diff --git a/.changeset/gentle-streams-flow.md b/.changeset/gentle-streams-flow.md
new file mode 100644
index 0000000000..16113f7c8e
--- /dev/null
+++ b/.changeset/gentle-streams-flow.md
@@ -0,0 +1,5 @@
+---
+"@trigger.dev/core": patch
+---
+
+Fix batch trigger failing with "ReadableStream is locked" error when network failures occur mid-stream. Added safe stream cancellation that gracefully handles locked streams during retry attempts.
diff --git a/packages/core/src/v3/apiClient/index.ts b/packages/core/src/v3/apiClient/index.ts
index 7b07b2fb60..8efbc762ab 100644
--- a/packages/core/src/v3/apiClient/index.ts
+++ b/packages/core/src/v3/apiClient/index.ts
@@ -444,14 +444,14 @@ export class ApiClient {
 
         if (retryResult.retry) {
           // Cancel the request stream before retry to prevent tee() from buffering
-          await forRequest.cancel();
+          await safeStreamCancel(forRequest);
           await sleep(retryResult.delay);
           // Use the backup stream for retry
           return this.#streamBatchItemsWithRetry(batchId, forRetry, retryOptions, attempt + 1);
         }
 
         // Not retrying - cancel the backup stream
-        await forRetry.cancel();
+        await safeStreamCancel(forRetry);
 
         const errText = await response.text().catch((e) => (e as Error).message);
         let errJSON: Object | undefined;
@@ -471,7 +471,7 @@ export class ApiClient {
 
       if (!parsed.success) {
         // Cancel backup stream since we're throwing
-        await forRetry.cancel();
+        await safeStreamCancel(forRetry);
         throw new Error(
           `Invalid response from server for batch ${batchId}: ${parsed.error.message}`
         );
@@ -484,14 +484,14 @@ export class ApiClient {
 
         if (delay) {
           // Cancel the request stream before retry to prevent tee() from buffering
-          await forRequest.cancel();
+          await safeStreamCancel(forRequest);
           // Retry with the backup stream
           await sleep(delay);
           return this.#streamBatchItemsWithRetry(batchId, forRetry, retryOptions, attempt + 1);
         }
 
         // No more retries - cancel backup stream and throw descriptive error
-        await forRetry.cancel();
+        await safeStreamCancel(forRetry);
         throw new BatchNotSealedError({
           batchId,
           enqueuedCount: parsed.data.enqueuedCount ?? 0,
@@ -502,7 +502,7 @@ export class ApiClient {
       }
 
       // Success - cancel the backup stream to release resources
-      await forRetry.cancel();
+      await safeStreamCancel(forRetry);
 
       return parsed.data;
     } catch (error) {
@@ -519,13 +519,13 @@ export class ApiClient {
       const delay = calculateNextRetryDelay(retryOptions, attempt);
       if (delay) {
         // Cancel the request stream before retry to prevent tee() from buffering
-        await forRequest.cancel();
+        await safeStreamCancel(forRequest);
         await sleep(delay);
         return this.#streamBatchItemsWithRetry(batchId, forRetry, retryOptions, attempt + 1);
       }
 
       // No more retries - cancel the backup stream
-      await forRetry.cancel();
+      await safeStreamCancel(forRetry);
 
       // Wrap in a more descriptive error
       const cause = error instanceof Error ? error : new Error(String(error));
@@ -1731,6 +1731,30 @@ function sleep(ms: number): Promise<void> {
   return new Promise((resolve) => setTimeout(resolve, ms));
 }
 
+/**
+ * Safely cancels a ReadableStream, handling the case where it might be locked.
+ *
+ * When fetch uses a ReadableStream as a request body and an error occurs mid-transfer
+ * (connection reset, timeout, etc.), the stream may remain locked by fetch's internal reader.
+ * Attempting to cancel a locked stream throws "Invalid state: ReadableStream is locked".
+ *
+ * This function gracefully handles that case by catching the error and doing nothing -
+ * the stream will be cleaned up by garbage collection when the reader is released.
+ */
+async function safeStreamCancel(stream: ReadableStream<unknown>): Promise<void> {
+  try {
+    await stream.cancel();
+  } catch (error) {
+    // Ignore "locked" errors - the stream will be cleaned up when the reader is released.
+    // This happens when fetch crashes mid-read and doesn't release the reader lock.
+    if (error instanceof TypeError && String(error).includes("locked")) {
+      return;
+    }
+    // Re-throw unexpected errors
+    throw error;
+  }
+}
+
 // ============================================================================
 // NDJSON Stream Helpers
 // ============================================================================
diff --git a/packages/core/src/v3/apiClient/streamBatchItems.test.ts b/packages/core/src/v3/apiClient/streamBatchItems.test.ts
index c148f9b68e..23a42b5732 100644
--- a/packages/core/src/v3/apiClient/streamBatchItems.test.ts
+++ b/packages/core/src/v3/apiClient/streamBatchItems.test.ts
@@ -398,6 +398,58 @@ describe("streamBatchItems stream cancellation on retry", () => {
     expect(cancelCallCount).toBeGreaterThanOrEqual(1);
   });
 
+  it("handles locked stream when connection error occurs mid-read", async () => {
+    // This test simulates the real-world scenario where fetch throws an error
+    // while still holding the reader lock on the request body stream.
+    // This can happen with connection resets, timeouts, or network failures.
+    let callIndex = 0;
+
+    const mockFetch = vi.fn().mockImplementation(async (_url: string, init?: RequestInit) => {
+      const currentAttempt = callIndex;
+      callIndex++;
+
+      if (init?.body && init.body instanceof ReadableStream) {
+        if (currentAttempt === 0) {
+          // First attempt: Get a reader and start reading, but throw while still holding the lock.
+          // This simulates a connection error that happens mid-transfer.
+          const reader = init.body.getReader();
+          await reader.read(); // Start reading
+          // DON'T release the lock - this simulates fetch crashing mid-read
+          throw new TypeError("Connection reset by peer");
+        }
+
+        // Subsequent attempts: consume and release normally
+        await consumeAndRelease(init.body);
+      }
+
+      // Second attempt: success
+      return {
+        ok: true,
+        json: () =>
+          Promise.resolve({
+            id: "batch_test123",
+            itemsAccepted: 10,
+            itemsDeduplicated: 0,
+            sealed: true,
+          }),
+      };
+    });
+    globalThis.fetch = mockFetch;
+
+    const client = new ApiClient("http://localhost:3030", "tr_test_key");
+
+    // This should NOT throw "ReadableStream is locked" error
+    // Instead it should gracefully handle the locked stream and retry
+    const result = await client.streamBatchItems(
+      "batch_test123",
+      [{ index: 0, task: "test-task", payload: "{}" }],
+      { retry: { maxAttempts: 3, minTimeoutInMs: 10, maxTimeoutInMs: 50 } }
+    );
+
+    expect(result.sealed).toBe(true);
+    expect(mockFetch).toHaveBeenCalledTimes(2);
+  });
+
   it("does not leak memory by leaving tee branches unconsumed during multiple retries", async () => {
     let cancelCallCount = 0;
     let callIndex = 0;