diff --git a/.chronus/changes/optional-encode-2024-8-14-9-51-14.md b/.chronus/changes/optional-encode-2024-8-14-9-51-14.md
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+---
+changeKind: breaking
+packages:
+  - "@azure-tools/typespec-client-generator-core"
+---
+
+1. change `encode` in `SdkBuiltInType` to optional.
+2. no longer use the value of `kind` as `encode` when there is no encode on this type.