feat(git): add graph view + branch switcher dropdown

package.json

@@ -276,6 +276,8 @@
 		"@fastify/rate-limit": "^9.1.0",
 		"@fastify/static": "^7.0.4",
 		"@fastify/websocket": "^9.0.0",
+		"@gitgraph/core": "^1.5.0",
+		"@gitgraph/react": "^1.6.0",
 		"@lezer/highlight": "^1.2.3",
 		"@sentry/electron": "^7.13.0",
 		"@tanstack/react-virtual": "^3.13.13",

src/__tests__/renderer/components/MainPanel.test.tsx

@@ -21,6 +21,12 @@ import {
 
 // Mock child components to simplify testing - must be before MainPanel import
 
+// useModalLayer is no-op in tests — MainPanel does not provide LayerStackProvider,
+// and the BranchSwitcherDropdown registers a layer when rendered.
+vi.mock('../../../renderer/hooks/ui/useModalLayer', () => ({
+	useModalLayer: () => {},
+}));
+
 // TerminalView: forwardRef stub that records render calls per session so we can
 // assert persistence (kept mounted) vs destruction (unmounted) across sessions.
 const terminalViewSessions: string[] = [];
@@ -198,6 +204,9 @@ vi.mock('../../../renderer/components/InlineWizard', () => ({
 vi.mock('../../../renderer/services/git', () => ({
 	gitService: {
 		getDiff: vi.fn().mockResolvedValue({ diff: 'mock diff content' }),
+		getBranches: vi.fn().mockResolvedValue([]),
+		getGraph: vi.fn().mockResolvedValue([]),
+		switchBranch: vi.fn().mockResolvedValue({ success: true, stderr: '' }),
 	},
 }));
 
@@ -1750,8 +1759,7 @@ describe('MainPanel', () => {
 			expect(writeText).toHaveBeenCalledWith('main');
 		});
 
-		it('should open git log when clicking on SSH remote git badge', async () => {
-			const setGitLogOpen = vi.fn();
+		it('should open branch switcher when double-clicking on SSH remote git badge', async () => {
 			const session = createSession({
 				isGitRepo: true,
 				sessionSshRemoteConfig: { enabled: true, remoteId: 'ssh-remote-123' },
@@ -1764,6 +1772,60 @@ describe('MainPanel', () => {
 			});
 			vi.mocked(window.maestro.sshRemote.getConfigs).mockImplementation(mockGetConfigs);
 
+			render(<MainPanel {...defaultProps} activeSession={session} />);
+
+			await waitFor(() => {
+				expect(screen.getByText('my-ssh-remote')).toBeInTheDocument();
+			});
+
+			fireEvent.doubleClick(screen.getByText('my-ssh-remote'));
+
+			// Branch switcher dropdown opens (revealed by its filter input).
+			expect(await screen.findByPlaceholderText(/Filter branches/)).toBeInTheDocument();
+			expect(gitService.getBranches).toHaveBeenCalled();
+		});
+
+		it('should open branch switcher on Shift+Enter on SSH remote git badge (keyboard a11y)', async () => {
+			const session = createSession({
+				isGitRepo: true,
+				sessionSshRemoteConfig: { enabled: true, remoteId: 'ssh-remote-123' },
+			});
+
+			const mockGetConfigs = vi.fn().mockResolvedValue({
+				success: true,
+				configs: [{ id: 'ssh-remote-123', name: 'my-ssh-remote' }],
+			});
+			vi.mocked(window.maestro.sshRemote.getConfigs).mockImplementation(mockGetConfigs);
+
+			render(<MainPanel {...defaultProps} activeSession={session} />);
+
+			await waitFor(() => {
+				expect(screen.getByText('my-ssh-remote')).toBeInTheDocument();
+			});
+
+			// The chip's button is the parent of the SSH remote name span.
+			const chipButton = screen.getByText('my-ssh-remote').closest('button');
+			expect(chipButton).not.toBeNull();
+			fireEvent.keyDown(chipButton!, { key: 'Enter', shiftKey: true });
+
+			// Branch switcher dropdown opens via the keyboard path.
+			expect(await screen.findByPlaceholderText(/Filter branches/)).toBeInTheDocument();
+			expect(gitService.getBranches).toHaveBeenCalled();
+		});
+
+		it('should open git log when single-clicking on SSH remote git badge', async () => {
+			const setGitLogOpen = vi.fn();
+			const session = createSession({
+				isGitRepo: true,
+				sessionSshRemoteConfig: { enabled: true, remoteId: 'ssh-remote-123' },
+			});
+
+			const mockGetConfigs = vi.fn().mockResolvedValue({
+				success: true,
+				configs: [{ id: 'ssh-remote-123', name: 'my-ssh-remote' }],
+			});
+			vi.mocked(window.maestro.sshRemote.getConfigs).mockImplementation(mockGetConfigs);
+
 			render(<MainPanel {...defaultProps} activeSession={session} setGitLogOpen={setGitLogOpen} />);
 
 			await waitFor(() => {
@@ -1772,7 +1834,8 @@ describe('MainPanel', () => {
 
 			fireEvent.click(screen.getByText('my-ssh-remote'));
 
-			expect(setGitLogOpen).toHaveBeenCalledWith(true);
+			// Single click is debounced (~220ms) before opening git log.
+			await waitFor(() => expect(setGitLogOpen).toHaveBeenCalledWith(true), { timeout: 1000 });
 		});
 
 		it('should call gitService.getDiff with SSH remote ID when session has SSH remote config enabled', async () => {

src/main/ipc/handlers/git.ts

@@ -352,6 +352,92 @@ export function registerGitHandlers(_deps: GitHandlerDependencies): void {
 		)
 	);
 
+	// Topology data for graph view: includes parent hashes for lane rendering.
+	ipcMain.handle(
+		'git:graph',
+		withIpcErrorLogging(
+			handlerOpts('graph'),
+			async (
+				cwd: string,
+				options?: { limit?: number },
+				sshRemoteId?: string,
+				remoteCwd?: string
+			) => {
+				const sshRemote = sshRemoteId ? getSshRemoteById(sshRemoteId) : undefined;
+				const effectiveRemoteCwd = sshRemote ? remoteCwd || cwd : undefined;
+				const limit = options?.limit || 200;
+				// Use ASCII Unit Separator (U+001F, written as %x1f in git's pretty-format)
+				// between fields. `|` was tempting but author names and subjects can legally
+				// contain it, which silently corrupts every field after the offending one.
+				// US is a non-printing control character that never appears in real text.
+				const args = [
+					'log',
+					'--all',
+					`--max-count=${limit}`,
+					'--pretty=format:GRAPH_START%H%x1f%P%x1f%an%x1f%ad%x1f%D%x1f%s',
+					'--date=iso-strict',
+				];
+				const result = await execGit(args, cwd, sshRemote, effectiveRemoteCwd);
+				if (result.exitCode !== 0) {
+					return { nodes: [], error: result.stderr };
+				}
+				const nodes = result.stdout
+					.split('GRAPH_START')
+					.filter((c) => c.trim())
+					.map((block) => {
+						const trimmed = block.trim();
+						const [hash = '', parents = '', author = '', date = '', refs = '', ...subj] =
+							trimmed.split('\x1f');
+						return {
+							hash,
+							shortHash: hash.slice(0, 7),
+							parents: parents ? parents.split(' ').filter(Boolean) : [],
+							author,
+							date,
+							refs: refs ? refs.split(', ').filter((r) => r.trim()) : [],
+							// Re-join with the same separator in case the subject itself contained one
+							// (extremely unlikely for a control character, but cheap to be correct).
+							subject: subj.join('\x1f'),
+						};
+					});
+				return { nodes, error: null };
+			}
+		)
+	);
+
+	// Switch to an existing branch in the current working tree.
+	// Returns success=false with stderr text on failure (e.g., dirty working tree).
+	ipcMain.handle(
+		'git:switch',
+		withIpcErrorLogging(
+			handlerOpts('switch'),
+			async (cwd: string, branchName: string, sshRemoteId?: string, remoteCwd?: string) => {
+				// Reject flag-like names so a caller can't pass e.g. "-c new-branch" or "-C"
+				// and have git interpret it as a switch flag. execFile blocks shell
+				// injection but not flag injection.
+				if (
+					typeof branchName !== 'string' ||
+					branchName.length === 0 ||
+					branchName.startsWith('-')
+				) {
+					return {
+						success: false,
+						stdout: '',
+						stderr: `Invalid branch name: ${branchName}`,
+					};
+				}
+				const sshRemote = sshRemoteId ? getSshRemoteById(sshRemoteId) : undefined;
+				const effectiveRemoteCwd = sshRemote ? remoteCwd || cwd : undefined;
+				const result = await execGit(['switch', branchName], cwd, sshRemote, effectiveRemoteCwd);
+				return {
+					success: result.exitCode === 0,
+					stdout: result.stdout,
+					stderr: result.stderr,
+				};
+			}
+		)
+	);
+
 	ipcMain.handle(
 		'git:commitCount',
 		withIpcErrorLogging(

src/main/preload/git.ts

@@ -56,6 +56,19 @@ export interface GitLogEntry {
 	subject: string;
 }
 
+/**
+ * Git graph node — like GitLogEntry but with parent hashes for topology rendering.
+ */
+export interface GitGraphNode {
+	hash: string;
+	shortHash: string;
+	parents: string[];
+	author: string;
+	date: string;
+	refs: string[];
+	subject: string;
+}
+
 /**
  * Discovered worktree event data
  */
@@ -207,6 +220,29 @@ export function createGitApi() {
 			error: string | null;
 		}> => ipcRenderer.invoke('git:log', cwd, options, sshRemoteId),
 
+		/**
+		 * Get topology graph data (commits with parent hashes) for graph rendering
+		 */
+		graph: (
+			cwd: string,
+			options?: { limit?: number },
+			sshRemoteId?: string,
+			remoteCwd?: string
+		): Promise<{ nodes: GitGraphNode[]; error: string | null }> =>
+			ipcRenderer.invoke('git:graph', cwd, options, sshRemoteId, remoteCwd),
+
+		/**
+		 * Switch the current working tree to an existing branch.
+		 * Returns success=false on dirty working tree (stderr contains git's message).
+		 */
+		switchBranch: (
+			cwd: string,
+			branchName: string,
+			sshRemoteId?: string,
+			remoteCwd?: string
+		): Promise<{ success: boolean; stdout: string; stderr: string }> =>
+			ipcRenderer.invoke('git:switch', cwd, branchName, sshRemoteId, remoteCwd),
+
 		/**
 		 * Get commit count
 		 */