diff --git a/crates/tui/src/tui/history.rs b/crates/tui/src/tui/history.rs
index 9ca7fb54..252e4288 100644
--- a/crates/tui/src/tui/history.rs
+++ b/crates/tui/src/tui/history.rs
@@ -957,7 +957,7 @@ impl ExecCell {
                 ));
             } else if self.status == ToolStatus::Running && self.source == ExecSource::Assistant {
                 lines.extend(wrap_plain_line(
-                    "  Ctrl+B opens shell controls.",
+                    "  Ctrl+B backgrounds this command.",
                     Style::default().fg(palette::TEXT_MUTED),
                     width,
                 ));
@@ -5075,7 +5075,7 @@ mod tests {
 
         assert!(text.contains("running line 1"));
         assert!(text.contains("running line 2"));
-        assert!(!text.contains("Ctrl+B opens shell controls"));
+        assert!(!text.contains("Ctrl+B backgrounds this command"));
     }
 
     #[test]
diff --git a/crates/tui/src/tui/ui.rs b/crates/tui/src/tui/ui.rs
index be17a2d9..ba25afb9 100644
--- a/crates/tui/src/tui/ui.rs
+++ b/crates/tui/src/tui/ui.rs
@@ -8771,10 +8771,30 @@ fn render_toast_stack_overlay(
 }
 
 pub(crate) fn request_foreground_shell_background(app: &mut App) {
-    if !app.is_loading || !active_foreground_shell_running(app) {
+    if !app.is_loading {
         app.status_message = Some("No foreground shell command to background".to_string());
         return;
     }
+    if !active_foreground_shell_running(app) {
+        // #3032 AC3: name the reason backgrounding is unavailable —
+        // interactive execs and non-shell blocking tools are visibly running
+        // but cannot be detached, and a generic shrug reads like a bug.
+        let reason = if terminal_pause_has_live_owner(app) {
+            "the running command is interactive"
+        } else if app
+            .active_cell
+            .as_ref()
+            .is_some_and(|active| !active.is_empty())
+        {
+            "the running tool is not a foreground shell command"
+        } else {
+            "no foreground shell command is running"
+        };
+        app.status_message = Some(format!(
+            "Cannot background: {reason}. Press Ctrl+C to cancel the turn, or wait for completion."
+        ));
+        return;
+    }
 
     let Some(shell_manager) = app.runtime_services.shell_manager.clone() else {
         app.status_message = Some("Shell manager is not attached".to_string());
diff --git a/docs/KEYBINDINGS.md b/docs/KEYBINDINGS.md
index 6782e4ee..e3710bc7 100644
--- a/docs/KEYBINDINGS.md
+++ b/docs/KEYBINDINGS.md
@@ -11,6 +11,7 @@ Bindings are not (yet) user-configurable — tracked for a future release (#436,
 | `F1` or `Ctrl-/`     | Toggle the help overlay                                       |
 | `Ctrl-K`             | Open the command palette (slash-command finder)                |
 | `Ctrl-C`             | Cancel current turn / dismiss modal / arm-then-confirm quit    |
+| `Ctrl-B`             | Background the running foreground shell command (turn continues; the command becomes a `/jobs` background job) |
 | `Ctrl-D`             | Quit (only when the composer is empty)                         |
 | `Tab`                | Cycle TUI mode: Plan → Agent → YOLO → Plan                     |
 | `Shift-Tab`          | Cycle reasoning effort: off → high → max → off                 |
diff --git a/docs/OPERATIONS_RUNBOOK.md b/docs/OPERATIONS_RUNBOOK.md
index d53a8a45..8e98ac8a 100644
--- a/docs/OPERATIONS_RUNBOOK.md
+++ b/docs/OPERATIONS_RUNBOOK.md
@@ -28,7 +28,7 @@ Checks:
 3. Confirm no local sandbox/permission deadlock in tool output
 
 Actions:
-1. If a foreground shell command is running, press `Ctrl+B` and choose whether to background it or cancel the current turn.
+1. If a foreground shell command is running, press `Ctrl+B` to move it to the background (the turn keeps running and the command becomes a background job under `/jobs`); use `Ctrl+C` instead if you want to cancel the turn.
 2. If the command was started in the background, ask the assistant to cancel it with `exec_shell_cancel` and the returned task id.
 3. Use `Esc` or `Ctrl+C` to interrupt the current turn when you want to stop the request itself.
 4. Retry prompt; if still failing, restart TUI.