Evaluating with Leakage Gates

OpenMed's release gates answer one question: did any PHI leak? A de-id model with a beautiful F1 can still leak a single SSN — and that one leak is a HIPAA breach. So openmed.eval gates on residual leakage and per-label recall floors, not on aggregate F1. The candidate is either RELEASABLE or QUARANTINED; there is no partial credit.

When to use this skill

• You have a candidate de-id or PII model and need a ship / no-ship decision.
• You want to run the benchmark harness over a synthetic golden suite.
• You need to enforce direct-identifier recall floors and critical_leakage == 0.
• You need calibration thresholds (thresholds.json) before the gate will pass.
• You want a signed, reproducible gate report for governance.

This is the flagship eval skill. For a pure NER scorecard see benchmarking-clinical-ner; for CI wiring see gating-deid-leakage.

The gates (G1a–G8)

Constants live in openmed.eval.release_gates (G1A_V16_RECALL_FLOOR, G1B_RECALL_FLOOR, G7_RECALL_DROP_LIMIT, RESIDUAL_LEAKAGE_SOFT_CEILING, ...). Confirm them there rather than hardcoding — they move per milestone.

Quick start

Run a candidate benchmark over a synthetic golden suite, then gate it:

from openmed.eval import run_suite, ReleaseGate, RELEASABLE

# 1) Produce a candidate BenchmarkReport from a SYNTHETIC fixtures file.
#    Each fixture carries gold PHI spans; no real patient text is committed.
report = run_suite(
    "eval/golden/phi_synthetic.json",     # user-supplied synthetic fixtures
    suite="golden",
    model_name="OpenMed/Privacy-PII-Detection",
    device="cpu",
    metadata={
        "family": "PII",
        "tier": "base",
        "policy": "hipaa_safe_harbor",
        # calibration artifacts are required for mask/replace policies (see below)
        "thresholds_path": "eval/artifacts/thresholds.json",
        "calibration_report_path": "eval/artifacts/calibration_report.json",
    },
)

# 2) Gate it. The gate reads the last-green baseline store read-only and
#    returns a signed GateReport.
gate = ReleaseGate(milestone="v1.6", policy="hipaa_safe_harbor")
decision = gate.evaluate(report)

print(decision.decision)                  # "RELEASABLE" or "QUARANTINED"
for check in decision.gate_results:
    if not check.passed:
        print(check.gate, "->", check.reason, check.details)

assert decision.decision == RELEASABLE, "do not ship a quarantined model"

CLI equivalent (fails closed, exit code 1 on quarantine):

python -m openmed.eval.release_gates \
  --candidate eval/out/candidate_report.json \
  --milestone v1.6 --policy hipaa_safe_harbor \
  --output release-gate-report.json

Workflow

1. Build a synthetic golden suite. Fixtures are JSON with text and gold_spans (offsets + labels). Use building-gold-corpus to scaffold one. Committed gold must be synthetic; DUA corpora (i2b2/n2c2) are eval-only and never committed.

2. Fit calibration thresholds for any policy that masks or replaces:

   from openmed.eval import write_calibration_artifacts
   
   paths = write_calibration_artifacts(
       calibration_samples,                 # held-out score/target samples
       artifact_dir="eval/artifacts",
       model_id="OpenMed/Privacy-PII-Detection",
       suite="golden",
       target_leakage=0.0,                   # leakage-first: drive leakage to 0
   )
   # writes thresholds.json + calibration_report.json the gate looks for
   

   The gate's calibration_present check fails the build if these are missing for a mask/replace policy.

3. Run the suite (run_suite / run_benchmark) to get a BenchmarkReport.

4. Evaluate with ReleaseGate(...).evaluate(report).

5. Read the per-gate results. Each GateCheck carries gate, passed, reason, and details (e.g. which labels fell below the recall floor).

6. Fail closed. Treat anything other than RELEASABLE as a hard stop.

7. Audit subgroups with fairness_report (see auditing-subgroup-fairness) so an aggregate pass doesn't hide an under-protected group.

Hand-off to / from OpenMed

• From building-with-openmed and the de-id pipeline: you evaluate the model produced by openmed.deidentify / openmed.extract_pii.
• To gating-deid-leakage: wrap ReleaseGate.evaluate(...) in a pytest/CLI gate so CI fails closed on regression.
• To authoring-model-cards: feed GateReport, fairness_report, and error_report outputs into the model card's metrics and limitations sections.
• Pairs with auditing-subgroup-fairness (fairness_report) and benchmarking-clinical-ner (error_report).

Edge cases & gotchas

• F1 is not a gate. A model can have higher F1 and still be quarantined if it leaks one critical identifier (G3) or drops a label below its floor (G1a/G1b).
• Calibration is mandatory for mask/replace policies. No thresholds.json → calibration_present fails → QUARANTINED.
• Baselines are read, never written, by the gate. The gate compares against the last-green baseline store without mutating it (G7). Promote baselines in a separate, deliberate step.
• Strict-no-leak policies raise the G1a floor and force the leakage target to 0. Don't assume the default floor.
• Reports must carry identity metadata (family, tier, format, eval_set_hash, leakage_fixture_hash); manifest_coherence fails without it.
• Reports are signed (HMAC-SHA256). Set OPENMED_RELEASE_GATE_KEY for a real signing key; GateReport.verify(key) checks the repro hash and signature.
• No raw PHI in the report. Gate evidence is offsets, hashes, and labels — never plaintext identifiers. Keep it that way in any wrapper you write.

Standards & references

• HIPAA Safe Harbor / Expert Determination (45 CFR 164.514): https://www.hhs.gov/hipaa/for-professionals/privacy/special-topics/de-identification/
• NIST SP 800-188, De-Identification of Personal Information: https://csrc.nist.gov/pubs/sp/800/188/final
• i2b2 2014 de-identification shared task (recall-first evaluation tradition): https://doi.org/10.1016/j.jbi.2015.06.007
• OpenMed eval source of truth: openmed/eval/release_gates.py, openmed/eval/harness.py, openmed/eval/calibrate.py.