diff --git a/src/__tests__/external-id-stability-guard.test.ts b/src/__tests__/external-id-stability-guard.test.ts
index 4e59506c5..47f942f04 100644
--- a/src/__tests__/external-id-stability-guard.test.ts
+++ b/src/__tests__/external-id-stability-guard.test.ts
@@ -44,6 +44,19 @@ function read(rel: string): string {
   return readFileSync(join(SRC, rel), "utf8");
 }
 
+/**
+ * The file with its `import … from "…";` statements removed.
+ *
+ * A guard that greps the raw source cannot tell "this file APPLIES the
+ * check" from "this file merely imports it" — deleting the call while
+ * leaving the import would slip straight through. Every usage assertion
+ * below therefore runs against the body, and the module import is
+ * asserted separately where it matters.
+ */
+function body(rel: string): string {
+  return read(rel).replace(/import\s+[\s\S]*?from\s+"[^"]+";/g, "");
+}
+
 /**
  * A REQUEST-side declaration of a client-supplied external identifier:
  * `externalId: z.…` / `externalSourceId: z.…` in a Zod object shape.
@@ -106,11 +119,10 @@ describe("every client-supplied external id routes through the stability floor",
         return;
       }
 
-      const source = read(rel);
       const usesFieldCheck =
-        source.includes(VALIDATOR_MODULE) &&
-        source.includes("assertStableExternalId");
-      const marksPerEntry = MARKER.test(source);
+        read(rel).includes(VALIDATOR_MODULE) &&
+        body(rel).includes("assertStableExternalId");
+      const marksPerEntry = MARKER.test(read(rel));
       expect(
         usesFieldCheck || marksPerEntry,
         `${rel} declares a client-supplied external id but neither applies ` +
@@ -134,7 +146,7 @@ describe("every client-supplied external id routes through the stability floor",
           target.startsWith("src/"),
           `${rel}: marker target "${target}" must be a repo-root-relative src/ path`,
         ).toBe(true);
-        const checker = read(target.replace(/^src\//, ""));
+        const checker = body(target.replace(/^src\//, ""));
         expect(
           checker.includes("classifyExternalId"),
           `${rel} points its per-entry marker at ${target}, but that file never calls classifyExternalId.`,
@@ -158,7 +170,7 @@ describe("the batch surfaces refuse per entry, never whole-batch", () => {
   ];
 
   it.each(BATCH_ROUTES)("%s classifies each entry itself", (rel) => {
-    const source = read(rel);
+    const source = body(rel);
     expect(source).toContain("classifyExternalId");
     expect(source).toContain("unstableExternalIdMeta");
   });
@@ -168,7 +180,7 @@ describe("the batch surfaces refuse per entry, never whole-batch", () => {
     (rel) => {
       // The JSON importer has no per-entry status envelope — it reports a
       // skipped COUNT — so it is the one batch surface without the code.
-      expect(read(rel)).toContain("UNSTABLE_EXTERNAL_ID_REASON");
+      expect(body(rel)).toContain("UNSTABLE_EXTERNAL_ID_REASON");
     },
   );
 });
diff --git a/src/app/api/mood-entries/bulk/__tests__/route.test.ts b/src/app/api/mood-entries/bulk/__tests__/route.test.ts
index bfbe3f9b6..081284866 100644
--- a/src/app/api/mood-entries/bulk/__tests__/route.test.ts
+++ b/src/app/api/mood-entries/bulk/__tests__/route.test.ts
@@ -461,6 +461,92 @@ describe("POST /api/mood-entries/bulk — structured tagKeys (v1.12.0)", () => {
   });
 });
 
+describe("POST /api/mood-entries/bulk — unstable external ids", () => {
+  /**
+   * `(userId, source, externalId)` dedups only while the id is stable
+   * across client launches. A per-process value — an object description
+   * carrying a memory address — never matches its own earlier row, so
+   * every re-post mints another entry. The refusal is PER ENTRY: a client
+   * draining an offline queue must not lose its good rows to one bad one.
+   */
+  beforeEach(() => {
+    vi.mocked(prisma.moodEntry.findMany).mockResolvedValue([]);
+    vi.mocked(prisma.moodEntry.upsert).mockResolvedValue({
+      id: "entry-1",
+    } as never);
+  });
+
+  it("skips the offending entry and still writes the rest of the batch", async () => {
+    const res = await POST(
+      postReq({
+        entries: [
+          {
+            mood: "GUT",
+            moodLoggedAt: "2026-05-16T08:00:00.000Z",
+            externalId: "8AD2A9CB-3F0C-4E4D-9C1E-4B7E2A1D6F30",
+          },
+          {
+            mood: "OKAY",
+            moodLoggedAt: "2026-05-16T09:00:00.000Z",
+            externalId: "<HKHealthConceptIdentifier: 0x12568db80>",
+          },
+          {
+            mood: "SUPER_GUT",
+            moodLoggedAt: "2026-05-16T10:00:00.000Z",
+            externalId: "0xdeadbeef",
+          },
+        ],
+      }),
+    );
+    expect(res.status).toBe(200);
+    const body = (await res.json()) as {
+      data: {
+        processed: number;
+        inserted: number;
+        skipped: Array<{ index: number; reason: string }>;
+        entries: Array<{
+          index: number;
+          status: string;
+          reason?: string;
+          externalId?: string;
+        }>;
+      };
+    };
+    expect(body.data.processed).toBe(3);
+    expect(body.data.entries[0].status).toBe("inserted");
+    expect(body.data.entries[1]).toMatchObject({
+      index: 1,
+      status: "skipped",
+      reason: "unstable_external_id",
+      externalId: "<HKHealthConceptIdentifier: 0x12568db80>",
+    });
+    expect(body.data.entries[2]).toMatchObject({
+      index: 2,
+      status: "skipped",
+      reason: "unstable_external_id",
+    });
+    expect(body.data.skipped).toEqual([
+      { index: 1, reason: "unstable_external_id" },
+      { index: 2, reason: "unstable_external_id" },
+    ]);
+    // Only the good entry reached the writer.
+    expect(prisma.moodEntry.upsert).toHaveBeenCalledTimes(1);
+  });
+
+  it("leaves an entry without an externalId untouched", async () => {
+    const res = await POST(
+      postReq({
+        entries: [{ mood: "OKAY", moodLoggedAt: "2026-05-16T08:00:00.000Z" }],
+      }),
+    );
+    expect(res.status).toBe(200);
+    const body = (await res.json()) as {
+      data: { entries: Array<{ status: string }> };
+    };
+    expect(body.data.entries[0].status).toBe("inserted");
+  });
+});
+
 describe("POST /api/mood-entries/bulk — tombstone suppression", () => {
   it("keeps a tombstoned match deleted: true no-op reported as duplicate", async () => {
     // A soft-deleted row under the batched pre-read: the sync feed already