From d06db09a53958e485131527db25c1293f29b9367 Mon Sep 17 00:00:00 2001
From: Georgi <46296586+Exrun94@users.noreply.github.com>
Date: Fri, 24 Apr 2026 14:30:49 +0300
Subject: [PATCH] fix(tui): decode CSI-u Ctrl+letter inside bracketed paste,
 fixes #3599 (#3623)

Co-authored-by: Georgi Chochev <georgi.chochev@siteground.com>
---
 packages/tui/src/components/editor.ts | 14 +++++++++++++-
 packages/tui/test/editor.test.ts      | 10 ++++++++++
 2 files changed, 23 insertions(+), 1 deletion(-)

diff --git a/packages/tui/src/components/editor.ts b/packages/tui/src/components/editor.ts
index a0337d60..990469e5 100644
--- a/packages/tui/src/components/editor.ts
+++ b/packages/tui/src/components/editor.ts
@@ -1088,8 +1088,20 @@ export class Editor implements Component, Focusable {
 
 		this.pushUndoSnapshot();
 
+		// Some terminals (e.g. tmux popups with extended-keys-format=csi-u) re-encode
+		// control bytes inside bracketed paste as CSI-u Ctrl+<letter> sequences
+		// (ESC [ <codepoint> ; 5 u). Decode those back to their literal byte so the
+		// per-char filter below preserves newlines instead of stripping ESC and
+		// leaking the printable tail (e.g. "[106;5u") into the editor.
+		const decodedText = pastedText.replace(/\x1b\[(\d+);5u/g, (match, code) => {
+			const cp = Number(code);
+			if (cp >= 97 && cp <= 122) return String.fromCharCode(cp - 96);
+			if (cp >= 65 && cp <= 90) return String.fromCharCode(cp - 64);
+			return match;
+		});
+
 		// Clean the pasted text: normalize line endings, expand tabs
-		const cleanText = this.normalizeText(pastedText);
+		const cleanText = this.normalizeText(decodedText);
 
 		// Filter out non-printable characters except newlines
 		let filteredText = cleanText
diff --git a/packages/tui/test/editor.test.ts b/packages/tui/test/editor.test.ts
index c3805129..99dd1cc7 100644
--- a/packages/tui/test/editor.test.ts
+++ b/packages/tui/test/editor.test.ts
@@ -1677,6 +1677,16 @@ describe("Editor component", () => {
 			assert.strictEqual(editor.isShowingAutocomplete(), false);
 		});
 
+		it("decodes CSI-u Ctrl+letter sequences inside bracketed paste (tmux popup)", () => {
+			const editor = new Editor(createTestTUI(), defaultEditorTheme);
+
+			// tmux popups with extended-keys-format=csi-u re-encode \n in pastes as
+			// \x1b[106;5u (Ctrl+J). Without decoding, the per-char filter strips ESC
+			// and leaks "[106;5u" between lines. See issue #3599.
+			editor.handleInput("\x1b[200~line1\x1b[106;5uline2\x1b[106;5uline3\x1b[201~");
+			assert.strictEqual(editor.getText(), "line1\nline2\nline3");
+		});
+
 		it("undoes multi-line paste atomically", () => {
 			const editor = new Editor(createTestTUI(), defaultEditorTheme);