I keep a plain Obsidian vault — about 1.4 MB of markdown across notes, projects and an inbox — and I let coding agents (the Claude Code / Cursor kind) work inside it: searching, summarizing, drafting. The first thing I measured changed how I set all of this up: an agent that reads the whole vault isn't being thorough. It's drowning.
Every file it opens costs context. Read enough files and the actual question gets buried under files that were never relevant. Three boring fixes, each measured on my own setup:
1. A derived index instead of the raw vault
A small script walks the vault and writes one line per note: title, what it's about, size, last change. That map is ~9 KB standing in for ~1.4 MB — the same answer to "what exists here and where," for about 150× less context. It's generated, never hand-maintained: I rerun the script after heavy edits, because a stale map is worse than none — it asserts confidently things that stopped being true.
2. A reading ladder, cheapest rung first
