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+# Split terminal view for the Workspace console
+
+**Status:** approved 2026-08-14.
+
+## Problem
+
+`Workspace.tsx` renders exactly one lane's run console at a time: a single
+`RunSetup`/`TerminalView` switcher (client/src/pages/Workspace.tsx:789-824)
+driven by page-level state (`selectedLaneId`, `prompt`, `cwd`, `model`,
+`permissionMode`, `effort`, `resumeSession`, `handle`, `busy`, `activeRuns`,
+`runHistory`, `cwdSuggestions`). Lanes are independent working directories
+that can each have their own live tmux/PTY session running concurrently on
+the server (`server/lib/pty-attach.js`), but the dashboard can only show one
+at a time — comparing two lanes' output means switching back and forth.
+
+The user wants to view multiple lanes' terminals side by side: 1 pane (today's
+behavior), 2 panes (left/right), or 4 panes (2x2 grid).
+
+## Approach
+
+**Extract a self-contained `LaneConsolePane` component.** Move the existing
+RunSetup/TerminalView switcher and all its state out of `Workspace.tsx` into
+its own component that owns one lane's run lifecycle independently. Each
+pane gets its own `laneId` (chosen via a dropdown in the pane header, listing
+all lanes, not just ones with an active run) and manages its own
+prompt/cwd/model/permissionMode/effort/resumeSession/handle/busy/activeRuns/
+runHistory state — nothing is shared across panes.
+
+Workspace keeps a `paneLaneIds: (number | null)[]` array sized to the current
+layout (1, 2, or 4) and renders that many `LaneConsolePane` instances in a
+CSS grid. This is the only viable approach given the existing state model is
+single-lane; the alternative (keeping one shared state object indexed by
+lane) would require rewriting every handler in Workspace.tsx to be
+lane-aware and is a much larger, riskier diff for the same result.
+
+## Layout
+
+A layout toggle (1 / 2 / 4 buttons) sits next to the existing console
+header. Grid via CSS:
+
+- **1**: full width — identical to today.
+- **2**: `grid-cols-2` — left/right.
+- **4**: `grid-cols-2 grid-rows-2` — four corners.
+
+Each pane has a small header with a lane-select dropdown. If the selected
+lane has no active run, the pane shows a compact `RunSetup` (reused
+component, same as today's pre-run form) so the user can start one directly
+from the pane. If it has an active run, the pane shows `TerminalView` as
+today.
+
+## Persistence
+
+The chosen layout mode and each pane's selected `laneId` are saved to
+`localStorage` (e.g. key `ccam.workspace.splitView`) and restored on next
+visit to Workspace. If a persisted lane no longer exists, that pane falls
+back to unselected (dropdown placeholder).
+
+## Non-goals
+
+- No server/API changes — this is purely a client-side rendering feature.
+  Each lane's run already exists independently server-side; this just lets
+  the UI display more than one at once.
+- No synchronized input across panes (typing in one pane's terminal does not
+  affect others) — each `TerminalView` keeps its own independent WebSocket
+  connection, unchanged from today's single-instance behavior.
+
+## Testing
+
+- `client/src/pages/__tests__/Workspace.test.tsx` currently mocks
+  `TerminalView` and exercises the single-console flow; update it (or add a
+  sibling test file) to cover: layout toggle, per-pane lane dropdown,
+  starting a run from within a pane, and multiple panes rendering
+  independent `TerminalView`/`RunSetup` instances.
+- Run `npm run test:client` before considering this done.