Inherit cwd from the source pane when splitting (#4)

When a split is initiated from an existing pane, the new pane spawns
with the source pane's last-known cwd. Remote cwds (e.g. OSC 7 over
ssh) are skipped since they aren't usable as a local spawn directory.

The inherited cwd rides through setPendingShellOpts alongside the
inherited shell selection and is consumed by getOrCreateTerminal on
the next platform.spawnPty.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: nedtwigg

docs/specs/layout.md

@@ -179,6 +179,10 @@ All handled in a single capture-phase `keydown` listener on `window`. Every hand
 | `t` | Toggle TODO flag | — |
 | `a` | Dismiss or toggle alert | — |
 
+### Split cwd inheritance
+
+When a split is initiated from an existing pane (via `"`/`%`, the header split buttons, or `Cmd/Ctrl+Click` on a split icon), the new pane spawns with its source pane's last-known cwd as the spawn directory. The source cwd is read from `getTerminalPaneState(sourceId).cwd`; remote cwds (`isRemote === true`, e.g. an OSC 7 path reported over ssh) are ignored because they aren't usable as a local spawn cwd. When no source cwd is known, when the split has no source pane (initial pane creation), or when the source is remote, the host's default cwd applies. The inherited cwd rides through `setPendingShellOpts` alongside the inherited shell selection and is consumed by `getOrCreateTerminal` on the next `platform.spawnPty`.
+
 ### Kill confirmation
 
 Pressing `x` (or clicking the kill button) enters command mode and shows a pane-centered semi-transparent overlay (`KillConfirmOverlay` → `KillConfirmCard`) with a random uppercase letter (A-Z, excluding X). Typing that letter confirms the kill (destroys session, removes pane). Cancel with Escape key, clicking the `[ESC] to cancel` button, or clicking another panel. Any other key triggers a shake animation (400ms `shake-x` keyframe) then auto-dismisses the confirmation.

lib/src/components/Wall.tsx

@@ -18,6 +18,7 @@ import {
   toggleSessionTodo,
   setPendingShellOpts,
   getDefaultShellOpts,
+  getTerminalPaneState,
   isUntouched,
   setTerminalUserTitle,
   UNNAMED_PANEL_TITLE,
@@ -610,8 +611,12 @@ export function Wall({
     const ref = id && api.getPanel(id) ? id : null;
     // Carry the currently-selected shell into the split, same as [+].
     const defaults = getDefaultShellOpts();
-    if (defaults?.shell) {
-      setPendingShellOpts(newId, { shell: defaults.shell, args: defaults.args });
+    // Inherit the source pane's cwd when known and local (diffplug/mouseterm#4).
+    // Remote cwds (e.g. from OSC 7 over ssh) aren't usable as a local spawn cwd.
+    const sourceCwd = ref ? getTerminalPaneState(ref).cwd : null;
+    const inheritedCwd = sourceCwd && !sourceCwd.isRemote ? sourceCwd.path : undefined;
+    if (defaults?.shell || inheritedCwd) {
+      setPendingShellOpts(newId, { shell: defaults?.shell, args: defaults?.args, cwd: inheritedCwd });
     }
     // Horizontal split places the new pane to the right → reveal from its left edge.
     // Vertical split places it below → reveal from its top edge.

lib/src/lib/terminal-lifecycle.ts

@@ -207,7 +207,7 @@ function setupTerminalEntry(id: string, options: { untouched?: boolean } = {}):
   return entry;
 }
 
-export function setPendingShellOpts(id: string, opts: { shell?: string; args?: string[] }): void {
+export function setPendingShellOpts(id: string, opts: { shell?: string; args?: string[]; cwd?: string }): void {
   pendingShellOpts.set(id, opts);
 }
 

lib/src/lib/terminal-registry.alert.test.ts

@@ -107,6 +107,7 @@ import {
   markSessionTodo,
   resumeTerminal,
   restoreTerminal,
+  setPendingShellOpts,
   swapTerminals,
   toggleSessionAlert,
   toggleSessionTodo,
@@ -962,3 +963,60 @@ describe('terminal-registry alert behavior', () => {
     });
   });
 });
+
+describe('pending shell opts → spawnPty', () => {
+  let spawnSpy: ReturnType<typeof vi.spyOn>;
+
+  beforeEach(() => {
+    vi.useFakeTimers();
+    fakePlatform.reset();
+    initAlertStateReceiver();
+    const documentElement = new MockElement();
+    vi.stubGlobal('document', {
+      createElement: () => new MockElement(),
+      documentElement,
+    });
+    vi.stubGlobal('getComputedStyle', () => ({
+      getPropertyValue: () => '#000000',
+    }));
+    vi.stubGlobal('requestAnimationFrame', (callback: FrameRequestCallback) => {
+      callback(0);
+      return 0;
+    });
+    vi.stubGlobal('MutationObserver', class { observe() {} disconnect() {} });
+    vi.stubGlobal('window', {
+      addEventListener: () => {},
+      removeEventListener: () => {},
+    });
+    spawnSpy = vi.spyOn(fakePlatform, 'spawnPty');
+  });
+
+  afterEach(() => {
+    disposeAllSessions();
+    fakePlatform.reset();
+    spawnSpy.mockRestore();
+    vi.unstubAllGlobals();
+    vi.useRealTimers();
+  });
+
+  it('forwards a pending cwd to spawnPty (split inherits source pane cwd)', () => {
+    const id = 'split-with-cwd';
+
+    setPendingShellOpts(id, { shell: '/bin/zsh', args: ['-l'], cwd: '/home/user/project' });
+    getOrCreateTerminal(id);
+
+    expect(spawnSpy).toHaveBeenCalledWith(
+      id,
+      expect.objectContaining({ shell: '/bin/zsh', args: ['-l'], cwd: '/home/user/project' }),
+    );
+  });
+
+  it('omits cwd when no pending opts were set', () => {
+    const id = 'split-without-cwd';
+
+    getOrCreateTerminal(id);
+
+    const options = spawnSpy.mock.calls[0]?.[1] as { cwd?: string } | undefined;
+    expect(options?.cwd).toBeUndefined();
+  });
+});

lib/src/lib/terminal-store.ts

@@ -37,7 +37,7 @@ export interface TerminalOverlayDims {
 }
 
 export const registry = new Map<string, TerminalEntry>();
-export const pendingShellOpts = new Map<string, { shell?: string; args?: string[] }>();
+export const pendingShellOpts = new Map<string, { shell?: string; args?: string[]; cwd?: string }>();
 
 export function getEntryByPtyId(ptyId: string): TerminalEntry | null {
   for (const entry of registry.values()) {