sqlite-memory compatibility assessment

Upstream inspected: sqliteai/sqlite-memory tag 1.3.5 (released 2026-06-10).

Decision

Reject as a Hippo runtime dependency. Adapt its proven design ideas.

The extension solves a similar problem, but adopting it would create a second memory/retrieval subsystem inside Hippo. Its useful ideas—Markdown-heading boundaries, content-hash no-ops, path-preserving identity, savepoint-scoped replacement, deferred embeddings, and cleanup on directory reconciliation—fit Hippo’s existing SQLite architecture and should be implemented against Hippo’s own source, knowledge-node, FTS5, sqlite-vec, inference, and MCP contracts.

Evidence

What aligns

Markdown parsing uses md4c, splits on semantic heading boundaries, and then enforces a configurable size/overlap budget.
File ingestion hashes content, skips unchanged input, atomically replaces modified chunks, removes deleted files during directory sync, and supports distinct logical paths for identical content.
Deferred indexing separates source durability from embedding availability.
FTS5 and vectors are combined in one hybrid query surface.
The extension supports a custom embedding-provider C callback, so its built-in llama.cpp/vectors.space providers are not the only theoretical integration path.

What conflicts

Concern	sqlite-memory 1.3.5	Hippo contract / impact
Vector extension	Requires `sqlite-vector` for semantic search	Hippo already owns `sqlite-vec` tables, migrations, integrity checks, and retrieval
Storage schema	Owns `dbmem_*` settings/content/vault/FTS tables	Would duplicate `knowledge_nodes`, link tables, FTS5, queue state, and source provenance
Retrieval	Own virtual table and weighted vector/text merge	Hippo uses filter pushdown, RRF, MMR, source hydration, and existing MCP/RAG APIs
Embeddings	Built-in llama.cpp or vectors.space; custom provider requires C callbacks	Hippo uses configurable OpenAI-compatible local providers and 768d embeddings from Python
Revision history	Modified files replace prior content	SNUG-130 requires bounded revision metadata, summaries, and diffs
Source health	Directory sync state, not Hippo watchdog/probe semantics	Hippo requires independent source health, alarms, doctor output, and synthetic-row exclusion
Packaging	C/C++ dynamic extension; full local build includes llama.cpp/Metal and optional curl	Adds binaries, submodules, signing/loading, release, and cross-platform support burden
Schema stability	Upstream documents a rebuild requirement for databases created before 1.0	Hippo requires ordered migrations and rollback-compatible ownership

License blocker

The upstream README says “MIT License,” but tag 1.3.5’s LICENSE.md is a modified Elastic License 2.0. It grants free use when incorporated into an OSI-licensed open-source project but requires a commercial license for non-open-source or commercial production use and restricts managed-service use. That mismatch is enough to reject direct dependency until upstream publishes a single unambiguous license. Hippo should not advertise or inherit an MIT-only dependency claim from the README.

Maturity

At inspection time the repository showed 66 commits, 21 releases, approximately 74 stars, five forks, and version 1.3.5. Rapid releases are positive, but the small adoption base, recent pre-1.0 schema break, and license contradiction make it unsuitable as a foundational storage dependency today.

Behavior matrix

Behavior	Upstream evidence	Hippo spike evidence	Required Hippo behavior
Update	Hash check and savepoint replacement	Scratch replacement removes stale FTS chunks	Preserve old searchable projection until new enrichment commits
Delete	Directory cleanup removes stored file/chunks	Cascading delete removes FTS rows	Tombstone current document; retain bounded history
Rename	Explicit logical rename without reprocessing	Scratch rename preserves content and changes stable path IDs	Preserve document history only when identity is unambiguous
Duplicate path/content	Optional path-scoped hash	Two identical files remain separately searchable	Path identity is authoritative; content hash is revision identity
Transaction failure	Savepoint rollback	Injected failure restored old document/chunks	No partial source, chunks, vectors, or node links
Deferred embedding	Stores unindexed content pending later embedding	Deferred document is durable but not searchable	Keep last known-good projection visible during pending replacement
Revision history	Not provided	Outside scratch-index scope	Bounded metadata/summary/diff, explicit-history query only

Build limitation

The planned local clone/build could not start because the execution environment could not resolve github.com. Source, Makefile, API, release, and license files were inspected through the configured GitHub connector at tag 1.3.5. No claim is made that the extension compiled or loaded on this host.