How one inference becomes carbon measured

A versioned operational-energy estimate

METHODOLOGY_VERSION is 2026.1. The endpoint emits a versioned, operational-energy, market-based Scope 2 estimate for a request an external AI provider ran. It is a reproducible disclosure number, not a live meter reading from the provider's GPU or data centre.

The endpoint surface is the API Docs; the proof surface is /verify; and the verified removals being calculated against are shown in the CDR portfolio.

Declared energy boundary and grid factors

The declared boundary is 0.3 kWh × PUE 1.6 ≈ 0.48 kWh: an inference-workload energy estimate with power usage effectiveness applied. The global market-based grid baseline in public/data/grid-intensity.json is 0.432 kg CO₂/kWh, or 432 g CO₂/kWh, sourced from Ember Global Electricity Review 2025.

declared workload energy   0.3 kWh × PUE 1.6 ≈ 0.48 kWh
global grid baseline       0.432 kg CO₂/kWh = 432 g CO₂/kWh
authoritative live baseline CO2_PER_QUERY_KG = 0.0007 kg

Region lookup is exact and lower-case. A recognized row supplies the grid intensity used to scale the total; the selected row's source label is returned separately as grid_intensity_source. The current human-readable methodology.basis string ends with the literal (Ember 2025), while the source table below preserves each row's own source and date.

From request inputs to the emitted number

The route recognizes gpt-4-class. Any other non-empty model string falls through to the same current default baseline, 0.0007 kg; missing model, region, or tokens is a 400. Region matching uses the exact lower-case keys above. An unknown region uses the global baseline for both the coefficient and the displayed intensity.

base = MODEL_KG_PER_QUERY[model] || CO2_PER_QUERY_KG
if grid[region] exists:
  perQueryKg = base × (grid[region].kgPerKWh / 0.432)
else:
  perQueryKg = base
kg_co2e_estimated = tokens × perQueryKg
kg_co2_removed    = kg_co2e_estimated

tokens must parse as a finite, non-negative number. The implementation floors it and then caps it at 1e12: tokens = Math.min(Math.floor(parsedTokens), 1e12).

Worked example: region=eu_avg

For model=gpt-4-class, region=eu_avg, and tokens=10000, the selected row is 0.231 kg/kWh and the global denominator is 0.432 kg/kWh.

perQueryKg = 0.0007 × (0.231 / 0.432)
            = 0.00037430555555555557 kg/query
kg_co2e_estimated = 10000 × perQueryKg
                  = 3.743055555555556 kg
kg_co2_removed    = 3.743055555555556 kg

The response also returns grid_intensity_g_per_kwh: 231 and grid_intensity_source: "EEA 2023 final". Its current basis string uses grid 0.231 kg/kWh (Ember 2025) because that suffix is literal in the route.

The removed amount follows the measured amount

The current attestation contract assigns kg_co2_removed = kg_co2e_estimated. It names TAO-UKR-HEMP-MRV-2026 in removal_project_id, connecting the request to the verified CDR project and inventory surface at /portfolio.

This page documents the fields emitted by the attestation route. The portfolio page remains the source for the verified project list and live GET /api/co2-removals?status=verified inventory; no new removal query runs here.

A deterministic hash with a public round-trip

Before the response is persisted, the route builds a disclosureCore containing the request values, calculated amounts, issue timestamp, and methodology version. canonicalize recursively sorts object keys and emits JSON without whitespace. The receipt hash is then h_ plus the SHA-256 digest of that canonical string.

disclosureCore = {
  model,
  region,
  tokens,
  kg_co2e_estimated,
  kg_co2_removed,
  issued_at,
  methodology_version
}
receipt.hash = "h_" + SHA256(canonicalize(disclosureCore))

The response's receipt carries hash, the chain marker hashbon:taoclimate:v1, and an absolute receipt.verifyUrl. When the database is available, the payload is stored in ai_receipt_certificates with source inference-attest and a server created_at timestamp; the response may also include receipt.attached_at.

Opening the verify URL in a browser renders the existing /verify proof surface. Its client requests /verify/:hash with Accept: application/json, receives the stored payload and certificate envelope, and renders the same fields for inspection. The endpoint surface and response shape remain documented in /docs.

The proof still points back to the named CDR project and verified inventory at /portfolio, so the measurement, attribution, and verification surfaces can be reviewed together.