From ba99e033642142c05d1527f1057ca2b2fc069bcf Mon Sep 17 00:00:00 2001
From: Andrea Marziali <andrea.marziali@datadoghq.com>
Date: Tue, 27 Jan 2026 15:49:36 +0100
Subject: [PATCH] Add safety check for TargetSystem encoding limits

---
 .../datadog/trace/agent/tooling/InstrumenterIndex.java    | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/dd-java-agent/agent-tooling/src/main/java/datadog/trace/agent/tooling/InstrumenterIndex.java b/dd-java-agent/agent-tooling/src/main/java/datadog/trace/agent/tooling/InstrumenterIndex.java
index 4270803df89..1595ab7ed0d 100644
--- a/dd-java-agent/agent-tooling/src/main/java/datadog/trace/agent/tooling/InstrumenterIndex.java
+++ b/dd-java-agent/agent-tooling/src/main/java/datadog/trace/agent/tooling/InstrumenterIndex.java
@@ -391,6 +391,14 @@ static boolean decodeModuleHasTargetSystemOverrides(byte flags) {
   }
 
   static short encodeTargetSystems(Set<InstrumenterModule.TargetSystem> targetSystems) {
+    final int allTargetSystemsCount = InstrumenterModule.TargetSystem.values().length;
+    // Safety check to ensure we don’t overflow the index if additional TargetSystem enums are added
+    if (allTargetSystemsCount > 16) {
+      throw new IllegalStateException(
+          "Using a short will only allow encoding 16 different target systems, but found "
+              + allTargetSystemsCount
+              + ". Please use a larger data type for encoding/decoding this field.");
+    }
     short ret = 0;
     for (InstrumenterModule.TargetSystem ts : targetSystems) {
       ret |= (short) (1 << ts.ordinal());