fix(hooks): skip gate outside a Git repository

crates/cli/src/hooks.rs

@@ -92,7 +92,9 @@ fn report_post_edit(input: &HookInput, paths: &[PathBuf]) -> Result<()> {
 }
 
 fn report_post_changed(input: &HookInput) -> Result<()> {
-    let changes = changed_files(&input.cwd)?;
+    let Some(changes) = repo_changes(&input.cwd)? else {
+        return Ok(());
+    };
     let result = scan(&ScanOptions {
         cwd: &input.cwd,
         paths: &[],
@@ -106,7 +108,10 @@ fn report_post_changed(input: &HookInput) -> Result<()> {
 }
 
 fn report_stop(input: &HookInput) -> Result<()> {
-    let changes = changed_files(&input.cwd)?;
+    let Some(changes) = repo_changes(&input.cwd)? else {
+        reset_counter(&input.session_id)?;
+        return Ok(());
+    };
     let result = scan(&ScanOptions {
         cwd: &input.cwd,
         paths: &[],
@@ -128,6 +133,21 @@ fn report_stop(input: &HookInput) -> Result<()> {
     ))
 }
 
+/// Hooks gate only the diff of the repository around `cwd`. Outside a Git
+/// repository (or with no `HEAD`) there is nothing to diff, so hooks pass
+/// instead of scanning the whole tree the way the CLI fallback does.
+fn repo_changes(cwd: &Path) -> Result<Option<complexity_gate_core::ChangedFiles>> {
+    let changes = changed_files(cwd)?;
+    if changes.fallback {
+        eprintln!(
+            "note: hook skipped: {} is not inside a Git repository with HEAD",
+            cwd.display()
+        );
+        return Ok(None);
+    }
+    Ok(Some(changes))
+}
+
 fn emit_block(reason: &str) -> Result<()> {
     println!(
         "{}",

crates/cli/tests/cli.rs

@@ -183,8 +183,16 @@ fn changed_ignored_paths_are_filtered_before_language_lookup() {
     fs::write(dir.path().join("target/Foo.kt"), "fun changed() = 2\n").unwrap();
 
     let output = command_output(dir.path(), &["check", "--changed"]);
-    assert!(output.status.success(), "stderr: {}", String::from_utf8_lossy(&output.stderr));
-    assert!(output.stdout.is_empty(), "stdout: {}", String::from_utf8_lossy(&output.stdout));
+    assert!(
+        output.status.success(),
+        "stderr: {}",
+        String::from_utf8_lossy(&output.stderr)
+    );
+    assert!(
+        output.stdout.is_empty(),
+        "stdout: {}",
+        String::from_utf8_lossy(&output.stdout)
+    );
 }
 
 #[test]
@@ -202,7 +210,11 @@ fn changed_non_utf8_diff_does_not_abort_check_or_stop_hook() {
     git(dir.path(), &["add", "staged.js"]);
 
     let check = command_output(dir.path(), &["check", "--changed"]);
-    assert!(check.status.success(), "stderr: {}", String::from_utf8_lossy(&check.stderr));
+    assert!(
+        check.status.success(),
+        "stderr: {}",
+        String::from_utf8_lossy(&check.stderr)
+    );
     assert_eq!(
         String::from_utf8_lossy(&check.stdout),
         "UNVERIFIED staged.js  not valid UTF-8\n"
@@ -213,7 +225,11 @@ fn changed_non_utf8_diff_does_not_abort_check_or_stop_hook() {
     })
     .to_string();
     let stop = hook_output(state.path(), &input);
-    assert!(stop.status.success(), "stderr: {}", String::from_utf8_lossy(&stop.stderr));
+    assert!(
+        stop.status.success(),
+        "stderr: {}",
+        String::from_utf8_lossy(&stop.stderr)
+    );
     assert!(stop.stdout.is_empty());
 }
 
@@ -388,3 +404,24 @@ fn complex_function() -> String {
         .join("\n");
     format!("function bad(x) {{\n{decisions}\nreturn x;\n}}\n")
 }
+
+#[test]
+fn stop_hook_outside_git_repository_passes_without_scanning() {
+    let dir = tempfile::tempdir().unwrap();
+    let state = tempfile::tempdir().unwrap();
+    fs::write(
+        dir.path().join("bad.js"),
+        "function bad(x) { if (x) { if (x > 1) { if (x > 2) { if (x > 3) { if (x > 4) { return 1; } } } } } return 0; }\n",
+    )
+    .unwrap();
+    let input = serde_json::json!({
+        "hook_event_name":"Stop", "session_id":"no/repo", "cwd":dir.path()
+    })
+    .to_string();
+
+    let output = hook_output(state.path(), &input);
+    assert!(output.status.success());
+    assert!(output.stdout.is_empty());
+    assert!(String::from_utf8_lossy(&output.stderr).contains("note: hook skipped"));
+    assert!(!state.path().join("no_repo.count").exists());
+}

docs/spec.md

@@ -141,6 +141,10 @@ complexity-gate --version
   its line span intersects the post-image range of any added/modified hunk. Pure
   deletions touch nothing. Outside a Git repository, or with no `HEAD`, `--changed`
   falls back to all given paths (or the cwd) and prints a `note:` line on stderr.
+  Hook mode (`hook claude|codex`) does not fall back: outside a Git repository
+  it prints a `note: hook skipped` line, emits no block, and a Stop resets the
+  loop counter, so a session running from a non-repo cwd is never gated on the
+  whole tree.
   The changed file set comes straight from Git: `git diff HEAD` post-image paths
   (which already include tracked files that a later `.gitignore` rule covers)
   plus untracked files from `git ls-files --others --exclude-standard`; config