[Feature]: Allow "Open" to launch a custom/user-defined application

[seniru-dilmith]

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/desktop

Problem or use case
The "Open" dropdown currently only lists a fixed set of applications (VS Code, CLion, PyCharm, RustRover, Files). If a user's preferred editor or tool isn't one of these, there's no way to launch the project with it they have to fall back to manually locating and opening the folder outside the app.

This is limiting for anyone using editors or tools outside the pre-baked list, e.g. Zed, Sublime Text, Neovim (via a terminal wrapper), Android Studio, Cursor, or internal/company-specific tooling.

Proposed solution
Add a "Custom application..." entry at the bottom of the "Open" dropdown that lets the user specify the path/command of an arbitrary application to open the project with.

Behavior:

• Selecting it opens a native file/app picker so the user can point to an executable.
• Once chosen, the entry is saved so it appears in the "Open" list going forward, like a first-class entry alongside the built-in apps.
• The app should be launched with the project's root path as an argument, consistent with how the existing entries behave.

Why this matters
Not everyone uses the same fixed list of IDEs. Supporting a custom application removes a hard limitation for users on less common editors and avoids forcing a detour through the file system every time.

Smallest useful scope

• Add a "Custom application" item to the Open dropdown.
• Prompt for an executable path via a native picker.
• Launch it with the project path as an argument.
• Persist the choice so it's remembered as a normal entry for next time.

No new open/no-existing-defaults behavior needs to change. This only adds an additional option.

Alternatives considered

• Manually opening the project folder and launching the app separately: works today but breaks the one-click workflow the Open menu provides for every other app.
• Requesting each individual missing editor be added as a hardcoded option: doesn't scale and still leaves out anyone on a less common tool.

Risks or tradeoffs
Needs to handle invalid/missing executable paths gracefully (e.g. app was moved or uninstalled since being set). Should probably allow removing/editing a saved custom entry.

Contribution

• I would be open to helping implement this.

[kethma-sansiluni]

Yeah! This will be very useful

[seniru-dilmith]

I took a run at this and have it working on a branch, if it's useful: seniru-dilmith:feat/open-in-custom-application

What it does: adds an "Open with…" entry to the Open dropdown that lists the applications actually installed on the environment host. You pick one by name and it opens the project folder. The pick becomes the default for the Open button and joins the menu; the same dialog takes it back out.

One deviation from what I originally asked for: I couldn't invoke the OS's own "Open with" chooser. macOS has no scriptable chooser (it's a Finder submenu), Windows' OpenAs_RunDLL targets files rather than folders, and Linux has no standard CLI for it. So the list is rendered in T3's own dialog from a read-only scan of the platform's application registry — .desktop entries across XDG_DATA_DIRS, .app bundles on macOS, Start Menu shortcuts on Windows.

Why the scan runs server-side: the launcher already spawns on the environment host, so discovery happens there too. That keeps the list describing the machine that actually runs the command, and it means the feature works from web and mobile rather than desktop only.

Two things I tried to be careful about:

• The command is only ever read from server settings, never accepted from a client payload, so naming a custom:<slug> id can't make the host run an arbitrary binary. Entries are also availability-probed alongside the built-in editors, so an uninstalled program drops out of the menu instead of failing on launch.
• The 30s scan cache uses the manual Ref pattern from externalLauncher.ts rather than cachedWithTTL, following the comment there about memoizing an interrupt from a client that disconnects mid-scan.

It's roughly 1,000 lines of source plus 350 of tests, which is well past what the PR template asks for, and I see you're not actively taking contributions right now. So rather than dropping it on you unsolicited: is this something you'd want a PR for? Happy to split it into smaller pieces, or to leave it here if it's not a direction you want.

[seniru-dilmith]

These are the screenshots of the work I did.

The open with menu icon:

App Selection menu (with the support to add/remove apps from the opening menu at top):

After Selecting antigravity from the app list:

[juliusmarminge]

Closing as a duplicate of #7055, which already tracks custom applications and configurable Open menu entries. The implementation notes and screenshots here remain useful for that work.

[dkritarth]

I ran into this as well. On my setup, the Open menu only offers VS Code and Cursor, but I use a different editor. A selector for an installed application, or a configurable command/path per project, would let T3 open the selected project folder directly. A global default plus a per-project override would be ideal. This would avoid having to open the folder manually outside T3.