Problem type `harness-error`

This URI identifies a Problem Details (RFC 9457) object that describes an error detected by an AI agent harness:

https://agenterrors.org/problems/harness-error

Implementations may use this URI until the problem type is registered with IANA as https://iana.org/assignments/http-problem-types#agent-harness-error. Consumers must treat the two URIs as equivalent.

This page summarizes the editor's copy of the draft. If they differ, the draft is authoritative.

Required member

code is a registered error code of the form <category>.<name>, for example output.schema_violation. Consumers decide what kind of error occurred from code, never from title or detail.

Extension members

Member	Meaning
`origin`	Where the error originated: `model`, `harness`, `tool`, `upstream`, or `user`.
`retryable`	Whether repeating the same operation unchanged may succeed.
`model_recoverable`	Whether the model is likely to correct the error if it is told about it.
`model_feedback`	Text intended for the model, distinct from `detail`, which is for humans.
`retry_after`	Seconds after which a retry is advised.
`attempts`, `max_attempts`	Attempts already made, and the configured maximum.
`limit`	The exceeded limit: `name`, `value`, `observed`, `unit`.
`location`	Where in the run: `run_id`, `turn`, `tool_name`, `tool_call_id`, `pointer`.
`upstream`	Raw information from an upstream component, kept for diagnosis.
`causes`	Problem details objects that caused this one, most recent first.

Code categories

Category	Description
`output`	Model output could not be accepted by the harness.
`loop`	A limit on the agent loop was reached, or the loop is not progressing.
`context`	Context assembly or management failed.
`tool`	Tool resolution or execution failed.
`policy`	A policy, guardrail, refusal, or human decision stopped the operation.
`upstream`	A remote dependency, typically the model API, failed.
`harness`	The harness failed for another reason.

The full list of codes, with default values for retryable and model_recoverable, is in the draft.

Example

HTTP/1.1 422 Unprocessable Content
Content-Type: application/problem+json

{
  "type": "https://agenterrors.org/problems/harness-error",
  "title": "Output Retries Exhausted",
  "code": "output.retries_exhausted",
  "origin": "harness",
  "retryable": false,
  "attempts": 3,
  "max_attempts": 3,
  "causes": [
    {
      "type": "https://agenterrors.org/problems/harness-error",
      "title": "Output Schema Violation",
      "code": "output.schema_violation",
      "origin": "model",
      "model_feedback": "Field 'price' must be a number, got string.",
      "location": { "turn": 5, "pointer": "/items/0/price" }
    }
  ]
}

Other bindings