[Feature]: Filter sidebar threads by who started them

[niieani]

Area

apps/web, apps/mobile

Problem or use case

Threads started by agents now outnumber the ones I start myself: outside agents launching
through /mcp, delegate_task children, scheduled tasks. The thread view already marks a
thread as started by an agent, but the sidebar can only be narrowed by project (and
environment on mobile, #8948 for desktop). There's no way to see "only threads I started"
or "only threads an agent started" without opening each one.

Proposed solution

Add a "Started by" filter next to the project filter in the sidebar:

• Me (createdBy: user)
• Agents (createdBy: agent), optionally split by source: outside agent (mcp), scheduled task, delegated task
• All (default)

Both fields already live on every thread (createdBy, creationSource), so this is a client-side filter
with no server changes. The choice should persist across navigation (cf. #9379).

Optional follow-up: record which outside agent (its OAuth client name) launched a thread and
show it on the thread, so several outside agents can be told apart. Today every outside launch
is recorded as creationSource: "mcp".

Happy to open PR.

Alternatives considered

Collapsing agent-started threads into a group, like subagents under their parent. A filter is
simpler and also works for search results.

Additional context

Related: #1043 (status filters, closed), #3523, #8948.

[ANTVirGEO]

A concrete use case and a small UX suggestion.

I coordinate work through an agent that starts executor threads via t3 thread start and MCP. On a normal day most of my active threads were started by agents, and the few I started myself get buried. All of them show up as identical rows.

Since createdBy and creationSource already exist on every thread, and #16699 adds the "opened by an agent" marker, a filter like this would cover it:

• A small segmented control (or tabs) at the top of the thread list: All · Mine · Agents. It filters every section (Pinned, Active, Working, Snoozed, Settled) instead of adding new sections, so settle, snooze and pin work as they do today.
• Each segment shows a count and a dot when a thread in it needs me (an approval, a question or a failure), so a filtered-out agent thread that needs me doesn't get lost.
• Keybindings: new commands such as sidebar.filter.all / sidebar.filter.mine / sidebar.filter.agents. Default mod+shift+1/2/3 would be nice, but Cmd+Shift+3 is the macOS screenshot shortcut, so they could also ship unbound or on mod+alt+1/2/3. mod+1…9 thread jumps should follow the active filter, as they already do for the project filter.
• The choice persists per device.

Related: #18017 (hiding agent-to-agent threads), #20940 / #21266 (grouping launched threads under their launcher), #11998 (manual groups).

[willsheldon]

Another use case, and what I built for it in a local build.

Most of my threads are started by an orchestrating agent, and they run on several provider accounts (two Claude accounts and a Codex account). I needed to narrow the sidebar by who started a thread, as proposed here, and also by which account a thread runs on.

My build filters by thread title, because my agent-launched threads have predictable title prefixes. The createdBy / creationSource filter proposed here is the better answer for "who started it", and I would use it instead of title rules for that.

What I run today, on web and desktop, beside the sidebar search and separate from the project filter:

• Account. Keep only threads that run on one provider instance. The key is environment plus provider instance, so the same account on two machines is listed twice, with the machine named. An account that is no longer available shows as "Unavailable account" until cleared.
• Title rules. Up to 20 rules. Each one hides matching threads or shows only matching threads, as plain text or a regular expression, case-insensitive. An invalid expression shows its error and has no effect. If an expression makes the sidebar unresponsive, the rule is turned off and marked on next start.
• A chip row under the search field shows each active rule and the account, with a count of hidden threads. Clicking a chip turns that rule off or on.
• Search and section counts follow the filter. The open thread stays visible even when the filter would hide it. The filter is client-side only, persists per device, and has a settings switch to hide it.

If an account filter or title rules would be useful alongside "Started by", I am happy to share the code or open a focused PR for whichever part you want, rebuilt on current main. The current implementation is on the local/patched-build-20261028 branch of willsheldon/t3code (apps/web/src/components/sidebar/enhancedFilter.ts and the sidebar wiring).

[TimFux11]

Same need here, in a slightly different shape. A few coordinator agents in my setup launch their own top-level threads through MCP (t3_thread_launch), one per piece of work. In my last 60 threads, 12 were agent-started top-level threads and only 3 were mine. Sub-agent threads already nest under their parent, so they aren't the problem.

Instead of a filter, I'd like agent-started threads (createdBy: agent) to get their own collapsible section at the bottom of the sidebar, next to Working, Snoozed and Settled. Nothing is hidden, only moved. An agent thread that's asking for input or has a permission request stays in the main list until it's answered, so I don't miss it.

For now I'm patching this into my own build of v0.1.6. If a maintainer approves the direction, I can share the patch or open a focused PR.