GitHub: https://github.com/itsamruth/subagent-reuse

Blog post with full context: https://medium.com/@itsamruth/stop-burning-tokens-how-to-use...

I built this after noticing a painful pattern with Claude Code: every new subagent (planner, explorer, implementer, fixer) would re-read the same files from scratch — burning hundreds of tokens each time on files like src/auth/callback.ts.

subagent-reuse solves it by automatically scanning Claude's native session storage (~/.claude/projects/) and tracking exactly which files each subagent has already read and modified. It builds a SHA-256 Merkle tree per agent for fast lookup.

Before spawning a subagent, it runs route_task(task, files). - Strong file overlap → REUSE the existing agent - File changed since last read → staleness warning (only re-read what's needed) - No good match → CREATE_NEW + summaries of existing agents so Claude can decide

I kept routing purely structural (file overlap + directory + recency). No embeddings or word matching — the calling LLM is better at semantics anyway.

Install (one command):

    npx subagent-reuse --setup

It adds the MCP and auto-approves permissions.

This is part of a small stack I'm using to make Claude Code dramatically more efficient (routing + semantic search + memory).

Code is ~1000 lines of vanilla JS with 52 tests.

Would love feedback especially on the routing approach — is staying purely structural the right decision, or should I add something smarter when the task doesn't specify file paths?

Happy to answer any questions!