Run browser file transcription through the long-form pipeline when asked and the VAD model is available

Adds an Advanced "Skip silence in uploaded files" option (off by default
pending measurement), the vad/longForm protocol fields, the old-path
fallback when the VAD model is missing, and a plain message for files
with no speech.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

tests/engine.test.ts

@@ -77,6 +77,15 @@ describe("BrowserEngine", () => {
     expect("modelId" in message).toBe(false);
   });
 
+  test("forwards the long-form request only when set (D-WS3a)", () => {
+    const worker = new FakeWorker();
+    const engine = new BrowserEngine(worker);
+    void engine.transcribe(new Float32Array(4), { longForm: true });
+    void engine.transcribe(new Float32Array(4));
+    expect(worker.posted[0]!.message.longForm).toBe(true);
+    expect("longForm" in worker.posted[1]!.message).toBe(false);
+  });
+
   test("asks the worker to stream only when a consumer listens", () => {
     const worker = new FakeWorker();
     const engine = new BrowserEngine(worker);

tests/longform-setting.test.ts

@@ -0,0 +1,55 @@
+import { describe, expect, test } from "bun:test";
+import { emptyTranscriptNotice } from "../src/lib/export";
+import {
+  LONG_FORM_DEFAULT,
+  LONG_FORM_KEY,
+  loadLongFormChoice,
+  saveLongFormChoice,
+} from "../src/lib/longForm";
+
+function memoryStorage(initial: Record<string, string> = {}) {
+  const data = { ...initial };
+  return {
+    data,
+    getItem: (key: string) => data[key] ?? null,
+    setItem: (key: string, value: string) => {
+      data[key] = value;
+    },
+  };
+}
+
+describe("long-form setting persistence (D-WS3a)", () => {
+  test("defaults when nothing is stored or storage is unavailable", () => {
+    expect(loadLongFormChoice(memoryStorage())).toBe(LONG_FORM_DEFAULT);
+    expect(loadLongFormChoice(null)).toBe(LONG_FORM_DEFAULT);
+    const throwing = {
+      getItem: () => {
+        throw new Error("denied");
+      },
+      setItem: () => {
+        throw new Error("denied");
+      },
+    };
+    expect(loadLongFormChoice(throwing)).toBe(LONG_FORM_DEFAULT);
+    expect(() => saveLongFormChoice(true, throwing)).not.toThrow();
+  });
+
+  test("round-trips an explicit choice", () => {
+    const storage = memoryStorage();
+    saveLongFormChoice(!LONG_FORM_DEFAULT, storage);
+    expect(storage.data[LONG_FORM_KEY]).toBeDefined();
+    expect(loadLongFormChoice(storage)).toBe(!LONG_FORM_DEFAULT);
+  });
+});
+
+describe("emptyTranscriptNotice (plan 001-0 Review Focus 4)", () => {
+  test("a finished transcript with no words says so plainly", () => {
+    expect(emptyTranscriptNotice({ text: "" })).toBe("No speech was found in this recording.");
+    expect(emptyTranscriptNotice({ text: "  \n" })).toBe("No speech was found in this recording.");
+  });
+
+  test("no notice while running or when there is text", () => {
+    expect(emptyTranscriptNotice(null)).toBeNull();
+    expect(emptyTranscriptNotice({ text: " Hello." })).toBeNull();
+  });
+});

tests/protocol.test.ts

@@ -4,6 +4,7 @@ import {
   deviceAttempts,
   dtypeRequiresF16,
   initialLoadProgress,
+  choosePipeline,
   isUiToWorkerMessage,
   isWorkerToUiMessage,
   TranscribeProgressTracker,
@@ -35,7 +36,9 @@ describe("isUiToWorkerMessage", () => {
       { type: "transcribe", audio: new Float32Array(8), requestId: "live-3" },
       { type: "transcribe", audio: new Float32Array(8), requestId: "engine-1-1", stream: true },
       { type: "transcribe", audio: new Float32Array(8), stream: false },
+      { type: "transcribe", audio: new Float32Array(8), stream: true, longForm: true },
     ];
+    loads.push({ type: "load", modelId: "onnx-community/whisper-base", device: "auto", vad: true });
     for (const message of [...loads, ...transcribes]) {
       expect(isUiToWorkerMessage(message)).toBe(true);
     }
@@ -65,10 +68,26 @@ describe("isUiToWorkerMessage", () => {
     expect(
       isUiToWorkerMessage({ type: "transcribe", audio: new Float32Array(4), stream: "yes" }),
     ).toBe(false);
+    expect(
+      isUiToWorkerMessage({ type: "transcribe", audio: new Float32Array(4), longForm: 1 }),
+    ).toBe(false);
+    expect(isUiToWorkerMessage({ type: "load", modelId: "x", device: "auto", vad: "yes" })).toBe(
+      false,
+    );
     expect(isUiToWorkerMessage({ type: "result", text: "", chunks: [] })).toBe(false);
   });
 });
 
+describe("choosePipeline (D-WS3a/D-WS3b)", () => {
+  test("long-form only when asked for and the VAD model loaded", () => {
+    expect(choosePipeline({ longForm: true, vadReady: true })).toBe("longform");
+    // Offline / never downloaded: the old path, never an error (Review Focus 3).
+    expect(choosePipeline({ longForm: true, vadReady: false })).toBe("chunked");
+    expect(choosePipeline({ longForm: false, vadReady: true })).toBe("chunked");
+    expect(choosePipeline({ longForm: undefined, vadReady: true })).toBe("chunked");
+  });
+});
+
 describe("isWorkerToUiMessage", () => {
   test("accepts every worker → UI message shape", () => {
     const messages: WorkerToUiMessage[] = [