Strip copies in the substring filter, not via yank-handler

agent-shell-markdown.el

@@ -466,14 +466,6 @@ body un-fontified."
         ;; chunk and would otherwise clear our `face' properties.
         (agent-shell-markdown--mirror-face-to-font-lock-face
          (point-min) (point-max))
-        ;; Tag rendered chars so a yank into another buffer drops the
-        ;; styling, display overrides, internal markers, and keymaps
-        ;; we layered on — paste should give plain chars, not our
-        ;; implementation cruft.
-        (put-text-property (point-min) (point-max)
-                           'yank-handler
-                           (list (lambda (s)
-                                   (insert (substring-no-properties s)))))
         ;; Mark rendered chars `fontified' so jit-lock never re-runs over
         ;; them during a mouse drag.  We style via `face'/`font-lock-face'
         ;; text properties, not font-lock keywords (`font-lock-defaults'

agent-shell.el

@@ -2083,6 +2083,10 @@ See also `agent-shell-confirm-interrupt'."
   "Return visible text between START and END, stripping hidden markup.
 If DELETE is non-nil, delete the text between START and END.
 
+The result carries no text properties, and \"> \" prefixes added
+by `agent-shell--block-quote' are dropped, so pasting a copy gives
+plain text matching what was on screen.
+
 START and END may be given in either order: like the stock
 `buffer-substring', a reversed range (START > END, e.g. a
 right-to-left mouse selection or a kill where mark > point) is
@@ -2105,10 +2109,13 @@ copy depending on selection direction."
         (setq pos (max next (1+ pos)))))
     (when delete
       (delete-region beg fin))
-    (remove-text-properties 0 (length text)
-                            '(line-prefix nil wrap-prefix nil)
-                            text)
-    text))
+    ;; One "> " per line, matching what the block quote inserted.
+    (substring-no-properties
+     (replace-regexp-in-string
+      (rx line-start "> ")
+      (lambda (match)
+        (if (get-text-property 0 'agent-shell-block-quote match) "" match))
+      text nil t))))
 
 (defvar-keymap agent-shell-mode-map
   :parent shell-maker-mode-map
@@ -9645,8 +9652,9 @@ When DEACTIVATE is non-nil, deactivate region/selection."
   "Return TEXT with each line prefixed by \"> \", displayed as a bar.
 
 Underlying text keeps the \"> \" so it remains valid markdown;
-the bar is a display-only override.  Yanks strip both the bar
-styling and the leading \"> \" so paste gives plain text."
+the bar is a display-only override.  The `agent-shell-block-quote'
+property tells `agent-shell--filter-buffer-substring' to drop the
+\"> \" from copies so paste gives plain text."
   (let* ((bar      (propertize "▌" 'face 'agent-shell-markdown-blockquote))
          (wrap     (propertize "▌ " 'face 'agent-shell-markdown-blockquote))
          (quoted   (concat "> " (replace-regexp-in-string
@@ -9657,12 +9665,7 @@ styling and the leading \"> \" so paste gives plain text."
      0 (length rendered)
      (list 'wrap-prefix wrap
            'face 'agent-shell-markdown-blockquote
-           'yank-handler
-           (list (lambda (s)
-                   (insert
-                    (replace-regexp-in-string
-                     (rx line-start "> ") ""
-                     (substring-no-properties s))))))
+           'agent-shell-block-quote t)
      rendered)
     (while (string-match (rx line-start ">") rendered pos)
       (put-text-property (match-beginning 0) (match-end 0)

tests/agent-shell-markdown-tests.el

@@ -3594,22 +3594,6 @@ A " nil)
     (should (string-match-p "^hello\nworld\n$"
                             (substring-no-properties (buffer-string))))))
 
-(ert-deftest agent-shell-markdown-yank-strips-properties ()
-  ;; Rendered chars carry a `yank-handler' that strips every text
-  ;; property on paste — display overrides, internal markers, faces,
-  ;; keymaps — so a copy/paste into another buffer gives plain chars,
-  ;; not our implementation cruft.
-  (with-temp-buffer
-    (insert "**bold** and `code`\n")
-    (agent-shell-markdown-replace-markup)
-    (kill-new (buffer-substring (point-min) (point-max))))
-  (with-temp-buffer
-    (yank)
-    (let ((pos (point-min)))
-      (while (< pos (point-max))
-        (should-not (text-properties-at pos))
-        (setq pos (1+ pos))))))
-
 (ert-deftest agent-shell-markdown-convert-blockquote-single-level ()
   ;; `> text\n' keeps the `>' in the buffer (source round-trips) but
   ;; shows `▌' as a display override.  The line content carries the

tests/agent-shell-tests.el

@@ -4225,6 +4225,42 @@ direction."
       (should (equal forward "hello world"))
       (should (equal reversed forward)))))
 
+(ert-deftest agent-shell-filter-buffer-substring-strips-text-properties ()
+  "Copied rendered output carries no text properties.
+Faces, display overrides, and internal markers stay in the buffer;
+a copy/paste into another buffer gives plain chars."
+  (with-temp-buffer
+    (insert "**bold** and `code`\n")
+    (agent-shell-markdown-replace-markup)
+    (let ((result (agent-shell--filter-buffer-substring (point-min) (point-max)))
+          (pos 0))
+      (should (equal result "bold and code\n"))
+      (while (< pos (length result))
+        (should-not (text-properties-at pos result))
+        (setq pos (1+ pos))))))
+
+(ert-deftest agent-shell-filter-buffer-substring-strips-block-quote-prefix ()
+  "Copying quoted text drops the \"> \" `agent-shell--block-quote' added."
+  (with-temp-buffer
+    (insert (agent-shell--block-quote "hello\nworld"))
+    (should (equal (agent-shell--filter-buffer-substring (point-min) (point-max))
+                   "hello\nworld"))))
+
+(ert-deftest agent-shell-filter-buffer-substring-strips-one-quote-level ()
+  "Quoting already-quoted text keeps the inner \"> \" on copy."
+  (with-temp-buffer
+    (insert (agent-shell--block-quote "> hello"))
+    (should (equal (agent-shell--filter-buffer-substring (point-min) (point-max))
+                   "> hello"))))
+
+(ert-deftest agent-shell-filter-buffer-substring-keeps-rendered-block-quote ()
+  "Markdown blockquotes copy with their \"> \" so the source round-trips."
+  (with-temp-buffer
+    (insert "> hello\n")
+    (agent-shell-markdown-replace-markup)
+    (should (equal (agent-shell--filter-buffer-substring (point-min) (point-max))
+                   "> hello\n"))))
+
 (ert-deftest agent-shell-trim-strips-untagged-whitespace ()
   ;; Plain `string-trim'-style behavior when nothing is tagged: outer
   ;; whitespace is removed.