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System Instructions
Describe system instructions configured on a Loop.
The base system text is configured with:
func WithSystem(system string) OptionIt is stored as immutable definition state. A mode can add a mode-local
Instructions string. The runtime never mutates the base prompt when selecting
a mode.
Effective system
Use the exported composition rule when a consumer needs to reproduce the exact request identity:
func EffectiveSystem(system, instructions string) stringThe result is instructions when the base is empty, system when mode
instructions are empty, and system + "\n\n" + instructions otherwise.
BoundDefinition.EffectiveSystem() applies the same rule to its selected mode.
This byte-for-byte equality matters because the Rig fingerprints the effective
system text for restore compatibility.
| Input | Result |
|---|---|
system="", instructions="" | "" |
system="base", instructions="" | "base" |
system="", instructions="mode" | "mode" |
system="base", instructions="mode" | "base\n\nmode" |
definition, err := loop.Define(
loop.WithName("assistant"),
loop.WithInference(client, selectedModel),
loop.WithSystem("You are a careful project assistant."),
loop.WithModes(loop.Mode{
Name: "review",
Instructions: "Explain risks before proposing edits.",
}),
loop.WithInitialMode("review"),
)
if err != nil {
return err
}
bound, err := definition.Bind(ctx, bindings)
if err != nil {
return err
}
fmt.Println(bound.EffectiveSystem())The definition’s PolicyRevision includes system and mode instructions. A
description or display name is presentation metadata; WithDescription is
included in Rig topology identity because it is injected into delegate
capabilities, while WithDisplayName is not an execution-policy input.