diff --git a/hwe/compare/turn_command_trace.php b/hwe/compare/turn_command_trace.php
new file mode 100644
index 00000000..f71dd6c6
--- /dev/null
+++ b/hwe/compare/turn_command_trace.php
@@ -0,0 +1,159 @@
+<?php
+
+declare(strict_types=1);
+
+namespace sammo;
+
+if (PHP_SAPI !== 'cli') {
+    http_response_code(404);
+    exit;
+}
+
+chdir(dirname(__DIR__));
+$_SERVER['REMOTE_ADDR'] ??= '127.0.0.1';
+error_reporting(E_ALL & ~E_DEPRECATED);
+require_once 'lib.php';
+require_once 'func.php';
+require_once __DIR__ . '/turn_state_snapshot.php';
+
+final class TurnComparisonTracingRNG implements RNG
+{
+    private int $sequence = 0;
+
+    /** @var list<array<string, mixed>> */
+    public array $calls = [];
+
+    public function __construct(private readonly RNG $inner)
+    {
+    }
+
+    public static function getMaxInt(): int
+    {
+        return LiteHashDRBG::getMaxInt();
+    }
+
+    public function nextBytes(int $bytes): string
+    {
+        $value = $this->inner->nextBytes($bytes);
+        $this->record('nextBytes', ['bytes' => $bytes], bin2hex($value));
+        return $value;
+    }
+
+    public function nextBits(int $bits): string
+    {
+        $value = $this->inner->nextBits($bits);
+        $this->record('nextBits', ['bits' => $bits], bin2hex($value));
+        return $value;
+    }
+
+    public function nextInt(?int $max = null): int
+    {
+        $value = $this->inner->nextInt($max);
+        $this->record('nextInt', ['maxInclusive' => $max], $value);
+        return $value;
+    }
+
+    public function nextFloat1(): float
+    {
+        $value = $this->inner->nextFloat1();
+        $this->record('nextFloat1', [], $value);
+        return $value;
+    }
+
+    private function record(string $operation, array $arguments, mixed $result): void
+    {
+        $this->calls[] = [
+            'seq' => $this->sequence++,
+            'operation' => $operation,
+            'arguments' => $arguments,
+            'result' => $result,
+        ];
+    }
+}
+
+function comparisonRunTurnCommand(array $request): array
+{
+    if (getenv('TURN_DIFFERENTIAL_ENABLED') !== '1') {
+        throw new \RuntimeException('TURN_DIFFERENTIAL_ENABLED=1 is required');
+    }
+    $kind = $request['kind'] ?? null;
+    if ($kind !== 'general' && $kind !== 'nation') {
+        throw new \InvalidArgumentException('kind must be general or nation');
+    }
+    $actorGeneralId = $request['actorGeneralId'] ?? null;
+    $action = $request['action'] ?? null;
+    $args = $request['args'] ?? null;
+    if (!is_int($actorGeneralId) || $actorGeneralId < 1) {
+        throw new \InvalidArgumentException('actorGeneralId must be a positive integer');
+    }
+    if (!is_string($action) || $action === '') {
+        throw new \InvalidArgumentException('action must be a non-empty string');
+    }
+
+    $snapshotRequest = ['observe' => $request['observe'] ?? []];
+    $before = comparisonTurnStateSnapshot($snapshotRequest);
+    $db = DB::db();
+    $gameStorage = KVStorage::getStorage($db, 'game_env');
+    $gameStorage->resetCache();
+    $environment = $gameStorage->getAll();
+    $general = General::createObjFromDB($actorGeneralId);
+    $turn = new TurnExecutionHelper($general);
+    $seedDomain = $kind === 'general' ? 'generalCommand' : 'nationCommand';
+    $seed = Util::simpleSerialize(
+        UniqueConst::$hiddenSeed,
+        $seedDomain,
+        (int)$environment['year'],
+        (int)$environment['month'],
+        $actorGeneralId,
+        $action,
+    );
+    $tracingRng = new TurnComparisonTracingRNG(new LiteHashDRBG($seed));
+    $rng = new RandUtil($tracingRng);
+
+    if ($kind === 'general') {
+        $command = buildGeneralCommandClass($action, $general, $environment, $args);
+        $resultTurn = $turn->processCommand($rng, $command, false);
+    } else {
+        $command = buildNationCommandClass($action, $general, $environment, $general->getLastTurn(), $args);
+        $resultTurn = $turn->processNationCommand($rng, $command);
+    }
+
+    $general->getLogger()->flush();
+    $turn->applyDB();
+    unset($turn);
+    $after = comparisonTurnStateSnapshot($snapshotRequest);
+
+    return [
+        'schemaVersion' => 1,
+        'engine' => 'ref',
+        'execution' => [
+            'kind' => $kind,
+            'actorGeneralId' => $actorGeneralId,
+            'action' => $action,
+            'args' => $args,
+            'seedDomain' => $seedDomain,
+            'outcome' => [
+                'lastTurn' => $resultTurn->toRaw(),
+                'commandName' => $command->getName(),
+            ],
+        ],
+        'before' => $before,
+        'after' => $after,
+        'rng' => $tracingRng->calls,
+    ];
+}
+
+try {
+    $input = stream_get_contents(STDIN);
+    $request = json_decode($input === '' ? '{}' : $input, true, flags: JSON_THROW_ON_ERROR);
+    if (!is_array($request)) {
+        throw new \InvalidArgumentException('request must be an object');
+    }
+    echo json_encode(
+        comparisonRunTurnCommand($request),
+        JSON_THROW_ON_ERROR | JSON_UNESCAPED_UNICODE | JSON_UNESCAPED_SLASHES | JSON_PRESERVE_ZERO_FRACTION,
+    ), PHP_EOL;
+} catch (\Throwable $throwable) {
+    fwrite(STDERR, $throwable::class . ': ' . $throwable->getMessage() . PHP_EOL);
+    exit(1);
+}
diff --git a/hwe/compare/turn_state_snapshot.php b/hwe/compare/turn_state_snapshot.php
index 3eb6af4a..ca562c9b 100644
--- a/hwe/compare/turn_state_snapshot.php
+++ b/hwe/compare/turn_state_snapshot.php
@@ -314,17 +314,24 @@ function comparisonTurnStateSnapshot(array $request): array
     ];
 }
 
-try {
-    $input = stream_get_contents(STDIN);
-    $request = json_decode($input === '' ? '{}' : $input, true, flags: JSON_THROW_ON_ERROR);
-    if (!is_array($request)) {
-        throw new \InvalidArgumentException('request must be an object');
+function comparisonTurnStateSnapshotMain(): void
+{
+    try {
+        $input = stream_get_contents(STDIN);
+        $request = json_decode($input === '' ? '{}' : $input, true, flags: JSON_THROW_ON_ERROR);
+        if (!is_array($request)) {
+            throw new \InvalidArgumentException('request must be an object');
+        }
+        echo json_encode(
+            comparisonTurnStateSnapshot($request),
+            JSON_THROW_ON_ERROR | JSON_UNESCAPED_UNICODE | JSON_UNESCAPED_SLASHES | JSON_PRESERVE_ZERO_FRACTION,
+        ), PHP_EOL;
+    } catch (\Throwable $throwable) {
+        fwrite(STDERR, $throwable::class . ': ' . $throwable->getMessage() . PHP_EOL);
+        exit(1);
     }
-    echo json_encode(
-        comparisonTurnStateSnapshot($request),
-        JSON_THROW_ON_ERROR | JSON_UNESCAPED_UNICODE | JSON_UNESCAPED_SLASHES | JSON_PRESERVE_ZERO_FRACTION,
-    ), PHP_EOL;
-} catch (\Throwable $throwable) {
-    fwrite(STDERR, $throwable::class . ': ' . $throwable->getMessage() . PHP_EOL);
-    exit(1);
+}
+
+if (realpath((string)($_SERVER['SCRIPT_FILENAME'] ?? '')) === __FILE__) {
+    comparisonTurnStateSnapshotMain();
 }