From c19e2dd363e55f211fafb9c2fc82d27d8f437ebb Mon Sep 17 00:00:00 2001
From: Jinwoo Hong <73622457+Jinwoo-H@users.noreply.github.com>
Date: Sun, 11 Oct 2026 03:05:10 -0400
Subject: [PATCH] fix(relay-load): reuse an Asia load principal set for shards
 past the fourth (#27403)

Staging auth mints principal sets for shards 0-3, so the second hosted runner's shards 4-7 were
refused. Their hosts stay distinct by peer index; each set carries the same host count as the
proven 4 x 710 run.
---
 cloud/dev/scripts/github-smoke-token.mjs  | 5 ++++-
 cloud/dev/scripts/load-relay-controls.mjs | 6 ++++--
 2 files changed, 8 insertions(+), 3 deletions(-)

diff --git a/cloud/dev/scripts/github-smoke-token.mjs b/cloud/dev/scripts/github-smoke-token.mjs
index f0bd67c1024..af4c61fd52b 100644
--- a/cloud/dev/scripts/github-smoke-token.mjs
+++ b/cloud/dev/scripts/github-smoke-token.mjs
@@ -50,10 +50,13 @@ export async function requestGitHubSmokeTokens(
   }
 }
 
+// Staging auth mints Asia load principal sets for this many shards.
+export const RELAY_ASIA_LOAD_PRINCIPAL_SHARDS = 4
+
 function parseRelayAsiaLoadOptions(value) {
   if (
     !value || typeof value !== 'object' ||
-    !Number.isSafeInteger(value.shardIndex) || value.shardIndex < 0 || value.shardIndex > 3 ||
+    !Number.isSafeInteger(value.shardIndex) || value.shardIndex < 0 || value.shardIndex >= RELAY_ASIA_LOAD_PRINCIPAL_SHARDS ||
     !Number.isSafeInteger(value.principalCount) || value.principalCount < 1 ||
     value.principalCount > 32
   ) throw new Error('Relay Asia load principal request is invalid')
diff --git a/cloud/dev/scripts/load-relay-controls.mjs b/cloud/dev/scripts/load-relay-controls.mjs
index be642bdbeb3..409f83d8f6e 100644
--- a/cloud/dev/scripts/load-relay-controls.mjs
+++ b/cloud/dev/scripts/load-relay-controls.mjs
@@ -3,7 +3,7 @@ import { readFileSync } from 'node:fs'
 import { monitorEventLoopDelay } from 'node:perf_hooks'
 import { setTimeout as delay } from 'node:timers/promises'
 import { RelayLoadControlPeer } from './relay-load-control-peer.mjs'
-import { requestGitHubSmokeTokens } from './github-smoke-token.mjs'
+import { RELAY_ASIA_LOAD_PRINCIPAL_SHARDS, requestGitHubSmokeTokens } from './github-smoke-token.mjs'
 import { relayLoadFailureReason } from './relay-load-connection-failure.mjs'
 import {
   assertRelayLoadDirectorCapacityToken,
@@ -164,7 +164,9 @@ if (!accessToken && !key.signingKey && process.env.ACTIONS_ID_TOKEN_REQUEST_URL
   const loadOptions = config.relayAsiaLoadPrincipalCount > 0
     ? {
         relayAsiaLoad: {
-          shardIndex: config.shardIndex,
+          // Staging auth mints principal sets for shards 0-3 only; shards past that (a second
+          // hosted runner) reuse a set, and their hosts stay distinct by peer index.
+          shardIndex: config.shardIndex % RELAY_ASIA_LOAD_PRINCIPAL_SHARDS,
           principalCount: config.relayAsiaLoadPrincipalCount
         }
       }