---
title: "LanguageModelSession.GenerationError.exceededContextWindowSize(_:)"
framework: foundationmodels
role: symbol
role_heading: Case
path: "foundationmodels/languagemodelsession/generationerror/exceededcontextwindowsize(_:)"
---

# LanguageModelSession.GenerationError.exceededContextWindowSize(_:)

An error that signals the session reached its context window size limit.

## Declaration

```swift
case exceededContextWindowSize(LanguageModelSession.GenerationError.Context)
```

## Discussion

Discussion This error occurs when you use the available tokens for the context window of 4,096 tokens. The token count includes instructions, prompts, and outputs for a session instance. A single token corresponds to approximately three to four characters in languages like English, Spanish, or German, and one token per character in languages like Japanese, Chinese, and Korean. Start a new session when you exceed the content window size, and try again using a shorter prompt or shorter output length. For more information on managing the context window size, see Managing the context window.

## See Also

### Generation errors

- [LanguageModelSession.GenerationError.assetsUnavailable(_:)](foundationmodels/languagemodelsession/generationerror/assetsunavailable(_:).md)
- [LanguageModelSession.GenerationError.decodingFailure(_:)](foundationmodels/languagemodelsession/generationerror/decodingfailure(_:).md)
- [LanguageModelSession.GenerationError.guardrailViolation(_:)](foundationmodels/languagemodelsession/generationerror/guardrailviolation(_:).md)
- [LanguageModelSession.GenerationError.rateLimited(_:)](foundationmodels/languagemodelsession/generationerror/ratelimited(_:).md)
- [LanguageModelSession.GenerationError.refusal(_:_:)](foundationmodels/languagemodelsession/generationerror/refusal(_:_:).md)
- [LanguageModelSession.GenerationError.concurrentRequests(_:)](foundationmodels/languagemodelsession/generationerror/concurrentrequests(_:).md)
- [LanguageModelSession.GenerationError.unsupportedGuide(_:)](foundationmodels/languagemodelsession/generationerror/unsupportedguide(_:).md)
- [LanguageModelSession.GenerationError.unsupportedLanguageOrLocale(_:)](foundationmodels/languagemodelsession/generationerror/unsupportedlanguageorlocale(_:).md)
- [LanguageModelSession.GenerationError.Context](foundationmodels/languagemodelsession/generationerror/context.md)
- [LanguageModelSession.GenerationError.Refusal](foundationmodels/languagemodelsession/generationerror/refusal.md)