diff --git a/src/rai_s2s/rai_s2s/asr/agents/initialization.py b/src/rai_s2s/rai_s2s/asr/agents/initialization.py
index 9ad163db0..caa744856 100644
--- a/src/rai_s2s/rai_s2s/asr/agents/initialization.py
+++ b/src/rai_s2s/rai_s2s/asr/agents/initialization.py
@@ -13,6 +13,7 @@
 # limitations under the License.
 
 from dataclasses import dataclass
+import math
 from typing import Literal, Optional
 
 import tomli
@@ -24,6 +25,20 @@ class VADConfig:
     threshold: float = 0.5
     silence_grace_period: float = 0.3
 
+    def __post_init__(self) -> None:
+        if not isinstance(self.threshold, (int, float)) or not math.isfinite(float(self.threshold)):
+            raise ValueError("threshold must be a finite number")
+        thr = float(self.threshold)
+        if thr <= 0.0 or thr > 1.0:
+            raise ValueError("threshold must be in (0, 1]")
+        if (
+            not isinstance(self.silence_grace_period, (int, float))
+            or not math.isfinite(float(self.silence_grace_period))
+        ):
+            raise ValueError("silence_grace_period must be a finite number")
+        if float(self.silence_grace_period) <= 0.0:
+            raise ValueError("silence_grace_period must be positive")
+
 
 @dataclass
 class WWConfig:
@@ -32,6 +47,13 @@ class WWConfig:
     threshold: float = 0.01
     is_used: bool = False
 
+    def __post_init__(self) -> None:
+        if not isinstance(self.threshold, (int, float)) or not math.isfinite(float(self.threshold)):
+            raise ValueError("threshold must be a finite number")
+        thr = float(self.threshold)
+        if thr <= 0.0 or thr > 1.0:
+            raise ValueError("threshold must be in (0, 1]")
+
 
 TRANSCRIBE_MODELS = ["LocalWhisper", "FasterWhisper", "OpenAI"]
 
diff --git a/tests/s2s/test_asr_agent_config_guards.py b/tests/s2s/test_asr_agent_config_guards.py
new file mode 100644
index 000000000..7cbf898d3
--- /dev/null
+++ b/tests/s2s/test_asr_agent_config_guards.py
@@ -0,0 +1,39 @@
+# Copyright (C) 2025 Robotec.AI
+import math
+
+import pytest
+
+from rai_s2s.asr.agents.initialization import VADConfig, WWConfig
+
+
+def test_vad_rejects_non_positive_threshold() -> None:
+    with pytest.raises(ValueError):
+        VADConfig(threshold=0.0)
+    with pytest.raises(ValueError):
+        VADConfig(threshold=-0.1)
+    with pytest.raises(ValueError):
+        VADConfig(threshold=1.1)
+
+
+def test_vad_rejects_non_positive_grace() -> None:
+    with pytest.raises(ValueError):
+        VADConfig(silence_grace_period=0.0)
+    with pytest.raises(ValueError):
+        VADConfig(silence_grace_period=float("nan"))
+
+
+def test_vad_accepts_defaults() -> None:
+    cfg = VADConfig()
+    assert cfg.threshold == 0.5
+
+
+def test_ww_rejects_bad_threshold() -> None:
+    with pytest.raises(ValueError):
+        WWConfig(threshold=0.0)
+    with pytest.raises(ValueError):
+        WWConfig(threshold=math.nan)
+
+
+def test_ww_accepts_defaults() -> None:
+    cfg = WWConfig()
+    assert 0.0 < cfg.threshold <= 1.0