Add eat backend anti-flicker support

Implement anti-flicker rendering optimization for eat terminal backend,
mirroring the existing vterm smart renderer functionality:

- Add eat-render-queue and timer variables for batched rendering
- Add eat-smart-renderer function with same pattern detection as vterm
- Add configure-eat-buffer function with display optimizations
- Call configure-eat-buffer from eat session creation
- Update vterm-anti-flicker docstring to note it applies to both backends
- Rename section from "Vterm Rendering Optimization" to "Terminal
  Rendering Optimization"

This brings feature parity between vterm and eat backends for flicker
reduction during Claude's output generation.

Author: manzaltu

README.org

@@ -191,7 +191,7 @@ This allows you to refine Claude's suggestions before they're applied, ensuring
 | ~claude-code-ide-cli-extra-flags~               | Additional CLI flags (e.g. "--model")       | ~""~                                   |
 | ~claude-code-ide-debug~                         | Enable debug logging                        | ~nil~                                  |
 | ~claude-code-ide-terminal-backend~              | Terminal backend (vterm or eat)             | ~'vterm~                               |
-| ~claude-code-ide-vterm-anti-flicker~            | Enable vterm flicker reduction              | ~t~                                    |
+| ~claude-code-ide-vterm-anti-flicker~            | Enable flicker reduction (vterm and eat)    | ~t~                                    |
 | ~claude-code-ide-vterm-render-delay~            | vterm render batching delay (seconds)       | ~0.016~                                |
 | ~claude-code-ide-fix-char-widths~               | Fix Unicode char widths to prevent flicker  | ~t~                                    |
 | ~claude-code-ide-terminal-initialization-delay~ | Initialization delay for terminals          | ~0.1~                                  |
@@ -263,12 +263,12 @@ Claude Code IDE supports both =vterm= and =eat= as terminal backends. By default
 
 The =eat= backend is a pure Elisp terminal emulator that may work better in some environments where =vterm= compilation is problematic. Both backends provide full terminal functionality including color support and special key handling.
 
-**** vterm Rendering Optimization
+**** Terminal Rendering Optimization
 
-Claude Code IDE includes intelligent flicker reduction for vterm terminals to provide smoother visual output:
+Claude Code IDE includes intelligent flicker reduction for both vterm and eat terminals to provide smoother visual output:
 
 #+begin_src emacs-lisp
-;; Enable/disable vterm anti-flicker optimization (enabled by default)
+;; Enable/disable anti-flicker optimization for vterm and eat (enabled by default)
 (setq claude-code-ide-vterm-anti-flicker t)
 
 ;; Adjust the render delay for batching updates (default is 0.016 seconds)

claude-code-ide.el

@@ -225,14 +225,14 @@ This setting should be removed once the upstream bug is fixed."
   :group 'claude-code-ide)
 
 (defcustom claude-code-ide-vterm-anti-flicker t
-  "Enable intelligent flicker reduction for vterm display.
+  "Enable intelligent flicker reduction for terminal display.
 When enabled, this feature optimizes terminal rendering by detecting
 and batching rapid update sequences.  This provides smoother visual
 output during complex terminal operations such as expanding text areas
 and rapid screen updates.
 
-This optimization applies only to vterm and uses advanced pattern
-matching to maintain responsiveness while improving visual quality."
+This optimization applies to both vterm and eat backends, using advanced
+pattern matching to maintain responsiveness while improving visual quality."
   :type 'boolean
   :group 'claude-code-ide)
 
@@ -300,13 +300,19 @@ single-width in Claude session buffers."
 (defvar claude-code-ide--last-accessed-buffer nil
   "The most recently accessed Claude Code buffer.")
 
-;;; Vterm Rendering Optimization
+;;; Terminal Rendering Optimization
 
 (defvar-local claude-code-ide--vterm-render-queue nil
-  "Queue for optimizing terminal rendering sequences.")
+  "Queue for optimizing vterm rendering sequences.")
 
 (defvar-local claude-code-ide--vterm-render-timer nil
-  "Timer for executing queued rendering operations.")
+  "Timer for executing queued vterm rendering operations.")
+
+(defvar-local claude-code-ide--eat-render-queue nil
+  "Queue for optimizing eat terminal rendering sequences.")
+
+(defvar-local claude-code-ide--eat-render-timer nil
+  "Timer for executing queued eat rendering operations.")
 
 (defun claude-code-ide--fix-char-widths ()
   "Set character widths for Claude's Unicode symbols to prevent flickering.
@@ -385,6 +391,52 @@ INPUT contains the terminal output stream."
           ;; Standard processing for regular output
           (funcall orig-fun process input))))))
 
+(defun claude-code-ide--eat-smart-renderer (orig-fun process input)
+  "Smart rendering filter for optimized eat display updates.
+Similar to vterm smart renderer - detects rapid redraw sequences
+and batches them for smoother visual output.
+
+ORIG-FUN is the underlying filter to enhance.
+PROCESS is the terminal process being optimized.
+INPUT contains the terminal output stream."
+  (if (or (not claude-code-ide-vterm-anti-flicker)
+          (not (claude-code-ide--session-buffer-p (process-buffer process))))
+      (funcall orig-fun process input)
+    (with-current-buffer (process-buffer process)
+      ;; Same pattern detection as vterm: escape density, clear count
+      (let* ((complex-redraw-detected
+              (string-match-p "\033\\[[0-9]*A.*\033\\[K.*\033\\[[0-9]*A.*\033\\[K" input))
+             (clear-count (cl-count-if (lambda (s) (string= s "\033[K"))
+                                       (split-string input "\033\\[K" t)))
+             (escape-count (cl-count ?\033 input))
+             (input-length (length input))
+             (escape-density (if (> input-length 0)
+                                 (/ (float escape-count) input-length)
+                               0)))
+        (if (or complex-redraw-detected
+                (and (> escape-density 0.3) (>= clear-count 2))
+                claude-code-ide--eat-render-queue)
+            (progn
+              (setq claude-code-ide--eat-render-queue
+                    (concat claude-code-ide--eat-render-queue input))
+              (when claude-code-ide--eat-render-timer
+                (cancel-timer claude-code-ide--eat-render-timer))
+              (setq claude-code-ide--eat-render-timer
+                    (run-at-time claude-code-ide-vterm-render-delay nil
+                                 (lambda (buf)
+                                   (when (buffer-live-p buf)
+                                     (with-current-buffer buf
+                                       (when claude-code-ide--eat-render-queue
+                                         (let ((inhibit-redisplay t)
+                                               (data claude-code-ide--eat-render-queue))
+                                           (setq claude-code-ide--eat-render-queue nil
+                                                 claude-code-ide--eat-render-timer nil)
+                                           (funcall orig-fun
+                                                    (get-buffer-process buf)
+                                                    data))))))
+                                 (current-buffer))))
+          (funcall orig-fun process input))))))
+
 (defvar-local claude-code-ide--saved-cursor-type nil
   "Saved cursor-type before entering vterm-copy-mode.")
 
@@ -436,6 +488,25 @@ cursor management, and process buffering for superior user experience."
   (when claude-code-ide-vterm-anti-flicker
     (advice-add 'vterm--filter :around #'claude-code-ide--vterm-smart-renderer)))
 
+(defun claude-code-ide--configure-eat-buffer ()
+  "Configure eat for enhanced performance and visual quality.
+Establishes optimal terminal settings including rendering optimizations
+and display fixes for superior user experience."
+  ;; Try to prevent cursor flickering by disabling Emacs' own cursor management
+  (setq-local cursor-in-non-selected-windows nil)
+  (setq-local blink-cursor-mode nil)
+  ;; disable hl-line-mode, eliminates another source of flicker
+  (when (featurep 'hl-line)
+    (hl-line-mode -1))
+  ;; make sure the non-breaking space in the prompt isn't themed
+  (face-remap-add-relative 'nobreak-space :inherit 'default)
+  ;; Fix character widths for Claude's Unicode symbols
+  (when claude-code-ide-fix-char-widths
+    (claude-code-ide--fix-char-widths))
+  ;; Set up rendering optimization
+  (when claude-code-ide-vterm-anti-flicker
+    (advice-add 'eat--filter :around #'claude-code-ide--eat-smart-renderer)))
+
 
 ;;; Terminal Backend Abstraction
 
@@ -813,11 +884,11 @@ when navigating between terminal and other buffers."
             (with-selected-window win
               (goto-char terminal-point)
               (recenter -1)))  ; Pin to bottom
-           ;; Terminal out of view: restore visibility
+           ;; Terminal out of view: restore visibility at bottom
            ((not (pos-visible-in-window-p terminal-point win))
             (with-selected-window win
               (goto-char terminal-point)
-              (recenter)))))))))
+              (recenter -1)))))))))
 
 (defun claude-code-ide--parse-command-string (command-string)
   "Parse a command string into (program . args) for eat-exec.
@@ -892,6 +963,8 @@ Signals an error if terminal fails to initialize."
           ;; Set up eat mode
           (unless (eq major-mode 'eat-mode)
             (eat-mode))
+          ;; Configure eat buffer for optimal performance
+          (claude-code-ide--configure-eat-buffer)
           ;; Configure position preservation if enabled
           (when claude-code-ide-eat-preserve-position
             (setq-local eat--synchronize-scroll-function