diff --git a/server/src/__tests__/decision-queues-routes.test.ts b/server/src/__tests__/decision-queues-routes.test.ts
index 3dce271bcd3..1c056b771c3 100644
--- a/server/src/__tests__/decision-queues-routes.test.ts
+++ b/server/src/__tests__/decision-queues-routes.test.ts
@@ -396,6 +396,38 @@ describeEmbeddedPostgres("decision queue routes", () => {
     expect(current[0]?.setByUserId).toBe("override-user");
   });
 
+  it("serializes concurrent partial triage updates without losing state or reusing a version", async () => {
+    const { companyId, issueId } = await seed();
+    const board = boardActor(companyId);
+    const [decideByResult, snoozeResult] = await Promise.all([
+      request(app(board))
+        .put(`/api/companies/${companyId}/decision-triage/review/${issueId}`)
+        .send({ decideBy: "today" }),
+      request(app(board))
+        .put(`/api/companies/${companyId}/decision-triage/review/${issueId}`)
+        .send({ snoozedUntil: "2026-08-03T12:00:00.000Z" }),
+    ]);
+
+    expect(decideByResult.status).toBe(200);
+    expect(snoozeResult.status).toBe(200);
+    expect([decideByResult.body.version, snoozeResult.body.version].sort()).toEqual([1, 2]);
+
+    const current = await request(app(board))
+      .get(`/api/companies/${companyId}/decision-triage/review/${issueId}`)
+      .expect(200);
+    expect(current.body).toMatchObject({
+      decideBy: "today",
+      snoozedUntil: "2026-08-03T12:00:00.000Z",
+      version: 2,
+    });
+    const events = await db.select().from(decisionTriageEvents).where(and(
+      eq(decisionTriageEvents.companyId, companyId),
+      eq(decisionTriageEvents.sourceKind, "review"),
+      eq(decisionTriageEvents.sourceId, issueId),
+    ));
+    expect(events.map((event) => event.details.version).sort()).toEqual([1, 2]);
+  });
+
   it("rejects task-bridge JWTs and returns the same 404 for missing and unauthorized sources", async () => {
     const { companyId, agentId, approvalId } = await seed();
     const bridge = {
diff --git a/server/src/services/decision-queues.ts b/server/src/services/decision-queues.ts
index e4af931716f..47398e12128 100644
--- a/server/src/services/decision-queues.ts
+++ b/server/src/services/decision-queues.ts
@@ -597,6 +597,8 @@ export function decisionQueueService(db: Db) {
       await requireSourceRead(db, input.authActor, input.companyId, input.sourceKind, input.sourceId);
       return db.transaction(async (tx) => {
         const txDb = tx as unknown as Db;
+        const lockKey = `decision-triage:${input.companyId}:${input.sourceKind}:${input.sourceId}`;
+        await txDb.execute(sql`select pg_advisory_xact_lock(hashtextextended(${lockKey}, 0))`);
         const current = await txDb.select().from(decisionTriage).where(and(
           eq(decisionTriage.companyId, input.companyId),
           eq(decisionTriage.sourceKind, input.sourceKind),