diff --git a/CLAUDE.md b/CLAUDE.md
index fdf64b1ff..4032af044 100644
--- a/CLAUDE.md
+++ b/CLAUDE.md
@@ -43,6 +43,13 @@ ps aux | grep "heap-prof-interval" | grep -v grep
 # Kill them: ... | awk '{print $2}' | xargs kill -9
 ```
 
+**Do not use Python for one-off JSON/hash work.** The resource fingerprint in
+`~/.sf/agent/managed-resources.json` is computed by Node's SHA-256 — Python's
+`hashlib` produces a different result for the same files, which breaks the
+fast-path check in `initResources` and causes a 30-60 s full resync on every
+launch. Use `node -e` (or `jq`) for any shell-level JSON/hash operations in
+this repo.
+
 ## Key directories
 
 | Path | Purpose |