How to Manage Multimodal API Calls Across Text, Image, and Audio in One Session

Multimodal APIs are typically documented per modality, leaving developers without guidance on combining text, image, audio, and video inputs into a single coherent session. A practical approach involves treating each request as an ordered list of typed parts, where each element declares its own modality, eliminating the need for multiple correlated API calls. Developers should note that large assets must be uploaded and referenced by URI rather than inlined as base64, since exceeding provider-specific size limits returns an unhelpful error rather than a clear message. Response handlers must function as state machines because text streams token by token while images arrive whole and audio may come in chunks, meaning stream events cannot all be treated as appendable text. Multi-turn sessions with images accumulate token costs quickly, so summarising older turns and allowing users to pin only essential assets in context are recommended strategies to control expenses.