diff --git a/assets/js/components/GitContributionChart.vue b/assets/js/components/GitContributionChart.vue
index 277f261..a1854e2 100644
--- a/assets/js/components/GitContributionChart.vue
+++ b/assets/js/components/GitContributionChart.vue
@@ -130,9 +130,6 @@ const contributionGrid = computed(() => {
     contributionMap[day.date] = day.count
   })
   
-  // Debug: Log contribution map
-  console.log('Contribution map sample:', Object.entries(contributionMap).slice(0, 10))
-  
   let col = 1
   let currentDate = new Date(firstSunday)
   const lastDay = new Date(currentYear.value, 11, 31)
@@ -173,11 +170,6 @@ const contributionGrid = computed(() => {
     currentDate.setDate(currentDate.getDate() + 1)
   }
   
-  // Debug: Log grid sample
-  const gridWithCommits = grid.filter(g => g.count > 0)
-  console.log('Grid cells with commits:', gridWithCommits.length)
-  console.log('Sample cells with commits:', gridWithCommits.slice(0, 5))
-  
   return grid
 })
 
@@ -309,11 +301,6 @@ async function loadContributions() {
 
     const data = await response.json()
     contributionData.value = data.contributions || []
-    
-    // Debug: Log the data to check format
-    console.log('Contribution data received:', contributionData.value.slice(0, 5))
-    console.log('Total days:', contributionData.value.length)
-    console.log('Days with commits:', contributionData.value.filter(d => d.count > 0).length)
   } catch (err) {
     console.error('Error loading contributions:', err)
     error.value = err.message
@@ -433,6 +420,11 @@ defineExpose({
   transition: all 0.15s ease;
   min-height: 13px;
   min-width: 13px;
+  border: 1px solid rgba(0, 0, 0, 0.06);
+}
+
+:global(.dark) .contribution-cell {
+  border: 1px solid rgba(255, 255, 255, 0.08);
 }
 
 .contribution-cell:not(.intensity-empty):hover {
diff --git a/assets/js/views/ProjectManagement.vue b/assets/js/views/ProjectManagement.vue
index 2711bc0..e386aff 100644
--- a/assets/js/views/ProjectManagement.vue
+++ b/assets/js/views/ProjectManagement.vue
@@ -711,6 +711,15 @@
                 :use-grouping="false"
                 class="w-10rem"
               />
+              <Button
+                v-if="selectedRepository"
+                icon="pi pi-refresh"
+                label="Cache aktualisieren"
+                size="small"
+                outlined
+                :loading="refreshingCache"
+                @click="refreshRepositoryCache"
+              />
             </div>
 
             <!-- Contribution Chart -->
@@ -782,6 +791,7 @@ const gitRepositories = ref([])
 const selectedRepository = ref(null)
 const selectedBranch = ref('main')
 const selectedYear = ref(new Date().getFullYear())
+const refreshingCache = ref(false)
 
 // Git Repository Management
 const editGitRepositories = ref([])
@@ -1302,6 +1312,48 @@ async function deleteProject() {
   }
 }
 
+async function refreshRepositoryCache() {
+  if (!selectedRepository.value) return
+  
+  refreshingCache.value = true
+  
+  try {
+    const response = await fetch(`/api/git-repos/${selectedRepository.value.id}/refresh-cache`, {
+      method: 'POST',
+      headers: {
+        'Content-Type': 'application/json'
+      }
+    })
+    
+    if (!response.ok) {
+      const errorData = await response.json()
+      throw new Error(errorData.error || 'Cache konnte nicht aktualisiert werden')
+    }
+    
+    const result = await response.json()
+    
+    toast.add({
+      severity: 'success',
+      summary: 'Erfolg',
+      detail: result.message || 'Cache wurde aktualisiert',
+      life: 3000
+    })
+    
+    // Reload git data
+    await loadGitRepositories(viewingProject.value.id)
+  } catch (error) {
+    console.error('Error refreshing cache:', error)
+    toast.add({
+      severity: 'error',
+      summary: 'Fehler',
+      detail: error.message || 'Cache konnte nicht aktualisiert werden',
+      life: 3000
+    })
+  } finally {
+    refreshingCache.value = false
+  }
+}
+
 function formatDate(dateString) {
   if (!dateString) return ''
   const date = new Date(dateString)
diff --git a/composer.json b/composer.json
index da19a41..a39d08f 100644
--- a/composer.json
+++ b/composer.json
@@ -20,6 +20,7 @@
         "phpstan/phpdoc-parser": "^2.3",
         "symfony/asset": "7.1.*",
         "symfony/asset-mapper": "7.1.*",
+        "symfony/cache": "7.1.*",
         "symfony/console": "7.1.*",
         "symfony/doctrine-messenger": "7.1.*",
         "symfony/dotenv": "7.1.*",
diff --git a/composer.lock b/composer.lock
index e288264..0608a85 100644
--- a/composer.lock
+++ b/composer.lock
@@ -4,7 +4,7 @@
         "Read more about it at https://getcomposer.org/doc/01-basic-usage.md#installing-dependencies",
         "This file is @generated automatically"
     ],
-    "content-hash": "af57c523401fba0e523501b76e0629f0",
+    "content-hash": "c70cc2a152b707d0dcf4c562bd06f8d5",
     "packages": [
         {
             "name": "api-platform/core",
diff --git a/src/Controller/GitRepositoryController.php b/src/Controller/GitRepositoryController.php
index 6105c38..452ad15 100644
--- a/src/Controller/GitRepositoryController.php
+++ b/src/Controller/GitRepositoryController.php
@@ -12,6 +12,8 @@ use Symfony\Component\HttpFoundation\JsonResponse;
 use Symfony\Component\HttpFoundation\Request;
 use Symfony\Component\HttpFoundation\Response;
 use Symfony\Component\Routing\Annotation\Route;
+use Symfony\Contracts\Cache\CacheInterface;
+use Symfony\Contracts\Cache\ItemInterface;
 
 #[Route('/api/git-repos')]
 class GitRepositoryController extends AbstractController
@@ -20,7 +22,8 @@ class GitRepositoryController extends AbstractController
         private GitService $gitService,
         private GitHubService $githubService,
         private GiteaService $giteaService,
-        private EntityManagerInterface $em
+        private EntityManagerInterface $em,
+        private CacheInterface $cache
     ) {
     }
 
@@ -31,22 +34,33 @@ class GitRepositoryController extends AbstractController
             $limit = (int)$request->query->get('limit', 100);
             $branch = $request->query->get('branch', $gitRepo->getBranch() ?? 'main');
 
-            // Choose service based on provider
-            if ($gitRepo->getProvider() === 'github') {
-                $commits = $this->getCommitsFromGitHub($gitRepo, $branch, $limit);
-            } elseif ($gitRepo->getProvider() === 'gitea') {
-                $commits = $this->getCommitsFromGitea($gitRepo, $branch, $limit);
-            } elseif ($gitRepo->getLocalPath()) {
-                $commits = $this->gitService->getCommits(
-                    $gitRepo->getLocalPath(),
-                    $branch,
-                    $limit
-                );
-            } else {
-                return $this->json([
-                    'error' => 'No data source configured (neither provider API nor local path)'
-                ], Response::HTTP_BAD_REQUEST);
-            }
+            // Cache key unique per repository, branch, and limit
+            $cacheKey = sprintf(
+                'git_commits_%d_%s_%d',
+                $gitRepo->getId(),
+                md5($branch),
+                $limit
+            );
+
+            $commits = $this->cache->get($cacheKey, function (ItemInterface $item) use ($gitRepo, $branch, $limit) {
+                // Cache for 15 minutes (commits change frequently during active development)
+                $item->expiresAfter(900);
+                
+                // Choose service based on provider
+                if ($gitRepo->getProvider() === 'github') {
+                    return $this->getCommitsFromGitHub($gitRepo, $branch, $limit);
+                } elseif ($gitRepo->getProvider() === 'gitea') {
+                    return $this->getCommitsFromGitea($gitRepo, $branch, $limit);
+                } elseif ($gitRepo->getLocalPath()) {
+                    return $this->gitService->getCommits(
+                        $gitRepo->getLocalPath(),
+                        $branch,
+                        $limit
+                    );
+                }
+                
+                throw new \Exception('No data source configured (neither provider API nor local path)');
+            });
 
             // Update last sync timestamp
             $gitRepo->setLastSync(new \DateTime());
@@ -89,23 +103,35 @@ class GitRepositoryController extends AbstractController
             $author = $request->query->get('author');
             $year = (int)$request->query->get('year', date('Y'));
 
-            // Choose service based on provider
-            if ($gitRepo->getProvider() === 'github') {
-                $contributions = $this->getContributionsFromGitHub($gitRepo, $year);
-            } elseif ($gitRepo->getProvider() === 'gitea') {
-                $contributions = $this->getContributionsFromGitea($gitRepo, $branch, $author, $year);
-            } elseif ($gitRepo->getLocalPath()) {
-                $contributions = $this->gitService->getContributions(
-                    $gitRepo->getLocalPath(),
-                    $branch,
-                    $author,
-                    $year
-                );
-            } else {
-                return $this->json([
-                    'error' => 'No data source configured (neither provider API nor local path)'
-                ], Response::HTTP_BAD_REQUEST);
-            }
+            // Cache key unique per repository, branch, author, and year
+            $cacheKey = sprintf(
+                'git_contributions_%d_%s_%s_%d',
+                $gitRepo->getId(),
+                md5($branch),
+                md5($author ?? 'all'),
+                $year
+            );
+
+            $contributions = $this->cache->get($cacheKey, function (ItemInterface $item) use ($gitRepo, $branch, $author, $year) {
+                // Cache for 1 hour (contributions data is relatively stable)
+                $item->expiresAfter(3600);
+                
+                // Choose service based on provider
+                if ($gitRepo->getProvider() === 'github') {
+                    return $this->getContributionsFromGitHub($gitRepo, $year);
+                } elseif ($gitRepo->getProvider() === 'gitea') {
+                    return $this->getContributionsFromGitea($gitRepo, $branch, $author, $year);
+                } elseif ($gitRepo->getLocalPath()) {
+                    return $this->gitService->getContributions(
+                        $gitRepo->getLocalPath(),
+                        $branch,
+                        $author,
+                        $year
+                    );
+                }
+                
+                throw new \Exception('No data source configured (neither provider API nor local path)');
+            });
 
             // Update last sync timestamp
             $gitRepo->setLastSync(new \DateTime());
@@ -141,6 +167,55 @@ class GitRepositoryController extends AbstractController
         return $this->giteaService->getContributions($parsed['baseUrl'], $parsed['owner'], $parsed['repo'], $branch, $author, $year);
     }
 
+    #[Route('/{id}/refresh-cache', name: 'api_git_repo_refresh_cache', methods: ['POST'])]
+    public function refreshCache(GitRepository $gitRepo): JsonResponse
+    {
+        $this->denyAccessUnlessGranted('IS_AUTHENTICATED_FULLY');
+        
+        try {
+            // Invalidate all cache entries for this repository
+            $repoId = $gitRepo->getId();
+            $years = range(date('Y') - 2, date('Y') + 1); // Last 2 years + current + next
+            $deletedKeys = [];
+            
+            // Delete contribution caches for multiple years
+            foreach ($years as $year) {
+                $patterns = [
+                    sprintf('git_contributions_%d_*_%d', $repoId, $year),
+                ];
+                foreach ($patterns as $pattern) {
+                    // Note: Pattern deletion requires specific cache adapter support
+                    // For filesystem cache, we need to delete specific known keys
+                    $key = sprintf('git_contributions_%d_%s_all_%d', $repoId, md5('main'), $year);
+                    if ($this->cache->delete($key)) {
+                        $deletedKeys[] = $key;
+                    }
+                }
+            }
+            
+            // Delete commit caches
+            $commitKey = sprintf('git_commits_%d_%s_100', $repoId, md5('main'));
+            if ($this->cache->delete($commitKey)) {
+                $deletedKeys[] = $commitKey;
+            }
+            
+            // Update last sync timestamp
+            $gitRepo->setLastSync(new \DateTime());
+            $this->em->flush();
+            
+            return $this->json([
+                'success' => true,
+                'message' => 'Cache erfolgreich invalidiert. Nächste Anfrage lädt frische Daten.',
+                'deletedKeys' => count($deletedKeys)
+            ]);
+        } catch (\Exception $e) {
+            return $this->json([
+                'success' => false,
+                'error' => 'Cache-Invalidierung fehlgeschlagen: ' . $e->getMessage()
+            ], Response::HTTP_INTERNAL_SERVER_ERROR);
+        }
+    }
+
     #[Route('/{id}/branches', name: 'api_git_repo_branches', methods: ['GET'])]
     public function getBranches(GitRepository $gitRepo): JsonResponse
     {
diff --git a/src/EventListener/GitRepositoryCacheListener.php b/src/EventListener/GitRepositoryCacheListener.php
new file mode 100644
index 0000000..d20a740
--- /dev/null
+++ b/src/EventListener/GitRepositoryCacheListener.php
@@ -0,0 +1,62 @@
+<?php
+
+namespace App\EventListener;
+
+use App\Entity\GitRepository;
+use Doctrine\Bundle\DoctrineBundle\Attribute\AsEntityListener;
+use Doctrine\ORM\Event\PreUpdateEventArgs;
+use Doctrine\ORM\Event\PreRemoveEventArgs;
+use Doctrine\ORM\Events;
+use Symfony\Contracts\Cache\CacheInterface;
+
+#[AsEntityListener(event: Events::preUpdate, entity: GitRepository::class)]
+#[AsEntityListener(event: Events::preRemove, entity: GitRepository::class)]
+class GitRepositoryCacheListener
+{
+    public function __construct(
+        private CacheInterface $cache
+    ) {
+    }
+
+    public function preUpdate(GitRepository $gitRepo, PreUpdateEventArgs $event): void
+    {
+        // Only invalidate if relevant fields changed
+        if ($event->hasChangedField('branch') || 
+            $event->hasChangedField('url') ||
+            $event->hasChangedField('localPath') ||
+            $event->hasChangedField('provider')) {
+            $this->invalidateRepositoryCache($gitRepo);
+        }
+    }
+
+    public function preRemove(GitRepository $gitRepo, PreRemoveEventArgs $event): void
+    {
+        $this->invalidateRepositoryCache($gitRepo);
+    }
+
+    private function invalidateRepositoryCache(GitRepository $gitRepo): void
+    {
+        // Delete all cache entries for this repository
+        $repoId = $gitRepo->getId();
+        $years = range(date('Y') - 2, date('Y') + 1);
+        
+        // Delete contribution caches
+        foreach ($years as $year) {
+            // Delete for common branches and author combinations
+            $branches = ['main', 'master', 'develop'];
+            foreach ($branches as $branch) {
+                $key = sprintf('git_contributions_%d_%s_all_%d', $repoId, md5($branch), $year);
+                $this->cache->delete($key);
+            }
+        }
+        
+        // Delete commit caches
+        $limits = [50, 100, 200];
+        foreach ($limits as $limit) {
+            foreach (['main', 'master', 'develop'] as $branch) {
+                $key = sprintf('git_commits_%d_%s_%d', $repoId, md5($branch), $limit);
+                $this->cache->delete($key);
+            }
+        }
+    }
+}