diff --git a/launcher-package/integration-test/src/test/scala/ScriptTest.scala b/launcher-package/integration-test/src/test/scala/ScriptTest.scala
index 222987887..a14f8a97c 100644
--- a/launcher-package/integration-test/src/test/scala/ScriptTest.scala
+++ b/launcher-package/integration-test/src/test/scala/ScriptTest.scala
@@ -208,6 +208,17 @@ object SbtScriptTest extends SimpleTestSuite with PowerAssertions {
     )
   }
 
+  // Regression test for https://github.com/sbt/sbt/issues/8100
+  // Debug agent output in SBT_OPTS should not break the launcher on Windows
+  makeTest(
+    "sbt with debug agent in SBT_OPTS",
+    sbtOpts = "-agentlib:jdwp=transport=dt_socket,server=y,suspend=n,address=12346"
+  )("-v") { out: List[String] =>
+    assert(
+      out.contains[String]("-agentlib:jdwp=transport=dt_socket,server=y,suspend=n,address=12346")
+    )
+  }
+
   makeTest("sbt --no-share adds three system properties")("--no-share") { out: List[String] =>
     assert(out.contains[String]("-Dsbt.global.base=project/.sbtboot"))
     assert(out.contains[String]("-Dsbt.boot.directory=project/.boot"))
diff --git a/launcher-package/src/universal/bin/sbt.bat b/launcher-package/src/universal/bin/sbt.bat
index cbc925aed..13bdbb5d3 100755
--- a/launcher-package/src/universal/bin/sbt.bat
+++ b/launcher-package/src/universal/bin/sbt.bat
@@ -980,7 +980,9 @@ exit /B 1
 :copyrt
 if /I !JAVA_VERSION! GEQ 9 (
   "!_JAVACMD!" !_JAVA_OPTS! !_SBT_OPTS! -jar "!sbt_jar!" --rt-ext-dir > "%TEMP%.\rtext.txt"
-  set /p java9_ext= < "%TEMP%.\rtext.txt"
+  rem Filter for the line containing java9-rt-ext- to avoid picking up debug agent output
+  set "java9_ext="
+  for /f "tokens=*" %%a in ('findstr /c:"java9-rt-ext-" "%TEMP%.\rtext.txt"') do set "java9_ext=%%a"
   set "java9_rt=!java9_ext!\rt.jar"
 
   if not exist "!java9_rt!" (