Add WebDriver BiDi support for real-time browser diagnostics

AGENTS.md

@@ -37,12 +37,14 @@ mcp-selenium/
     ├── browser.test.mjs   ← start_browser, close_session, take_screenshot, multi-session
     ├── navigation.test.mjs ← navigate, all 6 locator strategies
     ├── interactions.test.mjs ← click, send_keys, get_element_text, hover, double_click, right_click, press_key, drag_and_drop, upload_file
+    ├── bidi.test.mjs      ← BiDi enablement, console/error/network capture, session isolation
     └── fixtures/           ← HTML files loaded via file:// URLs
         ├── locators.html
         ├── interactions.html
         ├── mouse-actions.html
         ├── drag-drop.html
-        └── upload.html
+        ├── upload.html
+        └── bidi.html
 ```
 
 ### Key Files in Detail
@@ -82,20 +84,37 @@ All browser state is held in a module-level `state` object:
 ```js
 const state = {
     drivers: new Map(),    // sessionId → WebDriver instance
-    currentSession: null   // string | null — the active session ID
+    currentSession: null,  // string | null — the active session ID
+    bidi: new Map()        // sessionId → { available, consoleLogs, pageErrors, networkLogs }
 };
 ```
 
 - **Session IDs** are formatted as `{browser}_{Date.now()}` (e.g., `chrome_1708531200000`)
 - Only one session is "current" at a time (set by `start_browser`, cleared by `close_session`)
 - Multiple sessions can exist in the `drivers` Map, but tools always operate on `currentSession`
+- **BiDi state** is a single Map of per-session objects — cleanup is one `state.bidi.delete(sessionId)` call
 
 ### Helper Functions
 
 | Function | Purpose |
 |----------|---------|
 | `getDriver()` | Returns the WebDriver for `state.currentSession`. Throws if no active session. |
 | `getLocator(by, value)` | Converts a locator strategy string (`"id"`, `"css"`, `"xpath"`, `"name"`, `"tag"`, `"class"`) to a Selenium `By` object. |
+| `newBidiState()` | Returns a fresh `{ available, consoleLogs, pageErrors, networkLogs }` object for a new session. |
+| `setupBidi(driver, sessionId)` | Wires up BiDi event listeners (console, JS errors, network) for a session. Called from `start_browser`. |
+| `registerBidiTool(name, description, logKey, emptyMessage, unavailableMessage)` | Factory that registers a diagnostic tool. All three BiDi tools (`get_console_logs`, `get_page_errors`, `get_network_logs`) use this — don't copy-paste a new handler, call this instead. |
+
+### Diagnostics (WebDriver BiDi)
+
+The server automatically enables [WebDriver BiDi](https://w3c.github.io/webdriver-bidi/) when starting a browser session. BiDi provides real-time, passive capture of browser diagnostics — console messages, JavaScript errors, and network activity are collected in the background without any extra configuration.
+
+This is especially useful for AI agents: when something goes wrong on a page, the agent can check `get_console_logs` and `get_page_errors` to understand *why*, rather than relying solely on screenshots.
+
+- **Automatic**: BiDi is enabled by default when the browser supports it
+- **Graceful fallback**: If the browser or driver doesn't support BiDi, the session starts normally and the diagnostic tools return a helpful message
+- **No performance impact**: Logs are passively captured via event listeners — no polling or extra requests
+- **Per-session**: Each browser session has its own log buffers, cleaned up automatically on session close
+- **BiDi modules are dynamically imported** at the top of `server.js` — if the selenium-webdriver version doesn't include them, `LogInspector` and `Network` are set to `null` and all BiDi code is skipped
 
 ### Cleanup
 
@@ -232,6 +251,7 @@ Tests talk to the real MCP server over stdio using JSON-RPC 2.0. No mocking.
 | `browser.test.mjs` | start_browser, close_session, take_screenshot, multi-session |
 | `navigation.test.mjs` | navigate, all 6 locator strategies (id, css, xpath, name, tag, class) |
 | `interactions.test.mjs` | click, send_keys, get_element_text, hover, double_click, right_click, press_key, drag_and_drop, upload_file |
+| `bidi.test.mjs` | BiDi enablement, console log capture, page error capture, network log capture, session isolation |
 
 ### When Adding a New Tool
 

README.md

@@ -23,6 +23,10 @@ A Model Context Protocol (MCP) server implementation for Selenium WebDriver, ena
 - Upload files
 - Support for headless mode
 - Manage browser cookies (add, get, delete)
+- **Real-time diagnostics** via WebDriver BiDi:
+  - Console log capture (info, warn, error)
+  - JavaScript error detection with stack traces
+  - Network request monitoring (successes and failures)
 
 ## Supported Browsers
 
@@ -791,6 +795,54 @@ Deletes cookies from the current browser session. Deletes a specific cookie by n
 }
 ```
 
+### get_console_logs
+Retrieves captured browser console messages (log, warn, error, etc.). Console logs are automatically captured in the background via WebDriver BiDi when the browser supports it — no configuration needed.
+
+**Parameters:**
+| Parameter | Type | Required | Description |
+|-----------|------|----------|-------------|
+| clear | boolean | No | Clear the captured logs after retrieving them (default: false) |
+
+**Example:**
+```json
+{
+  "tool": "get_console_logs",
+  "parameters": {}
+}
+```
+
+### get_page_errors
+Retrieves captured JavaScript errors and uncaught exceptions with full stack traces. Errors are automatically captured in the background via WebDriver BiDi.
+
+**Parameters:**
+| Parameter | Type | Required | Description |
+|-----------|------|----------|-------------|
+| clear | boolean | No | Clear the captured errors after retrieving them (default: false) |
+
+**Example:**
+```json
+{
+  "tool": "get_page_errors",
+  "parameters": {}
+}
+```
+
+### get_network_logs
+Retrieves captured network activity including successful responses and failed requests. Network logs are automatically captured in the background via WebDriver BiDi.
+
+**Parameters:**
+| Parameter | Type | Required | Description |
+|-----------|------|----------|-------------|
+| clear | boolean | No | Clear the captured logs after retrieving them (default: false) |
+
+**Example:**
+```json
+{
+  "tool": "get_network_logs",
+  "parameters": {}
+}
+```
+
 ## License
 
 MIT

src/lib/server.js

@@ -10,6 +10,18 @@ import { Options as FirefoxOptions } from 'selenium-webdriver/firefox.js';
 import { Options as EdgeOptions } from 'selenium-webdriver/edge.js';
 import { Options as SafariOptions } from 'selenium-webdriver/safari.js';
 
+// BiDi imports — loaded dynamically to avoid hard failures if not available
+let LogInspector, Network;
+try {
+    LogInspector = (await import('selenium-webdriver/bidi/logInspector.js')).default;
+    const networkModule = await import('selenium-webdriver/bidi/network.js');
+    Network = networkModule.Network;
+} catch (_) {
+    // BiDi modules not available in this selenium-webdriver version
+    LogInspector = null;
+    Network = null;
+}
+
 
 // Create an MCP server
 const server = new McpServer({
@@ -20,7 +32,8 @@ const server = new McpServer({
 // Server state
 const state = {
     drivers: new Map(),
-    currentSession: null
+    currentSession: null,
+    bidi: new Map()
 };
 
 // Helper functions
@@ -44,6 +57,80 @@ const getLocator = (by, value) => {
     }
 };
 
+// BiDi helpers
+const newBidiState = () => ({
+    available: false,
+    consoleLogs: [],
+    pageErrors: [],
+    networkLogs: []
+});
+
+async function setupBidi(driver, sessionId) {
+    const bidi = newBidiState();
+
+    const logInspector = await LogInspector(driver);
+    await logInspector.onConsoleEntry((entry) => {
+        try {
+            bidi.consoleLogs.push({
+                level: entry.level, text: entry.text, timestamp: entry.timestamp,
+                type: entry.type, method: entry.method, args: entry.args
+            });
+        } catch (_) { /* ignore malformed entry */ }
+    });
+    await logInspector.onJavascriptLog((entry) => {
+        try {
+            bidi.pageErrors.push({
+                level: entry.level, text: entry.text, timestamp: entry.timestamp,
+                type: entry.type, stackTrace: entry.stackTrace
+            });
+        } catch (_) { /* ignore malformed entry */ }
+    });
+
+    const network = await Network(driver);
+    await network.responseCompleted((event) => {
+        try {
+            bidi.networkLogs.push({
+                type: 'response', url: event.request?.url, status: event.response?.status,
+                method: event.request?.method, mimeType: event.response?.mimeType, timestamp: Date.now()
+            });
+        } catch (_) { /* ignore malformed event */ }
+    });
+    await network.fetchError((event) => {
+        try {
+            bidi.networkLogs.push({
+                type: 'error', url: event.request?.url, method: event.request?.method,
+                errorText: event.errorText, timestamp: Date.now()
+            });
+        } catch (_) { /* ignore malformed event */ }
+    });
+
+    bidi.available = true;
+    state.bidi.set(sessionId, bidi);
+}
+
+function registerBidiTool(name, description, logKey, emptyMessage, unavailableMessage) {
+    server.tool(
+        name,
+        description,
+        { clear: z.boolean().optional().describe("Clear after returning (default: false)") },
+        async ({ clear = false }) => {
+            try {
+                getDriver();
+                const bidi = state.bidi.get(state.currentSession);
+                if (!bidi?.available) {
+                    return { content: [{ type: 'text', text: unavailableMessage }] };
+                }
+                const logs = bidi[logKey];
+                const result = logs.length === 0 ? emptyMessage : JSON.stringify(logs, null, 2);
+                if (clear) bidi[logKey] = [];
+                return { content: [{ type: 'text', text: result }] };
+            } catch (e) {
+                return { content: [{ type: 'text', text: `Error: ${e.message}` }], isError: true };
+            }
+        }
+    );
+}
+
 // Common schemas
 const browserOptionsSchema = z.object({
     headless: z.boolean().optional().describe("Run browser in headless mode"),
@@ -69,6 +156,12 @@ server.tool(
             let builder = new Builder();
             let driver;
             let warnings = [];
+
+            // Enable BiDi websocket if the modules are available
+            if (LogInspector && Network) {
+                builder = builder.withCapabilities({ 'webSocketUrl': true, 'unhandledPromptBehavior': 'ignore' });
+            }
+
             switch (browser) {
                 case 'chrome': {
                     const chromeOptions = new ChromeOptions();
@@ -134,7 +227,19 @@ server.tool(
             state.drivers.set(sessionId, driver);
             state.currentSession = sessionId;
 
+            // Attempt to enable BiDi for real-time log capture
+            if (LogInspector && Network) {
+                try {
+                    await setupBidi(driver, sessionId);
+                } catch (_) {
+                    // BiDi not supported by this browser/driver — continue without it
+                }
+            }
+
             let message = `Browser started with session_id: ${sessionId}`;
+            if (state.bidi.get(sessionId)?.available) {
+                message += ' (BiDi enabled: console logs, JS errors, and network activity are being captured)';
+            }
             if (warnings.length > 0) {
                 message += `\nWarnings: ${warnings.join(' ')}`;
             }
@@ -473,9 +578,10 @@ server.tool(
     async () => {
         try {
             const driver = getDriver();
-            await driver.quit();
-            state.drivers.delete(state.currentSession);
             const sessionId = state.currentSession;
+            await driver.quit();
+            state.drivers.delete(sessionId);
+            state.bidi.delete(sessionId);
             state.currentSession = null;
             return {
                 content: [{ type: 'text', text: `Browser session ${sessionId} closed` }]
@@ -681,6 +787,7 @@ server.tool(
                 console.error(`Error quitting driver for session ${sessionId}:`, quitError);
             }
             state.drivers.delete(sessionId);
+            state.bidi.delete(sessionId);
             state.currentSession = null;
             return {
                 content: [{ type: 'text', text: 'Last window closed. Session ended.' }]
@@ -957,6 +1064,31 @@ server.tool(
     }
 );
 
+// BiDi Diagnostic Tools
+registerBidiTool(
+    'get_console_logs',
+    'returns browser console messages (log, warn, info, debug) captured via WebDriver BiDi. Useful for debugging page behavior, seeing application output, and catching warnings.',
+    'consoleLogs',
+    'No console logs captured',
+    'Console log capture is not available (BiDi not supported by this browser/driver)'
+);
+
+registerBidiTool(
+    'get_page_errors',
+    'returns JavaScript errors and exceptions captured via WebDriver BiDi. Includes stack traces when available. Essential for diagnosing why a page is broken or a feature isn\'t working.',
+    'pageErrors',
+    'No page errors captured',
+    'Page error capture is not available (BiDi not supported by this browser/driver)'
+);
+
+registerBidiTool(
+    'get_network_logs',
+    'returns network activity (completed responses and failed requests) captured via WebDriver BiDi. Shows HTTP status codes, URLs, methods, and error details. Useful for diagnosing failed API calls and broken resources.',
+    'networkLogs',
+    'No network activity captured',
+    'Network log capture is not available (BiDi not supported by this browser/driver)'
+);
+
 // Resources
 server.resource(
     "browser-status",
@@ -986,6 +1118,7 @@ async function cleanup() {
         }
     }
     state.drivers.clear();
+    state.bidi.clear();
     state.currentSession = null;
     process.exit(0);
 }