[FEA-2240] fix(sdk-js): prevent unhandled rejection start failure

packages/sdk-js/src/v2/live/session.test.ts

@@ -165,4 +165,43 @@ describe('LiveV2Session connectSession', () => {
     )
     expect(session.sessionId).toBe('created-session-id')
   })
+
+  it('surfaces init failure without an unhandled rejection', async () => {
+    const initError = new Error('init failed')
+    mockHttpPost.mockRejectedValue(initError)
+
+    const unhandledRejections: unknown[] = []
+    const onUnhandledRejection = (reason: unknown) => {
+      unhandledRejections.push(reason)
+    }
+    process.on('unhandledRejection', onUnhandledRejection)
+
+    try {
+      const errorSpy = vi.fn()
+      const endedSpy = vi.fn()
+
+      const session = new LiveV2Session({
+        options: { sample_rate: 16000 },
+        httpClient,
+        webSocketClient,
+      })
+
+      session.on('error', errorSpy)
+      session.on('ended', endedSpy)
+
+      await expect(session.getSessionId()).rejects.toThrow('init failed')
+      await tick()
+
+      expect(errorSpy).toHaveBeenCalledWith(initError)
+      expect(endedSpy).toHaveBeenCalledWith({
+        code: 1006,
+        reason: `Couldn't start a new session`,
+      })
+      expect(session.status).toBe('ended')
+      expect(mockCreateSession).not.toHaveBeenCalled()
+      expect(unhandledRejections).toEqual([])
+    } finally {
+      process.off('unhandledRejection', onUnhandledRejection)
+    }
+  })
 })

packages/sdk-js/src/v2/live/session.ts

@@ -172,28 +172,44 @@ export class LiveV2Session {
   }
 
   private async startSession(): Promise<void> {
-    const session = await this.initSessionPromise
-    this.initSessionResponse = session
+    try {
+      const session = await this.initSessionPromise
+      this.initSessionResponse = session
 
-    if (this.abortController.signal.aborted) {
-      return
-    }
+      if (this.abortController.signal.aborted) {
+        return
+      }
 
-    if (this._status === 'starting') {
-      this._status = 'started'
-      this.emit('started', session)
-    }
+      if (this._status === 'starting') {
+        this._status = 'started'
+        this.emit('started', session)
+      }
 
-    if (this.sessionOptions.messages_config?.receive_lifecycle_events) {
-      const startSessionMessage: LiveV2StartSessionMessage = {
-        type: 'start_session',
-        session_id: session.id,
-        created_at: session.created_at,
+      if (this.sessionOptions.messages_config?.receive_lifecycle_events) {
+        const startSessionMessage: LiveV2StartSessionMessage = {
+          type: 'start_session',
+          session_id: session.id,
+          created_at: session.created_at,
+        }
+        this.emit('message', startSessionMessage)
       }
-      this.emit('message', startSessionMessage)
-    }
 
-    this.connectToWebSocket(session)
+      this.connectToWebSocket(session)
+    } catch (error) {
+      // initSession already emits 'error' and destroys on failure.
+      // Catch here so the constructor's fire-and-forget call cannot become an
+      // unhandled rejection that crashes the Node process.
+      if (this.abortController.signal.aborted || this._status === 'ended') {
+        return
+      }
+      this.emit(
+        'error',
+        error instanceof Error
+          ? error
+          : new Error(`Error starting session: ${error}`, { cause: error })
+      )
+      this.doDestroy(1006, `Couldn't start session`)
+    }
   }
 
   private connectToWebSocket(session: LiveV2InitResponse): void {