feat: best-in-class multi-line input editor (replaces readline)

[agjs]

What

Replaces Node readline for the interactive prompt with a purpose-built, grapheme-aware multi-line editor. Fixes the original bug (a multi-line paste became N messages/steers) and makes the input a real editor.

• Enter submits; Shift+Enter / Alt+Enter / trailing \+Enter insert a newline.
• Paste lands in the buffer and never auto-submits; huge pastes show [paste #N +M lines] and expand on send.
• Grapheme-correct editing; word/line/document motion; kill-ring + yank; coalesced undo/redo; in-session history (↑/↓ at buffer edges); / palette + @ file picker operate on the editor buffer.
• Bracketed paste + Kitty keyboard + xterm modifyOtherKeys (env-gated for Windows/WSL/SSH) make Shift+Enter reliable.
• TSFORGE_BASIC_INPUT=1 falls back to the old single-line readline path.

How it's built

Pure, unit-tested modules (editor/): segments, buffer (text model + kill-ring + undo + paste markers), keys (decoder), paste (bracketed-paste scanner), view (multi-line renderer) — driven by controller (sole stdin owner in editor mode) and wired into cli.ts. Best-of pi + hermes + our painted input row.

Process & quality

Subagent-driven: 11 TDD tasks, each task-reviewed + fixed, plus a final whole-branch review — READY TO MERGE, zero findings. Stdin-ownership invariant, module composition, and the unchanged non-TTY/fallback path all verified. bun run validate green: 1672 pass, 0 fail. 53 editor unit tests + cli wiring.

Spec: docs/superpowers/specs/2026-06-26-multiline-editor-design.md · Plan: docs/superpowers/plans/2026-06-26-multiline-editor.md.

Live verification needed before merge (no PTY in CI)

1. Enter submits; Shift+Enter / Alt+Enter / trailing \+Enter → newline.
2. Multi-line paste lands in buffer (not N messages), sends as one on Enter; huge paste → [paste #N +M lines], log shows expanded text.
3. ↑/↓ recall history at buffer edges.
4. Ctrl+W / Ctrl+Y / Ctrl+U editing; / palette + @ picker insert into the buffer.
5. Ctrl-C aborts a run / quits at idle; Ctrl-D on empty quits; terminal restored after exit.
6. Resize re-wraps cleanly.
7. TSFORGE_BASIC_INPUT=1 falls back to single-line; echo x | tsforge unaffected.

🤖 Generated with Claude Code

[gemini-code-assist]

Code Review

This pull request replaces the Node readline interactive prompt in tsforge with a custom, grapheme-aware multi-line input editor supporting advanced editing features like bracketed paste, emacs-style kill-ring, and coalesced undo/redo. The code review identified several critical bugs and improvement opportunities: intermediate undo snapshots during multiline inserts should be avoided by parameterizing newline(); lastYank must be cleared in clearSticky() to prevent buffer corruption during yankPop; the active draft should be stored in a separate variable to avoid polluting the shared history; and several string slicing and wrapping operations must be updated to use grapheme counts instead of UTF-16 code units to ensure correct emoji and combining character handling.

Important

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For more details on the timeline and next steps, please review the Help Documentation.

[gemini-code-assist]

When inserting multiline text, calling this.newline() directly triggers maybeSnapshot('other') on each newline. This creates multiple undo snapshots for a single multiline insert or paste operation, forcing the user to press undo multiple times to revert a single paste. Passing false to newline prevents intermediate snapshots.

Suggested change

	if (i > 0) {
	this.newline();
	}
	if (i > 0) {
	this.newline(false);
	}

[gemini-code-assist]

Update the newline method signature to accept an optional snapshot parameter. This allows internal operations like insertRaw to perform newlines without creating intermediate undo snapshots, preserving the atomicity of multiline inserts.

Suggested change

	newline(): void {
	this.clearSticky();
	this.maybeSnapshot("other");
	const g = this.curG();
	const left = g.slice(0, this.cursorCol).join("");
	newline(snapshot = true): void {
	this.clearSticky();
	if (snapshot) {
	this.maybeSnapshot("other");
	}

[gemini-code-assist]

To prevent buffer corruption, this.lastYank must be cleared whenever any other motion or editing command is executed. Otherwise, performing a yankPop after moving the cursor or editing another line will execute the splice at the old column index on the new line.

Suggested change

	private clearSticky(): void {
	this.stickyCol = null;
	}
	private clearSticky(): void {
	this.stickyCol = null;
	this.lastYank = null;
	}

[gemini-code-assist]

Since clearSticky() now invalidates this.lastYank, yankPop should clear stickyCol directly instead of calling clearSticky() to avoid immediately returning on the lastYank === null check.

Suggested change

	yankPop(): void {
	this.clearSticky();
	if (this.lastYank === null) {
	return;
	}
	yankPop(): void {
	this.stickyCol = null;
	if (this.lastYank === null) {
	return;
	}

[gemini-code-assist]

Declare a separate draftText variable in the closure to store the active draft. Pushing the draft directly to the shared history array pollutes the submitted message history if the user submits a message while browsing history.

Suggested change

	let historyIndex = -1; // -1 = not in history, >= 0 = viewing history item
	let dataListener: ((chunk: string) => void) | null = null;
	let historyIndex = -1; // -1 = not in history, >= 0 = viewing history item
	let draftText: string | null = null;
	let dataListener: ((chunk: string) => void) | null = null;

[gemini-code-assist]

Refactor navigateHistoryDown to restore the draft from draftText and clear it, avoiding the need to pop from the shared history array.

  function navigateHistoryDown(): void {
    if (historyIndex === -1) {
      return; // Not in history
    }

    if (historyIndex === history.length - 1) {
      // Restore draft
      buffer.setText(draftText ?? "");
      draftText = null;
      historyIndex = -1;
    } else {
      historyIndex += 1;
      buffer.setText(history[historyIndex] ?? "");
    }

    repaint();
    notifyChange();
  }

[gemini-code-assist]

Import graphemes from ./segments to enable grapheme-correct string slicing.

Suggested change

	import { EditorBuffer } from "./buffer";
	import { decodeKeys } from "./keys";
	import { createPasteScanner } from "./paste";
	import { renderEditor } from "./view";
	import { EditorBuffer } from "./buffer";
	import { decodeKeys } from "./keys";
	import { createPasteScanner } from "./paste";
	import { renderEditor } from "./view";
	import { graphemes } from "./segments";

[gemini-code-assist]

Using currentLine.substring(0, col) is incorrect because col is a grapheme offset, whereas substring expects UTF-16 code units. If there are any multi-unit graphemes (like emojis) before the cursor, the substring will be cut too early and fail to detect a trailing backslash. Slice the graphemes array instead.

Suggested change

	if (col > 0) {
	const beforeCursor = currentLine.substring(0, col);
	if (beforeCursor.endsWith("\\")) {
	hasTrailingBackslash = true;
	}
	}
	if (col > 0) {
	const lineGraphemes = graphemes(currentLine);
	const beforeCursor = lineGraphemes.slice(0, col).join("");
	if (beforeCursor.endsWith("\\")) {
	hasTrailingBackslash = true;
	}
	}

[gemini-code-assist]

Using row.length to wrap lines and set rowCursorCol is incorrect because it counts UTF-16 code units instead of visual columns (graphemes). Emojis and combining characters will cause premature wrapping and incorrect cursor positioning. Use a grapheme counter instead.

function wrapLine(
  line: string,
  cursorCol: number,
  columns: number
): IWrappedRow[] {
  if (columns <= 0) {
    return [];
  }

  const graphemeList = graphemes(line);
  const rows: IWrappedRow[] = [];
  let row = "";
  let rowGraphemeCount = 0;
  let rowCursorCol: number | undefined;
  let visualRow = 0;

  for (let i = 0; i < graphemeList.length; i += 1) {
    const g = graphemeList[i];

    if (rowGraphemeCount >= columns) {
      rows.push({
        text: row,
        cursorRow: rowCursorCol !== undefined ? visualRow : undefined,
        cursorCol: rowCursorCol,
      });
      row = "";
      rowGraphemeCount = 0;
      rowCursorCol = undefined;
      visualRow += 1;
    }

    if (i === cursorCol) {
      rowCursorCol = rowGraphemeCount;
    }

    if (g !== undefined) {
      row += g;
      rowGraphemeCount += 1;
    }
  }

  // Handle cursor at end of line
  if (graphemeList.length === cursorCol) {
    rowCursorCol = rowGraphemeCount;
  }

  // Push final row
  rows.push({
    text: row,
    cursorRow: rowCursorCol !== undefined ? visualRow : undefined,
    cursorCol: rowCursorCol,
  });

  return rows;
}

[gemini-code-assist]

Correct the copy-paste brand reference from 'The Dreamdata Platform's CLI' to 'The tsforge CLI'.

The tsforge CLI uses an interactive multi-line input editor for the REPL session. It supports full keyboard navigation, history recall, word deletion, and multi-line paste.