diff --git a/.gitignore b/.gitignore
index 411fe4011..7831aa60d 100644
--- a/.gitignore
+++ b/.gitignore
@@ -14,6 +14,7 @@
 .vscode
 !.vscode/launch.json
 !.vscode/tasks.json
+!browser-ext/lib
 
 # output
 node_modules
@@ -27,4 +28,4 @@ TestResults
 TestLogs
 .DS_Store
 .mono
-**/*.DotSettings.user
\ No newline at end of file
+**/*.DotSettings.user
diff --git a/browser-ext/lib/dap-protocol.js b/browser-ext/lib/dap-protocol.js
new file mode 100644
index 000000000..9f75e320c
--- /dev/null
+++ b/browser-ext/lib/dap-protocol.js
@@ -0,0 +1,226 @@
+/**
+ * DAP Protocol Helpers
+ *
+ * Type definitions and utilities for the Debug Adapter Protocol.
+ * Used by both content and background scripts.
+ */
+
+// DAP Request Commands
+const DapCommands = {
+  // Lifecycle
+  INITIALIZE: 'initialize',
+  ATTACH: 'attach',
+  CONFIGURATION_DONE: 'configurationDone',
+  DISCONNECT: 'disconnect',
+
+  // Execution Control
+  CONTINUE: 'continue',
+  NEXT: 'next',
+  STEP_IN: 'stepIn',
+  STEP_OUT: 'stepOut',
+  PAUSE: 'pause',
+  TERMINATE: 'terminate',
+
+  // Reverse Execution
+  STEP_BACK: 'stepBack',
+  REVERSE_CONTINUE: 'reverseContinue',
+
+  // Information
+  THREADS: 'threads',
+  STACK_TRACE: 'stackTrace',
+  SCOPES: 'scopes',
+  VARIABLES: 'variables',
+  SOURCE: 'source',
+
+  // Evaluation
+  EVALUATE: 'evaluate',
+  SET_VARIABLE: 'setVariable',
+
+  // Breakpoints
+  SET_BREAKPOINTS: 'setBreakpoints',
+  SET_FUNCTION_BREAKPOINTS: 'setFunctionBreakpoints',
+  SET_EXCEPTION_BREAKPOINTS: 'setExceptionBreakpoints',
+};
+
+// DAP Event Types
+const DapEvents = {
+  // Lifecycle
+  INITIALIZED: 'initialized',
+  TERMINATED: 'terminated',
+  EXITED: 'exited',
+
+  // Execution
+  STOPPED: 'stopped',
+  CONTINUED: 'continued',
+
+  // Output
+  OUTPUT: 'output',
+
+  // Other
+  THREAD: 'thread',
+  BREAKPOINT: 'breakpoint',
+  MODULE: 'module',
+  LOADED_SOURCE: 'loadedSource',
+  PROCESS: 'process',
+  CAPABILITIES: 'capabilities',
+  PROGRESS_START: 'progressStart',
+  PROGRESS_UPDATE: 'progressUpdate',
+  PROGRESS_END: 'progressEnd',
+  INVALIDATED: 'invalidated',
+  MEMORY: 'memory',
+};
+
+// Stopped Event Reasons
+const StoppedReasons = {
+  STEP: 'step',
+  BREAKPOINT: 'breakpoint',
+  EXCEPTION: 'exception',
+  PAUSE: 'pause',
+  ENTRY: 'entry',
+  GOTO: 'goto',
+  FUNCTION_BREAKPOINT: 'function breakpoint',
+  DATA_BREAKPOINT: 'data breakpoint',
+  INSTRUCTION_BREAKPOINT: 'instruction breakpoint',
+};
+
+// Output Categories
+const OutputCategories = {
+  CONSOLE: 'console',
+  IMPORTANT: 'important',
+  STDOUT: 'stdout',
+  STDERR: 'stderr',
+  TELEMETRY: 'telemetry',
+};
+
+// Evaluate Contexts
+const EvaluateContexts = {
+  WATCH: 'watch',
+  REPL: 'repl',
+  HOVER: 'hover',
+  CLIPBOARD: 'clipboard',
+  VARIABLES: 'variables',
+};
+
+/**
+ * Create a DAP request message
+ *
+ * @param {number} seq - Sequence number
+ * @param {string} command - DAP command name
+ * @param {object} args - Command arguments
+ * @returns {object} DAP request message
+ */
+function createDapRequest(seq, command, args = {}) {
+  return {
+    seq,
+    type: 'request',
+    command,
+    arguments: args,
+  };
+}
+
+/**
+ * Create a DAP response message
+ *
+ * @param {number} seq - Sequence number
+ * @param {number} requestSeq - Original request sequence number
+ * @param {string} command - DAP command name
+ * @param {boolean} success - Whether request succeeded
+ * @param {object} body - Response body
+ * @param {string} message - Error message (if success is false)
+ * @returns {object} DAP response message
+ */
+function createDapResponse(seq, requestSeq, command, success, body = {}, message = '') {
+  return {
+    seq,
+    type: 'response',
+    request_seq: requestSeq,
+    command,
+    success,
+    body,
+    message: success ? undefined : message,
+  };
+}
+
+/**
+ * Create a DAP event message
+ *
+ * @param {number} seq - Sequence number
+ * @param {string} event - Event type
+ * @param {object} body - Event body
+ * @returns {object} DAP event message
+ */
+function createDapEvent(seq, event, body = {}) {
+  return {
+    seq,
+    type: 'event',
+    event,
+    body,
+  };
+}
+
+/**
+ * Parse a DAP message
+ *
+ * @param {string|object} message - JSON string or parsed object
+ * @returns {object} Parsed message with helper properties
+ */
+function parseDapMessage(message) {
+  const msg = typeof message === 'string' ? JSON.parse(message) : message;
+
+  return {
+    raw: msg,
+    isRequest: msg.type === 'request',
+    isResponse: msg.type === 'response',
+    isEvent: msg.type === 'event',
+    seq: msg.seq,
+    requestSeq: msg.request_seq,
+    command: msg.command,
+    event: msg.event,
+    success: msg.success,
+    body: msg.body || {},
+    message: msg.message,
+  };
+}
+
+/**
+ * Check if a message indicates a capability
+ *
+ * @param {object} capabilities - Capabilities object from initialize response
+ * @param {string} name - Capability name
+ * @returns {boolean}
+ */
+function hasCapability(capabilities, name) {
+  return capabilities && capabilities[name] === true;
+}
+
+// Export for use in other modules
+if (typeof module !== 'undefined' && module.exports) {
+  module.exports = {
+    DapCommands,
+    DapEvents,
+    StoppedReasons,
+    OutputCategories,
+    EvaluateContexts,
+    createDapRequest,
+    createDapResponse,
+    createDapEvent,
+    parseDapMessage,
+    hasCapability,
+  };
+}
+
+// Make available globally for browser scripts
+if (typeof window !== 'undefined') {
+  window.DapProtocol = {
+    DapCommands,
+    DapEvents,
+    StoppedReasons,
+    OutputCategories,
+    EvaluateContexts,
+    createDapRequest,
+    createDapResponse,
+    createDapEvent,
+    parseDapMessage,
+    hasCapability,
+  };
+}