diff --git a/changelog/4522.changed.md b/changelog/4522.changed.md
new file mode 100644
index 000000000..37156adc7
--- /dev/null
+++ b/changelog/4522.changed.md
@@ -0,0 +1 @@
+- Updated the default p99 TTFS latency values for Smallest AI, Mistral, and XAI STT so turn stop timing uses measured values instead of the conservative fallback.
diff --git a/src/pipecat/services/stt_latency.py b/src/pipecat/services/stt_latency.py
index 7d285e353..f3fa235d5 100644
--- a/src/pipecat/services/stt_latency.py
+++ b/src/pipecat/services/stt_latency.py
@@ -44,17 +44,15 @@ GLADIA_TTFS_P99: float = 1.49
 GOOGLE_TTFS_P99: float = 1.57
 GRADIUM_TTFS_P99: float = 1.61
 GROQ_TTFS_P99: float = 1.54
+MISTRAL_TTFS_P99: float = 1.89
 OPENAI_TTFS_P99: float = 2.01
 OPENAI_REALTIME_TTFS_P99: float = 1.66
 SARVAM_TTFS_P99: float = 1.17
+SMALLEST_TTFS_P99: float = 1.59
 SONIOX_TTFS_P99: float = 0.35
 SPEECHMATICS_TTFS_P99: float = 0.74
+XAI_TTFS_P99: float = 2.14
 
 # These services run locally and should be replaced with measured values
 NVIDIA_TTFS_P99: float = DEFAULT_TTFS_P99
 WHISPER_TTFS_P99: float = DEFAULT_TTFS_P99
-
-# No benchmark available yet; using conservative default
-MISTRAL_TTFS_P99: float = DEFAULT_TTFS_P99
-SMALLEST_TTFS_P99: float = DEFAULT_TTFS_P99
-XAI_TTFS_P99: float = DEFAULT_TTFS_P99