diff --git a/.huskies/specs/tech/STATE_MACHINE.md b/.huskies/specs/tech/STATE_MACHINE.md
index 18c30055..e3b31c31 100644
--- a/.huskies/specs/tech/STATE_MACHINE.md
+++ b/.huskies/specs/tech/STATE_MACHINE.md
@@ -181,6 +181,25 @@ The mergemaster agent only runs against stories in `4_merge/`. It:
 4. On failure beyond the retry budget, writes `merge_failure` and blocks the
    story (auto-assign then skips it).
 
+### Agent terminated with committed work (bug 645 recovery path)
+
+When a coder agent terminates abnormally (e.g. the Claude Code CLI's
+`output.write(&bytes).is_ok()` PTY write assertion fires mid-session), the
+server-owned completion path detects the crash and checks for surviving work:
+
+1. If the worktree is dirty but has commits ahead of master, reset the
+   uncommitted files (`git checkout . && git clean -fd`) and run gates
+   against the committed code.
+2. If gates still fail but `git log master..HEAD` shows commits and
+   `cargo check` passes, **advance to QA** instead of entering the
+   retry/block path.  This is the "work survived" check, implemented in
+   `server/src/agents/pool/pipeline/advance.rs`.
+3. Agents that die WITHOUT committed work (no commits ahead of master)
+   still follow the existing retry → block path unchanged.
+
+This prevents false-positive blocking of stories where the agent completed
+meaningful work before crashing.
+
 ### Watchdog (current production)
 
 The "watchdog" at `server/src/agents/pool/auto_assign/watchdog.rs` runs every
diff --git a/server/src/agents/gates.rs b/server/src/agents/gates.rs
index 074daeaf..d587a3dc 100644
--- a/server/src/agents/gates.rs
+++ b/server/src/agents/gates.rs
@@ -41,6 +41,26 @@ pub(crate) fn worktree_has_committed_work(wt_path: &Path) -> bool {
     }
 }
 
+/// Run `cargo check` in the given worktree directory to verify committed code compiles.
+///
+/// Resets any dirty (uncommitted) files first via `git checkout .` so that only
+/// the committed state is evaluated.  Used as part of the "work survived" check
+/// when an agent crashes mid-output (bug 645).
+pub(crate) fn cargo_check_in_worktree(wt_path: &Path) -> bool {
+    // Reset uncommitted changes so cargo check evaluates only committed code.
+    let _ = Command::new("git")
+        .args(["checkout", "."])
+        .current_dir(wt_path)
+        .output();
+
+    Command::new("cargo")
+        .args(["check"])
+        .current_dir(wt_path)
+        .output()
+        .map(|o| o.status.success())
+        .unwrap_or(false)
+}
+
 /// Check whether the given directory has any uncommitted git changes.
 /// Returns `Err` with a descriptive message if there are any.
 pub(crate) fn check_uncommitted_changes(path: &Path) -> Result<(), String> {
@@ -434,4 +454,87 @@ mod tests {
         // Now the feature branch is ahead of the base branch.
         assert!(worktree_has_committed_work(&wt_path));
     }
+
+    // ── cargo_check_in_worktree tests ────────────────────────────────────────
+
+    /// Bug 645: cargo_check_in_worktree resets dirty files before checking.
+    #[test]
+    fn cargo_check_in_worktree_resets_dirty_files() {
+        use std::fs;
+        let tmp = tempfile::tempdir().unwrap();
+        let project_root = tmp.path().join("project");
+        fs::create_dir_all(&project_root).unwrap();
+        init_git_repo(&project_root);
+
+        // Create a minimal Cargo project so cargo check works.
+        fs::write(
+            project_root.join("Cargo.toml"),
+            "[package]\nname = \"test_proj\"\nversion = \"0.1.0\"\nedition = \"2021\"\n",
+        )
+        .unwrap();
+        fs::create_dir_all(project_root.join("src")).unwrap();
+        fs::write(project_root.join("src/lib.rs"), "// empty lib\n").unwrap();
+        Command::new("git")
+            .args(["add", "."])
+            .current_dir(&project_root)
+            .output()
+            .unwrap();
+        Command::new("git")
+            .args([
+                "-c",
+                "user.email=test@test.com",
+                "-c",
+                "user.name=Test",
+                "commit",
+                "-m",
+                "add cargo project",
+            ])
+            .current_dir(&project_root)
+            .output()
+            .unwrap();
+
+        // Create a worktree on a feature branch.
+        let wt_path = tmp.path().join("wt");
+        Command::new("git")
+            .args([
+                "worktree",
+                "add",
+                &wt_path.to_string_lossy(),
+                "-b",
+                "feature/story-645_test",
+            ])
+            .current_dir(&project_root)
+            .output()
+            .unwrap();
+
+        // Commit valid code.
+        fs::write(wt_path.join("src/lib.rs"), "pub fn hello() {}\n").unwrap();
+        Command::new("git")
+            .args(["add", "."])
+            .current_dir(&wt_path)
+            .output()
+            .unwrap();
+        Command::new("git")
+            .args([
+                "-c",
+                "user.email=test@test.com",
+                "-c",
+                "user.name=Test",
+                "commit",
+                "-m",
+                "add hello fn",
+            ])
+            .current_dir(&wt_path)
+            .output()
+            .unwrap();
+
+        // Now simulate a crash leaving dirty files (broken syntax).
+        fs::write(wt_path.join("src/lib.rs"), "THIS IS BROKEN SYNTAX!!!\n").unwrap();
+
+        // cargo_check_in_worktree should reset dirty files and check committed code.
+        assert!(
+            cargo_check_in_worktree(&wt_path),
+            "cargo check should pass on committed code after resetting dirty files"
+        );
+    }
 }
diff --git a/server/src/agents/pool/pipeline/advance.rs b/server/src/agents/pool/pipeline/advance.rs
index 1103229b..2a976f9f 100644
--- a/server/src/agents/pool/pipeline/advance.rs
+++ b/server/src/agents/pool/pipeline/advance.rs
@@ -115,8 +115,78 @@ impl AgentPool {
                         }
                     }
                 } else {
+                    // Bug 645: Before retry/block, check if the agent left committed
+                    // work that compiles.  An agent may crash mid-output (e.g. Claude
+                    // Code CLI PTY write assertion) after having already committed valid
+                    // code.  When committed work survives and `cargo check` passes,
+                    // advance to QA instead of wasting retries.
+                    let work_survived = worktree_path.as_ref().is_some_and(|wt_path| {
+                        crate::agents::gates::worktree_has_committed_work(wt_path)
+                            && crate::agents::gates::cargo_check_in_worktree(wt_path)
+                    });
+                    if work_survived {
+                        slog!(
+                            "[pipeline] Coder '{agent_name}' failed gates for '{story_id}' but \
+                             committed work survives and compiles. Advancing to QA instead of \
+                             retrying (bug 645)."
+                        );
+                        let qa_mode = {
+                            let item_type = crate::agents::lifecycle::item_type_from_id(story_id);
+                            if item_type == "spike" {
+                                crate::io::story_metadata::QaMode::Human
+                            } else {
+                                let default_qa = config.default_qa_mode();
+                                resolve_qa_mode_from_store(&project_root, story_id, default_qa)
+                            }
+                        };
+                        match qa_mode {
+                            crate::io::story_metadata::QaMode::Server => {
+                                if let Err(e) = crate::agents::lifecycle::move_story_to_merge(
+                                    &project_root,
+                                    story_id,
+                                ) {
+                                    slog_error!(
+                                        "[pipeline] Failed to move '{story_id}' to 4_merge/: {e}"
+                                    );
+                                } else {
+                                    self.start_mergemaster_or_block(&project_root, story_id)
+                                        .await;
+                                }
+                            }
+                            crate::io::story_metadata::QaMode::Agent => {
+                                if let Err(e) = crate::agents::lifecycle::move_story_to_qa(
+                                    &project_root,
+                                    story_id,
+                                ) {
+                                    slog_error!(
+                                        "[pipeline] Failed to move '{story_id}' to 3_qa/: {e}"
+                                    );
+                                } else if let Err(e) = self
+                                    .start_agent(&project_root, story_id, Some("qa"), None, None)
+                                    .await
+                                {
+                                    slog_error!(
+                                        "[pipeline] Failed to start qa for '{story_id}': {e}"
+                                    );
+                                }
+                            }
+                            crate::io::story_metadata::QaMode::Human => {
+                                if let Err(e) = crate::agents::lifecycle::move_story_to_qa(
+                                    &project_root,
+                                    story_id,
+                                ) {
+                                    slog_error!(
+                                        "[pipeline] Failed to move '{story_id}' to 3_qa/: {e}"
+                                    );
+                                } else {
+                                    write_review_hold_to_store(story_id);
+                                }
+                            }
+                        }
+                    } else
                     // Increment retry count and check if blocked.
-                    if let Some(reason) = should_block_story(story_id, config.max_retries, "coder")
+                    if let Some(reason) =
+                        should_block_story(story_id, config.max_retries, "coder")
                     {
                         // Story has exceeded retry limit — do not restart.
                         let _ = self.watcher_tx.send(WatcherEvent::StoryBlocked {
@@ -1062,4 +1132,218 @@ stage = "qa"
             );
         }
     }
+
+    // ── bug 645: work-survived check advances to QA instead of blocking ──
+
+    /// Integration test: when a coder agent fails gates but committed work
+    /// survives and compiles, the story advances to QA (not retry/block).
+    /// Simulates an agent that commits work and then dies mid-output.
+    #[tokio::test]
+    async fn work_survived_advances_to_qa_instead_of_blocking() {
+        use std::fs;
+        use std::process::Command;
+
+        let tmp = tempfile::tempdir().unwrap();
+        let root = tmp.path();
+
+        // Init a git repo with a minimal Cargo project.
+        Command::new("git")
+            .args(["init"])
+            .current_dir(root)
+            .output()
+            .unwrap();
+        Command::new("git")
+            .args(["config", "user.email", "test@test.com"])
+            .current_dir(root)
+            .output()
+            .unwrap();
+        Command::new("git")
+            .args(["config", "user.name", "Test"])
+            .current_dir(root)
+            .output()
+            .unwrap();
+        fs::write(
+            root.join("Cargo.toml"),
+            "[package]\nname = \"test_proj\"\nversion = \"0.1.0\"\nedition = \"2021\"\n",
+        )
+        .unwrap();
+        fs::create_dir_all(root.join("src")).unwrap();
+        fs::write(root.join("src/lib.rs"), "// empty\n").unwrap();
+        Command::new("git")
+            .args(["add", "."])
+            .current_dir(root)
+            .output()
+            .unwrap();
+        Command::new("git")
+            .args(["commit", "-m", "init"])
+            .current_dir(root)
+            .output()
+            .unwrap();
+
+        // Create a worktree on a feature branch.
+        let wt_path = tmp.path().join("wt");
+        Command::new("git")
+            .args([
+                "worktree",
+                "add",
+                &wt_path.to_string_lossy(),
+                "-b",
+                "feature/story-9945_story_survived",
+            ])
+            .current_dir(root)
+            .output()
+            .unwrap();
+
+        // Commit valid code on the feature branch.
+        fs::write(wt_path.join("src/lib.rs"), "pub fn survived() {}\n").unwrap();
+        Command::new("git")
+            .args(["add", "."])
+            .current_dir(&wt_path)
+            .output()
+            .unwrap();
+        Command::new("git")
+            .args(["commit", "-m", "add survived fn"])
+            .current_dir(&wt_path)
+            .output()
+            .unwrap();
+
+        // Set up the story in the content store.
+        crate::db::ensure_content_store();
+        crate::db::write_content("9945_story_survived", "---\nname: Survived Test\n---\n");
+        crate::db::write_item_with_content(
+            "9945_story_survived",
+            "2_current",
+            "---\nname: Survived Test\n---\n",
+        );
+
+        let pool = AgentPool::new_test(3001);
+
+        // Simulate coder failing gates (e.g. agent crashed, dirty worktree).
+        pool.run_pipeline_advance(
+            "9945_story_survived",
+            "coder-1",
+            CompletionReport {
+                summary: "Agent crashed".to_string(),
+                gates_passed: false,
+                gate_output: "Worktree has uncommitted changes".to_string(),
+            },
+            Some(root.to_path_buf()),
+            Some(wt_path),
+            false,
+            None,
+        )
+        .await;
+
+        // Story should have advanced — content store should reflect the move.
+        // The work-survived check should have moved it to QA (or merge for
+        // server qa mode), NOT incremented retry_count.
+        let content = crate::db::read_content("9945_story_survived")
+            .expect("story should exist in content store");
+        assert!(
+            !content.contains("blocked"),
+            "story should NOT be blocked when committed work survives: {content}"
+        );
+        assert!(
+            !content.contains("retry_count"),
+            "story should NOT have retry_count when work survived: {content}"
+        );
+    }
+
+    /// Backwards-compat: agents that die WITHOUT committed work still get
+    /// the existing retry/block treatment.
+    #[tokio::test]
+    async fn no_committed_work_still_retries_and_blocks() {
+        use std::fs;
+        use std::process::Command;
+
+        let tmp = tempfile::tempdir().unwrap();
+        let root = tmp.path();
+
+        // Init a git repo (no Cargo project needed — cargo check will fail).
+        Command::new("git")
+            .args(["init"])
+            .current_dir(root)
+            .output()
+            .unwrap();
+        Command::new("git")
+            .args(["config", "user.email", "test@test.com"])
+            .current_dir(root)
+            .output()
+            .unwrap();
+        Command::new("git")
+            .args(["config", "user.name", "Test"])
+            .current_dir(root)
+            .output()
+            .unwrap();
+        Command::new("git")
+            .args(["commit", "--allow-empty", "-m", "init"])
+            .current_dir(root)
+            .output()
+            .unwrap();
+
+        // Create a worktree with NO commits on the feature branch.
+        let wt_path = tmp.path().join("wt");
+        Command::new("git")
+            .args([
+                "worktree",
+                "add",
+                &wt_path.to_string_lossy(),
+                "-b",
+                "feature/story-9946_story_nowork",
+            ])
+            .current_dir(root)
+            .output()
+            .unwrap();
+
+        // Set up the story with max_retries=1 so it blocks immediately.
+        crate::db::ensure_content_store();
+        crate::db::write_content("9946_story_nowork", "---\nname: No Work Test\n---\n");
+        crate::db::write_item_with_content(
+            "9946_story_nowork",
+            "2_current",
+            "---\nname: No Work Test\n---\n",
+        );
+
+        // Write a project.toml with max_retries = 1.
+        fs::create_dir_all(root.join(".huskies")).unwrap();
+        fs::write(
+            root.join(".huskies/project.toml"),
+            "max_retries = 1\n\n[[agent]]\nname = \"coder-1\"\nstage = \"coder\"\n",
+        )
+        .unwrap();
+
+        let pool = AgentPool::new_test(3001);
+        let mut rx = pool.watcher_tx.subscribe();
+
+        // Simulate coder failing gates with NO committed work on the worktree.
+        pool.run_pipeline_advance(
+            "9946_story_nowork",
+            "coder-1",
+            CompletionReport {
+                summary: "Agent crashed".to_string(),
+                gates_passed: false,
+                gate_output: "Tests failed".to_string(),
+            },
+            Some(root.to_path_buf()),
+            Some(wt_path),
+            false,
+            None,
+        )
+        .await;
+
+        // With no committed work and max_retries=1, the story should be blocked.
+        let mut got_blocked = false;
+        while let Ok(evt) = rx.try_recv() {
+            if let WatcherEvent::StoryBlocked { story_id, .. } = &evt
+                && story_id == "9946_story_nowork"
+            {
+                got_blocked = true;
+                break;
+            }
+        }
+        assert!(
+            got_blocked,
+            "Story with no committed work should be blocked after exceeding retry limit"
+        );
+    }
 }
diff --git a/server/src/agents/pool/pipeline/completion.rs b/server/src/agents/pool/pipeline/completion.rs
index 2beedcd0..9d53a7f9 100644
--- a/server/src/agents/pool/pipeline/completion.rs
+++ b/server/src/agents/pool/pipeline/completion.rs
@@ -232,7 +232,31 @@ pub(in crate::agents::pool) async fn run_server_owned_completion(
     let (gates_passed, gate_output) = if let Some(wt_path) = worktree_path {
         let path = wt_path;
         match tokio::task::spawn_blocking(move || {
-            crate::agents::gates::check_uncommitted_changes(&path)?;
+            // If the worktree is dirty, check whether committed work survived.
+            // An agent crash (e.g. Claude Code CLI's `output.write(&bytes).is_ok()`
+            // assertion — bug 645) can leave uncommitted files behind even though
+            // the agent already committed valid work.  In that case, clean up the
+            // dirty files and proceed with gates on the committed code.
+            if let Err(dirty_msg) = crate::agents::gates::check_uncommitted_changes(&path) {
+                if crate::agents::gates::worktree_has_committed_work(&path) {
+                    crate::slog!(
+                        "[agents] Worktree dirty but committed work exists — \
+                         resetting uncommitted changes and proceeding with gates. \
+                         Dirty state: {dirty_msg}"
+                    );
+                    // Reset dirty files so gates run against committed code only.
+                    let _ = std::process::Command::new("git")
+                        .args(["checkout", "."])
+                        .current_dir(&path)
+                        .output();
+                    let _ = std::process::Command::new("git")
+                        .args(["clean", "-fd"])
+                        .current_dir(&path)
+                        .output();
+                } else {
+                    return Ok((false, dirty_msg));
+                }
+            }
             // AC5: Fail early if the coder finished with no commits on the feature branch.
             // This prevents empty-diff stories from advancing through QA to merge.
             if !crate::agents::gates::worktree_has_committed_work(&path) {
@@ -642,4 +666,82 @@ mod tests {
             "Agent must remain in pool — run_server_owned_completion is a no-op for mergemaster"
         );
     }
+
+    /// Bug 645: when an agent crashes leaving dirty files but committed work,
+    /// server-owned completion should clean up the dirty files and run gates
+    /// on the committed code instead of failing immediately.
+    #[tokio::test]
+    async fn server_owned_completion_cleans_dirty_worktree_with_committed_work() {
+        use std::fs;
+        use tempfile::tempdir;
+
+        let tmp = tempdir().unwrap();
+        let project_root = tmp.path().join("project");
+        fs::create_dir_all(&project_root).unwrap();
+        init_git_repo(&project_root);
+
+        // Create a worktree on a feature branch with committed code.
+        let wt_path = tmp.path().join("wt");
+        Command::new("git")
+            .args([
+                "worktree",
+                "add",
+                &wt_path.to_string_lossy(),
+                "-b",
+                "feature/story-645_test",
+            ])
+            .current_dir(&project_root)
+            .output()
+            .unwrap();
+
+        // Commit a valid file.
+        fs::write(wt_path.join("work.txt"), "done").unwrap();
+        Command::new("git")
+            .args(["add", "."])
+            .current_dir(&wt_path)
+            .output()
+            .unwrap();
+        Command::new("git")
+            .args(["commit", "-m", "coder: add work"])
+            .current_dir(&wt_path)
+            .output()
+            .unwrap();
+
+        // Now simulate crash leaving dirty files.
+        fs::write(wt_path.join("dirty.txt"), "crash residue").unwrap();
+
+        let pool = AgentPool::new_test(3001);
+        pool.inject_test_agent_with_path(
+            "645_test",
+            "coder-1",
+            AgentStatus::Running,
+            wt_path.clone(),
+        );
+
+        let mut rx = pool.subscribe("645_test", "coder-1").unwrap();
+
+        run_server_owned_completion(
+            &pool.agents,
+            pool.port,
+            "645_test",
+            "coder-1",
+            Some("sess-645".to_string()),
+            pool.watcher_tx.clone(),
+        )
+        .await;
+
+        // The dirty file should have been cleaned up.
+        assert!(
+            !wt_path.join("dirty.txt").exists(),
+            "dirty file should be cleaned up after server-owned completion"
+        );
+
+        // A Done event should have been emitted (completion ran, didn't fail
+        // on dirty worktree).
+        let event = rx.try_recv().expect("should emit Done event");
+        assert!(
+            matches!(event, AgentEvent::Done { .. }),
+            "expected Done event, got: {event:?}"
+        );
+    }
 }
diff --git a/server/src/agents/pty.rs b/server/src/agents/pty.rs
index 1107f402..322df415 100644
--- a/server/src/agents/pty.rs
+++ b/server/src/agents/pty.rs
@@ -36,6 +36,22 @@ impl Drop for ChildKillerGuard {
 }
 
 /// Spawn claude agent in a PTY and stream events through the broadcast channel.
+///
+/// ## Bug 645: `output.write(&bytes).is_ok()` assertion in Claude Code CLI
+///
+/// The Claude Code CLI can panic with an `output.write(&bytes).is_ok()` assertion
+/// when writing to its stdout (the PTY slave end).  This occurs inside the child
+/// process — not in this server code — when the PTY pipe breaks or fills.  The
+/// `output` in the assertion is the CLI's stdout writer, and the write fails when
+/// the PTY master side is closed or the kernel pipe buffer is exhausted.
+///
+/// When this happens, the child process dies, the PTY reader thread in this
+/// function receives EOF, and `run_agent_pty_blocking` returns `Ok(PtyResult)`.
+/// The server then runs completion gates via `run_server_owned_completion`.
+///
+/// If the agent committed valid work before crashing, the "work survived" check
+/// in `pipeline::advance` detects the committed code and advances the story to
+/// QA instead of entering the retry/block path.
 #[allow(clippy::too_many_arguments)]
 pub(in crate::agents) async fn run_agent_pty_streaming(
     story_id: &str,