diff --git a/app/Jobs/ApplicationDeploymentJob.php b/app/Jobs/ApplicationDeploymentJob.php
index dd3f251c65..ec25b44b98 100644
--- a/app/Jobs/ApplicationDeploymentJob.php
+++ b/app/Jobs/ApplicationDeploymentJob.php
@@ -260,6 +260,8 @@ class ApplicationDeploymentJob implements ShouldBeEncrypted, ShouldQueue
         $source = data_get($this->application, 'source');
         if ($source) {
             $this->source = $source->getMorphClass()::where('id', $this->application->source->id)->first();
+            // Share one source instance so the job reuses its in-memory GitHub installation token.
+            $this->application->setRelation('source', $this->source);
         }
         $this->server = Server::find($this->application_deployment_queue->server_id);
         $this->timeout = $this->server->settings->dynamic_timeout;
diff --git a/app/Jobs/ProcessGithubPullRequestWebhook.php b/app/Jobs/ProcessGithubPullRequestWebhook.php
index 362ad0a2d8..8abef9a486 100644
--- a/app/Jobs/ProcessGithubPullRequestWebhook.php
+++ b/app/Jobs/ProcessGithubPullRequestWebhook.php
@@ -14,6 +14,7 @@ use Illuminate\Contracts\Queue\ShouldQueue;
 use Illuminate\Foundation\Bus\Dispatchable;
 use Illuminate\Queue\InteractsWithQueue;
 use Illuminate\Queue\SerializesModels;
+use Illuminate\Support\Facades\Log;
 use Throwable;
 
 class ProcessGithubPullRequestWebhook implements ShouldBeEncrypted, ShouldQueue
@@ -127,21 +128,34 @@ class ProcessGithubPullRequestWebhook implements ShouldBeEncrypted, ShouldQueue
             }
         }
 
-        // Get changed files for watch path filtering
-        $changed_files = collect();
+        // Get changed files for watch path filtering (null means the full list is unknown)
+        $changed_files = [];
 
         if ($this->action === 'synchronize' && $this->beforeSha && $this->afterSha) {
             // For synchronize events, get files changed between before and after commits
-            $changed_files = collect(getGithubCommitRangeFiles($githubApp, $owner, $repo, $this->beforeSha, $this->afterSha));
+            $changed_files = getGithubCommitRangeFiles($githubApp, $owner, $repo, $this->beforeSha, $this->afterSha);
         } elseif ($this->action === 'opened' || $this->action === 'reopened') {
             // For opened/reopened events, get all files in the PR
-            $changed_files = collect(getGithubPullRequestFiles($githubApp, $owner, $repo, $this->pullRequestId));
+            $changed_files = getGithubPullRequestFiles($githubApp, $owner, $repo, $this->pullRequestId);
         }
 
         // Apply watch path filtering
-        $is_watch_path_triggered = $application->isWatchPathsTriggered($changed_files);
-        if (! $is_watch_path_triggered && ! blank($application->watch_paths)) {
-            return;
+        if (! blank($application->watch_paths)) {
+            $logContext = [
+                'application_uuid' => $application->uuid,
+                'pull_request_id' => $this->pullRequestId,
+                'action' => $this->action,
+            ];
+
+            if (is_null($changed_files)) {
+                Log::warning('Could not get the full list of changed files from GitHub. Deploying the pull request preview without the watch paths check.', $logContext);
+            } elseif (! $application->isWatchPathsTriggered(collect($changed_files))) {
+                Log::info('Skipped GitHub pull request preview deployment because no changed file matches the watch paths.', $logContext + [
+                    'changed_files_count' => count($changed_files),
+                ]);
+
+                return;
+            }
         }
 
         // Create ApplicationPreview if not exists
diff --git a/app/Models/GithubApp.php b/app/Models/GithubApp.php
index 0052232fb1..c7e5385fff 100644
--- a/app/Models/GithubApp.php
+++ b/app/Models/GithubApp.php
@@ -57,6 +57,34 @@ class GithubApp extends BaseModel
         'webhook_secret',
     ];
 
+    /**
+     * Installation token kept in memory, so one job does not request a new token for each GitHub call.
+     *
+     * @var array{credentials: string, token: string, expires_at: int}|null
+     */
+    private ?array $installationTokenInMemory = null;
+
+    public function installationToken(): string
+    {
+        $credentials = implode('|', [$this->api_url, $this->app_id, $this->installation_id, $this->private_key_id]);
+        $cached = $this->installationTokenInMemory;
+
+        if ($cached && $cached['credentials'] === $credentials && $cached['expires_at'] > now()->getTimestamp()) {
+            return $cached['token'];
+        }
+
+        $token = generateGithubToken($this, 'installation');
+
+        // GitHub installation tokens expire after one hour; renew them well before that.
+        $this->installationTokenInMemory = [
+            'credentials' => $credentials,
+            'token' => $token,
+            'expires_at' => now()->addMinutes(50)->getTimestamp(),
+        ];
+
+        return $token;
+    }
+
     protected static function booted(): void
     {
         static::deleting(function (GithubApp $github_app) {
diff --git a/bootstrap/helpers/github.php b/bootstrap/helpers/github.php
index d66ffd88b8..46ab731e94 100644
--- a/bootstrap/helpers/github.php
+++ b/bootstrap/helpers/github.php
@@ -216,7 +216,7 @@ function generateGithubToken(GithubApp $source, string $type)
 
 function generateGithubInstallationToken(GithubApp $source)
 {
-    return generateGithubToken($source, 'installation');
+    return $source->installationToken();
 }
 
 function generateGithubJwt(GithubApp $source)
@@ -397,28 +397,29 @@ function loadRepositoryByPage(GithubApp $source, string $token, int $page)
         'repositories' => $json['repositories'],
     ];
 }
-function getGithubCommitRangeFiles(?GithubApp $source, string $owner, string $repo, string $beforeSha, string $afterSha): array
+/**
+ * Returns null when the full list of changed files is unknown (API error or truncated list).
+ */
+function getGithubCommitRangeFiles(?GithubApp $source, string $owner, string $repo, string $beforeSha, string $afterSha): ?array
 {
     try {
         if (! $source) {
             // Manual webhooks don't have GitHub App authentication
-            // Return empty array so watch paths are ignored (current behavior)
             return [];
         }
 
         $endpoint = "/repos/{$owner}/{$repo}/compare/{$beforeSha}...{$afterSha}";
-        $response = githubApi($source, $endpoint, 'get', null, false);
-
-        if (! $response) {
-            return [];
-        }
-
+        $response = githubApi($source, $endpoint);
         $files = collect(data_get($response, 'data.files', []));
 
+        // The compare API returns at most 300 files and cannot paginate them.
+        if ($files->count() >= 300) {
+            return null;
+        }
+
         return $files->pluck('filename')->filter()->values()->toArray();
     } catch (Exception $e) {
-
-        return [];
+        return null;
     }
 }
 
@@ -444,27 +445,34 @@ function getGithubCommitMessage(?GithubApp $source, string $owner, string $repo,
     }
 }
 
-function getGithubPullRequestFiles(?GithubApp $source, string $owner, string $repo, int $pullRequestId): array
+/**
+ * Returns null when the full list of changed files is unknown (API error or truncated list).
+ */
+function getGithubPullRequestFiles(?GithubApp $source, string $owner, string $repo, int $pullRequestId): ?array
 {
     try {
         if (! $source) {
             // Manual webhooks don't have GitHub App authentication
-            // Return empty array so watch paths are ignored (current behavior)
             return [];
         }
 
-        $endpoint = "/repos/{$owner}/{$repo}/pulls/{$pullRequestId}/files";
-        $response = githubApi($source, $endpoint, 'get', null, false);
+        // GitHub returns at most 100 files per page and 3000 files per pull request.
+        $perPage = 100;
+        $maxPages = 30;
+        $files = collect();
 
-        if (! $response) {
-            return [];
+        for ($page = 1; $page <= $maxPages; $page++) {
+            $endpoint = "/repos/{$owner}/{$repo}/pulls/{$pullRequestId}/files?per_page={$perPage}&page={$page}";
+            $pageFiles = collect(data_get(githubApi($source, $endpoint), 'data', []));
+            $files = $files->merge($pageFiles->pluck('filename'));
+
+            if ($pageFiles->count() < $perPage) {
+                return $files->filter()->values()->toArray();
+            }
         }
 
-        $files = collect(data_get($response, 'data', []));
-
-        return $files->pluck('filename')->filter()->values()->toArray();
+        return null;
     } catch (Exception $e) {
-
-        return [];
+        return null;
     }
 }
diff --git a/tests/Feature/GithubAppInstallationTokenTest.php b/tests/Feature/GithubAppInstallationTokenTest.php
new file mode 100644
index 0000000000..bb83df0636
--- /dev/null
+++ b/tests/Feature/GithubAppInstallationTokenTest.php
@@ -0,0 +1,79 @@
+<?php
+
+use App\Models\GithubApp;
+use App\Models\PrivateKey;
+use App\Models\Team;
+use Illuminate\Foundation\Testing\RefreshDatabase;
+use Illuminate\Http\Client\Request;
+use Illuminate\Support\Facades\Http;
+
+uses(RefreshDatabase::class);
+
+beforeEach(function () {
+    $this->team = Team::factory()->create();
+
+    openssl_pkey_export(openssl_pkey_new([
+        'private_key_bits' => 2048,
+        'private_key_type' => OPENSSL_KEYTYPE_RSA,
+    ]), $pemKey);
+
+    $this->githubApp = GithubApp::create([
+        'name' => 'Private GitHub App',
+        'api_url' => 'https://api.github.com',
+        'html_url' => 'https://github.com',
+        'app_id' => 12345,
+        'installation_id' => 67890,
+        'private_key_id' => PrivateKey::create([
+            'name' => 'GitHub App Key',
+            'private_key' => $pemKey,
+            'team_id' => $this->team->id,
+        ])->id,
+        'is_public' => false,
+        'team_id' => $this->team->id,
+    ]);
+
+    Http::fake([
+        'https://api.github.com/zen' => fn () => Http::response('Keep it logically awesome.', 200, [
+            'Date' => now()->toRfc7231String(),
+        ]),
+        'https://api.github.com/app/installations/*/access_tokens' => Http::sequence()
+            ->push(['token' => 'first-token'], 201)
+            ->push(['token' => 'second-token'], 201),
+    ]);
+});
+
+function githubInstallationTokenRequests(): int
+{
+    return Http::recorded(fn (Request $request): bool => str_ends_with($request->url(), '/access_tokens'))->count();
+}
+
+it('reuses the installation token of the same GitHub App instance', function () {
+    expect(generateGithubInstallationToken($this->githubApp))->toBe('first-token')
+        ->and(generateGithubInstallationToken($this->githubApp))->toBe('first-token')
+        ->and(githubInstallationTokenRequests())->toBe(1);
+});
+
+it('requests a new installation token after the in-memory token expires', function () {
+    generateGithubInstallationToken($this->githubApp);
+
+    $this->travel(51)->minutes();
+
+    expect(generateGithubInstallationToken($this->githubApp))->toBe('second-token')
+        ->and(githubInstallationTokenRequests())->toBe(2);
+});
+
+it('requests a new installation token when the GitHub App installation changes', function () {
+    generateGithubInstallationToken($this->githubApp);
+
+    $this->githubApp->installation_id = 11111;
+
+    expect(generateGithubInstallationToken($this->githubApp))->toBe('second-token')
+        ->and(githubInstallationTokenRequests())->toBe(2);
+});
+
+it('does not share the installation token between GitHub App instances', function () {
+    generateGithubInstallationToken($this->githubApp);
+
+    expect(generateGithubInstallationToken(GithubApp::find($this->githubApp->id)))->toBe('second-token')
+        ->and(githubInstallationTokenRequests())->toBe(2);
+});
diff --git a/tests/Feature/ProcessGithubPullRequestWebhookTest.php b/tests/Feature/ProcessGithubPullRequestWebhookTest.php
index 667a7643f0..1b5c3023c1 100644
--- a/tests/Feature/ProcessGithubPullRequestWebhookTest.php
+++ b/tests/Feature/ProcessGithubPullRequestWebhookTest.php
@@ -8,6 +8,7 @@ use App\Models\ApplicationPreview;
 use App\Models\Environment;
 use App\Models\GithubApp;
 use App\Models\InstanceSettings;
+use App\Models\PrivateKey;
 use App\Models\Project;
 use App\Models\Server;
 use App\Models\StandaloneDocker;
@@ -204,5 +205,227 @@ it('skips a GitHub pull request preview when the opened or reopened head commit
         ->and(ApplicationDeploymentQueue::where('application_id', $this->application->id)->where('pull_request_id', 42)->exists())->toBeFalse();
 
     Http::assertSent(fn (Request $request): bool => $request->url() === 'https://api.github.com/repos/example/repo/commits/head-sha');
-    Http::assertNotSent(fn (Request $request): bool => $request->url() === 'https://api.github.com/repos/example/repo/pulls/42/files');
+    Http::assertNotSent(fn (Request $request): bool => str_contains($request->url(), '/repos/example/repo/pulls/42/files'));
 })->with(['opened', 'reopened']);
+
+it('deploys an opened GitHub pull request preview when a watched file is beyond the first page of changed files', function () {
+    Queue::fake();
+
+    $this->application->update(['watch_paths' => 'apps/app/**']);
+    $this->application->settings->update([
+        'is_preview_deployments_enabled' => true,
+    ]);
+
+    $githubApp = GithubApp::create([
+        'name' => 'Public GitHub',
+        'api_url' => 'https://api.github.com',
+        'html_url' => 'https://github.com',
+        'is_public' => true,
+        'team_id' => $this->team->id,
+    ]);
+
+    $firstPage = collect(range(1, 100))->map(fn (int $i): array => ['filename' => ".github/workflows/workflow-{$i}.yml"])->all();
+
+    Http::fake([
+        'https://api.github.com/repos/example/repo/commits/head-sha' => Http::response([
+            'commit' => ['message' => 'feat: add app'],
+        ]),
+        'https://api.github.com/repos/example/repo/pulls/42/files?per_page=100&page=1' => Http::response($firstPage),
+        'https://api.github.com/repos/example/repo/pulls/42/files?per_page=100&page=2' => Http::response([
+            ['filename' => 'apps/app/index.ts'],
+        ]),
+    ]);
+
+    $job = new ProcessGithubPullRequestWebhook(
+        applicationId: $this->application->id,
+        githubAppId: $githubApp->id,
+        action: 'opened',
+        pullRequestId: 42,
+        pullRequestHtmlUrl: 'https://github.com/example/repo/pull/42',
+        pullRequestTitle: 'Add feature',
+        beforeSha: null,
+        afterSha: null,
+        commitSha: 'head-sha',
+        authorAssociation: 'OWNER',
+        fullName: 'example/repo',
+    );
+
+    $job->handle();
+
+    expect(ApplicationPreview::where('application_id', $this->application->id)->where('pull_request_id', 42)->exists())->toBeTrue()
+        ->and(ApplicationDeploymentQueue::where('application_id', $this->application->id)->where('pull_request_id', 42)->exists())->toBeTrue();
+
+    Http::assertSentCount(3);
+});
+
+it('deploys a GitHub pull request preview when the full list of changed files is unknown', function (string $action, array $filesResponse) {
+    Queue::fake();
+
+    $this->application->update(['watch_paths' => 'apps/app/**']);
+    $this->application->settings->update([
+        'is_preview_deployments_enabled' => true,
+    ]);
+
+    $githubApp = GithubApp::create([
+        'name' => 'Public GitHub',
+        'api_url' => 'https://api.github.com',
+        'html_url' => 'https://github.com',
+        'is_public' => true,
+        'team_id' => $this->team->id,
+    ]);
+
+    Http::fake([
+        'https://api.github.com/repos/example/repo/commits/*' => Http::response([
+            'commit' => ['message' => 'feat: add app'],
+        ]),
+        ...$filesResponse,
+    ]);
+
+    $job = new ProcessGithubPullRequestWebhook(
+        applicationId: $this->application->id,
+        githubAppId: $githubApp->id,
+        action: $action,
+        pullRequestId: 42,
+        pullRequestHtmlUrl: 'https://github.com/example/repo/pull/42',
+        pullRequestTitle: 'Add feature',
+        beforeSha: 'before-sha',
+        afterSha: 'after-sha',
+        commitSha: 'after-sha',
+        authorAssociation: 'OWNER',
+        fullName: 'example/repo',
+    );
+
+    $job->handle();
+
+    expect(ApplicationPreview::where('application_id', $this->application->id)->where('pull_request_id', 42)->exists())->toBeTrue()
+        ->and(ApplicationDeploymentQueue::where('application_id', $this->application->id)->where('pull_request_id', 42)->exists())->toBeTrue();
+})->with([
+    'opened with a GitHub API error' => fn () => ['opened', [
+        'https://api.github.com/repos/example/repo/pulls/42/files*' => Http::response(['message' => 'Server Error'], 500),
+    ]],
+    'synchronize with a GitHub API error' => fn () => ['synchronize', [
+        'https://api.github.com/repos/example/repo/compare/*' => Http::response(['message' => 'Server Error'], 500),
+    ]],
+    'synchronize with a truncated compare file list' => fn () => ['synchronize', [
+        'https://api.github.com/repos/example/repo/compare/*' => Http::response([
+            'files' => collect(range(1, 300))->map(fn (int $i): array => ['filename' => "docs/page-{$i}.md"])->all(),
+        ]),
+    ]],
+]);
+
+it('skips an opened GitHub pull request preview when no changed file matches the watch paths', function () {
+    Queue::fake();
+
+    $this->application->update(['watch_paths' => 'apps/app/**']);
+    $this->application->settings->update([
+        'is_preview_deployments_enabled' => true,
+    ]);
+
+    $githubApp = GithubApp::create([
+        'name' => 'Public GitHub',
+        'api_url' => 'https://api.github.com',
+        'html_url' => 'https://github.com',
+        'is_public' => true,
+        'team_id' => $this->team->id,
+    ]);
+
+    Http::fake([
+        'https://api.github.com/repos/example/repo/commits/head-sha' => Http::response([
+            'commit' => ['message' => 'docs: update readme'],
+        ]),
+        'https://api.github.com/repos/example/repo/pulls/42/files*' => Http::response([
+            ['filename' => 'README.md'],
+        ]),
+    ]);
+
+    $job = new ProcessGithubPullRequestWebhook(
+        applicationId: $this->application->id,
+        githubAppId: $githubApp->id,
+        action: 'opened',
+        pullRequestId: 42,
+        pullRequestHtmlUrl: 'https://github.com/example/repo/pull/42',
+        pullRequestTitle: 'Update docs',
+        beforeSha: null,
+        afterSha: null,
+        commitSha: 'head-sha',
+        authorAssociation: 'OWNER',
+        fullName: 'example/repo',
+    );
+
+    $job->handle();
+
+    expect(ApplicationPreview::where('application_id', $this->application->id)->where('pull_request_id', 42)->exists())->toBeFalse()
+        ->and(ApplicationDeploymentQueue::where('application_id', $this->application->id)->where('pull_request_id', 42)->exists())->toBeFalse();
+});
+
+it('uses one GitHub App installation token for all GitHub API calls of a pull request job', function () {
+    Queue::fake();
+
+    $this->application->update(['watch_paths' => 'apps/app/**']);
+    $this->application->settings->update([
+        'is_preview_deployments_enabled' => true,
+    ]);
+
+    openssl_pkey_export(openssl_pkey_new([
+        'private_key_bits' => 2048,
+        'private_key_type' => OPENSSL_KEYTYPE_RSA,
+    ]), $pemKey);
+
+    $githubApp = GithubApp::create([
+        'name' => 'Private GitHub App',
+        'api_url' => 'https://api.github.com',
+        'html_url' => 'https://github.com',
+        'app_id' => 12345,
+        'installation_id' => 67890,
+        'private_key_id' => PrivateKey::create([
+            'name' => 'GitHub App Key',
+            'private_key' => $pemKey,
+            'team_id' => $this->team->id,
+        ])->id,
+        'is_public' => false,
+        'team_id' => $this->team->id,
+    ]);
+
+    $firstPage = collect(range(1, 100))->map(fn (int $i): array => ['filename' => ".github/workflows/workflow-{$i}.yml"])->all();
+
+    Http::fake([
+        'https://api.github.com/zen' => Http::response('Keep it logically awesome.', 200, [
+            'Date' => now()->toRfc7231String(),
+        ]),
+        'https://api.github.com/app/installations/67890/access_tokens' => Http::response([
+            'token' => 'fake-installation-token',
+        ], 201),
+        'https://api.github.com/repos/example/repo/commits/head-sha' => Http::response([
+            'commit' => ['message' => 'feat: add app'],
+        ]),
+        'https://api.github.com/repos/example/repo/pulls/42/files?per_page=100&page=1' => Http::response($firstPage),
+        'https://api.github.com/repos/example/repo/pulls/42/files?per_page=100&page=2' => Http::response([
+            ['filename' => 'apps/app/index.ts'],
+        ]),
+    ]);
+
+    $job = new ProcessGithubPullRequestWebhook(
+        applicationId: $this->application->id,
+        githubAppId: $githubApp->id,
+        action: 'opened',
+        pullRequestId: 42,
+        pullRequestHtmlUrl: 'https://github.com/example/repo/pull/42',
+        pullRequestTitle: 'Add feature',
+        beforeSha: null,
+        afterSha: null,
+        commitSha: 'head-sha',
+        authorAssociation: 'OWNER',
+        fullName: 'example/repo',
+    );
+
+    $job->handle();
+
+    expect(ApplicationDeploymentQueue::where('application_id', $this->application->id)->where('pull_request_id', 42)->exists())->toBeTrue();
+
+    $tokenRequests = Http::recorded(fn (Request $request): bool => str_ends_with($request->url(), '/access_tokens'));
+    $repositoryRequests = Http::recorded(fn (Request $request): bool => str_contains($request->url(), '/repos/example/repo/'));
+
+    expect($tokenRequests)->toHaveCount(1)
+        ->and($repositoryRequests)->toHaveCount(3)
+        ->and($repositoryRequests->every(fn (array $pair): bool => $pair[0]->hasHeader('Authorization', 'Bearer fake-installation-token')))->toBeTrue();
+});