From 3df5540dea76309c5aed0320c39688c8db9d3e71 Mon Sep 17 00:00:00 2001
From: Claude <noreply@anthropic.com>
Date: Tue, 21 Jul 2026 14:11:11 +0000
Subject: [PATCH] fix: render SSR-enabled build entries once by teeing the RSC
 stream
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When ssr is enabled, build() rendered the identical element through two
separate renderToReadableStream calls — one for SSR HTML and one for the
app RSC payload. Every server component (and defer() call) therefore
executed twice per entry. Render once and tee() the stream instead, so
both consumers see byte-identical streams with half the rendering work.

Closes #147

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01ShuMmxpPtcxZrHMQZdbq2a
---
 packages/static/src/rsc/entry.tsx | 11 +++++------
 1 file changed, 5 insertions(+), 6 deletions(-)

diff --git a/packages/static/src/rsc/entry.tsx b/packages/static/src/rsc/entry.tsx
index f3361d0..113fe41 100644
--- a/packages/static/src/rsc/entry.tsx
+++ b/packages/static/src/rsc/entry.tsx
@@ -293,13 +293,12 @@ export async function build() {
     let appRscStream: ReadableStream<Uint8Array>;
 
     if (ssrEnabled) {
-      // SSR on: both streams have full tree
-      rootRscStream = renderToReadableStream<RscPayload>({
+      // SSR on: render the full tree once and tee the stream — one branch
+      // for SSR HTML, one for the app RSC payload. Rendering twice would
+      // execute every server component (and defer()) twice per entry (#147).
+      [rootRscStream, appRscStream] = renderToReadableStream<RscPayload>({
         root: <Root>{appNode}</Root>,
-      });
-      appRscStream = renderToReadableStream<RscPayload>({
-        root: <Root>{appNode}</Root>,
-      });
+      }).tee();
     } else {
       // SSR off: root stream has shell, app stream has App only
       rootRscStream = renderToReadableStream<RscPayload>({