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The certificate is the factory’s unit of trust — the answer to the governing question any operator must face: when this breaks in production, who takes the call? The factory does, and the certificate is the artifact that makes that answerable. A Certificate of Conformance — the lot number — is a signed, versioned record issued at Station 4:
FieldContent
UnitName, family (skill/tool/agent), version
Bill of materialsContent hashes of every context file, skill version, tool version, model and version per binding
EvidenceEval scores, proof-of-work artifacts, judge transcripts, trace links
ProvenanceWork order link, principal, assembling agent, trial-run records
LiabilityOwner of record, escalation path, recall procedure
ExpiryRe-certification interval plus trigger conditions: model swap, dependency change, N production failures

Not a badge — a claim with an expiry

A certificate attests that a specific unit, with a specific bill of materials, passed specific verification against a specific work order, on a specific date. Every word of that sentence is load-bearing, and the last one is why certificates expire: the unit’s quality is a distribution over future runs, and the world under it drifts (Thesis 2). A unit without a certificate is not finished; the certified unit — artifact plus certificate — is the factory’s unit of production. The builder does not certify. Verification is independent of generation (Station 3), and the signature at Station 4 is human acceptance of the claim and its evidence — one of the line’s two takt-bound touches.

What a certificate buys

Full traceability comes free: any field defect walks backward from certificate to BOM to part to die, so the fix lands on the die — the template, the part process — not on the single unit. Fleet response becomes a query: a model swap reopens every certificate that binds that model; the BOM makes this a lookup, not an investigation. Early invalidation is defined, not improvised: the expiry field names its own triggers. Certificates live in git alongside the units they attest. The certificates are proof you can sleep.

The shelf: certificates issued

Every certificate below is a live record, not a sample. Each page renders the real card, the content-hashed bill of materials, the evidence with its actual numbers, the liability chain, and the expiry with its triggers. Two of the four carry a published defect: that is the point, not an embarrassment. A factory that hides its escapes is selling permanent trust, which nobody honest sells.
CertificateUnitFamilyThe story
#001op-headless 1.1skillRe-certified under the new gates. Opened red; a four-month-old defect, found and fixed.
#002validate-work-order 1.0toolThe factory’s own intake gate, certified. Clean first pass.
#003silence-watchdog 1.0toolThe second andon wire, certified. Clean first pass.
#004todo-issue-sync 1.0skillThe first demand-pulled unit. Three escapes found in review after certification, all fixed before merge.

Self-audit

ClaimSource
”Who takes the call?” — the certificate makes it answerabledocs/factory-design.md:131
Certificate field table (unit, BOM, evidence, provenance, liability, expiry)docs/factory-design.md:135–142
Traceability: certificate → BOM → part → diedocs/factory-design.md:144
Human acceptance at exit; reviews the claim and evidence, not the workdocs/factory-design.md:146
Model swap reopens affected certificates as a querydocs/factory-design.md:158
Certified unit is the unit of production; certificate committed in gitworkflows/production-line.md:56, 64
The four issued certificates and their published defectscertificates/op-headless-1.1.md, validate-work-order-1.0.md, silence-watchdog-1.0.md, todo-issue-sync-1.0.md; retros quality/retros/002 and 004