Two goals:
1. Centralize system_instruction vs context system message resolution into
the LLM adapters. This eliminates duplication between in-pipeline and
out-of-band (run_inference) code paths across ~16 locations in service
llm.py files.
2. Add support for "developer" role messages in conversation context, which
is facilitated by the above centralization.
Shared helpers on BaseLLMAdapter:
- _extract_initial_system_or_developer: extracts/converts messages[0]
based on role and whether system_instruction is provided
- _resolve_system_instruction: warns on conflicts between system_instruction
and context system messages, returns the effective instruction
Developer message handling (new):
- Non-OpenAI adapters: an initial "developer" message is promoted to the
system instruction when no system_instruction is provided; otherwise it
is converted to "user". Subsequent "developer" messages are always
converted to "user". No conflict warning is emitted for developer
messages (unlike "system" messages).
- OpenAI adapter: "developer" messages pass through in conversation
history without triggering conflict warnings.
- OpenAI Responses adapter: "developer" messages are kept as "developer"
role (same as "system", which is also converted to "developer" for the
Responses API).
Other behavior changes:
- Gemini: "initial" system message detection now checks messages[0] only
(previously searched anywhere in the list)
- Bedrock: a lone system message is now converted to "user" instead of
being extracted to an empty message list (matches existing Anthropic
behavior)
Perplexity appears to have statefulness within a conversation, so
converting a system message to "user" in one call and then back to
"system" in the next (after more messages are appended) causes API
errors. Remove the trailing system→user conversion entirely — if the
context only has system messages, the API call will fail but the
mistake will be caught right away.
Add test exercising the step 3 ordering where stripping a trailing
assistant exposes a system message that then gets converted to user.
Move the reasoning about when a trailing system message can occur
into the docstring.
Perplexity allows multiple initial system messages, so don't merge them.
Instead, skip system-system pairs during the consecutive same-role merge
step. Broaden the trailing message fix to convert any trailing system
message to user (not just a lone system message), so contexts with only
system messages don't fail.
Perplexity's API is stricter than OpenAI about conversation history:
- Requires strict alternation between user/tool and assistant messages
- Disallows system messages except as the initial message
- Requires the last message to be user or tool
The new adapter transforms messages before sending to satisfy all three
constraints: merging consecutive initial system messages, converting
non-initial system to user, merging consecutive same-role messages, and
removing trailing assistant messages.
Also adds dual-system-instruction warnings to Cerebras, Fireworks,
Mistral, Perplexity, and SambaNova services (matching the existing
BaseOpenAILLMService pattern), and updates the warning text in
BaseOpenAILLMService to be more descriptive.
