Japanese version: IChatTurn HashChain Contracts

IChatTurn HashChain Contracts

1. Responsibility Boundary

The ChatChain contracts define the deterministic governance boundary for chat-turn replay evidence:

• IChatTurn captures the actor, body, and timestamp of one conversational turn.
• IHashChainNode links a turn to PrevHash, Hash, and an optional signature.
• IChatTurnCanonicalizer converts a turn into deterministic canonical content.
• IChatTurnSemanticHasher computes the next hash from canonical content and the previous hash.
• IChatTurnSignatureProvider signs and verifies turn hashes.
• IChatTurnChainVerifier validates chain continuity and fail-closed acceptance.
• IChatTurnVerificationResult reports success or the rejection reason.

These interfaces are governance contracts only. They do not own storage, provider execution, prompt generation, or UI state.

2. Governance Flow

Chat-turn governance follows a fixed order:

1. Canonicalize the turn with IChatTurnCanonicalizer.
2. Compute the semantic hash with IChatTurnSemanticHasher.
3. Attach the hash to IHashChainNode with the previous tail hash.
4. Optionally sign the hash with IChatTurnSignatureProvider.
5. Verify continuity and signature acceptance with IChatTurnChainVerifier.

Verification must fail closed. A malformed chain, mismatched previous hash, invalid signature, or policy rejection is represented by IChatTurnVerificationResult.IsSuccess = false and a non-empty Error when available.

3. Determinism Rules

• Canonicalization must be stable for equivalent IChatTurn values.
• Hashing must depend only on canonical content and the previous hash.
• Verification must not introduce hidden state or provider-specific behavior.
• Signatures should use algorithm-tagged formats when encoded outside the interface boundary.

4. Dependency Boundary

• Depends on: System, System.Collections.Generic, System.Threading, System.Threading.Tasks.
• Called by: governance validators, replay-log verifiers, and chat-history ROM pipelines.
• Must not depend on: Core executor implementations, provider implementations, VFS implementations, or hosting-specific services.

5. Migration Notes

v0.0.4 introduced specific names for the ambiguous ChatChain contracts, and v0.0.5 removes the legacy ambiguous interface names from the package surface:

• AIKernel.Abstractions.Governance.ChatChain.IResult -> IChatTurnVerificationResult
• AIKernel.Abstractions.Governance.ChatChain.ISemanticHasher -> IChatTurnSemanticHasher

Use the specific ChatChain names when integrating deterministic replay or chat-history ROM validation. Do not consume or reintroduce the legacy IResult or ISemanticHasher names inside the ChatChain namespace.

Changelog

• v0.0.4 (2026-06-04): Added ChatChain governance contract documentation.
• v0.0.5 (2026-06-05): Clarified removal of the legacy ambiguous ChatChain interface names.