fix(coding-agent): prevent full re-renders during write tool streaming

Move line count from header to footer to avoid changing the first line
during streaming, which was triggering full screen re-renders in the
TUI's differential rendering logic.

packages/coding-agent/src/modes/interactive/components/hook-editor.ts

@@ -0,0 +1,118 @@
+/**
+ * Multi-line editor component for hooks.
+ * Supports Ctrl+G for external editor.
+ */
+
+import { spawnSync } from "node:child_process";
+import * as fs from "node:fs";
+import * as os from "node:os";
+import * as path from "node:path";
+import { Container, Editor, isCtrlG, isEscape, Spacer, Text, type TUI } from "@mariozechner/pi-tui";
+import { getEditorTheme, theme } from "../theme/theme.js";
+import { DynamicBorder } from "./dynamic-border.js";
+
+export class HookEditorComponent extends Container {
+	private editor: Editor;
+	private onSubmitCallback: (value: string) => void;
+	private onCancelCallback: () => void;
+	private tui: TUI;
+
+	constructor(
+		tui: TUI,
+		title: string,
+		prefill: string | undefined,
+		onSubmit: (value: string) => void,
+		onCancel: () => void,
+	) {
+		super();
+
+		this.tui = tui;
+		this.onSubmitCallback = onSubmit;
+		this.onCancelCallback = onCancel;
+
+		// Add top border
+		this.addChild(new DynamicBorder());
+		this.addChild(new Spacer(1));
+
+		// Add title
+		this.addChild(new Text(theme.fg("accent", title), 1, 0));
+		this.addChild(new Spacer(1));
+
+		// Create editor
+		this.editor = new Editor(getEditorTheme());
+		if (prefill) {
+			this.editor.setText(prefill);
+		}
+		this.addChild(this.editor);
+
+		this.addChild(new Spacer(1));
+
+		// Add hint
+		const hasExternalEditor = !!(process.env.VISUAL || process.env.EDITOR);
+		const hint = hasExternalEditor
+			? "ctrl+enter submit  esc cancel  ctrl+g external editor"
+			: "ctrl+enter submit  esc cancel";
+		this.addChild(new Text(theme.fg("dim", hint), 1, 0));
+
+		this.addChild(new Spacer(1));
+
+		// Add bottom border
+		this.addChild(new DynamicBorder());
+	}
+
+	handleInput(keyData: string): void {
+		// Ctrl+Enter to submit
+		if (keyData === "\x1b[13;5u" || keyData === "\x1b[27;5;13~") {
+			this.onSubmitCallback(this.editor.getText());
+			return;
+		}
+
+		// Escape to cancel
+		if (isEscape(keyData)) {
+			this.onCancelCallback();
+			return;
+		}
+
+		// Ctrl+G for external editor
+		if (isCtrlG(keyData)) {
+			this.openExternalEditor();
+			return;
+		}
+
+		// Forward to editor
+		this.editor.handleInput(keyData);
+	}
+
+	private openExternalEditor(): void {
+		const editorCmd = process.env.VISUAL || process.env.EDITOR;
+		if (!editorCmd) {
+			return;
+		}
+
+		const currentText = this.editor.getText();
+		const tmpFile = path.join(os.tmpdir(), `pi-hook-editor-${Date.now()}.md`);
+
+		try {
+			fs.writeFileSync(tmpFile, currentText, "utf-8");
+			this.tui.stop();
+
+			const [editor, ...editorArgs] = editorCmd.split(" ");
+			const result = spawnSync(editor, [...editorArgs, tmpFile], {
+				stdio: "inherit",
+			});
+
+			if (result.status === 0) {
+				const newContent = fs.readFileSync(tmpFile, "utf-8").replace(/\n$/, "");
+				this.editor.setText(newContent);
+			}
+		} finally {
+			try {
+				fs.unlinkSync(tmpFile);
+			} catch {
+				// Ignore cleanup errors
+			}
+			this.tui.start();
+			this.tui.requestRender();
+		}
+	}
+}

packages/coding-agent/src/modes/interactive/components/tool-execution.ts

@@ -441,9 +441,6 @@ export class ToolExecutionComponent extends Container {
 				theme.fg("toolTitle", theme.bold("write")) +
 				" " +
 				(path ? theme.fg("accent", path) : theme.fg("toolOutput", "..."));
-			if (totalLines > 10) {
-				text += ` (${totalLines} lines)`;
-			}
 
 			if (fileContent) {
 				const maxLines = this.expanded ? lines.length : 10;
@@ -456,7 +453,7 @@ export class ToolExecutionComponent extends Container {
 						.map((line: string) => (lang ? replaceTabs(line) : theme.fg("toolOutput", replaceTabs(line))))
 						.join("\n");
 				if (remaining > 0) {
-					text += theme.fg("toolOutput", `\n... (${remaining} more lines)`);
+					text += theme.fg("toolOutput", `\n... (${remaining} more lines, ${totalLines} total)`);
 				}
 			}
 		} else if (this.toolName === "edit") {