diff --git a/src/IlluminaRunFolder.php b/src/IlluminaRunFolder.php
index 6e9c73a..6875d62 100644
--- a/src/IlluminaRunFolder.php
+++ b/src/IlluminaRunFolder.php
@@ -2,21 +2,27 @@
 
 namespace MLL\Utils;
 
-use Carbon\CarbonImmutable;
+use Carbon\Carbon;
 
 use function Safe\preg_match;
 
+/**
+ * Parses Illumina sequencer run folder names (YYYYMMDD_InstrumentID_RunNumber_FlowcellSegment).
+ */
 class IlluminaRunFolder
 {
-    public CarbonImmutable $date;
+    private const FLOWCELL_ID_PATTERN = '/\d*-?([A-Z].+)$/';
+
+    public Carbon $date;
 
     public string $instrumentID;
 
     public int $runNumber;
 
+    /** Strips optional zero-prefix from raw segment: 000000000-AGKG7 → AGKG7. */
     public string $flowcellID;
 
-    public function __construct(CarbonImmutable $date, string $instrumentID, int $runNumber, string $flowcellID)
+    public function __construct(Carbon $date, string $instrumentID, int $runNumber, string $flowcellID)
     {
         $this->date = $date;
         $this->instrumentID = $instrumentID;
@@ -24,40 +30,43 @@ public function __construct(CarbonImmutable $date, string $instrumentID, int $ru
         $this->flowcellID = $flowcellID;
     }
 
-    /** @example IlluminaRunFolder::parse('/path/to/20260205_SH01038_0007_ASC2139476-SC3') */
+    /**
+     * Accepts both bare folder names and paths with forward or backslashes.
+     *
+     * @example IlluminaRunFolder::parse('foo\bar\260310_M02074_1219_000000000-MB4RJ')
+     * @example IlluminaRunFolder::parse('/path/to/20260205_SH01038_0007_ASC2139476-SC3')
+     */
     public static function parse(string $runFolder): self
     {
-        $folderName = basename($runFolder);
+        // Normalize backslashes so basename() works on Linux with Windows-style paths
+        $normalized = str_replace('\\', '/', $runFolder);
+        $folderName = basename($normalized);
+
         $parts = explode('_', $folderName, 4);
         if (count($parts) !== 4) {
             throw new \InvalidArgumentException("Invalid run folder format: {$runFolder}. Expected format: YYYYMMDD_InstrumentID_RunNumber_FlowcellID.");
         }
 
-        [$dateString, $instrumentID, $runNumberString, $flowcellID] = $parts;
+        [$dateString, $instrumentID, $runNumberString, $flowcellSegment] = $parts;
 
-        if (preg_match('/^\d{8}$/', $dateString) === 0) {
-            throw new \InvalidArgumentException("Invalid date in run folder: {$dateString}. Expected format: YYYYMMDD.");
+        if (preg_match('/^(\d{6}|\d{8})$/', $dateString) === 0) {
+            throw new \InvalidArgumentException("Invalid date in run folder: {$dateString}. Expected 6 or 8 digit date.");
         }
 
-        $date = CarbonImmutable::createFromFormat('!Ymd', $dateString);
-        if (! $date instanceof \Carbon\CarbonImmutable) {
-            throw new \InvalidArgumentException("Invalid date in run folder: {$dateString}. Expected format: YYYYMMDD.");
+        $format = strlen($dateString) === 8 ? '!Ymd' : '!ymd';
+        $date = Carbon::createFromFormat($format, $dateString);
+        if (! $date instanceof Carbon) {
+            throw new \InvalidArgumentException("Invalid date in run folder: {$dateString}.");
         }
 
         if ($runNumberString === '' || ! ctype_digit($runNumberString)) {
             throw new \InvalidArgumentException("Invalid run number in run folder: {$runNumberString}. Expected a numeric value.");
         }
 
-        return new self($date, $instrumentID, (int) $runNumberString, $flowcellID);
-    }
+        if (preg_match(self::FLOWCELL_ID_PATTERN, $flowcellSegment, $matches) !== 1) {
+            throw new \InvalidArgumentException("Cannot extract flowcell ID from: {$flowcellSegment}");
+        }
 
-    public function toString(): string
-    {
-        return implode('_', [
-            $this->date->format('Ymd'),
-            $this->instrumentID,
-            str_pad((string) $this->runNumber, 4, '0', STR_PAD_LEFT),
-            $this->flowcellID,
-        ]);
+        return new self($date, $instrumentID, (int) $runNumberString, $matches[1]);
     }
 }
diff --git a/tests/IlluminaRunFolderTest.php b/tests/IlluminaRunFolderTest.php
index 03a80bf..20d3d85 100644
--- a/tests/IlluminaRunFolderTest.php
+++ b/tests/IlluminaRunFolderTest.php
@@ -1,12 +1,14 @@
 <?php declare(strict_types=1);
 
+namespace MLL\Utils\Tests;
+
 use MLL\Utils\IlluminaRunFolder;
 use PHPUnit\Framework\Attributes\DataProvider;
 use PHPUnit\Framework\TestCase;
 
 final class IlluminaRunFolderTest extends TestCase
 {
-    public function testParse(): void
+    public function testParseMiSeqI100(): void
     {
         $folder = IlluminaRunFolder::parse('20260205_SH01038_0007_ASC2139476-SC3');
 
@@ -16,21 +18,56 @@ public function testParse(): void
         self::assertSame('ASC2139476-SC3', $folder->flowcellID);
     }
 
-    public function testParseFromPath(): void
+    public function testParseMiSeqWithZeroPrefixedFlowcell(): void
     {
-        $folder = IlluminaRunFolder::parse('/data/sequencing/20260205_SH01038_0007_ASC2139476-SC3');
+        $folder = IlluminaRunFolder::parse('151231_M01261_0163_000000000-AGKG7');
+
+        self::assertSame('2015-12-31', $folder->date->format('Y-m-d'));
+        self::assertSame('M01261', $folder->instrumentID);
+        self::assertSame(163, $folder->runNumber);
+        self::assertSame('AGKG7', $folder->flowcellID);
+    }
+
+    public function testParseNextSeq(): void
+    {
+        $folder = IlluminaRunFolder::parse('160205_NB501352_0003_AH7LFFAFXX');
+
+        self::assertSame('2016-02-05', $folder->date->format('Y-m-d'));
+        self::assertSame('NB501352', $folder->instrumentID);
+        self::assertSame(3, $folder->runNumber);
+        self::assertSame('AH7LFFAFXX', $folder->flowcellID);
+    }
+
+    public function testParseMiSeqNanoFlowcell(): void
+    {
+        $folder = IlluminaRunFolder::parse('160315_M01111_0231_000000000-D0WDA');
+
+        self::assertSame('D0WDA', $folder->flowcellID);
+    }
+
+    public function testParseFlowcellStartingWithL(): void
+    {
+        $folder = IlluminaRunFolder::parse('231013_M02074_0918_000000000-L6G7G');
+
+        self::assertSame('L6G7G', $folder->flowcellID);
+    }
+
+    public function testParseFromForwardSlashPath(): void
+    {
+        $folder = IlluminaRunFolder::parse('/path/to/20260205_SH01038_0007_ASC2139476-SC3');
 
-        self::assertSame('2026-02-05', $folder->date->format('Y-m-d'));
         self::assertSame('SH01038', $folder->instrumentID);
-        self::assertSame(7, $folder->runNumber);
         self::assertSame('ASC2139476-SC3', $folder->flowcellID);
     }
 
-    public function testToString(): void
+    public function testParseFromBackslashPath(): void
     {
-        $folder = IlluminaRunFolder::parse('20260205_SH01038_0007_ASC2139476-SC3');
+        $folder = IlluminaRunFolder::parse('foo\bar\260310_M02074_1219_000000000-MB4RJ');
 
-        self::assertSame('20260205_SH01038_0007_ASC2139476-SC3', $folder->toString());
+        self::assertSame('2026-03-10', $folder->date->format('Y-m-d'));
+        self::assertSame('M02074', $folder->instrumentID);
+        self::assertSame(1219, $folder->runNumber);
+        self::assertSame('MB4RJ', $folder->flowcellID);
     }
 
     public function testParseRejectsInvalidPartCount(): void
@@ -43,7 +80,7 @@ public function testParseRejectsInvalidPartCount(): void
     public function testParseRejectsInvalidDate(): void
     {
         self::expectException(\InvalidArgumentException::class);
-        self::expectExceptionMessage('Expected format: YYYYMMDD.');
+        self::expectExceptionMessage('Expected 6 or 8 digit date.');
         IlluminaRunFolder::parse('not-a-date_SH01038_0007_ASC2139476-SC3');
     }
 
@@ -62,4 +99,11 @@ public function testParseRejectsInvalidRunNumber(string $value): void
         self::expectExceptionMessage('Expected a numeric value.');
         IlluminaRunFolder::parse($value);
     }
+
+    public function testParseRejectsUnparsableFlowcellID(): void
+    {
+        self::expectException(\InvalidArgumentException::class);
+        self::expectExceptionMessage('Cannot extract flowcell ID from: 12345');
+        IlluminaRunFolder::parse('20260205_SH01038_0007_12345');
+    }
 }