Source: https://guthlabs.ai/docs/instruments/bitmask-flag-builder/implementation/

instrument implementation / implementation-contract

# Bitmask / Flag Builder implementation

A source-bound implementation contract for Bitmask / Flag Builder; 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**: t2-040

**Effect**: Computation or source lookup only

## Input and validation requirements

The extreme-magnitude vector exposes a real JavaScript Number precision failure: the exact mask 9007199254740993 is rounded to 9007199254740992, causing the bit-0 flag to disappear during decomposition. The convention probe also exposes an underspecified 0-based versus 1-based flag-index interpretation.

## 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": {
    "mode": "compose",
    "flags": {
      "read": {
        "bit": 0,
        "toggled": true
      },
      "write": {
        "bit": 1,
        "toggled": false
      },
      "execute": {
        "bit": 2,
        "toggled": true
      }
    },
    "tests": [
      "read",
      "write",
      "execute"
    ]
  },
  "expected_outputs": {
    "result": 5,
    "tests": {
      "read": 1,
      "write": 0,
      "execute": 4
    },
    "active_flags": [
      "read",
      "execute"
    ]
  },
  "working": "read = 2^0 = 1. write = 2^1 = 2, but it is off, so contribute 0. execute = 2^2 = 4. mask = 1 + 0 + 4 = 5. Tests: 5 & 1 = 1, 5 & 2 = 0, and 5 & 4 = 4. Therefore the active flags are read and execute."
}
````

## Other records

[01**Overview**](<https://guthlabs.ai/docs/instruments/bitmask-flag-builder/>)[02**Mechanism**](<https://guthlabs.ai/docs/instruments/bitmask-flag-builder/mechanism/>)[04**Qualification**](<https://guthlabs.ai/docs/instruments/bitmask-flag-builder/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-tranche2/tranche2-results.json`