Per-project default browser profile (so agent-opened tabs use the right profile)

[direksethi]

Problem or use case

Browser profiles are a great addition. I use them to keep two worlds apart: one profile is logged into my work accounts and one is logged into my personal/client accounts. Mixing them up means signing into the wrong account or giving an agent access to the wrong world.

The problem is that the profile a new tab uses is decided by a single global setting (browserDefaultProfileId, set with "Set as default" in Settings → Browser). When an agent opens a browser, it always gets that one profile, whatever project the thread belongs to.

In practice:

• I work in a work project, and the agent opens a tab in my personal profile (or the reverse).
• The agent can't fix this itself, because the agent browser tools (preview_open, preview_navigate, …) don't accept a profile.
• The only workaround is to remember to change the global default every time I switch projects, or to catch the tab and switch it by hand before the agent does anything.

Proposed solution

Let a project (workspace root) set its own default browser profile:

1. Per-project default profile. Add a "Browser profile" option in the project's settings (or its context menu in the sidebar) with the choices Use global default (the default) or any configured profile.
2. Resolution order when opening a tab: thread override (if ever added) → project default → global browserDefaultProfileId → default.
3. Agent-opened tabs use it. When an agent opens or reuses a tab for a thread, it gets that thread's project profile automatically, with no agent involvement needed.
4. Nice to have: an optional profileId on preview_open, so agents or skills can ask for a specific profile explicitly. If the requested profile doesn't match the project's profile, it's reasonable to show a warning or refuse.
5. Nice to have: show the active profile name in the browser toolbar for agent-opened tabs, so it's obvious which world a tab is in.

A simpler first step that would already solve most of this: store an optional browserProfileId on the project and use it instead of browserDefaultProfileId when a thread in that project opens a tab.

Why this matters

Profiles exist to keep cookies and logins separate. Today the separation only holds if the user remembers to flip a global setting, and agents open tabs without asking, so the risky moments are exactly when nobody is watching. A per-project default makes the safe behaviour automatic. It matters most for people who do client or freelance work next to a day job, or who run several clients in parallel.

Environment

T3 Code (Nightly) 0.0.43-nightly.20260922.2123, macOS.

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Also filed as an issue: #13254

[juliusmarminge]

Duplicate of tracking issue #13254 (same feature request; this discussion notes it was also filed there). Closing this discussion so we track the work on the issue.

Related but not the same: open PR #9704 adds optional profileId on preview_open only — it does not add a per-project default profile.