diff --git a/docs/superpowers/specs/2026-05-25-mibook-claude-code-design.md b/docs/superpowers/specs/2026-05-25-mibook-claude-code-design.md
index ea73c63..9e04ace 100644
--- a/docs/superpowers/specs/2026-05-25-mibook-claude-code-design.md
+++ b/docs/superpowers/specs/2026-05-25-mibook-claude-code-design.md
@@ -44,6 +44,8 @@ No sub-options for Phase 1. Phase 2 would add `my.profiles.claude-code.service.e
 
 `git`, `nodejs`, and `docker` are already provided by existing modules and are not duplicated.
 
+**Contingency:** If `pkgs.unstable.claude-code` does not exist at eval time, the fallback is a custom derivation in `pkgs/claude-code/default.nix` added to the local overlay — the same mechanism used for other absent packages.
+
 ## No Secrets Management
 
 The Anthropic API key is handled manually by the user (browser login / `claude` interactive setup). No sops-nix or shell-profile injection needed.