Acontext normalizes messages to a unified internal schema on store, and converts back to the target provider format on retrieval.
Conversion Flow
Part Type Conversion Matrix
Each message is composed of typed parts. The table below shows how each internal part type maps to provider-specific structures on retrieval:
| Internal Part Type | OpenAI | Anthropic | Gemini |
|---|
text | content string or text content part | text block | text part |
image | image_url content part | image block (base64) | InlineData part |
tool-call | tool_calls array | tool_use block | FunctionCall part |
tool-result | tool role message | tool_result block | FunctionResponse part |
thinking | downgraded to text content part | native thinking block with signature | native Thought part with ThoughtSignature |
audio | input_audio content part | — | — |
file | file content part | document block | — |
Thinking blocks from Anthropic and Gemini are stored identically and are fully cross-compatible. A thinking block stored from Claude can be retrieved in Gemini format as a native Thought part, and vice versa.
Role Mapping
| Provider | Provider Roles | Internal Role |
|---|
| OpenAI | user, assistant, tool, function | user or assistant |
| Anthropic | user, assistant | user or assistant |
| Gemini | user, model | user or assistant |
assistant is converted back to model for Gemini format.
Provider-specific Handling
