fix(table): decorate resumed history tables lazily on scroll

pi-coding-agent-render.el

@@ -5251,8 +5251,10 @@ Uses the current buffer's completed-thinking display mode."
 (defun pi-coding-agent--history-postprocess-start ()
   "Return the first position that needs eager history post-processing.
 Large resumed histories should render the visible tail promptly.  Older content
-can rely on normal jit-lock when visited, while display-only table decoration is
-kept to the same hot-tail suffix used by resize refreshes."
+relies on jit-lock when visited: tree-sitter fontification and the registered
+`pi-coding-agent--jit-decorate-tables' pass both run as each region scrolls into
+view, so eager decoration is limited to the same hot-tail suffix used by resize
+refreshes."
   (if (markerp pi-coding-agent--hot-tail-start)
       (marker-position pi-coding-agent--hot-tail-start)
     (point-min)))
@@ -5274,8 +5276,10 @@ contain `|' but cannot be pipe tables.")
   "Run consolidated display post-processing after history replay.
 History replay inserts many small user/assistant chunks.  Running fontification
 and table decoration after each chunk is expensive in large sessions, so replay
-defers that work.  Fontification is left to jit-lock on redisplay; the only
-synchronous pass decorates candidate tables in the recent hot tail."
+defers that work.  Fontification and table decoration are both left to jit-lock
+on redisplay (see `pi-coding-agent--jit-decorate-tables'); the only synchronous
+pass here decorates candidate tables in the recent hot tail so the visible tail
+is a grid immediately, without waiting for a redisplay."
   (let ((start (pi-coding-agent--history-postprocess-start))
         (end (point-max)))
     (when (pi-coding-agent--history-table-candidate-p start end)

pi-coding-agent-table.el

@@ -35,6 +35,7 @@
 ;; - `pi-coding-agent--decorate-tables-in-region' — stable path
 ;; - `pi-coding-agent--maybe-decorate-streaming-table' — streaming path
 ;; - `pi-coding-agent--maybe-refresh-hot-tail-tables' — resize path
+;; - `pi-coding-agent--jit-decorate-tables' — lazy scroll-into-view path
 ;;
 ;; Depends on `pi-coding-agent-ui' for visible-text extraction and
 ;; scroll preservation, and on `markdown-table-wrap' for the wrapping engine.
@@ -630,6 +631,31 @@ Idempotent: existing table overlays in the region are removed first."
       (when (pi-coding-agent--table-has-data-row-p (car region) (cdr region))
         (pi-coding-agent--decorate-table (car region) (cdr region) width)))))
 
+;;;; Lazy Scroll-Into-View Decoration (jit-lock)
+
+;; History replay only decorates the hot tail eagerly (see
+;; `pi-coding-agent--postprocess-history-buffer'); older tables are left as raw
+;; markdown so large resumed sessions load promptly.  Tree-sitter fontification
+;; already renders lazily as jit-lock brings each region into view, but table
+;; decoration is a display-overlay pass that jit-lock does not know about, so
+;; older tables would stay raw until a resize or manual toggle.  Registering a
+;; jit-lock function closes that gap: as you scroll an older table into view,
+;; it is decorated on the same redisplay pass that fontifies it -- no load-time
+;; cost, because jit-lock only ever runs on regions about to be displayed.
+
+(defun pi-coding-agent--jit-decorate-tables (beg end)
+  "Decorate pipe tables overlapping BEG..END, expanded to whole tables.
+Registered with `jit-lock-register' so tables render when scrolled into
+view.  jit-lock hands out arbitrary chunk boundaries that may bisect a
+table, so the region is grown to the full extent of every overlapping
+table before decorating; this keeps the idempotent overlay-removal in
+`pi-coding-agent--decorate-tables-in-region' aligned to whole tables and
+never leaves a table decorated from a partial range."
+  (when-let* ((regions (pi-coding-agent--treesit-table-regions beg end)))
+    (let ((full-beg (apply #'min beg (mapcar #'car regions)))
+          (full-end (apply #'max end (mapcar #'cdr regions))))
+      (pi-coding-agent--decorate-tables-in-region full-beg full-end))))
+
 ;;;; Cleanup
 
 (defun pi-coding-agent--cleanup-visible-string-buffer ()

pi-coding-agent-ui.el

@@ -60,6 +60,7 @@
 (declare-function pi-coding-agent--cleanup-on-kill "pi-coding-agent-render")
 (declare-function pi-coding-agent--restore-tool-properties "pi-coding-agent-render")
 (declare-function pi-coding-agent--maybe-refresh-hot-tail-tables "pi-coding-agent-table")
+(declare-function pi-coding-agent--jit-decorate-tables "pi-coding-agent-table")
 
 ;; pi-coding-agent-input.el (input buffer commands)
 (declare-function pi-coding-agent-quit "pi-coding-agent-input")
@@ -857,6 +858,12 @@ This is a read-only buffer showing the conversation history."
   ;; Run after font-lock to undo markdown damage in tool overlays.
   (jit-lock-register #'pi-coding-agent--restore-tool-properties)
 
+  ;; Decorate pipe tables lazily as they scroll into view.  History replay
+  ;; eagerly decorates only the hot tail; this jit-lock pass renders older
+  ;; tables on the same redisplay that fontifies them, so resumed sessions
+  ;; stay fast to load yet every table becomes a grid once seen.
+  (jit-lock-register #'pi-coding-agent--jit-decorate-tables)
+
   ;; Compute theme-derived faces used by chat overlays.
   (pi-coding-agent--update-theme-derived-faces)
 

test/pi-coding-agent-table-test.el

@@ -885,6 +885,60 @@ what the parser recognizes as a `pipe_table'."
     (pi-coding-agent--display-message-delta "| Auth | Done |\n")
     (should (>= (pi-coding-agent-test--table-overlay-count) 1))))
 
+(ert-deftest pi-coding-agent-test-jit-decorate-tables-decorates-region ()
+  "jit-decorate-tables renders a table overlapping the requested region."
+  (with-temp-buffer
+    (pi-coding-agent-chat-mode)
+    (let ((inhibit-read-only t))
+      (insert pi-coding-agent-test--wide-table))
+    (font-lock-ensure)
+    (pi-coding-agent--jit-decorate-tables (point-min) (point-max))
+    (should (>= (pi-coding-agent-test--table-overlay-count) 1))))
+
+(ert-deftest pi-coding-agent-test-jit-decorate-tables-expands-partial-region ()
+  "A jit-lock chunk that bisects a table still decorates the whole table.
+jit-lock hands out arbitrary boundaries; the region is grown to the full
+tree-sitter table extent so overlays cover every row, not a partial range."
+  (with-temp-buffer
+    (pi-coding-agent-chat-mode)
+    (let ((table-beg nil)
+          (inhibit-read-only t))
+      (insert "Some intro prose before the table.\n\n")
+      (setq table-beg (point))
+      (insert pi-coding-agent-test--wide-table)
+      (font-lock-ensure)
+      ;; Request a range that begins in the middle of the table and ends
+      ;; before its last row -- the worst case for a redisplay chunk.
+      (pi-coding-agent--jit-decorate-tables (+ table-beg 20) (- (point-max) 20))
+      ;; The whole four-line table (header, separator, two data rows) gets
+      ;; one overlay per raw line, so all rows are covered, not just those
+      ;; inside the narrow request.
+      (should (= (pi-coding-agent-test--table-overlay-count) 4)))))
+
+(ert-deftest pi-coding-agent-test-jit-decorate-tables-noop-without-table ()
+  "jit-decorate-tables creates no overlays when the region has no table."
+  (with-temp-buffer
+    (pi-coding-agent-chat-mode)
+    (let ((inhibit-read-only t))
+      (insert "Just prose here, no pipe table at all.\n\nMore prose.\n"))
+    (font-lock-ensure)
+    (pi-coding-agent--jit-decorate-tables (point-min) (point-max))
+    (should (= (pi-coding-agent-test--table-overlay-count) 0))))
+
+(ert-deftest pi-coding-agent-test-jit-decorate-tables-respects-raw-toggle ()
+  "jit-decorate-tables leaves user-toggled raw tables undecorated.
+The `pi-coding-agent--skip-raw-tables' advice guards every decoration
+path, including this lazy one, so scrolling a raw table into view does
+not clobber the user's choice."
+  (with-temp-buffer
+    (pi-coding-agent-chat-mode)
+    (let ((inhibit-read-only t))
+      (insert pi-coding-agent-test--wide-table))
+    (font-lock-ensure)
+    (pi-coding-agent--mark-table-raw (point-min) (point-max))
+    (pi-coding-agent--jit-decorate-tables (point-min) (point-max))
+    (should (= (pi-coding-agent-test--table-overlay-count) 0))))
+
 (ert-deftest pi-coding-agent-test-chat-buffer-hidden-p-sees-visible-window-on-other-frame ()
   "A chat buffer visible on another frame is not hidden."
   (with-temp-buffer