; avoid blocking on discoverable details.
4. Define backend/public contracts and state transitions before integrating clients; plan compatibility and migration where needed.
5. Implement by owning capability with validated boundaries, complete failure states, and no unrelated refactoring.
6. Test important success, validation, denial, failure, retry/concurrency, and recovery paths at the appropriate levels.
7. Run relevant type, build, lint, test, and focused operational checks; review the final diff against acceptance criteria.

Deliverables

• Working implementation and focused tests, not merely a plan or scaffold.
• Explicit contract/data/configuration/migration changes and compatibility behavior.
• Verification results plus rollout, observability, and rollback/forward-recovery notes where relevant.

Constraints

• Do not invent product behavior to fill consequential ambiguity.
• Do not make client checks the source of truth for authorization or business invariants.
• Do not claim completion while acceptance criteria or required verification remain unresolved.

Delegation and parallel safety

• For a material lifecycle task, the active lead must delegate at least one bounded specialist lane when subagents are available; prefer two or more concurrent lanes only when their evidence or file ownership is independent.
• The active lead owns acceptance criteria and final integration. Supporting agents must not recursively delegate unless explicitly promoted to lead a named lane.
• Give each delegate distinct inputs, outputs, and ownership. Serialize shared documents, contracts, schemas, migrations, deployments, external writes, and overlapping file edits.
• If subagents are unavailable, perform the named specialist passes sequentially and report the limitation; do not imply parallel verification.
• Delegation does not authorize outreach, paid resources, destructive changes, consequential external writes, or production deployment.

Finish with what changed or was decided, exact verification evidence, remaining risks, and the next decision only if one is genuinely required.

User arguments: $ARGUMENTS