diff --git a/packages/agents-a365-observability/src/tracing/middleware/BaggageBuilder.ts b/packages/agents-a365-observability/src/tracing/middleware/BaggageBuilder.ts
index 19b6f297..fc2e1345 100644
--- a/packages/agents-a365-observability/src/tracing/middleware/BaggageBuilder.ts
+++ b/packages/agents-a365-observability/src/tracing/middleware/BaggageBuilder.ts
@@ -99,6 +99,16 @@ export class BaggageBuilder {
     return this;
   }
 
+  /**
+   * Set the session ID baggage value.
+   * @param value The session ID
+   * @returns Self for method chaining
+   */
+  sessionId(value: string): BaggageBuilder {
+    this.set(OpenTelemetryConstants.SESSION_ID_KEY, value);
+    return this;
+  }
+
   /**
    * Set the caller ID baggage value.
    * @param value The caller ID
@@ -267,7 +277,7 @@ export class BaggageBuilder {
   static setRequestContext(
     tenantId?: string | null,
     agentId?: string | null,
-    correlationId?: string | null
+    correlationId?: string | null,
   ): BaggageScope {
     return new BaggageBuilder()
       .tenantId(tenantId)
diff --git a/packages/agents-a365-observability/src/tracing/processors/util.ts b/packages/agents-a365-observability/src/tracing/processors/util.ts
index b9aa94c4..4b960dae 100644
--- a/packages/agents-a365-observability/src/tracing/processors/util.ts
+++ b/packages/agents-a365-observability/src/tracing/processors/util.ts
@@ -12,6 +12,7 @@ export const GENERIC_ATTRIBUTES: readonly string[] = [
   consts.CUSTOM_PARENT_SPAN_ID_KEY,
   consts.CUSTOM_SPAN_NAME_KEY,
   consts.CORRELATION_ID_KEY,
+  consts.SESSION_ID_KEY,
   consts.GEN_AI_CONVERSATION_ID_KEY,
   consts.GEN_AI_CONVERSATION_ITEM_LINK_KEY,
   consts.GEN_AI_OPERATION_NAME_KEY,
diff --git a/tests/observability/core/BaggageBuilder.test.ts b/tests/observability/core/BaggageBuilder.test.ts
index 73ab2e41..e3afd04a 100644
--- a/tests/observability/core/BaggageBuilder.test.ts
+++ b/tests/observability/core/BaggageBuilder.test.ts
@@ -2,7 +2,7 @@
 // Copyright (c) Microsoft Corporation. All rights reserved.
 // ------------------------------------------------------------------------------
 
-import { context } from '@opentelemetry/api';
+import { context, propagation } from '@opentelemetry/api';
 import { BaggageBuilder, BaggageScope } from '@microsoft/agents-a365-observability/dist/cjs/tracing/middleware/BaggageBuilder';
 import { OpenTelemetryConstants } from '@microsoft/agents-a365-observability/dist/cjs/tracing/constants';
 
@@ -133,6 +133,27 @@ describe('BaggageBuilder', () => {
     });
   });
 
+  describe('sessionId support', () => {
+    it('should set sessionId via fluent API', () => {
+      const scope = new BaggageBuilder()
+        .tenantId('tenant-123')
+        .agentId('agent-456')
+        .correlationId('corr-789')
+        .sessionId('session-0001')
+        .build();
+      const bag = propagation.getBaggage((scope as any).contextWithBaggage);
+      expect(bag?.getEntry(OpenTelemetryConstants.SESSION_ID_KEY)?.value).toBe('session-0001');
+    });
+
+    it('should omit empty sessionId value', () => {
+      const scope = new BaggageBuilder()
+        .sessionId('   ')
+        .build();
+      const bag = propagation.getBaggage((scope as any).contextWithBaggage);
+      expect(bag?.getEntry(OpenTelemetryConstants.SESSION_ID_KEY)).toBeUndefined();
+    });
+  });
+
 });
 
 describe('BaggageScope', () => {
diff --git a/tests/observability/core/SpanProcessor.test.ts b/tests/observability/core/SpanProcessor.test.ts
index 32b75f8b..2b175904 100644
--- a/tests/observability/core/SpanProcessor.test.ts
+++ b/tests/observability/core/SpanProcessor.test.ts
@@ -27,7 +27,6 @@ describe('SpanProcessor', () => {
 
   describe('baggage to span attribute enrichment', () => {
     it('should copy generic attributes from baggage to span', () => {
-      // Set baggage
       const baggageEntries = {
         [OpenTelemetryConstants.TENANT_ID_KEY]: 'tenant-123',
         [OpenTelemetryConstants.CORRELATION_ID_KEY]: 'corr-456',
@@ -41,7 +40,7 @@ describe('SpanProcessor', () => {
 
       const ctx = propagation.setBaggage(context.active(), baggage);
 
-      // Create a span in this context
+      // Create a span in this context (parentContext not passed so processor may no-op)
       const tracer = provider.getTracer('test');
       let testSpan: Span | undefined;
 
@@ -52,10 +51,23 @@ describe('SpanProcessor', () => {
         }
       });
 
-      // The span processor should have copied baggage to attributes
       expect(testSpan).toBeDefined();
     });
 
+
+    it('should copy sessionId from baggage to span', () => {
+      let baggage = propagation.createBaggage();
+      baggage = baggage.setEntry(OpenTelemetryConstants.SESSION_ID_KEY, { value: 'session-abc' });
+
+      const ctx = propagation.setBaggage(context.active(), baggage);
+      const tracer = provider.getTracer('test');
+      const testSpan = tracer.startSpan('test-span', { kind: SpanKind.CLIENT }, ctx as any);
+      testSpan.end();
+
+      const attrs = (testSpan as any)._attributes ?? (testSpan as any).attributes ?? {};
+      expect(attrs[OpenTelemetryConstants.SESSION_ID_KEY]).toBe('session-abc');
+    });
+
     it('should copy invoke agent attributes for invoke_agent operations', () => {
       // Set baggage with invoke agent specific fields
       const baggageEntries = {
@@ -139,6 +151,7 @@ describe('SpanProcessor', () => {
       expect(GENERIC_ATTRIBUTES).toContain(OpenTelemetryConstants.TENANT_ID_KEY);
       expect(GENERIC_ATTRIBUTES).toContain(OpenTelemetryConstants.CORRELATION_ID_KEY);
       expect(GENERIC_ATTRIBUTES).toContain(OpenTelemetryConstants.GEN_AI_AGENT_ID_KEY);
+      expect(GENERIC_ATTRIBUTES).toContain(OpenTelemetryConstants.SESSION_ID_KEY);
     });
 
     it('should apply invoke agent specific attributes', () => {