# AIP017: system-message-mismatch
## Description
Detects Anthropic-style system prompts (opening with "You are...") when targeting Gemini models. Gemini handles system messages with different semantics than Anthropic's Claude, and direct porting may not work as intended.
## Severity
Info
## Applies When
This rule only fires when `target_models` is configured to include models with names starting with `gemini` (case-insensitive). The rule only checks `system` role prompts. If no target models are specified, this rule produces no diagnostics.
## Example
```
role: system
model: gemini-1.5-pro
prompt: |
You are a helpful assistant that answers questions accurately.
```
Violation: Gemini's system message handling differs from Claude's; this pattern may not achieve the desired behavior.
## Remediation
Consult Gemini's documentation on system instructions and restructure your prompt to align with Gemini's conventions. Consider using explicit instructions instead of role-play framing.