@@ -1,5 +1,6 @@
 
 * Release history
+- Feat: Add an Emacs MCP server with built-in tools and agent integration for Codex CLI and GitHub Copilot CLI
 
 ** Main branch change
 
 
@@ -166,6 +166,92 @@ The generated prompt will include the function/region scope, visible file list,
   - [[https://github.com/crystaldba/postgres-mcp][Postgresql MCP]] / Sqlite MCP
   - [[https://github.com/docker/mcp-gateway][Docker]] / [[https://github.com/containers/kubernetes-mcp-server][Kubernetes]] MCP
 
+**** Built-in Emacs MCP Tools
+
+AI Code includes an Emacs MCP server with these built-in tools:
+- =project_info=
+- =imenu_list_symbols=
+- =xref_find_references=
+- =treesit_info=
+
+***** Use It with an AI CLI
+
+Set the backend to =codex= or =github-copilot-cli= and start a session with =C-c a a=. AI Code will:
+- start a local Emacs MCP HTTP server
+- register the current project/buffer as the MCP session context
+- inject a session-scoped MCP config into that agent session automatically
+
+Today this auto-wiring is enabled for =codex= and =github-copilot-cli=. The adapter layer is designed so other backends can be added later.
+
+If you disabled it before, enable it again with:
+
+#+begin_src emacs-lisp
+(setq ai-code-mcp-agent-enabled-backends '(codex github-copilot-cli))
+#+end_src
+
+***** Make Sure It Works
+
+1. Start =codex= or =github-copilot-cli= with =C-c a a= from the file or project you want to work on.
+2. Switch to the agent buffer and run =M-x ai-code-mcp-agent-show-buffer-status=.
+
+If it shows =:backend=, =:session-id=, and a local =:server-url=, then Emacs has attached MCP to this session.
+
+3. Then ask the agent to use one of the Emacs tools, for example:
+- use =project_info= and tell me the current project info
+- use =imenu_list_symbols= for the current file
+
+The status command only proves the Emacs side is wired.
+The real proof is that the started agent returns your current project path, buffer context, or current-file symbols from those tools.
+
+***** Add New MCP function
+
+1. Define an Emacs Lisp function.
+
+#+begin_src emacs-lisp
+(defun ai-code-mcp-current-buffer-name ()
+  "Return the current buffer name for the active MCP session."
+  (buffer-name (current-buffer)))
+#+end_src
+
+2. Register it as an MCP tool before you start the AI agent session:
+
+#+begin_src emacs-lisp
+(require 'ai-code-mcp-server)
+
+(ai-code-mcp-make-tool
+ :function #'ai-code-mcp-current-buffer-name
+ :name "current_buffer_name"
+ :description "Return the current Emacs buffer name."
+ :args nil)
+#+end_src
+
+3. Start =codex= or =github-copilot-cli= with =C-c a a=.
+If the agent session is already running, restart it after registering the new tool.
+
+4. Ask the agent to use the tool, for example:
+- use =current_buffer_name= and tell me the current Emacs buffer name
+
+5. If you want to verify from Emacs first, run:
+
+#+begin_src emacs-lisp
+(ai-code-mcp-dispatch "tools/list")
+#+end_src
+
+If =current_buffer_name= appears in the tool list, Emacs has registered it.
+If the started agent can call it and returns the expected buffer name, the tool is available inside the AI coding agent.
+
+***** Use the MCP Core Directly from Elisp
+
+If you want to use the MCP core without an AI CLI, you can still call it directly:
+
+#+begin_src emacs-lisp
+(require 'ai-code-mcp-server)
+(ai-code-mcp-builtins-setup)
+(ai-code-mcp-dispatch "tools/list")
+#+end_src
+
+To expose your own Emacs function as a tool, use =ai-code-mcp-make-tool=.
+
 - [[https://martinfowler.com/articles/exploring-gen-ai/context-engineering-coding-agents.html][Context Engineering for Coding Agents]], recommended by Martin Fowler.
 
 *** Harness Engineering Practice
 
@@ -754,7 +754,8 @@ any error output left behind by the CLI."
 (defun ai-code-backends-infra--toggle-or-create-session (working-dir buffer-name process-table command
                                                                      &optional escape-fn cleanup-fn
                                                                      instance-name prefix force-prompt
-                                                                     env-vars multiline-input-sequence)
+                                                                     env-vars multiline-input-sequence
+                                                                     post-start-fn)
   "Toggle or create a terminal session.
 WORKING-DIR is the directory for the session.
 BUFFER-NAME is the terminal buffer name.
@@ -768,7 +769,9 @@ When FORCE-PROMPT is non-nil, always prompt for a new instance name.
 ENV-VARS is a list of additional environment variable strings (e.g., \"VAR=value\")
 passed to the terminal session on creation.
 MULTILINE-INPUT-SEQUENCE configures `S-<return>' and `C-<return>' to send
-that sequence inside the session buffer."
+that sequence inside the session buffer.
+POST-START-FN is called with (BUFFER PROCESS INSTANCE-NAME) after a new
+session starts successfully."
   (setq process-table (or process-table ai-code-backends-infra--processes))
   (ai-code-backends-infra--cleanup-dead-processes process-table)
   (let* ((existing-buffers (and prefix
@@ -829,8 +832,10 @@ that sequence inside the session buffer."
                   event)
                  (when cleanup-fn
                    (funcall cleanup-fn))))
-               (ai-code-backends-infra--configure-session-buffer
-                new-buffer escape-fn multiline-input-sequence)
+              (ai-code-backends-infra--configure-session-buffer
+               new-buffer escape-fn multiline-input-sequence)
+               (when post-start-fn
+                 (funcall post-start-fn new-buffer process resolved-instance))
                (with-current-buffer new-buffer
                  (add-hook 'kill-buffer-hook
                            (lambda ()
 
@@ -12,6 +12,7 @@
 
 (require 'ai-code-backends)
 (require 'ai-code-backends-infra)
+(require 'ai-code-mcp-agent)
 
 (defgroup ai-code-codex-cli nil
   "Codex CLI integration via `ai-code-backends-infra'."
@@ -46,17 +47,24 @@ With prefix ARG, prompt for CLI args using
                     ai-code-codex-cli-program-switches
                     arg
                     "Codex"))
-         (command (plist-get resolved :command)))
+         (command (plist-get resolved :command))
+         (mcp-launch (ai-code-mcp-agent-prepare-launch 'codex working-dir command))
+         (launch-command (or (plist-get mcp-launch :command) command))
+         (cleanup-fn (plist-get mcp-launch :cleanup-fn))
+         (post-start-fn (plist-get mcp-launch :post-start-fn)))
     (ai-code-backends-infra--toggle-or-create-session
      working-dir
      nil
      ai-code-codex-cli--processes
-     command
+     launch-command
      #'ai-code-codex-cli-send-escape
-     nil
+     cleanup-fn
      nil
      ai-code-codex-cli--session-prefix
-     nil)))
+     nil
+     nil
+     nil
+     post-start-fn)))
 
 ;;;###autoload
 (defun ai-code-codex-cli-switch-to-buffer (&optional force-prompt)
 
@@ -12,6 +12,7 @@
 
 (require 'ai-code-backends)
 (require 'ai-code-backends-infra)
+(require 'ai-code-mcp-agent)
 
 (defgroup ai-code-github-copilot-cli nil
   "GitHub Copilot CLI integration via `ai-code-backends-infra'."
@@ -61,19 +62,26 @@ With prefix ARG, prompt for CLI args using
                     ai-code-github-copilot-cli-program-switches
                     arg
                     "Copilot"))
-         (command (plist-get resolved :command)))
+         (command (plist-get resolved :command))
+         (mcp-launch (ai-code-mcp-agent-prepare-launch 'github-copilot-cli
+                                                       working-dir
+                                                       command))
+         (launch-command (or (plist-get mcp-launch :command) command))
+         (cleanup-fn (plist-get mcp-launch :cleanup-fn))
+         (post-start-fn (plist-get mcp-launch :post-start-fn)))
     (ai-code-backends-infra--toggle-or-create-session
      working-dir
      nil
      ai-code-github-copilot-cli--processes
-     command
+     launch-command
      #'ai-code-github-copilot-cli-send-escape
-     nil
+     cleanup-fn
      nil
      ai-code-github-copilot-cli--session-prefix
      nil
      ai-code-github-copilot-cli-extra-env-vars
-     ai-code-github-copilot-cli-multiline-input-sequence)))
+     ai-code-github-copilot-cli-multiline-input-sequence
+     post-start-fn)))
 
 ;;;###autoload
 (defun ai-code-github-copilot-cli-switch-to-buffer (&optional force-prompt)
 
@@ -0,0 +1,128 @@
+;;; ai-code-mcp-agent.el --- Agent adapters for ai-code MCP tools -*- lexical-binding: t; -*-
+
+;; Author: Kang Tu <tninja@gmail.com>
+;; SPDX-License-Identifier: Apache-2.0
+
+;;; Commentary:
+;; Backend-facing helpers that expose Emacs MCP tools to AI agents.
+
+;;; Code:
+
+(require 'json)
+
+(require 'ai-code-mcp-http-server)
+(require 'ai-code-mcp-server)
+
+(defgroup ai-code-mcp-agent nil
+  "Agent adapters for AI Code MCP tools."
+  :group 'tools
+  :prefix "ai-code-mcp-agent-")
+
+(defcustom ai-code-mcp-agent-enabled-backends '(codex github-copilot-cli)
+  "Backends that should receive automatic Emacs MCP integration."
+  :type '(repeat symbol)
+  :group 'ai-code-mcp-agent)
+
+(defconst ai-code-mcp-agent--server-name "emacs_tools"
+  "Server name used in backend MCP config overrides.")
+
+(defconst ai-code-mcp-agent--status-buffer-name "*AI Code MCP Status*"
+  "Buffer name used to display MCP status to users.")
+
+(defvar-local ai-code-mcp-agent--backend nil
+  "Backend symbol attached to the current agent buffer.")
+
+(defvar-local ai-code-mcp-agent--session-id nil
+  "Session id attached to the current agent buffer.")
+
+(defvar-local ai-code-mcp-agent--server-url nil
+  "MCP server URL attached to the current agent buffer.")
+
+(defun ai-code-mcp-agent-buffer-status (&optional buffer)
+  "Return MCP status for BUFFER or the current buffer."
+  (with-current-buffer (or buffer (current-buffer))
+    (when ai-code-mcp-agent--session-id
+      (list :backend ai-code-mcp-agent--backend
+            :session-id ai-code-mcp-agent--session-id
+            :server-url ai-code-mcp-agent--server-url))))
+
+;;;###autoload
+(defun ai-code-mcp-agent-show-buffer-status (&optional buffer)
+  "Display MCP status for BUFFER or the current buffer."
+  (interactive)
+  (let ((status (ai-code-mcp-agent-buffer-status buffer)))
+    (if (not status)
+        (message "No MCP session is attached to the current buffer.")
+      (with-help-window ai-code-mcp-agent--status-buffer-name
+        (princ (ai-code-mcp-agent--format-status status))))
+    status))
+
+(defun ai-code-mcp-agent--format-status (status)
+  "Return a display string for MCP STATUS."
+  (concat
+   "AI Code MCP Status\n\n"
+   (format "Backend: %s\n" (plist-get status :backend))
+   (format "Session ID: %s\n" (plist-get status :session-id))
+   (format "Server URL: %s\n" (plist-get status :server-url))))
+
+(defun ai-code-mcp-agent-prepare-launch (backend working-dir command)
+  "Return MCP launch metadata for BACKEND, WORKING-DIR, and COMMAND."
+  (when (memq backend ai-code-mcp-agent-enabled-backends)
+    (ai-code-mcp-builtins-setup)
+    (let* ((port (ai-code-mcp-http-server-ensure))
+           (session-id (ai-code-mcp-agent--make-session-id backend))
+           (url (ai-code-mcp-agent--make-server-url port session-id)))
+      (list :command (ai-code-mcp-agent--inject-command backend command url)
+            :cleanup-fn (lambda ()
+                          (ai-code-mcp-unregister-session session-id))
+            :post-start-fn (lambda (buffer _process _instance-name)
+                             (ai-code-mcp-agent--record-buffer-session
+                              buffer backend session-id working-dir url))))))
+
+(defun ai-code-mcp-agent--make-session-id (backend)
+  "Create a fresh session id for BACKEND."
+  (format "%s-%s-%d"
+          (symbol-name backend)
+          (format-time-string "%Y%m%d%H%M%S")
+          (random 1000000)))
+
+(defun ai-code-mcp-agent--make-server-url (port session-id)
+  "Build an MCP server URL from PORT and SESSION-ID."
+  (format "http://127.0.0.1:%d/mcp/%s" port session-id))
+
+(defun ai-code-mcp-agent--record-buffer-session (buffer backend session-id working-dir url)
+  "Record session metadata for BUFFER."
+  (ai-code-mcp-register-session session-id working-dir buffer)
+  (with-current-buffer buffer
+    (setq-local ai-code-mcp-agent--backend backend
+                ai-code-mcp-agent--session-id session-id
+                ai-code-mcp-agent--server-url url)))
+
+(defun ai-code-mcp-agent--inject-command (backend command url)
+  "Inject backend-specific MCP config into COMMAND for URL."
+  (pcase backend
+    ('codex
+     (concat command
+             " -c "
+             (shell-quote-argument
+              (format "mcp_servers.%s={ url = %s }"
+                      ai-code-mcp-agent--server-name
+                      (json-encode url)))))
+    ('github-copilot-cli
+     (concat command
+             " --additional-mcp-config "
+             (shell-quote-argument
+              (ai-code-mcp-agent--copilot-config-json url))))
+    (_ command)))
+
+(defun ai-code-mcp-agent--copilot-config-json (url)
+  "Return a Copilot CLI MCP config JSON string for URL."
+  (json-encode
+   `((mcpServers
+      . ((,ai-code-mcp-agent--server-name
+          . ((type . "http")
+             (url . ,url))))))))
+
+(provide 'ai-code-mcp-agent)
+
+;;; ai-code-mcp-agent.el ends here
Original file line number	Diff line number	Diff line change
`@@ -1,5 +1,6 @@`
`1`	`1`
`2`	`2`	`* Release history`
	`3`	`+- Feat: Add an Emacs MCP server with built-in tools and agent integration for Codex CLI and GitHub Copilot CLI`
`3`	`4`
`4`	`5`	`** Main branch change`
`5`	`6`