wip

composer.json

@@ -25,12 +25,12 @@
         "pestphp/pest-plugin-arch": "^4.0.2",
         "pestphp/pest-plugin-mutate": "^4.0.1",
         "pestphp/pest-plugin-profanity": "^4.2.1",
-        "phpunit/phpunit": "^12.5.22",
+        "phpunit/phpunit": "^12.5.23",
         "symfony/process": "^7.4.8|^8.0.8"
     },
     "conflict": {
         "filp/whoops": "<2.18.3",
-        "phpunit/phpunit": ">12.5.22",
+        "phpunit/phpunit": ">12.5.23",
         "sebastian/exporter": "<7.0.0",
         "webmozart/assert": "<1.11.0"
     },
@@ -123,6 +123,7 @@
                 "Pest\\Plugins\\Verbose",
                 "Pest\\Plugins\\Version",
                 "Pest\\Plugins\\Shard",
+                "Pest\\Plugins\\Tia",
                 "Pest\\Plugins\\Parallel"
             ]
         },

src/Bootstrappers/BootSubscribers.php

@@ -25,6 +25,16 @@ final readonly class BootSubscribers implements Bootstrapper
         Subscribers\EnsureIgnorableTestCasesAreIgnored::class,
         Subscribers\EnsureKernelDumpIsFlushed::class,
         Subscribers\EnsureTeamCityEnabled::class,
+        Subscribers\EnsureTiaCoverageIsRecorded::class,
+        Subscribers\EnsureTiaCoverageIsFlushed::class,
+        Subscribers\EnsureTiaResultsAreCollected::class,
+        Subscribers\EnsureTiaResultIsRecordedOnPassed::class,
+        Subscribers\EnsureTiaResultIsRecordedOnFailed::class,
+        Subscribers\EnsureTiaResultIsRecordedOnErrored::class,
+        Subscribers\EnsureTiaResultIsRecordedOnSkipped::class,
+        Subscribers\EnsureTiaResultIsRecordedOnIncomplete::class,
+        Subscribers\EnsureTiaResultIsRecordedOnRisky::class,
+        Subscribers\EnsureTiaAssertionsAreRecordedOnFinished::class,
     ];
 
     /**

src/Concerns/Testable.php

@@ -7,12 +7,15 @@ namespace Pest\Concerns;
 use Closure;
 use Pest\Exceptions\DatasetArgumentsMismatch;
 use Pest\Panic;
+use Pest\Plugins\Tia;
 use Pest\Preset;
+use Pest\Support\Container;
 use Pest\Support\ChainableClosure;
 use Pest\Support\ExceptionTrace;
 use Pest\Support\Reflection;
 use Pest\Support\Shell;
 use Pest\TestSuite;
+use PHPUnit\Framework\AssertionFailedError;
 use PHPUnit\Framework\Attributes\PostCondition;
 use PHPUnit\Framework\IncompleteTest;
 use PHPUnit\Framework\SkippedTest;
@@ -75,6 +78,12 @@ trait Testable
      */
     public bool $__ran = false;
 
+    /**
+     * Set when a `BeforeEachable` plugin returns a cached success result.
+     * Checked in `__runTest` and `tearDown` to skip body + cleanup.
+     */
+    private bool $__cachedPass = false;
+
     /**
      * The test's test closure.
      */
@@ -227,6 +236,45 @@ trait Testable
     {
         TestSuite::getInstance()->test = $this;
 
+        $this->__cachedPass = false;
+
+        /** @var Tia $tia */
+        $tia = Container::getInstance()->get(Tia::class);
+        $cached = $tia->getCachedResult(self::$__filename, $this::class.'::'.$this->name());
+
+        if ($cached !== null) {
+            if ($cached->isSuccess()) {
+                $this->__cachedPass = true;
+
+                return;
+            }
+
+            // Risky tests have no public PHPUnit hook to replay as-risky.
+            // Best available: short-circuit as a pass so the test doesn't
+            // misreport as a failure. Aggregate risky totals won't
+            // survive replay — accepted trade-off until PHPUnit grows a
+            // programmatic risky-marker API.
+            if ($cached->isRisky()) {
+                $this->__cachedPass = true;
+
+                return;
+            }
+
+            // Non-success: throw the matching PHPUnit exception. Runner
+            // catches it and marks the test with the correct status so
+            // skips, failures, incompletes and todos appear in output
+            // exactly as they did in the cached run.
+            if ($cached->isSkipped()) {
+                $this->markTestSkipped($cached->message());
+            }
+
+            if ($cached->isIncomplete()) {
+                $this->markTestIncomplete($cached->message());
+            }
+
+            throw new AssertionFailedError($cached->message() ?: 'Cached failure');
+        }
+
         $method = TestSuite::getInstance()->tests->get(self::$__filename)->getMethod($this->name());
 
         $description = $method->description;
@@ -302,6 +350,12 @@ trait Testable
      */
     protected function tearDown(...$arguments): void
     {
+        if ($this->__cachedPass) {
+            TestSuite::getInstance()->test = null;
+
+            return;
+        }
+
         $afterEach = TestSuite::getInstance()->afterEach->get(self::$__filename);
 
         if ($this->__afterEach instanceof Closure) {
@@ -327,6 +381,19 @@ trait Testable
      */
     private function __runTest(Closure $closure, ...$args): mixed
     {
+        if ($this->__cachedPass) {
+            // Feed the exact assertion count captured during the recorded
+            // run so Pest's "Tests: N passed (M assertions)" banner stays
+            // accurate on replay instead of collapsing to 1-per-test.
+            /** @var Tia $tia */
+            $tia = Container::getInstance()->get(Tia::class);
+            $assertions = $tia->getCachedAssertions($this::class.'::'.$this->name());
+
+            $this->addToAssertionCount($assertions > 0 ? $assertions : 1);
+
+            return null;
+        }
+
         $arguments = $this->__resolveTestArguments($args);
         $this->__ensureDatasetArgumentNameAndNumberMatches($arguments);
 

src/Configuration.php

@@ -119,6 +119,14 @@ final readonly class Configuration
         return new Browser\Configuration;
     }
 
+    /**
+     * Gets the TIA (Test Impact Analysis) configuration.
+     */
+    public function tia(): Plugins\Tia\Configuration
+    {
+        return new Plugins\Tia\Configuration;
+    }
+
     /**
      * Proxies calls to the uses method.
      *

src/Kernel.php

@@ -36,6 +36,7 @@ final readonly class Kernel
      */
     private const array BOOTSTRAPPERS = [
         Bootstrappers\BootOverrides::class,
+        Plugins\Tia\Bootstrapper::class,
         Bootstrappers\BootSubscribers::class,
         Bootstrappers\BootFiles::class,
         Bootstrappers\BootView::class,

src/Pest.php

@@ -6,7 +6,7 @@ namespace Pest;
 
 function version(): string
 {
-    return '4.6.2';
+    return '4.6.3';
 }
 
 function testDirectory(string $file = ''): string

src/Plugins/Tia/BaselineSync.php

@@ -0,0 +1,524 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Pest\Plugins\Tia;
+
+use Pest\Plugins\Tia;
+use Pest\Plugins\Tia\Contracts\State;
+use Symfony\Component\Console\Input\InputInterface;
+use Symfony\Component\Console\Output\OutputInterface;
+use Symfony\Component\Process\Process;
+
+/**
+ * Pulls a team-shared TIA baseline on the first `--tia` run so new
+ * contributors and fresh CI workspaces start in replay mode instead of
+ * paying the ~30s record cost.
+ *
+ * The baseline lives as a GitHub Release with a fixed tag containing two
+ * assets — the graph JSON and the coverage cache. The repo is inferred
+ * from `.git/config`'s `origin` remote, so no per-project configuration
+ * is required. Non-GitHub remotes silently opt out.
+ *
+ * Fetching is attempted in order:
+ *   1. `gh release download` — uses the user's existing GitHub auth,
+ *      works for private repos.
+ *   2. Plain HTTPS — public-repo fallback when `gh` isn't installed.
+ *
+ * Fingerprint validation happens back in `Tia::handleParent` after the
+ * blobs are written: a mismatched environment (different PHP version,
+ * composer.lock, etc.) discards the pulled baseline and falls through to
+ * the regular record path.
+ *
+ * @internal
+ */
+final class BaselineSync
+{
+    /**
+     * Conventional tag the CI recipe publishes under. Not configurable for
+     * MVP — if teams outgrow the convention, a `PEST_TIA_BASELINE_TAG` env
+     * var is the likely escape hatch.
+     */
+    private const string RELEASE_TAG = 'pest-tia-baseline';
+
+    /**
+     * Asset filenames within the release — mirror the state keys so the
+     * CI publisher and the sync consumer stay in lock-step.
+     */
+    private const string GRAPH_ASSET = Tia::KEY_GRAPH;
+
+    private const string COVERAGE_ASSET = Tia::KEY_COVERAGE_CACHE;
+
+    public function __construct(
+        private readonly State $state,
+        private readonly OutputInterface $output,
+        private readonly InputInterface $input,
+    ) {}
+
+    /**
+     * Attempts the full detect → prompt → download flow. Returns true when
+     * the graph blob was pulled and written to state. Coverage is best-
+     * effort: its absence doesn't fail the sync, since plain `--tia` (no
+     * `--coverage`) works fine without it.
+     */
+    public function fetchIfAvailable(string $projectRoot): bool
+    {
+        $repo = $this->detectGitHubRepo($projectRoot);
+
+        if ($repo === null) {
+            return false;
+        }
+
+        if (! $this->confirm($repo)) {
+            return false;
+        }
+
+        $this->output->writeln(sprintf(
+            '  <fg=cyan>TIA</> fetching baseline from <fg=white>%s</>…',
+            $repo,
+        ));
+
+        $graphJson = $this->download($repo, self::GRAPH_ASSET);
+
+        if ($graphJson === null) {
+            $this->output->writeln(
+                '  <fg=yellow>TIA</> no baseline published yet — recording locally.',
+            );
+
+            return false;
+        }
+
+        if (! $this->state->write(Tia::KEY_GRAPH, $graphJson)) {
+            return false;
+        }
+
+        // Coverage cache is optional. The baseline is useful even without
+        // it (plain `--tia` never needs it) so don't fail the whole sync
+        // just because this asset is missing or slow.
+        $coverageBin = $this->download($repo, self::COVERAGE_ASSET);
+
+        if ($coverageBin !== null) {
+            $this->state->write(Tia::KEY_COVERAGE_CACHE, $coverageBin);
+        }
+
+        $this->output->writeln(sprintf(
+            '  <fg=green>TIA</> baseline ready (%s).',
+            $this->formatSize(strlen($graphJson) + strlen($coverageBin ?? '')),
+        ));
+
+        return true;
+    }
+
+    /**
+     * Publishes the *local* baseline to GitHub Releases under the
+     * conventional tag, creating the release on first run or uploading
+     * into the existing one otherwise.
+     *
+     * Uploading from a developer workstation is intentionally discouraged
+     * — CI is the authoritative publisher because its environment is
+     * reproducible, its working tree is clean, and its result cache
+     * isn't contaminated by local flakiness. The prompt here defaults to
+     * *No* to keep this an explicit, opt-in action.
+     *
+     * Returns a CLI-style exit code so the caller can `exit()` on it.
+     */
+    public function publish(string $projectRoot): int
+    {
+        $graphBytes = $this->state->read(Tia::KEY_GRAPH);
+
+        if ($graphBytes === null) {
+            $this->output->writeln([
+                '',
+                '  <fg=red>TIA</> no local baseline to publish.',
+                '  Run <fg=cyan>./vendor/bin/pest --tia</> first to record one, then retry.',
+                '',
+            ]);
+
+            return 1;
+        }
+
+        $repo = $this->detectGitHubRepo($projectRoot);
+
+        if ($repo === null) {
+            $this->output->writeln([
+                '',
+                '  <fg=red>TIA</> cannot infer a GitHub repo from <fg=gray>.git/config</>.',
+                '  Publishing is supported only for GitHub-hosted projects.',
+                '',
+            ]);
+
+            return 1;
+        }
+
+        if (! $this->commandExists('gh')) {
+            $this->output->writeln([
+                '',
+                '  <fg=red>TIA</> publishing requires the <fg=cyan>gh</> CLI.',
+                '  Install: <fg=gray>https://cli.github.com</>',
+                '',
+            ]);
+
+            return 1;
+        }
+
+        $this->output->writeln([
+            '',
+            '  <fg=black;bg=yellow> WARNING </> Publishing local baselines is discouraged.',
+            '',
+            '  Local runs can bake flaky results or dirty working-tree state into the',
+            '  baseline, which your team then replays. CI-published baselines are safer.',
+            '  See <fg=gray>https://pestphp.com/docs/tia/ci</> for the recommended workflow.',
+            '',
+        ]);
+
+        if (! $this->confirmPublish($repo)) {
+            $this->output->writeln('  <fg=yellow>TIA</> publish cancelled.');
+
+            return 0;
+        }
+
+        $tmpDir = sys_get_temp_dir().DIRECTORY_SEPARATOR.'pest-tia-publish-'.bin2hex(random_bytes(4));
+
+        if (! @mkdir($tmpDir, 0755, true) && ! is_dir($tmpDir)) {
+            $this->output->writeln('  <fg=red>TIA</> failed to create temp dir for upload.');
+
+            return 1;
+        }
+
+        $graphPath = $tmpDir.DIRECTORY_SEPARATOR.self::GRAPH_ASSET;
+
+        if (@file_put_contents($graphPath, $graphBytes) === false) {
+            $this->cleanup($tmpDir);
+
+            return 1;
+        }
+
+        $filesToUpload = [$graphPath];
+
+        $coverageBytes = $this->state->read(Tia::KEY_COVERAGE_CACHE);
+
+        if ($coverageBytes !== null) {
+            $coveragePath = $tmpDir.DIRECTORY_SEPARATOR.self::COVERAGE_ASSET;
+
+            if (@file_put_contents($coveragePath, $coverageBytes) !== false) {
+                $filesToUpload[] = $coveragePath;
+            }
+        }
+
+        $this->output->writeln(sprintf(
+            '  <fg=cyan>TIA</> publishing to <fg=white>%s</> (tag <fg=white>%s</>)…',
+            $repo,
+            self::RELEASE_TAG,
+        ));
+
+        $exitCode = $this->ghReleaseUploadOrCreate($repo, $filesToUpload);
+        $this->cleanup($tmpDir);
+
+        if ($exitCode !== 0) {
+            $this->output->writeln('  <fg=red>TIA</> <fg=cyan>gh release</> failed.');
+
+            return $exitCode;
+        }
+
+        $this->output->writeln(sprintf(
+            '  <fg=green>TIA</> baseline published (%s).',
+            $this->formatSize(strlen($graphBytes) + ($coverageBytes === null ? 0 : strlen($coverageBytes))),
+        ));
+
+        return 0;
+    }
+
+    /**
+     * Uploads into the existing release if present, falls back to
+     * creating the release with the assets attached on first run.
+     *
+     * @param  array<int, string>  $files
+     */
+    private function ghReleaseUploadOrCreate(string $repo, array $files): int
+    {
+        $uploadArgs = ['gh', 'release', 'upload', self::RELEASE_TAG, ...$files, '-R', $repo, '--clobber'];
+        $upload = new Process($uploadArgs);
+        $upload->setTimeout(300.0);
+        $upload->run(function (string $_, string $buffer): void {
+            $this->output->write($buffer);
+        });
+
+        if ($upload->isSuccessful()) {
+            return 0;
+        }
+
+        // Release likely doesn't exist yet — create it, attaching the files.
+        $createArgs = [
+            'gh', 'release', 'create', self::RELEASE_TAG,
+            ...$files,
+            '-R', $repo,
+            '--title', 'Pest TIA baseline',
+            '--notes', 'Machine-generated baseline for Pest TIA. Do not edit manually.',
+        ];
+        $create = new Process($createArgs);
+        $create->setTimeout(300.0);
+        $create->run(function (string $_, string $buffer): void {
+            $this->output->write($buffer);
+        });
+
+        return $create->isSuccessful() ? 0 : 1;
+    }
+
+    private function confirmPublish(string $repo): bool
+    {
+        if (! $this->isTerminal()) {
+            return false;
+        }
+
+        $this->output->writeln(sprintf(
+            '  Publish to <fg=white>%s</> (tag <fg=white>%s</>)? <fg=gray>[y/N]</>',
+            $repo,
+            self::RELEASE_TAG,
+        ));
+
+        $handle = @fopen('php://stdin', 'r');
+
+        if ($handle === false) {
+            return false;
+        }
+
+        $line = fgets($handle);
+        fclose($handle);
+
+        if ($line === false) {
+            return false;
+        }
+
+        // Unlike the fetch prompt, this one defaults to *No*. Empty input
+        // or anything other than an explicit "y"/"yes" cancels.
+        $line = strtolower(trim($line));
+
+        return $line === 'y' || $line === 'yes';
+    }
+
+    /**
+     * Parses `.git/config` for the `origin` remote and extracts
+     * `org/repo`. Supports the two URL flavours git emits out of the box.
+     * Non-GitHub remotes (GitLab, Bitbucket, self-hosted) → null, which
+     * silently opts the repo out of auto-sync.
+     */
+    private function detectGitHubRepo(string $projectRoot): ?string
+    {
+        $gitConfig = $projectRoot.DIRECTORY_SEPARATOR.'.git'.DIRECTORY_SEPARATOR.'config';
+
+        if (! is_file($gitConfig)) {
+            return null;
+        }
+
+        $content = @file_get_contents($gitConfig);
+
+        if ($content === false) {
+            return null;
+        }
+
+        // Find the `[remote "origin"]` section and the first `url` line
+        // inside it. Tolerates INI whitespace quirks (tabs, CRLF).
+        if (preg_match('/\[remote "origin"\][^\[]*?url\s*=\s*(\S+)/s', $content, $match) !== 1) {
+            return null;
+        }
+
+        $url = $match[1];
+
+        // SSH: git@github.com:org/repo(.git)
+        if (preg_match('#^git@github\.com:([\w.-]+/[\w.-]+?)(?:\.git)?$#', $url, $m) === 1) {
+            return $m[1];
+        }
+
+        // HTTPS: https://github.com/org/repo(.git) (optional trailing slash)
+        if (preg_match('#^https?://github\.com/([\w.-]+/[\w.-]+?)(?:\.git)?/?$#', $url, $m) === 1) {
+            return $m[1];
+        }
+
+        return null;
+    }
+
+    /**
+     * One-shot Y/n prompt. Defaults to Y. In non-interactive shells (CI,
+     * piped input) returns false so scripted runs never hang waiting for
+     * input.
+     */
+    private function confirm(string $repo): bool
+    {
+        if (! $this->isTerminal()) {
+            return false;
+        }
+
+        $this->output->writeln('');
+        $this->output->writeln(sprintf(
+            '  <fg=cyan>TIA</> no local cache — fetch baseline from <fg=white>%s</>? <fg=gray>[Y/n]</>',
+            $repo,
+        ));
+
+        $handle = @fopen('php://stdin', 'r');
+
+        if ($handle === false) {
+            return false;
+        }
+
+        $line = fgets($handle);
+        fclose($handle);
+
+        if ($line === false) {
+            return false;
+        }
+
+        $line = strtolower(trim($line));
+
+        return $line === '' || $line === 'y' || $line === 'yes';
+    }
+
+    /**
+     * Real-TTY check for STDIN. Symfony's `isInteractive()` defaults to true
+     * unless `--no-interaction` is explicitly passed, which would make
+     * scripted invocations (CI, pipes, subshells) hang at a prompt nobody
+     * sees. Combining both signals is the safe default.
+     */
+    private function isTerminal(): bool
+    {
+        if (! $this->input->isInteractive()) {
+            return false;
+        }
+
+        if (! defined('STDIN')) {
+            return false;
+        }
+
+        if (function_exists('posix_isatty')) {
+            return @posix_isatty(STDIN) === true;
+        }
+
+        if (function_exists('stream_isatty')) {
+            return @stream_isatty(STDIN) === true;
+        }
+
+        return false;
+    }
+
+    /**
+     * Tries `gh` first (handles private repos + rate limiting via the
+     * user's GitHub auth), falls through to public HTTPS. Returns the
+     * raw asset bytes, or null on any failure.
+     */
+    private function download(string $repo, string $asset): ?string
+    {
+        $viaGh = $this->downloadViaGh($repo, $asset);
+
+        if ($viaGh !== null) {
+            return $viaGh;
+        }
+
+        return $this->downloadViaHttps($repo, $asset);
+    }
+
+    private function downloadViaGh(string $repo, string $asset): ?string
+    {
+        if (! $this->commandExists('gh')) {
+            return null;
+        }
+
+        $tmpDir = sys_get_temp_dir().DIRECTORY_SEPARATOR.'pest-tia-'.bin2hex(random_bytes(4));
+
+        if (! @mkdir($tmpDir, 0755, true) && ! is_dir($tmpDir)) {
+            return null;
+        }
+
+        $process = new Process([
+            'gh', 'release', 'download', self::RELEASE_TAG,
+            '-R', $repo,
+            '-p', $asset,
+            '-D', $tmpDir,
+            '--clobber',
+        ]);
+        $process->setTimeout(120.0);
+        $process->run();
+
+        $payload = null;
+
+        if ($process->isSuccessful()) {
+            $path = $tmpDir.DIRECTORY_SEPARATOR.$asset;
+
+            if (is_file($path)) {
+                $content = @file_get_contents($path);
+                $payload = $content === false ? null : $content;
+            }
+        }
+
+        $this->cleanup($tmpDir);
+
+        return $payload;
+    }
+
+    private function downloadViaHttps(string $repo, string $asset): ?string
+    {
+        $url = sprintf(
+            'https://github.com/%s/releases/download/%s/%s',
+            $repo,
+            self::RELEASE_TAG,
+            $asset,
+        );
+
+        $ctx = stream_context_create([
+            'http' => [
+                'timeout' => 120,
+                'follow_location' => 1,
+                'ignore_errors' => false,
+            ],
+        ]);
+
+        $content = @file_get_contents($url, false, $ctx);
+
+        return $content === false ? null : $content;
+    }
+
+    private function commandExists(string $cmd): bool
+    {
+        $probe = new Process(['command', '-v', $cmd]);
+        $probe->run();
+
+        if ($probe->isSuccessful()) {
+            return true;
+        }
+
+        $which = new Process(['which', $cmd]);
+        $which->run();
+
+        return $which->isSuccessful();
+    }
+
+    private function cleanup(string $dir): void
+    {
+        if (! is_dir($dir)) {
+            return;
+        }
+
+        $entries = glob($dir.DIRECTORY_SEPARATOR.'*');
+
+        if ($entries !== false) {
+            foreach ($entries as $entry) {
+                if (is_file($entry)) {
+                    @unlink($entry);
+                }
+            }
+        }
+
+        @rmdir($dir);
+    }
+
+    private function formatSize(int $bytes): string
+    {
+        if ($bytes >= 1024 * 1024) {
+            return sprintf('%.1f MB', $bytes / 1024 / 1024);
+        }
+
+        if ($bytes >= 1024) {
+            return sprintf('%.1f KB', $bytes / 1024);
+        }
+
+        return $bytes.' B';
+    }
+}

src/Plugins/Tia/Bootstrapper.php

@@ -0,0 +1,47 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Pest\Plugins\Tia;
+
+use Pest\Contracts\Bootstrapper as BootstrapperContract;
+use Pest\Plugins\Tia\Contracts\State;
+use Pest\Support\Container;
+
+/**
+ * Plugin-level container registrations for TIA. Runs as part of Kernel's
+ * bootstrapper chain so Tia's own service graph is set up without Kernel
+ * having to know about any of its internals.
+ *
+ * Most Tia services (`Recorder`, `CoverageCollector`, `WatchPatterns`,
+ * `ResultCollector`, `BaselineSync`) are auto-buildable — Pest's container
+ * resolves them lazily via constructor reflection. The only service that
+ * requires an explicit binding is the `State` contract, because the
+ * filesystem implementation needs a root-directory string that reflection
+ * can't infer.
+ *
+ * @internal
+ */
+final readonly class Bootstrapper implements BootstrapperContract
+{
+    public function __construct(private Container $container) {}
+
+    public function boot(): void
+    {
+        $this->container->add(State::class, new FileState($this->tempDir()));
+    }
+
+    /**
+     * Resolve Pest's `.temp/` directory relative to this file so TIA's
+     * caches share the same location as the rest of Pest's transient
+     * state (PHPUnit result cache, coverage PHP dumps, etc.).
+     */
+    private function tempDir(): string
+    {
+        return __DIR__
+            .DIRECTORY_SEPARATOR.'..'
+            .DIRECTORY_SEPARATOR.'..'
+            .DIRECTORY_SEPARATOR.'..'
+            .DIRECTORY_SEPARATOR.'.temp';
+    }
+}

src/Plugins/Tia/ChangedFiles.php

@@ -0,0 +1,339 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Pest\Plugins\Tia;
+
+use Symfony\Component\Process\Process;
+
+/**
+ * Detects files that changed between the last recorded TIA run and the
+ * current working tree.
+ *
+ * Strategy:
+ *   1. If we have a `recordedAtSha`, `git diff <sha>..HEAD` captures committed
+ *      changes on top of the recording point.
+ *   2. `git status --short` captures unstaged + staged + untracked changes on
+ *      top of that.
+ *
+ * We return relative paths to the project root. Deletions are included so the
+ * caller can decide whether to invalidate: a deleted source file may still
+ * appear in the graph and should mark its dependents as affected.
+ *
+ * @internal
+ */
+final readonly class ChangedFiles
+{
+    public function __construct(private string $projectRoot) {}
+
+    /**
+     * @return array<int, string>|null `null` when git is unavailable, or when
+     *                                 the recorded SHA is no longer reachable
+     *                                 from HEAD (rebase / force-push) — in
+     *                                 that case the graph should be rebuilt.
+     */
+    /**
+     * Removes files whose current content hash matches the snapshot from the
+     * last `--tia` run. Used to ignore "dirty but unchanged" files — a file
+     * that git still reports as modified but whose content is bit-identical
+     * to the previous TIA invocation.
+     *
+     * @param  array<int, string>  $files          project-relative paths.
+     * @param  array<string, string>  $lastRunTree  path → content hash from last run.
+     * @return array<int, string>
+     */
+    public function filterUnchangedSinceLastRun(array $files, array $lastRunTree): array
+    {
+        if ($lastRunTree === []) {
+            return $files;
+        }
+
+        // Union: `$files` (what git currently reports) + every path that was
+        // dirty last run. The second set matters for reverts — when a user
+        // undoes a local edit, the file matches HEAD again and git reports
+        // it clean, so it would never enter `$files`. But it has genuinely
+        // changed vs the snapshot we captured during the bad run, so it
+        // must be checked.
+        $candidates = array_fill_keys($files, true);
+
+        foreach (array_keys($lastRunTree) as $snapshotted) {
+            $candidates[$snapshotted] = true;
+        }
+
+        $remaining = [];
+
+        foreach (array_keys($candidates) as $file) {
+            $snapshot = $lastRunTree[$file] ?? null;
+            $absolute = $this->projectRoot.DIRECTORY_SEPARATOR.$file;
+            $exists = is_file($absolute);
+
+            if ($snapshot === null) {
+                // File wasn't in last-run tree at all — trust git's signal.
+                $remaining[] = $file;
+
+                continue;
+            }
+
+            if (! $exists) {
+                // Missing now. If the snapshot recorded it as absent too
+                // (sentinel ''), state is identical to last run — unchanged.
+                // Otherwise it was present last run and got deleted since.
+                if ($snapshot !== '') {
+                    $remaining[] = $file;
+                }
+
+                continue;
+            }
+
+            $hash = @hash_file('xxh128', $absolute);
+
+            if ($hash === false || $hash !== $snapshot) {
+                $remaining[] = $file;
+            }
+        }
+
+        return $remaining;
+    }
+
+    /**
+     * Computes content hashes for the given project-relative files. Used to
+     * snapshot the working tree after a successful run so the next run can
+     * detect which files are actually different.
+     *
+     * @param  array<int, string>  $files
+     * @return array<string, string>  path → xxh128 content hash
+     */
+    public function snapshotTree(array $files): array
+    {
+        $out = [];
+
+        foreach ($files as $file) {
+            $absolute = $this->projectRoot.DIRECTORY_SEPARATOR.$file;
+
+            if (! is_file($absolute)) {
+                // Record the deletion with an empty-string sentinel so the
+                // next run recognises "still deleted" as unchanged rather
+                // than re-flagging the file as a fresh change.
+                $out[$file] = '';
+
+                continue;
+            }
+
+            $hash = @hash_file('xxh128', $absolute);
+
+            if ($hash !== false) {
+                $out[$file] = $hash;
+            }
+        }
+
+        return $out;
+    }
+
+    /**
+     * @return array<int, string>|null `null` when git is unavailable, or when
+     *                                 the recorded SHA is no longer reachable
+     *                                 from HEAD (rebase / force-push).
+     */
+    public function since(?string $sha): ?array
+    {
+        if (! $this->gitAvailable()) {
+            return null;
+        }
+
+        $files = [];
+
+        if ($sha !== null && $sha !== '') {
+            if (! $this->shaIsReachable($sha)) {
+                return null;
+            }
+
+            $files = array_merge($files, $this->diffSinceSha($sha));
+        }
+
+        $files = array_merge($files, $this->workingTreeChanges());
+
+        // Normalise + dedupe, filtering out paths that can never belong to the
+        // graph: vendor (caught by the fingerprint instead), cache dirs, and
+        // anything starting with a dot we don't care about.
+        $unique = [];
+
+        foreach ($files as $file) {
+            if ($file === '') {
+                continue;
+            }
+            if ($this->shouldIgnore($file)) {
+                continue;
+            }
+            $unique[$file] = true;
+        }
+
+        return array_keys($unique);
+    }
+
+    private function shouldIgnore(string $path): bool
+    {
+        static $prefixes = [
+            '.pest/',
+            '.phpunit.cache/',
+            '.phpunit.result.cache',
+            'vendor/',
+            'node_modules/',
+        ];
+
+        foreach ($prefixes as $prefix) {
+            if (str_starts_with($path, (string) $prefix)) {
+                return true;
+            }
+        }
+
+        return false;
+    }
+
+    public function currentBranch(): ?string
+    {
+        if (! $this->gitAvailable()) {
+            return null;
+        }
+
+        $process = new Process(['git', 'rev-parse', '--abbrev-ref', 'HEAD'], $this->projectRoot);
+        $process->run();
+
+        if (! $process->isSuccessful()) {
+            return null;
+        }
+
+        $branch = trim($process->getOutput());
+
+        return $branch === '' || $branch === 'HEAD' ? null : $branch;
+    }
+
+    public function gitAvailable(): bool
+    {
+        $process = new Process(['git', 'rev-parse', '--git-dir'], $this->projectRoot);
+        $process->run();
+
+        return $process->isSuccessful();
+    }
+
+    private function shaIsReachable(string $sha): bool
+    {
+        $process = new Process(
+            ['git', 'merge-base', '--is-ancestor', $sha, 'HEAD'],
+            $this->projectRoot,
+        );
+        $process->run();
+
+        // Exit 0 → ancestor; 1 → not ancestor; anything else → git error
+        // (e.g. unknown commit after a rebase/gc). Treat non-zero as
+        // "unreachable" and force a rebuild.
+        return $process->getExitCode() === 0;
+    }
+
+    /**
+     * @return array<int, string>
+     */
+    private function diffSinceSha(string $sha): array
+    {
+        $process = new Process(
+            ['git', 'diff', '--name-only', $sha.'..HEAD'],
+            $this->projectRoot,
+        );
+        $process->run();
+
+        if (! $process->isSuccessful()) {
+            return [];
+        }
+
+        return $this->splitLines($process->getOutput());
+    }
+
+    /**
+     * @return array<int, string>
+     */
+    private function workingTreeChanges(): array
+    {
+        // `-z` produces NUL-terminated records with no path quoting, so paths
+        // that contain spaces, tabs, unicode or other special characters
+        // are passed through verbatim. Without `-z`, git wraps such paths in
+        // quotes with backslash escapes, which would corrupt our lookup keys.
+        //
+        // Record format: `XY <SP> <path> <NUL>` for most entries, and
+        // `R  <new> <NUL> <orig> <NUL>` for renames/copies (two NUL-separated
+        // fields).
+        $process = new Process(
+            ['git', 'status', '--porcelain', '-z', '--untracked-files=all'],
+            $this->projectRoot,
+        );
+        $process->run();
+
+        if (! $process->isSuccessful()) {
+            return [];
+        }
+
+        $output = $process->getOutput();
+
+        if ($output === '') {
+            return [];
+        }
+
+        $records = explode("\x00", rtrim($output, "\x00"));
+        $files = [];
+        $count = count($records);
+
+        for ($i = 0; $i < $count; $i++) {
+            $record = $records[$i];
+
+            if (strlen($record) < 4) {
+                continue;
+            }
+
+            $status = substr($record, 0, 2);
+            $path = substr($record, 3);
+
+            // Renames/copies emit two records: the new path first, then the
+            // original. Consume both.
+            if ($status[0] === 'R' || $status[0] === 'C') {
+                $files[] = $path;
+
+                if (isset($records[$i + 1]) && $records[$i + 1] !== '') {
+                    $files[] = $records[$i + 1];
+                    $i++;
+                }
+
+                continue;
+            }
+
+            $files[] = $path;
+        }
+
+        return $files;
+    }
+
+    public function currentSha(): ?string
+    {
+        if (! $this->gitAvailable()) {
+            return null;
+        }
+
+        $process = new Process(['git', 'rev-parse', 'HEAD'], $this->projectRoot);
+        $process->run();
+
+        if (! $process->isSuccessful()) {
+            return null;
+        }
+
+        $sha = trim($process->getOutput());
+
+        return $sha === '' ? null : $sha;
+    }
+
+    /**
+     * @return array<int, string>
+     */
+    private function splitLines(string $output): array
+    {
+        $lines = preg_split('/\R+/', trim($output), flags: PREG_SPLIT_NO_EMPTY);
+
+        return $lines === false ? [] : $lines;
+    }
+}

src/Plugins/Tia/Configuration.php

@@ -0,0 +1,42 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Pest\Plugins\Tia;
+
+use Pest\Support\Container;
+
+/**
+ * User-facing TIA configuration, returned by `pest()->tia()`.
+ *
+ * Usage in `tests/Pest.php`:
+ *
+ *     pest()->tia()->watch([
+ *         'resources/js/**\/*.tsx' => 'tests/Browser',
+ *         'public/build/**\/*'     => 'tests/Browser',
+ *     ]);
+ *
+ * Patterns are merged with the built-in defaults (config, routes, views,
+ * frontend assets, migrations). Duplicate glob keys overwrite the default
+ * mapping so users can redirect a pattern to a narrower directory.
+ *
+ * @internal
+ */
+final class Configuration
+{
+    /**
+     * Adds watch-pattern → test-directory mappings that supplement (or
+     * override) the built-in defaults.
+     *
+     * @param  array<string, string>  $patterns  glob → project-relative test dir
+     * @return $this
+     */
+    public function watch(array $patterns): self
+    {
+        /** @var WatchPatterns $watchPatterns */
+        $watchPatterns = Container::getInstance()->get(WatchPatterns::class);
+        $watchPatterns->add($patterns);
+
+        return $this;
+    }
+}

src/Plugins/Tia/Contracts/State.php

@@ -0,0 +1,48 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Pest\Plugins\Tia\Contracts;
+
+/**
+ * Storage contract for TIA's persistent state (graph, baselines, affected
+ * set, worker partials, coverage snapshots). Modelled as a flat key/value
+ * store of raw byte blobs so implementations can sit on top of whatever
+ * backend fits — a directory, a shared cache, a remote object store — and
+ * TIA's logic stays identical.
+ *
+ * @internal
+ */
+interface State
+{
+    /**
+     * Returns the stored blob for `$key`, or `null` when the key is unset
+     * or cannot be read.
+     */
+    public function read(string $key): ?string;
+
+    /**
+     * Atomically stores `$content` under `$key`. Existing value (if any) is
+     * replaced. Implementations SHOULD guarantee that concurrent readers
+     * never observe partial writes.
+     */
+    public function write(string $key, string $content): bool;
+
+    /**
+     * Removes `$key`. Returns true whether or not the key existed beforehand
+     * — callers should treat a `true` result as "the key is now absent",
+     * not "the key was present and has been removed."
+     */
+    public function delete(string $key): bool;
+
+    public function exists(string $key): bool;
+
+    /**
+     * Returns every key whose name starts with `$prefix`. Used to collect
+     * paratest worker partials (`tia-worker-<token>.json`, etc.) without
+     * exposing backend-specific glob semantics.
+     *
+     * @return list<string>
+     */
+    public function keysWithPrefix(string $prefix): array;
+}

src/Plugins/Tia/CoverageCollector.php

@@ -0,0 +1,152 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Pest\Plugins\Tia;
+
+use PHPUnit\Runner\CodeCoverage as PhpUnitCodeCoverage;
+use ReflectionClass;
+use Throwable;
+
+/**
+ * Extracts per-test file coverage from PHPUnit's shared `CodeCoverage`
+ * instance. Used when TIA piggybacks on `--coverage` instead of starting
+ * its own driver session — both share the same PCOV / Xdebug state, so
+ * running two recorders in parallel would corrupt each other's data.
+ *
+ * PHPUnit tags every coverage sample with the current test's id
+ * (`$test->valueObjectForEvents()->id()`, e.g. `Foo\BarTest::baz`). The
+ * per-file / per-line coverage map therefore already carries everything
+ * we need to rebuild TIA edges at the end of the run.
+ *
+ * @internal
+ */
+final class CoverageCollector
+{
+    /**
+     * Cached `className → test file` lookups. Class reflection is cheap
+     * individually but the record run can visit tens of thousands of
+     * samples, so the cache matters.
+     *
+     * @var array<string, string|null>
+     */
+    private array $classFileCache = [];
+
+    /**
+     * Rebuilds the same `absolute test file → list<absolute source file>`
+     * shape that `Recorder::perTestFiles()` exposes, so callers can treat
+     * the two collectors interchangeably when feeding the graph.
+     *
+     * @return array<string, array<int, string>>
+     */
+    public function perTestFiles(): array
+    {
+        if (! PhpUnitCodeCoverage::instance()->isActive()) {
+            return [];
+        }
+
+        try {
+            $lineCoverage = PhpUnitCodeCoverage::instance()
+                ->codeCoverage()
+                ->getData()
+                ->lineCoverage();
+        } catch (Throwable) {
+            return [];
+        }
+
+        /** @var array<string, array<string, true>> $edges */
+        $edges = [];
+
+        foreach ($lineCoverage as $sourceFile => $lines) {
+            // Collect the set of tests that hit any line in this file once,
+            // then emit one edge per (testFile, sourceFile) pair. Walking
+            // the lines per test would re-resolve the test file repeatedly.
+            $testIds = [];
+
+            foreach ($lines as $hits) {
+                if ($hits === null) {
+                    continue;
+                }
+
+                foreach ($hits as $id) {
+                    $testIds[$id] = true;
+                }
+            }
+
+            foreach (array_keys($testIds) as $testId) {
+                $testFile = $this->testIdToFile($testId);
+
+                if ($testFile === null) {
+                    continue;
+                }
+
+                $edges[$testFile][$sourceFile] = true;
+            }
+        }
+
+        $out = [];
+
+        foreach ($edges as $testFile => $sources) {
+            $out[$testFile] = array_keys($sources);
+        }
+
+        return $out;
+    }
+
+    public function reset(): void
+    {
+        $this->classFileCache = [];
+    }
+
+    private function testIdToFile(string $testId): ?string
+    {
+        // PHPUnit's test id is `ClassName::methodName` with an optional
+        // `#dataSetName` suffix for data-provider runs. Strip the dataset
+        // part — we only need the class.
+        $hash = strpos($testId, '#');
+        $identifier = $hash === false ? $testId : substr($testId, 0, $hash);
+
+        if (! str_contains($identifier, '::')) {
+            return null;
+        }
+
+        [$className] = explode('::', $identifier, 2);
+
+        if (array_key_exists($className, $this->classFileCache)) {
+            return $this->classFileCache[$className];
+        }
+
+        $file = $this->resolveClassFile($className);
+        $this->classFileCache[$className] = $file;
+
+        return $file;
+    }
+
+    private function resolveClassFile(string $className): ?string
+    {
+        if (! class_exists($className, false)) {
+            return null;
+        }
+
+        $reflection = new ReflectionClass($className);
+
+        // Pest's eval'd test classes expose the original `.php` path on a
+        // static `$__filename`. The eval'd class itself has no file of its
+        // own, so prefer this property when present.
+        if ($reflection->hasProperty('__filename')) {
+            $property = $reflection->getProperty('__filename');
+
+            if ($property->isStatic()) {
+                $value = $property->getValue();
+
+                if (is_string($value)) {
+                    return $value;
+                }
+            }
+        }
+
+        $file = $reflection->getFileName();
+
+        return is_string($file) ? $file : null;
+    }
+}

src/Plugins/Tia/CoverageMerger.php

@@ -0,0 +1,186 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Pest\Plugins\Tia;
+
+use Pest\Plugins\Tia;
+use Pest\Plugins\Tia\Contracts\State;
+use Pest\Support\Container;
+use SebastianBergmann\CodeCoverage\CodeCoverage;
+use Throwable;
+
+/**
+ * Merges the current run's PHPUnit coverage into a cached full-suite
+ * snapshot so `--tia --coverage` can produce a complete report after
+ * executing only the affected tests.
+ *
+ * Invoked from `Pest\Support\Coverage::report()` right before the coverage
+ * file is consumed. A marker dropped by the `Tia` plugin gates the
+ * behaviour — plain `--coverage` runs (no `--tia`) leave the marker absent
+ * and therefore keep their existing semantics.
+ *
+ * Algorithm
+ * ---------
+ * The PHPUnit coverage PHP file unserialises to a `CodeCoverage` object.
+ * Its `ProcessedCodeCoverageData` stores, per source file, per line, the
+ * list of test IDs that covered that line. We:
+ *
+ *   1. Load the cached snapshot from `State` (serialised bytes).
+ *   2. Strip every test id that re-ran this time from the cached map —
+ *      the tests that ran now are the ones whose attribution is fresh.
+ *   3. Merge the current run into the stripped cached snapshot via
+ *      `CodeCoverage::merge()`.
+ *   4. Write the merged result back to the report path (so Pest's report
+ *      generator sees the full suite) and back into `State` (for the
+ *      next invocation).
+ *
+ * If no cache exists yet (first `--tia --coverage` run on this machine)
+ * we serialise the current object and save it — nothing to merge yet.
+ *
+ * @internal
+ */
+final class CoverageMerger
+{
+    public static function applyIfMarked(string $reportPath): void
+    {
+        $state = self::state();
+
+        if ($state === null || ! $state->exists(Tia::KEY_COVERAGE_MARKER)) {
+            return;
+        }
+
+        $state->delete(Tia::KEY_COVERAGE_MARKER);
+
+        $cachedBytes = $state->read(Tia::KEY_COVERAGE_CACHE);
+
+        if ($cachedBytes === null) {
+            // First `--tia --coverage` run: nothing cached yet, so the
+            // current file already represents the full suite. Capture it
+            // verbatim (as serialised bytes) for next time.
+            $current = self::requireCoverage($reportPath);
+
+            if ($current !== null) {
+                $state->write(Tia::KEY_COVERAGE_CACHE, serialize($current));
+            }
+
+            return;
+        }
+
+        $cached = self::unserializeCoverage($cachedBytes);
+        $current = self::requireCoverage($reportPath);
+
+        if ($cached === null || $current === null) {
+            return;
+        }
+
+        self::stripCurrentTestsFromCached($cached, $current);
+
+        $cached->merge($current);
+
+        $serialised = serialize($cached);
+
+        // Write back to the PHPUnit-style `.cov` path so the report reader
+        // can `require` it, and to the state cache for the next run.
+        @file_put_contents(
+            $reportPath,
+            "<?php return unserialize(".var_export($serialised, true).");\n",
+        );
+        $state->write(Tia::KEY_COVERAGE_CACHE, $serialised);
+    }
+
+    /**
+     * Removes from `$cached`'s per-line test attribution any test id that
+     * appears in `$current`. Those tests just ran, so the fresh slice is
+     * authoritative — keeping stale attribution in the cache would claim
+     * a test still covers a line it no longer touches.
+     */
+    private static function stripCurrentTestsFromCached(CodeCoverage $cached, CodeCoverage $current): void
+    {
+        $currentIds = self::collectTestIds($current);
+
+        if ($currentIds === []) {
+            return;
+        }
+
+        $cachedData = $cached->getData();
+        $lineCoverage = $cachedData->lineCoverage();
+
+        foreach ($lineCoverage as $file => $lines) {
+            foreach ($lines as $line => $ids) {
+                if ($ids === null || $ids === []) {
+                    continue;
+                }
+
+                $filtered = array_values(array_diff($ids, $currentIds));
+
+                if ($filtered !== $ids) {
+                    $lineCoverage[$file][$line] = $filtered;
+                }
+            }
+        }
+
+        $cachedData->setLineCoverage($lineCoverage);
+    }
+
+    /**
+     * @return array<int, string>
+     */
+    private static function collectTestIds(CodeCoverage $coverage): array
+    {
+        $ids = [];
+
+        foreach ($coverage->getData()->lineCoverage() as $lines) {
+            foreach ($lines as $hits) {
+                if ($hits === null) {
+                    continue;
+                }
+
+                foreach ($hits as $id) {
+                    $ids[$id] = true;
+                }
+            }
+        }
+
+        return array_keys($ids);
+    }
+
+    private static function state(): ?State
+    {
+        try {
+            $state = Container::getInstance()->get(State::class);
+        } catch (Throwable) {
+            return null;
+        }
+
+        return $state instanceof State ? $state : null;
+    }
+
+    private static function requireCoverage(string $reportPath): ?CodeCoverage
+    {
+        if (! is_file($reportPath)) {
+            return null;
+        }
+
+        try {
+            /** @var mixed $value */
+            $value = require $reportPath;
+        } catch (Throwable) {
+            return null;
+        }
+
+        return $value instanceof CodeCoverage ? $value : null;
+    }
+
+    private static function unserializeCoverage(string $bytes): ?CodeCoverage
+    {
+        try {
+            /** @var mixed $value */
+            $value = @unserialize($bytes);
+        } catch (Throwable) {
+            return null;
+        }
+
+        return $value instanceof CodeCoverage ? $value : null;
+    }
+}

src/Plugins/Tia/FileState.php

@@ -0,0 +1,150 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Pest\Plugins\Tia;
+
+use Pest\Plugins\Tia\Contracts\State;
+
+/**
+ * Filesystem-backed implementation of the TIA `State` contract. Each key
+ * maps verbatim to a file name under `$rootDir`, so existing `.temp/*.json`
+ * layouts are preserved exactly.
+ *
+ * The root directory is created lazily on first write — callers don't have
+ * to pre-provision it, and reads against a missing directory simply return
+ * `null` rather than throwing.
+ *
+ * @internal
+ */
+final class FileState implements State
+{
+    /**
+     * Configured root. May not exist on disk yet; resolved + created on
+     * the first write. Keeping the raw string lets the instance be built
+     * before Pest's temp dir has been materialised.
+     */
+    private readonly string $rootDir;
+
+    public function __construct(string $rootDir)
+    {
+        $this->rootDir = rtrim($rootDir, DIRECTORY_SEPARATOR);
+    }
+
+    public function read(string $key): ?string
+    {
+        $path = $this->pathFor($key);
+
+        if (! is_file($path)) {
+            return null;
+        }
+
+        $bytes = @file_get_contents($path);
+
+        return $bytes === false ? null : $bytes;
+    }
+
+    public function write(string $key, string $content): bool
+    {
+        if (! $this->ensureRoot()) {
+            return false;
+        }
+
+        $path = $this->pathFor($key);
+        $tmp = $path.'.'.bin2hex(random_bytes(4)).'.tmp';
+
+        if (@file_put_contents($tmp, $content) === false) {
+            return false;
+        }
+
+        // Atomic rename — on POSIX filesystems this is a single-step
+        // replacement, so concurrent readers never see a half-written file.
+        if (! @rename($tmp, $path)) {
+            @unlink($tmp);
+
+            return false;
+        }
+
+        return true;
+    }
+
+    public function delete(string $key): bool
+    {
+        $path = $this->pathFor($key);
+
+        if (! is_file($path)) {
+            return true;
+        }
+
+        return @unlink($path);
+    }
+
+    public function exists(string $key): bool
+    {
+        return is_file($this->pathFor($key));
+    }
+
+    public function keysWithPrefix(string $prefix): array
+    {
+        $root = $this->resolvedRoot();
+
+        if ($root === null) {
+            return [];
+        }
+
+        $pattern = $root.DIRECTORY_SEPARATOR.$prefix.'*';
+        $matches = glob($pattern);
+
+        if ($matches === false) {
+            return [];
+        }
+
+        $keys = [];
+
+        foreach ($matches as $path) {
+            $keys[] = basename($path);
+        }
+
+        return $keys;
+    }
+
+    /**
+     * Absolute path for `$key`. Not part of the interface — used by the
+     * coverage merger and similar callers that need direct filesystem
+     * access (e.g. `require` on a cached PHP file). Consumers that only
+     * deal in bytes should go through `read()` / `write()`.
+     */
+    public function pathFor(string $key): string
+    {
+        return $this->rootDir.DIRECTORY_SEPARATOR.$key;
+    }
+
+    /**
+     * Returns the resolved root if it exists already, otherwise `null`.
+     * Used by read-side helpers so they don't eagerly create the directory
+     * just to find nothing inside.
+     */
+    private function resolvedRoot(): ?string
+    {
+        $resolved = @realpath($this->rootDir);
+
+        return $resolved === false ? null : $resolved;
+    }
+
+    /**
+     * Creates the root dir on demand. Returns false only when creation
+     * fails and the directory still isn't there afterwards.
+     */
+    private function ensureRoot(): bool
+    {
+        if (is_dir($this->rootDir)) {
+            return true;
+        }
+
+        if (@mkdir($this->rootDir, 0755, true)) {
+            return true;
+        }
+
+        return is_dir($this->rootDir);
+    }
+}

src/Plugins/Tia/Fingerprint.php

@@ -0,0 +1,95 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Pest\Plugins\Tia;
+
+/**
+ * Captures environmental inputs that, when changed, make the TIA graph stale.
+ *
+ * Any drift in PHP version, Composer lock, or Pest/PHPUnit config can change
+ * what a test actually exercises, so the graph must be rebuilt in those cases.
+ *
+ * @internal
+ */
+final readonly class Fingerprint
+{
+    // Bump this whenever the set of inputs or the hash algorithm changes, so
+    // older graphs are invalidated automatically.
+    private const int SCHEMA_VERSION = 2;
+
+    /**
+     * @return array<string, int|string|null>
+     */
+    public static function compute(string $projectRoot): array
+    {
+        return [
+            'schema' => self::SCHEMA_VERSION,
+            'php' => PHP_VERSION,
+            'pest' => self::readPestVersion($projectRoot),
+            'composer_lock' => self::hashIfExists($projectRoot.'/composer.lock'),
+            'phpunit_xml' => self::hashIfExists($projectRoot.'/phpunit.xml'),
+            'phpunit_xml_dist' => self::hashIfExists($projectRoot.'/phpunit.xml.dist'),
+            'pest_php' => self::hashIfExists($projectRoot.'/tests/Pest.php'),
+            // Pest's generated classes bake the code-generation logic in — if
+            // TestCaseFactory changes (new attribute, different method
+            // signature, etc.) every previously-recorded edge is stale.
+            // Hashing the factory sources makes path-repo / dev-main installs
+            // automatically rebuild their graphs when Pest itself is edited.
+            'pest_factory' => self::hashIfExists(__DIR__.'/../../Factories/TestCaseFactory.php'),
+            'pest_method_factory' => self::hashIfExists(__DIR__.'/../../Factories/TestCaseMethodFactory.php'),
+        ];
+    }
+
+    /**
+     * @param  array<string, mixed>  $a
+     * @param  array<string, mixed>  $b
+     */
+    public static function matches(array $a, array $b): bool
+    {
+        ksort($a);
+        ksort($b);
+
+        return $a === $b;
+    }
+
+    private static function hashIfExists(string $path): ?string
+    {
+        if (! is_file($path)) {
+            return null;
+        }
+
+        $hash = @hash_file('xxh128', $path);
+
+        return $hash === false ? null : $hash;
+    }
+
+    private static function readPestVersion(string $projectRoot): string
+    {
+        $installed = $projectRoot.'/vendor/composer/installed.json';
+
+        if (! is_file($installed)) {
+            return 'unknown';
+        }
+
+        $raw = @file_get_contents($installed);
+
+        if ($raw === false) {
+            return 'unknown';
+        }
+
+        $data = json_decode($raw, true);
+
+        if (! is_array($data) || ! isset($data['packages']) || ! is_array($data['packages'])) {
+            return 'unknown';
+        }
+
+        foreach ($data['packages'] as $package) {
+            if (is_array($package) && ($package['name'] ?? null) === 'pestphp/pest') {
+                return (string) ($package['version'] ?? 'unknown');
+            }
+        }
+
+        return 'unknown';
+    }
+}

src/Plugins/Tia/Graph.php

@@ -0,0 +1,502 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Pest\Plugins\Tia;
+
+use Pest\Support\Container;
+use PHPUnit\Framework\TestStatus\TestStatus;
+
+/**
+ * File-level Test Impact Analysis graph.
+ *
+ * Persists the mapping `test_file → set<source_file>` so that subsequent runs
+ * can skip tests whose dependencies have not changed. Paths are stored relative
+ * to the project root and source files are deduplicated via an index so that
+ * the on-disk JSON stays compact for large suites.
+ *
+ * @internal
+ */
+final class Graph
+{
+    /**
+     * Relative path of each known source file, indexed by numeric id.
+     *
+     * @var array<int, string>
+     */
+    private array $files = [];
+
+    /**
+     * Reverse lookup: source file → numeric id.
+     *
+     * @var array<string, int>
+     */
+    private array $fileIds = [];
+
+    /**
+     * Edges: test file (relative) → list of source file ids.
+     *
+     * @var array<string, array<int, int>>
+     */
+    private array $edges = [];
+
+    /**
+     * Environment fingerprint captured at record time.
+     *
+     * @var array<string, mixed>
+     */
+    private array $fingerprint = [];
+
+    /**
+     * Per-branch baselines. Each branch independently tracks:
+     *   - `sha`     — last HEAD at which `--tia` ran on this branch
+     *   - `tree`    — content hashes of modified files at that point
+     *   - `results` — per-test status + message + time
+     *
+     * Graph edges (test → source) stay shared across branches because
+     * structure doesn't change per branch. Only run-state is per-branch so
+     * a failing test on one branch doesn't poison another branch's replay.
+     *
+     * @var array<string, array{
+     *     sha: ?string,
+     *     tree: array<string, string>,
+     *     results: array<string, array{status: int, message: string, time: float, assertions?: int}>
+     * }>
+     */
+    private array $baselines = [];
+
+    /**
+     * Canonicalised project root. Resolved through `realpath()` so paths
+     * captured by coverage drivers (always real filesystem targets) match
+     * regardless of whether the user's CWD is a symlink or has trailing
+     * separators.
+     */
+    private readonly string $projectRoot;
+
+    public function __construct(string $projectRoot)
+    {
+        $real = @realpath($projectRoot);
+
+        $this->projectRoot = $real !== false ? $real : $projectRoot;
+    }
+
+    /**
+     * Records that a test file depends on the given source file.
+     */
+    public function link(string $testFile, string $sourceFile): void
+    {
+        $testRel = $this->relative($testFile);
+        $sourceRel = $this->relative($sourceFile);
+
+        if ($sourceRel === null || $testRel === null) {
+            return;
+        }
+
+        if (! isset($this->fileIds[$sourceRel])) {
+            $id = count($this->files);
+            $this->files[$id] = $sourceRel;
+            $this->fileIds[$sourceRel] = $id;
+        }
+
+        $this->edges[$testRel][] = $this->fileIds[$sourceRel];
+    }
+
+    /**
+     * Returns the set of test files whose dependencies intersect $changedFiles.
+     *
+     * Two resolution paths:
+     *   1. **Coverage edges** — test depends on a PHP source file that changed.
+     *   2. **Watch patterns** — a non-PHP file (JS, CSS, config, …) matches a
+     *      glob that maps to a test directory; every test under that directory
+     *      is affected.
+     *
+     * @param  array<int, string>  $changedFiles  Absolute or relative paths.
+     * @return array<int, string> Relative test file paths.
+     */
+    public function affected(array $changedFiles): array
+    {
+        // Normalise all changed paths once.
+        $normalised = [];
+
+        foreach ($changedFiles as $file) {
+            $rel = $this->relative($file);
+
+            if ($rel !== null) {
+                $normalised[] = $rel;
+            }
+        }
+
+        // 1. Coverage-edge lookup (PHP → PHP).
+        $changedIds = [];
+        $unknownSourceDirs = [];
+
+        foreach ($normalised as $rel) {
+            if (isset($this->fileIds[$rel])) {
+                $changedIds[$this->fileIds[$rel]] = true;
+            } elseif (str_ends_with($rel, '.php') && ! str_starts_with($rel, 'tests/')) {
+                // Source PHP file unknown to the graph — might be a new file
+                // that only exists on this branch (graph inherited from main).
+                // Track its directory for the sibling heuristic (step 3).
+                $unknownSourceDirs[dirname($rel)] = true;
+            }
+        }
+
+        $affectedSet = [];
+
+        foreach ($this->edges as $testFile => $ids) {
+            foreach ($ids as $id) {
+                if (isset($changedIds[$id])) {
+                    $affectedSet[$testFile] = true;
+
+                    break;
+                }
+            }
+        }
+
+        // 2. Watch-pattern lookup (non-PHP assets → test directories).
+        /** @var WatchPatterns $watchPatterns */
+        $watchPatterns = Container::getInstance()->get(WatchPatterns::class);
+
+        $dirs = $watchPatterns->matchedDirectories($this->projectRoot, $normalised);
+        $allTestFiles = array_keys($this->edges);
+
+        foreach ($watchPatterns->testsUnderDirectories($dirs, $allTestFiles) as $testFile) {
+            $affectedSet[$testFile] = true;
+        }
+
+        // 3. Sibling heuristic for unknown source files.
+        //
+        // When a PHP source file is unknown to the graph (no test depends on
+        // it), it is either genuinely untested OR it was added on a branch
+        // whose graph was inherited from another branch (e.g. main). In the
+        // latter case the graph simply never saw the file.
+        //
+        // To avoid silent misses: find tests that already cover ANY file in
+        // the same directory. If `app/Models/OrderItem.php` is unknown but
+        // `app/Models/Order.php` is covered by `OrderTest`, run `OrderTest`
+        // — it likely exercises sibling files in the same module.
+        //
+        // This over-runs slightly (sibling may be unrelated) but never
+        // under-runs. And once the test executes, its coverage captures the
+        // new file → graph self-heals for next run.
+        if ($unknownSourceDirs !== []) {
+            foreach ($this->edges as $testFile => $ids) {
+                if (isset($affectedSet[$testFile])) {
+                    continue;
+                }
+
+                foreach ($ids as $id) {
+                    if (! isset($this->files[$id])) {
+                        continue;
+                    }
+
+                    $depDir = dirname($this->files[$id]);
+
+                    if (isset($unknownSourceDirs[$depDir])) {
+                        $affectedSet[$testFile] = true;
+
+                        break;
+                    }
+                }
+            }
+        }
+
+        return array_keys($affectedSet);
+    }
+
+    /**
+     * Returns `true` if the given test file has any recorded dependencies.
+     */
+    public function knowsTest(string $testFile): bool
+    {
+        $rel = $this->relative($testFile);
+
+        return $rel !== null && isset($this->edges[$rel]);
+    }
+
+    /**
+     * @return array<int, string> All project-relative test files the graph knows.
+     */
+    public function allTestFiles(): array
+    {
+        return array_keys($this->edges);
+    }
+
+    /**
+     * @param  array<string, int|string|null>  $fingerprint
+     */
+    public function setFingerprint(array $fingerprint): void
+    {
+        $this->fingerprint = $fingerprint;
+    }
+
+    /**
+     * @return array<string, int|string|null>
+     */
+    public function fingerprint(): array
+    {
+        return $this->fingerprint;
+    }
+
+    /**
+     * Returns the SHA the given branch last ran against, or falls back to
+     * `$fallbackBranch` (typically `main`) when this branch has no baseline
+     * yet. That way a freshly-created feature branch inherits main's
+     * baseline on its first run.
+     */
+    public function recordedAtSha(string $branch, string $fallbackBranch = 'main'): ?string
+    {
+        $baseline = $this->baselineFor($branch, $fallbackBranch);
+
+        return $baseline['sha'];
+    }
+
+    public function setRecordedAtSha(string $branch, ?string $sha): void
+    {
+        $this->ensureBaseline($branch);
+        $this->baselines[$branch]['sha'] = $sha;
+    }
+
+    public function setResult(string $branch, string $testId, int $status, string $message, float $time, int $assertions = 0): void
+    {
+        $this->ensureBaseline($branch);
+        $this->baselines[$branch]['results'][$testId] = [
+            'status' => $status,
+            'message' => $message,
+            'time' => $time,
+            'assertions' => $assertions,
+        ];
+    }
+
+    /**
+     * Returns the cached assertion count for a test, or `null` if unknown.
+     * Callers use this to feed `addToAssertionCount()` at replay time so
+     * the "Tests: N passed (M assertions)" banner matches the recorded run
+     * instead of defaulting to 1 assertion per test.
+     */
+    public function getAssertions(string $branch, string $testId, string $fallbackBranch = 'main'): ?int
+    {
+        $baseline = $this->baselineFor($branch, $fallbackBranch);
+
+        if (! isset($baseline['results'][$testId]['assertions'])) {
+            return null;
+        }
+
+        $value = $baseline['results'][$testId]['assertions'];
+
+        return is_int($value) ? $value : null;
+    }
+
+    public function getResult(string $branch, string $testId, string $fallbackBranch = 'main'): ?TestStatus
+    {
+        $baseline = $this->baselineFor($branch, $fallbackBranch);
+
+        if (! isset($baseline['results'][$testId])) {
+            return null;
+        }
+
+        $r = $baseline['results'][$testId];
+
+        // PHPUnit's `TestStatus::from(int)` ignores messages, so reconstruct
+        // each variant via its specific factory. Keeps the stored message
+        // intact (important for skips/failures shown to the user).
+        return match ($r['status']) {
+            0 => TestStatus::success(),
+            1 => TestStatus::skipped($r['message']),
+            2 => TestStatus::incomplete($r['message']),
+            3 => TestStatus::notice($r['message']),
+            4 => TestStatus::deprecation($r['message']),
+            5 => TestStatus::risky($r['message']),
+            6 => TestStatus::warning($r['message']),
+            7 => TestStatus::failure($r['message']),
+            8 => TestStatus::error($r['message']),
+            default => TestStatus::unknown(),
+        };
+    }
+
+    /**
+     * @param  array<string, string>  $tree  project-relative path → content hash
+     */
+    public function setLastRunTree(string $branch, array $tree): void
+    {
+        $this->ensureBaseline($branch);
+        $this->baselines[$branch]['tree'] = $tree;
+    }
+
+    /**
+     * @return array<string, string>
+     */
+    public function lastRunTree(string $branch, string $fallbackBranch = 'main'): array
+    {
+        return $this->baselineFor($branch, $fallbackBranch)['tree'];
+    }
+
+    /**
+     * @return array{sha: ?string, tree: array<string, string>, results: array<string, array{status: int, message: string, time: float, assertions?: int}>}
+     */
+    private function baselineFor(string $branch, string $fallbackBranch): array
+    {
+        if (isset($this->baselines[$branch])) {
+            return $this->baselines[$branch];
+        }
+
+        if ($branch !== $fallbackBranch && isset($this->baselines[$fallbackBranch])) {
+            return $this->baselines[$fallbackBranch];
+        }
+
+        return ['sha' => null, 'tree' => [], 'results' => []];
+    }
+
+    private function ensureBaseline(string $branch): void
+    {
+        if (! isset($this->baselines[$branch])) {
+            $this->baselines[$branch] = ['sha' => null, 'tree' => [], 'results' => []];
+        }
+    }
+
+    /**
+     * Replaces edges for the given test files. Used during a partial record
+     * run so that existing edges for other tests are preserved.
+     *
+     * @param  array<string, array<int, string>>  $testToFiles
+     */
+    public function replaceEdges(array $testToFiles): void
+    {
+        foreach ($testToFiles as $testFile => $sources) {
+            $testRel = $this->relative($testFile);
+
+            if ($testRel === null) {
+                continue;
+            }
+
+            $this->edges[$testRel] = [];
+
+            foreach ($sources as $source) {
+                $this->link($testFile, $source);
+            }
+
+            // Deduplicate ids for this test.
+            $this->edges[$testRel] = array_values(array_unique($this->edges[$testRel]));
+        }
+    }
+
+    /**
+     * Drops edges whose test file no longer exists on disk. Prevents the graph
+     * from keeping stale entries for deleted / renamed tests that would later
+     * be flagged as affected and confuse PHPUnit's discovery.
+     */
+    public function pruneMissingTests(): void
+    {
+        $root = rtrim($this->projectRoot, DIRECTORY_SEPARATOR).DIRECTORY_SEPARATOR;
+
+        foreach (array_keys($this->edges) as $testRel) {
+            if (! is_file($root.$testRel)) {
+                unset($this->edges[$testRel]);
+            }
+        }
+    }
+
+    /**
+     * Rebuilds a graph from its JSON representation. Returns `null` when
+     * the payload is missing, unreadable, or schema-incompatible. Separated
+     * from transport (state backend, file, etc.) so tests can feed bytes
+     * directly without touching disk.
+     */
+    public static function decode(string $json, string $projectRoot): ?self
+    {
+        $data = json_decode($json, true);
+
+        if (! is_array($data) || ($data['schema'] ?? null) !== 1) {
+            return null;
+        }
+
+        $graph = new self($projectRoot);
+        $graph->fingerprint = is_array($data['fingerprint'] ?? null) ? $data['fingerprint'] : [];
+        $graph->files = is_array($data['files'] ?? null) ? array_values($data['files']) : [];
+        $graph->fileIds = array_flip($graph->files);
+        $graph->edges = is_array($data['edges'] ?? null) ? $data['edges'] : [];
+        $graph->baselines = is_array($data['baselines'] ?? null) ? $data['baselines'] : [];
+
+        return $graph;
+    }
+
+    /**
+     * Serialises the graph to its JSON on-disk form. Returns `null` if the
+     * payload can't be encoded (extremely rare — pathological UTF-8 only).
+     * Persistence is the caller's responsibility: write the returned bytes
+     * through whatever `State` implementation is in play.
+     */
+    public function encode(): ?string
+    {
+        $payload = [
+            'schema' => 1,
+            'fingerprint' => $this->fingerprint,
+            'files' => $this->files,
+            'edges' => $this->edges,
+            'baselines' => $this->baselines,
+        ];
+
+        $json = json_encode($payload, JSON_UNESCAPED_SLASHES);
+
+        return $json === false ? null : $json;
+    }
+
+    /**
+     * Normalises a path to be relative to the project root; returns `null` for
+     * paths we should ignore (outside the project, unknown, virtual, vendor).
+     *
+     * Accepts both absolute paths (from Xdebug/PCOV coverage) and
+     * project-relative paths (from `git diff`) — we normalise without relying
+     * on `realpath()` of relative paths because the current working directory
+     * is not guaranteed to be the project root.
+     */
+    private function relative(string $path): ?string
+    {
+        if ($path === '' || $path === 'unknown') {
+            return null;
+        }
+
+        if (str_contains($path, "eval()'d")) {
+            return null;
+        }
+
+        $root = rtrim($this->projectRoot, DIRECTORY_SEPARATOR).DIRECTORY_SEPARATOR;
+
+        $isAbsolute = str_starts_with($path, DIRECTORY_SEPARATOR)
+            || (strlen($path) >= 2 && $path[1] === ':'); // Windows drive
+
+        if ($isAbsolute) {
+            $real = @realpath($path);
+
+            if ($real === false) {
+                $real = $path;
+            }
+
+            if (! str_starts_with($real, $root)) {
+                return null;
+            }
+
+            // Always normalise to forward slashes. Windows' native separator
+            // would otherwise produce keys that never match paths reported
+            // by `git` (which always uses forward slashes).
+            $relative = str_replace(DIRECTORY_SEPARATOR, '/', substr($real, strlen($root)));
+        } else {
+            // Normalise directory separators and strip any "./" prefix.
+            $relative = str_replace(DIRECTORY_SEPARATOR, '/', $path);
+
+            while (str_starts_with($relative, './')) {
+                $relative = substr($relative, 2);
+            }
+        }
+
+        // Vendor packages are pinned by composer.lock. Any upgrade bumps the
+        // fingerprint and invalidates the graph wholesale, so there is no
+        // reason to track individual vendor files — doing so inflates the
+        // graph by orders of magnitude on Laravel-style projects.
+        if (str_starts_with($relative, 'vendor/')) {
+            return null;
+        }
+
+        return $relative;
+    }
+}

src/Plugins/Tia/Recorder.php

@@ -0,0 +1,229 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Pest\Plugins\Tia;
+
+use ReflectionClass;
+
+/**
+ * Captures per-test file coverage using the PCOV driver.
+ *
+ * Acts as a singleton because PCOV has a single global collection state and
+ * the recorder is wired into PHPUnit through two distinct subscribers
+ * (`Prepared` / `Finished`) that must share context.
+ *
+ * @internal
+ */
+final class Recorder
+{
+    /**
+     * Test file currently being recorded, or `null` when idle.
+     */
+    private ?string $currentTestFile = null;
+
+    /**
+     * Aggregated map: absolute test file → set<absolute source file>.
+     *
+     * @var array<string, array<string, true>>
+     */
+    private array $perTestFiles = [];
+
+    /**
+     * Cached class → test file resolution.
+     *
+     * @var array<string, string|null>
+     */
+    private array $classFileCache = [];
+
+    private bool $active = false;
+
+    private bool $driverChecked = false;
+
+    private bool $driverAvailable = false;
+
+    private string $driver = 'none';
+
+    public function activate(): void
+    {
+        $this->active = true;
+    }
+
+    public function isActive(): bool
+    {
+        return $this->active;
+    }
+
+    public function driverAvailable(): bool
+    {
+        if (! $this->driverChecked) {
+            if (function_exists('pcov\\start')) {
+                $this->driver = 'pcov';
+                $this->driverAvailable = true;
+            } elseif (function_exists('xdebug_start_code_coverage')) {
+                // Xdebug is loaded. Probe whether coverage mode is active by
+                // attempting a start — it emits E_WARNING when the mode is off.
+                // We capture the warning via a temporary error handler.
+                $probeOk = true;
+                set_error_handler(static function () use (&$probeOk): bool {
+                    $probeOk = false;
+
+                    return true;
+                });
+                \xdebug_start_code_coverage();
+                restore_error_handler();
+
+                if ($probeOk) {
+                    \xdebug_stop_code_coverage(false);
+                    $this->driver = 'xdebug';
+                    $this->driverAvailable = true;
+                }
+            }
+
+            $this->driverChecked = true;
+        }
+
+        return $this->driverAvailable;
+    }
+
+    public function driver(): string
+    {
+        $this->driverAvailable();
+
+        return $this->driver;
+    }
+
+    public function beginTest(string $className, string $methodName, string $fallbackFile): void
+    {
+        if (! $this->active || ! $this->driverAvailable()) {
+            return;
+        }
+
+        $file = $this->resolveTestFile($className, $fallbackFile);
+
+        if ($file === null) {
+            return;
+        }
+
+        $this->currentTestFile = $file;
+
+        if ($this->driver === 'pcov') {
+            \pcov\clear();
+            \pcov\start();
+
+            return;
+        }
+
+        // Xdebug
+        \xdebug_start_code_coverage();
+    }
+
+    public function endTest(): void
+    {
+        if (! $this->active || ! $this->driverAvailable() || $this->currentTestFile === null) {
+            return;
+        }
+
+        if ($this->driver === 'pcov') {
+            \pcov\stop();
+            /** @var array<string, mixed> $data */
+            $data = \pcov\collect(\pcov\inclusive);
+        } else {
+            /** @var array<string, mixed> $data */
+            $data = \xdebug_get_code_coverage();
+            // `true` resets Xdebug's internal buffer so the next `start()`
+            // does not accumulate earlier tests' coverage into the current
+            // one — otherwise the graph becomes progressively polluted.
+            \xdebug_stop_code_coverage(true);
+        }
+
+        foreach (array_keys($data) as $sourceFile) {
+            $this->perTestFiles[$this->currentTestFile][$sourceFile] = true;
+        }
+
+        $this->currentTestFile = null;
+    }
+
+    /**
+     * @return array<string, array<int, string>> absolute test file → list of absolute source files.
+     */
+    public function perTestFiles(): array
+    {
+        $out = [];
+
+        foreach ($this->perTestFiles as $testFile => $sources) {
+            $out[$testFile] = array_keys($sources);
+        }
+
+        return $out;
+    }
+
+    private function resolveTestFile(string $className, string $fallbackFile): ?string
+    {
+        if (array_key_exists($className, $this->classFileCache)) {
+            $file = $this->classFileCache[$className];
+        } else {
+            $file = $this->readPestFilename($className);
+            $this->classFileCache[$className] = $file;
+        }
+
+        if ($file !== null) {
+            return $file;
+        }
+
+        if ($fallbackFile !== '' && $fallbackFile !== 'unknown' && ! str_contains($fallbackFile, "eval()'d")) {
+            return $fallbackFile;
+        }
+
+        return null;
+    }
+
+    /**
+     * Resolves the file that *defines* the test class.
+     *
+     * Order of preference:
+     *   1. Pest's generated `$__filename` static — the original `*.php` file
+     *      containing the `test()` calls (the eval'd class itself has no file).
+     *   2. `ReflectionClass::getFileName()` — the concrete class's file. This
+     *      is intentionally more specific than `ReflectionMethod::getFileName()`
+     *      (which would return the *trait* file for methods brought in via
+     *      `uses SharedTestBehavior`).
+     */
+    private function readPestFilename(string $className): ?string
+    {
+        if (! class_exists($className, false)) {
+            return null;
+        }
+
+        $reflection = new ReflectionClass($className);
+
+        if ($reflection->hasProperty('__filename')) {
+            $property = $reflection->getProperty('__filename');
+
+            if ($property->isStatic()) {
+                $value = $property->getValue();
+
+                if (is_string($value)) {
+                    return $value;
+                }
+            }
+        }
+
+        $file = $reflection->getFileName();
+
+        return is_string($file) ? $file : null;
+    }
+
+    /**
+     * Clears all captured state. Useful for long-running hosts (daemons,
+     * PHP-FPM, watchers) that invoke Pest multiple times in a single process
+     * — without this, coverage from run N would bleed into run N+1.
+     */
+    public function reset(): void
+    {
+        $this->currentTestFile = null;
+        $this->perTestFiles = [];
+        $this->classFileCache = [];
+        $this->active = false;
+    }
+}

src/Plugins/Tia/ResultCollector.php

@@ -0,0 +1,155 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Pest\Plugins\Tia;
+
+/**
+ * Collects per-test status + message during the run so the graph can persist
+ * them for faithful replay. PHPUnit's own result cache discards messages
+ * during serialisation — this collector retains them.
+ *
+ * @internal
+ */
+final class ResultCollector
+{
+    /**
+     * @var array<string, array{status: int, message: string, time: float, assertions: int}>
+     */
+    private array $results = [];
+
+    private ?string $currentTestId = null;
+
+    private ?float $startTime = null;
+
+    public function testPrepared(string $testId): void
+    {
+        $this->currentTestId = $testId;
+        $this->startTime = microtime(true);
+    }
+
+    public function testPassed(): void
+    {
+        if ($this->currentTestId === null) {
+            return;
+        }
+
+        $this->record(0, '');
+    }
+
+    public function testFailed(string $message): void
+    {
+        if ($this->currentTestId === null) {
+            return;
+        }
+
+        $this->record(7, $message);
+    }
+
+    public function testErrored(string $message): void
+    {
+        if ($this->currentTestId === null) {
+            return;
+        }
+
+        $this->record(8, $message);
+    }
+
+    public function testSkipped(string $message): void
+    {
+        if ($this->currentTestId === null) {
+            return;
+        }
+
+        $this->record(1, $message);
+    }
+
+    public function testIncomplete(string $message): void
+    {
+        if ($this->currentTestId === null) {
+            return;
+        }
+
+        $this->record(2, $message);
+    }
+
+    public function testRisky(string $message): void
+    {
+        if ($this->currentTestId === null) {
+            return;
+        }
+
+        $this->record(5, $message);
+    }
+
+    /**
+     * @return array<string, array{status: int, message: string, time: float, assertions: int}>
+     */
+    public function all(): array
+    {
+        return $this->results;
+    }
+
+    public function recordAssertions(string $testId, int $assertions): void
+    {
+        if (isset($this->results[$testId])) {
+            $this->results[$testId]['assertions'] = $assertions;
+        }
+    }
+
+    /**
+     * Injects externally-collected results (e.g. partials flushed by parallel
+     * workers) into this collector so the parent can persist them in the same
+     * snapshot pass as non-parallel runs.
+     *
+     * @param  array<string, array{status: int, message: string, time: float, assertions: int}>  $results
+     */
+    public function merge(array $results): void
+    {
+        foreach ($results as $testId => $result) {
+            $this->results[$testId] = $result;
+        }
+    }
+
+    public function reset(): void
+    {
+        $this->results = [];
+        $this->currentTestId = null;
+        $this->startTime = null;
+    }
+
+    /**
+     * Called by the Finished subscriber after a test's outcome + assertion
+     * events have all fired. Clears the "currently recording" pointer so
+     * the next test's events don't get mis-attributed.
+     */
+    public function finishTest(): void
+    {
+        $this->currentTestId = null;
+        $this->startTime = null;
+    }
+
+    private function record(int $status, string $message): void
+    {
+        if ($this->currentTestId === null) {
+            return;
+        }
+
+        $time = $this->startTime !== null
+            ? round(microtime(true) - $this->startTime, 3)
+            : 0.0;
+
+        // PHPUnit can fire more than one outcome event per test — the
+        // canonical case is a risky pass (`Passed` then `ConsideredRisky`).
+        // Last-wins semantics preserve the most specific status; the
+        // existing assertion count (if any) survives the overwrite.
+        $existing = $this->results[$this->currentTestId] ?? null;
+
+        $this->results[$this->currentTestId] = [
+            'status' => $status,
+            'message' => $message,
+            'time' => $time,
+            'assertions' => $existing['assertions'] ?? 0,
+        ];
+    }
+}

src/Plugins/Tia/WatchDefaults/Browser.php

@@ -0,0 +1,119 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Pest\Plugins\Tia\WatchDefaults;
+
+use Composer\InstalledVersions;
+use Pest\Browser\Support\BrowserTestIdentifier;
+use Pest\Factories\TestCaseFactory;
+use Pest\TestSuite;
+
+/**
+ * Watch patterns for frontend assets that affect browser tests.
+ *
+ * Uses `BrowserTestIdentifier` from pest-plugin-browser (if installed) to
+ * auto-discover directories containing browser tests. Falls back to the
+ * `tests/Browser` convention when the plugin is absent.
+ *
+ * @internal
+ */
+final readonly class Browser implements WatchDefault
+{
+    public function applicable(): bool
+    {
+        // Browser tests can exist in any PHP project. We only activate when
+        // there is an actual `tests/Browser` directory OR pest-plugin-browser
+        // is installed.
+        return class_exists(InstalledVersions::class)
+            && InstalledVersions::isInstalled('pestphp/pest-plugin-browser');
+    }
+
+    public function defaults(string $projectRoot, string $testPath): array
+    {
+        $browserDirs = $this->detectBrowserTestDirs($projectRoot, $testPath);
+
+        $globs = [
+            'resources/js/**/*.js',
+            'resources/js/**/*.ts',
+            'resources/js/**/*.tsx',
+            'resources/js/**/*.jsx',
+            'resources/js/**/*.vue',
+            'resources/js/**/*.svelte',
+            'resources/css/**/*.css',
+            'resources/css/**/*.scss',
+            'resources/css/**/*.less',
+            // Vite / Webpack build output that browser tests may consume.
+            'public/build/**/*.js',
+            'public/build/**/*.css',
+        ];
+
+        $patterns = [];
+
+        foreach ($globs as $glob) {
+            $patterns[$glob] = $browserDirs;
+        }
+
+        return $patterns;
+    }
+
+    /**
+     * @return array<int, string>
+     */
+    private function detectBrowserTestDirs(string $projectRoot, string $testPath): array
+    {
+        $dirs = [];
+
+        $candidate = $testPath.'/Browser';
+
+        if (is_dir($projectRoot.DIRECTORY_SEPARATOR.$candidate)) {
+            $dirs[] = $candidate;
+        }
+
+        // Scan TestRepository via BrowserTestIdentifier if pest-plugin-browser
+        // is installed to find tests using `visit()` outside the conventional
+        // Browser/ folder.
+        if (class_exists(BrowserTestIdentifier::class)) {
+            $repo = TestSuite::getInstance()->tests;
+
+            foreach ($repo->getFilenames() as $filename) {
+                $factory = $repo->get($filename);
+
+                if (! $factory instanceof TestCaseFactory) {
+                    continue;
+                }
+
+                foreach ($factory->methods as $method) {
+                    if (BrowserTestIdentifier::isBrowserTest($method)) {
+                        $rel = $this->fileRelative($projectRoot, $filename);
+
+                        if ($rel !== null) {
+                            $dirs[] = dirname($rel);
+                        }
+
+                        break;
+                    }
+                }
+            }
+        }
+
+        return array_values(array_unique($dirs === [] ? [$testPath] : $dirs));
+    }
+
+    private function fileRelative(string $projectRoot, string $path): ?string
+    {
+        $real = @realpath($path);
+
+        if ($real === false) {
+            $real = $path;
+        }
+
+        $root = rtrim($projectRoot, DIRECTORY_SEPARATOR).DIRECTORY_SEPARATOR;
+
+        if (! str_starts_with($real, $root)) {
+            return null;
+        }
+
+        return str_replace(DIRECTORY_SEPARATOR, '/', substr($real, strlen($root)));
+    }
+}

src/Plugins/Tia/WatchDefaults/Inertia.php

@@ -0,0 +1,53 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Pest\Plugins\Tia\WatchDefaults;
+
+use Composer\InstalledVersions;
+
+/**
+ * Watch patterns for Inertia.js projects (Laravel or otherwise).
+ *
+ * Inertia bridges PHP controllers with JS/TS page components. A change to
+ * a React / Vue / Svelte page can break assertions in browser tests or
+ * Inertia-specific feature tests.
+ *
+ * @internal
+ */
+final readonly class Inertia implements WatchDefault
+{
+    public function applicable(): bool
+    {
+        return class_exists(InstalledVersions::class)
+            && (InstalledVersions::isInstalled('inertiajs/inertia-laravel')
+                || InstalledVersions::isInstalled('rompetomp/inertia-bundle'));
+    }
+
+    public function defaults(string $projectRoot, string $testPath): array
+    {
+        $browserDir = is_dir($projectRoot.DIRECTORY_SEPARATOR.$testPath.'/Browser')
+            ? $testPath.'/Browser'
+            : $testPath;
+
+        return [
+            // Inertia page components (React / Vue / Svelte).
+            'resources/js/Pages/**/*.vue' => [$testPath, $browserDir],
+            'resources/js/Pages/**/*.tsx' => [$testPath, $browserDir],
+            'resources/js/Pages/**/*.jsx' => [$testPath, $browserDir],
+            'resources/js/Pages/**/*.svelte' => [$testPath, $browserDir],
+
+            // Shared layouts / components consumed by pages.
+            'resources/js/Layouts/**/*.vue' => [$browserDir],
+            'resources/js/Layouts/**/*.tsx' => [$browserDir],
+            'resources/js/Components/**/*.vue' => [$browserDir],
+            'resources/js/Components/**/*.tsx' => [$browserDir],
+
+            // SSR entry point.
+            'resources/js/ssr.js' => [$browserDir],
+            'resources/js/ssr.ts' => [$browserDir],
+            'resources/js/app.js' => [$browserDir],
+            'resources/js/app.ts' => [$browserDir],
+        ];
+    }
+}

src/Plugins/Tia/WatchDefaults/Laravel.php

@@ -0,0 +1,81 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Pest\Plugins\Tia\WatchDefaults;
+
+use Composer\InstalledVersions;
+
+/**
+ * Watch patterns for Laravel projects.
+ *
+ * Laravel boots the entire application inside `setUp()` (before PHPUnit's
+ * `Prepared` event where TIA's coverage window opens). That means PHP files
+ * loaded during boot — config, routes, service providers, migrations — are
+ * invisible to the coverage driver. Watch patterns are the only way to
+ * track them.
+ *
+ * @internal
+ */
+final readonly class Laravel implements WatchDefault
+{
+    public function applicable(): bool
+    {
+        return class_exists(InstalledVersions::class)
+            && InstalledVersions::isInstalled('laravel/framework');
+    }
+
+    public function defaults(string $projectRoot, string $testPath): array
+    {
+        $featurePath = is_dir($projectRoot.DIRECTORY_SEPARATOR.$testPath.'/Feature')
+            ? $testPath.'/Feature'
+            : $testPath;
+
+        return [
+            // Config — loaded during app boot (setUp), invisible to coverage.
+            // Affects both Feature and Unit: Pest.php commonly binds fakes
+            // and seeds DB based on config values.
+            'config/*.php' => [$testPath],
+            'config/**/*.php' => [$testPath],
+
+            // Routes — loaded during boot. HTTP/Feature tests depend on them.
+            'routes/*.php' => [$featurePath],
+            'routes/**/*.php' => [$featurePath],
+
+            // Service providers / bootstrap — loaded during boot, affect
+            // bindings, middleware, event listeners, scheduled tasks.
+            'bootstrap/app.php' => [$testPath],
+            'bootstrap/providers.php' => [$testPath],
+
+            // Migrations — run via RefreshDatabase/FastRefreshDatabase in
+            // setUp. Schema changes can break any test that touches DB.
+            'database/migrations/**/*.php' => [$testPath],
+
+            // Seeders — often run globally via Pest.php beforeEach.
+            'database/seeders/**/*.php' => [$testPath],
+
+            // Factories — loaded lazily but still PHP that coverage may miss
+            // if the factory file was already autoloaded before Prepared.
+            'database/factories/**/*.php' => [$testPath],
+
+            // Blade templates — compiled to cache, source file not executed.
+            'resources/views/**/*.blade.php' => [$featurePath],
+
+            // Translations — JSON translations read via file_get_contents,
+            // PHP translations loaded via include (but during boot).
+            'lang/**/*.php' => [$featurePath],
+            'lang/**/*.json' => [$featurePath],
+            'resources/lang/**/*.php' => [$featurePath],
+            'resources/lang/**/*.json' => [$featurePath],
+
+            // Build tool config — affects compiled assets consumed by
+            // browser and Inertia tests.
+            'vite.config.js' => [$featurePath],
+            'vite.config.ts' => [$featurePath],
+            'webpack.mix.js' => [$featurePath],
+            'tailwind.config.js' => [$featurePath],
+            'tailwind.config.ts' => [$featurePath],
+            'postcss.config.js' => [$featurePath],
+        ];
+    }
+}

src/Plugins/Tia/WatchDefaults/Livewire.php

@@ -0,0 +1,38 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Pest\Plugins\Tia\WatchDefaults;
+
+use Composer\InstalledVersions;
+
+/**
+ * Watch patterns for projects using Livewire.
+ *
+ * Livewire components pair a PHP class with a Blade view. A view change can
+ * break rendering or assertions in feature / browser tests even though the
+ * PHP side is untouched.
+ *
+ * @internal
+ */
+final readonly class Livewire implements WatchDefault
+{
+    public function applicable(): bool
+    {
+        return class_exists(InstalledVersions::class)
+            && InstalledVersions::isInstalled('livewire/livewire');
+    }
+
+    public function defaults(string $projectRoot, string $testPath): array
+    {
+        return [
+            // Livewire views live alongside Blade views or in a dedicated dir.
+            'resources/views/livewire/**/*.blade.php' => [$testPath],
+            'resources/views/components/**/*.blade.php' => [$testPath],
+
+            // Livewire JS interop / Alpine plugins.
+            'resources/js/**/*.js' => [$testPath],
+            'resources/js/**/*.ts' => [$testPath],
+        ];
+    }
+}

src/Plugins/Tia/WatchDefaults/Php.php

@@ -0,0 +1,53 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Pest\Plugins\Tia\WatchDefaults;
+
+/**
+ * Baseline watch patterns for any PHP project.
+ *
+ * @internal
+ */
+final readonly class Php implements WatchDefault
+{
+    public function applicable(): bool
+    {
+        return true;
+    }
+
+    public function defaults(string $projectRoot, string $testPath): array
+    {
+        // NOTE: composer.json / composer.lock changes are caught by the
+        // fingerprint (which hashes composer.lock). PHP files are tracked by
+        // the coverage driver. Only non-PHP, non-fingerprinted files that
+        // can silently alter test behaviour belong here.
+
+        return [
+            // Environment files — can change DB drivers, feature flags,
+            // queue connections, etc. Not PHP, not fingerprinted.
+            '.env' => [$testPath],
+            '.env.testing' => [$testPath],
+
+            // Docker / CI — can affect integration test infrastructure.
+            'docker-compose.yml' => [$testPath],
+            'docker-compose.yaml' => [$testPath],
+
+            // PHPUnit / Pest config (XML) — phpunit.xml IS fingerprinted, but
+            // phpunit.xml.dist and other XML overrides are not individually
+            // tracked by the coverage driver.
+            'phpunit.xml.dist' => [$testPath],
+
+            // Test fixtures — JSON, CSV, XML, TXT data files consumed by
+            // assertions. A fixture change can flip a test result.
+            $testPath.'/Fixtures/**/*.json' => [$testPath],
+            $testPath.'/Fixtures/**/*.csv' => [$testPath],
+            $testPath.'/Fixtures/**/*.xml' => [$testPath],
+            $testPath.'/Fixtures/**/*.txt' => [$testPath],
+
+            // Pest snapshots — external edits to snapshot files invalidate
+            // snapshot assertions.
+            $testPath.'/.pest/snapshots/**/*.snap' => [$testPath],
+        ];
+    }
+}

src/Plugins/Tia/WatchDefaults/Symfony.php

@@ -0,0 +1,75 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Pest\Plugins\Tia\WatchDefaults;
+
+use Composer\InstalledVersions;
+
+/**
+ * Watch patterns for Symfony projects.
+ *
+ * @internal
+ */
+final readonly class Symfony implements WatchDefault
+{
+    public function applicable(): bool
+    {
+        return class_exists(InstalledVersions::class)
+            && InstalledVersions::isInstalled('symfony/framework-bundle');
+    }
+
+    public function defaults(string $projectRoot, string $testPath): array
+    {
+        // Symfony boots the kernel in setUp() (before the coverage window).
+        // PHP config, routes, kernel, and migrations are loaded during boot
+        // and invisible to the coverage driver. Same reasoning as Laravel.
+
+        return [
+            // Config — YAML, XML, and PHP. All loaded during kernel boot.
+            'config/*.yaml' => [$testPath],
+            'config/*.yml' => [$testPath],
+            'config/*.php' => [$testPath],
+            'config/*.xml' => [$testPath],
+            'config/**/*.yaml' => [$testPath],
+            'config/**/*.yml' => [$testPath],
+            'config/**/*.php' => [$testPath],
+            'config/**/*.xml' => [$testPath],
+
+            // Routes — loaded during boot.
+            'config/routes/*.yaml' => [$testPath],
+            'config/routes/*.php' => [$testPath],
+            'config/routes/*.xml' => [$testPath],
+            'config/routes/**/*.yaml' => [$testPath],
+
+            // Kernel / bootstrap — loaded during boot.
+            'src/Kernel.php' => [$testPath],
+
+            // Migrations — run during setUp (before coverage window).
+            'migrations/**/*.php' => [$testPath],
+
+            // Twig templates — compiled, source not PHP-executed.
+            'templates/**/*.html.twig' => [$testPath],
+            'templates/**/*.twig' => [$testPath],
+
+            // Translations (YAML / XLF / XLIFF).
+            'translations/**/*.yaml' => [$testPath],
+            'translations/**/*.yml' => [$testPath],
+            'translations/**/*.xlf' => [$testPath],
+            'translations/**/*.xliff' => [$testPath],
+
+            // Doctrine XML/YAML mappings.
+            'config/doctrine/**/*.xml' => [$testPath],
+            'config/doctrine/**/*.yaml' => [$testPath],
+
+            // Webpack Encore / asset-mapper config + frontend sources.
+            'webpack.config.js' => [$testPath],
+            'importmap.php' => [$testPath],
+            'assets/**/*.js' => [$testPath],
+            'assets/**/*.ts' => [$testPath],
+            'assets/**/*.vue' => [$testPath],
+            'assets/**/*.css' => [$testPath],
+            'assets/**/*.scss' => [$testPath],
+        ];
+    }
+}

src/Plugins/Tia/WatchDefaults/WatchDefault.php

@@ -0,0 +1,28 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Pest\Plugins\Tia\WatchDefaults;
+
+/**
+ * A set of file-watch patterns that apply when a particular framework,
+ * library or project layout is detected.
+ *
+ * Each implementation probes for the presence of the tool it covers
+ * (`applicable`) and returns glob → test-directory mappings (`defaults`)
+ * that are merged into `WatchPatterns`.
+ *
+ * @internal
+ */
+interface WatchDefault
+{
+    /**
+     * Whether this default set applies to the current project.
+     */
+    public function applicable(): bool;
+
+    /**
+     * @return array<string, array<int, string>> glob → list of project-relative test dirs
+     */
+    public function defaults(string $projectRoot, string $testPath): array;
+}

src/Plugins/Tia/WatchPatterns.php

@@ -0,0 +1,188 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Pest\Plugins\Tia;
+
+use Pest\Plugins\Tia\WatchDefaults\WatchDefault;
+use Pest\TestSuite;
+
+/**
+ * Maps non-PHP file globs to the test directories they should invalidate.
+ *
+ * Coverage drivers only see `.php` files. Frontend assets, config files,
+ * Blade templates, routes and environment files are invisible to the graph.
+ * Watch patterns bridge the gap: when a changed file matches a glob, every
+ * test under the associated directory is marked as affected.
+ *
+ * Defaults are assembled dynamically from the `WatchDefaults/` registry —
+ * each implementation probes the current project and contributes patterns
+ * when applicable. Users extend via `pest()->tia()->watch(…)`.
+ *
+ * @internal
+ */
+final class WatchPatterns
+{
+    /**
+     * All known default providers, in evaluation order.
+     *
+     * @var array<int, class-string<WatchDefault>>
+     */
+    private const array DEFAULTS = [
+        WatchDefaults\Php::class,
+        WatchDefaults\Laravel::class,
+        WatchDefaults\Symfony::class,
+        WatchDefaults\Livewire::class,
+        WatchDefaults\Inertia::class,
+        WatchDefaults\Browser::class,
+    ];
+
+    /**
+     * @var array<string, array<int, string>> glob → list of project-relative test dirs
+     */
+    private array $patterns = [];
+
+    /**
+     * Probes every registered `WatchDefault` and merges the patterns of
+     * those that apply. Called once during Tia plugin boot, after BootFiles
+     * has loaded `tests/Pest.php` (so user-added `pest()->tia()->watch()`
+     * calls are already in `$this->patterns`).
+     */
+    public function useDefaults(string $projectRoot): void
+    {
+        $testPath = TestSuite::getInstance()->testPath;
+
+        foreach (self::DEFAULTS as $class) {
+            $default = new $class;
+
+            if (! $default->applicable()) {
+                continue;
+            }
+
+            foreach ($default->defaults($projectRoot, $testPath) as $glob => $dirs) {
+                $this->patterns[$glob] = array_values(array_unique(
+                    array_merge($this->patterns[$glob] ?? [], $dirs),
+                ));
+            }
+        }
+    }
+
+    /**
+     * Adds user-defined patterns. Merges with existing entries so a single
+     * glob can map to multiple directories.
+     *
+     * @param  array<string, string>  $patterns  glob → project-relative test dir
+     */
+    public function add(array $patterns): void
+    {
+        foreach ($patterns as $glob => $dir) {
+            $this->patterns[$glob] = array_values(array_unique(
+                array_merge($this->patterns[$glob] ?? [], [$dir]),
+            ));
+        }
+    }
+
+    /**
+     * Returns all test directories whose watch patterns match at least one of
+     * the given changed files.
+     *
+     * @param  string  $projectRoot  Absolute path.
+     * @param  array<int, string>  $changedFiles  Project-relative paths.
+     * @return array<int, string> Project-relative test directories.
+     */
+    public function matchedDirectories(string $projectRoot, array $changedFiles): array
+    {
+        if ($this->patterns === []) {
+            return [];
+        }
+
+        $matched = [];
+
+        foreach ($changedFiles as $file) {
+            foreach ($this->patterns as $glob => $dirs) {
+                if ($this->globMatches($glob, $file)) {
+                    foreach ($dirs as $dir) {
+                        $matched[$dir] = true;
+                    }
+                }
+            }
+        }
+
+        return array_keys($matched);
+    }
+
+    /**
+     * Given the affected directories, returns every test file in the graph
+     * that lives under one of those directories.
+     *
+     * @param  array<int, string>  $directories  Project-relative dirs.
+     * @param  array<int, string>  $allTestFiles  Project-relative test files from graph.
+     * @return array<int, string>
+     */
+    public function testsUnderDirectories(array $directories, array $allTestFiles): array
+    {
+        if ($directories === []) {
+            return [];
+        }
+
+        $affected = [];
+
+        foreach ($allTestFiles as $testFile) {
+            foreach ($directories as $dir) {
+                $prefix = rtrim($dir, '/').'/';
+
+                if (str_starts_with($testFile, $prefix)) {
+                    $affected[] = $testFile;
+
+                    break;
+                }
+            }
+        }
+
+        return $affected;
+    }
+
+    public function reset(): void
+    {
+        $this->patterns = [];
+    }
+
+    /**
+     * Matches a project-relative file against a glob pattern.
+     *
+     * Supports `*` (single segment), `**` (any depth) and `?`.
+     */
+    private function globMatches(string $pattern, string $file): bool
+    {
+        $pattern = str_replace('\\', '/', $pattern);
+        $file = str_replace('\\', '/', $file);
+
+        $regex = '';
+        $len = strlen($pattern);
+        $i = 0;
+
+        while ($i < $len) {
+            $c = $pattern[$i];
+
+            if ($c === '*' && isset($pattern[$i + 1]) && $pattern[$i + 1] === '*') {
+                $regex .= '.*';
+                $i += 2;
+
+                if (isset($pattern[$i]) && $pattern[$i] === '/') {
+                    $i++;
+                }
+            } elseif ($c === '*') {
+                $regex .= '[^/]*';
+                $i++;
+            } elseif ($c === '?') {
+                $regex .= '[^/]';
+                $i++;
+            } else {
+                $regex .= preg_quote($c, '#');
+                $i++;
+            }
+        }
+
+        return (bool) preg_match('#^'.$regex.'$#', $file);
+    }
+}

src/Subscribers/EnsureTiaAssertionsAreRecordedOnFinished.php

@@ -0,0 +1,40 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Pest\Subscribers;
+
+use Pest\Plugins\Tia\ResultCollector;
+use PHPUnit\Event\Code\TestMethod;
+use PHPUnit\Event\Test\Finished;
+use PHPUnit\Event\Test\FinishedSubscriber;
+
+/**
+ * Fires last for each test, after the outcome subscribers. Records the exact
+ * assertion count so replay can emit the same `addToAssertionCount()` instead
+ * of a hardcoded value.
+ *
+ * @internal
+ */
+final class EnsureTiaAssertionsAreRecordedOnFinished implements FinishedSubscriber
+{
+    public function __construct(private readonly ResultCollector $collector) {}
+
+    public function notify(Finished $event): void
+    {
+        $test = $event->test();
+
+        if ($test instanceof TestMethod) {
+            $this->collector->recordAssertions(
+                $test->className().'::'.$test->methodName(),
+                $event->numberOfAssertionsPerformed(),
+            );
+        }
+
+        // Close the "currently recording" window on Finished so the next
+        // test's events don't get mis-attributed. Keeping the pointer open
+        // through the outcome subscribers is what lets a late-firing
+        // `ConsideredRisky` overwrite an earlier `Passed`.
+        $this->collector->finishTest();
+    }
+}

src/Subscribers/EnsureTiaCoverageIsFlushed.php

@@ -0,0 +1,25 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Pest\Subscribers;
+
+use Pest\Plugins\Tia\Recorder;
+use PHPUnit\Event\Test\Finished;
+use PHPUnit\Event\Test\FinishedSubscriber;
+
+/**
+ * Stops PCOV collection after each test and merges the covered files into the
+ * TIA recorder's aggregate map. No-op unless the recorder is active.
+ *
+ * @internal
+ */
+final readonly class EnsureTiaCoverageIsFlushed implements FinishedSubscriber
+{
+    public function __construct(private Recorder $recorder) {}
+
+    public function notify(Finished $event): void
+    {
+        $this->recorder->endTest();
+    }
+}

src/Subscribers/EnsureTiaCoverageIsRecorded.php

@@ -0,0 +1,36 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Pest\Subscribers;
+
+use Pest\Plugins\Tia\Recorder;
+use PHPUnit\Event\Code\TestMethod;
+use PHPUnit\Event\Test\Prepared;
+use PHPUnit\Event\Test\PreparedSubscriber;
+
+/**
+ * Starts PCOV collection before each test. No-op unless the TIA recorder was
+ * activated by the `--tia` plugin.
+ *
+ * @internal
+ */
+final readonly class EnsureTiaCoverageIsRecorded implements PreparedSubscriber
+{
+    public function __construct(private Recorder $recorder) {}
+
+    public function notify(Prepared $event): void
+    {
+        if (! $this->recorder->isActive()) {
+            return;
+        }
+
+        $test = $event->test();
+
+        if (! $test instanceof TestMethod) {
+            return;
+        }
+
+        $this->recorder->beginTest($test->className(), $test->methodName(), $test->file());
+    }
+}

src/Subscribers/EnsureTiaResultIsRecordedOnErrored.php

@@ -0,0 +1,22 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Pest\Subscribers;
+
+use Pest\Plugins\Tia\ResultCollector;
+use PHPUnit\Event\Test\Errored;
+use PHPUnit\Event\Test\ErroredSubscriber;
+
+/**
+ * @internal
+ */
+final class EnsureTiaResultIsRecordedOnErrored implements ErroredSubscriber
+{
+    public function __construct(private readonly ResultCollector $collector) {}
+
+    public function notify(Errored $event): void
+    {
+        $this->collector->testErrored($event->throwable()->message());
+    }
+}

src/Subscribers/EnsureTiaResultIsRecordedOnFailed.php

@@ -0,0 +1,22 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Pest\Subscribers;
+
+use Pest\Plugins\Tia\ResultCollector;
+use PHPUnit\Event\Test\Failed;
+use PHPUnit\Event\Test\FailedSubscriber;
+
+/**
+ * @internal
+ */
+final class EnsureTiaResultIsRecordedOnFailed implements FailedSubscriber
+{
+    public function __construct(private readonly ResultCollector $collector) {}
+
+    public function notify(Failed $event): void
+    {
+        $this->collector->testFailed($event->throwable()->message());
+    }
+}

src/Subscribers/EnsureTiaResultIsRecordedOnIncomplete.php

@@ -0,0 +1,22 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Pest\Subscribers;
+
+use Pest\Plugins\Tia\ResultCollector;
+use PHPUnit\Event\Test\MarkedIncomplete;
+use PHPUnit\Event\Test\MarkedIncompleteSubscriber;
+
+/**
+ * @internal
+ */
+final class EnsureTiaResultIsRecordedOnIncomplete implements MarkedIncompleteSubscriber
+{
+    public function __construct(private readonly ResultCollector $collector) {}
+
+    public function notify(MarkedIncomplete $event): void
+    {
+        $this->collector->testIncomplete($event->throwable()->message());
+    }
+}

src/Subscribers/EnsureTiaResultIsRecordedOnPassed.php

@@ -0,0 +1,22 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Pest\Subscribers;
+
+use Pest\Plugins\Tia\ResultCollector;
+use PHPUnit\Event\Test\Passed;
+use PHPUnit\Event\Test\PassedSubscriber;
+
+/**
+ * @internal
+ */
+final class EnsureTiaResultIsRecordedOnPassed implements PassedSubscriber
+{
+    public function __construct(private readonly ResultCollector $collector) {}
+
+    public function notify(Passed $event): void
+    {
+        $this->collector->testPassed();
+    }
+}

src/Subscribers/EnsureTiaResultIsRecordedOnRisky.php

@@ -0,0 +1,22 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Pest\Subscribers;
+
+use Pest\Plugins\Tia\ResultCollector;
+use PHPUnit\Event\Test\ConsideredRisky;
+use PHPUnit\Event\Test\ConsideredRiskySubscriber;
+
+/**
+ * @internal
+ */
+final class EnsureTiaResultIsRecordedOnRisky implements ConsideredRiskySubscriber
+{
+    public function __construct(private readonly ResultCollector $collector) {}
+
+    public function notify(ConsideredRisky $event): void
+    {
+        $this->collector->testRisky($event->message());
+    }
+}

src/Subscribers/EnsureTiaResultIsRecordedOnSkipped.php

@@ -0,0 +1,22 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Pest\Subscribers;
+
+use Pest\Plugins\Tia\ResultCollector;
+use PHPUnit\Event\Test\Skipped;
+use PHPUnit\Event\Test\SkippedSubscriber;
+
+/**
+ * @internal
+ */
+final class EnsureTiaResultIsRecordedOnSkipped implements SkippedSubscriber
+{
+    public function __construct(private readonly ResultCollector $collector) {}
+
+    public function notify(Skipped $event): void
+    {
+        $this->collector->testSkipped($event->message());
+    }
+}

src/Subscribers/EnsureTiaResultsAreCollected.php

@@ -0,0 +1,35 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Pest\Subscribers;
+
+use Pest\Plugins\Tia\ResultCollector;
+use PHPUnit\Event\Code\TestMethod;
+use PHPUnit\Event\Test\Prepared;
+use PHPUnit\Event\Test\PreparedSubscriber;
+
+/**
+ * Starts a per-test recording window on Prepared. Sibling subscribers
+ * (`EnsureTia*`) close it with the outcome and the assertion count so the
+ * graph can persist everything needed for faithful replay.
+ *
+ * Why one subscriber per event: PHPUnit's `TypeMap::map()` picks only the
+ * first subscriber interface it finds on a class, so one class cannot fan
+ * out to multiple events — each event needs its own subscriber class.
+ *
+ * @internal
+ */
+final class EnsureTiaResultsAreCollected implements PreparedSubscriber
+{
+    public function __construct(private readonly ResultCollector $collector) {}
+
+    public function notify(Prepared $event): void
+    {
+        $test = $event->test();
+
+        if ($test instanceof TestMethod) {
+            $this->collector->testPrepared($test->className().'::'.$test->methodName());
+        }
+    }
+}

src/Support/Coverage.php

@@ -88,6 +88,12 @@ final class Coverage
             throw ShouldNotHappen::fromMessage(sprintf('Coverage not found in path: %s.', $reportPath));
         }
 
+        // If TIA's marker is present, this run executed only the affected
+        // tests. Merge their fresh coverage slice into the cached full-run
+        // snapshot (stored by the previous `--tia --coverage` pass) so the
+        // report reflects the entire suite, not just what re-ran.
+        \Pest\Plugins\Tia\CoverageMerger::applyIfMarked($reportPath);
+
         /** @var CodeCoverage $codeCoverage */
         $codeCoverage = require $reportPath;
         unlink($reportPath);

tests/.pest/snapshots/Visual/Help/visual_snapshot_of_help_command_output.snap

@@ -1,5 +1,5 @@
 
-  Pest Testing Framework 4.6.2.  
+  Pest Testing Framework 4.6.3.  
 
   USAGE: pest <file> [options]  
 

tests/.pest/snapshots/Visual/Version/visual_snapshot_of_help_command_output.snap

@@ -1,3 +1,3 @@
 
-  Pest Testing Framework 4.6.2.  
+  Pest Testing Framework 4.6.3.  
 

tests/Arch.php

@@ -7,6 +7,9 @@ arch()->preset()->php()->ignoring([
     'debug_backtrace',
     'var_export',
     'xdebug_info',
+    'xdebug_start_code_coverage',
+    'xdebug_stop_code_coverage',
+    'xdebug_get_code_coverage',
 ]);
 
 arch()->preset()->strict()->ignoring([