diff --git a/README.md b/README.md
index 59bb1bc..c8cce72 100644
--- a/README.md
+++ b/README.md
@@ -97,6 +97,8 @@ ai-control is pool management only — it does not change, extend, or circumvent
 
 For that reason the app stores no OAuth tokens itself: with an OAuth pool, the first session of a project on that pool goes through the regular Anthropic login (`/login`, browser, against your subscription), run by Claude Code itself. Credentials live where Claude Code puts them — in the macOS keychain, one entry per pool.
 
+API keys go into the keychain as well (one entry per pool). Only when no keychain/keyring is available does the app offer — after an explicit confirmation — to store the key as a file in the pool directory (mode 0600). We strongly advise against that fallback: an API key on disk is readable by every process running as your user. Use the keychain.
+
 ## License
 
 [MIT](LICENSE)