diff --git a/src/libcmd/repl.cc b/src/libcmd/repl.cc
index ffb14c42ec7..0324d98f040 100644
--- a/src/libcmd/repl.cc
+++ b/src/libcmd/repl.cc
@@ -710,7 +710,7 @@ void NixRepl::loadFlake(const std::string & flakeRefS)
     try {
         cwd = std::filesystem::current_path();
     } catch (std::filesystem::filesystem_error & e) {
-        throw SysError("cannot determine current working directory");
+        throw SystemError(e.code(), "cannot determine current working directory");
     }
 
     auto flakeRef = parseFlakeRef(fetchSettings, flakeRefS, cwd.string(), true);
diff --git a/src/libfetchers/git-utils.cc b/src/libfetchers/git-utils.cc
index 9b33d8e91eb..e3bce13b215 100644
--- a/src/libfetchers/git-utils.cc
+++ b/src/libfetchers/git-utils.cc
@@ -247,7 +247,8 @@ static void initRepoAtomically(std::filesystem::path & path, GitRepo::Options op
             || e.code() == std::errc::directory_not_empty) {
             return;
         } else
-            throw SysError("moving temporary git repository from %s to %s", PathFmt(tmpDir), PathFmt(path));
+            throw SystemError(
+                e.code(), "moving temporary git repository from %s to %s", PathFmt(tmpDir), PathFmt(path));
     }
     // we successfully moved the repository, so the temporary directory no longer exists.
     delTmpDir.cancel();
diff --git a/src/libstore/builtins/unpack-channel.cc b/src/libstore/builtins/unpack-channel.cc
index 317cbe9ef1f..f1b30572d88 100644
--- a/src/libstore/builtins/unpack-channel.cc
+++ b/src/libstore/builtins/unpack-channel.cc
@@ -36,8 +36,8 @@ static void builtinUnpackChannel(const BuiltinBuilderContext & ctx)
     auto target = out / channelName;
     try {
         std::filesystem::rename(fileName, target);
-    } catch (std::filesystem::filesystem_error &) {
-        throw SysError("failed to rename %1% to %2%", fileName, target.string());
+    } catch (std::filesystem::filesystem_error & e) {
+        throw SystemError(e.code(), "failed to rename %1% to %2%", fileName, target.string());
     }
 }
 
diff --git a/src/libstore/gc.cc b/src/libstore/gc.cc
index 15642dcd6d4..2424bdce55d 100644
--- a/src/libstore/gc.cc
+++ b/src/libstore/gc.cc
@@ -272,7 +272,7 @@ void LocalStore::findRoots(const Path & path, std::filesystem::file_type type, R
             || e.code() == std::errc::not_a_directory)
             printInfo("cannot read potential root '%1%'", path);
         else
-            throw;
+            throw SystemError(e.code(), "finding GC roots in '%1%'", path);
     }
 
     catch (SystemError & e) {
diff --git a/src/libstore/local-gc.cc b/src/libstore/local-gc.cc
index 9e3bbfb5ccc..681ac28c514 100644
--- a/src/libstore/local-gc.cc
+++ b/src/libstore/local-gc.cc
@@ -35,7 +35,7 @@ static void readProcLink(const std::filesystem::path & file, UncheckedRoots & ro
         if (e.code() == std::errc::no_such_file_or_directory || e.code() == std::errc::permission_denied
             || e.code() == std::errc::no_such_process)
             return;
-        throw;
+        throw SystemError(e.code(), "reading symlink '%s'", PathFmt(file));
     }
     if (buf.is_absolute())
         roots[buf.string()].emplace(file.string());
diff --git a/src/libstore/machines.cc b/src/libstore/machines.cc
index f5f630ad01d..1a97f96a250 100644
--- a/src/libstore/machines.cc
+++ b/src/libstore/machines.cc
@@ -111,8 +111,8 @@ static std::vector<std::string> expandBuilderLines(const std::string & builders)
                 std::string text;
                 try {
                     text = readFile(path);
-                } catch (const SysError & e) {
-                    if (e.errNo != ENOENT)
+                } catch (const SystemError & e) {
+                    if (!e.is(std::errc::no_such_file_or_directory))
                         throw;
                     debug("cannot find machines file '%s'", path);
                     continue;
diff --git a/src/libstore/optimise-store.cc b/src/libstore/optimise-store.cc
index efdf748826f..9e5cc77ab5c 100644
--- a/src/libstore/optimise-store.cc
+++ b/src/libstore/optimise-store.cc
@@ -202,14 +202,13 @@ void LocalStore::optimisePath_(
                    full.  When that happens, it's fine to ignore it: we
                    just effectively disable deduplication of this
                    file.
-                   TODO: Get rid of errno, use error code.
                    */
-                printInfo("cannot link %s to '%s': %s", PathFmt(linkPath), path, strerror(errno));
+                printInfo("cannot link %s to '%s': %s", PathFmt(linkPath), path, e.code().message());
                 return;
             }
 
             else
-                throw;
+                throw SystemError(e.code(), "creating hard link from %1% to %2%", PathFmt(linkPath), path);
         }
     }
 
@@ -250,7 +249,7 @@ void LocalStore::optimisePath_(
                 printInfo("%1% has maximum number of links", PathFmt(linkPath));
             return;
         }
-        throw;
+        throw SystemError(e.code(), "creating hard link from %1% to %2%", PathFmt(linkPath), PathFmt(tempLink));
     }
 
     /* Atomically replace the old file with the new hard link. */
@@ -271,7 +270,7 @@ void LocalStore::optimisePath_(
             debug("%s has reached maximum number of links", PathFmt(linkPath));
             return;
         }
-        throw;
+        throw SystemError(e.code(), "renaming %1% to %2%", PathFmt(tempLink), path);
     }
 
     stats.filesLinked++;
diff --git a/src/libstore/profiles.cc b/src/libstore/profiles.cc
index b0126351a21..c90ed1e5023 100644
--- a/src/libstore/profiles.cc
+++ b/src/libstore/profiles.cc
@@ -103,7 +103,7 @@ static void removeFile(const std::filesystem::path & path)
     try {
         std::filesystem::remove(path);
     } catch (std::filesystem::filesystem_error & e) {
-        throw SysError("removing file %1%", PathFmt(path));
+        throw SystemError(e.code(), "removing file %1%", PathFmt(path));
     }
 }
 
@@ -324,8 +324,6 @@ std::filesystem::path getDefaultProfile(ProfileDirsOptions settings)
         return absPath(readLink(profileLink), &linkDir);
     } catch (Error &) {
         return profileLink;
-    } catch (std::filesystem::filesystem_error &) {
-        return profileLink;
     }
 }
 
diff --git a/src/libutil-tests/file-system.cc b/src/libutil-tests/file-system.cc
index e96694ff7c6..6bfcb7d0c00 100644
--- a/src/libutil-tests/file-system.cc
+++ b/src/libutil-tests/file-system.cc
@@ -319,7 +319,7 @@ TEST(chmodIfNeeded, works)
 
 TEST(chmodIfNeeded, nonexistent)
 {
-    ASSERT_THROW(chmodIfNeeded("/schnitzel/darmstadt/pommes", 0755), SysError);
+    ASSERT_THROW(chmodIfNeeded("/schnitzel/darmstadt/pommes", 0755), SystemError);
 }
 
 /* ----------------------------------------------------------------------------
@@ -340,7 +340,7 @@ TEST(DirectoryIterator, works)
 
 TEST(DirectoryIterator, nonexistent)
 {
-    ASSERT_THROW(DirectoryIterator("/schnitzel/darmstadt/pommes"), SysError);
+    ASSERT_THROW(DirectoryIterator("/schnitzel/darmstadt/pommes"), SystemError);
 }
 
 /* ----------------------------------------------------------------------------
diff --git a/src/libutil/file-system.cc b/src/libutil/file-system.cc
index 2f671627ff9..4458a3a8362 100644
--- a/src/libutil/file-system.cc
+++ b/src/libutil/file-system.cc
@@ -40,9 +40,9 @@ DirectoryIterator::DirectoryIterator(const std::filesystem::path & p)
         // **Attempt to create the underlying directory_iterator**
         it_ = std::filesystem::directory_iterator(p);
     } catch (const std::filesystem::filesystem_error & e) {
-        // **Catch filesystem_error and throw SysError**
-        // Adapt the error message as needed for SysError
-        throw SysError("cannot read directory %s", PathFmt(p));
+        // **Catch filesystem_error and throw SystemError**
+        // Adapt the error message as needed for SystemError
+        throw SystemError(e.code(), "cannot read directory %s", PathFmt(p));
     }
 }
 
@@ -280,7 +280,11 @@ bool pathAccessible(const std::filesystem::path & path)
 std::filesystem::path readLink(const std::filesystem::path & path)
 {
     checkInterrupt();
-    return std::filesystem::read_symlink(path);
+    try {
+        return std::filesystem::read_symlink(path);
+    } catch (std::filesystem::filesystem_error & e) {
+        throw SystemError(e.code(), "reading symbolic link '%s'", PathFmt(path));
+    }
 }
 
 Path readLink(const Path & path)
@@ -463,7 +467,7 @@ void createDirs(const std::filesystem::path & path)
     try {
         std::filesystem::create_directories(path);
     } catch (std::filesystem::filesystem_error & e) {
-        throw SysError("creating directory '%1%'", path.string());
+        throw SystemError(e.code(), "creating directory '%1%'", path.string());
     }
 }
 
@@ -664,7 +668,7 @@ void replaceSymlink(const std::filesystem::path & target, const std::filesystem:
         } catch (std::filesystem::filesystem_error & e) {
             if (e.code() == std::errc::file_exists)
                 continue;
-            throw SysError("creating symlink %1% -> %2%", PathFmt(tmp), PathFmt(target));
+            throw SystemError(e.code(), "creating symlink %1% -> %2%", PathFmt(tmp), PathFmt(target));
         }
 
         try {
@@ -672,7 +676,7 @@ void replaceSymlink(const std::filesystem::path & target, const std::filesystem:
         } catch (std::filesystem::filesystem_error & e) {
             if (e.code() == std::errc::file_exists)
                 continue;
-            throw SysError("renaming %1% to %2%", PathFmt(tmp), PathFmt(link));
+            throw SystemError(e.code(), "renaming %1% to %2%", PathFmt(tmp), PathFmt(link));
         }
 
         break;
@@ -773,7 +777,7 @@ std::filesystem::path makeParentCanonical(const std::filesystem::path & rawPath)
         }
         return std::filesystem::canonical(parent) / path.filename();
     } catch (std::filesystem::filesystem_error & e) {
-        throw SysError("canonicalising parent path of %1%", PathFmt(path));
+        throw SystemError(e.code(), "canonicalising parent path of %1%", PathFmt(path));
     }
 }
 
diff --git a/src/libutil/include/nix/util/error.hh b/src/libutil/include/nix/util/error.hh
index 4f6d2363d05..d9babf34d1c 100644
--- a/src/libutil/include/nix/util/error.hh
+++ b/src/libutil/include/nix/util/error.hh
@@ -127,20 +127,20 @@ public:
     BaseError & operator=(BaseError &&) = default;
 
     template<typename... Args>
-    BaseError(unsigned int status, const Args &... args)
-        : err{.level = lvlError, .msg = HintFmt(args...), .pos = {}, .status = status}
+    BaseError(unsigned int status, Args &&... args)
+        : err{.level = lvlError, .msg = HintFmt(std::forward<Args>(args)...), .pos = {}, .status = status}
     {
     }
 
     template<typename... Args>
-    explicit BaseError(const std::string & fs, const Args &... args)
-        : err{.level = lvlError, .msg = HintFmt(fs, args...), .pos = {}}
+    explicit BaseError(const std::string & fs, Args &&... args)
+        : err{.level = lvlError, .msg = HintFmt(fs, std::forward<Args>(args)...), .pos = {}}
     {
     }
 
     template<typename... Args>
-    BaseError(const Suggestions & sug, const Args &... args)
-        : err{.level = lvlError, .msg = HintFmt(args...), .pos = {}, .suggestions = sug}
+    BaseError(const Suggestions & sug, Args &&... args)
+        : err{.level = lvlError, .msg = HintFmt(std::forward<Args>(args)...), .pos = {}, .suggestions = sug}
     {
     }
 
@@ -204,9 +204,9 @@ public:
      * @param args... Format string arguments.
      */
     template<typename... Args>
-    void addTrace(std::shared_ptr<const Pos> && pos, std::string_view fs, const Args &... args)
+    void addTrace(std::shared_ptr<const Pos> && pos, std::string_view fs, Args &&... args)
     {
-        addTrace(std::move(pos), HintFmt(std::string(fs), args...));
+        addTrace(std::move(pos), HintFmt(std::string(fs), std::forward<Args>(args)...));
     }
 
     /**
@@ -248,19 +248,39 @@ MakeError(UnimplementedError, Error);
 class SystemError : public Error
 {
     std::error_code errorCode;
+    std::string errorDetails;
 
-public:
+protected:
+
+    /**
+     * Just here to allow derived classes to use the right constructor
+     * (the protected one).
+     */
+    struct Disambig
+    {};
+
+    /**
+     * Protected constructor for subclasses that provide their own error message.
+     * The error message is appended to the formatted hint.
+     */
     template<typename... Args>
-    SystemError(std::errc posixErrNo, Args &&... args)
-        : Error(std::forward<Args>(args)...)
-        , errorCode(std::make_error_code(posixErrNo))
+    SystemError(Disambig, std::error_code errorCode, std::string_view errorDetails, Args &&... args)
+        : Error("")
+        , errorCode(errorCode)
+        , errorDetails(errorDetails)
     {
+        auto hf = HintFmt(std::forward<Args>(args)...);
+        err.msg = HintFmt("%s: %s", Uncolored(hf.str()), errorDetails);
     }
 
+public:
+    /**
+     * Construct with an error code. The error code's message is automatically
+     * appended to the error message.
+     */
     template<typename... Args>
     SystemError(std::error_code errorCode, Args &&... args)
-        : Error(std::forward<Args>(args)...)
-        , errorCode(errorCode)
+        : SystemError(Disambig{}, errorCode, errorCode.message(), std::forward<Args>(args)...)
     {
     }
 
@@ -301,12 +321,14 @@ public:
      * will be used to try to add additional information to the message.
      */
     template<typename... Args>
-    SysError(int errNo, const Args &... args)
-        : SystemError(static_cast<std::errc>(errNo), "")
+    SysError(int errNo, Args &&... args)
+        : SystemError(
+              Disambig{},
+              std::make_error_code(static_cast<std::errc>(errNo)),
+              strerror(errNo),
+              std::forward<Args>(args)...)
         , errNo(errNo)
     {
-        auto hf = HintFmt(args...);
-        err.msg = HintFmt("%1%: %2%", Uncolored(hf.str()), strerror(errNo));
     }
 
     /**
@@ -316,8 +338,8 @@ public:
      * calling this constructor!
      */
     template<typename... Args>
-    SysError(const Args &... args)
-        : SysError(errno, args...)
+    SysError(Args &&... args)
+        : SysError(errno, std::forward<Args>(args)...)
     {
     }
 };
@@ -381,12 +403,14 @@ public:
      * information to the message.
      */
     template<typename... Args>
-    WinError(DWORD lastError, const Args &... args)
-        : SystemError(std::error_code(lastError, std::system_category()), "")
+    WinError(DWORD lastError, Args &&... args)
+        : SystemError(
+              Disambig{},
+              std::error_code(lastError, std::system_category()),
+              renderError(lastError),
+              std::forward<Args>(args)...)
         , lastError(lastError)
     {
-        auto hf = HintFmt(args...);
-        err.msg = HintFmt("%1%: %2%", Uncolored(hf.str()), renderError(lastError));
     }
 
     /**
@@ -396,14 +420,14 @@ public:
      * before calling this constructor!
      */
     template<typename... Args>
-    WinError(const Args &... args)
-        : WinError(GetLastError(), args...)
+    WinError(Args &&... args)
+        : WinError(GetLastError(), std::forward<Args>(args)...)
     {
     }
 
 private:
 
-    std::string renderError(DWORD lastError);
+    static std::string renderError(DWORD lastError);
 };
 
 } // namespace windows
diff --git a/src/libutil/include/nix/util/file-system-at.hh b/src/libutil/include/nix/util/file-system-at.hh
index b1b636d83b8..4026e68e5d8 100644
--- a/src/libutil/include/nix/util/file-system-at.hh
+++ b/src/libutil/include/nix/util/file-system-at.hh
@@ -75,7 +75,7 @@ namespace linux {
  *
  * @see https://man7.org/linux/man-pages/man2/openat2.2.html
  * @see https://man7.org/linux/man-pages/man2/open_how.2type.html
-v*
+ *
  * @param flags O_* flags
  * @param mode Mode for O_{CREAT,TMPFILE}
  * @param resolve RESOLVE_* flags
diff --git a/src/libutil/include/nix/util/file-system.hh b/src/libutil/include/nix/util/file-system.hh
index 6fd30196213..310daa01efe 100644
--- a/src/libutil/include/nix/util/file-system.hh
+++ b/src/libutil/include/nix/util/file-system.hh
@@ -189,21 +189,19 @@ Path readLink(const Path & path);
  */
 std::filesystem::path readLink(const std::filesystem::path & path);
 
-#ifdef _WIN32
-namespace windows {
-
 /**
- * Get the path associated with a file handle.
+ * Get the path associated with a file descriptor.
  *
  * @note One MUST only use this for error handling, because it creates
  * TOCTOU issues. We don't mind if error messages point to out of date
  * paths (that is a rather trivial TOCTOU --- the error message is best
  * effort) but for anything else we do.
+ *
+ * @note this function will clobber `errno` (Unix) / "last error"
+ * (Windows), so care must be used to get those error codes, then call
+ * this, then build a `SysError` / `WinError` with the saved error code.
  */
-std::filesystem::path handleToPath(Descriptor handle);
-
-} // namespace windows
-#endif
+std::filesystem::path descriptorToPath(Descriptor fd);
 
 /**
  * Open a `Descriptor` with read-only access to the given directory.
diff --git a/src/libutil/posix-source-accessor.cc b/src/libutil/posix-source-accessor.cc
index 6b21696f024..bc3af9c0288 100644
--- a/src/libutil/posix-source-accessor.cc
+++ b/src/libutil/posix-source-accessor.cc
@@ -170,7 +170,7 @@ SourceAccessor::DirEntries PosixSourceAccessor::readDirectory(const CanonPath &
                 if (e.code() == std::errc::permission_denied || e.code() == std::errc::operation_not_permitted)
                     return std::nullopt;
                 else
-                    throw;
+                    throw SystemError(e.code(), "getting status of '%s'", PathFmt(entry.path()));
             }
         }();
         res.emplace(entry.path().filename().string(), type);
diff --git a/src/libutil/unix/file-descriptor.cc b/src/libutil/unix/file-descriptor.cc
index ec01f337de9..86177d01bef 100644
--- a/src/libutil/unix/file-descriptor.cc
+++ b/src/libutil/unix/file-descriptor.cc
@@ -49,7 +49,8 @@ void readFull(int fd, char * buf, size_t count)
                 pollFD(fd, POLLIN);
                 continue;
             }
-            throw SysError("reading from file");
+            auto savedErrno = errno;
+            throw SysError(savedErrno, "reading from file %s", PathFmt(descriptorToPath(fd)));
         }
         if (res == 0)
             throw EndOfFile("unexpected end-of-file");
@@ -72,7 +73,8 @@ void writeFull(int fd, std::string_view s, bool allowInterrupts)
                 pollFD(fd, POLLOUT);
                 continue;
             }
-            throw SysError("writing to file");
+            auto savedErrno = errno;
+            throw SysError(savedErrno, "writing to file %s", PathFmt(descriptorToPath(fd)));
         }
         if (res > 0)
             s.remove_prefix(res);
@@ -95,8 +97,10 @@ std::string readLine(int fd, bool eofOk, char terminator)
                 pollFD(fd, POLLIN);
                 continue;
             }
-            default:
-                throw SysError("reading a line");
+            default: {
+                auto savedErrno = errno;
+                throw SysError(savedErrno, "reading a line from %s", PathFmt(descriptorToPath(fd)));
+            }
             }
         } else if (rd == 0) {
             if (eofOk)
diff --git a/src/libutil/unix/file-system-at.cc b/src/libutil/unix/file-system-at.cc
index 866cdd31ced..85c90f6972d 100644
--- a/src/libutil/unix/file-system-at.cc
+++ b/src/libutil/unix/file-system-at.cc
@@ -71,8 +71,10 @@ void unix::fchmodatTryNoFollow(Descriptor dirFd, const CanonPath & path, mode_t
         if (res < 0) {
             if (errno == ENOSYS)
                 fchmodat2Unsupported.test_and_set();
-            else
-                throw SysError("fchmodat2 '%s' relative to parent directory", path.rel());
+            else {
+                auto savedErrno = errno;
+                throw SysError(savedErrno, "fchmodat2 %s", PathFmt(descriptorToPath(dirFd) / path.rel()));
+            }
         } else
             return;
     }
@@ -80,10 +82,13 @@ void unix::fchmodatTryNoFollow(Descriptor dirFd, const CanonPath & path, mode_t
 
 #ifdef __linux__
     AutoCloseFD pathFd = ::openat(dirFd, path.rel_c_str(), O_PATH | O_NOFOLLOW | O_CLOEXEC);
-    if (!pathFd)
+    if (!pathFd) {
+        auto savedErrno = errno;
         throw SysError(
-            "opening '%s' relative to parent directory to get an O_PATH file descriptor (fchmodat2 is unsupported)",
-            path.rel());
+            savedErrno,
+            "opening %s to get an O_PATH file descriptor (fchmodat2 is unsupported)",
+            PathFmt(descriptorToPath(dirFd) / path.rel()));
+    }
 
     struct ::stat st;
     /* Possible since https://github.com/torvalds/linux/commit/55815f70147dcfa3ead5738fd56d3574e2e3c1c2 (3.6) */
@@ -91,7 +96,7 @@ void unix::fchmodatTryNoFollow(Descriptor dirFd, const CanonPath & path, mode_t
         throw SysError("statting '%s' relative to parent directory via O_PATH file descriptor", path.rel());
 
     if (S_ISLNK(st.st_mode))
-        throw SysError(EOPNOTSUPP, "can't change mode of symlink '%s' relative to parent directory", path.rel());
+        throw SysError(EOPNOTSUPP, "can't change mode of symlink %s", PathFmt(descriptorToPath(dirFd) / path.rel()));
 
     static std::atomic_flag dontHaveProc{};
     if (!dontHaveProc.test()) {
@@ -101,8 +106,11 @@ void unix::fchmodatTryNoFollow(Descriptor dirFd, const CanonPath & path, mode_t
         if (int res = ::chmod(selfProcFdPath.c_str(), mode); res == -1) {
             if (errno == ENOENT)
                 dontHaveProc.test_and_set();
-            else
-                throw SysError("chmod '%s' ('%s' relative to parent directory)", selfProcFdPath, path);
+            else {
+                auto savedErrno = errno;
+                throw SysError(
+                    savedErrno, "chmod %s (%s)", selfProcFdPath, PathFmt(descriptorToPath(dirFd) / path.rel()));
+            }
         } else
             return;
     }
@@ -122,8 +130,10 @@ void unix::fchmodatTryNoFollow(Descriptor dirFd, const CanonPath & path, mode_t
 #endif
     );
 
-    if (res == -1)
-        throw SysError("fchmodat '%s' relative to parent directory", path.rel());
+    if (res == -1) {
+        auto savedErrno = errno;
+        throw SysError(savedErrno, "fchmodat %s", PathFmt(descriptorToPath(dirFd) / path.rel()));
+    }
 }
 
 static Descriptor
@@ -206,9 +216,10 @@ OsString readLinkAt(Descriptor dirFd, const CanonPath & path)
         checkInterrupt();
         buf.resize(bufSize);
         ssize_t rlSize = ::readlinkat(dirFd, path.rel_c_str(), buf.data(), bufSize);
-        if (rlSize == -1)
-            throw SysError("reading symbolic link '%1%' relative to parent directory", path.rel());
-        else if (rlSize < bufSize)
+        if (rlSize == -1) {
+            auto savedErrno = errno;
+            throw SysError(savedErrno, "reading symbolic link %1%", PathFmt(descriptorToPath(dirFd) / path.rel()));
+        } else if (rlSize < bufSize)
             return {buf.data(), static_cast<std::size_t>(rlSize)};
     }
 }
diff --git a/src/libutil/unix/file-system.cc b/src/libutil/unix/file-system.cc
index d3b6cbe28a3..3598bc8dee7 100644
--- a/src/libutil/unix/file-system.cc
+++ b/src/libutil/unix/file-system.cc
@@ -46,6 +46,31 @@ Descriptor openNewFileForWrite(const std::filesystem::path & path, mode_t mode,
     return open(path.c_str(), flags, mode);
 }
 
+std::filesystem::path descriptorToPath(Descriptor fd)
+{
+    if (fd == STDIN_FILENO)
+        return "<stdin>";
+    if (fd == STDOUT_FILENO)
+        return "<stdout>";
+    if (fd == STDERR_FILENO)
+        return "<stderr>";
+
+#if defined(__linux__)
+    try {
+        return readLink("/proc/self/fd/" + std::to_string(fd));
+    } catch (SystemError &) {
+    }
+#elif HAVE_F_GETPATH
+    /* F_GETPATH requires PATH_MAX buffer per POSIX */
+    char buf[PATH_MAX];
+    if (fcntl(fd, F_GETPATH, buf) != -1)
+        return buf;
+#endif
+
+    /* Fallback for unknown fd or unsupported platform */
+    return "<fd " + std::to_string(fd) + ">";
+}
+
 std::filesystem::path defaultTempDir()
 {
     return getEnvNonEmpty("TMPDIR").value_or("/tmp");
diff --git a/src/libutil/unix/meson.build b/src/libutil/unix/meson.build
index e59b4b6386d..7859707fe88 100644
--- a/src/libutil/unix/meson.build
+++ b/src/libutil/unix/meson.build
@@ -8,6 +8,12 @@ configdata_unix.set(
   description : 'Optionally used for changing the files and symlinks.',
 )
 
+configdata_unix.set(
+  'HAVE_F_GETPATH',
+  cxx.has_header_symbol('fcntl.h', 'F_GETPATH').to_int(),
+  description : 'Optionally used for getting the path of a file descriptor (macOS).',
+)
+
 # Check for each of these functions, and create a define like `#define
 # HAVE_CLOSE_RANGE 1`.
 check_funcs_unix = [
diff --git a/src/libutil/windows/file-descriptor.cc b/src/libutil/windows/file-descriptor.cc
index bd50e40be79..44a13cc9154 100644
--- a/src/libutil/windows/file-descriptor.cc
+++ b/src/libutil/windows/file-descriptor.cc
@@ -45,9 +45,9 @@ void writeFull(HANDLE handle, std::string_view s, bool allowInterrupts)
             checkInterrupt();
         DWORD res;
         if (!WriteFile(handle, s.data(), s.size(), &res, NULL)) {
-            // Do this because `handleToPath` will overwrite the last error.
+            // Do this because `descriptorToPath` will overwrite the last error.
             auto lastError = GetLastError();
-            auto path = handleToPath(handle);
+            auto path = descriptorToPath(handle);
             throw WinError(lastError, "writing to file %d:%s", handle, PathFmt(path));
         }
         if (res > 0)
diff --git a/src/libutil/windows/file-system-at.cc b/src/libutil/windows/file-system-at.cc
index 4e012bb0867..db4a3b0d663 100644
--- a/src/libutil/windows/file-system-at.cc
+++ b/src/libutil/windows/file-system-at.cc
@@ -156,13 +156,13 @@ OsString readSymlinkTarget(HANDLE linkHandle)
     size_t path_buf_offset = offsetof(ReparseDataBuffer, SymbolicLinkReparseBuffer.PathBuffer[0]);
 
     if (out < path_buf_offset) {
-        auto fullPath = handleToPath(linkHandle);
+        auto fullPath = descriptorToPath(linkHandle);
         throw WinError(
             DWORD{ERROR_REPARSE_TAG_INVALID}, "invalid reparse data for %d:%s", linkHandle, PathFmt(fullPath));
     }
 
     if (reparse->ReparseTag != IO_REPARSE_TAG_SYMLINK) {
-        auto fullPath = handleToPath(linkHandle);
+        auto fullPath = descriptorToPath(linkHandle);
         throw WinError(DWORD{ERROR_REPARSE_TAG_INVALID}, "not a symlink: %d:%s", linkHandle, PathFmt(fullPath));
     }
 
@@ -179,7 +179,7 @@ OsString readSymlinkTarget(HANDLE linkHandle)
     }
 
     if (path_buf_offset + name_offset + name_length > out) {
-        auto fullPath = handleToPath(linkHandle);
+        auto fullPath = descriptorToPath(linkHandle);
         throw WinError(
             DWORD{ERROR_REPARSE_TAG_INVALID}, "invalid symlink data for %d:%s", linkHandle, PathFmt(fullPath));
     }
diff --git a/src/libutil/windows/file-system.cc b/src/libutil/windows/file-system.cc
index e3b74fe392f..5b770e60a23 100644
--- a/src/libutil/windows/file-system.cc
+++ b/src/libutil/windows/file-system.cc
@@ -83,7 +83,7 @@ void deletePath(const std::filesystem::path & path, uint64_t & bytesFreed)
     deletePath(path);
 }
 
-std::filesystem::path windows::handleToPath(HANDLE handle)
+std::filesystem::path descriptorToPath(Descriptor handle)
 {
     std::vector<wchar_t> buf(0x100);
     DWORD dw = GetFinalPathNameByHandleW(handle, buf.data(), buf.size(), FILE_NAME_OPENED);
diff --git a/src/nix/nix-collect-garbage/nix-collect-garbage.cc b/src/nix/nix-collect-garbage/nix-collect-garbage.cc
index ec6ede80c2b..88fbc9db0e2 100644
--- a/src/nix/nix-collect-garbage/nix-collect-garbage.cc
+++ b/src/nix/nix-collect-garbage/nix-collect-garbage.cc
@@ -43,8 +43,8 @@ void removeOldGenerations(std::filesystem::path dir)
             std::string link;
             try {
                 link = readLink(path);
-            } catch (std::filesystem::filesystem_error & e) {
-                if (e.code() == std::errc::no_such_file_or_directory)
+            } catch (SystemError & e) {
+                if (e.is(std::errc::no_such_file_or_directory))
                     continue;
                 throw;
             }
diff --git a/src/nix/nix-env/nix-env.cc b/src/nix/nix-env/nix-env.cc
index 4a46e7ca65b..18bb2c74a03 100644
--- a/src/nix/nix-env/nix-env.cc
+++ b/src/nix/nix-env/nix-env.cc
@@ -1419,7 +1419,6 @@ static int main_nix_env(int argc, char ** argv)
                 replaceSymlink(defaultChannelsDir(profilesDirOpts), nixExprPath / "channels");
                 if (!isRootUser())
                     replaceSymlink(rootChannelsDir(profilesDirOpts), nixExprPath / "channels_root");
-            } catch (std::filesystem::filesystem_error &) {
             } catch (Error &) {
             }
         }