diff --git a/src/app/api/v1/batches/delete-completed/route.ts b/src/app/api/v1/batches/delete-completed/route.ts
index 0659253e09..af0c53b79c 100644
--- a/src/app/api/v1/batches/delete-completed/route.ts
+++ b/src/app/api/v1/batches/delete-completed/route.ts
@@ -19,7 +19,11 @@ export async function DELETE(request: Request) {
     );
   }
 
-  const result = deleteCompletedBatches();
+  // Scope the sweep to the caller's own batches, like the list/count siblings do.
+  // Only a dashboard session (apiKeyId === null) sweeps the whole instance —
+  // otherwise an ordinary inference key would delete every tenant's completed
+  // batches and null out their file contents (GHSA-wvxc-jp3v-5mg5).
+  const result = deleteCompletedBatches(scope.apiKeyId || undefined);
 
   return NextResponse.json(
     { deleted: true, deletedBatches: result.deletedBatches, deletedFiles: result.deletedFiles },
diff --git a/src/lib/db/batches.ts b/src/lib/db/batches.ts
index 268f8aa4a9..12d95e0251 100644
--- a/src/lib/db/batches.ts
+++ b/src/lib/db/batches.ts
@@ -411,15 +411,30 @@ export function deleteBatch(id: string): boolean {
   return result.changes > 0;
 }
 
-export function deleteCompletedBatches(): { deletedBatches: number; deletedFiles: number } {
+/**
+ * Delete completed batches and the files they reference.
+ *
+ * `apiKeyId` scopes the sweep to that key's own batches, exactly like
+ * `listBatches`/`countBatches`. Omitting it sweeps the whole instance and is
+ * reserved for an authenticated dashboard session — an ordinary inference key
+ * that reached this without its own id would otherwise delete every tenant's
+ * completed batches and null out their file contents (GHSA-wvxc-jp3v-5mg5).
+ */
+export function deleteCompletedBatches(apiKeyId?: string): {
+  deletedBatches: number;
+  deletedFiles: number;
+} {
   const db = getDbInstance();
 
-  // Collect unique file IDs from all completed batches
+  const ownershipClause = apiKeyId ? " AND api_key_id = ?" : "";
+  const ownershipArgs = apiKeyId ? [apiKeyId] : [];
+
+  // Collect unique file IDs from the completed batches in scope
   const rows = db
     .prepare(
-      "SELECT input_file_id, output_file_id, error_file_id FROM batches WHERE status = 'completed'"
+      `SELECT input_file_id, output_file_id, error_file_id FROM batches WHERE status = 'completed'${ownershipClause}`
     )
-    .all() as Array<{
+    .all(...ownershipArgs) as Array<{
     input_file_id: string | null;
     output_file_id: string | null;
     error_file_id: string | null;
@@ -442,9 +457,11 @@ export function deleteCompletedBatches(): { deletedBatches: number; deletedFiles
   }
 
   db.prepare(
-    "DELETE FROM batch_item_checkpoints WHERE batch_id IN (SELECT id FROM batches WHERE status = 'completed')"
-  ).run();
+    `DELETE FROM batch_item_checkpoints WHERE batch_id IN (SELECT id FROM batches WHERE status = 'completed'${ownershipClause})`
+  ).run(...ownershipArgs);
 
-  const result = db.prepare("DELETE FROM batches WHERE status = 'completed'").run();
+  const result = db
+    .prepare(`DELETE FROM batches WHERE status = 'completed'${ownershipClause}`)
+    .run(...ownershipArgs);
   return { deletedBatches: result.changes, deletedFiles };
 }
diff --git a/tests/unit/batches-delete-completed-ownership-wvxc.test.ts b/tests/unit/batches-delete-completed-ownership-wvxc.test.ts
new file mode 100644
index 0000000000..79daa2898c
--- /dev/null
+++ b/tests/unit/batches-delete-completed-ownership-wvxc.test.ts
@@ -0,0 +1,99 @@
+/**
+ * GHSA-wvxc-jp3v-5mg5 — DELETE /api/v1/batches/delete-completed dropped the
+ * ownership predicate that every sibling batch operation keeps.
+ *
+ * `listBatches(apiKeyId?)` / `countBatches(apiKeyId?)` take the caller's key and
+ * scope the SQL to `api_key_id = ?`, falling back to instance-wide only when the
+ * caller is an authenticated dashboard session (which passes `undefined`).
+ * `deleteCompletedBatches()` took no such argument, so any valid inference key —
+ * including one with `scopes: []` — deleted every completed batch on the instance
+ * and nulled the content of the files those batches referenced.
+ *
+ * These tests pin both halves of the contract: scoped deletion for a key, and the
+ * unchanged instance-wide sweep for the dashboard session.
+ */
+import { describe, it, after } from "node:test";
+import assert from "node:assert";
+import { createFile, getFile } from "@/lib/db/files";
+import { createBatch, getBatch, deleteCompletedBatches } from "@/lib/db/batches";
+import { resetDbInstance } from "@/lib/db/core";
+
+/** One completed batch owned by `apiKeyId`, with its input file. */
+function seedCompletedBatch(apiKeyId: string | null, label: string) {
+  const file = createFile({
+    bytes: 8,
+    filename: `${label}.jsonl`,
+    purpose: "batch",
+    content: Buffer.from(label),
+    apiKeyId,
+  });
+  const batch = createBatch({
+    endpoint: "/v1/chat/completions",
+    completionWindow: "24h",
+    inputFileId: file.id,
+    status: "completed",
+    apiKeyId,
+  });
+  return { file, batch };
+}
+
+describe("deleteCompletedBatches — ownership boundary (GHSA-wvxc-jp3v-5mg5)", () => {
+  after(() => {
+    resetDbInstance();
+  });
+
+  it("deletes only the caller's completed batches, never another key's", () => {
+    const attacker = seedCompletedBatch("key_attacker_wvxc", "wvxc-attacker");
+    const victim = seedCompletedBatch("key_victim_wvxc", "wvxc-victim");
+
+    const result = deleteCompletedBatches("key_attacker_wvxc");
+
+    assert.strictEqual(
+      getBatch(attacker.batch.id),
+      null,
+      "the caller's own completed batch should be deleted"
+    );
+    assert.ok(
+      getBatch(victim.batch.id),
+      "another key's completed batch must survive — this is the vulnerability"
+    );
+    assert.ok(
+      getFile(victim.file.id),
+      "another key's file content must not be cleared by a foreign caller"
+    );
+    assert.strictEqual(result.deletedBatches, 1, "only one batch belonged to the caller");
+  });
+
+  it("leaves a batch that is not completed alone, even when the caller owns it", () => {
+    const own = seedCompletedBatch("key_owner_wvxc", "wvxc-owner");
+    const inProgressFile = createFile({
+      bytes: 8,
+      filename: "wvxc-inprogress.jsonl",
+      purpose: "batch",
+      content: Buffer.from("running"),
+      apiKeyId: "key_owner_wvxc",
+    });
+    const inProgress = createBatch({
+      endpoint: "/v1/chat/completions",
+      completionWindow: "24h",
+      inputFileId: inProgressFile.id,
+      status: "in_progress",
+      apiKeyId: "key_owner_wvxc",
+    });
+
+    deleteCompletedBatches("key_owner_wvxc");
+
+    assert.strictEqual(getBatch(own.batch.id), null, "completed batch of the caller goes");
+    assert.ok(getBatch(inProgress.id), "an in-progress batch is never swept");
+  });
+
+  it("keeps the instance-wide sweep for a dashboard session (no apiKeyId)", () => {
+    const a = seedCompletedBatch("key_a_wvxc_global", "wvxc-global-a");
+    const b = seedCompletedBatch("key_b_wvxc_global", "wvxc-global-b");
+
+    deleteCompletedBatches();
+
+    assert.strictEqual(getBatch(a.batch.id), null, "session sweep clears every key");
+    assert.strictEqual(getBatch(b.batch.id), null, "session sweep clears every key");
+  });
+});