diff --git a/CHANGELOG.md b/CHANGELOG.md
index 31610622..9389d1ab 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -21,6 +21,14 @@ Contributors: add user-facing changes under **[Unreleased]** in your PR to `deve
 
 ---
 
+## [1.17.1] - 2026-07-19
+
+### Fixed
+
+- **Concurrent error-group create race** — `findOrCreateErrorGroup` now handles Prisma P2002 on unique `(project_id, fingerprint)` by re-fetching the existing group and incrementing occurrences (`isNew: false`), so concurrent `POST /ingest/error` no longer 500s ([#599](https://github.com/Telemetry-Tracker/telemetry-tracker/pull/599))
+
+---
+
 ## [1.17.0] - 2026-07-19
 
 ### Added
diff --git a/apps/api/src/generated/api-version.ts b/apps/api/src/generated/api-version.ts
index 45773dfd..173a9c43 100644
--- a/apps/api/src/generated/api-version.ts
+++ b/apps/api/src/generated/api-version.ts
@@ -1,2 +1,2 @@
 /** Generated at build time from CHANGELOG (/Users/unjica/Documents/GitHub/telemetry-tracker/CHANGELOG.md). Do not edit manually. */
-export const API_VERSION = "1.17.0";
+export const API_VERSION = "1.17.1";
diff --git a/apps/api/src/services/errors.test.ts b/apps/api/src/services/errors.test.ts
index 24835365..698eb63a 100644
--- a/apps/api/src/services/errors.test.ts
+++ b/apps/api/src/services/errors.test.ts
@@ -60,4 +60,66 @@ describe("findOrCreateErrorGroup", () => {
       })
     );
   });
+
+  it("on create race (P2002), re-fetches existing group and returns isNew false", async () => {
+    prisma.errorGroup.findUnique
+      .mockResolvedValueOnce(null)
+      .mockResolvedValueOnce({
+        id: "eg-winner",
+        message: "boom",
+        app: "web",
+        environment: "production",
+      });
+    prisma.errorGroup.create.mockRejectedValueOnce(
+      Object.assign(new Error("Unique constraint failed"), { code: "P2002" })
+    );
+    prisma.errorGroup.update.mockResolvedValueOnce({});
+
+    const result = await findOrCreateErrorGroup(prisma as never, {
+      projectId: "p1",
+      fingerprint: "fp",
+      message: "boom",
+      top_stack: "at foo",
+      app: "web",
+      environment: "production",
+      release: "1.2.0",
+    });
+
+    expect(result).toEqual({
+      group: {
+        id: "eg-winner",
+        message: "boom",
+        app: "web",
+        environment: "production",
+      },
+      isNew: false,
+    });
+    expect(prisma.errorGroup.update).toHaveBeenCalledWith(
+      expect.objectContaining({
+        where: { id: "eg-winner" },
+        data: expect.objectContaining({
+          occurrences: { increment: 1 },
+          release: "1.2.0",
+        }),
+      })
+    );
+  });
+
+  it("re-throws non-P2002 create errors", async () => {
+    prisma.errorGroup.findUnique.mockResolvedValueOnce(null);
+    prisma.errorGroup.create.mockRejectedValueOnce(
+      Object.assign(new Error("db down"), { code: "P1001" })
+    );
+
+    await expect(
+      findOrCreateErrorGroup(prisma as never, {
+        projectId: "p1",
+        fingerprint: "fp",
+        message: "boom",
+        top_stack: "at foo",
+        app: "web",
+      })
+    ).rejects.toMatchObject({ code: "P1001" });
+    expect(prisma.errorGroup.update).not.toHaveBeenCalled();
+  });
 });
diff --git a/apps/api/src/services/errors.ts b/apps/api/src/services/errors.ts
index 008fafd0..a91c90f7 100644
--- a/apps/api/src/services/errors.ts
+++ b/apps/api/src/services/errors.ts
@@ -5,6 +5,54 @@ export function computeFingerprint(message: string, stack?: string): string {
   return `${message}\n${firstLine}`;
 }
 
+function isUniqueViolation(e: unknown): boolean {
+  return (
+    typeof e === "object" &&
+    e !== null &&
+    "code" in e &&
+    (e as { code: string }).code === "P2002"
+  );
+}
+
+type ErrorGroupRow = {
+  id: string;
+  message: string;
+  app: string;
+  environment: string | null;
+};
+
+async function touchExistingErrorGroup(
+  prisma: PrismaClient,
+  existing: ErrorGroupRow,
+  data: {
+    environment?: string | null;
+    release?: string | null;
+    platform?: string | null;
+  }
+): Promise<{ group: ErrorGroupRow; isNew: false }> {
+  await prisma.errorGroup.update({
+    where: { id: existing.id },
+    data: {
+      occurrences: { increment: 1 },
+      last_seen: new Date(),
+      ...(data.environment != null && data.environment !== ""
+        ? { environment: data.environment }
+        : {}),
+      ...(data.release != null && data.release !== "" ? { release: data.release } : {}),
+      ...(data.platform != null && data.platform !== "" ? { platform: data.platform } : {}),
+    },
+  });
+  return {
+    group: {
+      id: existing.id,
+      message: existing.message,
+      app: existing.app,
+      environment: existing.environment,
+    },
+    isNew: false,
+  };
+}
+
 export async function findOrCreateErrorGroup(
   prisma: PrismaClient,
   data: {
@@ -17,7 +65,7 @@ export async function findOrCreateErrorGroup(
     release?: string | null;
     platform?: string | null;
   }
-): Promise<{ group: { id: string; message: string; app: string; environment: string | null }; isNew: boolean }> {
+): Promise<{ group: ErrorGroupRow; isNew: boolean }> {
   const existing = await prisma.errorGroup.findUnique({
     where: {
       project_id_fingerprint: {
@@ -27,48 +75,43 @@ export async function findOrCreateErrorGroup(
     },
   });
   if (existing) {
-    await prisma.errorGroup.update({
-      where: { id: existing.id },
+    return touchExistingErrorGroup(prisma, existing, data);
+  }
+  try {
+    const created = await prisma.errorGroup.create({
       data: {
-        occurrences: { increment: 1 },
-        last_seen: new Date(),
-        ...(data.environment != null && data.environment !== ""
-          ? { environment: data.environment }
-          : {}),
-        ...(data.release != null && data.release !== "" ? { release: data.release } : {}),
-        ...(data.platform != null && data.platform !== "" ? { platform: data.platform } : {}),
+        project_id: data.projectId,
+        fingerprint: data.fingerprint,
+        message: data.message,
+        top_stack: data.top_stack,
+        app: data.app,
+        environment: data.environment ?? null,
+        release: data.release ?? null,
+        platform: data.platform ?? null,
+        occurrences: 1,
       },
     });
     return {
       group: {
-        id: existing.id,
-        message: existing.message,
-        app: existing.app,
-        environment: existing.environment,
+        id: created.id,
+        message: created.message,
+        app: created.app,
+        environment: created.environment,
       },
-      isNew: false,
+      isNew: true,
     };
+  } catch (e) {
+    // Concurrent ingest: another request created the same (project_id, fingerprint).
+    if (!isUniqueViolation(e)) throw e;
+    const raced = await prisma.errorGroup.findUnique({
+      where: {
+        project_id_fingerprint: {
+          project_id: data.projectId,
+          fingerprint: data.fingerprint,
+        },
+      },
+    });
+    if (!raced) throw e;
+    return touchExistingErrorGroup(prisma, raced, data);
   }
-  const created = await prisma.errorGroup.create({
-    data: {
-      project_id: data.projectId,
-      fingerprint: data.fingerprint,
-      message: data.message,
-      top_stack: data.top_stack,
-      app: data.app,
-      environment: data.environment ?? null,
-      release: data.release ?? null,
-      platform: data.platform ?? null,
-      occurrences: 1,
-    },
-  });
-  return {
-    group: {
-      id: created.id,
-      message: created.message,
-      app: created.app,
-      environment: created.environment,
-    },
-    isNew: true,
-  };
 }