diff --git a/lib/src/main/java/com/diffplug/spotless/ForeignExe.java b/lib/src/main/java/com/diffplug/spotless/ForeignExe.java
index 4cb15d1a8a..43846a2c9e 100644
--- a/lib/src/main/java/com/diffplug/spotless/ForeignExe.java
+++ b/lib/src/main/java/com/diffplug/spotless/ForeignExe.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2020-2023 DiffPlug
+ * Copyright 2020-2024 DiffPlug
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -16,6 +16,7 @@
 package com.diffplug.spotless;
 
 import java.io.IOException;
+import java.io.Serializable;
 import java.nio.charset.Charset;
 import java.util.Objects;
 import java.util.regex.Matcher;
@@ -31,7 +32,8 @@
  * Usage: {@code ForeignExe.nameAndVersion("grep", "2.5.7").confirmVersionAndGetAbsolutePath()}
  * will find grep, confirm that it is version 2.5.7, and then return.
  */
-public class ForeignExe {
+public class ForeignExe implements Serializable {
+	private static final long serialVersionUID = 1L;
 	private @Nullable String pathToExe;
 	private String versionFlag = "--version";
 	private Pattern versionRegex = Pattern.compile("version (\\S*)");
diff --git a/lib/src/main/java/com/diffplug/spotless/cpp/ClangFormatStep.java b/lib/src/main/java/com/diffplug/spotless/cpp/ClangFormatStep.java
index 5591045505..345ac723c3 100644
--- a/lib/src/main/java/com/diffplug/spotless/cpp/ClangFormatStep.java
+++ b/lib/src/main/java/com/diffplug/spotless/cpp/ClangFormatStep.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2020-2022 DiffPlug
+ * Copyright 2020-2024 DiffPlug
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -64,10 +64,10 @@ public ClangFormatStep withPathToExe(String pathToExe) {
 	}
 
 	public FormatterStep create() {
-		return FormatterStep.createLazy(name(), this::createState, State::toFunc);
+		return FormatterStep.createLazy(name(), this::createState, RoundtripState::state, State::toFunc);
 	}
 
-	private State createState() throws IOException, InterruptedException {
+	private RoundtripState createState() throws IOException, InterruptedException {
 		String howToInstall = "" +
 				"You can download clang-format from https://releases.llvm.org and " +
 				"then point Spotless to it with {@code pathToExe('/path/to/clang-format')} " +
@@ -82,7 +82,25 @@ private State createState() throws IOException, InterruptedException {
 				.fixWrongVersion(
 						"You can tell Spotless to use the version you already have with {@code clangFormat('{versionFound}')}" +
 								"or you can download the currently specified version, {version}.\n" + howToInstall);
-		return new State(this, exe);
+		return new RoundtripState(this, exe);
+	}
+
+	static class RoundtripState implements Serializable {
+		private static final long serialVersionUID = 1L;
+
+		final String version;
+		final @Nullable String style;
+		final ForeignExe exe;
+
+		RoundtripState(ClangFormatStep step, ForeignExe exe) {
+			this.version = step.version;
+			this.style = step.style;
+			this.exe = exe;
+		}
+
+		private State state() {
+			return new State(version, style, exe);
+		}
 	}
 
 	@SuppressFBWarnings("SE_TRANSIENT_FIELD_NOT_RESTORED")
@@ -95,9 +113,9 @@ static class State implements Serializable {
 		// used for executing
 		private transient @Nullable List<String> args;
 
-		State(ClangFormatStep step, ForeignExe pathToExe) {
-			this.version = step.version;
-			this.style = step.style;
+		State(String version, @Nullable String style, ForeignExe pathToExe) {
+			this.version = version;
+			this.style = style;
 			this.exe = Objects.requireNonNull(pathToExe);
 		}
 
diff --git a/lib/src/main/java/com/diffplug/spotless/protobuf/BufStep.java b/lib/src/main/java/com/diffplug/spotless/protobuf/BufStep.java
index ac39eac935..4fc087ad7a 100644
--- a/lib/src/main/java/com/diffplug/spotless/protobuf/BufStep.java
+++ b/lib/src/main/java/com/diffplug/spotless/protobuf/BufStep.java
@@ -58,16 +58,32 @@ public BufStep withPathToExe(String pathToExe) {
 	}
 
 	public FormatterStep create() {
-		return FormatterStep.createLazy(name(), this::createState, State::toFunc);
+		return FormatterStep.createLazy(name(), this::createRoundtrip, RoundtripState::state, State::toFunc);
 	}
 
-	private State createState() {
+	private RoundtripState createRoundtrip() {
 		String instructions = "https://docs.buf.build/installation";
 		ForeignExe exe = ForeignExe.nameAndVersion("buf", version)
 				.pathToExe(pathToExe)
 				.versionRegex(Pattern.compile("(\\S*)"))
 				.fixCantFind("Try following the instructions at " + instructions + ", or else tell Spotless where it is with {@code buf().pathToExe('path/to/executable')}");
-		return new State(this, exe);
+		return new RoundtripState(version, exe);
+	}
+
+	private static class RoundtripState implements Serializable {
+		private static final long serialVersionUID = 1L;
+
+		final String version;
+		final ForeignExe exe;
+
+		RoundtripState(String version, ForeignExe exe) {
+			this.version = version;
+			this.exe = exe;
+		}
+
+		private State state() {
+			return new State(version, exe);
+		}
 	}
 
 	@SuppressFBWarnings("SE_TRANSIENT_FIELD_NOT_RESTORED")
@@ -80,9 +96,9 @@ static class State implements Serializable {
 		private final transient ForeignExe exe;
 		private transient String exeAbsPath;
 
-		State(BufStep step, ForeignExe exe) {
-			this.version = step.version;
-			this.exe = Objects.requireNonNull(exe);
+		State(String version, ForeignExe exeAbsPath) {
+			this.version = version;
+			this.exe = Objects.requireNonNull(exeAbsPath);
 		}
 
 		String format(ProcessRunner runner, String input, File file) throws IOException, InterruptedException {
diff --git a/lib/src/main/java/com/diffplug/spotless/python/BlackStep.java b/lib/src/main/java/com/diffplug/spotless/python/BlackStep.java
index 9bce2241dd..9fe26cdae8 100644
--- a/lib/src/main/java/com/diffplug/spotless/python/BlackStep.java
+++ b/lib/src/main/java/com/diffplug/spotless/python/BlackStep.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2020-2022 DiffPlug
+ * Copyright 2020-2024 DiffPlug
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -56,17 +56,33 @@ public BlackStep withPathToExe(String pathToExe) {
 	}
 
 	public FormatterStep create() {
-		return FormatterStep.createLazy(name(), this::createState, State::toFunc);
+		return FormatterStep.createLazy(name(), this::createState, RoundtripState::state, State::toFunc);
 	}
 
-	private State createState() throws IOException, InterruptedException {
+	private RoundtripState createState() {
 		String trackingIssue = "\n  github issue to handle this better: https://github.com/diffplug/spotless/issues/674";
 		ForeignExe exeAbsPath = ForeignExe.nameAndVersion("black", version)
 				.pathToExe(pathToExe)
 				.versionRegex(Pattern.compile("(?:black, version|black,|version) (\\S*)"))
 				.fixCantFind("Try running {@code pip install black=={version}}, or else tell Spotless where it is with {@code black().pathToExe('path/to/executable')}" + trackingIssue)
 				.fixWrongVersion("Try running {@code pip install --force-reinstall black=={version}}, or else specify {@code black('{versionFound}')} to Spotless" + trackingIssue);
-		return new State(this, exeAbsPath);
+		return new RoundtripState(version, exeAbsPath);
+	}
+
+	static class RoundtripState implements Serializable {
+		private static final long serialVersionUID = 1L;
+
+		final String version;
+		final ForeignExe exe;
+
+		RoundtripState(String version, ForeignExe exe) {
+			this.version = version;
+			this.exe = exe;
+		}
+
+		private State state() {
+			return new State(version, exe);
+		}
 	}
 
 	@SuppressFBWarnings("SE_TRANSIENT_FIELD_NOT_RESTORED")
@@ -78,8 +94,8 @@ static class State implements Serializable {
 		// used for executing
 		private transient @Nullable String[] args;
 
-		State(BlackStep step, ForeignExe exeAbsPath) {
-			this.version = step.version;
+		State(String version, ForeignExe exeAbsPath) {
+			this.version = version;
 			this.exe = Objects.requireNonNull(exeAbsPath);
 		}
 
diff --git a/testlib/src/main/java/com/diffplug/spotless/StepHarnessBase.java b/testlib/src/main/java/com/diffplug/spotless/StepHarnessBase.java
index c82de128a1..f9b5864d7f 100644
--- a/testlib/src/main/java/com/diffplug/spotless/StepHarnessBase.java
+++ b/testlib/src/main/java/com/diffplug/spotless/StepHarnessBase.java
@@ -17,6 +17,7 @@
 
 import java.util.Locale;
 import java.util.Objects;
+import java.util.Set;
 
 import org.assertj.core.api.Assertions;
 
@@ -48,6 +49,8 @@ protected StepHarnessBase(Formatter formatter) {
 				supportsRoundTrip = true;
 			} else if (onlyStepName.equals("fence")) {
 				supportsRoundTrip = true;
+			} else if (Set.of("black", "buf", "clang").contains(onlyStepName)) {
+				supportsRoundTrip = true;
 			}
 		}
 	}