diff --git a/astra/core.py b/astra/core.py
index d4295da..59f895b 100644
--- a/astra/core.py
+++ b/astra/core.py
@@ -1,5 +1,6 @@
 """Configuration and pure request policy, independent of audio hardware."""
 
+import json
 import os
 from dataclasses import dataclass
 
@@ -106,10 +107,36 @@ def trim_messages(messages: list[dict], max_chars: int = 10000) -> list[dict]:
     return system + turns
 
 
+def normalize_tool_calls(messages: list[dict]) -> list[dict]:
+    """Ollama's native /api/chat rejects tool_calls whose function.arguments
+    is a JSON string (400 "Value looks like object..."); it wants an object.
+    Pipecat's context stores tool_calls OpenAI-style, arguments as a string,
+    so every request has to convert it back before it reaches Ollama.
+    """
+    normalized = []
+    for message in messages:
+        tool_calls = message.get("tool_calls")
+        if not tool_calls:
+            normalized.append(message)
+            continue
+        new_calls = []
+        for call in tool_calls:
+            function = call.get("function", {})
+            arguments = function.get("arguments")
+            if isinstance(arguments, str):
+                try:
+                    arguments = json.loads(arguments)
+                except json.JSONDecodeError:
+                    pass
+            new_calls.append({**call, "function": {**function, "arguments": arguments}})
+        normalized.append({**message, "tool_calls": new_calls})
+    return normalized
+
+
 def build_request(settings: Settings, messages: list[dict]) -> dict:
     return {
         "model": settings.model,
-        "messages": trim_messages(messages),
+        "messages": normalize_tool_calls(trim_messages(messages)),
         "think": False,
         "stream": True,
         "keep_alive": -1,
diff --git a/astra/server.py b/astra/server.py
index 4b3ec0a..a131b40 100644
--- a/astra/server.py
+++ b/astra/server.py
@@ -158,12 +158,12 @@ async def run_voice(connection, models, config, voice_state, voice_name, context
 
     @aggregators.assistant().event_handler("on_assistant_turn_stopped")
     async def assistant_turn(aggregator, message):
-        if message.content:
+        if message.content or message.interrupted:
             notify(
                 {
                     "type": "transcript",
                     "role": "assistant",
-                    "text": message.content,
+                    "text": message.content or "…",
                     "interrupted": message.interrupted,
                 }
             )
diff --git a/tests/test_core.py b/tests/test_core.py
index 460ee2a..16befdd 100644
--- a/tests/test_core.py
+++ b/tests/test_core.py
@@ -1,6 +1,12 @@
 import unittest
 
-from astra.core import Settings, build_request, local_origin_allowed, trim_messages
+from astra.core import (
+    Settings,
+    build_request,
+    local_origin_allowed,
+    normalize_tool_calls,
+    trim_messages,
+)
 
 
 class CoreTests(unittest.TestCase):
@@ -64,6 +70,47 @@ class CoreTests(unittest.TestCase):
         self.assertEqual(trimmed[2]["tool_calls"][0]["function"]["name"], "generate_image")
         self.assertEqual(trimmed[3]["tool_call_id"], "call_1")
 
+    def test_tool_call_string_arguments_are_normalized_to_an_object(self):
+        messages = [
+            {
+                "role": "assistant",
+                "content": "",
+                "tool_calls": [
+                    {
+                        "id": "call_1",
+                        "type": "function",
+                        "function": {"name": "generate_image", "arguments": '{"prompt": "a cat"}'},
+                    }
+                ],
+            }
+        ]
+        normalized = normalize_tool_calls(messages)
+        self.assertEqual(
+            normalized[0]["tool_calls"][0]["function"]["arguments"], {"prompt": "a cat"}
+        )
+        # The original message is untouched (immutable transform).
+        self.assertIsInstance(messages[0]["tool_calls"][0]["function"]["arguments"], str)
+
+    def test_build_request_normalizes_tool_call_arguments_end_to_end(self):
+        messages = [
+            {"role": "user", "content": "Erzeuge ein Bild."},
+            {
+                "role": "assistant",
+                "content": "",
+                "tool_calls": [
+                    {
+                        "id": "call_1",
+                        "type": "function",
+                        "function": {"name": "generate_image", "arguments": '{"prompt": "a cat"}'},
+                    }
+                ],
+            },
+            {"role": "tool", "tool_call_id": "call_1", "content": '{"status": "ok"}'},
+        ]
+        request = build_request(Settings(), messages)
+        tool_call_message = next(m for m in request["messages"] if m.get("tool_calls"))
+        self.assertIsInstance(tool_call_message["tool_calls"][0]["function"]["arguments"], dict)
+
     def test_image_attachment_survives_trimming(self):
         messages = [
             {"role": "system", "content": "Deutsch"},