fix(composer): forward Ctrl+Arrow to the terminal on Windows

src/components/ComposerBar.tsx

@@ -8,7 +8,10 @@ import { useNotificationStore } from "../stores/notificationStore";
 import { useCanvasStore, SIDEBAR_WIDTH, RIGHT_PANEL_WIDTH, COLLAPSED_TAB_WIDTH } from "../stores/canvasStore";
 import { getComposerAdapter } from "../terminal/cliConfig";
 import { filterSlashCommands } from "../terminal/slashCommands";
-import { shouldSubmitComposerFromKeyEvent } from "./composerInputBehavior";
+import {
+  getComposerPassthroughSequence,
+  shouldSubmitComposerFromKeyEvent,
+} from "./composerInputBehavior";
 import {
   getComposerTargetState,
   getSupportedTerminals,
@@ -69,52 +72,6 @@ function formatComposerFailure(
   return t.composer_submit_failed_with_context(targetTitle, stage, detail);
 }
 
-const ARROW_SEQUENCES: Record<string, string> = {
-  ArrowUp: "\x1b[A",
-  ArrowDown: "\x1b[B",
-  ArrowRight: "\x1b[C",
-  ArrowLeft: "\x1b[D",
-};
-
-/**
- * Map keyboard events to terminal escape sequences for keys that should be
- * forwarded to the PTY rather than handled by the Composer textarea.
- * Returns null if the key should stay in the textarea.
- */
-function getPassthroughSequence(
-  event: React.KeyboardEvent<HTMLTextAreaElement>,
-  draft: string,
-  hasImages: boolean,
-): string | null {
-  // Shift+Tab → mode cycling (e.g. Claude Code permission modes)
-  if (event.key === "Tab" && event.shiftKey) return "\x1b[Z";
-  // Escape → cancel / go back
-  if (event.key === "Escape") return "\x1b";
-  // Ctrl+C → interrupt (only when no text is selected, so copy still works)
-  if (event.key === "c" && event.ctrlKey && !event.metaKey) {
-    const el = event.target as HTMLTextAreaElement;
-    if (el.selectionStart === el.selectionEnd) {
-      return "\x03";
-    }
-  }
-  // Enter → forward to terminal when Composer has no content
-  // (e.g. confirm permission prompts, accept defaults)
-  if (event.key === "Enter" && !event.shiftKey && draft.trim().length === 0 && !hasImages) {
-    return "\r";
-  }
-  // Backspace → forward to terminal when Composer is empty
-  if (event.key === "Backspace" && draft.length === 0 && !hasImages) {
-    return "\x7f";
-  }
-  // Cmd+Arrow → always forward to terminal (history / cursor control)
-  // Plain Arrow → forward only when Composer is empty
-  const arrowSeq = ARROW_SEQUENCES[event.key];
-  if (arrowSeq && (event.metaKey || draft.trim().length === 0)) {
-    return arrowSeq;
-  }
-  return null;
-}
-
 export function ComposerBar() {
   const t = useT();
   const textareaRef = useRef<HTMLTextAreaElement>(null);
@@ -696,7 +653,12 @@ export function ComposerBar() {
                 }
 
                 if (targetTerminal) {
-                  const seq = getPassthroughSequence(event, draft, images.length > 0);
+                  const seq = getComposerPassthroughSequence(
+                    event,
+                    draft,
+                    images.length > 0,
+                    window.termcanvas?.app.platform ?? "darwin",
+                  );
                   if (seq !== null) {
                     event.preventDefault();
                     window.termcanvas.terminal.input(targetTerminal.ptyId, seq);

src/components/composerInputBehavior.ts

@@ -1,3 +1,5 @@
+import { hasPrimaryModifier } from "../hooks/shortcutTarget.ts";
+
 export interface ComposerKeyEventLike {
   key: string;
   shiftKey: boolean;
@@ -7,6 +9,24 @@ export interface ComposerKeyEventLike {
   };
 }
 
+export interface ComposerPassthroughKeyEventLike {
+  key: string;
+  shiftKey: boolean;
+  ctrlKey: boolean;
+  metaKey: boolean;
+  target?: {
+    selectionStart: number;
+    selectionEnd: number;
+  } | null;
+}
+
+const ARROW_SEQUENCES: Record<string, string> = {
+  ArrowUp: "\x1b[A",
+  ArrowDown: "\x1b[B",
+  ArrowRight: "\x1b[C",
+  ArrowLeft: "\x1b[D",
+};
+
 export function shouldSubmitComposerFromKeyEvent(
   event: ComposerKeyEventLike,
 ): boolean {
@@ -20,3 +40,36 @@ export function shouldSubmitComposerFromKeyEvent(
 
   return !(event.isComposing || event.nativeEvent?.isComposing);
 }
+
+export function getComposerPassthroughSequence(
+  event: ComposerPassthroughKeyEventLike,
+  draft: string,
+  hasImages: boolean,
+  platform: "darwin" | "win32" | "linux" = "darwin",
+): string | null {
+  if (event.key === "Tab" && event.shiftKey) return "\x1b[Z";
+  if (event.key === "Escape") return "\x1b";
+
+  if (event.key === "c" && event.ctrlKey && !event.metaKey) {
+    const selectionStart = event.target?.selectionStart;
+    const selectionEnd = event.target?.selectionEnd;
+    if (selectionStart === undefined || selectionStart === selectionEnd) {
+      return "\x03";
+    }
+  }
+
+  if (event.key === "Enter" && !event.shiftKey && draft.trim().length === 0 && !hasImages) {
+    return "\r";
+  }
+
+  if (event.key === "Backspace" && draft.length === 0 && !hasImages) {
+    return "\x7f";
+  }
+
+  const arrowSeq = ARROW_SEQUENCES[event.key];
+  if (arrowSeq && (hasPrimaryModifier(event, platform) || draft.trim().length === 0)) {
+    return arrowSeq;
+  }
+
+  return null;
+}

tests/composer-input-behavior.test.ts

@@ -1,7 +1,10 @@
 import test from "node:test";
 import assert from "node:assert/strict";
 
-import { shouldSubmitComposerFromKeyEvent } from "../src/components/composerInputBehavior.ts";
+import {
+  getComposerPassthroughSequence,
+  shouldSubmitComposerFromKeyEvent,
+} from "../src/components/composerInputBehavior.ts";
 
 test("Enter submits the composer", () => {
   assert.equal(
@@ -35,3 +38,37 @@ test("Composing text with an IME does not submit on Enter", () => {
     false,
   );
 });
+
+test("Windows Ctrl+Arrow forwards to terminal even with draft text", () => {
+  assert.equal(
+    getComposerPassthroughSequence(
+      {
+        key: "ArrowUp",
+        shiftKey: false,
+        ctrlKey: true,
+        metaKey: false,
+      },
+      "hello",
+      false,
+      "win32",
+    ),
+    "\x1b[A",
+  );
+});
+
+test("Windows plain Arrow stays in composer when draft has text", () => {
+  assert.equal(
+    getComposerPassthroughSequence(
+      {
+        key: "ArrowUp",
+        shiftKey: false,
+        ctrlKey: false,
+        metaKey: false,
+      },
+      "hello",
+      false,
+      "win32",
+    ),
+    null,
+  );
+});