kmp-adapter-embedded

KMP is local-first agent memory that preserves what happened, when and why. This crate supplies its embedded storage adapters.

One EmbeddedKernelStore opens one data directory — a FORMAT_VERSION marker next to store/ — and implements every persistence port the kernel needs: graph reads over materialized adjacency, node detail, the append-only context event log, projection runtime state, snapshots and quality telemetry. No server, no cluster, no daemon.

Two engines, one seam

The ports are written once against a small storage seam; the engine behind it is chosen when the directory is created and recorded in FORMAT_VERSION, so a store is never reopened by the wrong one.

SQLite is the engine for a fresh user-facing kmp-mcp store: two agent hosts can open the same project memory, readers do not block the writer, and a second writer waits for the commit lock. The crate keeps SQLite feature-gated so a library consumer can still choose a pure-Rust build. Existing redb stores remain readable from their format stamp and never change engine implicitly. Both engines pass the same conformance and kill -9 recovery suites; SQLite also passes a two-process, no-lost-events scenario. See ADR-018.

A binary built without the feature still recognises a SQLite store and refuses it by name, saying which feature to enable; a binary older than the layout refuses it as "newer than this binary supports". Neither ever opens an empty store beside it.

What durability means here

Commits are fsync-durable on both engines (redb immediate durability; SQLite synchronous=FULL in WAL), so the crash contract is explicit: nothing is lost beyond the in-flight event, and replay applies nothing twice.

Not a special case

The observable semantics are pinned by the conformance suite that also certifies the in-memory store and the Neo4j / Valkey adapters. A store that passes it behaves like the others or it does not ship.

License

Apache-2.0.