fix(tui): handle multi-line text in insertTextAtCursor()

Add insertTextAtCursorInternal() to properly handle newlines by splitting
lines at the cursor position.

- Normalize line endings (CRLF/CR to LF)
- Handle single-line and multi-line insertion
- Position cursor at end of inserted text
- Call onChange only once at the end

Refactor handlePaste() to use insertTextAtCursorInternal() for
multi-line pastes, while retaining character-by-character insertion for
single-line pastes to preserve autocomplete triggering.

packages/tui/src/components/editor.ts

@@ -823,8 +823,62 @@ export class Editor implements Component, Focusable {
 		if (!text) return;
 		this.pushUndoSnapshot();
 		this.lastAction = null;
-		for (const char of text) {
-			this.insertCharacter(char, true);
+		this.historyIndex = -1;
+		this.insertTextAtCursorInternal(text);
+	}
+
+	/**
+	 * Internal text insertion at cursor. Handles single and multi-line text.
+	 * Does not push undo snapshots or trigger autocomplete - caller is responsible.
+	 * Normalizes line endings and calls onChange once at the end.
+	 */
+	private insertTextAtCursorInternal(text: string): void {
+		if (!text) return;
+
+		// Normalize line endings
+		const normalized = text.replace(/\r\n/g, "\n").replace(/\r/g, "\n");
+		const insertedLines = normalized.split("\n");
+
+		const currentLine = this.state.lines[this.state.cursorLine] || "";
+		const beforeCursor = currentLine.slice(0, this.state.cursorCol);
+		const afterCursor = currentLine.slice(this.state.cursorCol);
+
+		if (insertedLines.length === 1) {
+			// Single line - insert at cursor position
+			this.state.lines[this.state.cursorLine] = beforeCursor + normalized + afterCursor;
+			this.state.cursorCol += normalized.length;
+		} else {
+			// Multi-line insertion
+			const newLines: string[] = [];
+
+			// Add all lines before current line
+			for (let i = 0; i < this.state.cursorLine; i++) {
+				newLines.push(this.state.lines[i] || "");
+			}
+
+			// Add the first inserted line merged with text before cursor
+			newLines.push(beforeCursor + (insertedLines[0] || ""));
+
+			// Add all middle inserted lines
+			for (let i = 1; i < insertedLines.length - 1; i++) {
+				newLines.push(insertedLines[i] || "");
+			}
+
+			// Add the last inserted line with text after cursor
+			newLines.push((insertedLines[insertedLines.length - 1] || "") + afterCursor);
+
+			// Add all lines after current line
+			for (let i = this.state.cursorLine + 1; i < this.state.lines.length; i++) {
+				newLines.push(this.state.lines[i] || "");
+			}
+
+			this.state.lines = newLines;
+			this.state.cursorLine += insertedLines.length - 1;
+			this.state.cursorCol = (insertedLines[insertedLines.length - 1] || "").length;
+		}
+
+		if (this.onChange) {
+			this.onChange(this.getText());
 		}
 	}
 
@@ -836,7 +890,7 @@ export class Editor implements Component, Focusable {
 		// - Consecutive word chars coalesce into one undo unit
 		// - Space captures state before itself (so undo removes space+following word together)
 		// - Each space is separately undoable
-		// Skip coalescing when called from atomic operations (paste, insertTextAtCursor)
+		// Skip coalescing when called from atomic operations (e.g., handlePaste)
 		if (!skipUndoCoalescing) {
 			if (isWhitespaceChar(char) || this.lastAction !== "type-word") {
 				this.pushUndoSnapshot();
@@ -918,7 +972,7 @@ export class Editor implements Component, Focusable {
 			}
 		}
 
-		// Split into lines
+		// Split into lines to check for large paste
 		const pastedLines = filteredText.split("\n");
 
 		// Check if this is a large paste (> 10 lines or > 1000 characters)
@@ -934,61 +988,20 @@ export class Editor implements Component, Focusable {
 				pastedLines.length > 10
 					? `[paste #${pasteId} +${pastedLines.length} lines]`
 					: `[paste #${pasteId} ${totalChars} chars]`;
-			for (const char of marker) {
-				this.insertCharacter(char, true);
-			}
+			this.insertTextAtCursorInternal(marker);
 			return;
 		}
 
 		if (pastedLines.length === 1) {
-			// Single line - just insert each character
-			const text = pastedLines[0] || "";
-			for (const char of text) {
+			// Single line - insert character by character to trigger autocomplete
+			for (const char of filteredText) {
 				this.insertCharacter(char, true);
 			}
 			return;
 		}
 
-		// Multi-line paste - be very careful with array manipulation
-		const currentLine = this.state.lines[this.state.cursorLine] || "";
-		const beforeCursor = currentLine.slice(0, this.state.cursorCol);
-		const afterCursor = currentLine.slice(this.state.cursorCol);
-
-		// Build the new lines array step by step
-		const newLines: string[] = [];
-
-		// Add all lines before current line
-		for (let i = 0; i < this.state.cursorLine; i++) {
-			newLines.push(this.state.lines[i] || "");
-		}
-
-		// Add the first pasted line merged with before cursor text
-		newLines.push(beforeCursor + (pastedLines[0] || ""));
-
-		// Add all middle pasted lines
-		for (let i = 1; i < pastedLines.length - 1; i++) {
-			newLines.push(pastedLines[i] || "");
-		}
-
-		// Add the last pasted line with after cursor text
-		newLines.push((pastedLines[pastedLines.length - 1] || "") + afterCursor);
-
-		// Add all lines after current line
-		for (let i = this.state.cursorLine + 1; i < this.state.lines.length; i++) {
-			newLines.push(this.state.lines[i] || "");
-		}
-
-		// Replace the entire lines array
-		this.state.lines = newLines;
-
-		// Update cursor position to end of pasted content
-		this.state.cursorLine += pastedLines.length - 1;
-		this.state.cursorCol = (pastedLines[pastedLines.length - 1] || "").length;
-
-		// Notify of change
-		if (this.onChange) {
-			this.onChange(this.getText());
-		}
+		// Multi-line paste - use direct state manipulation
+		this.insertTextAtCursorInternal(filteredText);
 	}
 
 	private addNewLine(): void {

packages/tui/test/editor.test.ts

@@ -1466,6 +1466,44 @@ describe("Editor component", () => {
 			assert.strictEqual(editor.getText(), "hello| world");
 		});
 
+		it("insertTextAtCursor handles multiline text", () => {
+			const editor = new Editor(createTestTUI(), defaultEditorTheme);
+
+			editor.setText("hello world");
+			editor.handleInput("\x01"); // Ctrl+A - go to start
+			for (let i = 0; i < 5; i++) editor.handleInput("\x1b[C"); // Move right 5 (after "hello", before space)
+
+			// Insert multiline text
+			editor.insertTextAtCursor("line1\nline2\nline3");
+			assert.strictEqual(editor.getText(), "helloline1\nline2\nline3 world");
+
+			// Cursor should be at end of inserted text (after "line3", before " world")
+			const cursor = editor.getCursor();
+			assert.strictEqual(cursor.line, 2);
+			assert.strictEqual(cursor.col, 5); // "line3".length
+
+			// Single undo should restore entire pre-insert state
+			editor.handleInput("\x1b[45;5u"); // Ctrl+- (undo)
+			assert.strictEqual(editor.getText(), "hello world");
+		});
+
+		it("insertTextAtCursor normalizes CRLF and CR line endings", () => {
+			const editor = new Editor(createTestTUI(), defaultEditorTheme);
+
+			editor.setText("");
+
+			// Insert text with CRLF
+			editor.insertTextAtCursor("a\r\nb\r\nc");
+			assert.strictEqual(editor.getText(), "a\nb\nc");
+
+			editor.handleInput("\x1b[45;5u"); // Undo
+			assert.strictEqual(editor.getText(), "");
+
+			// Insert text with CR only
+			editor.insertTextAtCursor("x\ry\rz");
+			assert.strictEqual(editor.getText(), "x\ny\nz");
+		});
+
 		it("undoes setText to empty string", () => {
 			const editor = new Editor(createTestTUI(), defaultEditorTheme);