diff --git a/kits/bigquery-firestore-export/src/handlers.ts b/kits/bigquery-firestore-export/src/handlers.ts
index 13ddddd535..3c5ad0bb30 100644
--- a/kits/bigquery-firestore-export/src/handlers.ts
+++ b/kits/bigquery-firestore-export/src/handlers.ts
@@ -23,6 +23,7 @@ import {
   createTransferConfig,
   type DataTransferClient,
   getTransferConfig,
+  PARTITIONING_FIELD_REMOVAL_ERROR_PREFIX,
   updateTransferConfig,
 } from "./dts";
 import type { ResolvedBigqueryFirestoreExportConfig } from "./export-config";
@@ -64,6 +65,13 @@ async function ensureNotificationTopic(ctx: HandlerContext): Promise<void> {
   }
 }
 
+function isPartitioningFieldRemovalError(err: unknown): err is Error {
+  return (
+    err instanceof Error &&
+    err.message.includes(PARTITIONING_FIELD_REMOVAL_ERROR_PREFIX)
+  );
+}
+
 async function storeTransferConfig(
   ctx: HandlerContext,
   transferConfig: Awaited<ReturnType<typeof getTransferConfig>>
@@ -105,9 +113,10 @@ export async function handleUpsertTransferConfig(
       ctx.config.transferConfigName
     );
     if (!linked) {
-      throw new Error(
-        `Transfer config not found: ${ctx.config.transferConfigName}`
-      );
+      // Only a redeploy with a corrected TRANSFER_CONFIG_NAME can resolve this,
+      // so retrying the task cannot help.
+      logs.linkedTransferConfigMissing(ctx.config.transferConfigName);
+      return;
     }
     await storeTransferConfig(ctx, linked);
     return;
@@ -128,14 +137,21 @@ export async function handleUpsertTransferConfig(
   const transferConfigName = existing.docs[0].data().name;
   if (typeof transferConfigName !== "string" || !transferConfigName) {
     throw new Error(
-      `Existing transfer config document in ${ctx.config.firestoreCollection} is missing required 'name' field.`
+      `Existing transfer config document in ${ctx.config.firestoreCollection} is missing required 'name' field. Delete the document so a new scheduled query is created, then redeploy.`
     );
   }
 
-  const updated = await updateTransferConfig(
-    ctx.dataTransfer,
-    transferConfigName,
-    ctx.config
-  );
-  await storeTransferConfig(ctx, updated);
+  try {
+    const updated = await updateTransferConfig(
+      ctx.dataTransfer,
+      transferConfigName,
+      ctx.config
+    );
+    await storeTransferConfig(ctx, updated);
+  } catch (err) {
+    if (!isPartitioningFieldRemovalError(err)) throw err;
+    // The guard rejects the update while building the request, so nothing was
+    // sent and a retry hits the same guard.
+    logs.partitioningFieldRemovalAborted(err.message);
+  }
 }
diff --git a/kits/bigquery-firestore-export/src/logs.ts b/kits/bigquery-firestore-export/src/logs.ts
index 0848691139..96e93ac1e7 100644
--- a/kits/bigquery-firestore-export/src/logs.ts
+++ b/kits/bigquery-firestore-export/src/logs.ts
@@ -140,6 +140,19 @@ export function partitioningFieldRemovalAttempted(
   });
 }
 
+export function linkedTransferConfigMissing(name: string): void {
+  logger.error(
+    "The scheduled query named by TRANSFER_CONFIG_NAME does not exist, so nothing was linked. Set it to a scheduled query that exists in this project and redeploy, or clear it to have this deployment create its own.",
+    { name }
+  );
+}
+
+// The reason carries the remediation, and an Error passed as structured data
+// serialises to {}, so it goes in the message.
+export function partitioningFieldRemovalAborted(reason: string): void {
+  logger.error(`Stopped without updating the scheduled query. ${reason}`);
+}
+
 export function topicCreated(name: string): void {
   logger.info("Created Pub/Sub topic for transfer notifications", { name });
 }
diff --git a/kits/bigquery-firestore-export/tests/handlers.test.ts b/kits/bigquery-firestore-export/tests/handlers.test.ts
index 6e9cfcc1ac..e33115f91d 100644
--- a/kits/bigquery-firestore-export/tests/handlers.test.ts
+++ b/kits/bigquery-firestore-export/tests/handlers.test.ts
@@ -23,13 +23,23 @@ const mocks = vi.hoisted(() => ({
   getTransferConfig: vi.fn(),
   updateTransferConfig: vi.fn(),
   handleTransferRunMessage: vi.fn(),
+  linkedTransferConfigMissing: vi.fn(),
+  partitioningFieldRemovalAborted: vi.fn(),
 }));
 
-vi.mock("../src/dts", () => ({
-  createTransferConfig: mocks.createTransferConfig,
-  getTransferConfig: mocks.getTransferConfig,
-  updateTransferConfig: mocks.updateTransferConfig,
-}));
+// The error constants come from the real module so the handler's prefix match
+// is tested against the message the guard actually throws.
+vi.mock("../src/dts", async (importOriginal) => {
+  const actual = await importOriginal<typeof import("../src/dts")>();
+  return {
+    createTransferConfig: mocks.createTransferConfig,
+    getTransferConfig: mocks.getTransferConfig,
+    updateTransferConfig: mocks.updateTransferConfig,
+    PARTITIONING_FIELD_REMOVAL_ERROR: actual.PARTITIONING_FIELD_REMOVAL_ERROR,
+    PARTITIONING_FIELD_REMOVAL_ERROR_PREFIX:
+      actual.PARTITIONING_FIELD_REMOVAL_ERROR_PREFIX,
+  };
+});
 
 vi.mock("../src/helper", () => ({
   handleTransferRunMessage: mocks.handleTransferRunMessage,
@@ -41,10 +51,13 @@ vi.mock("../src/helper", () => ({
 vi.mock("../src/logs", () => ({
   complete: vi.fn(),
   error: vi.fn(),
+  linkedTransferConfigMissing: mocks.linkedTransferConfigMissing,
+  partitioningFieldRemovalAborted: mocks.partitioningFieldRemovalAborted,
   start: vi.fn(),
   topicCreated: vi.fn(),
 }));
 
+import { PARTITIONING_FIELD_REMOVAL_ERROR } from "../src/dts";
 import { handleUpsertTransferConfig } from "../src/handlers";
 
 const config = resolveConfig({
@@ -167,4 +180,70 @@ describe("handleUpsertTransferConfig", () => {
       ...linked,
     });
   });
+
+  test("reports a missing linked transfer config without retrying", async () => {
+    mocks.getTransferConfig.mockResolvedValue(null);
+    const { ctx, set } = makeContext({
+      transferConfigName: "projects/p/locations/us/transferConfigs/gone",
+    });
+
+    await expect(handleUpsertTransferConfig(ctx)).resolves.toBeUndefined();
+
+    expect(mocks.linkedTransferConfigMissing).toHaveBeenCalledWith(
+      "projects/p/locations/us/transferConfigs/gone"
+    );
+    expect(set).not.toHaveBeenCalled();
+  });
+
+  test("reports a rejected partitioning-field removal without retrying", async () => {
+    mocks.updateTransferConfig.mockRejectedValue(
+      new Error(PARTITIONING_FIELD_REMOVAL_ERROR)
+    );
+    const { ctx, set } = makeContext({
+      existing: {
+        empty: false,
+        docs: [
+          {
+            data: () => ({
+              name: "projects/p/locations/us/transferConfigs/config-1",
+            }),
+          },
+        ],
+      },
+    });
+
+    await expect(handleUpsertTransferConfig(ctx)).resolves.toBeUndefined();
+
+    expect(mocks.partitioningFieldRemovalAborted).toHaveBeenCalledWith(
+      PARTITIONING_FIELD_REMOVAL_ERROR
+    );
+    expect(set).not.toHaveBeenCalled();
+  });
+
+  test("rethrows any other update failure so the task retries", async () => {
+    mocks.updateTransferConfig.mockRejectedValue(
+      new Error(
+        "bigquerydatatransfer.googleapis.com is temporarily unavailable"
+      )
+    );
+    const { ctx, set } = makeContext({
+      existing: {
+        empty: false,
+        docs: [
+          {
+            data: () => ({
+              name: "projects/p/locations/us/transferConfigs/config-1",
+            }),
+          },
+        ],
+      },
+    });
+
+    await expect(handleUpsertTransferConfig(ctx)).rejects.toThrow(
+      "temporarily unavailable"
+    );
+
+    expect(mocks.partitioningFieldRemovalAborted).not.toHaveBeenCalled();
+    expect(set).not.toHaveBeenCalled();
+  });
 });