Support resuming AI sessions from a selected UUID

ai-code-backends-infra.el

@@ -17,6 +17,7 @@
 
 (require 'cl-lib)
 (require 'project)
+(require 'subr-x)
 (require 'ai-code-session-link)
 ;; Terminal-specific implementations live in dedicated modules so this
 ;; file can stay focused on shared session orchestration.
@@ -145,6 +146,22 @@ being sent for the response completion.")
 (defvar ai-code-cli-args-history nil
   "History list for CLI args prompts.")
 
+(defconst ai-code-backends-infra--uuid-regexp
+  "[[:xdigit:]]\\{8\\}-[[:xdigit:]]\\{4\\}-[[:xdigit:]]\\{4\\}-[[:xdigit:]]\\{4\\}-[[:xdigit:]]\\{12\\}"
+  "Regexp matching the general UUID 8-4-4-4-12 text structure.
+This validates the textual shape, but not UUID version or variant bits.")
+
+(defun ai-code-backends-infra--selected-session-id ()
+  "Return the active region text when it contains a UUID session id."
+  (when (use-region-p)
+    (let ((candidate
+           (string-trim
+            (buffer-substring-no-properties (region-beginning) (region-end)))))
+      (when (string-match-p
+             (concat "\\`" ai-code-backends-infra--uuid-regexp "\\'")
+             candidate)
+        candidate))))
+
 (defcustom ai-code-backends-infra-idle-delay 5.0
   "Delay in seconds of inactivity before considering response complete.
 After this period of terminal inactivity, a notification may be sent
@@ -854,12 +871,27 @@ If FORCE-PROMPT is nil and there are no existing instances, return \"default\"."
 (defun ai-code-backends-infra--resolve-start-command (program switches arg &optional prompt-label)
   "Build command string for PROGRAM and SWITCHES.
 When ARG is non-nil, prompt for CLI args using SWITCHES as default input.
-PROMPT-LABEL is used in the minibuffer prompt."
-  (let* ((default-args (mapconcat #'identity switches " "))
+PROMPT-LABEL is used in the minibuffer prompt.
+When resuming and the active region contains a UUID, prompt as though ARG
+were non-nil and append that UUID to the default CLI args."
+  (let* ((found-resume-switch
+          (cl-some (lambda (switch)
+                     (member switch '("resume" "--resume")))
+                   switches))
+         (selected-session-id
+          (and (null arg)
+               found-resume-switch
+               (ai-code-backends-infra--selected-session-id)))
+         (prompt-p (or arg selected-session-id))
+         (default-args (mapconcat #'identity
+                                   (append switches
+                                           (and selected-session-id
+                                                (list selected-session-id)))
+                                   " "))
          (prompt (format "%s args: " (or prompt-label "CLI")))
-         (prompt-args (when arg
-                        (read-string prompt default-args 'ai-code-cli-args-history)))
-         (resolved-args (if arg
+         (prompt-args (when prompt-p
+                           (read-string prompt default-args 'ai-code-cli-args-history)))
+         (resolved-args (if prompt-p
                             (split-string-shell-command prompt-args)
                           switches))
          (command (mapconcat #'identity

test/test_ai-code-backends-infra.el

@@ -21,6 +21,10 @@
 (defvar ghostel--copy-mode-active)
 (defvar ghostel--process)
 
+(defconst test-ai-code-backends-infra-valid-uuid
+  "123e4567-e89b-12d3-a456-426614174000"
+  "UUID fixture used by resume command resolution tests.")
+
 (ert-deftest test-ai-code-backends-infra-output-meaningful-p-noise ()
   "Ensure terminal noise is not considered meaningful output."
   (should-not (ai-code-backends-infra--output-meaningful-p nil))
@@ -63,6 +67,77 @@
     (should (re-search-forward
              "^(defcustom ai-code-backends-infra-eat-preserve-position\\_>" nil t))))
 
+(ert-deftest test-ai-code-backends-infra--resume-double-dash-prefills-uuid ()
+  "A selected UUID should make `--resume' prompt with that id appended."
+  (let ((uuid test-ai-code-backends-infra-valid-uuid)
+        seen-prompt
+        seen-initial
+        seen-history
+        result)
+    (with-temp-buffer
+      (transient-mark-mode 1)
+      (insert uuid)
+      (goto-char (point-min))
+      (set-mark (point))
+      (goto-char (point-max))
+      (activate-mark)
+      (cl-letf (((symbol-function 'read-string)
+                 (lambda (prompt &optional initial-input history &rest _args)
+                   (setq seen-prompt prompt
+                         seen-initial initial-input
+                         seen-history history)
+                   initial-input)))
+        (setq result
+              (ai-code-backends-infra--resolve-start-command
+               "claude" '("--resume") nil "Claude"))))
+    (should (equal seen-prompt "Claude args: "))
+    (should (equal seen-initial (format "--resume %s" uuid)))
+    (should (eq seen-history 'ai-code-cli-args-history))
+    (should (equal (plist-get result :args) `("--resume" ,uuid)))
+    (should (equal (plist-get result :command)
+                   (format "claude --resume %s" uuid)))))
+
+(ert-deftest test-ai-code-backends-infra--resume-subcommand-prefills-uuid ()
+  "A selected UUID should make `resume' prompt with that id appended."
+  (let ((uuid test-ai-code-backends-infra-valid-uuid)
+        seen-initial
+        result)
+    (with-temp-buffer
+      (transient-mark-mode 1)
+      (insert uuid)
+      (goto-char (point-min))
+      (set-mark (point))
+      (goto-char (point-max))
+      (activate-mark)
+      (cl-letf (((symbol-function 'read-string)
+                 (lambda (_prompt &optional initial-input _history &rest _args)
+                   (setq seen-initial initial-input)
+                   initial-input)))
+        (setq result
+              (ai-code-backends-infra--resolve-start-command
+               "codex" '("resume") nil "Codex"))))
+    (should (equal seen-initial (format "resume %s" uuid)))
+    (should (equal (plist-get result :args) `("resume" ,uuid)))
+    (should (equal (plist-get result :command)
+                   (format "codex resume %s" uuid)))))
+
+(ert-deftest test-ai-code-backends-infra--resume-ignores-non-uuid ()
+  "A non-UUID region should not trigger resume prompting."
+  (with-temp-buffer
+    (transient-mark-mode 1)
+    (insert "not-a-session-id")
+    (goto-char (point-min))
+    (set-mark (point))
+    (goto-char (point-max))
+    (activate-mark)
+    (cl-letf (((symbol-function 'read-string)
+               (lambda (&rest _args)
+                 (ert-fail "non-UUID selection should not prompt"))))
+      (let ((result (ai-code-backends-infra--resolve-start-command
+                     "claude" '("--resume") nil "Claude")))
+        (should (equal (plist-get result :args) '("--resume")))
+        (should (equal (plist-get result :command) "claude --resume"))))))
+
 (ert-deftest test-ai-code-backends-infra-buffer-user-visible-p ()
   "Return non-nil only when buffer has a visible window."
   (with-temp-buffer