diff --git a/docs/internal/MULTITENANT-HANDOFF.md b/docs/internal/MULTITENANT-HANDOFF.md
index c8701ce..7fc4eba 100644
--- a/docs/internal/MULTITENANT-HANDOFF.md
+++ b/docs/internal/MULTITENANT-HANDOFF.md
@@ -17,6 +17,15 @@ Each agent must set `user.name` in the repo before committing:
 git config user.name "Operator & <agent>"
 ```
 
+`user.name` lives in `.git/config` (per-clone, not per-host). If zAI and
+Claude share a clone on the same Linux box, whoever set `user.name` most
+recently wins — so each agent must run the command above at the start of
+its own session, not rely on an earlier agent's value. A quick guard is
+committed below: `hooks/pre-commit` now refuses any commit whose
+`user.name` does not start with `Operator & ` (or the legacy
+`Clawdie AI`), so a forgotten reset produces a fast error instead of a
+misattributed commit.
+
 ## In flight
 
 This branch is worked on by more than one agent in parallel. Before
diff --git a/hooks/pre-commit b/hooks/pre-commit
index 99dec5e..55bf8e9 100755
--- a/hooks/pre-commit
+++ b/hooks/pre-commit
@@ -1,6 +1,18 @@
 #!/bin/sh
-# Auto-update README Current Release version from package.json
+# Attribution guard: fail fast if user.name was not set for this session.
+# Each agent must run `git config user.name "Operator & <agent>"` before
+# committing — see docs/internal/MULTITENANT-HANDOFF.md § Agent Identity.
+AUTHOR_NAME=$(git config user.name || true)
+case "$AUTHOR_NAME" in
+  "Operator & "*|"Clawdie AI") ;;
+  *)
+    echo "pre-commit: git user.name is '$AUTHOR_NAME' — expected 'Operator & <agent>'." >&2
+    echo "  Run: git config user.name \"Operator & <agent>\"" >&2
+    exit 1
+    ;;
+esac
 
+# Auto-update README Current Release version from package.json
 VERSION=$(node -e "process.stdout.write(require('./package.json').version)")
 if [ -z "$VERSION" ]; then exit 0; fi