BCR-2026-XXX: Anchor Predicates

[ChristopherA]

Proposes Known Values for anchoring assertions to cryptographic event logs in Gordian Envelopes.

Predicates defined:

• anchoredIn — Reference to event log containing the anchor
• anchorDigest — Cryptographic digest anchored in the log
• anchorTimestamp — Timestamp when anchored
• anchorHeight — Block/sequence number in the log
• anchorProof — Merkle proof or similar verification data
• anchorWitnesses — Entities that witnessed the anchoring
• anchorChain — Name/identifier of the anchoring system

Codepoints: Core registry 87-93 (XID Documents section)

Seeking community review.

[shannona]

I don't really understand the use case here. I know you're talking about append-only logs, but the way the examples are written, people are going to read these as logs that could be rewritten. I think this needs some specifics to really make it clear what you're saying.

[ChristopherA]

Updates (Feb 4, 2026)

Per reviewer feedback:

1. Notation: Changed CID(...) → Digest(...) per Issue BCR notation question: Content-addressed envelope references in examples #157 resolution
2. Terminology: Renamed anchorHash → anchorDigest with native Digest type (not wrapped in assertion)
3. Scope clarification: Added "Why Anchoring Matters" and "Use Cases" sections; clarified this is Envelope-native anchoring, not CT/CEL interop
4. Append-only emphasis: Strengthened language around append-only anchor stores

[ChristopherA]

Per Wolf's feedback: removed { } envelope wrapping from examples that don't include signatures. Wrapping is only needed when showing signed envelopes.

[ChristopherA]

Renumbered: BCR-2026-004 → BCR-2026-011

This BCR has been renumbered to 011 (last in the suite) because:

• Uses core registry codepoints (87-93) requiring community review
• Other BCRs in this suite are ready for earlier release

File renamed: bcr-2026-004-anchor-predicates.md → bcr-2026-011-anchor-predicates.md

Cross-references updated throughout the BCR suite. Branch name preserved for PR history.