Source: https://guthlabs.ai/docs/instruments/stair-rise-run-designer/implementation/

instrument implementation / implementation-contract

# Stair Rise & Run Designer implementation

A source-bound implementation contract for Stair Rise & Run Designer; 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**: t4-043

**Effect**: Computation or source lookup only

## Input and validation requirements

A zero total rise produces num_steps = 0 and then actual_riser = 0/0, an undefined result; the instrument must reject this input before division. Negative tread depth also exposes an unspecified sign convention and can produce a misleading comfort result unless rejected or converted to a magnitude.

## 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": {
    "total_rise": 108,
    "desired_riser": 7.5,
    "tread_depth": 10.5,
    "units": "in"
  },
  "expected_outputs": {
    "step_count": 14,
    "actual_riser": 7.7142857143,
    "run": 10.5,
    "total_run": 136.5,
    "stringer_length": 174.05818,
    "comfort_flag": false,
    "code_range_flag": true
  },
  "working": "108 / 7.5 = 14.4; round(14.4) = 14 steps. Actual riser = 108 / 14 = 7.7142857143 in. Run per tread = 10.5 in. Total run = 10.5 × (14 - 1) = 10.5 × 13 = 136.5 in. Stringer = sqrt(108² + 136.5²) = sqrt(11664 + 18632.25) = sqrt(30296.25) = 174.058180 in. Comfort value = 2 × 7.7142857143 + 10.5 = 25.9285714286 in, so comfort_flag = false. Code range: 7.0 <= 7.7142857143 <= 7.75 and 10.5 >= 10, so code_range_flag = true."
}
````

## Other records

[01**Overview**](<https://guthlabs.ai/docs/instruments/stair-rise-run-designer/>)[02**Mechanism**](<https://guthlabs.ai/docs/instruments/stair-rise-run-designer/mechanism/>)[04**Qualification**](<https://guthlabs.ai/docs/instruments/stair-rise-run-designer/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`