diff --git a/src/libexpr-tests/nix_api_expr.cc b/src/libexpr-tests/nix_api_expr.cc
index 3e5cd0d43..026c89598 100644
--- a/src/libexpr-tests/nix_api_expr.cc
+++ b/src/libexpr-tests/nix_api_expr.cc
@@ -18,13 +18,13 @@ TEST_F(nix_api_expr_test, nix_eval_state_lookup_path)
 {
     auto tmpDir = nix::createTempDir();
     auto delTmpDir = std::make_unique<nix::AutoDelete>(tmpDir, true);
-    auto nixpkgs = tmpDir + "/pkgs";
-    auto nixos = tmpDir + "/cfg";
+    auto nixpkgs = tmpDir / "pkgs";
+    auto nixos = tmpDir / "cfg";
     std::filesystem::create_directories(nixpkgs);
     std::filesystem::create_directories(nixos);
 
-    std::string nixpkgsEntry = "nixpkgs=" + nixpkgs;
-    std::string nixosEntry = "nixos-config=" + nixos;
+    std::string nixpkgsEntry = "nixpkgs=" + nixpkgs.string();
+    std::string nixosEntry = "nixos-config=" + nixos.string();
     const char * lookupPath[] = {nixpkgsEntry.c_str(), nixosEntry.c_str(), nullptr};
 
     auto builder = nix_eval_state_builder_new(ctx, store);
diff --git a/src/libexpr/parser.y b/src/libexpr/parser.y
index 520086e28..c9ad30407 100644
--- a/src/libexpr/parser.y
+++ b/src/libexpr/parser.y
@@ -384,7 +384,7 @@ path_start
             std::string_view($1.p, $1.l)
         );
     }
-    Path path(getHome() + std::string($1.p + 1, $1.l - 1));
+    Path path(getHome().string() + std::string($1.p + 1, $1.l - 1));
     $$ = state->exprs.add<ExprPath>(state->exprs.alloc, ref<SourceAccessor>(state->rootFS), path);
   }
   ;
diff --git a/src/libfetchers/git-lfs-fetch.cc b/src/libfetchers/git-lfs-fetch.cc
index f1982c314..e2b2c2e7d 100644
--- a/src/libfetchers/git-lfs-fetch.cc
+++ b/src/libfetchers/git-lfs-fetch.cc
@@ -268,10 +268,10 @@ void Fetch::fetch(
         return;
     }
 
-    Path cacheDir = getCacheDir() + "/git-lfs";
+    std::filesystem::path cacheDir = getCacheDir() / "git-lfs";
     std::string key = hashString(HashAlgorithm::SHA256, pointerFilePath.rel()).to_string(HashFormat::Base16, false)
                       + "/" + pointer->oid;
-    Path cachePath = cacheDir + "/" + key;
+    std::filesystem::path cachePath = cacheDir / key;
     if (pathExists(cachePath)) {
         debug("using cache entry %s -> %s", key, cachePath);
         sink(readFile(cachePath));
@@ -302,8 +302,8 @@ void Fetch::fetch(
         downloadToSink(ourl, authHeader, sink, sha256, size);
 
         debug("creating cache entry %s -> %s", key, cachePath);
-        if (!pathExists(dirOf(cachePath)))
-            createDirs(dirOf(cachePath));
+        if (!pathExists(cachePath.parent_path()))
+            createDirs(cachePath.parent_path());
         writeFile(cachePath, sink.s);
 
         debug("%s fetched with git-lfs", pointerFilePath);
diff --git a/src/libfetchers/git-utils.cc b/src/libfetchers/git-utils.cc
index 4a7fc3d0d..37f776b11 100644
--- a/src/libfetchers/git-utils.cc
+++ b/src/libfetchers/git-utils.cc
@@ -206,7 +206,7 @@ static void initRepoAtomically(std::filesystem::path & path, bool bare)
     if (pathExists(path.string()))
         return;
 
-    Path tmpDir = createTempDir(os_string_to_string(PathViewNG{std::filesystem::path(path).parent_path()}));
+    std::filesystem::path tmpDir = createTempDir(path.parent_path());
     AutoDelete delTmpDir(tmpDir, true);
     Repository tmpRepo;
 
diff --git a/src/libfetchers/git.cc b/src/libfetchers/git.cc
index 75e3f1214..0e6a6cb69 100644
--- a/src/libfetchers/git.cc
+++ b/src/libfetchers/git.cc
@@ -42,10 +42,10 @@ bool isCacheFileWithinTtl(time_t now, const struct stat & st)
     return st.st_mtime + static_cast<time_t>(settings.tarballTtl) > now;
 }
 
-Path getCachePath(std::string_view key, bool shallow)
+std::filesystem::path getCachePath(std::string_view key, bool shallow)
 {
-    return getCacheDir() + "/gitv3/" + hashString(HashAlgorithm::SHA256, key).to_string(HashFormat::Nix32, false)
-           + (shallow ? "-shallow" : "");
+    return getCacheDir() / "gitv3"
+           / (hashString(HashAlgorithm::SHA256, key).to_string(HashFormat::Nix32, false) + (shallow ? "-shallow" : ""));
 }
 
 // Returns the name of the HEAD branch.
@@ -55,7 +55,7 @@ Path getCachePath(std::string_view key, bool shallow)
 //
 //   ref: refs/heads/main       HEAD
 //   ...
-std::optional<std::string> readHead(const Path & path)
+std::optional<std::string> readHead(const std::filesystem::path & path)
 {
     auto [status, output] = runProgram(
         RunOptions{
@@ -86,7 +86,7 @@ std::optional<std::string> readHead(const Path & path)
 // Persist the HEAD ref from the remote repo in the local cached repo.
 bool storeCachedHead(const std::string & actualUrl, bool shallow, const std::string & headRef)
 {
-    Path cacheDir = getCachePath(actualUrl, shallow);
+    std::filesystem::path cacheDir = getCachePath(actualUrl, shallow);
     try {
         runProgram("git", true, {"-C", cacheDir, "--git-dir", ".", "symbolic-ref", "--", "HEAD", headRef});
     } catch (ExecError & e) {
@@ -109,8 +109,8 @@ std::optional<std::string> readHeadCached(const std::string & actualUrl, bool sh
 {
     // Create a cache path to store the branch of the HEAD ref. Append something
     // in front of the URL to prevent collision with the repository itself.
-    Path cacheDir = getCachePath(actualUrl, shallow);
-    Path headRefFile = cacheDir + "/HEAD";
+    std::filesystem::path cacheDir = getCachePath(actualUrl, shallow);
+    std::filesystem::path headRefFile = cacheDir / "HEAD";
 
     time_t now = time(0);
     struct stat st;
diff --git a/src/libfetchers/include/nix/fetchers/registry.hh b/src/libfetchers/include/nix/fetchers/registry.hh
index c9c8b162f..dc7e3edb5 100644
--- a/src/libfetchers/include/nix/fetchers/registry.hh
+++ b/src/libfetchers/include/nix/fetchers/registry.hh
@@ -39,7 +39,7 @@ struct Registry
 
     static std::shared_ptr<Registry> read(const Settings & settings, const SourcePath & path, RegistryType type);
 
-    void write(const Path & path);
+    void write(const std::filesystem::path & path);
 
     void add(const Input & from, const Input & to, const Attrs & extraAttrs);
 
@@ -50,9 +50,9 @@ typedef std::vector<std::shared_ptr<Registry>> Registries;
 
 std::shared_ptr<Registry> getUserRegistry(const Settings & settings);
 
-std::shared_ptr<Registry> getCustomRegistry(const Settings & settings, const Path & p);
+std::shared_ptr<Registry> getCustomRegistry(const Settings & settings, const std::filesystem::path & p);
 
-Path getUserRegistryPath();
+std::filesystem::path getUserRegistryPath();
 
 Registries getRegistries(const Settings & settings, Store & store);
 
diff --git a/src/libfetchers/mercurial.cc b/src/libfetchers/mercurial.cc
index 87e18133d..65999497c 100644
--- a/src/libfetchers/mercurial.cc
+++ b/src/libfetchers/mercurial.cc
@@ -213,11 +213,11 @@ struct MercurialInputScheme : InputScheme
                     runHg({"status", "-R", actualUrl, "--clean", "--modified", "--added", "--no-status", "--print0"}),
                     "\0"s);
 
-                Path actualPath(absPath(actualUrl));
+                std::filesystem::path actualPath(absPath(actualUrl));
 
                 PathFilter filter = [&](const Path & p) -> bool {
-                    assert(hasPrefix(p, actualPath));
-                    std::string file(p, actualPath.size() + 1);
+                    assert(hasPrefix(p, actualPath.string()));
+                    std::string file(p, actualPath.string().size() + 1);
 
                     auto st = lstat(p);
 
@@ -232,7 +232,7 @@ struct MercurialInputScheme : InputScheme
 
                 auto storePath = store.addToStore(
                     input.getName(),
-                    {getFSSourceAccessor(), CanonPath(actualPath)},
+                    {getFSSourceAccessor(), CanonPath(actualPath.string())},
                     ContentAddressMethod::Raw::NixArchive,
                     HashAlgorithm::SHA256,
                     {},
@@ -275,10 +275,8 @@ struct MercurialInputScheme : InputScheme
                 return makeResult(res->value, res->storePath);
         }
 
-        Path cacheDir =
-            fmt("%s/hg/%s",
-                getCacheDir(),
-                hashString(HashAlgorithm::SHA256, actualUrl).to_string(HashFormat::Nix32, false));
+        std::filesystem::path cacheDir =
+            getCacheDir() / "hg" / hashString(HashAlgorithm::SHA256, actualUrl).to_string(HashFormat::Nix32, false);
 
         /* If this is a commit hash that we already have, we don't
            have to pull again. */
@@ -292,7 +290,7 @@ struct MercurialInputScheme : InputScheme
                 try {
                     runHg({"pull", "-R", cacheDir, "--", actualUrl});
                 } catch (ExecError & e) {
-                    auto transJournal = cacheDir + "/.hg/store/journal";
+                    auto transJournal = cacheDir / ".hg" / "store" / "journal";
                     /* hg throws "abandoned transaction" error only if this file exists */
                     if (pathExists(transJournal)) {
                         runHg({"recover", "-R", cacheDir});
@@ -302,7 +300,7 @@ struct MercurialInputScheme : InputScheme
                     }
                 }
             } else {
-                createDirs(dirOf(cacheDir));
+                createDirs(dirOf(cacheDir.string()));
                 runHg({"clone", "--noupdate", "--", actualUrl, cacheDir});
             }
         }
@@ -328,14 +326,14 @@ struct MercurialInputScheme : InputScheme
         if (auto res = settings.getCache()->lookupStorePath(revInfoKey(rev), store))
             return makeResult(res->value, res->storePath);
 
-        Path tmpDir = createTempDir();
+        std::filesystem::path tmpDir = createTempDir();
         AutoDelete delTmpDir(tmpDir, true);
 
         runHg({"archive", "-R", cacheDir, "-r", rev.gitRev(), tmpDir});
 
-        deletePath(tmpDir + "/.hg_archival.txt");
+        deletePath(tmpDir / ".hg_archival.txt");
 
-        auto storePath = store.addToStore(name, {getFSSourceAccessor(), CanonPath(tmpDir)});
+        auto storePath = store.addToStore(name, {getFSSourceAccessor(), CanonPath(tmpDir.string())});
 
         Attrs infoAttrs({
             {"revCount", (uint64_t) revCount},
diff --git a/src/libfetchers/registry.cc b/src/libfetchers/registry.cc
index cb360f03c..c81eb6b53 100644
--- a/src/libfetchers/registry.cc
+++ b/src/libfetchers/registry.cc
@@ -56,7 +56,7 @@ std::shared_ptr<Registry> Registry::read(const Settings & settings, const Source
     return registry;
 }
 
-void Registry::write(const Path & path)
+void Registry::write(const std::filesystem::path & path)
 {
     nlohmann::json arr;
     for (auto & entry : entries) {
@@ -74,7 +74,7 @@ void Registry::write(const Path & path)
     json["version"] = 2;
     json["flakes"] = std::move(arr);
 
-    createDirs(dirOf(path));
+    createDirs(path.parent_path());
     writeFile(path, json.dump(2));
 }
 
@@ -90,38 +90,38 @@ void Registry::remove(const Input & input)
         entries.end());
 }
 
-static Path getSystemRegistryPath()
+static std::filesystem::path getSystemRegistryPath()
 {
-    return settings.nixConfDir + "/registry.json";
+    return settings.nixConfDir / "registry.json";
 }
 
 static std::shared_ptr<Registry> getSystemRegistry(const Settings & settings)
 {
     static auto systemRegistry = Registry::read(
         settings,
-        SourcePath{getFSSourceAccessor(), CanonPath{getSystemRegistryPath()}}.resolveSymlinks(),
+        SourcePath{getFSSourceAccessor(), CanonPath{getSystemRegistryPath().string()}}.resolveSymlinks(),
         Registry::System);
     return systemRegistry;
 }
 
-Path getUserRegistryPath()
+std::filesystem::path getUserRegistryPath()
 {
-    return getConfigDir() + "/registry.json";
+    return getConfigDir() / "registry.json";
 }
 
 std::shared_ptr<Registry> getUserRegistry(const Settings & settings)
 {
     static auto userRegistry = Registry::read(
         settings,
-        SourcePath{getFSSourceAccessor(), CanonPath{getUserRegistryPath()}}.resolveSymlinks(),
+        SourcePath{getFSSourceAccessor(), CanonPath{getUserRegistryPath().string()}}.resolveSymlinks(),
         Registry::User);
     return userRegistry;
 }
 
-std::shared_ptr<Registry> getCustomRegistry(const Settings & settings, const Path & p)
+std::shared_ptr<Registry> getCustomRegistry(const Settings & settings, const std::filesystem::path & p)
 {
-    static auto customRegistry =
-        Registry::read(settings, SourcePath{getFSSourceAccessor(), CanonPath{p}}.resolveSymlinks(), Registry::Custom);
+    static auto customRegistry = Registry::read(
+        settings, SourcePath{getFSSourceAccessor(), CanonPath{p.string()}}.resolveSymlinks(), Registry::Custom);
     return customRegistry;
 }
 
diff --git a/src/libflake-tests/nix_api_flake.cc b/src/libflake-tests/nix_api_flake.cc
index da7f01401..84ac8eb40 100644
--- a/src/libflake-tests/nix_api_flake.cc
+++ b/src/libflake-tests/nix_api_flake.cc
@@ -86,7 +86,7 @@ TEST_F(nix_api_store_test, nix_api_load_flake)
     auto tmpDir = nix::createTempDir();
     nix::AutoDelete delTmpDir(tmpDir, true);
 
-    nix::writeFile(tmpDir + "/flake.nix", R"(
+    nix::writeFile(tmpDir / "flake.nix", R"(
         {
             outputs = { ... }: {
                 hello = "potato";
@@ -121,7 +121,8 @@ TEST_F(nix_api_store_test, nix_api_load_flake)
     assert_ctx_ok();
     ASSERT_NE(nullptr, parseFlags);
 
-    auto r0 = nix_flake_reference_parse_flags_set_base_directory(ctx, parseFlags, tmpDir.c_str(), tmpDir.size());
+    auto r0 =
+        nix_flake_reference_parse_flags_set_base_directory(ctx, parseFlags, tmpDir.c_str(), tmpDir.string().size());
     assert_ctx_ok();
     ASSERT_EQ(NIX_OK, r0);
 
@@ -177,8 +178,8 @@ TEST_F(nix_api_store_test, nix_api_load_flake_with_flags)
     auto tmpDir = nix::createTempDir();
     nix::AutoDelete delTmpDir(tmpDir, true);
 
-    nix::createDirs(tmpDir + "/b");
-    nix::writeFile(tmpDir + "/b/flake.nix", R"(
+    nix::createDirs(tmpDir / "b");
+    nix::writeFile(tmpDir / "b" / "flake.nix", R"(
         {
             outputs = { ... }: {
                 hello = "BOB";
@@ -186,18 +187,18 @@ TEST_F(nix_api_store_test, nix_api_load_flake_with_flags)
         }
     )");
 
-    nix::createDirs(tmpDir + "/a");
-    nix::writeFile(tmpDir + "/a/flake.nix", R"(
+    nix::createDirs(tmpDir / "a");
+    nix::writeFile(tmpDir / "a" / "flake.nix", R"(
         {
-            inputs.b.url = ")" + tmpDir + R"(/b";
+            inputs.b.url = ")" + tmpDir.string() + R"(/b";
             outputs = { b, ... }: {
                 hello = b.hello;
             };
         }
     )");
 
-    nix::createDirs(tmpDir + "/c");
-    nix::writeFile(tmpDir + "/c/flake.nix", R"(
+    nix::createDirs(tmpDir / "c");
+    nix::writeFile(tmpDir / "c" / "flake.nix", R"(
         {
             outputs = { ... }: {
                 hello = "Claire";
@@ -230,7 +231,8 @@ TEST_F(nix_api_store_test, nix_api_load_flake_with_flags)
     assert_ctx_ok();
     ASSERT_NE(nullptr, parseFlags);
 
-    auto r0 = nix_flake_reference_parse_flags_set_base_directory(ctx, parseFlags, tmpDir.c_str(), tmpDir.size());
+    auto r0 =
+        nix_flake_reference_parse_flags_set_base_directory(ctx, parseFlags, tmpDir.c_str(), tmpDir.string().size());
     assert_ctx_ok();
     ASSERT_EQ(NIX_OK, r0);
 
diff --git a/src/libstore-tests/nix_api_store.cc b/src/libstore-tests/nix_api_store.cc
index a7fa4d8d8..142f648d3 100644
--- a/src/libstore-tests/nix_api_store.cc
+++ b/src/libstore-tests/nix_api_store.cc
@@ -212,9 +212,9 @@ TEST_F(nix_api_store_test, nix_store_real_path)
 TEST_F(nix_api_util_context, nix_store_real_path_relocated)
 {
     auto tmp = nix::createTempDir();
-    std::string storeRoot = tmp + "/store";
-    std::string stateDir = tmp + "/state";
-    std::string logDir = tmp + "/log";
+    std::string storeRoot = tmp / "store";
+    std::string stateDir = tmp / "state";
+    std::string logDir = tmp / "log";
     const char * rootkv[] = {"root", storeRoot.c_str()};
     const char * statekv[] = {"state", stateDir.c_str()};
     const char * logkv[] = {"log", logDir.c_str()};
@@ -250,7 +250,8 @@ TEST_F(nix_api_util_context, nix_store_real_path_relocated)
 
 TEST_F(nix_api_util_context, nix_store_real_path_binary_cache)
 {
-    Store * store = nix_store_open(ctx, nix::fmt("file://%s/binary-cache", nix::createTempDir()).c_str(), nullptr);
+    Store * store =
+        nix_store_open(ctx, nix::fmt("file://%s/binary-cache", nix::createTempDir().string()).c_str(), nullptr);
     assert_ctx_ok();
     ASSERT_NE(store, nullptr);
 
diff --git a/src/libstore/globals.cc b/src/libstore/globals.cc
index 8c542b686..9e72f8577 100644
--- a/src/libstore/globals.cc
+++ b/src/libstore/globals.cc
@@ -486,7 +486,7 @@ void initLibStore(bool loadConfig)
     /* On macOS, don't use the per-session TMPDIR (as set e.g. by
        sshd). This breaks build users because they don't have access
        to the TMPDIR, in particular in ‘nix-store --serve’. */
-    if (hasPrefix(defaultTempDir(), "/var/folders/"))
+    if (hasPrefix(defaultTempDir().string(), "/var/folders/"))
         unsetenv("TMPDIR");
 #endif
 
diff --git a/src/libstore/include/nix/store/globals.hh b/src/libstore/include/nix/store/globals.hh
index 5ddfbee30..fa4f7abbd 100644
--- a/src/libstore/include/nix/store/globals.hh
+++ b/src/libstore/include/nix/store/globals.hh
@@ -101,7 +101,7 @@ public:
     /**
      * The directory where system configuration files are stored.
      */
-    Path nixConfDir;
+    std::filesystem::path nixConfDir;
 
     /**
      * A list of user configuration files to load.
@@ -292,7 +292,7 @@ public:
 
     Setting<std::string> builders{
         this,
-        "@" + nixConfDir + "/machines",
+        "@" + nixConfDir.string() + "/machines",
         "builders",
         R"(
           A semicolon- or newline-separated list of build machines.
diff --git a/src/libstore/local-store.cc b/src/libstore/local-store.cc
index a849576f6..ab242bd84 100644
--- a/src/libstore/local-store.cc
+++ b/src/libstore/local-store.cc
@@ -1332,7 +1332,7 @@ std::pair<std::filesystem::path, AutoCloseFD> LocalStore::createTempDirInStore()
         /* There is a slight possibility that `tmpDir' gets deleted by
            the GC between createTempDir() and when we acquire a lock on it.
            We'll repeat until 'tmpDir' exists and we've locked it. */
-        tmpDirFn = createTempDir(config->realStoreDir, "tmp");
+        tmpDirFn = createTempDir(std::filesystem::path{config->realStoreDir.get()}, "tmp");
         tmpDirFd = openDirectory(tmpDirFn);
         if (!tmpDirFd) {
             continue;
diff --git a/src/libstore/unix/build/darwin-derivation-builder.cc b/src/libstore/unix/build/darwin-derivation-builder.cc
index 613ec6d54..24329bffc 100644
--- a/src/libstore/unix/build/darwin-derivation-builder.cc
+++ b/src/libstore/unix/build/darwin-derivation-builder.cc
@@ -174,7 +174,7 @@ struct DarwinDerivationBuilder : DerivationBuilderImpl
         /* The tmpDir in scope points at the temporary build directory for our derivation. Some packages try different
            mechanisms to find temporary directories, so we want to open up a broader place for them to put their files,
            if needed. */
-        Path globalTmpDir = canonPath(defaultTempDir(), true);
+        Path globalTmpDir = canonPath(defaultTempDir().string(), true);
 
         /* They don't like trailing slashes on subpath directives */
         while (!globalTmpDir.empty() && globalTmpDir.back() == '/')
diff --git a/src/libutil/file-system.cc b/src/libutil/file-system.cc
index 758173f41..6b145b343 100644
--- a/src/libutil/file-system.cc
+++ b/src/libutil/file-system.cc
@@ -676,16 +676,16 @@ void AutoUnmount::cancel()
 
 //////////////////////////////////////////////////////////////////////
 
-std::string defaultTempDir()
+std::filesystem::path defaultTempDir()
 {
     return getEnvNonEmpty("TMPDIR").value_or("/tmp");
 }
 
-Path createTempDir(const Path & tmpRoot, const Path & prefix, mode_t mode)
+std::filesystem::path createTempDir(const std::filesystem::path & tmpRoot, const std::string & prefix, mode_t mode)
 {
     while (1) {
         checkInterrupt();
-        Path tmpDir = makeTempPath(tmpRoot, prefix);
+        std::filesystem::path tmpDir = makeTempPath(tmpRoot, prefix);
         if (mkdir(
                 tmpDir.c_str()
 #ifndef _WIN32 // TODO abstract mkdir perms for Windows
@@ -727,11 +727,11 @@ std::pair<AutoCloseFD, Path> createTempFile(const Path & prefix)
     return {std::move(fd), tmpl};
 }
 
-Path makeTempPath(const Path & root, const Path & suffix)
+std::filesystem::path makeTempPath(const std::filesystem::path & root, const std::string & suffix)
 {
     // start the counter at a random value to minimize issues with preexisting temp paths
     static std::atomic<uint32_t> counter(std::random_device{}());
-    auto tmpRoot = canonPath(root.empty() ? defaultTempDir() : root, true);
+    auto tmpRoot = canonPath(root.empty() ? defaultTempDir().string() : root.string(), true);
     return fmt("%1%/%2%-%3%-%4%", tmpRoot, suffix, getpid(), counter.fetch_add(1, std::memory_order_relaxed));
 }
 
diff --git a/src/libutil/include/nix/util/file-system.hh b/src/libutil/include/nix/util/file-system.hh
index a203af2aa..7673c24fd 100644
--- a/src/libutil/include/nix/util/file-system.hh
+++ b/src/libutil/include/nix/util/file-system.hh
@@ -334,7 +334,8 @@ typedef std::unique_ptr<DIR, DIRDeleter> AutoCloseDir;
 /**
  * Create a temporary directory.
  */
-Path createTempDir(const Path & tmpRoot = "", const Path & prefix = "nix", mode_t mode = 0755);
+std::filesystem::path
+createTempDir(const std::filesystem::path & tmpRoot = "", const std::string & prefix = "nix", mode_t mode = 0755);
 
 /**
  * Create a temporary file, returning a file handle and its path.
@@ -344,7 +345,7 @@ std::pair<AutoCloseFD, Path> createTempFile(const Path & prefix = "nix");
 /**
  * Return `TMPDIR`, or the default temporary directory if unset or empty.
  */
-Path defaultTempDir();
+std::filesystem::path defaultTempDir();
 
 /**
  * Interpret `exe` as a location in the ambient file system and return
@@ -358,7 +359,7 @@ bool isExecutableFileAmbient(const std::filesystem::path & exe);
  * The constructed path looks like `<root><suffix>-<pid>-<unique>`. To create a
  * path nested in a directory, provide a suffix starting with `/`.
  */
-Path makeTempPath(const Path & root, const Path & suffix = ".tmp");
+std::filesystem::path makeTempPath(const std::filesystem::path & root, const std::string & suffix = ".tmp");
 
 /**
  * Used in various places.