Fix vterm-copy-mode disrupted by anti-flicker timer in Claude Code sessions

[Copilot]

Claude Code's complex ANSI output (spinners, progress redraws) consistently triggers the anti-flicker batching in vterm-smart-renderer. When the deferred render timer fired during vterm-copy-mode, it called vterm--filter and jumped the cursor back to the terminal bottom, making copy mode unusable. Simpler CLIs (Gemini, Codex) rarely hit the batching threshold, so they were unaffected.

Changes

• ai-code-backends-infra--vterm-smart-renderer: adds (bound-and-true-p vterm-copy-mode) to the batching predicate so all incoming data is queued rather than immediately rendered while copy mode is active; the timer callback now clears its own reference unconditionally but skips calling vterm--filter when copy mode is still on, preserving the queue.

• ai-code-backends-infra--vterm-flush-on-copy-mode-exit: new function that drains the pending render queue the moment the user exits copy mode — no output is lost.

• ai-code-backends-infra--configure-vterm-buffer: installs the flush function as a buffer-local vterm-copy-mode-hook.

• (defvar vterm-copy-mode): forward declaration added alongside the other vterm dynamic-variable declarations for clean byte-compilation.

;; Before: timer always called vterm--filter, disrupting copy position
(when ai-code-backends-infra--vterm-render-queue
  (let ((data ai-code-backends-infra--vterm-render-queue))
    (setq ai-code-backends-infra--vterm-render-queue nil
          ai-code-backends-infra--vterm-render-timer nil)
    (funcall orig-fun (get-buffer-process buf) data)))

;; After: skip render while in copy mode; flush via hook on exit
(setq ai-code-backends-infra--vterm-render-timer nil)
(when (and ai-code-backends-infra--vterm-render-queue
           (not (bound-and-true-p vterm-copy-mode)))
  (let ((data ai-code-backends-infra--vterm-render-queue))
    (setq ai-code-backends-infra--vterm-render-queue nil)
    (funcall orig-fun (get-buffer-process buf) data)))

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Original prompt

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This section details on the original issue you should resolve

<issue_title>Cannot use Vterm-Copy mode for Claude (I can for other AI agent CLIs).</issue_title>
<issue_description>Described in https://www.reddit.com/r/emacs/comments/1rvytih/best_claude_code_emacs_integration/</issue_description>

<agent_instructions>check https://www.reddit.com/r/emacs/comments/1rvytih/best_claude_code_emacs_integration/</agent_instructions>

Comments on the Issue (you are @copilot in this section)

• Fixes Cannot use Vterm-Copy mode for Claude (I can for other AI agent CLIs). #239

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