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AIMODELRACE
Build software

Best agent for backend & apis

Designing endpoints, data models, business logic, auth and integrations.

Leader

Narrow lead

Claude Opus 5.5

Index

95

Lead

+1.0

% ahead

1.1%

over Claude Fable 5.1.

Full ranking

Task index, 0 to 100. Bars are scaled to the field, so small gaps look small.

  1. 1
    Claude Opus 5.5
    95

    Most reliable with complex domain logic.

  2. 2
    Claude Fable 5.1
    −1.094

    Even deeper reasoning, at higher cost.

  3. 3
    GPT-6 Astra
    −3.092

    Excellent, a touch less consistent on long sessions.

  4. 4
    Claude Sonnet 5.5
    −4.091

    Best value for routine endpoint work.

  5. 5
    DeepSeek V4 Pro
    −10.085

    Strong open option for cost-sensitive teams.

Key takeaways
  • 1Opus 5.5 leads on getting business logic and edge cases right.
  • 2Tests are the agent's best friend: TDD loops work extremely well.
  • 3Watch for subtle security and transaction mistakes.

Recommended setup

A coding agent with database access in a dev environment, the OpenAPI spec in context, and a test suite it must keep green.

Prompts that work

Endpoint with tests first

Implement {{endpoint}} per this spec: {{spec}}. Write integration tests first covering success, validation errors, auth failures and concurrency edge cases. Run them, implement, and show passing output. Flag any spec ambiguity instead of guessing.

More in build software

Frontend & UI

Claude Opus 5.5 (Claude Code)+2.0

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Claude Fable 5.1+4.0

Website building

Claude Code + Opus 5.5+2.0

App building

Claude Code + Opus 5.5+3.0

DevOps & infrastructure

Claude Sonnet 5.5+0.6

Data & analytics

GPT-6 Astra+0.7

Code review & security

Claude Opus 5.5+3.0