diff --git a/core/instructions/git.md b/core/instructions/git.md
index 70bb295..a162a70 100644
--- a/core/instructions/git.md
+++ b/core/instructions/git.md
@@ -5,3 +5,9 @@
 - Commit messages explain why, not what. Written for both humans and changelog generators.
 - Never commit secrets, credentials, or environment-specific config.
 - Use conventional commits: `feat:`, `fix:`, `docs:`, `chore:`, `refactor:`, `test:`
+
+## Submodules
+
+- When working with submodules: commit and push the submodule first, then update and push the parent repo. Pushing the parent while the submodule commit doesn't exist on the remote breaks `git submodule update` for anyone who pulls.
+- Always use `rtk git` for parent repo operations; drop into the submodule directory for submodule-specific git commands.
+- After adding a submodule, check `git status` in both the parent and the submodule — a `-dirty` flag means the submodule has uncommitted local changes that need to be committed before the parent pointer is updated.