dev-be

name	dev-be
description	Phase 5 backend implementation — implement a child-task's server-side logic (services, persistence, endpoints) following the design docs and language conventions. Use when: implementing server-side logic for a child-task, building services/persistence/endpoints, coding against an API contract + schema, or the Phase 5 backend slice.

One-Liner

Build the thinnest server-side slice that satisfies this task's acceptance criteria — honoring the API contract and schema exactly, structured errors, no secrets — and stop at the task boundary.

Input: a child-task plan.md + the design docs (architecture/database/api). Scope: this task only (WIP=1).

Delegate framework craft to the expert. Match the project's backend stack to its expert via ../../resources/expert-skills-map.md (FastAPI/Django → fastapi-expert/django-expert, Spring Boot → spring-boot-engineer, NestJS → nestjs-expert, Rails → rails-expert, Laravel → laravel-specialist, ASP.NET → dotnet-core-expert, Next.js API → nextjs-developer) and follow it for framework idioms. This skill keeps owning the contract, schema, error model, and gates.

Implement

• Build the thinnest slice that satisfies the task's behavior and acceptance criteria.
• Follow the API contract (docs/design/api.md) and schema (docs/design/database.md) exactly.
• Apply the language guide in ../../resources/conventions/.
• Comments explain why, not what (harness rule); keep functions small and testable.
• Wire structured errors per the design's error model; no secrets in code.

Examples (Bad vs Good)

# BAD: contract drift + string-built query + secret in code
@app.post("/orders")
def create(o):
    db.exec(f"insert into orders values ('{o['id']}')")   # injection; ignores api.md shape
    return {"ok": 1}                                        # not the designed response envelope
# GOOD: validated input, parameterized, designed error model
@app.post("/orders", response_model=OrderOut)
def create(o: OrderIn):                                     # matches docs/design/api.md
    try: return svc.create_order(o)                         # parameterized in the repo layer
    except DuplicateOrder: raise HTTPError(409, code="duplicate")

Self-check before handoff

• The task's unit behavior works locally; obvious edge cases handled.
• No scope creep beyond the child-task — surface larger issues as a new feature. Gate: the task's behavior works locally against the contract/schema, with no scope creep.

Handoff

Hand to check-code-review (F08), then the selected test-* skills (the strategy frozen in plan-tasks), then harness verify. Compress inter-agent handoff notes per ../../resources/token-budget.md.