diff --git a/packages/http-client/__tests__/basics.test.ts b/packages/http-client/__tests__/basics.test.ts
index 254a8ec507..2bb57ed3bf 100644
--- a/packages/http-client/__tests__/basics.test.ts
+++ b/packages/http-client/__tests__/basics.test.ts
@@ -21,7 +21,10 @@ describe('basics', () => {
     _http = new httpm.HttpClient('http-client-tests')
   })
 
-  afterEach(() => {})
+  afterEach(() => {
+    // Clean up environment variable to prevent test pollution
+    delete process.env['ACTIONS_ORCHESTRATION_ID']
+  })
 
   it('constructs', () => {
     const http: httpm.HttpClient = new httpm.HttpClient('thttp-client-tests')
@@ -60,7 +63,7 @@ describe('basics', () => {
     const body: string = await res.readBody()
     const obj = JSON.parse(body)
     expect(obj.url).toBe('https://postman-echo.com/get')
-    expect(obj.headers['user-agent']).toBeFalsy()
+    expect(obj.headers['user-agent']).toBe('actions/http-client')
   })
 
   /* TODO write a mock rather then relying on a third party
@@ -374,4 +377,66 @@ describe('basics', () => {
       httpm.MediaTypes.ApplicationJson
     )
   })
+
+  it('appends orchestration ID to user-agent when ACTIONS_ORCHESTRATION_ID is set', async () => {
+    const orchId = 'test-orch-id-12345'
+    process.env['ACTIONS_ORCHESTRATION_ID'] = orchId
+
+    const http: httpm.HttpClient = new httpm.HttpClient('http-client-tests')
+    const res: httpm.HttpClientResponse = await http.get(
+      'https://postman-echo.com/get'
+    )
+    expect(res.message.statusCode).toBe(200)
+    const body: string = await res.readBody()
+    const obj = JSON.parse(body)
+    expect(obj.headers['user-agent']).toBe(
+      `http-client-tests actions_orchestration_id/${orchId}`
+    )
+  })
+
+  it('sanitizes invalid characters in orchestration ID', async () => {
+    const orchId = 'test (with) special/chars'
+    process.env['ACTIONS_ORCHESTRATION_ID'] = orchId
+
+    const http: httpm.HttpClient = new httpm.HttpClient('http-client-tests')
+    const res: httpm.HttpClientResponse = await http.get(
+      'https://postman-echo.com/get'
+    )
+    expect(res.message.statusCode).toBe(200)
+    const body: string = await res.readBody()
+    const obj = JSON.parse(body)
+    // Spaces, parentheses, and slashes should be replaced with underscores
+    expect(obj.headers['user-agent']).toBe(
+      'http-client-tests actions_orchestration_id/test__with__special_chars'
+    )
+  })
+
+  it('does not modify user-agent when ACTIONS_ORCHESTRATION_ID is not set', async () => {
+    delete process.env['ACTIONS_ORCHESTRATION_ID']
+
+    const http: httpm.HttpClient = new httpm.HttpClient('http-client-tests')
+    const res: httpm.HttpClientResponse = await http.get(
+      'https://postman-echo.com/get'
+    )
+    expect(res.message.statusCode).toBe(200)
+    const body: string = await res.readBody()
+    const obj = JSON.parse(body)
+    expect(obj.headers['user-agent']).toBe('http-client-tests')
+  })
+
+  it('uses default user-agent with orchestration ID when no custom user-agent provided', async () => {
+    const orchId = 'test-default-id-12345'
+    process.env['ACTIONS_ORCHESTRATION_ID'] = orchId
+
+    const http: httpm.HttpClient = new httpm.HttpClient()
+    const res: httpm.HttpClientResponse = await http.get(
+      'https://postman-echo.com/get'
+    )
+    expect(res.message.statusCode).toBe(200)
+    const body: string = await res.readBody()
+    const obj = JSON.parse(body)
+    expect(obj.headers['user-agent']).toBe(
+      `actions/http-client actions_orchestration_id/${orchId}`
+    )
+  })
 })
diff --git a/packages/http-client/src/index.ts b/packages/http-client/src/index.ts
index 5691e89137..2aee17dc3e 100644
--- a/packages/http-client/src/index.ts
+++ b/packages/http-client/src/index.ts
@@ -147,7 +147,7 @@ export class HttpClient {
     handlers?: ifm.RequestHandler[],
     requestOptions?: ifm.RequestOptions
   ) {
-    this.userAgent = userAgent
+    this.userAgent = this._getUserAgentWithOrchestrationId(userAgent)
     this.handlers = handlers || []
     this.requestOptions = requestOptions
     if (requestOptions) {
@@ -816,6 +816,18 @@ export class HttpClient {
     return proxyAgent
   }
 
+  private _getUserAgentWithOrchestrationId(userAgent?: string): string {
+    const baseUserAgent = userAgent || 'actions/http-client'
+    const orchId = process.env['ACTIONS_ORCHESTRATION_ID']
+    if (orchId) {
+      // Sanitize the orchestration ID to ensure it contains only valid characters
+      // Valid characters: 0-9, a-z, _, -, .
+      const sanitizedId = orchId.replace(/[^a-z0-9_.-]/gi, '_')
+      return `${baseUserAgent} actions_orchestration_id/${sanitizedId}`
+    }
+    return baseUserAgent
+  }
+
   private async _performExponentialBackoff(retryNumber: number): Promise<void> {
     retryNumber = Math.min(ExponentialBackoffCeiling, retryNumber)
     const ms: number = ExponentialBackoffTimeSlice * Math.pow(2, retryNumber)