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Surface: GET /agents/runs/{id}, error.type = "AgentLoopStructuredOutputRetriesExhausted"

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When this error occurs

When the model emits a final structured answer, the platform validates it against the run’s output_format_schema. A validation failure no longer fails the run outright — instead the workflow feeds the failure back to the model (the non-conforming output plus the validator’s explanation) and asks it to try again. This error means every one of those retries also failed validation, so the workflow gave up.
  • The retry budget is a fixed 10 attempts — separate from max_iterations, which bounds productive tool-use rounds rather than these corrective re-prompts.
  • Each retry is one inference job, so a run that hits this error has spent 11 inference jobs on the final answer alone (the first attempt plus 10 retries).
  • Distinct from Output Schema Decode Failed: that one is a single, non-retried decode failure of the final answer; this one is the terminal state after the retry loop is exhausted.

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How to fix

  • Simplify the schema — Bedrock’s structured-output sampler enforces a subset of Draft 2020-12; deeply nested or exotic constructs (e.g. unconstrained oneOf) are the most common reason the model can’t produce a conforming object even when re-prompted.
  • Reinforce the schema in the system prompt — tell the model explicitly what shape to emit and which fields are required. A schema the sampler struggles with is often one the model was never steered toward in the instructions.
  • Inspect the last failed_structured_output on the final inference job’s result — it holds the raw JSON the model produced and the validator’s message, which pinpoints the field that keeps failing.