diff --git a/integrations/openai-agents-js/src/index.ts b/integrations/openai-agents-js/src/index.ts
index 244d0b81c..43b63be08 100644
--- a/integrations/openai-agents-js/src/index.ts
+++ b/integrations/openai-agents-js/src/index.ts
@@ -322,6 +322,13 @@ export class OpenAIAgentsTraceProcessor {
     const traceData = this.traceSpans.get(trace.traceId);
 
     if (traceData) {
+      // End any child spans that are still open. This protects against a race
+      // where the OpenAI SDK emits onTraceEnd before our onSpanEnd handler runs.
+      for (const [, braintrustSpan] of traceData.childSpans) {
+        braintrustSpan.end();
+      }
+      traceData.childSpans.clear();
+
       traceData.rootSpan.log({
         input: traceData.metadata.firstInput,
         output: traceData.metadata.lastOutput,
diff --git a/integrations/openai-agents-js/src/openai-agents-trace-processor.test.ts b/integrations/openai-agents-js/src/openai-agents-trace-processor.test.ts
index 4f76eb786..5e2810cd3 100644
--- a/integrations/openai-agents-js/src/openai-agents-trace-processor.test.ts
+++ b/integrations/openai-agents-js/src/openai-agents-trace-processor.test.ts
@@ -1,5 +1,6 @@
 import { assert, describe, test } from "vitest";
 import { OpenAIAgentsTraceProcessor } from "./index";
+import type { AgentsSpan, AgentsTrace } from "./types";
 
 function createDeferredPromise(): {
   promise: Promise<void>;
@@ -13,6 +14,93 @@ function createDeferredPromise(): {
   return { promise, resolve };
 }
 
+class MockBraintrustSpan {
+  public endCalls = 0;
+  public readonly logs: Array<Record<string, unknown>> = [];
+
+  startSpan(_args: { name: string; type: string }): MockBraintrustSpan {
+    return new MockBraintrustSpan();
+  }
+
+  log(payload: Record<string, unknown>): void {
+    this.logs.push(payload);
+  }
+
+  end(): void {
+    this.endCalls += 1;
+  }
+}
+
+function createTrace(traceId: string): AgentsTrace {
+  return {
+    type: "trace",
+    traceId,
+    name: "test-trace",
+    groupId: null,
+    metadata: {},
+  };
+}
+
+function createGenerationSpan(
+  traceId: string,
+  spanId: string,
+  parentId: string | null = null,
+): AgentsSpan {
+  return {
+    type: "trace.span",
+    traceId,
+    spanId,
+    parentId,
+    startedAt: new Date().toISOString(),
+    endedAt: new Date(Date.now() + 10).toISOString(),
+    error: null,
+    spanData: {
+      type: "generation",
+      input: [{ role: "user", content: "hello" }],
+      output: [{ role: "assistant", content: "world" }],
+    },
+  };
+}
+
+function createProcessorWithMockLogger(): OpenAIAgentsTraceProcessor {
+  return new OpenAIAgentsTraceProcessor({
+    logger: {
+      startSpan: () => new MockBraintrustSpan(),
+      flush: async () => {},
+    } as any,
+  });
+}
+
+function requireTraceData(
+  processor: OpenAIAgentsTraceProcessor,
+  traceId: string,
+): {
+  rootSpan: unknown;
+  childSpans: Map<string, unknown>;
+  metadata: unknown;
+} {
+  const traceData = processor._traceSpans.get(traceId);
+  if (!traceData) {
+    throw new Error(`Expected trace data for traceId=${traceId}`);
+  }
+  return traceData as unknown as {
+    rootSpan: unknown;
+    childSpans: Map<string, unknown>;
+    metadata: unknown;
+  };
+}
+
+function requireChildSpan(
+  traceData: { childSpans: Map<string, unknown> },
+  spanId: string,
+): MockBraintrustSpan {
+  const span = traceData.childSpans.get(spanId);
+  if (!span) {
+    throw new Error(`Expected child span for spanId=${spanId}`);
+  }
+  return span as MockBraintrustSpan;
+}
+
 describe("OpenAIAgentsTraceProcessor flush behavior", () => {
   test("forceFlush waits for logger.flush to complete", async () => {
     let flushCalls = 0;
@@ -92,3 +180,101 @@ describe("OpenAIAgentsTraceProcessor flush behavior", () => {
     );
   });
 });
+
+describe("OpenAIAgentsTraceProcessor span race handling", () => {
+  test("child spans are ended when onTraceEnd runs before onSpanEnd", async () => {
+    const processor = createProcessorWithMockLogger();
+    const trace = createTrace("race-trace-1");
+    const span = createGenerationSpan(trace.traceId, "race-span-1");
+
+    await processor.onTraceStart(trace);
+    await processor.onSpanStart(span);
+
+    const traceData = requireTraceData(processor, trace.traceId);
+    const childSpan = requireChildSpan(traceData, span.spanId);
+    assert.equal(childSpan.endCalls, 0, "Child span should start unended");
+
+    await processor.onTraceEnd(trace);
+
+    assert.equal(
+      childSpan.endCalls,
+      1,
+      "Child span should be ended when trace ends first",
+    );
+    assert.isFalse(
+      processor._traceSpans.has(trace.traceId),
+      "Trace data should be cleaned up after onTraceEnd",
+    );
+  });
+
+  test("onSpanEnd after onTraceEnd is a safe no-op", async () => {
+    const processor = createProcessorWithMockLogger();
+    const trace = createTrace("race-trace-2");
+    const span = createGenerationSpan(trace.traceId, "race-span-2");
+
+    await processor.onTraceStart(trace);
+    await processor.onSpanStart(span);
+
+    const traceData = requireTraceData(processor, trace.traceId);
+    const childSpan = requireChildSpan(traceData, span.spanId);
+
+    await processor.onTraceEnd(trace);
+    assert.equal(
+      childSpan.endCalls,
+      1,
+      "Child span should be ended by trace end",
+    );
+
+    await processor.onSpanEnd(span);
+
+    assert.equal(
+      childSpan.endCalls,
+      1,
+      "Late onSpanEnd should not fail or double-end the span",
+    );
+  });
+
+  test("multiple child spans are all ended when onTraceEnd runs first", async () => {
+    const processor = createProcessorWithMockLogger();
+    const trace = createTrace("race-trace-3");
+    const spanA = createGenerationSpan(trace.traceId, "span-a");
+    const spanB = createGenerationSpan(trace.traceId, "span-b");
+    const spanC = createGenerationSpan(trace.traceId, "span-c", spanB.spanId);
+
+    await processor.onTraceStart(trace);
+    await processor.onSpanStart(spanA);
+    await processor.onSpanStart(spanB);
+    await processor.onSpanStart(spanC);
+
+    const traceData = requireTraceData(processor, trace.traceId);
+    const childSpanA = requireChildSpan(traceData, spanA.spanId);
+    const childSpanB = requireChildSpan(traceData, spanB.spanId);
+    const childSpanC = requireChildSpan(traceData, spanC.spanId);
+
+    // End one span through the normal path to verify trace end only closes remaining spans.
+    await processor.onSpanEnd(spanA);
+    assert.equal(
+      childSpanA.endCalls,
+      1,
+      "Span A should be ended once normally",
+    );
+
+    await processor.onTraceEnd(trace);
+
+    assert.equal(
+      childSpanA.endCalls,
+      1,
+      "Span A should not be double-ended on trace end",
+    );
+    assert.equal(
+      childSpanB.endCalls,
+      1,
+      "Span B should be ended by onTraceEnd",
+    );
+    assert.equal(
+      childSpanC.endCalls,
+      1,
+      "Span C should be ended by onTraceEnd",
+    );
+  });
+});