Source: https://guthlabs.ai/docs/instruments/packing-weight-checker/implementation/

instrument implementation / implementation-contract

# Packing Weight Checker implementation

A source-bound implementation contract for Packing Weight Checker; 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**: t4-187

**Effect**: Computation or source lookup only

## Input and validation requirements

The extreme-magnitude vector produces Infinity in JavaScript, and the negative-weight vector exposes an input-validation and sign-convention hazard. The checker should reject non-finite values, negative physical item weights, and mixed or unlabeled units before calculating totals.

## 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": {
    "bags": [
      {
        "id": "bag_1",
        "items": [
          {
            "name": "clothes",
            "weight": 2.4
          },
          {
            "name": "shoes",
            "weight": 1.8
          },
          {
            "name": "toiletries",
            "weight": 3.1
          }
        ],
        "limit": 8
      }
    ],
    "unit": "kg"
  },
  "expected_outputs": {
    "total_weight": 7.3,
    "pass_fail_per_bag": {
      "bag_1": "PASS"
    },
    "overage": -0.7
  },
  "working": "total_weight = 2.4 + 1.8 + 3.1 = 4.2 + 3.1 = 7.3 kg. overage = 7.3 − 8.0 = −0.7 kg. Since 7.3 <= 8.0, bag_1 = PASS."
}
````

## Other records

[01**Overview**](<https://guthlabs.ai/docs/instruments/packing-weight-checker/>)[02**Mechanism**](<https://guthlabs.ai/docs/instruments/packing-weight-checker/mechanism/>)[04**Qualification**](<https://guthlabs.ai/docs/instruments/packing-weight-checker/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-tranche4/tranche4-results.json`