diff --git a/composer.json b/composer.json
index c2008b020..72bcda2f3 100644
--- a/composer.json
+++ b/composer.json
@@ -22,6 +22,7 @@
         "rector/rector": "^2.3.2",
         "shipmonk/composer-dependency-analyser": "^1.8",
         "symplify/easy-coding-standard": "^13.0",
+        "symplify/phpstan-extensions": "^12.0",
         "tomasvotruba/class-leak": "^2.1",
         "tracy/tracy": "^2.10"
     },
diff --git a/phpstan.neon b/phpstan.neon
index 80b10f296..52a865ef1 100644
--- a/phpstan.neon
+++ b/phpstan.neon
@@ -1,6 +1,8 @@
 parameters:
     level: 8
 
+    errorFormat: symplify
+
     paths:
         - bin
         - src
diff --git a/src/Analyzer/DuplicatedScenarioTitlesAnalyzer.php b/src/Analyzer/DuplicatedScenarioTitlesAnalyzer.php
index 7bfc74db7..378cfa516 100644
--- a/src/Analyzer/DuplicatedScenarioTitlesAnalyzer.php
+++ b/src/Analyzer/DuplicatedScenarioTitlesAnalyzer.php
@@ -33,6 +33,6 @@ public function analyze(array $featureFiles): array
             }
         }
 
-        return array_filter($scenarioNamesToFiles, fn(array $files): bool => count($files) > 1);
+        return array_filter($scenarioNamesToFiles, fn (array $files): bool => count($files) > 1);
     }
 }
diff --git a/src/DefinitionPatternsExtractor.php b/src/DefinitionPatternsExtractor.php
index 8fd384ff1..14ef119f0 100644
--- a/src/DefinitionPatternsExtractor.php
+++ b/src/DefinitionPatternsExtractor.php
@@ -36,6 +36,8 @@ public function __construct(
      */
     public function extract(array $contextFiles): PatternCollection
     {
+        Assert::allIsInstanceOf($contextFiles, SplFileInfo::class);
+
         foreach ($contextFiles as $contextFile) {
             Assert::endsWith($contextFile->getFilename(), '.php');
         }
diff --git a/src/Enum/RuleIdentifier.php b/src/Enum/RuleIdentifier.php
index 3f89a4dd8..a20b78780 100644
--- a/src/Enum/RuleIdentifier.php
+++ b/src/Enum/RuleIdentifier.php
@@ -13,4 +13,6 @@ final class RuleIdentifier
     public const string DUPLICATED_PATTERNS = 'duplicated-patterns';
 
     public const string UNUSED_DEFINITIONS = 'unused-definitions';
+
+    public const string MISSING_CONTEXT_DEFINITIONS = 'missing-context-definitions';
 }
diff --git a/src/Rule/MissingContextDefinitionsRule.php b/src/Rule/MissingContextDefinitionsRule.php
new file mode 100644
index 000000000..1bce94b98
--- /dev/null
+++ b/src/Rule/MissingContextDefinitionsRule.php
@@ -0,0 +1,160 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Rector\Behastan\Rule;
+
+use Behat\Config\Config;
+use Rector\Behastan\Contract\RuleInterface;
+use Rector\Behastan\DefinitionPatternsExtractor;
+use Rector\Behastan\Enum\RuleIdentifier;
+use Rector\Behastan\Finder\BehatMetafilesFinder;
+use Rector\Behastan\UsedInstructionResolver;
+use Rector\Behastan\ValueObject\Pattern\NamedPattern;
+use Rector\Behastan\ValueObject\PatternCollection;
+use Rector\Behastan\ValueObject\RuleError;
+use Symfony\Component\Finder\SplFileInfo;
+use Webmozart\Assert\Assert;
+
+// WIP
+/**
+ * @todo extract service and test heavily
+ */
+final readonly class MissingContextDefinitionsRule implements RuleInterface
+{
+    public function __construct(
+        private UsedInstructionResolver $usedInstructionResolver,
+        private DefinitionPatternsExtractor $definitionPatternsExtractor,
+    ) {
+    }
+
+    /**
+     * @param SplFileInfo[] $contextFiles
+     * @param SplFileInfo[] $featureFiles
+     *
+     * @return RuleError[]
+     */
+    public function process(
+        array $contextFiles,
+        array $featureFiles,
+        PatternCollection $patternCollection,
+        string $projectDirectory
+    ): array {
+        $behatConfigFile = getcwd() . '/behat.php';
+
+        // nothing to analyse
+        if (! file_exists($behatConfigFile)) {
+            return [];
+        }
+
+        /** @var Config $behatConfiguration */
+        $behatConfiguration = require_once $behatConfigFile;
+
+        $suites = $behatConfiguration->toArray()['profile']['suites'] ?? [];
+
+        // most likely a bug, as at least one suite is expected
+        if ($suites === []) {
+            return [];
+        }
+
+        $featureInstructionsWithoutDefinitions = [];
+
+        foreach ($suites as $suiteName => $suiteConfiguration) {
+            // 1. find definitions in paths
+            $suiteFeatureFiles = BehatMetafilesFinder::findFeatureFiles($suiteConfiguration['paths']);
+            Assert::notEmpty($suiteFeatureFiles);
+
+            $suiteContextFilePaths = $this->resolveClassesFilePaths($suiteConfiguration['contexts']);
+            Assert::notEmpty($suiteContextFilePaths);
+
+            $suiteFeatureInstructions = $this->usedInstructionResolver->resolveInstructionsFromFeatureFiles(
+                $suiteFeatureFiles
+            );
+
+            // feature-used instructions
+            Assert::notEmpty($suiteFeatureInstructions);
+
+            // definitions-provided instructions
+            $suitePatternCollection = $this->definitionPatternsExtractor->extract($suiteContextFilePaths);
+
+            $featureInstructionsWithoutDefinitions = [];
+            foreach ($suiteFeatureInstructions as $featureInstruction) {
+                if ($this->isFeatureFoundInDefinitionPatterns($featureInstruction, $suitePatternCollection)) {
+                    continue;
+                }
+
+                $featureInstructionsWithoutDefinitions[$suiteName][] = $featureInstruction;
+            }
+        }
+
+        $ruleErrors = [];
+        foreach ($featureInstructionsWithoutDefinitions as $suiteName => $featureInstructions) {
+            // WIP @todo
+            $ruleErrors[] = new RuleError(
+                sprintf(
+                    'Suite %s is missing Context definitions for %d feature instructions: %s',
+                    $suiteName,
+                    count($featureInstructions),
+                    implode(PHP_EOL . ' * ', $featureInstructions)
+                ),
+                [],
+                $this->getIdentifier()
+            );
+        }
+
+        return $ruleErrors;
+    }
+
+    public function getIdentifier(): string
+    {
+        return RuleIdentifier::MISSING_CONTEXT_DEFINITIONS;
+    }
+
+    /**
+     * @param class-string[] $contextClasses
+     * @return SplFileInfo[]
+     */
+    private function resolveClassesFilePaths(array $contextClasses): array
+    {
+        $contextFilePaths = [];
+
+        foreach ($contextClasses as $contextClass) {
+            $reflectionClass = new \ReflectionClass($contextClass);
+            $fileName = $reflectionClass->getFileName();
+            if ($fileName === false) {
+                continue;
+            }
+
+            $contextFilePaths[] = new SplFileInfo($fileName, '', '');
+        }
+
+        return $contextFilePaths;
+    }
+
+    private function isFeatureFoundInDefinitionPatterns(
+        string $featureInstruction,
+        PatternCollection $suitePatternCollection
+    ): bool {
+        // 1. is feature used in exact pattern?
+        if (in_array($featureInstruction, $suitePatternCollection->exactPatternStrings())) {
+            return true;
+        }
+
+        // 2. is feature used in named pattern?
+        $namedPatterns = $suitePatternCollection->byType(NamedPattern::class);
+        foreach ($namedPatterns as $namedPattern) {
+            if (\Nette\Utils\Strings::match($featureInstruction, $namedPattern->getRegexPattern())) {
+                return true;
+            }
+        }
+
+        // 3. is feature used in regex pattern?
+        foreach ($suitePatternCollection->regexPatternsStrings() as $regexPatternString) {
+            if (\Nette\Utils\Strings::match($featureInstruction, $regexPatternString)) {
+                return true;
+            }
+        }
+
+        return false;
+    }
+}
diff --git a/src/ValueObject/Pattern/NamedPattern.php b/src/ValueObject/Pattern/NamedPattern.php
index f65f79b73..08677c30b 100644
--- a/src/ValueObject/Pattern/NamedPattern.php
+++ b/src/ValueObject/Pattern/NamedPattern.php
@@ -4,6 +4,14 @@
 
 namespace Rector\Behastan\ValueObject\Pattern;
 
+use Entropy\Utils\Regex;
+
 final class NamedPattern extends AbstractPattern
 {
+    private const string NAMED_MASK_REGEX = '#(\:[\W\w]+)#';
+
+    public function getRegexPattern(): string
+    {
+        return '#' . Regex::replace($this->pattern, self::NAMED_MASK_REGEX, '(.*?)') . '#';
+    }
 }
diff --git a/src/ValueObject/PatternCollection.php b/src/ValueObject/PatternCollection.php
index c3affacb5..89e065698 100644
--- a/src/ValueObject/PatternCollection.php
+++ b/src/ValueObject/PatternCollection.php
@@ -4,7 +4,6 @@
 
 namespace Rector\Behastan\ValueObject;
 
-use InvalidArgumentException;
 use Rector\Behastan\ValueObject\Pattern\AbstractPattern;
 use Rector\Behastan\ValueObject\Pattern\ExactPattern;
 use Rector\Behastan\ValueObject\Pattern\RegexPattern;
@@ -62,41 +61,17 @@ public function byType(string $type): array
         return array_filter($this->patterns, fn (AbstractPattern $pattern): bool => $pattern instanceof $type);
     }
 
-    public function regexPatternString(): string
-    {
-        $regexPatterns = $this->byType(RegexPattern::class);
-
-        $regexPatternStrings = array_map(
-            fn (RegexPattern $regexPattern): string => $regexPattern->pattern,
-            $regexPatterns
-        );
-
-        return $this->combineRegexes($regexPatternStrings, '#');
-    }
-
     /**
-     * @param string[] $regexes Like ['/foo/i', '~bar\d+~', '#baz#u']
+     * @return string[]
      */
-    private function combineRegexes(array $regexes, string $delimiter = '#'): string
+    public function regexPatternsStrings(): array
     {
-        $parts = [];
-
-        foreach ($regexes as $regex) {
-            // Very common case: regex is given like "/pattern/flags"
-            // Parse: delimiter + pattern + delimiter + flags
-            if (! preg_match('~^(.)(.*)\\1([a-zA-Z]*)$~s', $regex, $m)) {
-                throw new InvalidArgumentException('Invalid regex: ' . $regex);
-            }
-
-            $pattern = $m[2];
-            $flags = $m[3];
+        $regexPatterns = $this->byType(RegexPattern::class);
 
-            // If you truly have mixed flags per-regex, you can't naively merge them.
-            // Best practice: normalize flags beforehand (same for all).
-            // We'll ignore per-regex flags here and let the caller decide final flags.
-            $parts[] = '(?:' . $pattern . ')';
-        }
+        $regexPatternStrings = array_map(function (RegexPattern $regexPattern): string {
+            return $regexPattern->pattern;
+        }, $regexPatterns);
 
-        return $delimiter . '(?:' . implode('|', $parts) . ')' . $delimiter;
+        return array_values($regexPatternStrings);
     }
 }
diff --git a/stubs/Behat/Behat/Config.php b/stubs/Behat/Behat/Config.php
new file mode 100644
index 000000000..cc2390e04
--- /dev/null
+++ b/stubs/Behat/Behat/Config.php
@@ -0,0 +1,13 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Behat\Config;
+
+final class Config
+{
+    public function toArray(): array
+    {
+        return [];
+    }
+}
diff --git a/tests/ValueObject/PatternCollectionTest.php b/tests/ValueObject/PatternCollectionTest.php
index 1b3ab5d6b..8e76e95e8 100644
--- a/tests/ValueObject/PatternCollectionTest.php
+++ b/tests/ValueObject/PatternCollectionTest.php
@@ -31,7 +31,13 @@ public function testRegexPatterns(): void
             new RegexPattern('#here is more#', 'file1.php', 10, 'SomeClass', 'someMethod'),
         ]);
 
-        $this->assertSame('#(?:(?:this is it)|(?:here is more))#', $patternCollection->regexPatternString());
+        $this->assertSame(['#this is it#', '#here is more#'], $patternCollection->regexPatternsStrings());
+    }
+
+    public function testNamedPatterns(): void
+    {
+        $namedPattern = new NamedPattern('this is :me', 'file1.php', 10, 'SomeClass', 'someMethod');
 
+        $this->assertSame('#this is (.*?)#', $namedPattern->getRegexPattern());
     }
 }