[Feature]: Send prompts to new threads with Alt+Enter

[AksharP5]

Before submitting

• I searched existing issues and did not find a duplicate.
• I am describing a concrete problem or use case, not just a vague idea.

Area

apps/web

Problem or use case

When I finish drafting a prompt in an existing thread, I sometimes realize it belongs in a separate thread.

T3 Code currently makes me copy the draft, create a new thread, paste it, and send it. This interrupts the keyboard flow and makes it easy to send unrelated work into the current thread by mistake.

Proposed solution

On desktop, Alt+Enter should send the current composer draft to a new thread in the same project.

Plain Enter should continue sending to the current thread, and Shift+Enter should continue inserting a newline.

T3 should start the turn in the new thread, navigate to it, and avoid briefly showing the source thread as working. The new thread should use the same project and checkout defaults as a normally created thread.

The send button tooltip should mention the shortcut so it is discoverable.

Why this matters

Threads are easier to follow when unrelated work stays separate. This replaces a copy, create, paste, and send workflow with one shortcut while preserving the prompt the user has already written.

Smallest useful scope

Support Alt+Enter in the desktop web composer and desktop app.

The first version does not need a setting, mobile gesture, command-palette action, or configurable keybinding. Existing Enter and Shift+Enter behavior should remain unchanged.

Alternatives considered

The current workaround is to copy the draft, create a thread, paste it, and send it.

A separate button or menu action would work, but it adds UI for an action meant to keep the user in the keyboard flow.

The broader keybinding system could expose this as a configurable command later. A fixed composer shortcut keeps the first version smaller.

Risks or tradeoffs

The shortcut must not interfere with Shift+Enter or modified combinations such as Ctrl+Alt+Enter and Meta+Alt+Enter.

If creating or starting the new thread fails, the current thread should remain usable and show a clear error. The source thread should not briefly enter a working state for a turn that belongs to the new thread.

The shortcut is desktop-only because mobile keyboards do not provide the same modifier behavior.

Examples or references

Prior art: Cortex Code provides an Alt action for sending a draft to a new session.

Related but distinct:

• [Feature]: Expose "Implement in new thread" as a keybindable command #1469 requests a keybinding for implementing a completed plan in a new thread.
• [Feature]: Expose more actions as bindable keybinding commands #4641 tracks broader keybinding command coverage.

Demo video will be added below.

Contribution

• I would be open to helping implement this.

[AksharP5]

alt-enter-new-thread-demo-hq-ready.mp4

[henrik092]

I'd find this useful too, especially from an existing conversation: I start writing a prompt, then realize it is a separate task that should have its own thread in the same project. Being able to send that draft to a new thread while keeping my current provider/model settings (including reasoning effort) would save copying, creating a thread, pasting, and checking the settings again.

I'm using nightly. The Ctrl+Enter background-start workflow for a fresh draft is helpful, but it doesn't cover this case in an existing thread.

I saw that #6550 was closed during the backlog cleanup, with concerns about adding another send path and changing branch selection state. Would a small implementation using the existing new-thread flow and normal checkout defaults be welcome, or is the interaction itself outside the intended scope? I don't have a preference for Alt+Enter specifically; a shortcut or action consistent with T3's existing UX would work for me.

Posting here per CONTRIBUTING.md rather than opening another issue or an unsolicited PR. Thanks for considering the use case!