feat(plugins): add export-format registration hook to plugin API

Add context.formats.registerExportFormat(id, opts) to PluginContext,
backed by a new FormatRegistry (mirrors PluginRegistry's Map-based
shape). Plugins register namespaced (${pluginId}:${id}) export
formats with a label/extension/handler; the writing-studio built-in
plugin registers a trivial "sprint-summary" .txt export as a
worked example.

The plugin system lives entirely in the renderer process while the
Export menu is built in main.js, so wiring formats into the menu
required a small IPC round-trip: renderer sends format metadata to
main after plugin load (main rebuilds the menu via the already-
idempotent createMenu()), and a menu click sends the resolved save
path back to the renderer, which is the only process holding the
plugin's handler function.

Amit Haridas

src/main.js

@@ -419,6 +419,7 @@ let pandocVersionCache = null; // Cached parsed { major, minor } from `pandoc --
 let wordTemplatePath = null; // Path to selected Word template
 let templateStartPage = 3; // Which page to start inserting content (default: page 3)
 let rendererReady = false; // Track if renderer is ready to receive file data
+let pluginExportFormats = []; // Export formats registered by plugins: [{ id, label, extension }]
 
 // Header & Footer Settings
 let headerFooterSettings = {
@@ -997,6 +998,7 @@ function createMenu() {
               label: 'Jupyter Notebook (.ipynb)',
               click: () => exportFile('ipynb'),
             },
+            ...buildPluginExportMenuItems(),
           ],
         },
         {
@@ -1895,6 +1897,42 @@ function exportFile(format) {
 function showExportOptionsDialog(format) {
   mainWindow.webContents.send('show-export-dialog', format);
 }
+
+// Build the dynamic tail of the Export submenu from plugin-registered
+// formats (see plugin-export-formats-registered IPC handler below). Returns
+// [] when no plugin has registered a format, so the Export menu is
+// unchanged for a plain install.
+function buildPluginExportMenuItems() {
+  if (!pluginExportFormats.length) return [];
+  const items = pluginExportFormats.map((fmt) => ({
+    label: fmt.label || fmt.id,
+    click: () => runPluginExportFormat(fmt),
+  }));
+  return [{ type: 'separator' }, ...items];
+}
+
+// Resolve an output path for a plugin-registered export format (main
+// process owns save dialogs, same as every other export path in this
+// file), then hand off to the renderer — the plugin's handler function
+// only exists there, since that's the process that loaded the plugin.
+function runPluginExportFormat(fmt) {
+  if (!currentFile) {
+    dialog.showErrorBox('Error', 'Please save the file first');
+    return;
+  }
+  const ext = fmt.extension || 'txt';
+  const outputFile = dialog.showSaveDialogSync(mainWindow, {
+    defaultPath: currentFile.replace(/\.[^/.]+$/, `.${ext}`),
+    filters: [
+      {
+        name: fmt.label || fmt.id,
+        extensions: [ext],
+      },
+    ],
+  });
+  if (!outputFile) return; // User cancelled
+  mainWindow.webContents.send('run-plugin-export-format', { id: fmt.id, outputPath: outputFile });
+}
 function showBatchConversionDialog() {
   mainWindow.webContents.send('show-batch-dialog');
 }
@@ -4637,6 +4675,28 @@ ipcMain.on('clear-recent-files', (event) => {
   }
 });
 
+// Plugins (loaded in the renderer) report the export formats they've
+// registered; rebuild the Export menu so they show up as entries.
+// createMenu() is idempotent and already re-invoked elsewhere (e.g. after
+// clearRecentFilesOnDisk() above) so calling it again here is safe.
+ipcMain.on('plugin-export-formats-registered', (event, formats) => {
+  pluginExportFormats = Array.isArray(formats)
+    ? formats.filter((f) => f && typeof f.id === 'string')
+    : [];
+  createMenu();
+});
+
+// Result of a plugin export handler running in the renderer (see
+// runPluginExportFormat() / the Export menu wiring above).
+ipcMain.on('plugin-export-format-result', (event, result) => {
+  const { outputPath, success, error } = result || {};
+  if (success) {
+    showExportSuccess(outputPath);
+  } else {
+    dialog.showErrorBox('Export Error', sanitizeErrorMessage(error || 'Unknown error'));
+  }
+});
+
 // Handle file opening on macOS
 app.on('open-file', (event, filePath) => {
   event.preventDefault();

src/plugins/built-in/writing-studio/index.js

@@ -29,6 +29,7 @@ class WritingStudioPlugin extends PluginAPI {
 
     this._registerCommands(context);
     this._registerStatusBar(context);
+    this._registerExportFormats(context);
   }
 
   _registerCommands(context) {
@@ -120,6 +121,42 @@ class WritingStudioPlugin extends PluginAPI {
     });
   }
 
+  // Example usage of context.formats.registerExportFormat (Task 17): adds
+  // a "Writing Studio Summary" entry to the Export menu that writes a
+  // plain-text snapshot of today's sprint/goal progress instead of going
+  // through Pandoc. Doubles as documentation for how a plugin can offer
+  // its own export target.
+  _registerExportFormats(context) {
+    const { sprintEngine, goalTracker } = this;
+
+    context.formats.registerExportFormat('sprint-summary', {
+      label: 'Writing Studio Summary (.txt)',
+      extension: 'txt',
+      handler: async (markdownContent, outputPath) => {
+        const fs = require('fs');
+        const goal = context.settings.get('dailyGoal') || 1000;
+        const progress = goalTracker.getDailyProgress(goal);
+        const streak = goalTracker.getStreak(goal);
+        const wordCount = (markdownContent || '').split(/\s+/).filter(Boolean).length;
+
+        const lines = [
+          'Writing Studio Summary',
+          '=======================',
+          `Generated: ${new Date().toISOString()}`,
+          '',
+          `Document word count: ${wordCount}`,
+          `Daily goal: ${goal}`,
+          `Words written today: ${progress.written} (${progress.pct}%)`,
+          `Current streak: ${streak} day(s)`,
+          `Sprint active: ${sprintEngine.isActive() ? 'yes' : 'no'}`,
+          '',
+        ];
+
+        fs.writeFileSync(outputPath, lines.join('\n'), 'utf-8');
+      },
+    });
+  }
+
   deactivate() {
     if (this._sprintInterval) clearInterval(this._sprintInterval);
   }

src/plugins/built-in/writing-studio/manifest.json

@@ -32,7 +32,14 @@
         "shortcut": "Ctrl+Alt+G"
       }
     ],
-    "statusBar": { "indicators": ["sprint-timer", "word-goal"] }
+    "statusBar": { "indicators": ["sprint-timer", "word-goal"] },
+    "exportFormats": [
+      {
+        "id": "sprint-summary",
+        "label": "Writing Studio Summary (.txt)",
+        "extension": "txt"
+      }
+    ]
   },
   "settings": [
     { "key": "dailyGoal", "type": "number", "default": 1000, "label": "Daily word goal" },

src/plugins/format-registry.js

@@ -0,0 +1,40 @@
+/**
+ * FormatRegistry — tracks export formats registered by plugins via
+ * `context.formats.registerExportFormat(id, opts)`.
+ *
+ * Mirrors the simple Map-backed storage pattern used by PluginRegistry
+ * (see plugin-registry.js), scoped to a single concern: export format
+ * metadata + handler functions rather than whole plugin instances.
+ */
+class FormatRegistry {
+  constructor() {
+    this.formats = new Map();
+  }
+
+  /**
+   * Register (or overwrite) an export format entry.
+   * @param {string} id - Fully-namespaced format id, e.g. "writing-studio:sprint-summary"
+   * @param {object} opts - { label, extension, handler: async (markdownContent, outputPath, options) => void }
+   */
+  register(id, opts) {
+    this.formats.set(id, opts);
+  }
+
+  /**
+   * Look up a single registered format entry by its namespaced id.
+   * @param {string} id
+   * @returns {object|undefined}
+   */
+  get(id) {
+    return this.formats.get(id);
+  }
+
+  /**
+   * Return all registered formats as an array of { id, ...opts }.
+   */
+  getAll() {
+    return Array.from(this.formats.entries()).map(([id, opts]) => ({ id, ...opts }));
+  }
+}
+
+module.exports = { FormatRegistry };

src/plugins/plugin-context.js

@@ -10,10 +10,21 @@ class PluginContext {
    * @param {object} deps.editor - { getContent, getSelection, insertAtCursor, onContentChanged }
    * @param {object} deps.ipc - { invoke, on }
    * @param {object} deps.exportHooks - { preHooks: [], postHooks: [] }
+   * @param {object} deps.formatRegistry - FormatRegistry instance ({ register, get, getAll })
    */
   constructor(deps) {
-    const { pluginId, sidebar, commands, statusBar, eventBus, settings, editor, ipc, exportHooks } =
-      deps;
+    const {
+      pluginId,
+      sidebar,
+      commands,
+      statusBar,
+      eventBus,
+      settings,
+      editor,
+      ipc,
+      exportHooks,
+      formatRegistry,
+    } = deps;
 
     this.sidebar = {
       registerPanel: (id, opts) => sidebar.registerPanel(`${pluginId}:${id}`, opts),
@@ -69,6 +80,19 @@ class PluginContext {
         if (exportHooks) exportHooks.postHooks.push(handler);
       },
     };
+
+    this.formats = {
+      /**
+       * Register a plugin-provided export format. It is namespaced as
+       * `${pluginId}:${id}` so plugins can't collide with each other or
+       * with the built-in Pandoc-backed formats.
+       * @param {string} id - Format id, unique within this plugin.
+       * @param {object} opts - { label, extension, handler: async (markdownContent, outputPath, options) => void }
+       */
+      registerExportFormat: (id, opts) => {
+        if (formatRegistry) formatRegistry.register(`${pluginId}:${id}`, opts);
+      },
+    };
   }
 }
 

src/plugins/plugin-registry.js

@@ -33,6 +33,7 @@ class PluginRegistry {
       editor: this.deps.editor,
       ipc: this.deps.ipc,
       exportHooks: this.exportHooks,
+      formatRegistry: this.deps.formatRegistry,
     });
 
     try {

src/renderer.js

@@ -1817,8 +1817,10 @@ document.addEventListener('DOMContentLoaded', async () => {
   const { PluginRegistry } = require('./plugins/plugin-registry');
   const { EventBus } = require('./plugins/event-bus');
   const { SettingsStore } = require('./plugins/settings-store');
+  const { FormatRegistry } = require('./plugins/format-registry');
   const pluginPath = require('path');
   const pluginEventBus = new EventBus();
+  const pluginFormatRegistry = new FormatRegistry();
   const pluginSettings = new SettingsStore({
     get: (key) => window.electronAPI.invoke('plugin-settings:get', key),
     set: (key, value) =>
@@ -1863,12 +1865,51 @@ document.addEventListener('DOMContentLoaded', async () => {
       invoke: (ch, data) => window.electronAPI.invoke(ch, data),
       on: (ch, cb) => window.electronAPI.on(ch, cb),
     },
+    formatRegistry: pluginFormatRegistry,
   });
   const builtInDir = pluginPath.join(__dirname, 'plugins', 'built-in');
   const loader = new PluginLoader([builtInDir]);
   const discovered = loader.discoverPlugins();
   discovered.forEach((p) => pluginRegistry.register(p));
 
+  // Tell the main process which export formats plugins registered, so the
+  // Export menu (built in main.js, a separate process from this one) can
+  // grow entries for them. Only serializable metadata crosses the IPC
+  // boundary — the handler functions stay here in the renderer, since
+  // that's the only process that actually holds them.
+  ipcRenderer.send(
+    'plugin-export-formats-registered',
+    pluginFormatRegistry.getAll().map(({ id, label, extension }) => ({ id, label, extension }))
+  );
+
+  // Main process resolved a save path (via the Export menu) for a
+  // plugin-registered format; run the plugin's handler with the live
+  // editor content and report back so main can show success/error UI.
+  ipcRenderer.on('run-plugin-export-format', async (event, { id, outputPath } = {}) => {
+    const entry = pluginFormatRegistry.get(id);
+    if (!entry || typeof entry.handler !== 'function') {
+      ipcRenderer.send('plugin-export-format-result', {
+        id,
+        outputPath,
+        success: false,
+        error: `Export format "${id}" is not registered.`,
+      });
+      return;
+    }
+    try {
+      const content = tabManager.getCurrentContent();
+      await entry.handler(content, outputPath, {});
+      ipcRenderer.send('plugin-export-format-result', { id, outputPath, success: true });
+    } catch (err) {
+      ipcRenderer.send('plugin-export-format-result', {
+        id,
+        outputPath,
+        success: false,
+        error: err && err.message ? err.message : String(err),
+      });
+    }
+  });
+
   // Initialize Zen Mode
   const ZenModeClass = getZenMode();
   const zenMode = new ZenModeClass(tabManager);

tests/format-registry.test.js

@@ -0,0 +1,39 @@
+const { FormatRegistry } = require('../src/plugins/format-registry');
+
+describe('FormatRegistry', () => {
+  let registry;
+
+  beforeEach(() => {
+    registry = new FormatRegistry();
+  });
+
+  test('register — stores an entry retrievable by id', () => {
+    const handler = jest.fn();
+    registry.register('plugin-a:fmt', { label: 'Format A', extension: 'txt', handler });
+    const entry = registry.get('plugin-a:fmt');
+    expect(entry).toEqual({ label: 'Format A', extension: 'txt', handler });
+  });
+
+  test('get — returns undefined for unknown id', () => {
+    expect(registry.get('nope')).toBeUndefined();
+  });
+
+  test('register — overwrites an existing id', () => {
+    registry.register('plugin-a:fmt', { label: 'First' });
+    registry.register('plugin-a:fmt', { label: 'Second' });
+    expect(registry.get('plugin-a:fmt').label).toBe('Second');
+  });
+
+  test('getAll — returns all entries with id merged in', () => {
+    registry.register('plugin-a:fmt', { label: 'Format A', extension: 'txt' });
+    registry.register('plugin-b:fmt', { label: 'Format B', extension: 'csv' });
+    const all = registry.getAll();
+    expect(all).toHaveLength(2);
+    expect(all).toContainEqual({ id: 'plugin-a:fmt', label: 'Format A', extension: 'txt' });
+    expect(all).toContainEqual({ id: 'plugin-b:fmt', label: 'Format B', extension: 'csv' });
+  });
+
+  test('getAll — returns empty array when nothing registered', () => {
+    expect(registry.getAll()).toEqual([]);
+  });
+});

tests/plugin-context.test.js

@@ -21,6 +21,7 @@ describe('PluginContext', () => {
       },
       ipc: { invoke: jest.fn(), on: jest.fn() },
       exportHooks: { preHooks: [], postHooks: [] },
+      formatRegistry: { register: jest.fn(), get: jest.fn(), getAll: jest.fn() },
     };
     context = new PluginContext(mockDeps);
   });
@@ -87,4 +88,18 @@ describe('PluginContext', () => {
     context.exports.registerPostHook(handler);
     expect(mockDeps.exportHooks.postHooks).toContain(handler);
   });
+
+  test('exposes formats.registerExportFormat with namespaced id', () => {
+    const handler = jest.fn();
+    const opts = { label: 'My Format', extension: 'txt', handler };
+    context.formats.registerExportFormat('my-format', opts);
+    expect(mockDeps.formatRegistry.register).toHaveBeenCalledWith('test-plugin:my-format', opts);
+  });
+
+  test('formats.registerExportFormat is a no-op when no formatRegistry is injected', () => {
+    const noRegistryContext = new PluginContext({ ...mockDeps, formatRegistry: undefined });
+    expect(() =>
+      noRegistryContext.formats.registerExportFormat('x', { handler: jest.fn() })
+    ).not.toThrow();
+  });
 });

tests/plugin-registry.test.js

@@ -1,6 +1,7 @@
 const { PluginRegistry } = require('../src/plugins/plugin-registry');
 const { PluginAPI } = require('../src/plugins/plugin-api');
 const { EventBus } = require('../src/plugins/event-bus');
+const { FormatRegistry } = require('../src/plugins/format-registry');
 
 class TestPlugin extends PluginAPI {
   init(context) {
@@ -153,4 +154,40 @@ describe('PluginRegistry', () => {
     registry.getPlugin('test').instance.ctx.exports.registerPreHook(handler);
     expect(registry.exportHooks.preHooks).toContain(handler);
   });
+
+  test('a plugin calling context.formats.registerExportFormat populates the injected FormatRegistry with a namespaced entry', () => {
+    const formatRegistry = new FormatRegistry();
+    const registryWithFormats = new PluginRegistry({ ...mockDeps, formatRegistry });
+
+    class ExportingPlugin extends PluginAPI {
+      init(context) {
+        context.formats.registerExportFormat('sprint-summary', {
+          label: 'Writing Studio Summary (.txt)',
+          extension: 'txt',
+          handler: async () => {},
+        });
+      }
+    }
+
+    registryWithFormats.register({
+      id: 'writing-studio',
+      name: 'Writing Studio',
+      version: '1.0.0',
+      description: 'desc',
+      manifest: {},
+      PluginClass: ExportingPlugin,
+      dir: '/tmp/test',
+    });
+
+    const entry = formatRegistry.get('writing-studio:sprint-summary');
+    expect(entry).toBeDefined();
+    expect(entry.label).toBe('Writing Studio Summary (.txt)');
+    expect(entry.extension).toBe('txt');
+    expect(typeof entry.handler).toBe('function');
+
+    const all = formatRegistry.getAll();
+    expect(all).toContainEqual(
+      expect.objectContaining({ id: 'writing-studio:sprint-summary', extension: 'txt' })
+    );
+  });
 });