diff --git a/docs/tracing.md b/docs/tracing.md
index d73a644209..b9cc14a22d 100644
--- a/docs/tracing.md
+++ b/docs/tracing.md
@@ -139,11 +139,19 @@ Spans are automatically part of the current trace, and are nested under the near
 
 Certain spans may capture potentially sensitive data.
 
-The `generation_span()` stores the inputs/outputs of the LLM generation, and `function_span()` stores the inputs/outputs of function calls. These may contain sensitive data, so you can disable capturing that data via [`RunConfig.trace_include_sensitive_data`][agents.run.RunConfig.trace_include_sensitive_data].
+The `generation_span()` stores the inputs/outputs of the LLM generation, and `function_span()` stores the inputs/outputs of function calls. These may contain sensitive data, so you can control capturing that data via [`RunConfig.trace_include_sensitive_data`][agents.run.RunConfig.trace_include_sensitive_data].
 
 Similarly, Audio spans include base64-encoded PCM data for input and output audio by default. You can disable capturing this audio data by configuring [`VoicePipelineConfig.trace_include_sensitive_audio_data`][agents.voice.pipeline_config.VoicePipelineConfig.trace_include_sensitive_audio_data].
 
-By default, `trace_include_sensitive_data` is `True`. You can set the default without code by exporting the `OPENAI_AGENTS_TRACE_INCLUDE_SENSITIVE_DATA` environment variable to `true/1` or `false/0` before running your app.
+By default, `trace_include_sensitive_data` is `False`. Applications that intentionally need model and tool inputs/outputs in traces must opt in explicitly, either in code:
+
+```python
+from agents import RunConfig
+
+run_config = RunConfig(trace_include_sensitive_data=True)
+```
+
+or by exporting `OPENAI_AGENTS_TRACE_INCLUDE_SENSITIVE_DATA=true` (also accepts `1`, `yes`, or `on`). Setting the option explicitly is recommended for applications migrating from releases where sensitive trace data was included by default.
 
 ## Custom tracing processors
 
diff --git a/src/agents/run_config.py b/src/agents/run_config.py
index cf28ec5cf8..e449fa510e 100644
--- a/src/agents/run_config.py
+++ b/src/agents/run_config.py
@@ -51,7 +51,7 @@
 
 def _default_trace_include_sensitive_data() -> bool:
     """Return the default for trace_include_sensitive_data based on environment."""
-    val = os.getenv("OPENAI_AGENTS_TRACE_INCLUDE_SENSITIVE_DATA", "true")
+    val = os.getenv("OPENAI_AGENTS_TRACE_INCLUDE_SENSITIVE_DATA", "false")
     return val.strip().lower() in ("1", "true", "yes", "on")
 
 
diff --git a/src/agents/voice/pipeline_config.py b/src/agents/voice/pipeline_config.py
index 35c55d093a..4a292dcafb 100644
--- a/src/agents/voice/pipeline_config.py
+++ b/src/agents/voice/pipeline_config.py
@@ -23,9 +23,10 @@ class VoicePipelineConfig:
     tracing: TracingConfig | None = None
     """Tracing configuration for this pipeline."""
 
-    trace_include_sensitive_data: bool = True
-    """Whether to include sensitive data in traces. Defaults to `True`. This is specifically for the
-      voice pipeline, and not for anything that goes on inside your Workflow."""
+    trace_include_sensitive_data: bool = False
+    """Whether to include sensitive data in traces. Defaults to `False` for security. When enabled,
+      tool inputs/outputs and LLM generations may be exposed in traces. Only enable in trusted
+      environments."""
 
     trace_include_sensitive_audio_data: bool = True
     """Whether to include audio data in traces. Defaults to `True`."""
diff --git a/tests/test_run_config.py b/tests/test_run_config.py
index 8c88046af5..39cd30b35d 100644
--- a/tests/test_run_config.py
+++ b/tests/test_run_config.py
@@ -274,11 +274,11 @@ async def test_agent_model_object_is_used_when_present() -> None:
     assert result.final_output == "from-agent-object"
 
 
-def test_trace_include_sensitive_data_defaults_to_true_when_env_not_set(monkeypatch):
-    """By default, trace_include_sensitive_data should be True when the env is not set."""
+def test_trace_include_sensitive_data_defaults_to_false_when_env_not_set(monkeypatch):
+    """By default, trace_include_sensitive_data should be False for security when the env is not set."""
     monkeypatch.delenv("OPENAI_AGENTS_TRACE_INCLUDE_SENSITIVE_DATA", raising=False)
     config = RunConfig()
-    assert config.trace_include_sensitive_data is True
+    assert config.trace_include_sensitive_data is False
 
 
 @pytest.mark.parametrize(