fix (tui): coalesce rapid git-bash submit bursts into multiline paste

src/tui/tui.submit-handler.test.ts

@@ -1,5 +1,9 @@
 import { describe, expect, it, vi } from "vitest";
-import { createEditorSubmitHandler } from "./tui.js";
+import {
+  createEditorSubmitHandler,
+  createSubmitBurstCoalescer,
+  shouldEnableWindowsGitBashPasteFallback,
+} from "./tui.js";
 
 describe("createEditorSubmitHandler", () => {
   it("routes lines starting with ! to handleBangLine", () => {
@@ -118,3 +122,70 @@ describe("createEditorSubmitHandler", () => {
     expect(handleBangLine).not.toHaveBeenCalled();
   });
 });
+
+describe("createSubmitBurstCoalescer", () => {
+  it("coalesces rapid single-line submits into one multiline submit when enabled", () => {
+    vi.useFakeTimers();
+    const submit = vi.fn();
+    let now = 1_000;
+    const onSubmit = createSubmitBurstCoalescer({
+      submit,
+      enabled: true,
+      burstWindowMs: 50,
+      now: () => now,
+    });
+
+    onSubmit("Line 1");
+    now += 10;
+    onSubmit("Line 2");
+    now += 10;
+    onSubmit("Line 3");
+
+    expect(submit).not.toHaveBeenCalled();
+
+    vi.advanceTimersByTime(50);
+
+    expect(submit).toHaveBeenCalledTimes(1);
+    expect(submit).toHaveBeenCalledWith("Line 1\nLine 2\nLine 3");
+    vi.useRealTimers();
+  });
+
+  it("passes through immediately when disabled", () => {
+    const submit = vi.fn();
+    const onSubmit = createSubmitBurstCoalescer({
+      submit,
+      enabled: false,
+    });
+
+    onSubmit("Line 1");
+    onSubmit("Line 2");
+
+    expect(submit).toHaveBeenCalledTimes(2);
+    expect(submit).toHaveBeenNthCalledWith(1, "Line 1");
+    expect(submit).toHaveBeenNthCalledWith(2, "Line 2");
+  });
+});
+
+describe("shouldEnableWindowsGitBashPasteFallback", () => {
+  it("enables fallback on Windows Git Bash env", () => {
+    expect(
+      shouldEnableWindowsGitBashPasteFallback({
+        platform: "win32",
+        env: {
+          MSYSTEM: "MINGW64",
+        } as NodeJS.ProcessEnv,
+      }),
+    ).toBe(true);
+  });
+
+  it("disables fallback outside Windows", () => {
+    expect(
+      shouldEnableWindowsGitBashPasteFallback({
+        platform: "darwin",
+        env: {
+          MSYSTEM: "MINGW64",
+        } as NodeJS.ProcessEnv,
+      }),
+    ).toBe(false);
+  });
+});

src/tui/tui.ts

@@ -77,6 +77,99 @@ export function createEditorSubmitHandler(params: {
   };
 }
 
+export function shouldEnableWindowsGitBashPasteFallback(params?: {
+  platform?: string;
+  env?: NodeJS.ProcessEnv;
+}): boolean {
+  const platform = params?.platform ?? process.platform;
+  if (platform !== "win32") {
+    return false;
+  }
+  const env = params?.env ?? process.env;
+  const msystem = (env.MSYSTEM ?? "").toUpperCase();
+  const shell = env.SHELL ?? "";
+  const termProgram = (env.TERM_PROGRAM ?? "").toLowerCase();
+  if (msystem.startsWith("MINGW") || msystem.startsWith("MSYS")) {
+    return true;
+  }
+  if (shell.toLowerCase().includes("bash")) {
+    return true;
+  }
+  return termProgram.includes("mintty");
+}
+
+export function createSubmitBurstCoalescer(params: {
+  submit: (value: string) => void;
+  enabled: boolean;
+  burstWindowMs?: number;
+  now?: () => number;
+  setTimer?: typeof setTimeout;
+  clearTimer?: typeof clearTimeout;
+}) {
+  const windowMs = Math.max(1, params.burstWindowMs ?? 50);
+  const now = params.now ?? (() => Date.now());
+  const setTimer = params.setTimer ?? setTimeout;
+  const clearTimer = params.clearTimer ?? clearTimeout;
+  let pending: string | null = null;
+  let pendingAt = 0;
+  let flushTimer: ReturnType<typeof setTimeout> | null = null;
+
+  const clearFlushTimer = () => {
+    if (!flushTimer) {
+      return;
+    }
+    clearTimer(flushTimer);
+    flushTimer = null;
+  };
+
+  const flushPending = () => {
+    if (pending === null) {
+      return;
+    }
+    const value = pending;
+    pending = null;
+    pendingAt = 0;
+    clearFlushTimer();
+    params.submit(value);
+  };
+
+  const scheduleFlush = () => {
+    clearFlushTimer();
+    flushTimer = setTimer(() => {
+      flushPending();
+    }, windowMs);
+  };
+
+  return (value: string) => {
+    if (!params.enabled) {
+      params.submit(value);
+      return;
+    }
+    if (value.includes("\n")) {
+      flushPending();
+      params.submit(value);
+      return;
+    }
+    const ts = now();
+    if (pending === null) {
+      pending = value;
+      pendingAt = ts;
+      scheduleFlush();
+      return;
+    }
+    if (ts - pendingAt <= windowMs) {
+      pending = `${pending}\n${value}`;
+      pendingAt = ts;
+      scheduleFlush();
+      return;
+    }
+    flushPending();
+    pending = value;
+    pendingAt = ts;
+    scheduleFlush();
+  };
+}
+
 export function resolveTuiSessionKey(params: {
   raw?: string;
   sessionScope: SessionScope;
@@ -612,12 +705,16 @@ export async function runTui(opts: TuiOptions) {
     closeOverlay,
   });
   updateAutocompleteProvider();
-  editor.onSubmit = createEditorSubmitHandler({
+  const submitHandler = createEditorSubmitHandler({
     editor,
     handleCommand,
     sendMessage,
     handleBangLine: runLocalShellLine,
   });
+  editor.onSubmit = createSubmitBurstCoalescer({
+    submit: submitHandler,
+    enabled: shouldEnableWindowsGitBashPasteFallback(),
+  });
 
   editor.onEscape = () => {
     void abortActive();