diff --git a/MODULE.bazel b/MODULE.bazel
index d99b016..db00e23 100644
--- a/MODULE.bazel
+++ b/MODULE.bazel
@@ -22,7 +22,7 @@
 bazel_dep(name = "zstd-jni", version = "1.5.2-3.bcr.1")
 bazel_dep(name = "blake3", version = "1.5.1.bcr.1")
 bazel_dep(name = "sqlite3", version = "3.42.0.bcr.1")
-bazel_dep(name = "zlib", version = "1.3")
+bazel_dep(name = "zlib", version = "1.3.1.bcr.3")
 bazel_dep(name = "rules_cc", version = "0.0.9")
 bazel_dep(name = "rules_java", version = "7.6.5")
 bazel_dep(name = "rules_graalvm", version = "0.11.1")
diff --git a/MODULE.bazel.lock b/MODULE.bazel.lock
index 11b62a7..ae99f88 100644
--- a/MODULE.bazel.lock
+++ b/MODULE.bazel.lock
@@ -117,8 +117,9 @@
     "https://bcr.bazel.build/modules/zlib/1.2.11/MODULE.bazel": "07b389abc85fdbca459b69e2ec656ae5622873af3f845e1c9d80fe179f3effa0",
     "https://bcr.bazel.build/modules/zlib/1.2.12/MODULE.bazel": "3b1a8834ada2a883674be8cbd36ede1b6ec481477ada359cd2d3ddc562340b27",
     "https://bcr.bazel.build/modules/zlib/1.2.13/MODULE.bazel": "aa6deb1b83c18ffecd940c4119aff9567cd0a671d7bba756741cb2ef043a29d5",
+    "https://bcr.bazel.build/modules/zlib/1.3.1.bcr.3/MODULE.bazel": "af322bc08976524477c79d1e45e241b6efbeb918c497e8840b8ab116802dda79",
+    "https://bcr.bazel.build/modules/zlib/1.3.1.bcr.3/source.json": "2be409ac3c7601245958cd4fcdff4288be79ed23bd690b4b951f500d54ee6e7d",
     "https://bcr.bazel.build/modules/zlib/1.3/MODULE.bazel": "6a9c02f19a24dcedb05572b2381446e27c272cd383aed11d41d99da9e3167a72",
-    "https://bcr.bazel.build/modules/zlib/1.3/source.json": "b6b43d0737af846022636e6e255fd4a96fee0d34f08f3830e6e0bac51465c37c",
     "https://bcr.bazel.build/modules/zstd-jni/1.5.2-3.bcr.1/MODULE.bazel": "cb11f12dc4c8454bede2b64855a8126b547cc89cf77838188513f647d9edd86e",
     "https://bcr.bazel.build/modules/zstd-jni/1.5.2-3.bcr.1/source.json": "f728c0f2384b4d047a759f4ff5d9cd05a81a78388fbe9cc3981b773e5536be38"
   },
diff --git a/src/MODULE.tools b/src/MODULE.tools
index 82ab204..51e51ac 100644
--- a/src/MODULE.tools
+++ b/src/MODULE.tools
@@ -13,7 +13,7 @@
 bazel_dep(name = "buildozer", version = "7.1.2")
 bazel_dep(name = "platforms", version = "0.0.9")
 bazel_dep(name = "protobuf", version = "3.19.6", repo_name = "com_google_protobuf")
-bazel_dep(name = "zlib", version = "1.3")
+bazel_dep(name = "zlib", version = "1.3.1.bcr.3")
 
 cc_configure = use_extension("//tools/cpp:cc_configure.bzl", "cc_configure_extension")
 use_repo(cc_configure, "local_config_cc", "local_config_cc_toolchains")
diff --git a/src/main/java/com/google/devtools/build/lib/bazel/bzlmod/BUILD b/src/main/java/com/google/devtools/build/lib/bazel/bzlmod/BUILD
index 1c4ed82..02b3a87 100644
--- a/src/main/java/com/google/devtools/build/lib/bazel/bzlmod/BUILD
+++ b/src/main/java/com/google/devtools/build/lib/bazel/bzlmod/BUILD
@@ -26,6 +26,7 @@
     ],
     deps = [
         "//src/main/java/com/google/devtools/build/lib/cmdline",
+        "//src/main/java/com/google/devtools/build/lib/packages/semantics",
         "//src/main/java/net/starlark/java/eval",
         "//third_party:auto_value",
         "//third_party:gson",
@@ -250,6 +251,7 @@
         "//src/main/java/com/google/devtools/build/lib/cmdline",
         "//src/main/java/com/google/devtools/build/lib/events",
         "//src/main/java/com/google/devtools/build/lib/packages",
+        "//src/main/java/com/google/devtools/build/lib/packages/semantics",
         "//src/main/java/com/google/devtools/build/lib/profiler",
         "//src/main/java/com/google/devtools/build/lib/rules:repository/repo_recorded_input",
         "//src/main/java/com/google/devtools/build/lib/rules:repository/repository_directory_value",
diff --git a/src/main/java/com/google/devtools/build/lib/bazel/bzlmod/BazelDepGraphFunction.java b/src/main/java/com/google/devtools/build/lib/bazel/bzlmod/BazelDepGraphFunction.java
index 5770b09..7faf5a1 100644
--- a/src/main/java/com/google/devtools/build/lib/bazel/bzlmod/BazelDepGraphFunction.java
+++ b/src/main/java/com/google/devtools/build/lib/bazel/bzlmod/BazelDepGraphFunction.java
@@ -33,7 +33,9 @@
 import com.google.devtools.build.lib.cmdline.RepositoryMapping;
 import com.google.devtools.build.lib.cmdline.RepositoryName;
 import com.google.devtools.build.lib.packages.LabelConverter;
+import com.google.devtools.build.lib.packages.semantics.BuildLanguageOptions;
 import com.google.devtools.build.lib.server.FailureDetails.ExternalDeps.Code;
+import com.google.devtools.build.lib.skyframe.PrecomputedValue;
 import com.google.devtools.build.lib.vfs.PathFragment;
 import com.google.devtools.build.skyframe.SkyFunction;
 import com.google.devtools.build.skyframe.SkyFunctionException;
@@ -42,6 +44,7 @@
 import com.google.devtools.build.skyframe.SkyValue;
 import java.util.Map.Entry;
 import javax.annotation.Nullable;
+import net.starlark.java.eval.StarlarkSemantics;
 
 /**
  * This function runs Bazel module resolution, extracts the dependency graph from it and creates a
@@ -58,13 +61,14 @@
       throws BazelDepGraphFunctionException, InterruptedException {
     BazelModuleResolutionValue selectionResult =
         (BazelModuleResolutionValue) env.getValue(BazelModuleResolutionValue.KEY);
+    StarlarkSemantics starlarkSemantics = PrecomputedValue.STARLARK_SEMANTICS.get(env);
     if (env.valuesMissing()) {
       return null;
     }
     var depGraph = selectionResult.getResolvedDepGraph();
 
     ImmutableBiMap<RepositoryName, ModuleKey> canonicalRepoNameLookup =
-        computeCanonicalRepoNameLookup(depGraph);
+        computeCanonicalRepoNameLookup(depGraph, starlarkSemantics);
     ImmutableTable<ModuleExtensionId, ModuleKey, ModuleExtensionUsage> extensionUsagesById;
     try {
       extensionUsagesById = getExtensionUsagesById(depGraph, canonicalRepoNameLookup.inverse());
@@ -73,14 +77,17 @@
     }
 
     ImmutableBiMap<String, ModuleExtensionId> extensionUniqueNames =
-        calculateUniqueNameForUsedExtensionId(extensionUsagesById);
+        calculateUniqueNameForUsedExtensionId(extensionUsagesById, starlarkSemantics);
 
     return BazelDepGraphValue.create(
         depGraph,
         canonicalRepoNameLookup,
         depGraph.values().stream().map(AbridgedModule::from).collect(toImmutableList()),
         extensionUsagesById,
-        extensionUniqueNames.inverse());
+        extensionUniqueNames.inverse(),
+        starlarkSemantics.getBool(BuildLanguageOptions.INCOMPATIBLE_USE_PLUS_IN_REPO_NAMES)
+            ? '+'
+            : '~');
   }
 
   private static ImmutableTable<ModuleExtensionId, ModuleKey, ModuleExtensionUsage>
@@ -126,7 +133,7 @@
   }
 
   private static ImmutableBiMap<RepositoryName, ModuleKey> computeCanonicalRepoNameLookup(
-      ImmutableMap<ModuleKey, Module> depGraph) {
+      ImmutableMap<ModuleKey, Module> depGraph, StarlarkSemantics semantics) {
     // Find modules with multiple versions in the dep graph. Currently, the only source of such
     // modules is multiple_version_override.
     ImmutableSet<String> multipleVersionsModules =
@@ -151,13 +158,14 @@
             toImmutableBiMap(
                 key ->
                     multipleVersionsModules.contains(key.getName())
-                        ? key.getCanonicalRepoNameWithVersion()
-                        : key.getCanonicalRepoNameWithoutVersion(),
+                        ? key.getCanonicalRepoNameWithVersion(semantics)
+                        : key.getCanonicalRepoNameWithoutVersion(semantics),
                 key -> key));
   }
 
   private ImmutableBiMap<String, ModuleExtensionId> calculateUniqueNameForUsedExtensionId(
-      ImmutableTable<ModuleExtensionId, ModuleKey, ModuleExtensionUsage> extensionUsagesById) {
+      ImmutableTable<ModuleExtensionId, ModuleKey, ModuleExtensionUsage> extensionUsagesById,
+      StarlarkSemantics starlarkSemantics) {
     // Calculate a unique name for each used extension id with the following property that is
     // required for BzlmodRepoRuleFunction to unambiguously identify the extension that generates a
     // given repo:
@@ -166,18 +174,23 @@
     BiMap<String, ModuleExtensionId> extensionUniqueNames = HashBiMap.create();
     for (ModuleExtensionId id : extensionUsagesById.rowKeySet()) {
       int attempt = 1;
-      while (extensionUniqueNames.putIfAbsent(makeUniqueNameCandidate(id, attempt), id) != null) {
+      while (extensionUniqueNames.putIfAbsent(
+              makeUniqueNameCandidate(id, attempt, starlarkSemantics), id)
+          != null) {
         attempt++;
       }
     }
     return ImmutableBiMap.copyOf(extensionUniqueNames);
   }
 
-  private static String makeUniqueNameCandidate(ModuleExtensionId id, int attempt) {
+  private static String makeUniqueNameCandidate(
+      ModuleExtensionId id, int attempt, StarlarkSemantics starlarkSemantics) {
+    boolean usePlus =
+        starlarkSemantics.getBool(BuildLanguageOptions.INCOMPATIBLE_USE_PLUS_IN_REPO_NAMES);
     // Ensure that the resulting extension name (and thus the repository names derived from it) do
     // not start with a tilde.
     RepositoryName repository = id.getBzlFileLabel().getRepository();
-    String nonEmptyRepoPart = repository.isMain() ? "_main" : repository.getName();
+    String nonEmptyRepoPart = repository.isMain() && !usePlus ? "_main" : repository.getName();
     // When using a namespace, prefix the extension name with "_" to distinguish the prefix from
     // those generated by non-namespaced extension usages. Extension names are identified by their
     // Starlark identifier, which in the case of an exported symbol cannot start with "_".
@@ -191,14 +204,18 @@
         .map(
             namespace ->
                 String.format(
-                    "%s~_%s%s~%s~%s~%s",
+                    usePlus ? "%s+_%s%s+%s+%s+%s" : "%s~_%s%s~%s~%s~%s",
                     nonEmptyRepoPart,
                     id.getExtensionName(),
                     extensionNameDisambiguator,
                     namespace.getModule().getName(),
                     namespace.getModule().getVersion(),
                     namespace.getUsageExportedName()))
-        .orElse(nonEmptyRepoPart + "~" + id.getExtensionName() + extensionNameDisambiguator);
+        .orElse(
+            nonEmptyRepoPart
+                + (usePlus ? "+" : "~")
+                + id.getExtensionName()
+                + extensionNameDisambiguator);
   }
 
   static class BazelDepGraphFunctionException extends SkyFunctionException {
diff --git a/src/main/java/com/google/devtools/build/lib/bazel/bzlmod/BazelDepGraphValue.java b/src/main/java/com/google/devtools/build/lib/bazel/bzlmod/BazelDepGraphValue.java
index 6fb4c98..8621775 100644
--- a/src/main/java/com/google/devtools/build/lib/bazel/bzlmod/BazelDepGraphValue.java
+++ b/src/main/java/com/google/devtools/build/lib/bazel/bzlmod/BazelDepGraphValue.java
@@ -15,7 +15,6 @@
 
 package com.google.devtools.build.lib.bazel.bzlmod;
 
-import static com.google.common.collect.ImmutableMap.toImmutableMap;
 
 import com.google.auto.value.AutoValue;
 import com.google.common.collect.ImmutableBiMap;
@@ -43,13 +42,15 @@
       ImmutableMap<RepositoryName, ModuleKey> canonicalRepoNameLookup,
       ImmutableList<AbridgedModule> abridgedModules,
       ImmutableTable<ModuleExtensionId, ModuleKey, ModuleExtensionUsage> extensionUsagesTable,
-      ImmutableMap<ModuleExtensionId, String> extensionUniqueNames) {
+      ImmutableMap<ModuleExtensionId, String> extensionUniqueNames,
+      char repoNameSeparator) {
     return new AutoValue_BazelDepGraphValue(
         depGraph,
         ImmutableBiMap.copyOf(canonicalRepoNameLookup),
         abridgedModules,
         extensionUsagesTable,
-        extensionUniqueNames);
+        extensionUniqueNames,
+        repoNameSeparator);
   }
 
   public static BazelDepGraphValue createEmptyDepGraph() {
@@ -65,22 +66,16 @@
             .build();
 
     ImmutableMap<ModuleKey, Module> emptyDepGraph = ImmutableMap.of(ModuleKey.ROOT, root);
-
     ImmutableMap<RepositoryName, ModuleKey> canonicalRepoNameLookup =
-        emptyDepGraph.keySet().stream()
-            .collect(
-                toImmutableMap(
-                    // All modules in the empty dep graph (just the root module) have an empty
-                    // version, so the choice of including it in the canonical repo name does not
-                    // matter.
-                    ModuleKey::getCanonicalRepoNameWithoutVersion, key -> key));
+        ImmutableMap.of(RepositoryName.MAIN, ModuleKey.ROOT);
 
     return BazelDepGraphValue.create(
         emptyDepGraph,
         canonicalRepoNameLookup,
         ImmutableList.of(),
         ImmutableTable.of(),
-        ImmutableMap.of());
+        ImmutableMap.of(),
+        '+');
   }
 
   /**
@@ -112,6 +107,9 @@
    */
   public abstract ImmutableMap<ModuleExtensionId, String> getExtensionUniqueNames();
 
+  /** The character to use to separate the different segments of a canonical repo name. */
+  public abstract char getRepoNameSeparator();
+
   /**
    * Returns the full {@link RepositoryMapping} for the given module, including repos from Bazel
    * module deps and module extensions.
@@ -122,7 +120,7 @@
         getExtensionUsagesTable().column(key).entrySet()) {
       ModuleExtensionId extensionId = extIdAndUsage.getKey();
       ModuleExtensionUsage usage = extIdAndUsage.getValue();
-      String repoNamePrefix = getExtensionUniqueNames().get(extensionId) + "~";
+      String repoNamePrefix = getExtensionUniqueNames().get(extensionId) + getRepoNameSeparator();
       for (ModuleExtensionUsage.Proxy proxy : usage.getProxies()) {
         for (Map.Entry<String, String> entry : proxy.getImports().entrySet()) {
           String canonicalRepoName = repoNamePrefix + entry.getValue();
diff --git a/src/main/java/com/google/devtools/build/lib/bazel/bzlmod/BazelLockFileModule.java b/src/main/java/com/google/devtools/build/lib/bazel/bzlmod/BazelLockFileModule.java
index afb6f3a..b615a6d 100644
--- a/src/main/java/com/google/devtools/build/lib/bazel/bzlmod/BazelLockFileModule.java
+++ b/src/main/java/com/google/devtools/build/lib/bazel/bzlmod/BazelLockFileModule.java
@@ -117,6 +117,18 @@
     // lockfile that are still up-to-date and adding the newly resolved extension results.
     BazelLockFileValue newLockfile =
         BazelLockFileValue.builder()
+            // HACK: Flipping the flag `--incompatible_use_plus_in_repo_names` causes the canonical
+            // repo name format to change, which warrants a lockfile invalidation. We could do this
+            // properly by introducing another field in the lockfile, but that's very annoying since
+            // we'll need to 1) keep it around for a while; 2) be careful not to parse the rest of
+            // the lockfile to avoid triggering parsing errors ('~' will be an invalid character in
+            // repo names eventually). So we just increment the lockfile version if '+' is being
+            // used. This does mean that, while this hack exists, normal increments of the lockfile
+            // version need to be done by 2 at a time (i.e. keep LOCK_FILE_VERSION an odd number).
+            .setLockFileVersion(
+                depGraphValue.getRepoNameSeparator() == '+'
+                    ? BazelLockFileValue.LOCK_FILE_VERSION + 1
+                    : BazelLockFileValue.LOCK_FILE_VERSION)
             .setRegistryFileHashes(
                 ImmutableSortedMap.copyOf(moduleResolutionValue.getRegistryFileHashes()))
             .setSelectedYankedVersions(moduleResolutionValue.getSelectedYankedVersions())
diff --git a/src/main/java/com/google/devtools/build/lib/bazel/bzlmod/BazelLockFileValue.java b/src/main/java/com/google/devtools/build/lib/bazel/bzlmod/BazelLockFileValue.java
index 60b6faf..ff94e4c 100644
--- a/src/main/java/com/google/devtools/build/lib/bazel/bzlmod/BazelLockFileValue.java
+++ b/src/main/java/com/google/devtools/build/lib/bazel/bzlmod/BazelLockFileValue.java
@@ -35,6 +35,8 @@
 @GenerateTypeAdapter
 public abstract class BazelLockFileValue implements SkyValue, Postable {
 
+  // NOTE: See "HACK" note in BazelLockFileModule. While this hack exists, normal increments of the
+  // lockfile version need to be done by 2 at a time (i.e. keep LOCK_FILE_VERSION an odd number).
   public static final int LOCK_FILE_VERSION = 11;
 
   @SerializationConstant public static final SkyKey KEY = () -> SkyFunctions.BAZEL_LOCK_FILE;
diff --git a/src/main/java/com/google/devtools/build/lib/bazel/bzlmod/ModuleExtensionId.java b/src/main/java/com/google/devtools/build/lib/bazel/bzlmod/ModuleExtensionId.java
index 3fb6eeb..e0b135a 100644
--- a/src/main/java/com/google/devtools/build/lib/bazel/bzlmod/ModuleExtensionId.java
+++ b/src/main/java/com/google/devtools/build/lib/bazel/bzlmod/ModuleExtensionId.java
@@ -60,6 +60,8 @@
 
     @Override
     public final String toString() {
+      // NOTE: Can't be bothered to switch this based on the flag. But DO change this to "+" by
+      // Bazel 8!
       return getModule() + "~" + getUsageExportedName();
     }
 
diff --git a/src/main/java/com/google/devtools/build/lib/bazel/bzlmod/ModuleFileFunction.java b/src/main/java/com/google/devtools/build/lib/bazel/bzlmod/ModuleFileFunction.java
index fd04204..8ba416e 100644
--- a/src/main/java/com/google/devtools/build/lib/bazel/bzlmod/ModuleFileFunction.java
+++ b/src/main/java/com/google/devtools/build/lib/bazel/bzlmod/ModuleFileFunction.java
@@ -156,7 +156,8 @@
     GetModuleFileResult getModuleFileResult;
     try (SilentCloseable c =
         Profiler.instance().profile(ProfilerTask.BZLMOD, () -> "fetch module file: " + moduleKey)) {
-      getModuleFileResult = getModuleFile(moduleKey, moduleFileKey.getOverride(), env);
+      getModuleFileResult =
+          getModuleFile(moduleKey, moduleFileKey.getOverride(), starlarkSemantics, env);
     }
     if (getModuleFileResult == null) {
       return null;
@@ -475,7 +476,8 @@
                     // A module with a non-registry override always has a unique version across the
                     // entire dep graph.
                     name ->
-                        ModuleKey.create(name, Version.EMPTY).getCanonicalRepoNameWithoutVersion(),
+                        ModuleKey.create(name, Version.EMPTY)
+                            .getCanonicalRepoNameWithoutVersion(starlarkSemantics),
                     name -> name));
     ImmutableSet<PathFragment> moduleFilePaths =
         Stream.concat(
@@ -544,14 +546,17 @@
 
   @Nullable
   private GetModuleFileResult getModuleFile(
-      ModuleKey key, @Nullable ModuleOverride override, Environment env)
+      ModuleKey key,
+      @Nullable ModuleOverride override,
+      StarlarkSemantics starlarkSemantics,
+      Environment env)
       throws ModuleFileFunctionException, InterruptedException {
     // If there is a non-registry override for this module, we need to fetch the corresponding repo
     // first and read the module file from there.
     if (override instanceof NonRegistryOverride) {
       // A module with a non-registry override always has a unique version across the entire dep
       // graph.
-      RepositoryName canonicalRepoName = key.getCanonicalRepoNameWithoutVersion();
+      RepositoryName canonicalRepoName = key.getCanonicalRepoNameWithoutVersion(starlarkSemantics);
       RepositoryDirectoryValue repoDir =
           (RepositoryDirectoryValue) env.getValue(RepositoryDirectoryValue.key(canonicalRepoName));
       if (repoDir == null) {
diff --git a/src/main/java/com/google/devtools/build/lib/bazel/bzlmod/ModuleKey.java b/src/main/java/com/google/devtools/build/lib/bazel/bzlmod/ModuleKey.java
index 6fb5e0a..c0ad725 100644
--- a/src/main/java/com/google/devtools/build/lib/bazel/bzlmod/ModuleKey.java
+++ b/src/main/java/com/google/devtools/build/lib/bazel/bzlmod/ModuleKey.java
@@ -16,12 +16,15 @@
 package com.google.devtools.build.lib.bazel.bzlmod;
 
 import com.google.auto.value.AutoValue;
+import com.google.common.annotations.VisibleForTesting;
 import com.google.common.base.Preconditions;
 import com.google.common.base.Splitter;
 import com.google.common.collect.ImmutableMap;
 import com.google.devtools.build.lib.cmdline.RepositoryName;
+import com.google.devtools.build.lib.packages.semantics.BuildLanguageOptions;
 import java.util.Comparator;
 import java.util.List;
+import net.starlark.java.eval.StarlarkSemantics;
 
 /** A module name, version pair that identifies a module in the external dependency graph. */
 @AutoValue
@@ -79,8 +82,13 @@
    *
    * <p>This method must not be called if the module has a {@link NonRegistryOverride}.
    */
-  public RepositoryName getCanonicalRepoNameWithVersion() {
-    return getCanonicalRepoName(/* includeVersion= */ true);
+  public RepositoryName getCanonicalRepoNameWithVersion(StarlarkSemantics semantics) {
+    return getCanonicalRepoName(/* includeVersion= */ true, semantics);
+  }
+
+  @VisibleForTesting
+  public RepositoryName getCanonicalRepoNameWithVersionForTesting() {
+    return getCanonicalRepoNameWithVersion(StarlarkSemantics.DEFAULT);
   }
 
   /**
@@ -88,26 +96,32 @@
    * only guaranteed to be unique when there is a single version of the module in the entire dep
    * graph.
    */
-  public RepositoryName getCanonicalRepoNameWithoutVersion() {
-    return getCanonicalRepoName(/* includeVersion= */ false);
+  public RepositoryName getCanonicalRepoNameWithoutVersion(StarlarkSemantics semantics) {
+    return getCanonicalRepoName(/* includeVersion= */ false, semantics);
   }
 
-  private RepositoryName getCanonicalRepoName(boolean includeVersion) {
+  @VisibleForTesting
+  public RepositoryName getCanonicalRepoNameWithoutVersionForTesting() {
+    return getCanonicalRepoNameWithoutVersion(StarlarkSemantics.DEFAULT);
+  }
+
+  private RepositoryName getCanonicalRepoName(boolean includeVersion, StarlarkSemantics semantics) {
     if (WELL_KNOWN_MODULES.containsKey(getName())) {
       return WELL_KNOWN_MODULES.get(getName());
     }
     if (ROOT.equals(this)) {
       return RepositoryName.MAIN;
     }
+    boolean usePlus = semantics.getBool(BuildLanguageOptions.INCOMPATIBLE_USE_PLUS_IN_REPO_NAMES);
     String suffix;
     if (includeVersion) {
       // getVersion().isEmpty() is true only for modules with non-registry overrides, which enforce
       // that there is a single version of the module in the dep graph.
       Preconditions.checkState(!getVersion().isEmpty());
-      // Prepend "v" to prevent canonical repo names, which form segments of file paths, from
-      // looking like a Windows short path. Such paths segments would incur additional file IO
-      // during analysis (see WindowsShortPath).
-      suffix = "v" + getVersion().toString();
+      // When using `~` as the separator, prepend "v" to prevent canonical repo names, which form
+      // segments of file paths, from looking like a Windows short path. Such paths segments would
+      // incur additional file IO during analysis (see WindowsShortPath).
+      suffix = usePlus ? getVersion().toString() : "v" + getVersion().toString();
     } else {
       // This results in canonical repository names such as `rules_foo~` for the module `rules_foo`.
       // This particular format is chosen since:
@@ -125,7 +139,8 @@
       //   rarely used.
       suffix = "";
     }
-    return RepositoryName.createUnvalidated(String.format("%s~%s", getName(), suffix));
+    return RepositoryName.createUnvalidated(
+        String.format("%s%c%s", getName(), usePlus ? '+' : '~', suffix));
   }
 
   public static ModuleKey fromString(String s) throws Version.ParseException {
diff --git a/src/main/java/com/google/devtools/build/lib/bazel/bzlmod/SingleExtensionEvalFunction.java b/src/main/java/com/google/devtools/build/lib/bazel/bzlmod/SingleExtensionEvalFunction.java
index b1ca65d..e452dda 100644
--- a/src/main/java/com/google/devtools/build/lib/bazel/bzlmod/SingleExtensionEvalFunction.java
+++ b/src/main/java/com/google/devtools/build/lib/bazel/bzlmod/SingleExtensionEvalFunction.java
@@ -47,6 +47,7 @@
 import com.google.devtools.build.lib.packages.NoSuchPackageException;
 import com.google.devtools.build.lib.packages.Rule;
 import com.google.devtools.build.lib.packages.RuleFactory.InvalidRuleException;
+import com.google.devtools.build.lib.packages.semantics.BuildLanguageOptions;
 import com.google.devtools.build.lib.profiler.Profiler;
 import com.google.devtools.build.lib.profiler.ProfilerTask;
 import com.google.devtools.build.lib.profiler.SilentCloseable;
@@ -178,6 +179,7 @@
                   extension,
                   usagesValue,
                   extension.getEvalFactors(),
+                  starlarkSemantics,
                   lockedExtension);
           if (singleExtensionValue != null) {
             return singleExtensionValue;
@@ -261,7 +263,13 @@
       lockFileInfo = Optional.empty();
     }
     return createSingleExtensionValue(
-        generatedRepoSpecs, moduleExtensionMetadata, extensionId, usagesValue, lockFileInfo, env);
+        generatedRepoSpecs,
+        moduleExtensionMetadata,
+        extensionId,
+        usagesValue,
+        lockFileInfo,
+        starlarkSemantics,
+        env);
   }
 
   /**
@@ -278,6 +286,7 @@
       RunnableExtension extension,
       SingleExtensionUsagesValue usagesValue,
       ModuleExtensionEvalFactors evalFactors,
+      StarlarkSemantics starlarkSemantics,
       LockFileModuleExtension lockedExtension)
       throws SingleExtensionEvalFunctionException,
           InterruptedException,
@@ -338,6 +347,7 @@
           extensionId,
           usagesValue,
           Optional.of(new LockFileModuleExtension.WithFactors(evalFactors, lockedExtension)),
+          starlarkSemantics,
           env);
     }
     if (lockfileMode.equals(LockfileMode.ERROR)) {
@@ -452,6 +462,7 @@
       ModuleExtensionId extensionId,
       SingleExtensionUsagesValue usagesValue,
       Optional<LockFileModuleExtension.WithFactors> lockFileInfo,
+      StarlarkSemantics starlarkSemantics,
       Environment env)
       throws SingleExtensionEvalFunctionException {
     Optional<RootModuleFileFixup> fixup = Optional.empty();
@@ -479,6 +490,11 @@
       }
     }
 
+    char separator =
+        starlarkSemantics.getBool(BuildLanguageOptions.INCOMPATIBLE_USE_PLUS_IN_REPO_NAMES)
+            ? '+'
+            : '~';
+
     return SingleExtensionValue.create(
         generatedRepoSpecs,
         generatedRepoSpecs.keySet().stream()
@@ -486,7 +502,7 @@
                 toImmutableBiMap(
                     e ->
                         RepositoryName.createUnvalidated(
-                            usagesValue.getExtensionUniqueName() + "~" + e),
+                            usagesValue.getExtensionUniqueName() + separator + e),
                     Function.identity())),
         lockFileInfo,
         fixup);
@@ -744,7 +760,11 @@
         Dict<String, Object> kwargs = repo.tag().getAttributeValues().attributes();
         // This cast should be safe since it should have been verified at tag creation time.
         String name = (String) kwargs.get("name");
-        String prefixedName = usagesValue.getExtensionUniqueName() + "~" + name;
+        char separator =
+            starlarkSemantics.getBool(BuildLanguageOptions.INCOMPATIBLE_USE_PLUS_IN_REPO_NAMES)
+                ? '+'
+                : '~';
+        String prefixedName = usagesValue.getExtensionUniqueName() + separator + name;
         Rule ruleInstance;
         AttributeValues attributesValue;
         try {
@@ -884,9 +904,13 @@
         ModuleExtensionId extensionId,
         RepositoryMapping mainRepositoryMapping)
         throws InterruptedException, SingleExtensionEvalFunctionException {
+      char separator =
+          starlarkSemantics.getBool(BuildLanguageOptions.INCOMPATIBLE_USE_PLUS_IN_REPO_NAMES)
+              ? '+'
+              : '~';
       ModuleExtensionEvalStarlarkThreadContext threadContext =
           new ModuleExtensionEvalStarlarkThreadContext(
-              usagesValue.getExtensionUniqueName() + "~",
+              usagesValue.getExtensionUniqueName() + separator,
               extensionId.getBzlFileLabel().getPackageIdentifier(),
               BazelModuleContext.of(bzlLoadValue.getModule()).repoMapping(),
               directories,
diff --git a/src/main/java/com/google/devtools/build/lib/bazel/bzlmod/StarlarkBazelModule.java b/src/main/java/com/google/devtools/build/lib/bazel/bzlmod/StarlarkBazelModule.java
index 90b28b8..f15f7d4 100644
--- a/src/main/java/com/google/devtools/build/lib/bazel/bzlmod/StarlarkBazelModule.java
+++ b/src/main/java/com/google/devtools/build/lib/bazel/bzlmod/StarlarkBazelModule.java
@@ -139,7 +139,7 @@
     }
     return new StarlarkBazelModule(
         module.getName(),
-        module.getVersion().getOriginal(),
+        module.getVersion().getNormalized(),
         new Tags(Maps.transformValues(typeCheckedTags, StarlarkList::immutableCopyOf)),
         module.getKey().equals(ModuleKey.ROOT));
   }
diff --git a/src/main/java/com/google/devtools/build/lib/bazel/bzlmod/Version.java b/src/main/java/com/google/devtools/build/lib/bazel/bzlmod/Version.java
index 41072e0..42d4402 100644
--- a/src/main/java/com/google/devtools/build/lib/bazel/bzlmod/Version.java
+++ b/src/main/java/com/google/devtools/build/lib/bazel/bzlmod/Version.java
@@ -36,9 +36,9 @@
  * each a sequence of "identifiers" (defined as a non-empty sequence of ASCII alphanumerical
  * characters and hyphens) separated by dots. The {@code RELEASE} part may not contain hyphens.
  *
- * <p>Otherwise, this format is identical to SemVer, especially in terms of the comparison algorithm
- * (https://semver.org/#spec-item-11). In other words, this format is intentionally looser than
- * SemVer; in particular:
+ * <p>Otherwise, this format is identical to SemVer, especially in terms of the <a
+ * href="https://semver.org/#spec-item-11">comparison algorithm</a>. In other words, this format is
+ * intentionally looser than SemVer; in particular:
  *
  * <ul>
  *   <li>the "release" part isn't limited to exactly 3 segments (major, minor, patch), but can be
@@ -51,6 +51,13 @@
  * {@code a} and {@code b} compare {@code a < b} iff the same holds when they're compared as Bazel
  * module versions.
  *
+ * <p>Versions with a "build" part are generally accepted as input, but they're treated as if the
+ * "build" part is completely absent. That is, when Bazel outputs version strings, it never outputs
+ * the "build" part (in fact, it doesn't even store it); similarly, when Bazel accesses registries
+ * to request versions, the "build" part is never included. This gives us the nice property of
+ * "consistent with equals" natural ordering (see {@link Comparable}); that is, {@code
+ * a.compareTo(b) == 0} iff {@code a.equals(b)}.
+ *
  * <p>The special "empty string" version can also be used, and compares higher than everything else.
  * It signifies that there is a {@link NonRegistryOverride} for a module.
  */
@@ -112,15 +119,15 @@
   /** Returns the "prerelease" part of the version string as a list of {@link Identifier}s. */
   abstract ImmutableList<Identifier> getPrerelease();
 
-  /** Returns the original version string. */
-  public abstract String getOriginal();
+  /** Returns the normalized version string (that is, with any "build" part stripped). */
+  public abstract String getNormalized();
 
   /**
    * Whether this is just the "empty string" version, which signifies a non-registry override for
    * the module.
    */
   boolean isEmpty() {
-    return getOriginal().isEmpty();
+    return getNormalized().isEmpty();
   }
 
   /**
@@ -164,7 +171,8 @@
       }
     }
 
-    return new AutoValue_Version(releaseSplit.build(), prereleaseSplit.build(), version);
+    String normalized = Strings.isNullOrEmpty(prerelease) ? release : release + '-' + prerelease;
+    return new AutoValue_Version(releaseSplit.build(), prereleaseSplit.build(), normalized);
   }
 
   private static final Comparator<Version> COMPARATOR =
@@ -180,17 +188,18 @@
 
   @Override
   public final String toString() {
-    return getOriginal();
+    return getNormalized();
   }
 
   @Override
   public final boolean equals(Object o) {
-    return this == o || (o instanceof Version && ((Version) o).getOriginal().equals(getOriginal()));
+    return this == o
+        || (o instanceof Version && ((Version) o).getNormalized().equals(getNormalized()));
   }
 
   @Override
   public final int hashCode() {
-    return Objects.hash("version", getOriginal().hashCode());
+    return Objects.hash("version", getNormalized().hashCode());
   }
 
   /** An exception encountered while trying to {@link Version#parse parse} a version. */
diff --git a/src/main/java/com/google/devtools/build/lib/cmdline/RepositoryName.java b/src/main/java/com/google/devtools/build/lib/cmdline/RepositoryName.java
index 5a386b3..ab1bf0d 100644
--- a/src/main/java/com/google/devtools/build/lib/cmdline/RepositoryName.java
+++ b/src/main/java/com/google/devtools/build/lib/cmdline/RepositoryName.java
@@ -42,7 +42,7 @@
   // Repository names must not start with a tilde as shells treat unescaped paths starting with them
   // specially.
   // https://www.gnu.org/software/bash/manual/html_node/Tilde-Expansion.html
-  private static final Pattern VALID_REPO_NAME = Pattern.compile("|[\\w\\-.][\\w\\-.~]*");
+  private static final Pattern VALID_REPO_NAME = Pattern.compile("|[\\w\\-.+][\\w\\-.~+]*");
 
   // Must start with a letter. Can contain ASCII letters and digits, underscore, dash, and dot.
   private static final Pattern VALID_USER_PROVIDED_NAME = Pattern.compile("[a-zA-Z][-.\\w]*$");
@@ -218,11 +218,12 @@
     if (ownerRepoIfNotVisible.isMain()) {
       return "root module";
     } else {
+      boolean hasTilde = ownerRepoIfNotVisible.getName().contains("~");
       return String.format(
           "module '%s'",
           ownerRepoIfNotVisible
               .getName()
-              .substring(0, ownerRepoIfNotVisible.getName().indexOf('~')));
+              .substring(0, ownerRepoIfNotVisible.getName().indexOf(hasTilde ? '~' : '+')));
     }
   }
 
diff --git a/src/main/java/com/google/devtools/build/lib/packages/semantics/BuildLanguageOptions.java b/src/main/java/com/google/devtools/build/lib/packages/semantics/BuildLanguageOptions.java
index 9575a92..3df4f24 100644
--- a/src/main/java/com/google/devtools/build/lib/packages/semantics/BuildLanguageOptions.java
+++ b/src/main/java/com/google/devtools/build/lib/packages/semantics/BuildLanguageOptions.java
@@ -216,6 +216,17 @@
   public boolean enableWorkspace;
 
   @Option(
+      name = "incompatible_use_plus_in_repo_names",
+      defaultValue = "false",
+      documentationCategory = OptionDocumentationCategory.STARLARK_SEMANTICS,
+      effectTags = OptionEffectTag.LOADING_AND_ANALYSIS,
+      help =
+          "If true, uses the plus sign (+) as the separator in canonical repo names, instead of the"
+              + " tilde (~). This is to address severe performance issues on Windows; see"
+              + " https://github.com/bazelbuild/bazel/issues/22865 for more information.")
+  public boolean incompatibleUsePlusInRepoNames;
+
+  @Option(
       name = "experimental_isolated_extension_usages",
       defaultValue = "false",
       documentationCategory = OptionDocumentationCategory.STARLARK_SEMANTICS,
@@ -760,6 +771,7 @@
             .setBool(EXPERIMENTAL_ENABLE_SCL_DIALECT, experimentalEnableSclDialect)
             .setBool(ENABLE_BZLMOD, enableBzlmod)
             .setBool(ENABLE_WORKSPACE, enableWorkspace)
+            .setBool(INCOMPATIBLE_USE_PLUS_IN_REPO_NAMES, incompatibleUsePlusInRepoNames)
             .setBool(EXPERIMENTAL_ISOLATED_EXTENSION_USAGES, experimentalIsolatedExtensionUsages)
             .setBool(
                 INCOMPATIBLE_EXISTING_RULES_IMMUTABLE_VIEW, incompatibleExistingRulesImmutableView)
@@ -869,6 +881,8 @@
   public static final String EXPERIMENTAL_ENABLE_SCL_DIALECT = "-experimental_enable_scl_dialect";
   public static final String ENABLE_BZLMOD = "+enable_bzlmod";
   public static final String ENABLE_WORKSPACE = "+enable_workspace";
+  public static final String INCOMPATIBLE_USE_PLUS_IN_REPO_NAMES =
+      "-incompatible_use_plus_in_repo_names";
   public static final String EXPERIMENTAL_ISOLATED_EXTENSION_USAGES =
       "-experimental_isolated_extension_usages";
   public static final String INCOMPATIBLE_EXISTING_RULES_IMMUTABLE_VIEW =
diff --git a/src/main/java/com/google/devtools/build/lib/skyframe/BzlmodRepoRuleFunction.java b/src/main/java/com/google/devtools/build/lib/skyframe/BzlmodRepoRuleFunction.java
index 55e4135..3e30cb1 100644
--- a/src/main/java/com/google/devtools/build/lib/skyframe/BzlmodRepoRuleFunction.java
+++ b/src/main/java/com/google/devtools/build/lib/skyframe/BzlmodRepoRuleFunction.java
@@ -39,6 +39,7 @@
 import com.google.devtools.build.lib.packages.RuleClassProvider;
 import com.google.devtools.build.lib.packages.RuleFactory.InvalidRuleException;
 import com.google.devtools.build.lib.packages.RuleFunction;
+import com.google.devtools.build.lib.packages.semantics.BuildLanguageOptions;
 import com.google.devtools.build.lib.server.FailureDetails.PackageLoading;
 import com.google.devtools.build.lib.util.Pair;
 import com.google.devtools.build.skyframe.SkyFunction;
@@ -113,9 +114,13 @@
     }
 
     // Step 3: look for the repo from module extension evaluation results.
+    char separator =
+        starlarkSemantics.getBool(BuildLanguageOptions.INCOMPATIBLE_USE_PLUS_IN_REPO_NAMES)
+            ? '+'
+            : '~';
     Optional<ModuleExtensionId> extensionId =
         bazelDepGraphValue.getExtensionUniqueNames().entrySet().stream()
-            .filter(e -> repositoryName.getName().startsWith(e.getValue() + "~"))
+            .filter(e -> repositoryName.getName().startsWith(e.getValue() + separator))
             .map(Entry::getKey)
             .findFirst();
 
diff --git a/src/main/java/com/google/devtools/build/lib/skyframe/RepositoryMappingFunction.java b/src/main/java/com/google/devtools/build/lib/skyframe/RepositoryMappingFunction.java
index d01fd4d..2cfd331 100644
--- a/src/main/java/com/google/devtools/build/lib/skyframe/RepositoryMappingFunction.java
+++ b/src/main/java/com/google/devtools/build/lib/skyframe/RepositoryMappingFunction.java
@@ -233,7 +233,11 @@
   private static Optional<ModuleExtensionId> maybeGetModuleExtensionForRepo(
       RepositoryName repositoryName, BazelDepGraphValue bazelDepGraphValue) {
     return bazelDepGraphValue.getExtensionUniqueNames().entrySet().stream()
-        .filter(e -> repositoryName.getName().startsWith(e.getValue() + "~"))
+        .filter(
+            e ->
+                repositoryName
+                    .getName()
+                    .startsWith(e.getValue() + bazelDepGraphValue.getRepoNameSeparator()))
         .map(Entry::getKey)
         .findFirst();
   }
diff --git a/src/main/java/com/google/devtools/build/lib/skyframe/RepositoryMappingValue.java b/src/main/java/com/google/devtools/build/lib/skyframe/RepositoryMappingValue.java
index 54bfef2..d457372 100644
--- a/src/main/java/com/google/devtools/build/lib/skyframe/RepositoryMappingValue.java
+++ b/src/main/java/com/google/devtools/build/lib/skyframe/RepositoryMappingValue.java
@@ -72,7 +72,7 @@
     return new AutoValue_RepositoryMappingValue(
         repositoryMapping,
         Optional.of(associatedModuleName),
-        Optional.of(associatedModuleVersion.getOriginal()));
+        Optional.of(associatedModuleVersion.getNormalized()));
   }
 
   /**
diff --git a/src/test/java/com/google/devtools/build/lib/bazel/bzlmod/BzlmodTestUtil.java b/src/test/java/com/google/devtools/build/lib/bazel/bzlmod/BzlmodTestUtil.java
index d27f684..6783f21 100644
--- a/src/test/java/com/google/devtools/build/lib/bazel/bzlmod/BzlmodTestUtil.java
+++ b/src/test/java/com/google/devtools/build/lib/bazel/bzlmod/BzlmodTestUtil.java
@@ -307,7 +307,7 @@
       mappingBuilder.put(names[i], RepositoryName.createUnvalidated(names[i + 1]));
     }
     return RepositoryMapping.create(
-        mappingBuilder.buildOrThrow(), key.getCanonicalRepoNameWithoutVersion());
+        mappingBuilder.buildOrThrow(), key.getCanonicalRepoNameWithoutVersionForTesting());
   }
 
   public static TagClass createTagClass(Attribute... attrs) {
diff --git a/src/test/java/com/google/devtools/build/lib/bazel/bzlmod/FakeRegistry.java b/src/test/java/com/google/devtools/build/lib/bazel/bzlmod/FakeRegistry.java
index d1d20ae..1f8ba8e 100644
--- a/src/test/java/com/google/devtools/build/lib/bazel/bzlmod/FakeRegistry.java
+++ b/src/test/java/com/google/devtools/build/lib/bazel/bzlmod/FakeRegistry.java
@@ -81,7 +81,10 @@
             .setAttributes(
                 AttributeValues.create(
                     ImmutableMap.of(
-                        "path", rootPath + "/" + key.getCanonicalRepoNameWithVersion().getName())))
+                        "path",
+                        rootPath
+                            + "/"
+                            + key.getCanonicalRepoNameWithVersionForTesting().getName())))
             .build();
     eventHandler.post(
         RegistryFileDownloadEvent.create(
diff --git a/src/test/java/com/google/devtools/build/lib/bazel/bzlmod/InterimModuleTest.java b/src/test/java/com/google/devtools/build/lib/bazel/bzlmod/InterimModuleTest.java
index dd65628..d903da3 100644
--- a/src/test/java/com/google/devtools/build/lib/bazel/bzlmod/InterimModuleTest.java
+++ b/src/test/java/com/google/devtools/build/lib/bazel/bzlmod/InterimModuleTest.java
@@ -39,7 +39,7 @@
                         DepSpec.fromModuleKey(
                             createModuleKey(
                                 depSpec.getName() + "_new",
-                                depSpec.getVersion().getOriginal() + ".1"))))
+                                depSpec.getVersion().getNormalized() + ".1"))))
         .isEqualTo(
             InterimModuleBuilder.create("", "")
                 .addDep("dep_foo", createModuleKey("foo_new", "1.0.1"))
diff --git a/src/test/java/com/google/devtools/build/lib/bazel/bzlmod/ModuleTest.java b/src/test/java/com/google/devtools/build/lib/bazel/bzlmod/ModuleTest.java
index d7f3041..dd4db83 100644
--- a/src/test/java/com/google/devtools/build/lib/bazel/bzlmod/ModuleTest.java
+++ b/src/test/java/com/google/devtools/build/lib/bazel/bzlmod/ModuleTest.java
@@ -46,7 +46,8 @@
             module.getRepoMappingWithBazelDepsOnly(
                 Stream.of(key, fooKey, barKey, ModuleKey.ROOT)
                     .collect(
-                        toImmutableMap(k -> k, ModuleKey::getCanonicalRepoNameWithoutVersion))))
+                        toImmutableMap(
+                            k -> k, ModuleKey::getCanonicalRepoNameWithoutVersionForTesting))))
         .isEqualTo(
             createRepositoryMapping(
                 key,
@@ -73,7 +74,9 @@
     assertThat(
             module.getRepoMappingWithBazelDepsOnly(
                 Stream.of(ModuleKey.ROOT, fooKey, barKey)
-                    .collect(toImmutableMap(k -> k, ModuleKey::getCanonicalRepoNameWithVersion))))
+                    .collect(
+                        toImmutableMap(
+                            k -> k, ModuleKey::getCanonicalRepoNameWithVersionForTesting))))
         .isEqualTo(
             createRepositoryMapping(
                 ModuleKey.ROOT,
@@ -89,11 +92,14 @@
 
   @Test
   public void getCanonicalRepoName_isNotAWindowsShortPath() {
-    assertNotAShortPath(createModuleKey("foo", "").getCanonicalRepoNameWithoutVersion().getName());
-    assertNotAShortPath(createModuleKey("foo", "1").getCanonicalRepoNameWithVersion().getName());
-    assertNotAShortPath(createModuleKey("foo", "1.2").getCanonicalRepoNameWithVersion().getName());
     assertNotAShortPath(
-        createModuleKey("foo", "1.2.3").getCanonicalRepoNameWithVersion().getName());
+        createModuleKey("foo", "").getCanonicalRepoNameWithoutVersionForTesting().getName());
+    assertNotAShortPath(
+        createModuleKey("foo", "1").getCanonicalRepoNameWithVersionForTesting().getName());
+    assertNotAShortPath(
+        createModuleKey("foo", "1.2").getCanonicalRepoNameWithVersionForTesting().getName());
+    assertNotAShortPath(
+        createModuleKey("foo", "1.2.3").getCanonicalRepoNameWithVersionForTesting().getName());
   }
 
   private static void assertNotAShortPath(String name) {
diff --git a/src/test/java/com/google/devtools/build/lib/bazel/bzlmod/StarlarkBazelModuleTest.java b/src/test/java/com/google/devtools/build/lib/bazel/bzlmod/StarlarkBazelModuleTest.java
index 6fdb4f7..032488d 100644
--- a/src/test/java/com/google/devtools/build/lib/bazel/bzlmod/StarlarkBazelModuleTest.java
+++ b/src/test/java/com/google/devtools/build/lib/bazel/bzlmod/StarlarkBazelModuleTest.java
@@ -95,8 +95,8 @@
             extension,
             module.getRepoMappingWithBazelDepsOnly(
                 ImmutableMap.of(
-                    fooKey, fooKey.getCanonicalRepoNameWithoutVersion(),
-                    barKey, barKey.getCanonicalRepoNameWithoutVersion())),
+                    fooKey, fooKey.getCanonicalRepoNameWithoutVersionForTesting(),
+                    barKey, barKey.getCanonicalRepoNameWithoutVersionForTesting())),
             usage);
 
     assertThat(moduleProxy.getName()).isEqualTo("foo");
@@ -143,7 +143,8 @@
                     abridgedModule,
                     extension,
                     module.getRepoMappingWithBazelDepsOnly(
-                        ImmutableMap.of(fooKey, fooKey.getCanonicalRepoNameWithoutVersion())),
+                        ImmutableMap.of(
+                            fooKey, fooKey.getCanonicalRepoNameWithoutVersionForTesting())),
                     usage));
     assertThat(e).hasMessageThat().contains("does not have a tag class named blep");
   }
diff --git a/src/test/java/com/google/devtools/build/lib/bazel/bzlmod/modcommand/ExtensionArgTest.java b/src/test/java/com/google/devtools/build/lib/bazel/bzlmod/modcommand/ExtensionArgTest.java
index 1b9366a..2bd1e58 100644
--- a/src/test/java/com/google/devtools/build/lib/bazel/bzlmod/modcommand/ExtensionArgTest.java
+++ b/src/test/java/com/google/devtools/build/lib/bazel/bzlmod/modcommand/ExtensionArgTest.java
@@ -89,7 +89,7 @@
             .buildOrThrow();
     ImmutableMap<ModuleKey, RepositoryName> moduleKeyToCanonicalNames =
         depGraph.keySet().stream()
-            .collect(toImmutableMap(k -> k, ModuleKey::getCanonicalRepoNameWithVersion));
+            .collect(toImmutableMap(k -> k, ModuleKey::getCanonicalRepoNameWithVersionForTesting));
     ImmutableBiMap<String, ModuleKey> baseModuleDeps = ImmutableBiMap.of("fred", key);
     ImmutableBiMap<String, ModuleKey> baseModuleUnusedDeps = ImmutableBiMap.of();
 
@@ -118,7 +118,7 @@
             .buildOrThrow();
     ImmutableMap<ModuleKey, RepositoryName> moduleKeyToCanonicalNames =
         depGraph.keySet().stream()
-            .collect(toImmutableMap(k -> k, ModuleKey::getCanonicalRepoNameWithVersion));
+            .collect(toImmutableMap(k -> k, ModuleKey::getCanonicalRepoNameWithVersionForTesting));
     ImmutableBiMap<String, ModuleKey> baseModuleDeps = ImmutableBiMap.of("fred", key);
     ImmutableBiMap<String, ModuleKey> baseModuleUnusedDeps = ImmutableBiMap.of();
 
@@ -162,7 +162,7 @@
             .buildOrThrow();
     ImmutableMap<ModuleKey, RepositoryName> moduleKeyToCanonicalNames =
         depGraph.keySet().stream()
-            .collect(toImmutableMap(k -> k, ModuleKey::getCanonicalRepoNameWithVersion));
+            .collect(toImmutableMap(k -> k, ModuleKey::getCanonicalRepoNameWithVersionForTesting));
     ImmutableBiMap<String, ModuleKey> baseModuleDeps =
         ImmutableBiMap.of("foo1", foo1, "foo2", foo2);
     ImmutableBiMap<String, ModuleKey> baseModuleUnusedDeps = ImmutableBiMap.of();
diff --git a/src/test/java/com/google/devtools/build/lib/bazel/bzlmod/modcommand/ModuleArgTest.java b/src/test/java/com/google/devtools/build/lib/bazel/bzlmod/modcommand/ModuleArgTest.java
index fc15ea6..70d6b21 100644
--- a/src/test/java/com/google/devtools/build/lib/bazel/bzlmod/modcommand/ModuleArgTest.java
+++ b/src/test/java/com/google/devtools/build/lib/bazel/bzlmod/modcommand/ModuleArgTest.java
@@ -80,7 +80,7 @@
 
   ImmutableMap<ModuleKey, RepositoryName> moduleKeyToCanonicalNames =
       depGraph.keySet().stream()
-          .collect(toImmutableMap(k -> k, ModuleKey::getCanonicalRepoNameWithVersion));
+          .collect(toImmutableMap(k -> k, ModuleKey::getCanonicalRepoNameWithVersionForTesting));
   ImmutableBiMap<String, ModuleKey> baseModuleDeps = ImmutableBiMap.of("fred", foo2);
   ImmutableBiMap<String, ModuleKey> baseModuleUnusedDeps = ImmutableBiMap.of("fred", foo1);
   RepositoryMapping rootMapping = createRepositoryMapping(ModuleKey.ROOT, "fred", "foo~v2.0");
@@ -270,7 +270,7 @@
 
   @Test
   public void resolve_canonicalRepoName_good() throws Exception {
-    var arg = CanonicalRepoName.create(foo2.getCanonicalRepoNameWithVersion());
+    var arg = CanonicalRepoName.create(foo2.getCanonicalRepoNameWithVersionForTesting());
 
     assertThat(
             arg.resolveToModuleKeys(
@@ -311,7 +311,7 @@
 
   @Test
   public void resolve_canonicalRepoName_unused() throws Exception {
-    var arg = CanonicalRepoName.create(foo1.getCanonicalRepoNameWithVersion());
+    var arg = CanonicalRepoName.create(foo1.getCanonicalRepoNameWithVersionForTesting());
 
     // Without --include_unused, this doesn't resolve, as foo@1.0 has been replaced by foo@2.0.
     assertThat(
diff --git a/src/test/java/com/google/devtools/build/lib/packages/semantics/ConsistencyTest.java b/src/test/java/com/google/devtools/build/lib/packages/semantics/ConsistencyTest.java
index d5b4943..da4b746 100644
--- a/src/test/java/com/google/devtools/build/lib/packages/semantics/ConsistencyTest.java
+++ b/src/test/java/com/google/devtools/build/lib/packages/semantics/ConsistencyTest.java
@@ -129,6 +129,7 @@
         "--experimental_enable_android_migration_apis=" + rand.nextBoolean(),
         "--enable_bzlmod=" + rand.nextBoolean(),
         "--enable_workspace=" + rand.nextBoolean(),
+        "--incompatible_use_plus_in_repo_names=" + rand.nextBoolean(),
         "--experimental_isolated_extension_usages=" + rand.nextBoolean(),
         "--experimental_google_legacy_api=" + rand.nextBoolean(),
         "--experimental_platforms_api=" + rand.nextBoolean(),
@@ -177,6 +178,7 @@
             BuildLanguageOptions.EXPERIMENTAL_ENABLE_ANDROID_MIGRATION_APIS, rand.nextBoolean())
         .setBool(BuildLanguageOptions.ENABLE_BZLMOD, rand.nextBoolean())
         .setBool(BuildLanguageOptions.ENABLE_WORKSPACE, rand.nextBoolean())
+        .setBool(BuildLanguageOptions.INCOMPATIBLE_USE_PLUS_IN_REPO_NAMES, rand.nextBoolean())
         .setBool(BuildLanguageOptions.EXPERIMENTAL_ISOLATED_EXTENSION_USAGES, rand.nextBoolean())
         .setBool(BuildLanguageOptions.EXPERIMENTAL_GOOGLE_LEGACY_API, rand.nextBoolean())
         .setBool(BuildLanguageOptions.EXPERIMENTAL_PLATFORMS_API, rand.nextBoolean())
diff --git a/src/test/tools/bzlmod/MODULE.bazel.lock b/src/test/tools/bzlmod/MODULE.bazel.lock
index be76d81..10efc54 100644
--- a/src/test/tools/bzlmod/MODULE.bazel.lock
+++ b/src/test/tools/bzlmod/MODULE.bazel.lock
@@ -56,8 +56,8 @@
     "https://bcr.bazel.build/modules/upb/0.0.0-20220923-a547704/source.json": "f1ef7d3f9e0e26d4b23d1c39b5f5de71f584dd7d1b4ef83d9bbba6ec7a6a6459",
     "https://bcr.bazel.build/modules/zlib/1.2.11/MODULE.bazel": "07b389abc85fdbca459b69e2ec656ae5622873af3f845e1c9d80fe179f3effa0",
     "https://bcr.bazel.build/modules/zlib/1.2.12/MODULE.bazel": "3b1a8834ada2a883674be8cbd36ede1b6ec481477ada359cd2d3ddc562340b27",
-    "https://bcr.bazel.build/modules/zlib/1.3/MODULE.bazel": "6a9c02f19a24dcedb05572b2381446e27c272cd383aed11d41d99da9e3167a72",
-    "https://bcr.bazel.build/modules/zlib/1.3/source.json": "b6b43d0737af846022636e6e255fd4a96fee0d34f08f3830e6e0bac51465c37c"
+    "https://bcr.bazel.build/modules/zlib/1.3.1.bcr.3/MODULE.bazel": "af322bc08976524477c79d1e45e241b6efbeb918c497e8840b8ab116802dda79",
+    "https://bcr.bazel.build/modules/zlib/1.3.1.bcr.3/source.json": "2be409ac3c7601245958cd4fcdff4288be79ed23bd690b4b951f500d54ee6e7d"
   },
   "selectedYankedVersions": {},
   "moduleExtensions": {