diff --git a/packages/evals/framework/braintrust.ts b/packages/evals/framework/braintrust.ts
index 803f30d53b..1476fc629a 100644
--- a/packages/evals/framework/braintrust.ts
+++ b/packages/evals/framework/braintrust.ts
@@ -1,5 +1,9 @@
 let braintrustPromise: Promise<typeof import("braintrust")> | undefined;
 
+export function hasBraintrustApiKey(): boolean {
+  return Boolean(process.env.BRAINTRUST_API_KEY);
+}
+
 export function loadBraintrust(): Promise<typeof import("braintrust")> {
   braintrustPromise ??= import("braintrust");
   return braintrustPromise;
@@ -9,6 +13,9 @@ export async function tracedSpan<T>(
   fn: () => Promise<T>,
   options: { name: string },
 ): Promise<T> {
+  if (!hasBraintrustApiKey()) {
+    return fn();
+  }
   const { traced } = await loadBraintrust();
   return traced(fn, options);
 }
diff --git a/packages/evals/framework/runner.ts b/packages/evals/framework/runner.ts
index 336db1c029..2c712ecc22 100644
--- a/packages/evals/framework/runner.ts
+++ b/packages/evals/framework/runner.ts
@@ -22,7 +22,7 @@ import type { Testcase, EvalInput } from "../types/evals.js";
 import { generateBenchTestcases } from "./benchPlanner.js";
 import { DEFAULT_BENCH_HARNESS, type Harness } from "./benchTypes.js";
 import { executeBenchTask } from "./benchRunner.js";
-import { loadBraintrust, tracedSpan } from "./braintrust.js";
+import { hasBraintrustApiKey, loadBraintrust, tracedSpan } from "./braintrust.js";
 import { onceAsync, registerActiveRunCleanup } from "./activeRunCleanup.js";
 import { loadTaskModuleFromPath } from "./taskLoader.js";
 
@@ -352,6 +352,7 @@ export async function runEvals(
     : [exactMatch, errorMatch];
 
   const { Eval, flush } = await loadBraintrust();
+  const sendLogs = hasBraintrustApiKey();
 
   // Aggressive abort: when the caller flips signal.reason to "aggressive",
   // close every active session so any in-flight task throws on its next
@@ -440,10 +441,13 @@ export async function runEvals(
     {
       progress: silentBraintrustProgress,
       reporter: silentBraintrustReporter,
+      ...(sendLogs ? {} : { noSendLogs: true }),
     },
   );
 
-  await flush();
+  if (sendLogs) {
+    await flush();
+  }
 
   const summaryResults = evalResult.results.map((result) => {
     const output =
diff --git a/packages/evals/lib/AISdkClientWrapped.ts b/packages/evals/lib/AISdkClientWrapped.ts
index 213aaa0f34..1d4ab7df5f 100644
--- a/packages/evals/lib/AISdkClientWrapped.ts
+++ b/packages/evals/lib/AISdkClientWrapped.ts
@@ -21,16 +21,18 @@ import {
   toJsonSchema,
 } from "@browserbasehq/stagehand";
 
-let wrappedAiPromise:
-  | Promise<ReturnType<(typeof import("braintrust"))["wrapAISDK"]>>
-  | undefined;
+type WrappedAI = ReturnType<(typeof import("braintrust"))["wrapAISDK"]>;
 
-async function loadWrappedAISDK(): Promise<
-  ReturnType<(typeof import("braintrust"))["wrapAISDK"]>
-> {
-  wrappedAiPromise ??= import("braintrust").then(({ wrapAISDK }) =>
-    wrapAISDK(ai),
-  );
+let wrappedAiPromise: Promise<WrappedAI> | undefined;
+
+async function loadWrappedAISDK(): Promise<WrappedAI> {
+  wrappedAiPromise ??= (async () => {
+    if (!process.env.BRAINTRUST_API_KEY) {
+      return ai as unknown as WrappedAI;
+    }
+    const { wrapAISDK } = await import("braintrust");
+    return wrapAISDK(ai);
+  })();
   return wrappedAiPromise;
 }
 
diff --git a/packages/evals/tests/framework/braintrust-optional.test.ts b/packages/evals/tests/framework/braintrust-optional.test.ts
new file mode 100644
index 0000000000..97965fd9e8
--- /dev/null
+++ b/packages/evals/tests/framework/braintrust-optional.test.ts
@@ -0,0 +1,65 @@
+import { describe, it, expect, vi, beforeEach, afterEach } from "vitest";
+import {
+  hasBraintrustApiKey,
+  tracedSpan,
+} from "../../framework/braintrust.js";
+
+/**
+ * Verify that braintrust.ts helpers and AISdkClientWrapped work without
+ * BRAINTRUST_API_KEY. The runner-level tests live in a separate file
+ * (braintrust-runner-nolog.test.ts) because they need to vi.mock the
+ * braintrust module entirely.
+ */
+
+describe("braintrust.ts helpers without BRAINTRUST_API_KEY", () => {
+  const originalKey = process.env.BRAINTRUST_API_KEY;
+
+  beforeEach(() => {
+    delete process.env.BRAINTRUST_API_KEY;
+  });
+
+  afterEach(() => {
+    if (originalKey !== undefined) {
+      process.env.BRAINTRUST_API_KEY = originalKey;
+    } else {
+      delete process.env.BRAINTRUST_API_KEY;
+    }
+  });
+
+  it("hasBraintrustApiKey returns false when BRAINTRUST_API_KEY is unset", () => {
+    expect(hasBraintrustApiKey()).toBe(false);
+  });
+
+  it("hasBraintrustApiKey returns true when BRAINTRUST_API_KEY is set", () => {
+    process.env.BRAINTRUST_API_KEY = "test-key-123";
+    expect(hasBraintrustApiKey()).toBe(true);
+  });
+
+  it("tracedSpan calls fn directly without Braintrust when key is absent", async () => {
+    const fn = vi.fn(async () => 42);
+    const result = await tracedSpan(fn, { name: "test-span" });
+    expect(fn).toHaveBeenCalledOnce();
+    expect(result).toBe(42);
+  });
+});
+
+describe("AISdkClientWrapped without BRAINTRUST_API_KEY", () => {
+  const originalKey = process.env.BRAINTRUST_API_KEY;
+
+  beforeEach(() => {
+    delete process.env.BRAINTRUST_API_KEY;
+  });
+
+  afterEach(() => {
+    if (originalKey !== undefined) {
+      process.env.BRAINTRUST_API_KEY = originalKey;
+    } else {
+      delete process.env.BRAINTRUST_API_KEY;
+    }
+  });
+
+  it("AISdkClientWrapped class is importable without BRAINTRUST_API_KEY", async () => {
+    const mod = await import("../../lib/AISdkClientWrapped.js");
+    expect(mod.AISdkClientWrapped).toBeDefined();
+  });
+});
diff --git a/packages/evals/tests/framework/braintrust-runner-nolog.test.ts b/packages/evals/tests/framework/braintrust-runner-nolog.test.ts
new file mode 100644
index 0000000000..2978808b14
--- /dev/null
+++ b/packages/evals/tests/framework/braintrust-runner-nolog.test.ts
@@ -0,0 +1,112 @@
+import { describe, it, expect, vi, beforeEach, afterEach } from "vitest";
+
+/**
+ * Verify that the runner passes noSendLogs to Braintrust Eval and skips
+ * flush() when BRAINTRUST_API_KEY is absent. This file lives separately
+ * because it needs to vi.mock the braintrust module at the top level.
+ */
+
+vi.mock("playwright", () => ({
+  chromium: {},
+}));
+
+const mockEval = vi.fn(async () => ({
+  results: [],
+  summary: { experimentName: "test", scores: {} },
+}));
+const mockFlush = vi.fn(async () => {});
+let mockHasKey = false;
+
+vi.mock("../../framework/braintrust.js", () => ({
+  hasBraintrustApiKey: () => mockHasKey,
+  loadBraintrust: async () => ({
+    Eval: mockEval,
+    flush: mockFlush,
+  }),
+  tracedSpan: async <T>(fn: () => Promise<T>) => fn(),
+}));
+
+describe("runner.ts skips Braintrust logging when API key is absent", () => {
+  const originalKey = process.env.BRAINTRUST_API_KEY;
+
+  beforeEach(() => {
+    delete process.env.BRAINTRUST_API_KEY;
+    mockEval.mockClear();
+    mockFlush.mockClear();
+    mockHasKey = false;
+  });
+
+  afterEach(() => {
+    if (originalKey !== undefined) {
+      process.env.BRAINTRUST_API_KEY = originalKey;
+    } else {
+      delete process.env.BRAINTRUST_API_KEY;
+    }
+  });
+
+  it("passes noSendLogs: true to Eval when BRAINTRUST_API_KEY is unset", async () => {
+    mockHasKey = false;
+    const { runEvals } = await import("../../framework/runner.js");
+
+    const task = {
+      name: "test-task",
+      tier: "bench" as const,
+      primaryCategory: "extract",
+      categories: ["extract"],
+      tags: [],
+      filePath: "/fake.ts",
+      isLegacy: false,
+    };
+
+    await runEvals({
+      tasks: [task],
+      registry: {
+        tasks: [task],
+        byName: new Map([[task.name, task]]),
+        byTier: new Map([["bench", [task]]]),
+        byCategory: new Map([["extract", [task]]]),
+      },
+      trials: 1,
+    });
+
+    expect(mockEval).toHaveBeenCalledTimes(1);
+    const evalOptions = mockEval.mock.calls[0][2];
+    expect(evalOptions).toHaveProperty("noSendLogs", true);
+
+    // flush should NOT be called
+    expect(mockFlush).not.toHaveBeenCalled();
+  });
+
+  it("does NOT pass noSendLogs when BRAINTRUST_API_KEY is set", async () => {
+    mockHasKey = true;
+    const { runEvals } = await import("../../framework/runner.js");
+
+    const task = {
+      name: "test-task",
+      tier: "bench" as const,
+      primaryCategory: "extract",
+      categories: ["extract"],
+      tags: [],
+      filePath: "/fake.ts",
+      isLegacy: false,
+    };
+
+    await runEvals({
+      tasks: [task],
+      registry: {
+        tasks: [task],
+        byName: new Map([[task.name, task]]),
+        byTier: new Map([["bench", [task]]]),
+        byCategory: new Map([["extract", [task]]]),
+      },
+      trials: 1,
+    });
+
+    expect(mockEval).toHaveBeenCalledTimes(1);
+    const evalOptions = mockEval.mock.calls[0][2];
+    expect(evalOptions).not.toHaveProperty("noSendLogs");
+
+    // flush SHOULD be called
+    expect(mockFlush).toHaveBeenCalledTimes(1);
+  });
+});
diff --git a/packages/evals/tests/framework/core-runner.test.ts b/packages/evals/tests/framework/core-runner.test.ts
index 6d2879fb4f..6aa154af47 100644
--- a/packages/evals/tests/framework/core-runner.test.ts
+++ b/packages/evals/tests/framework/core-runner.test.ts
@@ -65,6 +65,9 @@ function makeRegistry(tasks: DiscoveredTask[]): TaskRegistry {
 beforeEach(() => {
   originalCi = process.env.CI;
   delete process.env.CI;
+  // Set a dummy API key so the runner sends logs and calls flush(),
+  // which this test asserts.
+  process.env.BRAINTRUST_API_KEY = "test-key";
   tracedNames.length = 0;
   evalMock.mockReset();
   flushMock.mockClear();
@@ -79,6 +82,7 @@ afterEach(() => {
   } else {
     process.env.CI = originalCi;
   }
+  delete process.env.BRAINTRUST_API_KEY;
 
   while (tempDirs.length > 0) {
     const dir = tempDirs.pop();