Skip to content

Glossary

Every load-bearing term used in the SiftCoder docs, alphabetised. If a term shows up in the foundations or operations chapters and you can't infer its meaning, look here.

Anthropic backend — One of the drain options. When memory.drainBackend resolves to anthropic, the consolidator (or the MCP server) calls the Anthropic SDK directly using ANTHROPIC_API_KEY. Models are configured via memory.summarizer.modelHaiku and modelSonnet. Higher-quality summaries than Ollama, but costs money and ships content out of the box.

BM25 — A classic lexical ranking function over an inverted index. SiftCoder uses SQLite's FTS5 BM25 implementation as one of two retrieval legs (the other being vector similarity). Strong for exact-keyword queries; weak when the user phrases something differently from the corpus.

Backfill — The act of replaying past Claude Code transcripts (~/.claude/projects/<encoded-cwd>/*.jsonl) into the memory store. Triggered by siftcoder backfill or the BackfillRequest RPC. Useful right after first install — without it, retrieval finds nothing because the store is empty.

Capture — The act of recording a tool call as an event. Performed by the PostToolUse hook (capture-observation.mjs). Sends a CaptureRequest frame over UDS; the daemon redacts secrets, deduplicates on input_hash, and writes to the events table with status raw.

CDG (Code Document Graph) embedder — A code-aware embedding model. Second-priority embedder in the cascade. Falls between Ollama (when available) and the deterministic embedder. Produces vectors that respect code structure better than generic embedders.

Chroot — A SiftCoder-specific tighter scope mechanism: instead of glob-based allowlists (which is what scope.json does), chroot.json lists exact file paths. Used for "AI may only touch these 12 files".

Consolidator — The component inside the daemon that runs on a tick (default 30 s) and summarises raw events into the summaries table. Configurable via memory.consolidator.tickMs and batchSize.

Daemon — The single Node process per workspace that owns the SQLite handle, the WAL file, the socket, and the consolidator. Spawned by hooks/session-start/spawn-daemon.mjs or siftcoder start. Lives at dist/memory/daemon/index.js.

Deterministic embedder — A pure-JS, 384-dimensional embedder that hashes tokens into vector slots. Always available — needs no external service. Lower retrieval quality than Ollama or CDG, but the floor is reliable. The drain-time embedder when nothing better is up.

Drain — Force-running the consolidator now (rather than waiting for the next tick). Triggered by siftcoder drain [batch], the mem_drain MCP tool, or the small per-call drain inside mem_search. Reads pending events, summarises, embeds, marks summarized.

Embedding — A fixed-length float vector representing the semantic content of a summary. Stored in summary_embeddings.vec as a packed float32 BLOB with the dimension in dim. Used for the cosine-similarity leg of retrieval.

Event — A row in the events table — one tool call. Columns: id, ts, session_id, tool, input_hash, payload_json, tokens_est, status. The unit of capture; many events become summaries.

FTS5 — SQLite's full-text-search virtual-table extension. Backs the BM25 leg of retrieval. SiftCoder maintains an FTS5 table over summary text; the daemon updates it as summaries are written.

Hook — A short Node script the harness runs synchronously around tool calls. SiftCoder ships hooks for PreToolUse, PostToolUse, PreCompact, Notification, SessionStart, and Stop. See hooks.md.

MCP (Model Context Protocol) — Anthropic's protocol for letting Claude call external tools. SiftCoder registers a server named siftcoder-memory that exposes mem_search, mem_get, mem_timeline, mem_drain, mem_why. JSON-RPC over stdio.

Namespace — Top-level isolation for runtime state. Set via SIFTCODER_NS. Defaults to default. Maps to ~/.siftcoder/<namespace>/. Useful for separating work from personal, or tenants in a shared dev box.

Ollama — A local LLM runner. SiftCoder treats it as the preferred drain backend when reachable at OLLAMA_HOST (default http://localhost:11434) — no token cost, no data egress. Default model llama3.2:3b for summaries, nomic-embed-text for embeddings.

RRF (Reciprocal Rank Fusion) — The fusion method SiftCoder uses to combine BM25 and vector retrieval results. Formula: score(d) = Σ_legs 1 / (rrfK + rank_leg(d)). Works without score normalisation — it only needs ranks. The rrfK constant defaults to 60.

Sampling (MCP) — A capability where an MCP server can request LLM calls back through the host. SiftCoder uses this so the daemon doesn't need its own API key — it borrows the host's. Outbound JSON-RPC method is sampling/createMessage. Requires the host to advertise sampling capability on initialize.

Scope file — .siftcoder/scope.json (project) or ~/.siftcoder/<ns>/scope.json (global). JSON object with allow-globs that the boundary-enforcer reads to decide which paths Write/Edit may touch. Strict JSON — comments break it silently.

Session — A Claude Code session id, propagated through hook invocations. Used in events.session_id for grouping. Multiple sessions can run against the same workspace.

Summariser — The class that takes a raw event payload and produces a short text summary. Implemented in dist/memory/daemon/summarizer.js. Calls whichever model client is configured (Ollama / Anthropic / sampling).

Summary — A condensed text representation of one or more events. Stored in the summaries table. The unit of retrieval — search and timeline operate over summaries, not raw events.

Time decay — An exponential weighting applied to retrieval scores so older summaries fade. score' = score * exp(-Δt / tauMs). Default tauMs = 7 days (halfLifeDays = 7). Tuneable in memory.decay.

WAL (Write-Ahead Log) — Two distinct things in this codebase: 1. SiftCoder's own per-workspace wal.ndjson — every captured event as a JSON line, fsync'd. Lets the daemon survive a crash mid-capture. 2. SQLite's WAL mode — db.sqlite-wal and db.sqlite-shm. Enabled because it gives concurrent readers + writer without locking pain.

Workspace — A repo, identified by the SHA-256 of the realpath of its git toplevel, truncated to 12 hex characters. One workspace ↔ one daemon ↔ one socket ↔ one DB file. Two terminals in the same repo share the workspace.