feat(web): mod+alt+enter on an existing thread sends and opens a new thread

apps/web/src/components/ChatView.tsx

@@ -8511,6 +8511,11 @@ export default function ChatView(props: ChatViewProps) {
             setComposerDraftThreadContexts(composerDraftTarget, [...records]),
           resetCursor: (options) => composerRef.current?.resetCursorState(options),
         });
+      } else if (
+        submissionIntent === "background" &&
+        currentRouteThreadKeyRef.current === routeThreadKey
+      ) {
+        handleNewThreadInActiveProject();
       }
       return;
     }
@@ -8743,7 +8748,9 @@ export default function ChatView(props: ChatViewProps) {
     }
     beginLocalDispatch({
       preparingWorktree: multipleModelSelections !== null || Boolean(baseBranchForWorktree),
-      submissionIntent,
+      // Only a draft has a background submission to hide behind its hero.
+      submissionIntent:
+        submissionIntent === "background" && !isLocalDraftThread ? "foreground" : submissionIntent,
     });
     setWorktreeSetupRef(
       multipleModelSelections === null && baseBranchForWorktree
@@ -9316,6 +9323,12 @@ export default function ChatView(props: ChatViewProps) {
               }),
             );
           }
+        } else if (
+          submissionIntent === "background" &&
+          currentRouteThreadKeyRef.current === routeThreadKey
+        ) {
+          // An existing thread keeps running; open a fresh composer like a draft does.
+          handleNewThreadInActiveProject();
         }
       }
     }

apps/web/src/components/settings/KeybindingsSettings.logic.ts

@@ -314,6 +314,7 @@ export function buildKeybindingCommandOptions(
 export function commandLabel(command: KeybindingCommand): string {
   if (command === "composer.sendAlternate") return "Composer: Opposite Queue or Steer Action";
   if (command === "composer.sendBackground") return "Composer: Start in Background";
+  if (command === "composer.sendAndNewThread") return "Composer: Send and Start New Thread";
   if (command === "thread.steerQueuedMessage") return "Queue: Send First Queued Message as Steer";
   if (command === "thread.editQueuedMessage") return "Queue: Edit Last Queued Message";
   if (command === "thread.copyReference") return "Pull Request: Copy Link or Thread ID";

apps/web/src/composer-logic.test.ts

@@ -124,6 +124,14 @@ describe("composerSubmissionIntentForKey", () => {
           event: { ...modEnter, altKey: true },
         }),
       ).toBe("background");
+      expect(
+        composerSubmissionIntentForKey({
+          ...input,
+          platform,
+          sendShortcut,
+          event: { ...modEnter, altKey: true },
+        }),
+      ).toBe("background");
       expect(
         composerSubmissionIntentForKey({
           ...input,

apps/web/src/composer-logic.ts

@@ -59,6 +59,7 @@ export function composerSubmissionIntentForKey(input: {
   });
   if (command === "composer.sendAlternate" && input.isRunning) return "alternate";
   if (command === "composer.sendBackground" && input.isDraftThread) return "background";
+  if (command === "composer.sendAndNewThread" && !input.isDraftThread) return "background";
   if (command !== null || event.key !== "Enter" || event.shiftKey || event.altKey) return null;
   if (
     composerRequiresModifier(input.sendShortcut, input.prompt ?? "") &&

docs/user/keybindings.md

@@ -11,11 +11,12 @@ inserts a new line. This applies to the web and desktop composer at desktop widt
 
 **Follow-up behavior** chooses Queue or Steer while the agent runs. Use
 `mod+Enter` to do the opposite for one message, even when the send shortcut
-requires a modifier. In a new thread, `mod+Alt+Enter` starts the thread in the
-background and opens a fresh composer. Change either shortcut in
-**Settings → Keybindings** under **Composer: Opposite Queue or Steer Action** or
-**Composer: Start in Background**. These bindings take priority over the send
-shortcut. Click the send button to use the configured follow-up behavior.
+requires a modifier. `mod+Alt+Enter` sends, keeps that thread running in the
+background, and opens a fresh new-thread composer. Change these
+shortcuts in **Settings → Keybindings** under **Composer: Opposite Queue or
+Steer Action**, **Composer: Start in Background**, or **Composer: Send and Start
+New Thread**. These bindings take priority over the send shortcut. Click the
+send button to use the configured follow-up behavior.
 
 When an active turn has queued messages, `mod+Shift+Enter` sends the first as a
 steer. Change it under **Queue: Send First Queued Message as Steer** in Keybindings.

packages/contracts/src/keybindings.ts

@@ -87,6 +87,7 @@ export const STATIC_KEYBINDING_COMMANDS = [
   "composer.stash",
   "composer.sendAlternate",
   "composer.sendBackground",
+  "composer.sendAndNewThread",
   "composer.host",
   "composer.effort",
   "composer.mode",

packages/shared/src/keybindings.ts

@@ -53,6 +53,11 @@ export const DEFAULT_KEYBINDINGS: ReadonlyArray<KeybindingRule> = [
     command: "composer.sendBackground",
     when: "composerFocus && draftThreadRoute",
   },
+  {
+    key: "mod+alt+enter",
+    command: "composer.sendAndNewThread",
+    when: "composerFocus && !draftThreadRoute",
+  },
   { key: "mod+n", command: "chat.new", when: "!terminalFocus" },
   { key: "mod+shift+o", command: "chat.new", when: "!terminalFocus" },
   { key: "mod+shift+n", command: "chat.newLocal", when: "!terminalFocus" },