diff --git a/internal-packages/run-engine/src/engine/systems/waitpointSystem.ts b/internal-packages/run-engine/src/engine/systems/waitpointSystem.ts
index a0d5b733494..b1143366aa0 100644
--- a/internal-packages/run-engine/src/engine/systems/waitpointSystem.ts
+++ b/internal-packages/run-engine/src/engine/systems/waitpointSystem.ts
@@ -1,5 +1,5 @@
 import { timeoutError, tryCatch } from "@trigger.dev/core/v3";
-import { WaitpointId } from "@trigger.dev/core/v3/isomorphic";
+import { UnclassifiableRunId, WaitpointId } from "@trigger.dev/core/v3/isomorphic";
 import type {
   PrismaClientOrTransaction,
   TaskRun,
@@ -91,11 +91,24 @@ export class WaitpointSystem {
     try {
       store = await this.$.runStore.forWaitpointCompletion(id, { routeKind: "MANUAL" });
     } catch (error) {
-      this.$.logger.error("completeWaitpoint: unclassifiable waitpointId", {
+      // Only a genuine id-classification failure should become UnclassifiableWaitpointId.
+      // forWaitpointCompletion also probes the DB to resolve the owning store, so a transient
+      // database/infra error (e.g. can't reach the database) can surface here too. Those MUST
+      // bubble up unchanged so they keep their original type, retryability, and error grouping
+      // instead of being mislabelled as an unclassifiable id.
+      if (error instanceof UnclassifiableRunId) {
+        this.$.logger.error("completeWaitpoint: unclassifiable waitpointId", {
+          waitpointId: id,
+          error,
+        });
+        throw new UnclassifiableWaitpointId(id, { cause: error });
+      }
+
+      this.$.logger.error("completeWaitpoint: error resolving waitpoint store", {
         waitpointId: id,
         error,
       });
-      throw new UnclassifiableWaitpointId(id, { cause: error });
+      throw error;
     }
 
     // 1. Complete the Waitpoint (if not completed)
diff --git a/internal-packages/run-engine/src/engine/tests/completeWaitpointErrorClassification.test.ts b/internal-packages/run-engine/src/engine/tests/completeWaitpointErrorClassification.test.ts
new file mode 100644
index 00000000000..bc6ebd5f8db
--- /dev/null
+++ b/internal-packages/run-engine/src/engine/tests/completeWaitpointErrorClassification.test.ts
@@ -0,0 +1,68 @@
+// completeWaitpoint's store-selection guard must only turn a genuine id-classification
+// failure into UnclassifiableWaitpointId. forWaitpointCompletion also probes the DB to
+// resolve the owning store, so a transient database/infra error can surface from the same
+// call — and those must bubble up UNCHANGED (keeping their original type, retryability, and
+// error grouping) rather than being mislabelled as an unclassifiable id.
+//
+// This is a hermetic unit test: the error is thrown on the very first line of
+// completeWaitpoint (runStore.forWaitpointCompletion), before any snapshot/enqueue work,
+// so we can drive it with a minimal SystemResources and a fake runStore — no DB, no Redis.
+import { UnclassifiableRunId } from "@trigger.dev/core/v3/isomorphic";
+import { expect } from "vitest";
+import { UnclassifiableWaitpointId } from "../errors.js";
+import type { SystemResources } from "../systems/systems.js";
+import { WaitpointSystem } from "../systems/waitpointSystem.js";
+
+function createWaitpointSystem(forWaitpointCompletion: () => Promise<never>) {
+  const runStore = { forWaitpointCompletion };
+
+  const resources = {
+    runStore,
+    logger: {
+      error: vi.fn(),
+      warn: vi.fn(),
+      info: vi.fn(),
+      debug: vi.fn(),
+    },
+  } as unknown as SystemResources;
+
+  return new WaitpointSystem({
+    resources,
+    // Never reached on the store-resolution error path.
+    executionSnapshotSystem: {} as any,
+    enqueueSystem: {} as any,
+  });
+}
+
+describe("completeWaitpoint store-resolution error classification", () => {
+  it("rethrows a transient database error unchanged (never wraps it as UnclassifiableWaitpointId)", async () => {
+    const dbError = new Error("Can't reach database server at db:5432");
+    const waitpointSystem = createWaitpointSystem(() => Promise.reject(dbError));
+
+    // The original error bubbles up as-is...
+    await expect(waitpointSystem.completeWaitpoint({ id: "waitpoint_transient" })).rejects.toBe(
+      dbError
+    );
+    // ...and is NOT relabelled as a classification failure.
+    await expect(
+      waitpointSystem.completeWaitpoint({ id: "waitpoint_transient" })
+    ).rejects.not.toBeInstanceOf(UnclassifiableWaitpointId);
+  });
+
+  it("wraps a genuine UnclassifiableRunId as UnclassifiableWaitpointId with the original as cause", async () => {
+    const waitpointId = "waitpoint_unclassifiable";
+    const classificationError = new UnclassifiableRunId(waitpointId);
+    const waitpointSystem = createWaitpointSystem(() => Promise.reject(classificationError));
+
+    await expect(waitpointSystem.completeWaitpoint({ id: waitpointId })).rejects.toBeInstanceOf(
+      UnclassifiableWaitpointId
+    );
+
+    const caught = (await waitpointSystem
+      .completeWaitpoint({ id: waitpointId })
+      .catch((error: unknown) => error)) as UnclassifiableWaitpointId;
+    expect(caught).toBeInstanceOf(UnclassifiableWaitpointId);
+    expect(caught.waitpointId).toBe(waitpointId);
+    expect(caught.cause).toBe(classificationError);
+  });
+});