diff --git a/.github/workflows/e2e-tests.yml b/.github/workflows/e2e-tests.yml
index fac692020a3..4be574fcbc1 100644
--- a/.github/workflows/e2e-tests.yml
+++ b/.github/workflows/e2e-tests.yml
@@ -606,10 +606,27 @@ jobs:
               OUTPUT=$(../bashunit -a exit_code "0" "../../bin/phpstan analyse -vv")
               echo "$OUTPUT"
               ../bashunit -a contains 'Result cache restored. 0 files will be reanalysed.' "$OUTPUT"
+          - script: |
+              cd e2e/result-cache-dots-in-path
+              # scanFiles/bootstrapFiles/stubFiles built out of %rootDir% with a '..' segment in the
+              # middle: the placeholder keeps NeonAdapter from normalizing them when the Neon file is
+              # read, so nothing may compare that spelling against the normalized one.
+              ../../bin/phpstan analyse
+              OUTPUT=$(../bashunit -a exit_code "0" "../../bin/phpstan analyse -vv")
+              echo "$OUTPUT"
+              ../bashunit -a contains 'Result cache restored. 0 files will be reanalysed.' "$OUTPUT"
           - script: |
               cd e2e/result-cache-package-update
               composer install
               ../../bin/phpstan analyse
+              # Nothing changed at all: the cache must be reused without even reaching the
+              # changed-packages fallback. Composer spells install_path in installed.php with a '..'
+              # segment ('vendor/composer/../test/logger'), so a meta that is not canonicalized the
+              # same way it is restored reports composerInstalled as changed on every single run.
+              OUTPUT=$(../bashunit -a exit_code "0" "../../bin/phpstan analyse -vv")
+              echo "$OUTPUT"
+              ../bashunit -a not_contains 'Composer metadata changed' "$OUTPUT"
+              ../bashunit -a contains 'Result cache restored. 0 files will be reanalysed.' "$OUTPUT"
               # Update a single Composer package by bumping its version with a patch and letting Composer
               # reinstall it, which changes its recorded reference in vendor/composer/installed.php. The
               # cache must be invalidated only for files depending on that package (src/Foo.php uses
diff --git a/e2e/result-cache-dots-in-path/.gitignore b/e2e/result-cache-dots-in-path/.gitignore
new file mode 100644
index 00000000000..ceeb05b4108
--- /dev/null
+++ b/e2e/result-cache-dots-in-path/.gitignore
@@ -0,0 +1 @@
+/tmp
diff --git a/e2e/result-cache-dots-in-path/bootstrap.php b/e2e/result-cache-dots-in-path/bootstrap.php
new file mode 100644
index 00000000000..3c6b2651747
--- /dev/null
+++ b/e2e/result-cache-dots-in-path/bootstrap.php
@@ -0,0 +1 @@
+<?php declare(strict_types = 1);
diff --git a/e2e/result-cache-dots-in-path/phpstan.neon b/e2e/result-cache-dots-in-path/phpstan.neon
new file mode 100644
index 00000000000..8e5003e01e7
--- /dev/null
+++ b/e2e/result-cache-dots-in-path/phpstan.neon
@@ -0,0 +1,13 @@
+parameters:
+	level: 8
+	tmpDir: tmp
+	paths:
+		- src
+	# every one of these spells an existing file through a '..' segment - the placeholder keeps
+	# NeonAdapter from normalizing them when the file is read
+	scanFiles:
+		- %rootDir%/e2e/result-cache-dots-in-path/src/../scanned/ScannedGreeter.php
+	bootstrapFiles:
+		- %rootDir%/e2e/result-cache-dots-in-path/src/../bootstrap.php
+	stubFiles:
+		- %rootDir%/e2e/result-cache-dots-in-path/src/../stubs/ScannedGreeter.stub
diff --git a/e2e/result-cache-dots-in-path/scanned/ScannedGreeter.php b/e2e/result-cache-dots-in-path/scanned/ScannedGreeter.php
new file mode 100644
index 00000000000..a7fb3fc69e6
--- /dev/null
+++ b/e2e/result-cache-dots-in-path/scanned/ScannedGreeter.php
@@ -0,0 +1,13 @@
+<?php declare(strict_types = 1);
+
+namespace DotsInPathResultCache;
+
+class ScannedGreeter
+{
+
+	public function greet(string $name): string
+	{
+		return sprintf('Hello, %s', $name);
+	}
+
+}
diff --git a/e2e/result-cache-dots-in-path/src/HelloWorld.php b/e2e/result-cache-dots-in-path/src/HelloWorld.php
new file mode 100644
index 00000000000..5eeb695f99c
--- /dev/null
+++ b/e2e/result-cache-dots-in-path/src/HelloWorld.php
@@ -0,0 +1,14 @@
+<?php declare(strict_types = 1);
+
+namespace DotsInPathResultCache;
+
+class HelloWorld
+{
+
+	/** @return non-empty-string */
+	public function sayHello(): string
+	{
+		return (new ScannedGreeter())->greet('PHPStan');
+	}
+
+}
diff --git a/e2e/result-cache-dots-in-path/stubs/ScannedGreeter.stub b/e2e/result-cache-dots-in-path/stubs/ScannedGreeter.stub
new file mode 100644
index 00000000000..b0efc4f00ab
--- /dev/null
+++ b/e2e/result-cache-dots-in-path/stubs/ScannedGreeter.stub
@@ -0,0 +1,11 @@
+<?php
+
+namespace DotsInPathResultCache;
+
+class ScannedGreeter
+{
+
+	/** @return non-empty-string */
+	public function greet(string $name): string;
+
+}
diff --git a/src/Analyser/ResultCache/ResultCacheManager.php b/src/Analyser/ResultCache/ResultCacheManager.php
index 53407bed071..d4f78e65713 100644
--- a/src/Analyser/ResultCache/ResultCacheManager.php
+++ b/src/Analyser/ResultCache/ResultCacheManager.php
@@ -34,7 +34,6 @@
 use function array_filter;
 use function array_key_exists;
 use function array_keys;
-use function array_map;
 use function array_merge;
 use function array_unique;
 use function array_values;
@@ -70,7 +69,7 @@
 final class ResultCacheManager
 {
 
-	private const CACHE_VERSION = 'v14-relativePaths';
+	private const CACHE_VERSION = 'v15-canonicalPaths';
 
 	/** @var array<string, string> */
 	private array $fileHashes = [];
@@ -1588,7 +1587,12 @@ private function getMeta(array $allAnalysedFiles, ?array $projectConfigArray): a
 			ksort($projectConfigArray);
 		}
 
-		return [
+		// The meta is stored relativized and comes back absolutized, which also normalizes every path
+		// in it ('a/b/../c' becomes 'a/c'). Not every path here is normalized to begin with - Composer
+		// records install_path as 'vendor/composer/../foo/bar' in installed.php - so the freshly computed
+		// meta is put through the very same transformation. Otherwise the restored meta could never equal
+		// it and the cache would be discarded on every single run.
+		return $this->getPathTransformer()->absolutizeMeta([
 			'cacheVersion' => self::CACHE_VERSION,
 			'phpstanVersion' => ComposerHelper::getPhpStanVersion(),
 			'metaExtensions' => $this->getMetaFromPhpStanExtensions(),
@@ -1605,9 +1609,9 @@ private function getMeta(array $allAnalysedFiles, ?array $projectConfigArray): a
 			// extensions may only run after the bootstrapFiles. This entry catches a changed
 			// list in any config file, including the included ones that are not part of the
 			// projectConfig entry above.
-			'configStubFiles' => array_map(fn (string $stubFile): string => $this->fileHelper->normalizePath($stubFile), $this->configStubFiles),
+			'configStubFiles' => $this->configStubFiles,
 			'level' => $this->usedLevel,
-		];
+		]);
 	}
 
 	private function getFileHash(string $path): string
diff --git a/src/Command/CommandHelper.php b/src/Command/CommandHelper.php
index 5f89864098e..84bfb5c3cfe 100644
--- a/src/Command/CommandHelper.php
+++ b/src/Command/CommandHelper.php
@@ -181,7 +181,7 @@ public static function begin(
 		$autoloadFunctionsBefore = spl_autoload_functions();
 
 		if ($autoloadFile !== null) {
-			$autoloadFile = $currentWorkingDirectoryFileHelper->absolutizePath($autoloadFile);
+			$autoloadFile = $currentWorkingDirectoryFileHelper->normalizePath($currentWorkingDirectoryFileHelper->absolutizePath($autoloadFile));
 			if (!is_file($autoloadFile)) {
 				$errorOutput->writeLineFormatted(sprintf('Autoload file "%s" not found.', $autoloadFile));
 				throw new InceptionNotSuccessfulException();
@@ -209,7 +209,7 @@ public static function begin(
 				}
 			}
 		} else {
-			$projectConfigFile = $currentWorkingDirectoryFileHelper->absolutizePath($projectConfigFile);
+			$projectConfigFile = $currentWorkingDirectoryFileHelper->normalizePath($currentWorkingDirectoryFileHelper->absolutizePath($projectConfigFile));
 		}
 
 		if ($generateBaselineFile !== null) {
diff --git a/src/DependencyInjection/NormalizePathParametersExtension.php b/src/DependencyInjection/NormalizePathParametersExtension.php
new file mode 100644
index 00000000000..c154584dd48
--- /dev/null
+++ b/src/DependencyInjection/NormalizePathParametersExtension.php
@@ -0,0 +1,135 @@
+<?php declare(strict_types = 1);
+
+namespace PHPStan\DependencyInjection;
+
+use Nette\DI\CompilerExtension;
+use Override;
+use PHPStan\DependencyInjection\Neon\OptionalPath;
+use PHPStan\File\FileHelper;
+use function array_key_exists;
+use function array_shift;
+use function is_array;
+use function is_string;
+use function preg_match_all;
+
+/**
+ * NeonAdapter absolutizes and normalizes the path entries listed in the `expandRelativePaths` section,
+ * but only the ones that do not contain a `%placeholder%` - those are still unexpanded strings at load
+ * time. A path like `%rootDir%/../../../vendor/autoload.php` therefore reaches the container with its
+ * `..` segments intact, and every consumer sees a different spelling of the same file than it would for
+ * the equivalent placeholder-free entry.
+ *
+ * The parameters are fully expanded by the time any extension's loadConfiguration() runs, so this is the
+ * first point where the same normalization can be applied. Doing it here rather than at each consumer
+ * keeps a single spelling of every configured path in the container - which is what the result cache
+ * compares its stored metadata against, see https://github.com/phpstan/phpstan/issues/15125
+ */
+#[ContainerExtension(name: 'normalizePathParameters')]
+final class NormalizePathParametersExtension extends CompilerExtension
+{
+
+	#[Override]
+	public function loadConfiguration(): void
+	{
+		$builder = $this->getContainerBuilder();
+		$fileHelper = new FileHelper($builder->parameters['currentWorkingDirectory']);
+
+		foreach ($this->getExpandRelativePaths() as $configKey) {
+			if (preg_match_all('~\[([^\]]*)\]~', $configKey, $matches) === 0) {
+				continue;
+			}
+
+			$segments = $matches[1];
+			if (array_shift($segments) !== 'parameters') {
+				continue;
+			}
+
+			$parameters = $builder->parameters;
+			$this->normalizeAtPath($parameters, $segments, $fileHelper);
+			$builder->parameters = $parameters;
+		}
+	}
+
+	/**
+	 * @return list<string>
+	 */
+	private function getExpandRelativePaths(): array
+	{
+		$configKeys = [];
+		foreach ($this->compiler->getExtensions(ExpandRelativePathExtension::class) as $extension) {
+			foreach ($extension->getConfig() as $configKey) {
+				if (!is_string($configKey)) {
+					continue;
+				}
+
+				$configKeys[] = $configKey;
+			}
+		}
+
+		return $configKeys;
+	}
+
+	/**
+	 * @param mixed[] $value
+	 * @param list<string> $segments an empty segment stands for "every element of this list"
+	 */
+	private function normalizeAtPath(array &$value, array $segments, FileHelper $fileHelper): void
+	{
+		$segment = array_shift($segments);
+		if ($segment === null) {
+			return;
+		}
+
+		if ($segment === '') {
+			foreach ($value as $key => $item) {
+				$value[$key] = $this->normalizeItem($item, $segments, $fileHelper);
+			}
+
+			return;
+		}
+
+		if (!array_key_exists($segment, $value)) {
+			return;
+		}
+
+		$value[$segment] = $this->normalizeItem($value[$segment], $segments, $fileHelper);
+	}
+
+	/**
+	 * @param list<string> $segments
+	 */
+	private function normalizeItem(mixed $item, array $segments, FileHelper $fileHelper): mixed
+	{
+		if ($segments !== []) {
+			if (is_array($item)) {
+				$this->normalizeAtPath($item, $segments, $fileHelper);
+			}
+
+			return $item;
+		}
+
+		if ($item instanceof OptionalPath) {
+			return new OptionalPath($this->normalizePath($item->path, $fileHelper));
+		}
+
+		if (!is_string($item)) {
+			return $item;
+		}
+
+		return $this->normalizePath($item, $fileHelper);
+	}
+
+	private function normalizePath(string $path, FileHelper $fileHelper): string
+	{
+		// A path that is still relative here is either an fnmatch pattern or came from a placeholder that
+		// expanded to a relative value; there is no config file left to resolve it against, and
+		// normalizePath() would silently drop its leading '..' segments. absolutizePath() returning the
+		// path unchanged is what "already absolute" means to the rest of PHPStan, including `scheme://` URLs.
+		if ($fileHelper->absolutizePath($path) !== $path) {
+			return $path;
+		}
+
+		return $fileHelper->normalizePath($path);
+	}
+
+}
diff --git a/tests/PHPStan/Analyser/ResultCache/ResultCachePathTransformerTest.php b/tests/PHPStan/Analyser/ResultCache/ResultCachePathTransformerTest.php
new file mode 100644
index 00000000000..2f7985b30a0
--- /dev/null
+++ b/tests/PHPStan/Analyser/ResultCache/ResultCachePathTransformerTest.php
@@ -0,0 +1,82 @@
+<?php declare(strict_types = 1);
+
+namespace PHPStan\Analyser\ResultCache;
+
+use Override;
+use PHPUnit\Framework\TestCase;
+use const DIRECTORY_SEPARATOR;
+
+class ResultCachePathTransformerTest extends TestCase
+{
+
+	private function createTransformer(): ResultCachePathTransformer
+	{
+		return new ResultCachePathTransformer('/project/vendor/phpstan/phpstan');
+	}
+
+	#[Override]
+	protected function setUp(): void
+	{
+		if (DIRECTORY_SEPARATOR === '/') {
+			return;
+		}
+
+		self::markTestSkipped('Test runs only on Unix-like systems.');
+	}
+
+	public function testRoundTripCanonicalizesDotDotSegments(): void
+	{
+		$transformer = $this->createTransformer();
+		$path = '/project/vendor/composer/../nette/neon/src/Neon.php';
+
+		$this->assertSame(
+			'/project/vendor/nette/neon/src/Neon.php',
+			$transformer->absolutizePath($transformer->relativizePath($path)),
+		);
+	}
+
+	/**
+	 * Composer records install_path in vendor/composer/installed.php as `vendor/composer/../foo/bar`,
+	 * so the meta the result cache stores is not normalized to begin with. Restoring it collapses those
+	 * `..` segments, which is why ResultCacheManager::getMeta() puts the freshly computed meta through
+	 * the very same transformation - otherwise the restored meta could never equal the computed one and
+	 * the cache would be discarded on every run.
+	 */
+	public function testAbsolutizeMetaIsTheCanonicalFormOfTheRoundTrip(): void
+	{
+		$transformer = $this->createTransformer();
+		$meta = [
+			'analysedPaths' => ['/project/src/../src'],
+			'scannedFiles' => ['/project/vendor/phpstan/phpstan/../../../vendor/autoload.php' => 'hash'],
+			'executedFilesHashes' => ['/project/vendor/../vendor/autoload.php' => 'hash'],
+			'composerLocks' => ['/project/./composer.lock' => 'hash'],
+			'composerInstalled' => [
+				'/project/vendor/composer/installed.php' => [
+					'versions' => [
+						'nette/neon' => ['install_path' => '/project/vendor/composer/../nette/neon'],
+					],
+				],
+			],
+		];
+
+		$canonical = $transformer->absolutizeMeta($meta);
+
+		$this->assertSame([
+			'analysedPaths' => ['/project/src'],
+			'scannedFiles' => ['/project/vendor/autoload.php' => 'hash'],
+			'executedFilesHashes' => ['/project/vendor/autoload.php' => 'hash'],
+			'composerLocks' => ['/project/composer.lock' => 'hash'],
+			'composerInstalled' => [
+				'/project/vendor/composer/installed.php' => [
+					'versions' => [
+						'nette/neon' => ['install_path' => '/project/vendor/nette/neon'],
+					],
+				],
+			],
+		], $canonical);
+
+		$this->assertSame($canonical, $transformer->absolutizeMeta($transformer->relativizeMeta($meta)));
+		$this->assertSame($canonical, $transformer->absolutizeMeta($canonical));
+	}
+
+}
diff --git a/tests/PHPStan/Command/CommandHelperTest.php b/tests/PHPStan/Command/CommandHelperTest.php
index a9c2c8414ee..779ac8f6a1f 100644
--- a/tests/PHPStan/Command/CommandHelperTest.php
+++ b/tests/PHPStan/Command/CommandHelperTest.php
@@ -283,6 +283,52 @@ public static function dataParameters(): array
 					],
 				],
 			],
+			[
+				// paths built out of a %placeholder% are not expanded when the Neon file is read, so
+				// they reach the container with their '..' segments intact unless they get normalized
+				// after the expansion - https://github.com/phpstan/phpstan/issues/15125
+				__DIR__ . '/relative-paths/placeholder-dots.neon',
+				[
+					'bootstrapFiles' => [
+						realpath(__DIR__ . '/../../../stubs/runtime/ReflectionUnionType.php'),
+						realpath(__DIR__ . '/../../../stubs/runtime/ReflectionAttribute.php'),
+						realpath(__DIR__ . '/../../../stubs/runtime/Attribute85.php'),
+						realpath(__DIR__ . '/../../../stubs/runtime/ReflectionIntersectionType.php'),
+						__DIR__ . DIRECTORY_SEPARATOR . 'relative-paths' . DIRECTORY_SEPARATOR . 'here.php',
+					],
+					'scanFiles' => [
+						__DIR__ . DIRECTORY_SEPARATOR . 'relative-paths' . DIRECTORY_SEPARATOR . 'here.php',
+						__DIR__ . DIRECTORY_SEPARATOR . 'relative-paths' . DIRECTORY_SEPARATOR . 'test' . DIRECTORY_SEPARATOR . 'there.php',
+						__DIR__ . DIRECTORY_SEPARATOR . 'relative-paths' . DIRECTORY_SEPARATOR . 'up.php',
+					],
+					'scanDirectories' => [
+						__DIR__ . DIRECTORY_SEPARATOR . 'relative-paths' . DIRECTORY_SEPARATOR . 'src',
+					],
+					'paths' => [
+						__DIR__ . DIRECTORY_SEPARATOR . 'relative-paths' . DIRECTORY_SEPARATOR . 'src',
+					],
+					'excludePaths' => [
+						'analyseAndScan' => [
+							__DIR__ . DIRECTORY_SEPARATOR . 'relative-paths' . DIRECTORY_SEPARATOR . 'test',
+						],
+						'analyse' => [
+							__DIR__ . DIRECTORY_SEPARATOR . 'relative-paths' . DIRECTORY_SEPARATOR . 'src',
+						],
+					],
+					'ignoreErrors' => [
+						[
+							'message' => '#aaa#',
+							'path' => __DIR__ . DIRECTORY_SEPARATOR . 'relative-paths' . DIRECTORY_SEPARATOR . 'src' . DIRECTORY_SEPARATOR . 'aaa.php',
+						],
+						[
+							'message' => '#bbb#',
+							'paths' => [
+								__DIR__ . DIRECTORY_SEPARATOR . 'relative-paths' . DIRECTORY_SEPARATOR . 'src' . DIRECTORY_SEPARATOR . 'bbb.php',
+							],
+						],
+					],
+				],
+			],
 		];
 	}
 
diff --git a/tests/PHPStan/Command/relative-paths/placeholder-dots.neon b/tests/PHPStan/Command/relative-paths/placeholder-dots.neon
new file mode 100644
index 00000000000..8f1727a1089
--- /dev/null
+++ b/tests/PHPStan/Command/relative-paths/placeholder-dots.neon
@@ -0,0 +1,25 @@
+parameters:
+	bootstrapFiles:
+		- %rootDir%/tests/PHPStan/Command/relative-paths/nested/../here.php
+	scanFiles:
+		- %rootDir%/tests/PHPStan/Command/relative-paths/../relative-paths/here.php
+		- %rootDir%/tests/PHPStan/Command/relative-paths/test/../test/there.php
+		- %rootDir%/tests/PHPStan/Command/relative-paths/nested/../up.php
+	scanDirectories:
+		- %rootDir%/tests/PHPStan/Command/relative-paths/nested/../src
+	paths:
+		- %rootDir%/tests/PHPStan/Command/relative-paths/nested/../src
+	excludePaths:
+		analyse:
+			- %rootDir%/tests/PHPStan/Command/relative-paths/nested/../src
+		analyseAndScan:
+			- %rootDir%/tests/PHPStan/Command/relative-paths/nested/../test
+	reportUnmatchedIgnoredErrors: false
+	ignoreErrors:
+		-
+			message: '#aaa#'
+			path: %rootDir%/tests/PHPStan/Command/relative-paths/nested/../src/aaa.php
+		-
+			message: '#bbb#'
+			paths:
+				- %rootDir%/tests/PHPStan/Command/relative-paths/nested/../src/bbb.php