core/lmproto: coerce developer role for chat completions

src/plyngent/lmproto/deepseek/openai_compat/client.py

@@ -3,6 +3,7 @@ from typing import TYPE_CHECKING, Literal, overload
 import msgspec
 
 from ...openai_compatible.client import BaseOpenAIClient, read_response_body
+from ...openai_compatible.compat import coerce_chat_completions_param_any
 
 if TYPE_CHECKING:
     from collections.abc import AsyncIterator
@@ -29,7 +30,7 @@ class DeepseekOpenAIClient(BaseOpenAIClient):
     async def chat_completions(
         self, param: ChatCompletionsParam, *, stream: bool = False
     ) -> ChatCompletionResponse | AsyncIterator[ChatCompletionChunk]:
-        param = msgspec.structs.replace(param, stream=stream)
+        param = coerce_chat_completions_param_any(msgspec.structs.replace(param, stream=stream))
         data = self.encoder.encode(param)
         if stream:
             resp = await self.session.post(

src/plyngent/lmproto/openai_compatible/client.py

@@ -8,6 +8,7 @@ import niquests
 from msgspec import UNSET
 from niquests.auth import BearerTokenAuth
 
+from .compat import coerce_chat_completions_param
 from .config import OpenAIConfig  # noqa: TC001
 from .model import (
     AssistantFunctionTool,
@@ -196,7 +197,7 @@ class OpenAICompatibleClient(BaseOpenAIClient):
         self, param: ChatCompletionsParam, *, stream: bool = False
     ) -> ChatCompletionResponse | AsyncIterator[ChatCompletionChunk]:
         # Library pattern: async def returns AsyncIterator when stream=True.
-        param = msgspec.structs.replace(param, stream=stream)
+        param = coerce_chat_completions_param(msgspec.structs.replace(param, stream=stream))
         data = self.encoder.encode(param)
         if stream:
             resp = await self.session.post(

src/plyngent/lmproto/openai_compatible/compat.py

@@ -0,0 +1,62 @@
+"""Message normalization for chat-completions-compatible wire APIs."""
+
+from __future__ import annotations
+
+from typing import TYPE_CHECKING, Any, cast
+
+import msgspec
+
+from .model import DeveloperChatMessage, SystemChatMessage
+
+if TYPE_CHECKING:
+    from collections.abc import Sequence
+
+    from .model import AnyChatMessage, ChatCompletionsParam
+
+
+def developer_to_system_message(message: DeveloperChatMessage) -> SystemChatMessage:
+    """Convert an internal developer-role message to classic chat ``system`` role."""
+    return SystemChatMessage(content=message.content, name=message.name)
+
+
+def coerce_developer_messages_to_system(messages: Sequence[AnyChatMessage]) -> list[AnyChatMessage]:
+    """Return *messages* with ``developer`` roles rewritten as ``system``.
+
+    Most OpenAI-compatible ``/chat/completions`` providers only accept
+    system/user/assistant/tool. Internal developer checkpoints still carry
+    control-plane intent best as ``system`` on that wire protocol.
+    """
+    changed = False
+    out: list[AnyChatMessage] = []
+    for message in messages:
+        if isinstance(message, DeveloperChatMessage):
+            out.append(developer_to_system_message(message))
+            changed = True
+        else:
+            out.append(message)
+    return out if changed else list(messages)
+
+
+def coerce_chat_completions_param(param: ChatCompletionsParam) -> ChatCompletionsParam:
+    """Normalize a chat-completions request for broad provider compatibility."""
+    messages = coerce_developer_messages_to_system(param.messages)
+    if messages == param.messages:
+        return param
+    return msgspec.structs.replace(param, messages=messages)
+
+
+def coerce_chat_completions_param_any(param: Any) -> Any:
+    """Generic variant for provider-specific chat param structs.
+
+    DeepSeek's request type excludes ``DeveloperChatMessage`` from its annotation,
+    but callers can still pass the generic agent param shape at runtime. Replace
+    messages structurally before encoding without depending on the exact class.
+    """
+    messages_obj: Any = getattr(param, "messages", None)
+    if not isinstance(messages_obj, list):
+        return param
+    messages = cast("list[AnyChatMessage]", messages_obj)
+    coerced = coerce_developer_messages_to_system(messages)
+    if coerced == messages:
+        return param
+    return msgspec.structs.replace(param, messages=coerced)