# SessionPropertyValues A container for property values. ``` final class SessionPropertyValues ``` ## Overview Use session property values across your session. To help manage the context window, access [`history`](/documentation/FoundationModels/SessionPropertyValues/history) to modify the transcript for the session: ```swift struct CompactingProfile: LanguageModelSession.DynamicProfile { @SessionProperty(\.history) var history var body: some LanguageModelSession.DynamicProfile { Profile { // Custom instructions and tools that you define. } .onResponse { _ in // Compact the history when the entries exceed a certain limit. if history.count > 100 { history = Array(history.suffix(50)) } } } } ``` Because updating the transcript history can cause cache invalidations for some models, carefully consider how you modify an existing transcript. For more information, see [Optimizing key-value caching in language model sessions](/documentation/FoundationModels/optimizing-key-value-caching-in-language-model-sessions). Use [`SessionPropertyEntry()`](/documentation/FoundationModels/SessionPropertyEntry()) to create custom session properties. ## Topics ### Accessing the session history and instructions [`var history: Transcript.HistoryView`](/documentation/FoundationModels/SessionPropertyValues/history) The history portion of the session’s transcript. ### Accessing the subscript [`subscript(K.Type) -> K.Value`](/documentation/FoundationModels/SessionPropertyValues/subscript(_:)) Accesses the value stored for the given session property key. ## Relationships ### Conforms To [`Copyable`](/documentation/Swift/Copyable) [`Escapable`](/documentation/Swift/Escapable) [`Observable`](/documentation/Observation/Observable) [`SendableMetatype`](/documentation/Swift/SendableMetatype) [`Sendable`](/documentation/Swift/Sendable) --- Copyright © 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)