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GEPA (Genetic Evolution of Prompt Architectures) is an evolutionary algorithm for optimizing prompts through population-based search. Endpoint: POST /api/policy-optimization/online/jobs Authentication: Bearer token via Authorization: Bearer $SYNTH_API_KEY

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Request

{
  "policy_optimization": {
    "algorithm": "gepa",
    "task_app_url": "https://your-task-app.example.com",
    "policy": {
      "model": "gpt-4o-mini",
      "provider": "openai",
      "temperature": 0.0,
      "max_completion_tokens": 256
    },
    "gepa": {
      "population": {
        "num_generations": 5,
        "children_per_generation": 4
      },
      "rollout": {
        "budget": 200
      }
    }
  }
}

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GEPA-Specific Parameters

ParameterTypeDescription
gepa.population.num_generationsintNumber of evolutionary generations
gepa.population.children_per_generationintCandidates generated per generation
gepa.rollout.budgetintTotal rollout budget for optimization

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Response

{
  "job_id": "pl_abc123",
  "status": "running"
}

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Polling for Completion

Use GET /api/policy-optimization/online/jobs/{job_id} to check status: 
{
  "job_id": "pl_abc123",
  "status": "succeeded",
  "best_score": 0.875
}

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Notes

  • GEPA requires the backend to call your task app, so:
    • Task app must be publicly accessible (via tunnel for local development)
    • ENVIRONMENT_API_KEY must be registered with the backend
  • See the GEPA walkthrough for a complete example