diff --git a/lix/libmain/common-args.cc b/lix/libmain/common-args.cc
index ba2d3ee0c..0367c53cc 100644
--- a/lix/libmain/common-args.cc
+++ b/lix/libmain/common-args.cc
@@ -1,8 +1,8 @@
 #include "lix/libmain/common-args.hh"
 #include "lix/libutil/args/root.hh"
+#include "lix/libutil/config-impl.hh" // IWYU pragma: keep
 #include "lix/libutil/error.hh"
 #include "lix/libstore/globals.hh"
-#include "lix/libmain/loggers.hh"
 #include "lix/libutil/logging.hh"
 
 namespace nix {
@@ -62,7 +62,9 @@ MixCommonArgs::MixCommonArgs(const std::string & programName)
         .description = "Set the format of log output; one of `raw`, `internal-json`, `bar`, `bar-with-logs`, `multiline` or `multiline-with-logs`.",
         .category = loggingCategory,
         .labels = {"format"},
-        .handler = {[](std::string format) { setLogFormat(format); }},
+        .handler = {[&](std::string format) {
+            loggerSettings.logFormat.set(format);
+        }},
     });
 
     addFlag({
diff --git a/lix/libmain/loggers.cc b/lix/libmain/loggers.cc
index ff9a03360..12301c392 100644
--- a/lix/libmain/loggers.cc
+++ b/lix/libmain/loggers.cc
@@ -1,29 +1,17 @@
 #include "lix/libutil/environment-variables.hh"
 #include "lix/libmain/loggers.hh"
 #include "lix/libmain/progress-bar.hh"
+#include "lix/libutil/log-format.hh"
+#include "lix/libutil/config-impl.hh" // IWYU pragma: keep
 
 namespace nix {
 
-LogFormat defaultLogFormat = LogFormat::Auto;
-
-[[deprecated]]
-LogFormat parseLogFormat(const std::string & logFormatStr) {
-    if (auto const parsed = LogFormat::parse(logFormatStr)) {
-        return *parsed;
-    }
-    throw Error("setting 'log-format' has an invalid value '%s'", logFormatStr);
-}
-
-Logger * makeDefaultLogger() {
-    return getLoggerByFormat(defaultLogFormat);
-}
-
-void setLogFormat(const std::string & logFormatStr) {
-    setLogFormat(parseLogFormat(logFormatStr));
+static Logger * makeDefaultLogger() {
+    return getLoggerByFormat(loggerSettings.logFormat);
 }
 
 void setLogFormat(const LogFormat & logFormat) {
-    defaultLogFormat = logFormat;
+    loggerSettings.logFormat.override(logFormat);
     createDefaultLogger();
 }
 
@@ -36,7 +24,7 @@ Logger * getLoggerByFormat(LogFormat logFormat)
     using enum LogFormatValue;
     switch (logFormat) {
     case LogFormat::Auto:
-        return getLoggerByFormat(defaultLogFormat);
+        return getLoggerByFormat(loggerSettings.logFormat.autoValue);
     case LogFormat::Raw:
         return makeSimpleLogger(false);
     case LogFormat::RawWithLogs:
diff --git a/lix/libmain/loggers.hh b/lix/libmain/loggers.hh
index 33cf133ac..323a913b4 100644
--- a/lix/libmain/loggers.hh
+++ b/lix/libmain/loggers.hh
@@ -8,9 +8,7 @@ namespace nix {
 
 class Logger;
 
-[[deprecated]]
-void setLogFormat(const std::string & logFormatStr);
-[[deprecated]]
+/** Overrides the current log format, and re-creates the current logger. */
 void setLogFormat(const LogFormat & logFormat);
 
 void createDefaultLogger();
diff --git a/lix/libmain/shared.cc b/lix/libmain/shared.cc
index bcf8ea3e8..e2cba0663 100644
--- a/lix/libmain/shared.cc
+++ b/lix/libmain/shared.cc
@@ -200,7 +200,10 @@ LegacyArgs::LegacyArgs(AsyncIoRoot & aio, const std::string & programName,
         .longName = "no-build-output",
         .shortName = 'Q',
         .description = "Do not show build output.",
-        .handler = {[&]() {setLogFormat(LogFormat::Raw); }},
+        .handler = {[&]() {
+            loggerSettings.logFormat.setDefault(loggerSettings.logFormat.get().withoutLogs());
+            loggerSettings.logFormat.autoValue = loggerSettings.logFormat.get().withoutLogs();
+        }},
     });
 
     addFlag({
diff --git a/lix/libutil/config-impl.hh b/lix/libutil/config-impl.hh
index 9cdc5964b..d25ec5fd1 100644
--- a/lix/libutil/config-impl.hh
+++ b/lix/libutil/config-impl.hh
@@ -133,6 +133,7 @@ DECLARE_CONFIG_SERIALISER(StringSet)
 DECLARE_CONFIG_SERIALISER(StringMap)
 DECLARE_CONFIG_SERIALISER(ExperimentalFeatures)
 DECLARE_CONFIG_SERIALISER(DeprecatedFeatures)
+DECLARE_CONFIG_SERIALISER(LogFormat)
 
 template<typename T>
 T BaseSetting<T>::parse(const std::string & str, const ApplyConfigOptions & options) const
diff --git a/lix/libutil/log-format.cc b/lix/libutil/log-format.cc
index 6062cc203..dee1616d5 100644
--- a/lix/libutil/log-format.cc
+++ b/lix/libutil/log-format.cc
@@ -1,4 +1,48 @@
 #include "lix/libutil/log-format.hh"
 
+#include "lix/libutil/abstract-setting-to-json.hh" // IWYU pragma: keep
+#include "lix/libutil/json.hh"
+#include "lix/libutil/log-format.hh"
+
+#include <format>
+
+namespace nix {
+template<>
+std::string BaseSetting<LogFormat>::to_string() const
+{
+    return std::format("{}", value);
+}
+
+template<>
+LogFormat
+BaseSetting<LogFormat>::parse(const std::string & str, const ApplyConfigOptions & options) const
+{
+    if (auto const parsed = LogFormat::parse(str)) {
+        return *parsed;
+    }
+    throw UsageError("setting '%s' has invalid value '%s'", name, str);
+}
+
+void to_json(JSON & j, const LogFormat & self)
+{
+    j = std::format("{}", self);
+}
+
+void from_json(const JSON & j, LogFormat & self)
+{
+    std::string asStr = ensureType(j, JSON::value_t::string);
+    auto const parsed = LogFormat::parse(asStr);
+    if (!parsed) {
+        throw Error("invalid json for 'log-format': %s", j);
+    }
+    self = *parsed;
+}
+
+// Explicitly instantiate the non-specialized templates.
+// `abstract-setting-to-json.hh` is IWYU-kept so this line also instantiates that template.
+template class BaseSetting<LogFormat>;
+
+}
+
 static_assert(std::formattable<nix::LogFormat, char>);
 static_assert(std::formattable<nix::LogFormatValue, char>);
diff --git a/lix/libutil/log-format.hh b/lix/libutil/log-format.hh
index 79378d543..a35f951dd 100644
--- a/lix/libutil/log-format.hh
+++ b/lix/libutil/log-format.hh
@@ -1,6 +1,7 @@
 #pragma once
 ///@file
 
+#include "lix/libutil/config.hh"
 #include "lix/libutil/fmt.hh"
 #include "lix/libutil/json-fwd.hh"
 
@@ -156,6 +157,30 @@ struct json::is_integral_enum<nix::LogFormat> : std::true_type {};
 template<>
 struct json::is_integral_enum<nix::LogFormatValue> : std::true_type {};
 
+/** Note: you'll have to include `config-impl.hh` when you want to use methods from this type. */
+struct LogFormatSetting : public BaseSetting<LogFormat>
+{
+    // I hate global state, man.
+    LogFormat autoValue = LogFormat::RawWithLogs;
+
+    LogFormatSetting(
+        Config * options,
+        const LogFormat & def,
+        const std::string & name,
+        const std::string & description,
+        const std::set<std::string> & aliases = {},
+        bool documentDefault = true,
+        std::optional<ExperimentalFeature> experimentalFeature = std::nullopt,
+        bool deprecated = false
+    ) : BaseSetting<LogFormat>(def, true, name, description, aliases, experimentalFeature, deprecated)
+    {
+        options->addSetting(this);
+    }
+};
+
+void to_json(JSON & j, const LogFormat & self);
+void from_json(const JSON & j, LogFormat & self);
+
 }
 
 template<>
diff --git a/lix/libutil/logging-settings/log-format.md b/lix/libutil/logging-settings/log-format.md
new file mode 100644
index 000000000..b0e1b614f
--- /dev/null
+++ b/lix/libutil/logging-settings/log-format.md
@@ -0,0 +1,11 @@
+---
+name: log-format
+internalName: logFormat
+settingType: LogFormatSetting
+defaultExpr: 'LogFormat::Auto'
+defaultText: auto
+---
+Set the format of log output; one of `raw`, `internal-json`, `bar`, `bar-with-logs`, `multiline` or `multiline-with-logs`.
+
+For legacy reasons, the default value "auto" makes the actual log format depend on which command you're using.
+The legacy `nix-` CLI will use `raw-with-logs` (or `raw` with `-Q`/`--no-build-output`), and `nix3` commands will use `bar-with-logs`.
diff --git a/lix/libutil/logging.cc b/lix/libutil/logging.cc
index 45196cac8..57fe06787 100644
--- a/lix/libutil/logging.cc
+++ b/lix/libutil/logging.cc
@@ -1,4 +1,5 @@
 #include "c-calls.hh"
+#include "lix/libutil/config-impl.hh"
 #include "lix/libutil/environment-variables.hh"
 #include "lix/libutil/file-descriptor.hh"
 #include "lix/libutil/logging.hh"
diff --git a/lix/libutil/logging.hh b/lix/libutil/logging.hh
index 1da9d53bc..e37df0025 100644
--- a/lix/libutil/logging.hh
+++ b/lix/libutil/logging.hh
@@ -4,7 +4,7 @@
 #include "lix/libutil/types.hh"
 #include "lix/libutil/error.hh"
 #include "lix/libutil/config.hh"
-#include "lix/libutil/log-format.hh"
+#include "lix/libutil/log-format.hh" // IWYU pragma: keep
 #include "result.hh"
 #include "serialise.hh"
 #include <kj/async.h>
diff --git a/lix/libutil/meson.build b/lix/libutil/meson.build
index bbd766689..4b8334c73 100644
--- a/lix/libutil/meson.build
+++ b/lix/libutil/meson.build
@@ -282,7 +282,10 @@ libutil_settings_headers += custom_target(
 )
 
 logging_setting_definitions = files(
+  # keep-sorted start
+  'logging-settings/log-format.md',
   'logging-settings/show-trace.md',
+  # keep-sorted end
 )
 libutil_settings_headers += custom_target(
   command : [
diff --git a/lix/nix/main.cc b/lix/nix/main.cc
index 0798f1cdf..05f7ee3a8 100644
--- a/lix/nix/main.cc
+++ b/lix/nix/main.cc
@@ -228,7 +228,9 @@ struct NixArgs : virtual MultiCommand, virtual MixCommonArgs, virtual RootArgs
                 .shortName = 'L',
                 .description = "Print full build logs on standard error.",
                 .category = loggingCategory,
-                .handler = {[&]() { logger->setPrintBuildLogs(true); }},
+                .handler = {[&]() {
+                    loggerSettings.logFormat.setDefault(loggerSettings.logFormat.get().withLogs());
+                }},
                 .experimentalFeature = Xp::NixCommand,
             });
 
@@ -500,7 +502,7 @@ int mainWrapped(AsyncIoRoot & aio, int argc, char ** argv)
 
     evalSettings.pureEval.setDefault(true);
 
-    setLogFormat(LogFormat::BarWithLogs);
+    loggerSettings.logFormat.autoValue = LogFormat::BarWithLogs;
 
     // FIXME: stop messing about with log verbosity depending on if it is interactive use
     if (isatty(STDERR_FILENO)) {
@@ -578,6 +580,9 @@ int mainWrapped(AsyncIoRoot & aio, int argc, char ** argv)
         if (!args.helpRequested && !args.completions) throw;
     }
 
+    // HACK: after args.parseCmdline() we re-create the default logger, to apply --option flags.
+    createDefaultLogger();
+
     if (args.completions) {
         switch (args.completions->type) {
         case Completions::Type::Normal:
diff --git a/lix/nix/prefetch.cc b/lix/nix/prefetch.cc
index a3161263d..e5fd29919 100644
--- a/lix/nix/prefetch.cc
+++ b/lix/nix/prefetch.cc
@@ -188,8 +188,9 @@ static int main_nix_prefetch_url(AsyncIoRoot & aio, std::string programName, Str
         if (args.size() > 2)
             throw UsageError("too many arguments");
 
-        if (isOutputARealTerminal(StandardOutputStream::Stderr))
-            setLogFormat(LogFormat::Bar);
+        if (isOutputARealTerminal(StandardOutputStream::Stderr)) {
+            loggerSettings.logFormat.autoValue = LogFormat::Bar;
+        }
 
         auto store = aio.blockOn(openStore());
         auto evaluator = std::make_unique<Evaluator>(aio, myArgs.searchPath, store);
diff --git a/tests/functional2/cli/test_completions.py b/tests/functional2/cli/test_completions.py
index e9bded03f..0a3194d0a 100644
--- a/tests/functional2/cli/test_completions.py
+++ b/tests/functional2/cli/test_completions.py
@@ -131,9 +131,9 @@ def test_completions_flake_update(nix: Nix, files: Path):
 
 def test_flag_completion(nix: Nix):
     nix.env["NIX_GET_COMPLETIONS"] = "2"
-    res = nix.nix(["build", "--log-form"]).run().ok()
-    assert "--log-format" in res.stdout_plain
-    assert "Set the format of log output; one of" in res.stdout_plain
+    res = nix.nix(["build", "--dry"]).run().ok()
+    assert "--dry-run" in res.stdout_plain
+    assert "Show what this command would do without doing it" in res.stdout_plain
 
 
 def test_option_completion(nix: Nix):
diff --git a/tests/unit/libmain/progress-bar.cc b/tests/unit/libmain/progress-bar.cc
index 0862111e0..99ba991ea 100644
--- a/tests/unit/libmain/progress-bar.cc
+++ b/tests/unit/libmain/progress-bar.cc
@@ -3,6 +3,7 @@
 #include "lix/libexpr/eval.hh"
 #include "lix/libmain/progress-bar.hh"
 #include "lix/libmain/loggers.hh"
+#include "lix/libutil/config-impl.hh"
 #include "lix/libutil/logging.hh"
 #include "lix/libmain/shared.hh"