From 217fef600dd05772bf6cf773877ea13d08aa1cbb Mon Sep 17 00:00:00 2001
From: Tim Smart <hello@timsmart.co>
Date: Fri, 17 Apr 2026 09:57:11 +1200
Subject: [PATCH] backport cluster serialization fix for notify path

---
 .changeset/major-lands-shake.md |  5 +++++
 packages/cluster/src/Runners.ts | 16 ++++++++++------
 2 files changed, 15 insertions(+), 6 deletions(-)
 create mode 100644 .changeset/major-lands-shake.md

diff --git a/.changeset/major-lands-shake.md b/.changeset/major-lands-shake.md
new file mode 100644
index 00000000000..7d1349f30e7
--- /dev/null
+++ b/.changeset/major-lands-shake.md
@@ -0,0 +1,5 @@
+---
+"@effect/cluster": patch
+---
+
+backport cluster serialization fix for notify path
diff --git a/packages/cluster/src/Runners.ts b/packages/cluster/src/Runners.ts
index e675f24362c..c69b9a7764c 100644
--- a/packages/cluster/src/Runners.ts
+++ b/packages/cluster/src/Runners.ts
@@ -590,12 +590,16 @@ export const makeRpc: Effect.Effect<
       if (Option.isNone(address)) {
         return Effect.void
       }
-      const envelope = message.envelope
-      return RcMap.get(clients, address.value).pipe(
-        Effect.flatMap((client) => client.Notify({ envelope })),
-        Effect.scoped,
-        Effect.ignore
-      )
+      const encode: Effect.Effect<Envelope.AckChunk | Envelope.Interrupt | Envelope.Envelope.PartialEncoded> =
+        message._tag === "OutgoingRequest"
+          ? Effect.orDie(Message.serializeRequest(message))
+          : Effect.succeed(message.envelope)
+      return Effect.flatMap(encode, (envelope) =>
+        RcMap.get(clients, address.value).pipe(
+          Effect.flatMap((client) => client.Notify({ envelope })),
+          Effect.scoped,
+          Effect.ignore
+        ))
     },
     onRunnerUnavailable: (address) => RcMap.invalidate(clients, address)
   })