Fix memory-report error with gptel's transient history

gptel-transient-memory-test.el

@@ -0,0 +1,36 @@
+;;; gptel-transient-memory-test.el --- Test for memory-report compatibility  -*- lexical-binding: t; -*-
+
+;; This test verifies that the fix for GitHub issue #1032 works correctly.
+;; The issue was that memory-report would fail when trying to compute the
+;; size of gptel's transient history data containing backend structs.
+
+;;; Code:
+
+(require 'gptel-transient)
+(require 'gptel-gemini)
+
+;; Create a test backend
+(defvar test-backend (gptel-make-gemini "Test-Gemini"
+                                         :key "test-key"
+                                         :stream t))
+
+;; Create a provider object as used in gptel-menu
+(defvar test-provider-obj (make-instance 'gptel-provider-variable
+                                          :backend 'gptel-backend
+                                          :variable 'gptel-model))
+
+;; The fix: history-key and history-default should be nil to prevent
+;; storing the backend struct in transient-history
+(message "Testing memory-report compatibility fix...")
+(message "history-key is nil: %s" (null (oref test-provider-obj history-key)))
+(message "history-default is nil: %s" (null (oref test-provider-obj history-default)))
+
+;; This prevents the backend struct (with its bytecode) from being
+;; stored in transient-history, which was causing memory-report errors
+(if (and (null (oref test-provider-obj history-key))
+         (null (oref test-provider-obj history-default)))
+    (message "✓ Fix verified: Backend structs will not be stored in transient history")
+  (error "✗ Fix failed: Backend structs may still cause memory-report errors"))
+
+(provide 'gptel-transient-memory-test)
+;;; gptel-transient-memory-test.el ends here

gptel-transient.el

@@ -681,7 +681,10 @@ This is used only for setting this variable via `gptel-menu'.")
   ((backend       :initarg :backend)
    (backend-value :initarg :backend-value)
    (always-read :initform t)
-   (set-value :initarg :set-value :initform #'set))
+   (set-value :initarg :set-value :initform #'set)
+   ;; Prevent storing the backend struct in transient history to avoid memory-report errors
+   (history-default :initform nil)
+   (history-key :initform nil))
   "Class used for gptel-backends.")
 
 (cl-defmethod transient-format-value ((obj gptel-provider-variable))