diff --git a/server/src/agents/pool/pipeline/completion/tests.rs b/server/src/agents/pool/pipeline/completion/tests.rs
index 0d560737..8cad2265 100644
--- a/server/src/agents/pool/pipeline/completion/tests.rs
+++ b/server/src/agents/pool/pipeline/completion/tests.rs
@@ -496,6 +496,127 @@ async fn watchdog_kill_preserves_uncommitted_diff() {
     );
 }
 
+/// Story 910 regression: a coder that exits with zero commits on the feature
+/// branch must NOT be promoted to Merge.  The server-owned completion path
+/// detects `git rev-list master..HEAD == 0`, records `gates_passed=false`,
+/// and the pipeline advance retries (or blocks at the cap) instead of
+/// advancing the story.
+#[tokio::test]
+async fn zero_commit_coder_exit_stays_in_coding_not_promoted_to_merge() {
+    use std::fs;
+    use std::process::Command;
+
+    let tmp = tempfile::tempdir().unwrap();
+    let project_root = tmp.path().join("project");
+    fs::create_dir_all(&project_root).unwrap();
+
+    // Init a git repo with an initial master commit.
+    Command::new("git")
+        .args(["init"])
+        .current_dir(&project_root)
+        .output()
+        .unwrap();
+    Command::new("git")
+        .args(["config", "user.email", "test@test.com"])
+        .current_dir(&project_root)
+        .output()
+        .unwrap();
+    Command::new("git")
+        .args(["config", "user.name", "Test"])
+        .current_dir(&project_root)
+        .output()
+        .unwrap();
+    Command::new("git")
+        .args(["commit", "--allow-empty", "-m", "init"])
+        .current_dir(&project_root)
+        .output()
+        .unwrap();
+
+    // Create a feature-branch worktree with ZERO commits ahead of master.
+    let wt_path = tmp.path().join("wt");
+    Command::new("git")
+        .args([
+            "worktree",
+            "add",
+            &wt_path.to_string_lossy(),
+            "-b",
+            "feature/story-9910_zero_exit",
+        ])
+        .current_dir(&project_root)
+        .output()
+        .unwrap();
+
+    // Set up the story with max_retries=1 so it blocks on the first failure.
+    crate::crdt_state::init_for_test();
+    crate::db::ensure_content_store();
+    crate::db::write_item_with_content(
+        "9910_zero_exit",
+        "2_current",
+        "---\nname: Zero Exit Test\n---\n",
+        crate::db::ItemMeta::from_yaml("---\nname: Zero Exit Test\n---\n"),
+    );
+
+    fs::create_dir_all(project_root.join(".huskies")).unwrap();
+    fs::write(
+        project_root.join(".huskies/project.toml"),
+        "max_retries = 1\n\n[[agent]]\nname = \"coder-1\"\nstage = \"coder\"\n",
+    )
+    .unwrap();
+
+    let pool = AgentPool::new_test(3001);
+    pool.inject_test_agent_with_root_and_path(
+        "9910_zero_exit",
+        "coder-1",
+        AgentStatus::Running,
+        project_root.clone(),
+        wt_path.clone(),
+    );
+
+    let mut rx = pool.watcher_tx.subscribe();
+
+    run_server_owned_completion(
+        &pool.agents,
+        pool.port,
+        "9910_zero_exit",
+        "coder-1",
+        None,
+        pool.watcher_tx.clone(),
+    )
+    .await;
+
+    // The pipeline advance spawns asynchronously — poll with a timeout.
+    let mut got_blocked = false;
+    let deadline = tokio::time::Instant::now() + std::time::Duration::from_secs(5);
+    while tokio::time::Instant::now() < deadline {
+        while let Ok(evt) = rx.try_recv() {
+            if let crate::io::watcher::WatcherEvent::StoryBlocked { story_id, .. } = &evt
+                && story_id == "9910_zero_exit"
+            {
+                got_blocked = true;
+            }
+        }
+        if got_blocked {
+            break;
+        }
+        tokio::time::sleep(std::time::Duration::from_millis(50)).await;
+    }
+
+    assert!(
+        got_blocked,
+        "Story 910 regression: a zero-commit coder exit must block/retry \
+         the story rather than advancing it to Merge"
+    );
+
+    // The story must NOT be in 4_merge.
+    if let Ok(Some(item)) = crate::pipeline_state::read_typed("9910_zero_exit") {
+        assert_ne!(
+            item.stage.dir_name(),
+            "4_merge",
+            "Story must NOT be in Merge after a zero-commit coder exit"
+        );
+    }
+}
+
 /// AC4 (bug 651 regression for 645): when an agent crashes with committed
 /// work AND uncommitted noise, the auto-advance still picks up the
 /// committed work.  The committed-state check is authoritative; the
diff --git a/server/src/agents/pool/test_helpers.rs b/server/src/agents/pool/test_helpers.rs
index 414cf214..d322f7c4 100644
--- a/server/src/agents/pool/test_helpers.rs
+++ b/server/src/agents/pool/test_helpers.rs
@@ -199,6 +199,48 @@ impl AgentPool {
             .and_then(|a| a.status_buffer.as_ref().map(|b| b.drain()))
     }
 
+    /// Test helper: inject an agent with a project root AND a worktree path.
+    ///
+    /// Use this when the full server-owned completion path needs both a
+    /// `project_root` (so `run_pipeline_advance` can load config and advance
+    /// the story) and a `worktree_info` (so gate checks can inspect the branch).
+    pub fn inject_test_agent_with_root_and_path(
+        &self,
+        story_id: &str,
+        agent_name: &str,
+        status: AgentStatus,
+        project_root: PathBuf,
+        worktree_path: PathBuf,
+    ) -> broadcast::Sender<AgentEvent> {
+        let (tx, _) = broadcast::channel::<AgentEvent>(64);
+        let key = composite_key(story_id, agent_name);
+        let mut agents = self.agents.lock().unwrap();
+        agents.insert(
+            key,
+            StoryAgent {
+                agent_name: agent_name.to_string(),
+                status,
+                worktree_info: Some(WorktreeInfo {
+                    path: worktree_path,
+                    branch: format!("feature/story-{story_id}"),
+                    base_branch: "master".to_string(),
+                }),
+                session_id: None,
+                tx: tx.clone(),
+                task_handle: None,
+                event_log: Arc::new(Mutex::new(Vec::new())),
+                completion: None,
+                project_root: Some(project_root),
+                log_session_id: None,
+                merge_failure_reported: false,
+                throttled: false,
+                termination_reason: None,
+                status_buffer: None,
+            },
+        );
+        tx
+    }
+
     /// Inject a Running agent with a pre-built (possibly finished) task handle.
     /// Used by watchdog tests to simulate an orphaned agent.
     pub fn inject_test_agent_with_handle(