Request.Messages carries an ordered content.AgenticMessages thread. The request does not copy or normalize it, so the caller should finish construction before invoking the client and avoid concurrent mutation.

API surface

request := inference.Request{
	Messages: content.AgenticMessages{
		&content.SystemMessage{Message: content.Message{
			Role: content.RoleSystem,
			Blocks: []content.Block{&content.TextBlock{Text: "Be precise."}},
		}},
		&content.UserMessage{Message: content.Message{
			Role: content.RoleUser,
			Blocks: []content.Block{&content.TextBlock{Text: "Explain this chart."}},
		}},
	},
}

Messages may contain any sealed block variant. Before encoding, ValidateRequestFeatures recursively looks for ImageBlock values, including images inside ToolResultBlock.Content, and compares that usage with Model.Caps.AcceptsImages.

Conversation policy

Keep the system prompt in Request.System when it is a per-agent instruction that should not become a history turn. Use a SystemMessage when the provider-neutral conversation itself needs that typed turn. Append returned AIMessage and matching ToolResultMessage values in order for an agentic loop.

Proof

Source: inference/client.go, core/content/message.go
Tests: inference/client_test.go, core/content/message_test.go