Runtime context

A RuntimeContext is the ambient configuration a program runs under. It carries the active language model, the adapter, any callbacks, and execution settings like thread count. Programs read it implicitly through a given, so you configure once and every program in scope picks it up.

Setting it

There are two ways to install a context:

• RuntimeEnvironment.configure(ctx) sets a global default for the current thread.
• RuntimeEnvironment.withSettings(ctx) { ... } installs a context just for the duration of a block.

The Quickstart shows the full wiring of a model and adapter into a context.

Scoped overrides

withSettings is the tool for changing one setting temporarily. Here a question is answered under the default model, then again under a different model, scoped to a block:

def askWithOverride(question: String, overrideModel: String)(using
    ctx: RuntimeContext
): Either[DspyError, (String, String)] =
  for
    base   <- ask(question) // current/global LM
    other  <- OpenAiLanguageModel.fromEnv(overrideModel)
    scoped <- RuntimeEnvironment.withSettings(ctx.copy(lm = Some(other))) {
                given RuntimeContext = RuntimeEnvironment.current
                ask(question)
              }
  yield (base, scoped)

The override applies only inside the block; outside it, the original context is unchanged. The same pattern swaps the adapter, adds callbacks, or changes any other context field.

What the context carries

Field	Purpose
lm	The active language model.
adapter	The active adapter.
callbacks	Handlers for the observability event stream.
trackUsage	Whether to record token usage.

Next: Observability.