Memtrace: Persistent, Time-Aware Codebase Memory for Claude Code Agents

Every long Claude Code session suffers from stale context: the agent re-reads the same files, forgets interface details, and refactors without understanding blast radius. Memtrace is a free, open-source memory layer that fixes this by maintaining a continuously updated, time-aware representation of your codebase.

Two Core Capabilities

• Always-fresh state: Every edit triggers a 42ms incremental snapshot of changes applied by the agent. The agent never works from session-old memory — after a refactor, it knows every caller, test, and consumer of the touched function immediately.
• Rewind and replay: The codebase is stored bi-temporally (valid_time + transaction_time per node/edge), allowing queries like “what did this function look like Monday” and replaying how a broken function evolved commit-by-commit.

Architecture & Performance Bets

Zero LLM inference during indexing: Tree-sitter parses code into an AST, which becomes the structural representation. Retrieval is hybrid — Tantivy BM25 for lexical recall and Jina-code 768-dim embeddings indexed in HNSW for semantic recall, fused with Reciprocal Rank Fusion at k=60. Jina-code is trained on code, so it understands “this is an auth handler” without pattern-matching the word “auth.”

Bi-temporal layer enables typed edges (CALLS, IMPORTS, IMPLEMENTS, EXTENDS, CONTAINS, TYPE_REFERENCES, INSTANTIATES) traversed in graph time, giving the agent blast radius before refactoring. Speed is critical: indexing path bottlenecks on I/O, not LLM tokens, making snapshotting cheap enough to run on every edit.

Approval & Limits

The binary requires an approval key due to edge cases from real beta users (mixed pnpm/npm lockfiles, Rust proc-macros, Python TYPE_CHECKING blocks). Approvals are capped at 50 per week, with a target under 24h. The benchmark harness is fully open and runnable without the key. Repo + waitlist: github.com/syncable-dev/memtrace-public