Suppress errors for requested session stops

server/src/session/claude.rs

@@ -802,11 +802,13 @@ async fn follow(
             process::Liveness::Dead if complete > 0 => {}
             process::Liveness::Dead => {
                 queue.lock().unwrap().close(&sink, "the session ended");
-                let detail = stderr_tail(&stderr_path);
-                if !detail.is_empty() {
-                    let _ = sink.send(Event::Error {
-                        message: format!("{label} exited:\n{detail}"),
-                    });
+                if !process::stopping(&session_dir) {
+                    let detail = stderr_tail(&stderr_path);
+                    if !detail.is_empty() {
+                        let _ = sink.send(Event::Error {
+                            message: format!("{label} exited:\n{detail}"),
+                        });
+                    }
                 }
                 let _ = sink.send(Event::Status {
                     state: SessionStatus::Exited,

server/src/session/codex.rs

@@ -623,6 +623,7 @@ async fn follow(inner: Arc<Inner>, mut record: process::Record, mut offset: u64)
             process::Liveness::Alive | process::Liveness::Unknown => {}
             process::Liveness::Dead if complete > 0 => {}
             process::Liveness::Dead => {
+                let stopped = process::stopping(&inner.session_dir);
                 process::clear(&inner.session_dir);
                 let dropped = {
                     let mut state = inner.state.lock().unwrap();
@@ -639,11 +640,13 @@ async fn follow(inner: Arc<Inner>, mut record: process::Record, mut offset: u64)
                 for id in dropped {
                     let _ = inner.sink.send(Event::MessageDropped { id });
                 }
-                let detail = stderr_tail(&stderr);
-                if !detail.is_empty() {
-                    let _ = inner.sink.send(Event::Error {
-                        message: format!("Codex exited:\n{detail}"),
-                    });
+                if !stopped {
+                    let detail = stderr_tail(&stderr);
+                    if !detail.is_empty() {
+                        let _ = inner.sink.send(Event::Error {
+                            message: format!("Codex exited:\n{detail}"),
+                        });
+                    }
                 }
                 let _ = inner.sink.send(Event::Status {
                     state: SessionStatus::Exited,

server/src/session/llama.rs

@@ -312,9 +312,11 @@ fn watch(session_dir: PathBuf, sink: EventSink) {
                 // deliberately, and whoever did that has already said so.
                 None => return,
                 Some((_, process::Liveness::Dead)) => {
-                    let _ = sink.send(Event::Error {
-                        message: "llama-server exited".to_string(),
-                    });
+                    if !process::stopping(&session_dir) {
+                        let _ = sink.send(Event::Error {
+                            message: "llama-server exited".to_string(),
+                        });
+                    }
                     let _ = sink.send(Event::Status {
                         state: SessionStatus::Exited,
                     });

server/src/session/mod.rs

@@ -1652,6 +1652,7 @@ impl SessionManager {
                 cwd.display(),
                 record.pid
             );
+            process::mark_stopping(&dir)?;
             process::stop(&record, process::STOP_GRACE);
         }
         Ok(())
@@ -1714,6 +1715,7 @@ impl SessionManager {
                 effort.unwrap_or("default"),
                 record.pid
             );
+            process::mark_stopping(&dir)?;
             process::stop(&record, process::STOP_GRACE);
         }
         Ok(())
@@ -1761,6 +1763,7 @@ impl SessionManager {
             }
         };
         tracing::info!("stopping session {id} (pid {})", record.pid);
+        process::mark_stopping(&self.data_dir.join(id))?;
         process::stop(&record, process::STOP_GRACE);
         Ok(())
     }
@@ -4329,6 +4332,52 @@ mod tests {
         ));
     }
 
+    /// Stderr is a log of the process's whole lifetime, not necessarily why it
+    /// ended. A requested Stop used to paste its oldest surviving diagnostics
+    /// into the transcript as a fresh failure -- complete with terminal escape
+    /// codes -- even though the process ended only because the person asked.
+    #[tokio::test]
+    async fn stopping_a_session_does_not_report_old_stderr_as_a_failure() {
+        let dir = tempfile::tempdir().expect("tempdir");
+        let config_path = dir.path().join("config.ron");
+        let data_dir = dir.path().join("sessions");
+        let provider = seed_stand_in_cli(&config_path, dir.path());
+        let manager = SessionManager::new(config_path, data_dir.clone(), data_dir.join("models"))
+            .expect("manager");
+        let info = manager
+            .spawn_session(stand_in_spec(&provider))
+            .expect("spawn");
+        let mut rx = manager.session(&info.id).expect("live").subscribe();
+        let session_dir = data_dir.join(&info.id);
+
+        std::fs::write(
+            session_dir.join("stderr.log"),
+            "\u{1b}[31mERROR\u{1b}[0m an old tool diagnostic\n",
+        )
+        .expect("seed stderr");
+        manager.stop_session(&info.id).expect("stop");
+
+        let seen = collect_until(&mut rx, |event| {
+            matches!(
+                event,
+                Event::Status {
+                    state: SessionStatus::Exited
+                }
+            )
+        })
+        .await;
+        assert!(
+            !seen
+                .iter()
+                .any(|entry| matches!(entry.event, Event::Error { .. })),
+            "a requested stop was presented as a failure: {seen:?}"
+        );
+        assert!(
+            !process::stopping(&session_dir),
+            "the completed stop left its marker behind"
+        );
+    }
+
     /// A message and a command both mean "now", so neither answers that the
     /// session's process has gone -- they start one and go to it.
     ///

server/src/session/process.rs

@@ -30,6 +30,7 @@ use anyhow::{Context, Result};
 use serde::{Deserialize, Serialize};
 
 const RECORD_FILE: &str = "process.json";
+const STOP_REQUEST_FILE: &str = "stop-requested";
 
 /// A process this server started and expects to outlive it.
 #[derive(Debug, Clone, PartialEq, Serialize, Deserialize)]
@@ -101,6 +102,28 @@ fn path(session_dir: &Path) -> PathBuf {
     session_dir.join(RECORD_FILE)
 }
 
+fn stop_request_path(session_dir: &Path) -> PathBuf {
+    session_dir.join(STOP_REQUEST_FILE)
+}
+
+/// Marks the process as one the server deliberately asked to end, so its watcher reports an exit
+/// without presenting ordinary stderr from the process's lifetime as the cause.
+pub fn mark_stopping(session_dir: &Path) -> Result<()> {
+    std::fs::OpenOptions::new()
+        .create(true)
+        .write(true)
+        .truncate(true)
+        .mode(0o600)
+        .open(stop_request_path(session_dir))
+        .with_context(|| format!("marking {} as stopping", session_dir.display()))?;
+    Ok(())
+}
+
+/// Whether this process's exit was deliberately requested.
+pub fn stopping(session_dir: &Path) -> bool {
+    stop_request_path(session_dir).is_file()
+}
+
 /// The recorded process and whether it is still there, or `None` when nothing
 /// usable is recorded. A record that does not parse reads as no record: the
 /// only way to get one is a crash partway through writing it, and the safe
@@ -179,11 +202,12 @@ pub fn size_of(path: &Path) -> u64 {
 /// Forgets the recorded process -- for one confirmed dead, or a session
 /// being deleted. The path out for [`write`].
 pub fn clear(session_dir: &Path) {
-    let path = path(session_dir);
-    if let Err(err) = std::fs::remove_file(&path)
-        && err.kind() != std::io::ErrorKind::NotFound
-    {
-        tracing::warn!("couldn't remove {}: {err}", path.display());
+    for path in [path(session_dir), stop_request_path(session_dir)] {
+        if let Err(err) = std::fs::remove_file(&path)
+            && err.kind() != std::io::ErrorKind::NotFound
+        {
+            tracing::warn!("couldn't remove {}: {err}", path.display());
+        }
     }
 }
 
@@ -405,8 +429,11 @@ mod tests {
         write(dir.path(), &record);
         assert_eq!(live(dir.path()), Some(record));
 
+        mark_stopping(dir.path()).expect("mark stopping");
+        assert!(stopping(dir.path()));
         clear(dir.path());
         assert_eq!(live(dir.path()), None);
+        assert!(!stopping(dir.path()));
     }
 
     #[test]