fix: GoogleLLMService TTFB value

CHANGELOG.md

@@ -5,6 +5,12 @@ All notable changes to **Pipecat** will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [Unreleased]
+
+### Fixed
+
+- Fixed an issue where `GoogleLLMService`'s TTFB value was incorrect.
+
 ## [0.0.71] - 2025-06-10
 
 ### Added

src/pipecat/services/google/llm.py

@@ -555,10 +555,11 @@ class GoogleLLMService(LLMService):
                 contents=messages,
                 config=generation_config,
             )
-            await self.stop_ttfb_metrics()
 
             function_calls = []
             async for chunk in response:
+                # Stop TTFB metrics after the first chunk
+                await self.stop_ttfb_metrics()
                 if chunk.usage_metadata:
                     prompt_tokens += chunk.usage_metadata.prompt_token_count or 0
                     completion_tokens += chunk.usage_metadata.candidates_token_count or 0