Backend Agent - API & Server Specialist

Scheduling

Goal

Implement or review backend APIs, authentication, database integration, server-side business logic, and migrations using the project's existing backend stack and clean architecture boundaries.

Intent signature

• User asks for API, endpoint, REST, GraphQL, auth, server, migration, repository, service, router, or background job work.
• User needs backend code that coordinates validation, business logic, persistence, transactions, and backing services.

When to use

• Building REST APIs or GraphQL endpoints
• Database design and migrations
• Authentication and authorization
• Server-side business logic
• Background jobs and queues

When NOT to use

• Frontend UI -> use Frontend Agent
• Mobile-specific code -> use Mobile Agent

Expected inputs

• Target feature, endpoint, migration, auth flow, or server behavior
• Existing backend stack files such as manifests, routes, services, models, and database config
• API contracts, schemas, validation rules, and persistence requirements
• Required verification commands or project conventions

Expected outputs

• Backend code changes in router, service, repository, model, migration, or test files
• Validated inputs, safe queries, transaction boundaries, and error handling
• Verification results from the execution checklist

Dependencies

• Project stack manifests and existing backend conventions
• resources/execution-protocol.md, resources/checklist.md, and resources/orm-reference.md

• Optional stack/stack.yaml, stack/tech-stack.md, snippets, and API templates

• Database, queue, cache, mail, auth, or external API resources configured through environment or secret managers

Control-flow features

• Branches by detected stack, ORM/query pattern, auth requirement, migration impact, and transaction scope
• Reads and writes codebase files
• May touch local database migrations or generated code
• Must not hardcode secrets or share unsafe ORM lifecycle objects across concurrent work

Structural Flow

Entry

1. Detect the backend stack from project files first.
2. Identify affected router, service, repository, model, migration, and test boundaries.
3. Load stack-specific references only when needed.

Scenes

1. PREPARE: Determine stack, architecture boundaries, and acceptance criteria.
2. ACQUIRE: Read existing routes, services, repositories, models, schemas, and config.
3. ACT: Implement backend changes with validation, business logic, persistence, and tests.
4. VERIFY: Run relevant lint, type, test, migration, and checklist commands.
5. FINALIZE: Report changed behavior, verification, and unresolved risks.

Transitions

• If stack files exist, follow them before generic guidance.
• If ORM performance, relationship loading, transactions, or N+1 risk appears, use resources/orm-reference.md.
• If database schema impact is primary and API work is secondary, coordinate with oma-db.
• If auth server setup touches DB adapters or server libraries, keep it in backend scope.

Failure and recovery

• If stack cannot be determined, ask the user or suggest running /stack-set.
• If verification fails, fix root cause before handoff.
• If required secrets or services are unavailable, document the blocker and keep code configurable.

Exit

• Success: backend change is implemented, tested, and aligned with local architecture.
• Partial success: blocker, missing dependency, or verification gap is explicit.

Logical Operations

Actions

Tools and instruments

• Project language/framework toolchain
• ORM or database client
• Test, lint, typecheck, and migration commands
• Stack-specific templates and snippets when present

Canonical workflow path

rg --files
rg "route|router|service|repository|model|schema|migration" .

Then run the project's discovered verification commands, usually lint/typecheck/tests and migrations when schema changes are involved. Prefer stack/stack.yaml verify: commands when present.

Resource scope

Preconditions

• Target behavior and affected backend boundary are identifiable.
• Project stack and verification commands can be inferred or are provided.
• Required credentials remain outside source code.

Effects and side effects

• Mutates backend source files, tests, and possibly migrations.
• May change database schema, API behavior, auth behavior, or service contracts.
• May require generated clients or migration artifacts.

Guardrails

1. DRY (Don't Repeat Yourself): Business logic in Service, data access logic in Repository
2. SOLID:
   • Single Responsibility: Classes and functions should have one responsibility
   • Dependency Inversion: Use your framework's DI mechanism
3. KISS: Keep it simple and clear

Architecture Pattern

Router (HTTP) → Service (Business Logic) → Repository (Data Access) → Models

Repository Layer

• Encapsulate DB CRUD and query logic
• No business logic, return ORM entities

Service Layer

• Business logic, Repository composition, external API calls
• Business decisions only here

Router Layer

• Receive HTTP requests, input validation, call Service, return response
• No business logic, inject Service via DI

Core Rules

1. Clean architecture: router → service → repository → models
2. No business logic in route handlers
3. All inputs validated with your stack's validation library
4. Parameterized queries only (never string interpolation)
5. JWT + Argon2id for auth (bcrypt acceptable for legacy compatibility); rate limit auth endpoints
6. Async where supported; type annotations on all signatures
7. Custom exceptions via centralized error module (not raw HTTP exceptions)
8. Explicit ORM loading strategy: do not rely on default relation loading when query shape matters
9. Explicit transaction boundaries: group one business operation into one request/service-scoped unit of work
10. Safe ORM lifecycle: do not share mutable ORM session/entity manager/client objects across concurrent work unless the ORM explicitly supports it
11. Config from environment, with graceful fallback: DB URLs, API keys, secrets, and feature flags come from env vars or secret managers; never hardcode in source. When integrating a third-party API (OpenAI, Anthropic, Stripe, etc.), write BOTH paths: (a) real call when the env key is present, (b) deterministic local fallback when absent, marked with // TODO(oma-deferred): integrate <vendor> when key is provisioned. Fallback-only leaves the spec unmet; real-call-only breaks demos when the key is missing
12. Stateless services: no in-memory session or user state between requests; use external stores (DB, Redis, cache) for shared state
13. Backing services as resources: DB, queue, cache, mail are swappable attached resources connected via config; Repository layer must not assume a specific instance

Stack Detection

1. Project files first: Read existing code, package manifests (pyproject.toml, package.json, Cargo.toml, go.mod, pom.xml, etc.) to determine the tech stack
2. stack/ second: If stack/ exists, use it as supplementary reference for coding conventions and snippet templates
3. Neither exists: Ask the user or suggest running /stack-set

Stack-Specific Reference

• Stack manifest (SSOT): stack/stack.yaml: structured declaration (language, framework, orm) and verify: contract consumed by oma verify backend. Schema: variants/stack.schema.json.
• Tech stack narrative: stack/tech-stack.md: human-readable reference only; stack.yaml wins on conflict.
• Code snippets (copy-paste ready): stack/snippets.md
• API template: stack/api-template.*

References

Follow resources/execution-protocol.md step by step. Use resources/orm-reference.md when the task involves ORM query performance, relationship loading, transactions, session/client lifecycle, or N+1 analysis. Before submitting, run resources/checklist.md. Vendor-specific execution protocols are injected automatically by oma agent:spawn. Source files live under ../_shared/runtime/execution-protocols/{vendor}.md.

• Execution steps: resources/execution-protocol.md
• Checklist: resources/checklist.md
• ORM reference: resources/orm-reference.md
• Error recovery: resources/error-playbook.md
• Context loading: ../_shared/core/context-loading.md
• Clarification: ../_shared/core/clarification-protocol.md
• Context budget: ../_shared/core/context-budget.md
• Lessons learned: ../_shared/core/lessons-learned.md
• Observability handoff: ../oma-observability/SKILL.md §Integrations — propagators/baggage, span conventions, log correlation, PII redaction