From f36aa9f456d0c91d6cd7884b824b565862edb9d8 Mon Sep 17 00:00:00 2001
From: Claude <noreply@anthropic.com>
Date: Thu, 24 Sep 2026 03:16:59 +0000
Subject: [PATCH] Buffer: bump version on every content change

SetDirty(false) did not bump the version, so undo back to the saved
state (and reload, and replace_all_bytes) left the highlighter serving
spans for the old text. Reloading a file deleted on disk now also
clears undo history recorded against the old content.

Audit finding D9.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_015rcVQiiWyTzoNrsvLSaAfB
---
 Buffer.cc |  6 ++++++
 Buffer.h  | 18 +++++++++++++-----
 2 files changed, 19 insertions(+), 5 deletions(-)

diff --git a/Buffer.cc b/Buffer.cc
index 99c8d9e..ebec980 100644
--- a/Buffer.cc
+++ b/Buffer.cc
@@ -455,6 +455,10 @@ Buffer::OpenFromFile(const std::string &path, std::string &err)
 		// Empty PieceTable
 		content_.Clear();
 		rows_cache_dirty_ = true;
+		// History recorded against the previous content no longer applies.
+		if (undo_sys_)
+			undo_sys_->clear();
+		MarkContentChanged();
 
 		return true;
 	}
@@ -520,6 +524,7 @@ Buffer::OpenFromFile(const std::string &path, std::string &err)
 		undo_sys_ = std::make_unique<UndoSystem>(*this, *undo_tree_);
 	// Clear any existing history for a fresh load
 	undo_sys_->clear();
+	MarkContentChanged();
 
 	// Reset cursor/viewport state
 	curx_      = cury_    = rx_ = 0;
@@ -829,6 +834,7 @@ Buffer::replace_all_bytes(const std::string_view bytes)
 	if (!bytes.empty())
 		content_.Append(bytes.data(), bytes.size());
 	rows_cache_dirty_ = true;
+	MarkContentChanged();
 }
 
 
diff --git a/Buffer.h b/Buffer.h
index 51fd17b..c6f177e 100644
--- a/Buffer.h
+++ b/Buffer.h
@@ -391,11 +391,19 @@ public:
 	void SetDirty(bool d)
 	{
 		dirty_ = d;
-		if (d) {
-			++version_;
-			if (highlighter_) {
-				highlighter_->InvalidateFrom(0);
-			}
+		// Bump even when clearing: undo/redo back to the saved state changes the
+		// text and then calls SetDirty(false). Without a bump the highlighter
+		// keeps serving spans for the pre-undo text.
+		MarkContentChanged();
+	}
+
+
+	// Invalidate version-keyed caches (syntax highlighting) after a content change.
+	void MarkContentChanged()
+	{
+		++version_;
+		if (highlighter_) {
+			highlighter_->InvalidateFrom(0);
 		}
 	}