Async and sync modes - Era SDK

Mode	Context returned	Default timeout	Best for
`async`	Previous turn	2 seconds	Interactive chat
`sync`	Current turn	30 seconds	Evals and background work

Async mode (default)

const era = new Era({ ..., mode: "async" });

Async mode keeps Era’s analysis out of the response path. On turn 2, Era returns the block prepared from turn 1 while it prepares turn 2 for the next call.

Call	Result
Turn 1	`""` because no earlier block exists
Turn 2	Context prepared from turn 1
Turn 3	Context prepared from turn 2

The call still waits for a normal API round trip.

Sync mode

const era = new Era({ ..., mode: "sync" });

Sync mode waits for Era to analyze the latest user message. It can return a block on the first turn, but it adds the full processing time before your model call. Use sync mode when:

You are running an evaluation.
The work runs in the background.
Current-turn context matters more than response time.

Change the timeout

const era = new Era({
  mode: "sync",
  timeoutMs: 60_000,
});

timeoutMs applies to each request attempt. A timeout is treated as a transient failure and can be retried up to maxRetries. If no attempt succeeds, turnContext() returns "".

Recommendation

Start with async for user-facing chat. Choose sync only when you have a specific need for current-turn context.