diff --git a/extensions/posthog-analytics/lib/trace-context.ts b/extensions/posthog-analytics/lib/trace-context.ts
index f8a3b7e168c..91e948dd98a 100644
--- a/extensions/posthog-analytics/lib/trace-context.ts
+++ b/extensions/posthog-analytics/lib/trace-context.ts
@@ -27,7 +27,7 @@ export class TraceContextManager {
 
   startTrace(sessionKey: string, runId: string): void {
     this.traces.set(sessionKey, {
-      traceId: randomUUID(),
+      traceId: sessionKey,
       sessionId: sessionKey,
       runId,
       startedAt: Date.now(),
diff --git a/src/telemetry/event-mappers.test.ts b/src/telemetry/event-mappers.test.ts
index b0dc8e63123..ad16f4f83a6 100644
--- a/src/telemetry/event-mappers.test.ts
+++ b/src/telemetry/event-mappers.test.ts
@@ -1,6 +1,6 @@
 import { describe, it, expect, beforeEach, vi } from "vitest";
 import { TraceContextManager } from "../../extensions/posthog-analytics/lib/trace-context.js";
-import { emitGeneration, emitToolSpan, emitTrace, emitCustomEvent, extractToolNamesFromMessages, extractUsageFromMessages, normalizeOutputForPostHog, buildTraceState } from "../../extensions/posthog-analytics/lib/event-mappers.js";
+import { emitGeneration, emitToolSpan, emitTrace, emitCustomEvent, extractToolNamesFromMessages, extractUsageFromMessages, normalizeOutputForPostHog, buildTraceState, extractInputMessages } from "../../extensions/posthog-analytics/lib/event-mappers.js";
 
 function createMockPostHog() {
   return {
@@ -131,6 +131,32 @@ describe("normalizeOutputForPostHog", () => {
   });
 });
 
+describe("extractInputMessages", () => {
+  it("extracts non-assistant messages from a conversation", () => {
+    const messages = [
+      { role: "system", content: "You are helpful" },
+      { role: "user", content: "What is 2+2?" },
+      { role: "assistant", content: "4" },
+      { role: "tool", name: "calc", content: "4" },
+    ];
+    const result = extractInputMessages(messages);
+    expect(result).toEqual([
+      { role: "system", content: "You are helpful" },
+      { role: "user", content: "What is 2+2?" },
+      { role: "tool", name: "calc", content: "4" },
+    ]);
+  });
+
+  it("returns undefined for non-array input", () => {
+    expect(extractInputMessages(null)).toBeUndefined();
+    expect(extractInputMessages(undefined)).toBeUndefined();
+  });
+
+  it("returns undefined when only assistant messages exist", () => {
+    expect(extractInputMessages([{ role: "assistant", content: "hi" }])).toBeUndefined();
+  });
+});
+
 describe("emitGeneration", () => {
   let ph: ReturnType<typeof createMockPostHog>;
   let traceCtx: TraceContextManager;
@@ -286,6 +312,45 @@ describe("emitGeneration", () => {
     emitGeneration(ph, traceCtx, "s", { durationMs: 5000 }, true);
     expect(ph.capture.mock.calls[0][0].properties.$ai_latency).toBe(5);
   });
+
+  it("includes user messages from event.messages in $ai_input even when trace.input is empty", () => {
+    traceCtx.startTrace("s", "r");
+
+    const messages = [
+      { role: "user", content: "what is this" },
+      { role: "assistant", content: "It's a config file." },
+    ];
+    emitGeneration(ph, traceCtx, "s", { messages }, false);
+
+    const input = ph.capture.mock.calls[0][0].properties.$ai_input;
+    expect(input).toEqual([{ role: "user", content: "what is this" }]);
+  });
+
+  it("prefers event.messages over trace.input for $ai_input", () => {
+    traceCtx.startTrace("s", "r");
+    traceCtx.setInput("s", [{ role: "system", content: "tool config" }], false);
+
+    const messages = [
+      { role: "user", content: "hello" },
+      { role: "assistant", content: "hi" },
+    ];
+    emitGeneration(ph, traceCtx, "s", { messages }, false);
+
+    const input = ph.capture.mock.calls[0][0].properties.$ai_input;
+    expect(input).toEqual([{ role: "user", content: "hello" }]);
+  });
+
+  it("falls back to trace.input when event.messages has no input messages", () => {
+    traceCtx.startTrace("s", "r");
+    traceCtx.setInput("s", [{ role: "user", content: "from trace" }], false);
+
+    emitGeneration(ph, traceCtx, "s", {
+      output: [{ role: "assistant", content: "reply" }],
+    }, false);
+
+    const input = ph.capture.mock.calls[0][0].properties.$ai_input;
+    expect(input).toEqual([{ role: "user", content: "from trace" }]);
+  });
 });
 
 describe("emitToolSpan", () => {
diff --git a/src/telemetry/trace-context.test.ts b/src/telemetry/trace-context.test.ts
index 5365d9de240..7c1d6642cfb 100644
--- a/src/telemetry/trace-context.test.ts
+++ b/src/telemetry/trace-context.test.ts
@@ -28,12 +28,13 @@ describe("TraceContextManager", () => {
 
   // ── Trace lifecycle (session-keyed) ──
 
-  it("generates a unique UUID traceId for each trace (ensures PostHog trace grouping)", () => {
+  it("uses sessionKey as traceId so feedback and generation events share the same trace", () => {
     ctx.startTrace("session-1", "run-1");
     ctx.startTrace("session-2", "run-2");
     const t1 = ctx.getTrace("session-1")!;
     const t2 = ctx.getTrace("session-2")!;
-    expect(t1.traceId).toMatch(/^[0-9a-f]{8}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{12}$/);
+    expect(t1.traceId).toBe("session-1");
+    expect(t2.traceId).toBe("session-2");
     expect(t1.traceId).not.toBe(t2.traceId);
   });