diff --git a/packages/opencode/src/session/compaction.ts b/packages/opencode/src/session/compaction.ts
index aaee2be2feba..254e6e5e2aba 100644
--- a/packages/opencode/src/session/compaction.ts
+++ b/packages/opencode/src/session/compaction.ts
@@ -405,6 +405,7 @@ export const layer: Layer.Layer<
       const modelMessages = yield* MessageV2.toModelMessagesEffect(msgs, model, {
         stripMedia: true,
         toolOutputMaxChars: TOOL_OUTPUT_MAX_CHARS,
+        stripReasoning: true,
       })
       const ctx = yield* InstanceState.context
       const msg: MessageV2.Assistant = {
diff --git a/packages/opencode/src/session/message-v2.ts b/packages/opencode/src/session/message-v2.ts
index 911f58efd0b9..7bf7866f0d55 100644
--- a/packages/opencode/src/session/message-v2.ts
+++ b/packages/opencode/src/session/message-v2.ts
@@ -729,7 +729,7 @@ function providerMeta(metadata: Record<string, any> | undefined) {
 export const toModelMessagesEffect = Effect.fnUntraced(function* (
   input: WithParts[],
   model: Provider.Model,
-  options?: { stripMedia?: boolean; toolOutputMaxChars?: number },
+  options?: { stripMedia?: boolean; toolOutputMaxChars?: number; stripReasoning?: boolean },
 ) {
   const result: UIMessage[] = []
   const toolNames = new Set<string>()
@@ -938,10 +938,11 @@ export const toModelMessagesEffect = Effect.fnUntraced(function* (
             })
         }
         if (part.type === "reasoning") {
+          if (options?.stripReasoning || differentModel) continue
           assistantMessage.parts.push({
             type: "reasoning",
             text: part.text,
-            ...(differentModel ? {} : { providerMetadata: part.metadata }),
+            providerMetadata: part.metadata,
           })
         }
       }
@@ -986,7 +987,7 @@ export const toModelMessagesEffect = Effect.fnUntraced(function* (
 export function toModelMessages(
   input: WithParts[],
   model: Provider.Model,
-  options?: { stripMedia?: boolean; toolOutputMaxChars?: number },
+  options?: { stripMedia?: boolean; toolOutputMaxChars?: number; stripReasoning?: boolean },
 ): Promise<ModelMessage[]> {
   return Effect.runPromise(toModelMessagesEffect(input, model, options).pipe(Effect.provide(EffectLogger.layer)))
 }