How it works

Three steps, and the second is the product.

1. Ask

A natural-language question resolves to a certified metric and a scope (period grain, entity, consolidated or not). The query is built from the trusted semantic layer and run as parameterized, read-only SQL — never string-built, never free-form. The agent answers; it does not certify.

question → resolve to a certified metric + scope → parameterized SQL → execute (read-only) → answer

A question outside the certified definitions returns WARN — an honest "I don't have a certified definition for that," never a fabricated number.

2. Verify — independently

This is the core. Given the answer, Tessera recomputes it by an orthogonal path: it rolls the certified metric up directly from the warehouse — a different engine than the agent's SQL, and never derived from that SQL. Re-running the model's own query to "check" it would be circular and worthless; Tessera never does that.

If the claim and the orthogonal truth diverge, the verifier diagnoses which failure class produced the wrong number by matching it against the counterfactual value of each failure class, and reports both figures.

truth = rollup(certified metric)        # orthogonal — not the agent's SQL
if |claim − truth| > tolerance:
    name the failure class whose counterfactual == claim   → FAIL
elif required SQL clause missing:
    fragile query, right answer          → WARN
else:                                    → PASS

Light SQL-contract heuristics corroborate the diagnosis but never decide the verdict on their own.

3. Attest

The verdict, the executed SQL, and the answer are bound into an Ed25519-signed receipt. Anyone re-checks it offline — they trust the receipt, not the assistant.

The shared contract

Internally, every verdict is an agentsensory Report = verdict + grounded issues + signed handoff. Tessera consumes that contract; it does not redefine it. Issues are grounded in Tessera's dimension — the failure class.

Architecture

                ┌──────────────┐     ┌────────────────────┐     ┌──────────────────┐
  question ───▶ │  agent       │ ──▶ │  independent       │ ──▶ │  receipt         │
                │  (resolve +  │ SQL │  verifier          │     │  (Ed25519 sign)  │
                │   exec SQL)  │     │  (orthogonal       │     │                  │
                └──────────────┘     │   recompute +      │     └──────────────────┘
                       │             │   8 failure checks)│              │
                       ▼             └────────────────────┘              ▼
              governed GL warehouse          ▲                   tessera verify
              (sqlite / Postgres)            │                   (offline)
                       └──────── certified metric semantic layer ┘

The same pipeline is exposed over a CLI, a REST API, and an MCP server, and runs cloud or fully air-gapped.