CAIN-42 PBFT quorum-certificate evidence: four-server-cluster-2026-09-27
============================================================================

What: Every quorum certificate held by each replica of cain-mr-02 after each of its 4 hosts was taken down in turn (the cluster had to keep committing) and two hosts were taken down at once (it had to refuse). Identical decision chains on all replicas show there was no fork.
Classification: MEASURED on the live cluster cain-mr-02 (4 replicas on 4 hosts)
Generated: 2026-09-27T00:08:12Z
Source commitment: git 521f84c0456bf118645722073f09df140167b16b (engine 33.4-production-hardened); source is not published.

Verify in about 30 seconds (Python 3.8+, `pip install cryptography`, no CAIN code):

  BASE=https://cainstudio.online/proof/bundle/four-server-cluster-2026-09-27/      # or https://mcpgate.online/proof/bundle/four-server-cluster-2026-09-27/
                                                             # or https://clawx.click/evidence/four-server-cluster-2026-09-27/
  curl -so verify_pbft_qc_bundle.py "$BASE/verify_pbft_qc_bundle.py.txt"
  curl -so PBFT_QC_BUNDLE.json "$BASE/PBFT_QC_BUNDLE.json"
  sha256sum PBFT_QC_BUNDLE.json verify_pbft_qc_bundle.py
    # expect 0ed32a92d4c58c3517679c6c0ca7c318a45960c01b5b63e7ce87db677b6a3b71  PBFT_QC_BUNDLE.json
    # expect ba452ce42528f11f7f5235727a65cae25a34072bc52b4711fd72581615d06009  verify_pbft_qc_bundle.py
  python3 verify_pbft_qc_bundle.py PBFT_QC_BUNDLE.json

Or open $BASE/index.html: your browser runs the same checks (WebCrypto Ed25519).

Read the verifier before trusting it: it is about 300 lines. It tampers with a certificate
in seven ways and requires every tampered copy to fail, so a verifier that accepts
everything would not pass.

Not claimed: independent providers (all hosts are Vultr); placement is operator-attested; third-party review; absence of bugs.