From f4b824524106a69c7363ff618aabf87d8ccd2ae2 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Aleix=20Conchillo=20Flaqu=C3=A9?= <aleix@daily.co>
Date: Thu, 5 Mar 2026 14:55:31 -0800
Subject: [PATCH 1/2] Warn when both system_instruction and context system
 message are set

system_instruction from the constructor always takes precedence. A
warning is now logged when the context also contains a system message
so users can spot the conflict.
---
 src/pipecat/services/anthropic/llm.py   | 5 +++++
 src/pipecat/services/aws/llm.py         | 5 +++++
 src/pipecat/services/openai/base_llm.py | 7 ++++++-
 3 files changed, 16 insertions(+), 1 deletion(-)

diff --git a/src/pipecat/services/anthropic/llm.py b/src/pipecat/services/anthropic/llm.py
index 755ca6400..5981d3e50 100644
--- a/src/pipecat/services/anthropic/llm.py
+++ b/src/pipecat/services/anthropic/llm.py
@@ -403,6 +403,11 @@ class AnthropicLLMService(LLMService):
                 context, enable_prompt_caching=self._settings.enable_prompt_caching
             )
             if self._system_instruction:
+                if params["system"] is not NOT_GIVEN:
+                    logger.warning(
+                        f"{self}: Both system_instruction and a system message in context are"
+                        " set. Using system_instruction."
+                    )
                 params["system"] = self._system_instruction
             return params
 
diff --git a/src/pipecat/services/aws/llm.py b/src/pipecat/services/aws/llm.py
index 31f8085bc..e465ae460 100644
--- a/src/pipecat/services/aws/llm.py
+++ b/src/pipecat/services/aws/llm.py
@@ -1025,6 +1025,11 @@ class AWSBedrockLLMService(LLMService):
             adapter: AWSBedrockLLMAdapter = self.get_llm_adapter()
             params: AWSBedrockLLMInvocationParams = adapter.get_llm_invocation_params(context)
             if self._system_instruction:
+                if params["system"]:
+                    logger.warning(
+                        f"{self}: Both system_instruction and a system message in context are"
+                        " set. Using system_instruction."
+                    )
                 params["system"] = [{"text": self._system_instruction}]
             return params
 
diff --git a/src/pipecat/services/openai/base_llm.py b/src/pipecat/services/openai/base_llm.py
index ed012d0df..dfef1ae90 100644
--- a/src/pipecat/services/openai/base_llm.py
+++ b/src/pipecat/services/openai/base_llm.py
@@ -292,9 +292,14 @@ class BaseOpenAILLMService(LLMService):
 
         params.update(self._settings.extra)
 
-        # Prepend system instruction if set
+        # Prepend system instruction from constructor, replacing any context system message
         if self._system_instruction:
             messages = params.get("messages", [])
+            if messages and messages[0].get("role") == "system":
+                logger.warning(
+                    f"{self}: Both system_instruction and a system message in context are set."
+                    " Using system_instruction."
+                )
             params["messages"] = [
                 {"role": "system", "content": self._system_instruction}
             ] + messages

From fda4cb6732587db938f9870c6c073603ef4b6a95 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Aleix=20Conchillo=20Flaqu=C3=A9?= <aleix@daily.co>
Date: Thu, 5 Mar 2026 16:16:41 -0800
Subject: [PATCH 2/2] Add changelog for #3932

---
 changelog/3932.added.md | 1 +
 1 file changed, 1 insertion(+)
 create mode 100644 changelog/3932.added.md

diff --git a/changelog/3932.added.md b/changelog/3932.added.md
new file mode 100644
index 000000000..e97690d44
--- /dev/null
+++ b/changelog/3932.added.md
@@ -0,0 +1 @@
+- LLM services (`BaseOpenAILLMService`, `AnthropicLLMService`, `AWSBedrockLLMService`) now log a warning when both `system_instruction` and a system message in the context are set. The constructor's `system_instruction` takes precedence.