[FEATURE]: Pinned session tabs in the TUI sidebar #24451

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Note on possible duplicates

The compliance bot flagged #24400 as a possible duplicate. They both touch the right sidebar but propose different things:

• [FEATURE]: expansion of the side panel #24400 asks for Recent Projects and Installed Plugins collapsible sections (project switching + plugin management).
• This issue asks for a live, persistent SESSIONS panel — pinned + ephemeral entries with per-row spinner/idle indicators driven by session.status SSE events. The goal is parallel-session orchestration, not project/plugin management.

The two are complementary; neither subsumes the other.

Problem

Working on multiple sessions in parallel today means juggling several terminal windows running separate opencode instances. The TUI is single-session: switching between sessions only happens via the DialogSessionList modal (<leader>l), which closes after each pick and gives no visibility on what other sessions are doing in the background.

I keep one session per task/issue and constantly want to (a) glance at whether another session is still working and (b) jump back to it without re-searching the list.

Proposed enhancement

Add a small "SESSIONS" panel at the top of the existing right sidebar. It would show:

• Pinned sessions — a stable, persistent list curated by the user (<leader>p to pin/unpin).
• Ephemeral entries — sessions visited in the current TUI run that aren't pinned, plus any session that's currently busy/retrying elsewhere. They stay listed until the TUI restarts or the user closes them, so a new prompt you just submitted doesn't disappear when you click another tab.

Each row shows a live status indicator (spinner when the model is generating, retry glyph for retry, dot for idle). Pinned rows pick up theme.primary, ephemeral rows pick up theme.secondary, so the distinction adapts to the active theme.

UX details

• Pin/unpin: <leader>p (/pin). Toggles the active session.
• Close tab: <leader>w. Drops a pinned session from the list (or removes an ephemeral one from this run's history); falls back to a neighbour tab.
• Switch tabs: ctrl+up / ctrl+down. Direct keybinds (no leader) so they work on any keyboard layout — [/] would have required Option on non-US Mac layouts.
• All four actions are also registered in the command palette (Ctrl+P), so they're discoverable without learning the keybinds first.
• Pinned set is persisted per-project-directory at ~/.local/share/opencode/state/session-tabs.json. Visited (ephemeral) set is in-memory only and clears on TUI restart.
• Sidebar can still be hidden with <leader>b (existing sidebar_toggle); no change to the layout when it's collapsed.

Why I think it belongs in OpenCode

• The server already supports concurrent sessions (SessionRunState keeps an independent Runner per SessionID) and emits session.status events the TUI already consumes (sync.tsx).
• The data path is therefore zero new infrastructure — this is purely a UI layer over state that already exists.
• It removes a real friction point for anyone running multiple parallel agents from a single terminal.

I have a working implementation ready as draft PR #24452 (pending design review per CONTRIBUTING).

Inspiration

The interaction is loosely inspired by lanes.sh, which keeps a live tab bar of CLI tasks. Kept entirely inside opencode and scoped to opencode sessions only — no separate dashboard, no extra binary.

Screenshot