diff --git a/actions/setup/js/action_conclusion_otlp.cjs b/actions/setup/js/action_conclusion_otlp.cjs
index 8bdcb6e32f1..4cc83964639 100644
--- a/actions/setup/js/action_conclusion_otlp.cjs
+++ b/actions/setup/js/action_conclusion_otlp.cjs
@@ -26,7 +26,8 @@
  *                                   execution window rather than this step's overhead.
  *   GITHUB_AW_OTEL_TRACE_ID       – parent trace ID (set by action_setup_otlp.cjs)
  *   GITHUB_AW_OTEL_PARENT_SPAN_ID – parent span ID (set by action_setup_otlp.cjs)
- *   OTEL_EXPORTER_OTLP_ENDPOINT   – OTLP endpoint (no-op when not set)
+ *   OTEL_EXPORTER_OTLP_ENDPOINT   – OTLP endpoint (HTTP export skipped when not set;
+ *                                    JSONL mirror write is attempted regardless)
  *
  * Runtime files read (optional):
  *   /tmp/gh-aw/github_rate_limits.jsonl – GitHub API rate-limit log written by
@@ -50,10 +51,6 @@ const { getActionInput } = require("./action_input_utils.cjs");
  */
 async function run() {
   const endpoint = process.env.OTEL_EXPORTER_OTLP_ENDPOINT;
-  if (!endpoint) {
-    console.log("[otlp] OTEL_EXPORTER_OTLP_ENDPOINT not set, skipping conclusion span");
-    return;
-  }
 
   // Read the job-start timestamp written by action_setup_otlp so the conclusion
   // span duration covers the actual job execution window, not just this step's overhead.
@@ -62,10 +59,18 @@ async function run() {
 
   const jobName = getActionInput("JOB_NAME");
   const spanName = jobName ? `gh-aw.${jobName}.conclusion` : "gh-aw.job.conclusion";
-  console.log(`[otlp] sending conclusion span "${spanName}" to ${endpoint}`);
+
+  if (!endpoint) {
+    console.log("[otlp] OTEL_EXPORTER_OTLP_ENDPOINT not set, skipping OTLP export (will attempt JSONL mirror)");
+  } else {
+    console.log(`[otlp] sending conclusion span "${spanName}" to ${endpoint}`);
+  }
 
   await sendOtlpSpan.sendJobConclusionSpan(spanName, { startMs });
-  console.log(`[otlp] conclusion span sent`);
+
+  if (endpoint) {
+    console.log(`[otlp] conclusion span export attempted`);
+  }
 }
 
 module.exports = { run };
diff --git a/actions/setup/js/action_conclusion_otlp.test.cjs b/actions/setup/js/action_conclusion_otlp.test.cjs
index 7b414437076..efe7daeb4f0 100644
--- a/actions/setup/js/action_conclusion_otlp.test.cjs
+++ b/actions/setup/js/action_conclusion_otlp.test.cjs
@@ -68,17 +68,17 @@ describe("action_conclusion_otlp.cjs", () => {
   });
 
   describe("when OTEL_EXPORTER_OTLP_ENDPOINT is not set", () => {
-    it("should log that the endpoint is not set and skip span", async () => {
+    it("should log that OTLP export is skipped and JSONL mirror will be attempted", async () => {
       await run();
 
-      expect(console.log).toHaveBeenCalledWith("[otlp] OTEL_EXPORTER_OTLP_ENDPOINT not set, skipping conclusion span");
-      expect(mockSendJobConclusionSpan).not.toHaveBeenCalled();
+      expect(console.log).toHaveBeenCalledWith("[otlp] OTEL_EXPORTER_OTLP_ENDPOINT not set, skipping OTLP export (will attempt JSONL mirror)");
     });
 
-    it("should not call sendJobConclusionSpan", async () => {
+    it("should still call sendJobConclusionSpan for JSONL mirror", async () => {
       await run();
 
-      expect(mockSendJobConclusionSpan).not.toHaveBeenCalled();
+      expect(mockSendJobConclusionSpan).toHaveBeenCalledOnce();
+      expect(mockSendJobConclusionSpan).toHaveBeenCalledWith("gh-aw.job.conclusion", { startMs: undefined });
     });
   });
 
@@ -93,10 +93,10 @@ describe("action_conclusion_otlp.cjs", () => {
       expect(mockSendJobConclusionSpan).toHaveBeenCalledOnce();
     });
 
-    it("should log the conclusion span as sent", async () => {
+    it("should log the conclusion span export as attempted", async () => {
       await run();
 
-      expect(console.log).toHaveBeenCalledWith("[otlp] conclusion span sent");
+      expect(console.log).toHaveBeenCalledWith("[otlp] conclusion span export attempted");
     });
 
     it("should log the endpoint URL in the sending message", async () => {
diff --git a/actions/setup/js/send_otlp_span.cjs b/actions/setup/js/send_otlp_span.cjs
index f65bada1bf0..8c077000c20 100644
--- a/actions/setup/js/send_otlp_span.cjs
+++ b/actions/setup/js/send_otlp_span.cjs
@@ -310,12 +310,16 @@ function sanitizeOTLPPayload(payload) {
  *
  * @param {string} endpoint  - OTLP base URL (e.g. https://traces.example.com:4317)
  * @param {object} payload   - Serialisable OTLP JSON object
- * @param {{ maxRetries?: number, baseDelayMs?: number }} [opts]
+ * @param {{ maxRetries?: number, baseDelayMs?: number, skipJSONL?: boolean }} [opts]
  * @returns {Promise<void>}
  */
-async function sendOTLPSpan(endpoint, payload, { maxRetries = 2, baseDelayMs = 100 } = {}) {
+async function sendOTLPSpan(endpoint, payload, { maxRetries = 2, baseDelayMs = 100, skipJSONL = false } = {}) {
   // Mirror payload locally so it survives even when the collector is unreachable.
-  appendToOTLPJSONL(payload);
+  // Callers that already wrote the JSONL mirror pass skipJSONL: true to avoid a
+  // duplicate line.
+  if (!skipJSONL) {
+    appendToOTLPJSONL(payload);
+  }
 
   const url = endpoint.replace(/\/$/, "") + "/v1/traces";
   const extraHeaders = parseOTLPHeaders(process.env.OTEL_EXPORTER_OTLP_HEADERS || "");
@@ -463,11 +467,8 @@ async function sendJobSetupSpan(options = {}) {
   // scripts to establish the correct parent span context.
   const spanId = generateSpanId();
 
-  const endpoint = process.env.OTEL_EXPORTER_OTLP_ENDPOINT || "";
-  if (!endpoint) {
-    return { traceId, spanId };
-  }
-
+  // Build the full payload unconditionally so the JSONL mirror is always written,
+  // enabling artifact-based debugging even without a live OTLP collector.
   const startMs = options.startMs ?? nowMs();
   const endMs = nowMs();
 
@@ -525,7 +526,16 @@ async function sendJobSetupSpan(options = {}) {
     resourceAttributes,
   });
 
-  await sendOTLPSpan(endpoint, payload);
+  // Always mirror to JSONL — the artifact is useful even without a live collector.
+  appendToOTLPJSONL(payload);
+
+  const endpoint = process.env.OTEL_EXPORTER_OTLP_ENDPOINT || "";
+  if (!endpoint) {
+    return { traceId, spanId };
+  }
+
+  // Pass skipJSONL: true so sendOTLPSpan doesn't double-write the mirror.
+  await sendOTLPSpan(endpoint, payload, { skipJSONL: true });
   return { traceId, spanId };
 }
 
@@ -595,8 +605,11 @@ function readLastRateLimitEntry() {
  * setup action.  The span carries workflow metadata read from `aw_info.json`
  * and the effective token count from `GH_AW_EFFECTIVE_TOKENS`.
  *
- * This is a no-op when `OTEL_EXPORTER_OTLP_ENDPOINT` is not set.  All errors
- * are surfaced as `console.warn` messages and never re-thrown.
+ * The span payload is always built and mirrored to the local JSONL file so
+ * that it can be inspected via GitHub Actions artifacts without needing a live
+ * collector.  The HTTP export to the OTLP endpoint is skipped when
+ * `OTEL_EXPORTER_OTLP_ENDPOINT` is not set.  All errors are surfaced as
+ * `console.warn` messages and never re-thrown.
  *
  * Environment variables consumed:
  * - `OTEL_EXPORTER_OTLP_ENDPOINT`  – collector endpoint
@@ -623,11 +636,6 @@ function readLastRateLimitEntry() {
  * @returns {Promise<void>}
  */
 async function sendJobConclusionSpan(spanName, options = {}) {
-  const endpoint = process.env.OTEL_EXPORTER_OTLP_ENDPOINT || "";
-  if (!endpoint) {
-    return;
-  }
-
   const startMs = options.startMs ?? nowMs();
 
   // Read workflow metadata from aw_info.json (written by the agent job setup step).
@@ -765,7 +773,16 @@ async function sendJobConclusionSpan(spanName, options = {}) {
     statusMessage,
   });
 
-  await sendOTLPSpan(endpoint, payload);
+  // Always mirror to JSONL — the artifact is useful even without a live collector.
+  appendToOTLPJSONL(payload);
+
+  const endpoint = process.env.OTEL_EXPORTER_OTLP_ENDPOINT || "";
+  if (!endpoint) {
+    return;
+  }
+
+  // Pass skipJSONL: true so sendOTLPSpan doesn't double-write the mirror.
+  await sendOTLPSpan(endpoint, payload, { skipJSONL: true });
 }
 
 module.exports = {
diff --git a/actions/setup/js/send_otlp_span.test.cjs b/actions/setup/js/send_otlp_span.test.cjs
index 762f9c8e228..3b7505ce477 100644
--- a/actions/setup/js/send_otlp_span.test.cjs
+++ b/actions/setup/js/send_otlp_span.test.cjs
@@ -657,6 +657,14 @@ describe("sendOTLPSpan JSONL mirror", () => {
 
     warnSpy.mockRestore();
   });
+
+  it("skips JSONL mirror when skipJSONL is true", async () => {
+    const payload = { resourceSpans: [{ note: "skip-test" }] };
+    await sendOTLPSpan("https://traces.example.com", payload, { skipJSONL: true });
+
+    expect(appendSpy).not.toHaveBeenCalled();
+    expect(fetch).toHaveBeenCalledOnce();
+  });
 });
 
 // ---------------------------------------------------------------------------
@@ -838,6 +846,15 @@ describe("sendJobSetupSpan", () => {
     expect(fetch).not.toHaveBeenCalled();
   });
 
+  it("writes JSONL mirror even when OTEL_EXPORTER_OTLP_ENDPOINT is not set", async () => {
+    await sendJobSetupSpan();
+    expect(appendSpy).toHaveBeenCalledOnce();
+    const [filePath, content] = appendSpy.mock.calls[0];
+    expect(filePath).toBe(OTEL_JSONL_PATH);
+    const payload = JSON.parse(content.trim());
+    expect(payload).toHaveProperty("resourceSpans");
+  });
+
   it("returns the same trace ID when called with INPUT_TRACE_ID and no endpoint", async () => {
     process.env.INPUT_TRACE_ID = "a".repeat(32);
     const { traceId } = await sendJobSetupSpan();
@@ -1360,9 +1377,14 @@ describe("sendJobConclusionSpan", () => {
     appendSpy.mockRestore();
   });
 
-  it("is a no-op when OTEL_EXPORTER_OTLP_ENDPOINT is not set", async () => {
+  it("skips OTLP export but writes JSONL mirror when OTEL_EXPORTER_OTLP_ENDPOINT is not set", async () => {
     await sendJobConclusionSpan("gh-aw.job.conclusion");
     expect(fetch).not.toHaveBeenCalled();
+    expect(appendSpy).toHaveBeenCalledOnce();
+    const [filePath, content] = appendSpy.mock.calls[0];
+    expect(filePath).toBe(OTEL_JSONL_PATH);
+    const payload = JSON.parse(content.trim());
+    expect(payload).toHaveProperty("resourceSpans");
   });
 
   it("sends a span with the given span name", async () => {