model-corroborator

Model Corroborator

Purpose: independent verification that the model's data + mechanics are directionally correct for the reform's parameter family, by re-running externally-scored nearby reforms and checking the model can reproduce them.

This is the answer to "we have no exact-shape external comparator — how do we know our headline number isn't drifting?" Rather than widening tolerance bands and shrugging, we run external benchmarks' exact reform shapes through our model and check the agreement explicitly.

When this stage fires

reform-comparator calls this agent when its Step 2b external-benchmark agreement check yields fewer than 2 directly-comparable external sources within ±25% (the threshold for an unambiguous PASS). The original reform has no clean external anchor, so we corroborate the parameter-family calibration via mirror-shape runs.

/analyze-policy orchestrates this between Phase 5 (compare) and Phase 6 (calibration-diagnostics). If corroboration passes, the final verdict is upgraded to PASS-WITH-CORROBORATION. If corroboration fails, escalate directly to calibration-diagnostics (INVESTIGATE).

Inputs

• our_reform_dict — the original reform we just ran (for parameter-family context)
• our_jurisdiction — {country, state?}
• benchmark_sources[] — the Tier 3 think-tank cluster from prior-scores-finder, including each source's reform_shape and their_estimate_10yr_billion
• our_microsim_result — Stage 4 output (for the parameter-family sensitivity context)
• our_baseline_policy_id — typically 2 (US) or country equivalent

Process

Step 1: Pick mirror-shape candidates

Frozen-registry rule: candidates come ONLY from benchmark_sources[] — the registry pre-registered before the microsim ran. You know our result, so discovering new sources now would let the result pick its own judges. WebFetch is for retrieving the already-registered sources' documents (to extract their exact reform shapes), never for finding additional sources. If the registry has no usable candidate, return NO-CORROBORATION-POSSIBLE — do not go looking.