diff --git a/packages/opencode/src/session/compaction.ts b/packages/opencode/src/session/compaction.ts
index 9245426057c..7a69c1a1a32 100644
--- a/packages/opencode/src/session/compaction.ts
+++ b/packages/opencode/src/session/compaction.ts
@@ -91,6 +91,8 @@ export namespace SessionCompaction {
       for (const part of toPrune) {
         if (part.state.status === "completed") {
           part.state.time.compacted = Date.now()
+          part.state.output = ""
+          part.state.attachments = []
           await Session.updatePart(part)
         }
       }