From 918f18c2007cb1f6a640dd9f8506d03e94f3703a Mon Sep 17 00:00:00 2001
From: dave <futurechimp@users.noreply.github.com>
Date: Tue, 19 May 2026 18:14:51 +0000
Subject: [PATCH] =?UTF-8?q?huskies:=20merge=201151=20bug=20install=5Fpre?=
 =?UTF-8?q?=5Fcommit=5Fhook=20blocks=20the=20tokio=20executor=20=E2=80=94?=
 =?UTF-8?q?=20sync=20std::process::Command::output()=20in=20an=20async=20p?=
 =?UTF-8?q?ath=20stalls=20worktree-create-sub?=
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---
 server/src/agents/pool/worktree_lifecycle.rs |  8 +++-
 server/src/worktree/create.rs                | 48 ++++++++++++++++++++
 2 files changed, 55 insertions(+), 1 deletion(-)

diff --git a/server/src/agents/pool/worktree_lifecycle.rs b/server/src/agents/pool/worktree_lifecycle.rs
index 51ab35d2..77749d36 100644
--- a/server/src/agents/pool/worktree_lifecycle.rs
+++ b/server/src/agents/pool/worktree_lifecycle.rs
@@ -129,7 +129,13 @@ pub(crate) async fn on_coding_transition(project_root: &Path, port: u16, story_i
                 "[worktree-create-sub] Worktree ready for '{story_id}' at {}",
                 info.path.display()
             );
-            if let Err(e) = crate::worktree::install_pre_commit_hook(&info.path) {
+            let hook_path = info.path.clone();
+            let hook_result = tokio::task::spawn_blocking(move || {
+                crate::worktree::install_pre_commit_hook(&hook_path)
+            })
+            .await
+            .unwrap_or_else(|e| Err(format!("spawn_blocking panicked: {e}")));
+            if let Err(e) = hook_result {
                 slog_warn!(
                     "[worktree-create-sub] Pre-commit hook install failed for '{story_id}': {e}"
                 );
diff --git a/server/src/worktree/create.rs b/server/src/worktree/create.rs
index 9355ec99..a78c4c61 100644
--- a/server/src/worktree/create.rs
+++ b/server/src/worktree/create.rs
@@ -475,6 +475,54 @@ mod tests {
         );
     }
 
+    /// Regression: before the fix, `install_pre_commit_hook` was called directly
+    /// from an async context, monopolising a tokio worker thread per call.  With
+    /// `worker_threads=2` and two concurrent installs the executor would stall.
+    /// After the fix the installs run on `spawn_blocking`'s thread pool, leaving
+    /// both worker threads free to drive async tasks like the sleep below.
+    #[tokio::test(flavor = "multi_thread", worker_threads = 2)]
+    async fn install_pre_commit_hook_does_not_block_tokio_executor() {
+        let tmp = TempDir::new().unwrap();
+
+        // Helper: create a git repo and a linked worktree inside tmp.
+        let setup = |repo: &str, wt: &str, branch: &str| -> std::path::PathBuf {
+            let repo_path = tmp.path().join(repo);
+            fs::create_dir_all(&repo_path).unwrap();
+            init_git_repo(&repo_path);
+            Command::new("git")
+                .args(["config", "extensions.worktreeConfig", "true"])
+                .current_dir(&repo_path)
+                .output()
+                .unwrap();
+            let wt_path = tmp.path().join(wt);
+            Command::new("git")
+                .args(["worktree", "add", wt_path.to_str().unwrap(), "-b", branch])
+                .current_dir(&repo_path)
+                .output()
+                .unwrap();
+            wt_path
+        };
+
+        let wt1 = setup("repo1", "wt1", "feature/noblock-1");
+        let wt2 = setup("repo2", "wt2", "feature/noblock-2");
+
+        // Both hook installs run on the blocking pool — executor threads stay free.
+        let h1 = tokio::task::spawn_blocking(move || install_pre_commit_hook(&wt1));
+        let h2 = tokio::task::spawn_blocking(move || install_pre_commit_hook(&wt2));
+
+        let start = std::time::Instant::now();
+        tokio::time::sleep(std::time::Duration::from_millis(100)).await;
+        let elapsed = start.elapsed();
+
+        h1.await.unwrap().expect("hook install 1 must succeed");
+        h2.await.unwrap().expect("hook install 2 must succeed");
+
+        assert!(
+            elapsed < std::time::Duration::from_millis(500),
+            "tokio executor was starved; 100 ms sleep took {elapsed:?}"
+        );
+    }
+
     #[test]
     fn install_pre_commit_hook_creates_executable_hook_and_sets_hookspath() {
         let tmp = TempDir::new().unwrap();