diff --git a/changelog.d/fixes/13597-calllogs-worker-error-detail.md b/changelog.d/fixes/13597-calllogs-worker-error-detail.md
new file mode 100644
index 0000000000..19c50b3118
--- /dev/null
+++ b/changelog.d/fixes/13597-calllogs-worker-error-detail.md
@@ -0,0 +1 @@
+- **fix(usage):** the call-logs artifact worker's failure warning now includes the underlying error's message/code instead of the generic "detail omitted" — a crashed or non-zero-exit worker was previously undiagnosable in the logs (#13597) — thanks @afonsoft
diff --git a/src/lib/usage/callLogArtifactWriter.ts b/src/lib/usage/callLogArtifactWriter.ts
index 7cd8452340..64966afa04 100644
--- a/src/lib/usage/callLogArtifactWriter.ts
+++ b/src/lib/usage/callLogArtifactWriter.ts
@@ -116,8 +116,15 @@ function warnRateLimited(message: string): void {
   console.warn(message);
 }
 
-function failOpen(warn = false): void {
-  if (warn) warnRateLimited("[callLogs] Call-log artifact worker failed; detail omitted.");
+function describeFailureDetail(detail: unknown): string {
+  if (detail instanceof Error) return `${detail.name}: ${detail.message}`;
+  return String(detail ?? "unknown error");
+}
+
+function failOpen(warn = false, detail?: unknown): void {
+  if (warn) {
+    warnRateLimited(`[callLogs] Call-log artifact worker failed: ${describeFailureDetail(detail)}`);
+  }
   const failed = active ? [active, ...queue] : [...queue];
   active = null;
   queue.length = 0;
@@ -126,10 +133,24 @@ function failOpen(warn = false): void {
   notifyCloseWaiters();
 }
 
+let workerFileOverride: { workerFile: string; execArgv: string[] } | null = null;
+
+/**
+ * Test-only hook: force the next ensureWorker() call to spawn an arbitrary worker
+ * script/execArgv instead of the real callLogArtifactWorker file. Lets regression tests
+ * trigger a genuine worker_threads `error`/`exit` event without editing the production
+ * worker script. Never called from production code paths.
+ */
+export function __setCallLogWorkerOverrideForTests(
+  override: { workerFile: string; execArgv: string[] } | null
+): void {
+  workerFileOverride = override;
+}
+
 function ensureWorker(): Worker {
   if (worker) return worker;
 
-  const { workerFile, execArgv } = resolveCallLogArtifactWorker();
+  const { workerFile, execArgv } = workerFileOverride ?? resolveCallLogArtifactWorker();
   // Reflect.construct keeps Next/Turbopack from interpreting the runtime-selected
   // worker path as a build-time glob and tracing tens of thousands of unrelated files.
   const created = Reflect.construct(Worker, [pathToFileURL(workerFile), { execArgv }]) as Worker;
@@ -141,12 +162,12 @@ function ensureWorker(): Worker {
     completed.resolve(reply.result);
     pump();
   });
-  created.on("error", () => failOpen(true));
-  created.on("messageerror", () => failOpen(true));
+  created.on("error", (err) => failOpen(true, err));
+  created.on("messageerror", (err) => failOpen(true, err));
   created.on("exit", (code) => {
     if (worker !== created) return;
     worker = null;
-    if (code !== 0 || active) failOpen(true);
+    if (code !== 0 || active) failOpen(true, new Error(`worker exited with code ${code}`));
   });
   return created;
 }
@@ -168,8 +189,8 @@ function pump(): void {
       artifact: next.artifact,
       environment: next.environment,
     });
-  } catch {
-    failOpen(true);
+  } catch (err) {
+    failOpen(true, err);
   }
 }
 
diff --git a/tests/unit/issue-13597-calllogs-worker-error-detail.test.ts b/tests/unit/issue-13597-calllogs-worker-error-detail.test.ts
new file mode 100644
index 0000000000..8f6f770b73
--- /dev/null
+++ b/tests/unit/issue-13597-calllogs-worker-error-detail.test.ts
@@ -0,0 +1,99 @@
+import test from "node:test";
+import assert from "node:assert/strict";
+import fs from "node:fs";
+import os from "node:os";
+import path from "node:path";
+
+// Regression test for GitHub issue #13597 (claim A): the callLogs artifact worker's
+// failOpen() only ever logged a hardcoded "detail omitted" string — the real Error from
+// the worker's `error`/`messageerror` events (and the exit code from a non-zero `exit`)
+// were read and then discarded before warnRateLimited() was called, making the failure
+// undiagnosable on a live system.
+//
+// This test forces a REAL worker_threads crash (a worker script that throws
+// synchronously at import time) via the `__setCallLogWorkerOverrideForTests` test-only
+// hook, so callLogArtifactWriter.ts's actual `worker.on("error", ...)` handler fires with
+// a genuine Error object. It then asserts the resulting console.warn call carries that
+// error's message. On the pre-fix code this assertion is RED: the only thing ever logged
+// is the generic "detail omitted" string, with no trace of the injected error text.
+
+const TEST_DATA_DIR = fs.mkdtempSync(path.join(os.tmpdir(), "omniroute-issue-13597-"));
+process.env.DATA_DIR = TEST_DATA_DIR;
+
+const { writeCallArtifactAsync, closeCallLogArtifactWriter, __setCallLogWorkerOverrideForTests } =
+  await import("../../src/lib/usage/callLogArtifactWriter.ts");
+
+const CRASH_MESSAGE = "probe-13597-worker-init-crash";
+const crashWorkerFile = path.join(TEST_DATA_DIR, "crash-worker.mjs");
+fs.writeFileSync(crashWorkerFile, `throw new Error(${JSON.stringify(CRASH_MESSAGE)});\n`);
+
+test.after(async () => {
+  __setCallLogWorkerOverrideForTests(null);
+  await closeCallLogArtifactWriter(0);
+  fs.rmSync(TEST_DATA_DIR, { recursive: true, force: true, maxRetries: 5, retryDelay: 100 });
+});
+
+function buildArtifact(id: string) {
+  return {
+    schemaVersion: 5 as const,
+    summary: {
+      id,
+      timestamp: "2026-09-15T00:00:00.000Z",
+      method: "POST",
+      path: "/v1/chat/completions",
+      status: 200,
+      model: "test-model",
+      requestedModel: null,
+      provider: "test-provider",
+      account: "test-account",
+      connectionId: null,
+      duration: 10,
+      tokens: {
+        in: 1,
+        out: 2,
+        cacheRead: null,
+        cacheWrite: null,
+        reasoning: null,
+        compressed: null,
+      },
+      requestType: "chat",
+      sourceFormat: "openai",
+      targetFormat: "openai",
+      apiKeyId: null,
+      apiKeyName: null,
+      comboName: null,
+      comboStepId: null,
+      comboExecutionKey: null,
+    },
+    requestBody: {},
+    responseBody: { content: "unreachable — worker never comes up" },
+    error: null,
+  };
+}
+
+test("issue #13597: a crashed call-log worker logs the underlying error detail, not 'detail omitted'", async () => {
+  __setCallLogWorkerOverrideForTests({ workerFile: crashWorkerFile, execArgv: [] });
+
+  const originalWarn = console.warn;
+  const warnings: string[] = [];
+  console.warn = (...args: unknown[]) => {
+    warnings.push(args.map(String).join(" "));
+  };
+
+  try {
+    const result = await writeCallArtifactAsync(buildArtifact("issue-13597-crash-1"));
+    assert.equal(result, null); // fails open — existing, correct behavior
+
+    const failureWarnings = warnings.filter((w) => w.includes("[callLogs]"));
+    assert.ok(failureWarnings.length > 0, "expected a [callLogs] warning to be logged");
+
+    const detailed = failureWarnings.some((w) => w.includes(CRASH_MESSAGE));
+    assert.ok(
+      detailed,
+      `expected a [callLogs] warning to include the underlying error detail ` +
+        `("${CRASH_MESSAGE}"), got: ${JSON.stringify(failureWarnings)}`
+    );
+  } finally {
+    console.warn = originalWarn;
+  }
+});