Source: https://guthlabs.ai/docs/instruments/http-status-code-header-lookup/implementation/

instrument implementation / implementation-contract

# HTTP Status Code / Header Lookup implementation

A source-bound implementation contract for HTTP Status Code / Header Lookup; deployment and executable qualification remain separate.

Status: **VERIFIED_CLEAN**Lifecycle: **implementation-contract**

## Binding contract

This record describes what an executable surface must bind and validate. It does not claim that a public calculator, package, or production route is deployed.

**Record owner**: Guth Instruments

**Lifecycle**: verified-clean

**Evidence ID**: t7-038

**Effect**: Computation or source lookup only

## Input and validation requirements

- Unknown, obsolete, deprecated, extension, and unofficial status codes must not be silently presented as standard IANA codes.

- Status codes outside 100-599, non-integer inputs, and integers with more or fewer than three decimal digits require explicit validation behavior; code 0 must not be treated as a valid HTTP status code.

- A lookup miss for a header must be distinguished from a recognized but deprecated or non-standard header.

- Header names must be matched case-insensitively, while header values and parameter names may have separate parsing rules.

- 'Common causes' can be misleading because the same status code or header can result from many application, proxy, cache, or server conditions.

- The empty honest_label is a concern: the panel should disclose that common causes and related-code lists are curated annotations, not always normative IANA or RFC fields.

- The data tables need an update/version policy because the IANA registry and HTTP field registry can change.

## Required corrections

No binding erratum is attached to this unique-name record. Implementers must still preserve the declared units, domain, and failure behavior.

## Inspectable interface fixture

The sample below is evidence for interface and validation tests, not a production implementation.

````
{
  "inputs": {
    "status_code": 200
  },
  "expected_outputs": {
    "description": "OK",
    "category": "2xx",
    "common_causes": [
      "The request succeeded."
    ],
    "related_codes": [
      201,
      202,
      204
    ]
  },
  "reference_data": {
    "status_code_entry": {
      "code": 200,
      "description": "OK",
      "source_convention": "IANA HTTP Status Code Registry / RFC 9110 §15.3.1"
    },
    "category_rule": {
      "range": "200-299",
      "category": "2xx",
      "source_convention": "RFC 9110 status-code class convention"
    },
    "operational_annotation": {
      "common_causes": [
        "The request succeeded."
      ],
      "related_codes": [
        201,
        202,
        204
      ],
      "source_convention": "Widely tabulated standard operational interpretation; not an IANA normative field"
    }
  },
  "working": "1. Read status code 200 from the bundled registry. 2. Look up 200 => 'OK'. 3. Compute the class: floor(200 / 100) = 2, so the category is 2xx. 4. Return the bundled operational annotation: successful request; related success codes 201, 202, and 204."
}
````

## Other records

[01**Overview**](<https://guthlabs.ai/docs/instruments/http-status-code-header-lookup/>)[02**Mechanism**](<https://guthlabs.ai/docs/instruments/http-status-code-header-lookup/mechanism/>)[04**Qualification**](<https://guthlabs.ai/docs/instruments/http-status-code-header-lookup/qualification/>)

## Sources and evidence

These pointers bind the page to evidence. They do not grant authority or collapse verification into deployment.

- `VERIFIED_LEDGER.json`

- `evidence-tranche7/tranche7-results.json`