diff --git a/.changelog/twig-evaluation-contract.md b/.changelog/twig-evaluation-contract.md
new file mode 100644
index 0000000..05c9c2f
--- /dev/null
+++ b/.changelog/twig-evaluation-contract.md
@@ -0,0 +1,9 @@
+---
+category: added
+type: minor
+---
+
+Add a reproducible, isolated Twig evaluation on the existing PHP matrix. Qualify
+native Finder/Git intersection, explicit configuration overrides, grammar parsing,
+deterministic native JSON and check/fix boundaries without adding a consumer CLI
+profile or changing the package's runtime dependencies.
diff --git a/.github/workflows/repository-ci.yml b/.github/workflows/repository-ci.yml
index a8a609b..849c88b 100644
--- a/.github/workflows/repository-ci.yml
+++ b/.github/workflows/repository-ci.yml
@@ -32,4 +32,15 @@ jobs:
           COMPOSER_CACHE_DIR: ${{ runner.temp }}/standards-composer-cache
       - run: composer validate --strict
       - run: composer check
+      - name: Provision isolated Twig evaluation dependencies
+        run: composer install --working-dir=tests/Evaluation/Twig --no-dev --no-plugins --no-scripts --no-interaction --prefer-dist --no-progress
+        env:
+          COMPOSER_HOME: ${{ runner.temp }}/standards-twig-composer-home
+          COMPOSER_CACHE_DIR: ${{ runner.temp }}/standards-twig-composer-cache
+          COMPOSER_VENDOR_DIR: ${{ runner.temp }}/standards-twig-vendor
+      - name: Evaluate native Twig contracts
+        run: php tests/Evaluation/Twig/evaluate.php
+        env:
+          TWIG_EVALUATION_AUTOLOAD: ${{ runner.temp }}/standards-twig-vendor/autoload.php
+          TWIG_EVALUATION_TEMP: ${{ runner.temp }}
       - run: git diff --exit-code
diff --git a/docs/twig-evaluation.rst b/docs/twig-evaluation.rst
new file mode 100644
index 0000000..f2f124e
--- /dev/null
+++ b/docs/twig-evaluation.rst
@@ -0,0 +1,121 @@
+Native Twig evaluation
+======================
+
+This contributor evaluation qualifies one formatter, Twig-CS-Fixer, together
+with Twig's native syntax parser. It does not expose a Code Standards Twig
+command, install anything during a check, or establish a supported consumer
+profile. It covers the evaluation portion of `issue #9
+<https://github.com/php-fast-forward/code-standards/issues/9>`_; that issue's
+broader command, compatibility and acceptance criteria remain separate.
+
+The nested Composer lock selects published Twig-CS-Fixer 4.1.1, source
+``53c1234b6e5d87ac2beaf686774bba013697f9c5``, and Twig 3.30.0, source
+``8c737079b726af72ff8ef3c595be9f6a810ea1ef``. The evaluator verifies those actual
+installed metadata records. Its graph is separate from the package's runtime
+and contributor dependencies. The resolution platform is PHP 8.3.0; the existing
+repository CI matrix executes the evaluation on PHP 8.3, 8.4 and 8.5.
+
+Explicit provisioning
+---------------------
+
+Dependency provisioning is a separate operation. The evaluator requires an
+existing absolute ``vendor/autoload.php`` outside the checkout and fails with
+an objective diagnostic when it is absent. It never invokes Composer. CI places
+the isolated vendor, Composer home and cache under ``runner.temp`` and disables
+plugins and scripts during installation.
+
+For a local checkout, provision into a newly owned external directory:
+
+.. code-block:: console
+
+   twig_evaluation_runtime="$(mktemp -d "${TMPDIR:-/tmp}/standards-twig.XXXXXX")"
+   COMPOSER_HOME="$twig_evaluation_runtime/home" \
+   COMPOSER_CACHE_DIR="$twig_evaluation_runtime/cache" \
+   COMPOSER_VENDOR_DIR="$twig_evaluation_runtime/vendor" \
+     composer install --working-dir=tests/Evaluation/Twig --no-dev --no-plugins --no-scripts --no-interaction --prefer-dist --no-progress
+   TWIG_EVALUATION_AUTOLOAD="$twig_evaluation_runtime/vendor/autoload.php" \
+   TWIG_EVALUATION_TEMP="$twig_evaluation_runtime" \
+     php tests/Evaluation/Twig/evaluate.php
+
+The harness creates and removes only its own randomly named synthetic fixture.
+It preserves the caller-provisioned runtime. No real consumer checkout is
+analysed or changed by this evaluation.
+
+Qualified path and rule contracts
+--------------------------------
+
+``ConfigResolver::resolveConfig([], $configPath, true)`` preserves the native
+consumer Finder and disables the native cache. Explicit native CLI paths can
+replace that Finder. The harness reproduces that gap and tests the narrower
+integration: iterate the complete configured Finder result, then intersect it
+with the Git-eligible candidate identities and materialize a sorted, deduplicated
+file list. This includes appended Finder iterables, which do not necessarily
+pass its directory filters. Configuration cannot expand the selected scan.
+
+The owned fixture covers Finder exclusions, Git-ignored force-added files,
+unselected and outside-appended files, duplicates, spaces and newline-bearing
+paths. Git's NUL-delimited output is retained. These assertions qualify the
+native integration boundary; they do not introduce a second Git diff parser.
+
+The fixture selects native ``Standard\Twig`` explicitly, rather than silently
+adding all rules from ``Standard\TwigCsFixer`` or a framework standard. Consumer
+``overrideRule()`` and ``removeRule()`` remain authoritative. ``addRule()`` can
+retain distinct configurations of the same class, so it is not treated as a
+universal last-wins replacement. Owned defaults are not reapplied after an
+explicit consumer configuration.
+
+Syntax, writes and reporting
+----------------------------
+
+Native style checks alone do not establish complete Twig grammar validity.
+The test worker first calls native ``Environment::tokenize()`` and ``parse()``
+for all effective files. Grammar failure prevents any fix pass. The parser
+receives the selected native Config's extensions, token parsers and node
+visitors. A custom tag and registered application function parse successfully;
+the function is not invoked and a missing include is not loaded. An unregistered
+custom tag fails. No template is compiled or rendered.
+
+The style pass uses native ``Linter``, ``Tokenizer`` and an explicit ``Fixer``
+only for the requested write case. Check preserves source/configuration/lock
+bytes; explicit fix is followed by check and a second idempotent fix. Native
+JSON comes directly from ``GitlabReporter`` into a fresh output buffer, without
+scraping ANSI or human-output prefixes. Every result gets a new reporter because
+the native object retains fingerprint collision state. Repeated checks produce
+byte-identical JSON, including escaped control characters in relative paths.
+The native report's error/fatal count determines failure, independently of
+presentation thresholds.
+
+Limits
+------
+
+Configuration and registered extension PHP are explicitly trusted executable
+code. Parsing can execute token parsers and node visitors; absence of rendering
+is not a sandbox guarantee. The native Config resolver does not automatically
+import the consumer's ``vendor/autoload.php`` in the qualified version. A
+sentinel regression checks that boundary; an explicit configuration can still
+load an application intentionally.
+
+Twig-CS-Fixer Config 4.1.1 exposes extensions, token parsers and node visitors, not an arbitrary
+complete application Environment, custom lexer, loader or environment options.
+Those full-environment integrations are unsupported by this evaluation. Unknown
+application functions and tags need native registration. The style engine's
+stubbed environment is not substituted for the explicit syntax environment.
+Parsing with Twig 3.30.0 does not prove compatibility with an older consumer Twig
+minimum or the existence of imported application resources.
+
+Twigcs remains an overlapping style comparator, not a second mandatory pass.
+The evaluated standalone twig-linter package has incompatible Symfony constraints
+and is not added. This bounded strategy avoids three mandatory engines while
+preserving the unresolved consumer-profile decisions in issue #9.
+
+Implementation references
+-------------------------
+
+- `Native Config resolution and Finder precedence
+  <https://github.com/VincentLanglet/Twig-CS-Fixer/blob/53c1234b6e5d87ac2beaf686774bba013697f9c5/src/Config/ConfigResolver.php>`_
+- `Native rule overrides
+  <https://github.com/VincentLanglet/Twig-CS-Fixer/blob/53c1234b6e5d87ac2beaf686774bba013697f9c5/src/Ruleset/Ruleset.php>`_
+- `Native JSON reporter
+  <https://github.com/VincentLanglet/Twig-CS-Fixer/blob/53c1234b6e5d87ac2beaf686774bba013697f9c5/src/Report/Reporter/GitlabReporter.php>`_
+- `Twig Environment parsing API
+  <https://github.com/twigphp/Twig/blob/8c737079b726af72ff8ef3c595be9f6a810ea1ef/src/Environment.php>`_
diff --git a/tests/Evaluation/Twig/composer.json b/tests/Evaluation/Twig/composer.json
new file mode 100644
index 0000000..5e15ea2
--- /dev/null
+++ b/tests/Evaluation/Twig/composer.json
@@ -0,0 +1,22 @@
+{
+    "name": "fixture/code-standards-twig-evaluation",
+    "description": "Isolated test dependencies for the native Twig evaluation",
+    "type": "project",
+    "license": "MIT",
+    "require": {
+        "php": "^8.3",
+        "symfony/console": "^7.4",
+        "symfony/filesystem": "^7.4",
+        "symfony/finder": "^7.4",
+        "symfony/process": "^7.4",
+        "twig/twig": "3.30.*",
+        "vincentlanglet/twig-cs-fixer": "4.1.*"
+    },
+    "config": {
+        "allow-plugins": false,
+        "platform": {
+            "php": "8.3.0"
+        },
+        "sort-packages": true
+    }
+}
diff --git a/tests/Evaluation/Twig/composer.lock b/tests/Evaluation/Twig/composer.lock
new file mode 100644
index 0000000..872c396
--- /dev/null
+++ b/tests/Evaluation/Twig/composer.lock
@@ -0,0 +1,1185 @@
+{
+    "_readme": [
+        "This file locks the dependencies of your project to a known state",
+        "Read more about it at https://getcomposer.org/doc/01-basic-usage.md#installing-dependencies",
+        "This file is @generated automatically"
+    ],
+    "content-hash": "a5630985ac92def1226f181ab1df9f52",
+    "packages": [
+        {
+            "name": "psr/container",
+            "version": "2.0.2",
+            "source": {
+                "type": "git",
+                "url": "https://github.com/php-fig/container.git",
+                "reference": "c71ecc56dfe541dbd90c5360474fbc405f8d5963"
+            },
+            "dist": {
+                "type": "zip",
+                "url": "https://api.github.com/repos/php-fig/container/zipball/c71ecc56dfe541dbd90c5360474fbc405f8d5963",
+                "reference": "c71ecc56dfe541dbd90c5360474fbc405f8d5963",
+                "shasum": ""
+            },
+            "require": {
+                "php": ">=7.4.0"
+            },
+            "type": "library",
+            "extra": {
+                "branch-alias": {
+                    "dev-master": "2.0.x-dev"
+                }
+            },
+            "autoload": {
+                "psr-4": {
+                    "Psr\\Container\\": "src/"
+                }
+            },
+            "notification-url": "https://packagist.org/downloads/",
+            "license": [
+                "MIT"
+            ],
+            "authors": [
+                {
+                    "name": "PHP-FIG",
+                    "homepage": "https://www.php-fig.org/"
+                }
+            ],
+            "description": "Common Container Interface (PHP FIG PSR-11)",
+            "homepage": "https://github.com/php-fig/container",
+            "keywords": [
+                "PSR-11",
+                "container",
+                "container-interface",
+                "container-interop",
+                "psr"
+            ],
+            "support": {
+                "issues": "https://github.com/php-fig/container/issues",
+                "source": "https://github.com/php-fig/container/tree/2.0.2"
+            },
+            "time": "2021-11-05T16:47:00+00:00"
+        },
+        {
+            "name": "symfony/console",
+            "version": "v7.4.21",
+            "source": {
+                "type": "git",
+                "url": "https://github.com/symfony/console.git",
+                "reference": "21f1bc2296f7ff6043241a8dcbc09559b3732820"
+            },
+            "dist": {
+                "type": "zip",
+                "url": "https://api.github.com/repos/symfony/console/zipball/21f1bc2296f7ff6043241a8dcbc09559b3732820",
+                "reference": "21f1bc2296f7ff6043241a8dcbc09559b3732820",
+                "shasum": ""
+            },
+            "require": {
+                "php": ">=8.2",
+                "symfony/deprecation-contracts": "^2.5|^3",
+                "symfony/polyfill-mbstring": "~1.0",
+                "symfony/service-contracts": "^2.5|^3",
+                "symfony/string": "^7.2|^8.0"
+            },
+            "conflict": {
+                "symfony/dependency-injection": "<6.4",
+                "symfony/dotenv": "<6.4",
+                "symfony/event-dispatcher": "<6.4",
+                "symfony/lock": "<6.4",
+                "symfony/process": "<6.4"
+            },
+            "provide": {
+                "psr/log-implementation": "1.0|2.0|3.0"
+            },
+            "require-dev": {
+                "psr/log": "^1|^2|^3",
+                "symfony/config": "^6.4|^7.0|^8.0",
+                "symfony/dependency-injection": "^6.4|^7.0|^8.0",
+                "symfony/event-dispatcher": "^6.4|^7.0|^8.0",
+                "symfony/http-foundation": "^6.4|^7.0|^8.0",
+                "symfony/http-kernel": "^6.4|^7.0|^8.0",
+                "symfony/lock": "^6.4|^7.0|^8.0",
+                "symfony/messenger": "^6.4|^7.0|^8.0",
+                "symfony/process": "^6.4|^7.0|^8.0",
+                "symfony/stopwatch": "^6.4|^7.0|^8.0",
+                "symfony/var-dumper": "^6.4|^7.0|^8.0"
+            },
+            "type": "library",
+            "autoload": {
+                "psr-4": {
+                    "Symfony\\Component\\Console\\": ""
+                },
+                "exclude-from-classmap": [
+                    "/Tests/"
+                ]
+            },
+            "notification-url": "https://packagist.org/downloads/",
+            "license": [
+                "MIT"
+            ],
+            "authors": [
+                {
+                    "name": "Fabien Potencier",
+                    "email": "fabien@symfony.com"
+                },
+                {
+                    "name": "Symfony Community",
+                    "homepage": "https://symfony.com/contributors"
+                }
+            ],
+            "description": "Eases the creation of beautiful and testable command line interfaces",
+            "homepage": "https://symfony.com",
+            "keywords": [
+                "cli",
+                "command-line",
+                "console",
+                "terminal"
+            ],
+            "support": {
+                "source": "https://github.com/symfony/console/tree/v7.4.21"
+            },
+            "funding": [
+                {
+                    "url": "https://symfony.com/sponsor",
+                    "type": "custom"
+                },
+                {
+                    "url": "https://github.com/fabpot",
+                    "type": "github"
+                },
+                {
+                    "url": "https://github.com/nicolas-grekas",
+                    "type": "github"
+                },
+                {
+                    "url": "https://tidelift.com/funding/github/packagist/symfony/symfony",
+                    "type": "tidelift"
+                }
+            ],
+            "time": "2026-10-12T18:45:38+00:00"
+        },
+        {
+            "name": "symfony/deprecation-contracts",
+            "version": "v3.7.1",
+            "source": {
+                "type": "git",
+                "url": "https://github.com/symfony/deprecation-contracts.git",
+                "reference": "f3202fa1b5097b0af062dc978b32ecf63404e31d"
+            },
+            "dist": {
+                "type": "zip",
+                "url": "https://api.github.com/repos/symfony/deprecation-contracts/zipball/f3202fa1b5097b0af062dc978b32ecf63404e31d",
+                "reference": "f3202fa1b5097b0af062dc978b32ecf63404e31d",
+                "shasum": ""
+            },
+            "require": {
+                "php": ">=8.1"
+            },
+            "type": "library",
+            "extra": {
+                "thanks": {
+                    "url": "https://github.com/symfony/contracts",
+                    "name": "symfony/contracts"
+                },
+                "branch-alias": {
+                    "dev-main": "3.7-dev"
+                }
+            },
+            "autoload": {
+                "files": [
+                    "function.php"
+                ]
+            },
+            "notification-url": "https://packagist.org/downloads/",
+            "license": [
+                "MIT"
+            ],
+            "authors": [
+                {
+                    "name": "Nicolas Grekas",
+                    "email": "p@tchwork.com"
+                },
+                {
+                    "name": "Symfony Community",
+                    "homepage": "https://symfony.com/contributors"
+                }
+            ],
+            "description": "A generic function and convention to trigger deprecation notices",
+            "homepage": "https://symfony.com",
+            "support": {
+                "source": "https://github.com/symfony/deprecation-contracts/tree/v3.7.1"
+            },
+            "funding": [
+                {
+                    "url": "https://symfony.com/sponsor",
+                    "type": "custom"
+                },
+                {
+                    "url": "https://github.com/fabpot",
+                    "type": "github"
+                },
+                {
+                    "url": "https://github.com/nicolas-grekas",
+                    "type": "github"
+                },
+                {
+                    "url": "https://tidelift.com/funding/github/packagist/symfony/symfony",
+                    "type": "tidelift"
+                }
+            ],
+            "time": "2026-06-05T06:23:12+00:00"
+        },
+        {
+            "name": "symfony/filesystem",
+            "version": "v7.4.21",
+            "source": {
+                "type": "git",
+                "url": "https://github.com/symfony/filesystem.git",
+                "reference": "fd0e3462be6d32a0d130e8423e4940a7688162d8"
+            },
+            "dist": {
+                "type": "zip",
+                "url": "https://api.github.com/repos/symfony/filesystem/zipball/fd0e3462be6d32a0d130e8423e4940a7688162d8",
+                "reference": "fd0e3462be6d32a0d130e8423e4940a7688162d8",
+                "shasum": ""
+            },
+            "require": {
+                "php": ">=8.2",
+                "symfony/polyfill-ctype": "~1.8",
+                "symfony/polyfill-mbstring": "~1.8"
+            },
+            "require-dev": {
+                "symfony/process": "^6.4|^7.0|^8.0"
+            },
+            "type": "library",
+            "autoload": {
+                "psr-4": {
+                    "Symfony\\Component\\Filesystem\\": ""
+                },
+                "exclude-from-classmap": [
+                    "/Tests/"
+                ]
+            },
+            "notification-url": "https://packagist.org/downloads/",
+            "license": [
+                "MIT"
+            ],
+            "authors": [
+                {
+                    "name": "Fabien Potencier",
+                    "email": "fabien@symfony.com"
+                },
+                {
+                    "name": "Symfony Community",
+                    "homepage": "https://symfony.com/contributors"
+                }
+            ],
+            "description": "Provides basic utilities for the filesystem",
+            "homepage": "https://symfony.com",
+            "support": {
+                "source": "https://github.com/symfony/filesystem/tree/v7.4.21"
+            },
+            "funding": [
+                {
+                    "url": "https://symfony.com/sponsor",
+                    "type": "custom"
+                },
+                {
+                    "url": "https://github.com/fabpot",
+                    "type": "github"
+                },
+                {
+                    "url": "https://github.com/nicolas-grekas",
+                    "type": "github"
+                },
+                {
+                    "url": "https://tidelift.com/funding/github/packagist/symfony/symfony",
+                    "type": "tidelift"
+                }
+            ],
+            "time": "2026-10-06T20:05:19+00:00"
+        },
+        {
+            "name": "symfony/finder",
+            "version": "v7.4.20",
+            "source": {
+                "type": "git",
+                "url": "https://github.com/symfony/finder.git",
+                "reference": "2dd31e5208db7a0fda7bfc998ad727b79c2e4d1e"
+            },
+            "dist": {
+                "type": "zip",
+                "url": "https://api.github.com/repos/symfony/finder/zipball/2dd31e5208db7a0fda7bfc998ad727b79c2e4d1e",
+                "reference": "2dd31e5208db7a0fda7bfc998ad727b79c2e4d1e",
+                "shasum": ""
+            },
+            "require": {
+                "php": ">=8.2"
+            },
+            "require-dev": {
+                "symfony/filesystem": "^6.4|^7.0|^8.0"
+            },
+            "type": "library",
+            "autoload": {
+                "psr-4": {
+                    "Symfony\\Component\\Finder\\": ""
+                },
+                "exclude-from-classmap": [
+                    "/Tests/"
+                ]
+            },
+            "notification-url": "https://packagist.org/downloads/",
+            "license": [
+                "MIT"
+            ],
+            "authors": [
+                {
+                    "name": "Fabien Potencier",
+                    "email": "fabien@symfony.com"
+                },
+                {
+                    "name": "Symfony Community",
+                    "homepage": "https://symfony.com/contributors"
+                }
+            ],
+            "description": "Finds files and directories via an intuitive fluent interface",
+            "homepage": "https://symfony.com",
+            "support": {
+                "source": "https://github.com/symfony/finder/tree/v7.4.20"
+            },
+            "funding": [
+                {
+                    "url": "https://symfony.com/sponsor",
+                    "type": "custom"
+                },
+                {
+                    "url": "https://github.com/fabpot",
+                    "type": "github"
+                },
+                {
+                    "url": "https://github.com/nicolas-grekas",
+                    "type": "github"
+                },
+                {
+                    "url": "https://tidelift.com/funding/github/packagist/symfony/symfony",
+                    "type": "tidelift"
+                }
+            ],
+            "time": "2026-09-26T06:31:10+00:00"
+        },
+        {
+            "name": "symfony/polyfill-ctype",
+            "version": "v1.37.0",
+            "source": {
+                "type": "git",
+                "url": "https://github.com/symfony/polyfill-ctype.git",
+                "reference": "141046a8f9477948ff284fa65be2095baafb94f2"
+            },
+            "dist": {
+                "type": "zip",
+                "url": "https://api.github.com/repos/symfony/polyfill-ctype/zipball/141046a8f9477948ff284fa65be2095baafb94f2",
+                "reference": "141046a8f9477948ff284fa65be2095baafb94f2",
+                "shasum": ""
+            },
+            "require": {
+                "php": ">=7.2"
+            },
+            "provide": {
+                "ext-ctype": "*"
+            },
+            "suggest": {
+                "ext-ctype": "For best performance"
+            },
+            "type": "library",
+            "extra": {
+                "thanks": {
+                    "url": "https://github.com/symfony/polyfill",
+                    "name": "symfony/polyfill"
+                }
+            },
+            "autoload": {
+                "files": [
+                    "bootstrap.php"
+                ],
+                "psr-4": {
+                    "Symfony\\Polyfill\\Ctype\\": ""
+                }
+            },
+            "notification-url": "https://packagist.org/downloads/",
+            "license": [
+                "MIT"
+            ],
+            "authors": [
+                {
+                    "name": "Gert de Pagter",
+                    "email": "BackEndTea@gmail.com"
+                },
+                {
+                    "name": "Symfony Community",
+                    "homepage": "https://symfony.com/contributors"
+                }
+            ],
+            "description": "Symfony polyfill for ctype functions",
+            "homepage": "https://symfony.com",
+            "keywords": [
+                "compatibility",
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+            ],
+            "description": "A tool to automatically fix Twig code style",
+            "homepage": "https://github.com/VincentLanglet/Twig-CS-Fixer",
+            "support": {
+                "issues": "https://github.com/VincentLanglet/Twig-CS-Fixer/issues",
+                "source": "https://github.com/VincentLanglet/Twig-CS-Fixer/tree/4.1.1"
+            },
+            "funding": [
+                {
+                    "url": "https://github.com/VincentLanglet",
+                    "type": "github"
+                }
+            ],
+            "time": "2026-09-08T21:26:25+00:00"
+        },
+        {
+            "name": "webmozart/assert",
+            "version": "2.5.0",
+            "source": {
+                "type": "git",
+                "url": "https://github.com/webmozarts/assert.git",
+                "reference": "8a163706bbcac613733dba03f51e13b5eb1bb819"
+            },
+            "dist": {
+                "type": "zip",
+                "url": "https://api.github.com/repos/webmozarts/assert/zipball/8a163706bbcac613733dba03f51e13b5eb1bb819",
+                "reference": "8a163706bbcac613733dba03f51e13b5eb1bb819",
+                "shasum": ""
+            },
+            "require": {
+                "ext-ctype": "*",
+                "ext-date": "*",
+                "ext-filter": "*",
+                "php": "^8.2"
+            },
+            "suggest": {
+                "ext-intl": "",
+                "ext-simplexml": "",
+                "ext-spl": ""
+            },
+            "type": "library",
+            "extra": {
+                "psalm": {
+                    "pluginClass": "Webmozart\\Assert\\PsalmPlugin"
+                },
+                "branch-alias": {
+                    "dev-master": "2.0-dev",
+                    "dev-feature/2-0": "2.0-dev"
+                }
+            },
+            "autoload": {
+                "psr-4": {
+                    "Webmozart\\Assert\\": "src/"
+                }
+            },
+            "notification-url": "https://packagist.org/downloads/",
+            "license": [
+                "MIT"
+            ],
+            "authors": [
+                {
+                    "name": "Bernhard Schussek",
+                    "email": "bschussek@gmail.com"
+                },
+                {
+                    "name": "Woody Gilk",
+                    "email": "woody.gilk@gmail.com"
+                }
+            ],
+            "description": "Assertions to validate method input/output with nice error messages.",
+            "keywords": [
+                "assert",
+                "check",
+                "validate"
+            ],
+            "support": {
+                "issues": "https://github.com/webmozarts/assert/issues",
+                "source": "https://github.com/webmozarts/assert/tree/2.5.0"
+            },
+            "time": "2026-10-05T23:14:19+00:00"
+        }
+    ],
+    "packages-dev": [],
+    "aliases": [],
+    "minimum-stability": "stable",
+    "stability-flags": {},
+    "prefer-stable": false,
+    "prefer-lowest": false,
+    "platform": {
+        "php": "^8.3"
+    },
+    "platform-dev": {},
+    "platform-overrides": {
+        "php": "8.3.0"
+    },
+    "plugin-api-version": "2.9.0"
+}
diff --git a/tests/Evaluation/Twig/evaluate.php b/tests/Evaluation/Twig/evaluate.php
new file mode 100644
index 0000000..09a5b1c
--- /dev/null
+++ b/tests/Evaluation/Twig/evaluate.php
@@ -0,0 +1,197 @@
+<?php
+
+declare(strict_types=1);
+
+use Symfony\Component\Filesystem\Filesystem;
+use Symfony\Component\Process\Process;
+use TwigCsFixer\Config\ConfigResolver;
+
+/** Fails an evaluation assertion; this harness is not a public Code Standards command. */
+function verify(bool $condition, string $name): void
+{
+    if (!$condition) {
+        throw new RuntimeException('Twig evaluation failed: ' . $name);
+    }
+    $GLOBALS['evaluation_checks'][] = $name;
+}
+
+/**
+ * Starts only fixed local test tools with finite bounds and without inherited credentials.
+ *
+ * @param list<string> $arguments Actual executable and separate arguments; never shell fragments.
+ * @param array<string, string|false> $environment Explicit synthetic-fixture environment.
+ */
+function process(array $arguments, string $directory, array $environment): Process
+{
+    $process = new Process($arguments, $directory, $environment, timeout: 20);
+    $process->run();
+
+    return $process;
+}
+
+/**
+ * Captures hashes of owned source/configuration; generated test markers are deliberately separate.
+ *
+ * @return array<string, string> Relative fixture names mapped to exact byte hashes.
+ */
+function snapshot(string $directory): array
+{
+    $result = [];
+    foreach (['composer.json', 'composer.lock', 'native-config.php', 'templates/keep a.twig', "templates/keep\nline.twig",
+        'templates/excluded.twig', 'templates/unselected.twig', 'templates/gitignored.twig', 'templates/grammar.twig',
+        'templates/custom.twig', '../outside.twig'] as $path) {
+        $hash = hash_file('sha256', $directory . '/' . $path);
+        if (false === $hash) {
+            throw new RuntimeException('Cannot snapshot owned fixture: ' . $path);
+        }
+        $result[$path] = $hash;
+    }
+
+    return $result;
+}
+
+/**
+ * Runs the native test worker; complete stdout must be native JSON, never a scraped human-output suffix.
+ *
+ * @param list<string> $selected Git-eligible paths; native configuration can narrow this scope.
+ * @param array<string, string|false> $environment Explicit synthetic-fixture environment.
+ */
+function evaluate(string $autoload, string $directory, string $config, string $mode, array $selected, array $environment): Process
+{
+    $process = process([PHP_BINARY, __DIR__ . '/worker.php', $autoload, $directory, $config, $mode, ...$selected], $directory, $environment);
+    if (in_array($process->getExitCode(), [0, 1], true)) {
+        json_decode($process->getOutput(), true, flags: JSON_THROW_ON_ERROR);
+    }
+
+    return $process;
+}
+
+$GLOBALS['evaluation_checks'] = [];
+$fixture = null;
+$status = 0;
+try {
+    $autoload = getenv('TWIG_EVALUATION_AUTOLOAD');
+    if (!is_string($autoload) || !str_starts_with($autoload, '/') || !is_file($autoload)) {
+        throw new InvalidArgumentException('Provision the isolated Twig lock first and set TWIG_EVALUATION_AUTOLOAD to its absolute vendor/autoload.php; the evaluator never installs dependencies.');
+    }
+    $autoload = realpath($autoload);
+    $repository = realpath(dirname(__DIR__, 3));
+    $temporary = realpath(getenv('TWIG_EVALUATION_TEMP') ?: sys_get_temp_dir());
+    if (false === $temporary || !is_dir($temporary) || str_starts_with($temporary . '/', $repository . '/')
+        || str_starts_with($autoload, $repository . '/')) {
+        throw new InvalidArgumentException('Evaluation runtime and temporary fixtures must be provisioned outside the checkout.');
+    }
+    require $autoload;
+
+    $manifest = hash_file('sha256', __DIR__ . '/composer.json');
+    $lock = hash_file('sha256', __DIR__ . '/composer.lock');
+    $installed = json_decode(file_get_contents(dirname($autoload) . '/composer/installed.json'), true, flags: JSON_THROW_ON_ERROR);
+    $versions = [];
+    foreach ($installed['packages'] as $package) {
+        if (in_array($package['name'], ['vincentlanglet/twig-cs-fixer', 'twig/twig'], true)) {
+            $versions[$package['name']] = ['version' => ltrim($package['version'], 'v'), 'source' => $package['source']['reference']];
+        }
+    }
+    verify(($versions['vincentlanglet/twig-cs-fixer'] ?? null) === ['version' => '4.1.1', 'source' => '53c1234b6e5d87ac2beaf686774bba013697f9c5'], 'published-formatter-runtime');
+    verify(($versions['twig/twig'] ?? null) === ['version' => '3.30.0', 'source' => '8c737079b726af72ff8ef3c595be9f6a810ea1ef'], 'published-parser-runtime');
+
+    $fixture = $temporary . '/code-standards-twig-' . bin2hex(random_bytes(12));
+    $directory = $fixture . '/consumer';
+    $filesystem = new Filesystem();
+    $filesystem->mkdir([$directory . '/templates', $directory . '/vendor', $directory . '/.runtime/tmp'], 0700);
+    $environment = array_fill_keys(array_keys(getenv()), false);
+    $environment['PATH'] = getenv('PATH') ?: '/usr/bin:/bin';
+    $environment['HOME'] = $directory . '/.runtime';
+    $environment['TMPDIR'] = $directory . '/.runtime/tmp';
+    $environment['GIT_CONFIG_GLOBAL'] = '/dev/null';
+    $environment['GIT_CONFIG_NOSYSTEM'] = '1';
+    $git = static function (array $arguments) use ($directory, $environment): string {
+        $process = process(['git', ...$arguments], $directory, $environment);
+        if (!$process->isSuccessful()) {
+            throw new RuntimeException($process->getErrorOutput());
+        }
+
+        return $process->getOutput();
+    };
+
+    file_put_contents($directory . '/composer.json', '{"name":"fixture/twig-consumer"}');
+    file_put_contents($directory . '/composer.lock', '{"packages":[]}');
+    file_put_contents($directory . '/.gitignore', "/vendor/\n/.runtime/\n/templates/gitignored.twig\n");
+    file_put_contents($directory . '/vendor/autoload.php', '<?php file_put_contents(__DIR__."/../autoload-executed", "unexpected");');
+    foreach (['keep a.twig', "keep\nline.twig", 'excluded.twig', 'unselected.twig', 'gitignored.twig'] as $name) {
+        file_put_contents($directory . '/templates/' . $name, "{{value}}\n");
+    }
+    file_put_contents($directory . '/templates/grammar.twig', "{% if true %}\n");
+    file_put_contents($directory . '/templates/custom.twig', "{% fixture_mark %}{{ application_function() }}{% include 'not-present.twig' %}\n");
+    file_put_contents($fixture . '/outside.twig', "{{outside}}\n");
+    $config = file_get_contents(__DIR__ . '/fixtures/native-config.php');
+    file_put_contents($directory . '/native-config.php', $config);
+    $git(['init', '-q']);
+    $git(['add', '--all']);
+    $git(['add', '-f', '--', 'templates/gitignored.twig']);
+    $ignored = array_fill_keys(array_filter(explode("\0", $git(['ls-files', '--cached', '--ignored', '--exclude-per-directory=.gitignore', '-z']))), true);
+    $tracked = array_filter(explode("\0", $git(['ls-files', '-z'])));
+    $selected = array_values(array_filter($tracked, static fn(string $path): bool => in_array($path, [
+        'templates/keep a.twig', "templates/keep\nline.twig", 'templates/excluded.twig', 'templates/gitignored.twig',
+    ], true) && !isset($ignored[$path])));
+    verify(!in_array('templates/gitignored.twig', $selected, true), 'git-ignored-tracked-template-excluded');
+
+    $before = snapshot($directory);
+    $check = evaluate($autoload, $directory, 'native-config.php', 'check', $selected, $environment);
+    verify(1 === $check->getExitCode(), 'native-style-failure:' . $check->getErrorOutput());
+    verify(snapshot($directory) === $before, 'check-preserves-source-config-and-lock');
+    $json = json_decode($check->getOutput(), true, flags: JSON_THROW_ON_ERROR);
+    $reported = array_values(array_unique(array_column(array_column($json, 'location'), 'path')));
+    verify($reported === ["templates/keep\nline.twig", 'templates/keep a.twig'], 'finder-intersection-sorted-and-deduplicated');
+    $again = evaluate($autoload, $directory, 'native-config.php', 'check', $selected, $environment);
+    verify($again->getOutput() === $check->getOutput() && 1 === $again->getExitCode(), 'native-json-byte-deterministic');
+    verify(str_contains($check->getOutput(), 'keep\\nline.twig'), 'native-json-escapes-newline-path');
+
+    // Deliberately reproduce the upstream path replacement instead of proposing that proxy as the adapter.
+    $replaced = (new ConfigResolver($directory))->resolveConfig([$directory . '/templates/excluded.twig'], $directory . '/native-config.php', true);
+    verify(count(iterator_to_array($replaced->getFinder())) === 1, 'cli-path-replacement-gap-reproduced');
+    verify(null === $replaced->getCacheManager() && null === $replaced->getCacheFile(), 'native-cache-disabled');
+
+    $override = str_replace('return $config;', '$config->getRuleset()->overrideRule(new TwigCsFixer\\Rules\\Delimiter\\DelimiterSpacingRule(beforeOverride: ["}}" => 0], afterOverride: ["{{" => 0])); return $config;', $config, $count);
+    verify(1 === $count, 'known-native-fixture-override-point');
+    file_put_contents($directory . '/override.php', $override);
+    verify(0 === evaluate($autoload, $directory, 'override.php', 'check', $selected, $environment)->getExitCode(), 'native-rule-override-last');
+    file_put_contents($directory . '/remove.php', str_replace('return $config;', '$config->getRuleset()->removeRule(TwigCsFixer\\Rules\\Delimiter\\DelimiterSpacingRule::class); return $config;', $config));
+    verify(0 === evaluate($autoload, $directory, 'remove.php', 'check', $selected, $environment)->getExitCode(), 'native-rule-removal-last');
+    verify(snapshot($directory) === $before, 'override-checks-do-not-write');
+
+    verify(0 === evaluate($autoload, $directory, 'native-config.php', 'fix', $selected, $environment)->getExitCode(), 'explicit-native-fix');
+    verify(file_get_contents($directory . '/templates/keep a.twig') === "{{ value }}\n", 'native-fixed-bytes');
+    $fixed = snapshot($directory);
+    verify(0 === evaluate($autoload, $directory, 'native-config.php', 'check', $selected, $environment)->getExitCode(), 'native-post-fix-check');
+    verify(0 === evaluate($autoload, $directory, 'native-config.php', 'fix', $selected, $environment)->getExitCode() && snapshot($directory) === $fixed, 'second-fix-idempotent');
+    foreach (['templates/excluded.twig', 'templates/unselected.twig', 'templates/gitignored.twig', '../outside.twig', 'composer.json', 'composer.lock', 'native-config.php'] as $path) {
+        verify($fixed[$path] === $before[$path], 'outside-effective-selection-unchanged:' . $path);
+    }
+
+    file_put_contents($directory . '/templates/keep a.twig', "{{needs_fix}}\n");
+    $grammarBefore = snapshot($directory);
+    $grammar = evaluate($autoload, $directory, 'native-config.php', 'fix', ['templates/grammar.twig', 'templates/keep a.twig'], $environment);
+    $syntax = json_decode($grammar->getOutput(), true, flags: JSON_THROW_ON_ERROR);
+    verify(1 === $grammar->getExitCode() && ($syntax[0]['severity'] ?? null) === 'critical', 'native-grammar-rejected-before-fix');
+    verify(snapshot($directory) === $grammarBefore, 'syntax-failure-performs-no-fix');
+    verify(0 === evaluate($autoload, $directory, 'native-config.php', 'check', ['templates/custom.twig'], $environment)->getExitCode(), 'custom-tag-function-and-include-parse');
+    verify(is_file($directory . '/tag-parsed') && !file_exists($directory . '/function-called'), 'custom-parser-used-without-rendering');
+    file_put_contents($directory . '/bare.php', '<?php $config = new TwigCsFixer\\Config\\Config(); $config->setFinder((new TwigCsFixer\\File\\Finder())->in(__DIR__."/templates")); return $config;');
+    verify(1 === evaluate($autoload, $directory, 'bare.php', 'check', ['templates/custom.twig'], $environment)->getExitCode(), 'unregistered-custom-tag-rejected');
+    verify(!file_exists($directory . '/autoload-executed') && !file_exists($directory . '/.twig-cs-fixer.cache'), 'no-implicit-consumer-autoload-or-project-cache');
+
+    $missing = process([PHP_BINARY, __FILE__], $directory, $environment);
+    verify(2 === $missing->getExitCode() && str_contains($missing->getErrorOutput(), 'never installs dependencies'), 'missing-provisioned-loader-fails-objectively');
+    verify($manifest === hash_file('sha256', __DIR__ . '/composer.json') && $lock === hash_file('sha256', __DIR__ . '/composer.lock'), 'evaluation-does-not-change-its-dependency-inputs');
+    echo json_encode(['result' => 'passed', 'checks' => count($GLOBALS['evaluation_checks']), 'versions' => $versions], JSON_UNESCAPED_SLASHES | JSON_THROW_ON_ERROR), PHP_EOL;
+} catch (Throwable $error) {
+    fwrite(STDERR, $error->getMessage() . PHP_EOL);
+    $status = 2;
+} finally {
+    if (null !== $fixture) {
+        (new Filesystem())->remove($fixture);
+    }
+}
+
+exit($status);
diff --git a/tests/Evaluation/Twig/fixtures/native-config.php b/tests/Evaluation/Twig/fixtures/native-config.php
new file mode 100644
index 0000000..ed3d7bb
--- /dev/null
+++ b/tests/Evaluation/Twig/fixtures/native-config.php
@@ -0,0 +1,48 @@
+<?php
+
+declare(strict_types=1);
+
+use Twig\Extension\AbstractExtension;
+use Twig\Node\Node;
+use Twig\Token;
+use Twig\TokenParser\AbstractTokenParser;
+use Twig\TwigFunction;
+use TwigCsFixer\Config\Config;
+use TwigCsFixer\File\Finder;
+use TwigCsFixer\Ruleset\Ruleset;
+use TwigCsFixer\Standard\Twig;
+
+$config = new Config('Native Twig evaluation');
+$config->setRuleset((new Ruleset())->addStandard(new Twig()));
+$config->setFinder((new Finder())->in(__DIR__ . '/templates')->notName('excluded.twig')->append([
+    __DIR__ . '/../outside.twig',
+    __DIR__ . '/templates/keep a.twig',
+]));
+$config->addTwigExtension(new class extends AbstractExtension {
+    public function getFunctions(): array
+    {
+        return [new TwigFunction('application_function', static function (): void {
+            file_put_contents(__DIR__ . '/function-called', 'unexpected rendering');
+        })];
+    }
+
+    public function getTokenParsers(): array
+    {
+        return [new class extends AbstractTokenParser {
+            public function parse(Token $token): Node
+            {
+                file_put_contents(__DIR__ . '/tag-parsed', 'native parsing');
+                $this->parser->getStream()->expect(Token::BLOCK_END_TYPE);
+
+                return new Node([], [], $token->getLine());
+            }
+
+            public function getTag(): string
+            {
+                return 'fixture_mark';
+            }
+        }];
+    }
+});
+
+return $config;
diff --git a/tests/Evaluation/Twig/worker.php b/tests/Evaluation/Twig/worker.php
new file mode 100644
index 0000000..bf45af5
--- /dev/null
+++ b/tests/Evaluation/Twig/worker.php
@@ -0,0 +1,123 @@
+<?php
+
+declare(strict_types=1);
+
+use Symfony\Component\Console\Output\BufferedOutput;
+use Twig\Environment;
+use Twig\Error\Error;
+use Twig\Loader\ArrayLoader;
+use Twig\Source;
+use TwigCsFixer\Config\Config;
+use TwigCsFixer\Config\ConfigResolver;
+use TwigCsFixer\Environment\StubbedEnvironment;
+use TwigCsFixer\Report\Report;
+use TwigCsFixer\Report\Reporter\GitlabReporter;
+use TwigCsFixer\Report\Violation;
+use TwigCsFixer\Report\ViolationId;
+use TwigCsFixer\Runner\Fixer;
+use TwigCsFixer\Runner\Linter;
+use TwigCsFixer\Token\Tokenizer;
+
+/**
+ * Materializes the native Finder result before intersecting all entries, including appended iterables.
+ *
+ * @param list<string> $paths Git-eligible template paths inside the owned fixture.
+ * @return list<SplFileInfo> Sorted, deduplicated native file inputs.
+ */
+function selectedFiles(Config $config, array $paths, string $directory): array
+{
+    $selected = [];
+    foreach ($paths as $path) {
+        $real = realpath($path);
+        if (false === $real || !is_file($real) || is_link($path) || !str_starts_with($real, $directory . '/')) {
+            throw new InvalidArgumentException('Expected readable owned template paths inside the fixture.');
+        }
+        $selected[$real] = true;
+    }
+
+    $files = [];
+    foreach ($config->getFinder() as $file) {
+        $real = $file->getRealPath();
+        if (false !== $real && isset($selected[$real])) {
+            $relative = substr($real, strlen($directory) + 1);
+            $files[$relative] = new SplFileInfo($relative);
+        }
+    }
+    ksort($files, SORT_STRING);
+
+    return array_values($files);
+}
+
+/**
+ * Parses with explicitly registered native extensions; never compiles, renders or discovers an application.
+ *
+ * @param list<SplFileInfo> $files Effective native Finder/Git intersection.
+ */
+function syntaxReport(Config $config, array $files): Report
+{
+    $environment = new Environment(new ArrayLoader(), ['cache' => false]);
+    foreach ($config->getTwigExtensions() as $extension) {
+        $environment->addExtension($extension);
+    }
+    foreach ($config->getTokenParsers() as $parser) {
+        $environment->addTokenParser($parser);
+    }
+    foreach ($config->getNodeVisitors() as $visitor) {
+        $environment->addNodeVisitor($visitor);
+    }
+
+    $report = new Report($files);
+    foreach ($files as $file) {
+        $content = file_get_contents($file->getPathname());
+        if (false === $content) {
+            throw new RuntimeException('Cannot read selected fixture template.');
+        }
+        try {
+            $source = new Source($content, $file->getPathname());
+            $environment->parse($environment->tokenize($source));
+        } catch (Error $error) {
+            $report->addViolation(new Violation(
+                Violation::LEVEL_FATAL,
+                $error->getRawMessage(),
+                $file->getPathname(),
+                identifier: new ViolationId(line: $error->getTemplateLine()),
+            ));
+        }
+    }
+
+    return $report;
+}
+
+// Fixed test-worker arguments: preinstalled autoloader, owned fixture, native config, mode and selected paths.
+try {
+    if ($argc < 6 || !in_array($argv[4], ['check', 'fix'], true) || !is_file($argv[1])) {
+        throw new InvalidArgumentException('Twig evaluation worker requires its provisioned runtime and owned fixture arguments.');
+    }
+    require $argv[1];
+    $directory = realpath($argv[2]);
+    if (false === $directory || !is_dir($directory) || !chdir($directory)) {
+        throw new InvalidArgumentException('Cannot enter the owned Twig fixture directory.');
+    }
+
+    $config = (new ConfigResolver($directory))->resolveConfig([], $argv[3], true);
+    $files = selectedFiles($config, array_slice($argv, 5), $directory);
+    $report = syntaxReport($config, $files);
+    if (0 === $report->getTotalErrors()) {
+        $environment = new StubbedEnvironment($config->getTwigExtensions(), $config->getTokenParsers(), $config->getNodeVisitors());
+        $tokenizer = new Tokenizer($environment);
+        $report = (new Linter($environment, $tokenizer, $config->getCacheManager()))->run(
+            $files,
+            $config->getRuleset(),
+            'fix' === $argv[4] ? new Fixer($tokenizer) : null,
+        );
+    }
+
+    $output = new BufferedOutput();
+    // Native reporter instances retain fingerprint collision state; each result gets a fresh one.
+    (new GitlabReporter())->display($output, $report, null, false);
+    echo $output->fetch();
+    exit(0 === $report->getTotalErrors() ? 0 : 1);
+} catch (Throwable $error) {
+    fwrite(STDERR, 'Twig evaluation worker: ' . $error->getMessage() . PHP_EOL);
+    exit(2);
+}