fix(aws): the file viewer's change poll no longer counts as workspace activity

Its 2 s sha256sum poll now carries X-Triple-C-Background, so an open viewer does
not keep an idle AWS workspace up. Opening and saving a file stay foreground;
Docker is unchanged.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

app/src-tauri/src/file_viewer/poll.rs

@@ -51,8 +51,10 @@ pub async fn poll_file(
         "poll".to_string(),
         container_path.to_string(),
     ];
+    // A background poll: an open viewer must not keep an idle AWS workspace
+    // up. Opening and saving a file are the user's own actions and count.
     let (stdout, stderr, code) = container
-        .exec_oneshot_streams_as("claude", cmd, Vec::new())
+        .exec_oneshot_streams_background("claude", cmd)
         .await?;
     if code != 0 && code != 4 {
         return Err(format!(

app/src-tauri/src/host/agent.rs

@@ -400,6 +400,17 @@ pub async fn exec_oneshot_streams_as(
     Ok((out.stdout(), out.stderr(), out.exit_code))
 }
 
+/// [`exec_oneshot_streams_as`] marked as a background poll (the file
+/// viewer's change check), so it never keeps an idle workspace up.
+pub async fn exec_oneshot_streams_background(
+    ep: &AgentEndpoint,
+    user: &str,
+    cmd: Vec<String>,
+) -> Result<(String, String, i64), String> {
+    let out = exec_oneshot_raw_marked(ep, user, cmd, Vec::new(), MAX_ONESHOT_OUTPUT, true).await?;
+    Ok((out.stdout(), out.stderr(), out.exit_code))
+}
+
 // ── detached execs, status, resize ───────────────────────────────────────────
 
 #[derive(Deserialize)]

app/src-tauri/src/host/agent/tests.rs

@@ -323,6 +323,22 @@ async fn only_a_background_poll_carries_the_background_marker() {
     assert_eq!(seen.exec_bodies[0], seen.exec_bodies[1], "the request is otherwise the same");
 }
 
+#[tokio::test]
+async fn the_file_viewers_poll_is_a_background_request_and_its_open_and_save_are_not() {
+    let (ep, fake) = fake_agent().await;
+    let t = target(&ep);
+    // The 2 s change check, as the viewer runs it.
+    let _ = crate::file_viewer::poll::poll_file(&t, "/workspace/x").await;
+    t.exec_oneshot_streams_background("claude", cmd("sh")).await.unwrap();
+    // What opening or saving goes through: user actions, which count.
+    t.exec_oneshot_streams_as("claude", cmd("sh"), Vec::new()).await.unwrap();
+    let seen = fake.seen.lock().unwrap();
+    assert_eq!(seen.exec_background, [Some("1".to_string()), Some("1".to_string()), None]);
+    let src = |s: &str| s.contains("exec_oneshot_streams_as(");
+    assert!(!src(include_str!("../../file_viewer/poll.rs")), "the poll stays a background request");
+    assert!(src(include_str!("../../file_viewer/resolve.rs")) && src(include_str!("../../file_viewer/write.rs")));
+}
+
 // ── one-shot execs ───────────────────────────────────────────────────────────
 
 #[tokio::test]

app/src-tauri/src/host/mod.rs

@@ -302,6 +302,22 @@ impl ContainerTarget {
         }
     }
 
+    /// [`Self::exec_oneshot_streams_as`] for a background poll (the file
+    /// viewer's change check): on the agent it carries the background marker,
+    /// so it never counts as activity for idle stop. The same call on Docker.
+    pub async fn exec_oneshot_streams_background(
+        &self,
+        user: &str,
+        cmd: Vec<String>,
+    ) -> Result<(String, String, i64), String> {
+        match self {
+            ContainerTarget::Docker { container_id } => {
+                docker::exec::exec_oneshot_streams_as(container_id, user, cmd, Vec::new()).await
+            }
+            ContainerTarget::Agent(ep) => agent::exec_oneshot_streams_background(ep, user, cmd).await,
+        }
+    }
+
     /// Start a command and return without waiting or reading its output.
     /// Returns the exec id.
     pub async fn exec_detached(&self, spec: ExecSpec) -> Result<String, String> {