Errors and retries

Failures surface as typed AIError cases:

do {
  let result = try await generateText(model: model, prompt: prompt)
} catch let AIError.http(status, body) {
  // 4xx/5xx with the provider's error body
} catch AIError.noObjectGenerated {
  // structured output did not parse or validate
} catch {
  // transport errors, cancellation
}

Other cases include .decoding, .invalidRequest, .unknownTool, and .transport. The tool layer adds .invalidToolInput, .invalidToolContext, .missingToolResults, .toolCallRepairFailed, and .invalidToolApproval; .timedOut(scope:limit:tool:) reports which timeout fired, .unsupportedFunctionality marks a capability the provider or platform does not offer, and .authorizationRequired(url:) carries the sign-in URL when an MCP server needs OAuth. Streaming surfaces errors by throwing from the stream you iterate.

Retries

Every request path retries transient failures with exponential backoff. maxRetries (default 2) counts retries after the first attempt; set 0 to disable:

let result = try await generateText(
  model: model,
  prompt: prompt,
  maxRetries: 4
)

Establishing a stream is retryable; a stream that already delivered parts is not, so you never see duplicated tokens.