inference.Request is the complete provider-neutral input to Client.Invoke or Client.Stream. It keeps model identity, per-agent instructions, ordered messages, tools, structured output, tool choice, and per-call sampling in one value.

Request surface

type Request struct {
	Model             model.Model
	System            string
	Messages          content.AgenticMessages
	TransientMessages int
	Tools             []Tool
	Output            *OutputSchema
	ToolChoice        ToolChoice
	Override          *model.Sampling
}

Field	Ownership and behavior
`Model`	Secret-free descriptor; validate before use
`System`	Per-call system instruction, separate from message history
`Messages`	Ordered sealed conversation turns
`Tools`	Tool definitions exposed to the model
`Output`	Optional portable JSON object contract
`TransientMessages`	Count of trailing messages excluded from cache breakpoints
`ToolChoice`	Automatic, required, or named tool behavior
`Override`	Optional per-call replacement for model sampling

request := inference.Request{
	Model: model.CustomModel(model.ProviderName("acme"), model.APIFormatOpenAI, "https://api.example.test", "chat-1"),
	System: "Answer with evidence.",
	Messages: content.AgenticMessages{&content.UserMessage{Message: content.Message{
		Role: content.RoleUser,
		Blocks: []content.Block{&content.TextBlock{Text: "What changed?"}},
	}}},
}
if err := inference.ValidateRequestFeatures(request); err != nil {
	panic(err)
}

The Harness model request step is the canonical consumer path when a request is produced inside a Harness loop.

Proof

Source: inference/client.go, inference/output.go
Tests: inference/client_test.go