diff --git a/main/src/main/scala/sbt/Defaults.scala b/main/src/main/scala/sbt/Defaults.scala
index 1c24bda64..9cabf774a 100644
--- a/main/src/main/scala/sbt/Defaults.scala
+++ b/main/src/main/scala/sbt/Defaults.scala
@@ -3633,6 +3633,7 @@ object Classpaths {
                   .withArtifactFilter(
                     updateConfig0.artifactFilter.map(af => af.withInverted(!af.inverted))
                   )
+                  .withMissingOk(true)
                 val app = appConfiguration.value
                 val srcTypes = sourceArtifactTypes.value
                 val docTypes = docArtifactTypes.value
@@ -3718,11 +3719,14 @@ object Classpaths {
       val ref = thisProjectRef.value
       val unit = loadedBuild.value.units(ref.build).unit
       val converter = unit.converter
-      val pluginClasspath = unit.plugins.pluginData.dependencyClasspath.toVector
+      val pluginData = unit.plugins.pluginData
+      val pluginInternalCp = pluginData.internalDependencyClasspath.toVector
+      val pluginClasspath = pluginData.dependencyClasspath.toVector
+      val cp = pluginClasspath.diff(pluginInternalCp)
       // Exclude directories: an approximation to whether they've been published
       // Note: it might be a redundant legacy from sbt 0.13/1.x times where the classpath contained directories
       // but it's left just in case
-      val pluginJars = pluginClasspath.filter: x =>
+      val pluginJars = cp.filter: x =>
         !Files.isDirectory(converter.toPath(x.data))
       val pluginIDs: Vector[ModuleID] = pluginJars.flatMap(_.get(moduleIDStr).map: str =>
         moduleIdJsonKeyFormat.read(str))
diff --git a/main/src/main/scala/sbt/EvaluateTask.scala b/main/src/main/scala/sbt/EvaluateTask.scala
index a7eb82ba8..208407585 100644
--- a/main/src/main/scala/sbt/EvaluateTask.scala
+++ b/main/src/main/scala/sbt/EvaluateTask.scala
@@ -142,6 +142,10 @@ object EvaluateTaskConfig {
   ) extends EvaluateTaskConfig
 }
 
+/**
+ * @param internalDependencyClasspath internal classpath entries from the metabuild that are used to exclude
+ *                                    them when resolving/retrieving classifiers for sbt.
+ */
 final case class PluginData(
     dependencyClasspath: Def.Classpath,
     definitionClasspath: Def.Classpath,
@@ -155,13 +159,28 @@ final case class PluginData(
     managedSources: Seq[File],
     buildTarget: Option[BuildTargetIdentifier],
     converter: FileConverter,
+    internalDependencyClasspath: Def.Classpath,
 ) {
   val classpath: Def.Classpath = definitionClasspath ++ dependencyClasspath
 }
 
 object PluginData {
   private[sbt] def apply(dependencyClasspath: Def.Classpath, converter: FileConverter): PluginData =
-    PluginData(dependencyClasspath, Nil, None, None, Nil, Nil, Nil, Nil, Nil, Nil, None, converter)
+    PluginData(
+      dependencyClasspath,
+      Nil,
+      None,
+      None,
+      Nil,
+      Nil,
+      Nil,
+      Nil,
+      Nil,
+      Nil,
+      None,
+      converter,
+      Nil
+    )
 }
 
 object EvaluateTask {
diff --git a/main/src/main/scala/sbt/internal/Load.scala b/main/src/main/scala/sbt/internal/Load.scala
index 88da9128f..0960d853e 100755
--- a/main/src/main/scala/sbt/internal/Load.scala
+++ b/main/src/main/scala/sbt/internal/Load.scala
@@ -1381,6 +1381,7 @@ private[sbt] object Load {
       isMetaBuild :== true,
       pluginData := Def.uncached {
         val prod = (Configurations.Runtime / exportedProducts).value
+        val internalCp = (Configurations.Runtime / internalDependencyClasspath).value
         val cp = (Configurations.Runtime / fullClasspath).value
         val opts = (Configurations.Compile / scalacOptions).value
         val javaOpts = (Configurations.Compile / javacOptions).value
@@ -1403,6 +1404,7 @@ private[sbt] object Load {
           managedSrcs,
           Some(buildTarget),
           converter,
+          internalCp,
         )
       },
       onLoadMessage := ("loading project definition from " + baseDirectory.value)
@@ -1670,6 +1672,7 @@ final case class LoadBuildConfiguration(
           Nil,
           None,
           converter,
+          Nil
         )
       case None => PluginData(globalPluginClasspath, converter)
     }
diff --git a/sbt-app/src/sbt-test/dependency-management/i8679-update-sbt-classifiers-local-plugin/build.sbt b/sbt-app/src/sbt-test/dependency-management/i8679-update-sbt-classifiers-local-plugin/build.sbt
new file mode 100644
index 000000000..c0f23c1d7
--- /dev/null
+++ b/sbt-app/src/sbt-test/dependency-management/i8679-update-sbt-classifiers-local-plugin/build.sbt
@@ -0,0 +1,39 @@
+lazy val root = (project in file("."))
+  .settings(
+    // Verify that local plugins work
+    TaskKey[Unit]("checkLocalPlugins") := Def.uncached {
+      val localResult = localPluginCheck.value
+      val customResult = customPluginCheck.value
+      assert(localResult == "local-plugin-active", s"Expected local plugin to be active, got: $localResult")
+      assert(customResult == "custom plugin", s"Expected custom plugin to be active, got: $customResult")
+    },
+
+    // Verify that the dependencies in updateSbtClassifiers / classifiersModule do not include the local plugins but do include
+    // other declared dependencies
+    TaskKey[Unit]("checkClassifiersModule") := Def.uncached {
+      val mod = (updateSbtClassifiers / classifiersModule).value
+      val deps = mod.dependencies
+      val actual = deps.map(m => s"${m.organization}:${m.name}").sorted.toSet
+
+      val expected = Set(
+        "org.scala-sbt:sbt",
+        "junit:junit",
+        "com.eed3si9n:sbt-buildinfo_sbt2_3",
+        "org.hamcrest:hamcrest-core",
+        "com.eed3si9n.manifesto:manifesto_3",
+        "org.scala-lang:scala3-library_3",
+        "org.scala-lang:scala-library",
+        "org.typelevel:cats-core_3",
+        "org.typelevel:cats-kernel_3"
+      )
+
+      assert(
+        actual == expected,
+        s"""
+           |ClassifiersModule dependencies mismatch.
+           |Expected: ${expected.mkString(", ")}
+           |Actual:   ${actual.mkString(", ")}
+          """.stripMargin
+      )
+    }
+  )
diff --git a/sbt-app/src/sbt-test/dependency-management/i8679-update-sbt-classifiers-local-plugin/project/LocalPlugin.scala b/sbt-app/src/sbt-test/dependency-management/i8679-update-sbt-classifiers-local-plugin/project/LocalPlugin.scala
new file mode 100644
index 000000000..1eee43635
--- /dev/null
+++ b/sbt-app/src/sbt-test/dependency-management/i8679-update-sbt-classifiers-local-plugin/project/LocalPlugin.scala
@@ -0,0 +1,17 @@
+import sbt.*
+import sbt.Keys.*
+
+object LocalPlugin extends AutoPlugin {
+  override def requires: Plugins = plugins.JvmPlugin
+  override def trigger: PluginTrigger = allRequirements
+
+  object autoImport {
+    val localPluginCheck = taskKey[String]("A task provided by the local plugin")
+  }
+
+  import autoImport.*
+
+  override lazy val projectSettings: Seq[Setting[?]] = Seq(
+    localPluginCheck := "local-plugin-active"
+  )
+}
diff --git a/sbt-app/src/sbt-test/dependency-management/i8679-update-sbt-classifiers-local-plugin/project/build.sbt b/sbt-app/src/sbt-test/dependency-management/i8679-update-sbt-classifiers-local-plugin/project/build.sbt
new file mode 100644
index 000000000..de5bb733e
--- /dev/null
+++ b/sbt-app/src/sbt-test/dependency-management/i8679-update-sbt-classifiers-local-plugin/project/build.sbt
@@ -0,0 +1,16 @@
+lazy val meta = (project in file("."))
+  .settings(
+    // Just to make the test more comprehensive and check whether the additional libraries/plugins
+    // are present in updateSbtClassifiers/classifiersModule.
+    addSbtPlugin("com.eed3si9n" % "sbt-buildinfo" % "0.13.1"),
+    libraryDependencies += "junit" % "junit" % "4.13.2"
+  )
+  .dependsOn(customPlugin)
+
+lazy val customPlugin = (project in file("custom"))
+  .enablePlugins(SbtPlugin)
+  .settings(
+    libraryDependencies ++= Seq(
+      "org.typelevel" %% "cats-core" % "2.13.0",
+    )
+  )
\ No newline at end of file
diff --git a/sbt-app/src/sbt-test/dependency-management/i8679-update-sbt-classifiers-local-plugin/project/custom/src/main/scala/CustomPlugin.scala b/sbt-app/src/sbt-test/dependency-management/i8679-update-sbt-classifiers-local-plugin/project/custom/src/main/scala/CustomPlugin.scala
new file mode 100644
index 000000000..c0b64b856
--- /dev/null
+++ b/sbt-app/src/sbt-test/dependency-management/i8679-update-sbt-classifiers-local-plugin/project/custom/src/main/scala/CustomPlugin.scala
@@ -0,0 +1,20 @@
+import sbt.*
+import sbt.Keys.*
+
+object CustomPlugin extends AutoPlugin {
+  override def requires: Plugins = plugins.JvmPlugin
+  override def trigger: PluginTrigger = allRequirements
+
+  object autoImport {
+    val customPluginCheck = taskKey[String]("A task provided by the custom plugin")
+  }
+
+  import autoImport.*
+
+  override lazy val projectSettings: Seq[Setting[?]] = Seq(
+    customPluginCheck := {
+      import cats.implicits.*
+      List("custom", " ", "plugin").combineAll
+    }
+  )
+}
diff --git a/sbt-app/src/sbt-test/dependency-management/i8679-update-sbt-classifiers-local-plugin/test b/sbt-app/src/sbt-test/dependency-management/i8679-update-sbt-classifiers-local-plugin/test
new file mode 100644
index 000000000..8a6a426a0
--- /dev/null
+++ b/sbt-app/src/sbt-test/dependency-management/i8679-update-sbt-classifiers-local-plugin/test
@@ -0,0 +1,8 @@
+# Verify the local plugins are loaded and active
+> checkLocalPlugins
+
+# Verify the local plugins are not included in the classifiersModule dependencies
+> checkClassifiersModule
+
+# Also verify updateSbtClassifiers itself succeeds
+> updateSbtClassifiers
diff --git a/sbt-app/src/sbt-test/dependency-management/i8679-update-sbt-classifiers-missingok/build.sbt b/sbt-app/src/sbt-test/dependency-management/i8679-update-sbt-classifiers-missingok/build.sbt
new file mode 100644
index 000000000..1b0629c23
--- /dev/null
+++ b/sbt-app/src/sbt-test/dependency-management/i8679-update-sbt-classifiers-missingok/build.sbt
@@ -0,0 +1,11 @@
+lazy val root = (project in file("."))
+  .settings(
+    // Inject a non-existent module into the classifiers module dependencies
+    // to simulate a scenario where classifier artifacts can't be downloaded.
+    // With missingOk=true, updateSbtClassifiers should still succeed.
+    updateSbtClassifiers / classifiersModule := {
+      val mod = (updateSbtClassifiers / classifiersModule).value
+      val fakeModule = "com.example.nonexistent" % "fake-library" % "0.0.1"
+      mod.withDependencies(mod.dependencies :+ fakeModule)
+    },
+  )
diff --git a/sbt-app/src/sbt-test/dependency-management/i8679-update-sbt-classifiers-missingok/project/plugins.sbt b/sbt-app/src/sbt-test/dependency-management/i8679-update-sbt-classifiers-missingok/project/plugins.sbt
new file mode 100644
index 000000000..ddfa827f9
--- /dev/null
+++ b/sbt-app/src/sbt-test/dependency-management/i8679-update-sbt-classifiers-missingok/project/plugins.sbt
@@ -0,0 +1 @@
+addSbtPlugin("com.eed3si9n" % "sbt-buildinfo" % "0.13.1")
diff --git a/sbt-app/src/sbt-test/dependency-management/i8679-update-sbt-classifiers-missingok/test b/sbt-app/src/sbt-test/dependency-management/i8679-update-sbt-classifiers-missingok/test
new file mode 100644
index 000000000..00ad751bf
--- /dev/null
+++ b/sbt-app/src/sbt-test/dependency-management/i8679-update-sbt-classifiers-missingok/test
@@ -0,0 +1 @@
+> updateSbtClassifiers