@hythe/mcp

HYTHE

A coordination bus + shared truth for your agent fleet. Self-hosted, two-component setup: a dockerized server plus a thin stdio bridge for your MCP clients.

HYTHE is an MCP server that lets multiple AI coding agents — Claude Code, Codex, Cursor, custom harnesses — share state, preserve context across sessions, and coordinate with each other. It is not another memory store. Its differentiators:

• Supersession + current-state resolution: observations supersede each other (replace-current), and get_current_observation resolves the chain server-side — so readers get the newest non-superseded state. Conflict handling is implemented: checkpoint is branch-preserving CAS — concurrent writers branch rather than overwrite, and conflicts surface as heads, never silently resolved (contract-tested; see the evidence ledger).
• Agent messaging with a tracked delivery lifecycle: direct and capability-based sends, message supersession, read-state as a shared signal, atomic ack+archive. (Described as tracked lifecycle, not guaranteed delivery — the states are honest about what the server knows.)
• The Adaptive Coordination Protocol (ACP): the ETA-driven coordination discipline that co-evolved with the server — published as docs/SPEC.md with a real two-harness worked tutorial.

Documentation

Doc	What it covers
Quickstart	Clean machine → two coordinating agents in ~15 minutes
Concepts	One current truth, messaging lifecycle, resume/checkpoint, honest security model
ACP SPEC	The coordination protocol, versioned (1.0.0)
Tutorial	Annotated transcript of a real Claude Code ↔ Codex review loop from the original Engram deployment
Tool compatibility map	The 20-tool v1 surface; every retired tool and its exact replacement
Backup & restore	Tested SQLite backup/restore/compaction runbook
Agent credential operator	Offline issuance, attestation, promotion, rotation, and revocation
Private-residue adjudication	Hash-bound, owner-approved disposition of ambiguous historical rows
SQLite physical sanitation	Verified offline VACUUM and no-clobber promotion after logical cleanup
Pavilion production	Pinned deployment, readiness, shutdown, canary, and rollback contract

Status

Version 0.1.7. This source tree and package define the reviewed 0.1.7 release. Version 0.1.7 preserves 0.1.6's dual-proof agent authorization, exact-mailbox/private-payload containment, bounded related-context discovery, and latency-SLO recovery. It extends the offline adjudicator with an explicit, hash-bound quarantine_backing_observation disposition for a uniquely proven private-shaped observation that backs an otherwise unresolved vector; ambiguous, cross-tenant, stale, or multiply owned evidence still fails closed. The earlier 0.1.4 candidate is superseded and is not a publish target. All 0.1.7 rollout configurations pin @hythe/mcp@0.1.7; verify that the registry returns that exact version before production use. The predecessor @tomcat65/engram-mcp and io.github.tomcat65/engram remain available as compatibility history and are never unpublished.

House rule: every claim in these docs must trace to a test or a measurement (see the evidence ledger below). Claims that don't are bugs.

Evidence ledger

Claim	Evidence	Source	Date
Tree green, full gates	Source and clean installed-package gates cover 49 Vitest files (530 passed, 2 skipped, 6 explicit todos), 107 migration checks, 43 release-tree checks, 31 agent-kit checks, zero production npm audit findings, registry validation, and an isolated Docker start/readiness/MCP/WebSocket/graceful-shutdown canary.	.github/workflows/ci.yml, tests/, src/migrations/, clients/agent-kit/tests/test-setup.sh, scripts/verify-hythe-release-tree.test.mjs, scripts/verify-packed-consumer.mjs	2026-08-14
Compaction identity fails closed	Startup and post-compaction hooks reject missing, conflicting, or invalid identity; the bridge binds acting tools and message-resource recipients to the configured exact lane before any HTTP request.	clients/agent-kit/tests/test-setup.sh, tests/contract-bridge-identity.test.ts	2026-08-13
Exact mailboxes stay isolated	Houston/Hythe, case variants, display metadata, legacy identity history, cross-tenant poisoning, suffix handles, lifecycle changes, supersession, HTTP, and ENG-4 authorship have negative isolation coverage.	tests/contract-message-identity-isolation.test.ts, tests/contract-eng4-p0.test.ts	2026-08-13
Private message bodies stay out of shared graph surfaces	Historical, oversized, malformed, alias-linked, relation-linked, imported, exported, searched, graphed, logged, and restored payload paths are covered; hidden children do not leak through counts.	tests/contract-message-payload-isolation.test.ts, tests/contract-data-payload-isolation.test.ts, tests/contract-log-confidentiality.test.ts	2026-08-13
Cleanup is offline and fail-closed	Migration 007, owner-approved adjudication, and physical sanitation are dry-run/plan-first, bind execution to reviewed database and decision evidence, require verified no-clobber artifacts, refuse unresolved custody, and preserve rollback state.	src/migrations/007-private-message-residue.mjs, src/migrations/private-message-residue-adjudication.mjs, src/migrations/vacuum-sanitized-database.mjs, docs/	2026-08-14
Per-agent authority is server-derived	The base key proves deployment/tenant access; a separate protected-file hya1 credential proves the exact agent. Required mode rejects stripped proof, mismatched identity, insufficient scope, revoked credentials, and stale WebSocket sessions.	src/agent-auth/, tests/contract-agent-auth-foundation.test.ts, tests/contract-agent-auth-server.test.ts, tests/contract-agent-key-client.test.ts	2026-08-14
Install and discovery surfaces agree	CLI and registry surfaces require an exact lane identity and expose only a protected per-agent key-file path plus an explicit authorization mode; tools and resource templates served through HTTP match the stdio bridge path.	tests/contract-cli.test.ts, tests/contract-agent-key-client.test.ts, tests/contract-mcp-resources-http.test.ts, scripts/verify-hythe-release-tree.test.mjs	2026-08-14

v1 surface (short)

• Install (two-component setup): server via docker compose up, then the @hythe/mcp stdio bridge per MCP client; first-run wizard stores the API key in a protected .env and prints secret-free file-referencing config for Claude Code / Codex / Cursor / Claude Desktop; optional namespaced (demo-*) demo seed on an otherwise empty DB.
• Knowledge graph: entities, observations, relations, supersession, current-state resolution, conflict surfacing.
• Related-context discovery: exact scope anchoring plus automatic bounded vector retrieval and graph-path reranking, with currentness/evidence/provenance explanations and no implicit writes.
• Agent messaging: direct, capability-based, superseding; tracked delivery lifecycle.
• resume / checkpoint: budgeted one-call session rehydration with closed coverage accounting, and CAS-protected, branch-preserving structured state capture.
• ACP: the coordination protocol as a versioned spec + real worked example.

Embedding runtime contract

The published npm package does not install a transformer engine by default. Without one, HYTHE still provides deterministic 384-dimension token-hash vectors plus lexical ranking; it does not download a model or create a model cache. @xenova/transformers@2.17.2 is an optional peer for operators who deliberately provide it from their own audited dependency root.

The Docker image keeps semantic behavior stable through a separate, locked /opt/hythe-transformers runtime. Its startup preflight loads the configured Xenova/all-MiniLM-L6-v2 q8 model and requires one finite 384-dimension embedding before the server starts. When SQLITE_VEC_ALLOW_REMOTE_MODELS=false, the configured SQLITE_VEC_CACHE_DIR must already contain that model. Do not switch between transformer and hash embeddings on a populated vector index: retain the same provider/model/dimensions or rebuild the vector index first.

License

Apache-2.0