# FAHCE Claim Verification and Repair

> FAHCE Claim Verification and Repair is a paid API for AI agents from fahce.kinganlogic.com, paid per call via x402, $0.15/call, status unknown (last checked 2026-10-15).

Reviews a candidate output's claims against supplied evidence, diagnoses contradictions, and returns a bounded step-by-step repair plan with a proposed corrected output.

## Facts

- Endpoint: POST https://fahce.kinganlogic.com/api/v1/repair?utm_source=zero.xyz
- Price: $0.15/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-15
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/fahce-claim-verification-and-repair-077a21e5
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_vHhpoPlQXWddhg10cuB_i

Status and success rate cover calls made through Zero and Zero's own probes. Third-party monitors may report differently.

## How to call it through Zero

Zero handles the 402 payment challenge and records the run. With the Zero CLI installed (`npm i -g @zeroxyz/cli`):

```sh
zero fetch --capability fahce-claim-verification-and-repair-077a21e5 -d '<json body>'
```

Example prompt: Check this draft answer against my evidence documents and give me a bounded repair plan — here's the schema I'm using, the evidence array, and the candidate output I want diagnosed for contradictions.

## When to prefer this

Choose FAHCE when you need to programmatically verify that a generated or candidate text is consistent with a specific set of evidence documents, and you want not just a diagnosis but an actionable, bounded repair plan with a proposed corrected output. It is especially well-suited for agent pipelines that need grounded, evidence-anchored outputs before delivering results to users, or when auditing LLM responses for hallucinations against retrieved context.

## Known failure modes

- Missing required fields (schema, evidence, or candidate_output) returns a 4xx validation error
- Evidence array is empty or malformed, leading to an inconclusive diagnosis
- Candidate output is too long or exceeds token limits
- Payment not received or invalid x402 payment header results in 402 Payment Required
- Idempotency key collision may return a cached prior result
- Billing determination not produced (DETERMINATION_NOT_PRODUCED) if service cannot assess the request

## How this service works

Review claims against evidence, resolve contradictions, and get a bounded repair plan with FAHCE.

## Output

Returns a structured FAHCE_MACHINE_RESPONSE_V1 object containing: a diagnosis of contradictions and unsupported claims, a repair plan with bounded step-by-step corrections (each step scoped with a boundary), a proposed corrected output string, verification results, billing determination (billable flag, free-retry eligibility, reason), a receipt, and a recommended next safe action. The repair is proposed but not automatically executed (status: PROPOSED_NOT_EXECUTED).

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "required": [
  "schema",
  "evidence",
  "candidate_output"
 ],
 "properties": {
  "schema": {
   "type": "string"
  },
  "evidence": {
   "type": "array"
  },
  "expected_output": {
   "type": "string",
   "description": "Optional response-contract and repair-target context for all operations, including Diagnose. Supported response-format directives (for example, Return JSON) and implemented explicit constraints can affect the diagnosis. Ordinary matching or mismatching factual text is not compared for string equality and is not a trusted answer oracle or supporting evidence; supply independent evidence for factual claims."
  },
  "candidate_output": {
   "type": "string",
   "description": "The exact candidate output to diagnose or verify. Never use payment evidence as semantic evidence."
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "object",
 "required": [
  "schema",
  "operation",
  "request_id",
  "input_hash",
  "diagnosis",
  "repair",
  "verification",
  "billing",
  "receipt",
  "next_safe_action"
 ],
 "properties": {
  "repair": {
   "anyOf": [
    {
     "type": "object",
     "required": [
      "plan",
      "treatment",
      "proposed_output",
      "status"
     ],
     "properties": {
      "plan": {
       "type": "object",
       "required": [
        "required",
        "bounded_steps",
        "authority_note"
       ],
       "properties": {
        "required": {
         "type": "boolean"
        },
        "validated_ir": {
         "type": "object"
        },
        "bounded_steps": {
         "type": "array",
         "items": {
          "type": "object",
          "required": [
           "step",
           "boundary"
          ],
          "properties": {
           "step": {
            "type": "string"
           },
           "boundary": {
            "type": "string"
           }
          },
          "additionalProperties": false
         }
        },
        "authority_note": {
         "type": "string"
        },
        "claim_corrections": {
         "type": "array",
         "items": {
          "type": "object"
         }
        }
       }
      },
      "status": {
       "const": "PROPOSED_NOT_EXECUTED"
      },
      "treatment": {
       "type": [
        "object",
        "null"
       ]
      },
      "proposed_output": {
       "type": [
        "string",
        "null"
       ]
      }
     },
     "additionalProperties": false
    },
    {
     "type": "null"
    }
   ]
  },
  "schema": {
   "const": "FAHCE_MACHINE_RESPONSE_V1"
  },
  "billing": {
   "type": "object",
   "required": [
    "billable",
    "free_retry",
    "reason",
    "determination_status"
   ],
   "properties": {
    "reason": {
     "type": [
      "string",
      "null"
     ]
    },
    "billable": {
     "type": "boolean"
    },
    "free_retry": {
     "type": "boolean"
    },
    "determination_status": {
     "enum": [
      "DETERMINATION_COMPLETE",
      "DETERMINATION_COMPLETE_NEGATIVE",
      "DETERMINATION_NOT_PRODUCED"
     ]
    }
   }
  },
  "binding": {
   "type": "object",
   "required": [
    "actor_id",
    "tenant_id",
    "nonce",
    "idempotency_key"
   ],
   "properties": {
    "nonce": {
     "type": "string"
    },
    "actor_id": {
     "type": "string"
    },
    "tenant_id": {
     "type": "string"
    },
    "tenant_model": 
… (truncated)
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/fahce-claim-verification-and-repair-077a21e5/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from fahce.kinganlogic.com](https://www.zero.xyz/host/fahce.kinganlogic.com/llms.txt)