From 84e9606e4f9470e0fea39af33dc7d45a49a2473c Mon Sep 17 00:00:00 2001
From: Evan Goode <mail@evangoo.de>
Date: Sun, 23 Mar 2025 17:08:51 -0400
Subject: [PATCH] legacy: handle URL-encoded session ID

---
 .../legacy/fix/online/OnlineModeFix.java              | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/libraries/launcher/legacy/org/prismlauncher/legacy/fix/online/OnlineModeFix.java b/libraries/launcher/legacy/org/prismlauncher/legacy/fix/online/OnlineModeFix.java
index b822d6469..01b7f3e8c 100644
--- a/libraries/launcher/legacy/org/prismlauncher/legacy/fix/online/OnlineModeFix.java
+++ b/libraries/launcher/legacy/org/prismlauncher/legacy/fix/online/OnlineModeFix.java
@@ -84,7 +84,16 @@ public final class OnlineModeFix {
 
         // sessionId has the form:
         // token:<accessToken>:<player UUID>
-        String accessToken = sessionId.split(":")[1];
+        // or, as of Minecraft release 1.3.1, it may be URL encoded:
+        // token%3A<accessToken>%3A<player UUID>
+        String accessToken;
+        if (sessionId.contains(":")) {
+            accessToken = sessionId.split(":")[1];
+        } else if (sessionId.contains("%3A")) {
+            accessToken = sessionId.split("%3A")[1];
+        } else {
+            throw new AssertionError("invalid sessionId");
+        }
 
         String uuid = null;
         uuid = MojangApi.getUuid(user, proxy);