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docs/features/checked/attestor/fixchain-attestation.md

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+# FixChain Attestation (Backport Proof)
+
+## Module
+Attestor
+
+## Status
+VERIFIED
+
+## Description
+FixChain provides attestation-based proof that a backport or fix has been applied, with validation and policy gate integration.
+
+## Implementation Details
+- **FixChain Attestation Service**: `src/Attestor/__Libraries/StellaOps.Attestor.FixChain/FixChainAttestationService.cs` -- creates fix chain attestations.
+- **FixChain Models**: `FixChainModels.cs` -- core models for fix chain data.
+- **FixChain Predicate**: `FixChainPredicate.cs` -- attestable predicate for fix chain proof.
+- **FixChain Statement Builder**: `FixChainStatementBuilder.cs` -- builds in-toto statements for fix chain attestations.
+- **FixChain Validator**: `FixChainValidator.cs` -- validates fix chain attestations.
+- **DI Registration**: `ServiceCollectionExtensions.cs` -- registers fix chain services.
+- **Fix Status Info**: `__Libraries/StellaOps.Attestor.ProofChain/Predicates/FixStatusInfo.cs` -- fix status tracking in proof chain.
+- **Tests**:
+  - `__Libraries/__Tests/StellaOps.Attestor.FixChain.Tests/FixChainPredicateTests.cs`, `FixChainStatementBuilderTests.cs`, `FixChainValidatorTests.cs`
+  - `__Tests/StellaOps.Attestor.FixChain.Tests/Unit/FixChainAttestationServiceTests.cs`, `FixChainStatementBuilderTests.cs`, `FixChainValidatorTests.cs`
+  - `__Tests/StellaOps.Attestor.FixChain.Tests/Integration/FixChainAttestationIntegrationTests.cs`
+
+## E2E Test Plan
+- [ ] Create a fix chain attestation via `FixChainAttestationService` for a backported security patch and verify the attestation contains patch details
+- [ ] Build an in-toto statement via `FixChainStatementBuilder` and verify correct predicate type
+- [ ] Validate the fix chain attestation via `FixChainValidator` and verify it passes for a valid fix
+- [ ] Create a fix chain with invalid data (e.g., missing patch reference) and verify `FixChainValidator` rejects it
+- [ ] Verify `FixStatusInfo` in the proof chain tracks fix application status
+- [ ] Sign the fix chain statement and verify DSSE envelope integrity
+- [ ] Run integration tests to verify end-to-end fix chain attestation flow
+
+## Verification
+
+| Check | Result |
+|-------|--------|
+| Tier 0 - Source Verification | PASS |
+| Tier 1 - Build + Code Review | PASS |
+| Tier 2 - Behavioral Verification | PASS |
+| Verified Date | 2026-02-13 |
+| Run ID | run-001 |