diff --git a/index.php b/index.php
index 1795b07..9f3392d 100644
--- a/index.php
+++ b/index.php
@@ -1208,6 +1208,10 @@ document.addEventListener('DOMContentLoaded', function () {
             const formData = new FormData();
             formData.append('person_id', personId);
             formData.append('process_id', processId);
+            if (instanceModalElement) {
+                instanceModalElement.dataset.lastPersonId = personId;
+                instanceModalElement.dataset.lastProcessId = processId;
+            }
             
             fetch('_init_single_instance.php', {
                 method: 'POST',
@@ -1225,7 +1229,7 @@ document.addEventListener('DOMContentLoaded', function () {
                             modalBody.innerHTML = html;
                         });
                 } else {
-                    alert('Błąd: ' + (data.error || 'Nieznany błąd'));
+                    alert('Błąd: ' + (data.error?.message || data.error || 'Nieznany błąd'));
                     btn.disabled = false;
                     btn.innerHTML = originalText;
                 }
@@ -1238,6 +1242,156 @@ document.addEventListener('DOMContentLoaded', function () {
             });
         });
     }
+    // --- Actions inside Instance Modal ---
+    if (instanceModalElement) {
+        instanceModalElement.addEventListener('click', function(event) {
+            // Apply Transition Button
+            if (event.target.classList.contains('apply-transition-btn')) {
+                event.preventDefault();
+                const btn = event.target;
+                const instanceId = btn.dataset.instanceId;
+                const transitionId = btn.dataset.transitionId;
+                
+                // Get form data if transition form exists
+                const form = instanceModalElement.querySelector('#transition-form');
+                const formData = new FormData();
+                formData.append('instanceId', instanceId);
+                formData.append('transitionId', transitionId);
+                
+                if (form) {
+                    const formElements = new FormData(form);
+                    for (let [key, value] of formElements.entries()) {
+                        formData.append('payload[' + key + ']', value);
+                    }
+                }
+                
+                const originalText = btn.innerHTML;
+                btn.disabled = true;
+                btn.innerHTML = '<span class="spinner-border spinner-border-sm"></span>...';
+                
+                fetch('_apply_transition.php', {
+                    method: 'POST',
+                    body: formData
+                })
+                .then(r => r.json())
+                .then(data => {
+                    if (data.success || !data.error) {
+                        // Reload modal content
+                        const personId = instanceModalElement.dataset.lastPersonId;
+                        const processId = instanceModalElement.dataset.lastProcessId;
+                        
+                        fetch(`_get_instance_details.php?person_id=${personId}&process_id=${processId}`)
+                            .then(r => r.text())
+                            .then(html => {
+                                instanceModalElement.querySelector('.modal-body').innerHTML = html;
+                            });
+                    } else {
+                        alert('Błąd: ' + (data.error?.message || 'Nieznany błąd'));
+                        btn.disabled = false;
+                        btn.innerHTML = originalText;
+                    }
+                })
+                .catch(err => {
+                    console.error(err);
+                    alert('Błąd sieci');
+                    btn.disabled = false;
+                    btn.innerHTML = originalText;
+                });
+            }
+            
+            // Add Note Button
+            if (event.target.id === 'addNoteBtn') {
+                event.preventDefault();
+                const btn = event.target;
+                const instanceId = btn.dataset.instanceId;
+                const noteMessage = instanceModalElement.querySelector('#noteMessage').value.trim();
+                
+                if (!noteMessage) {
+                    alert('Treść notatki nie może być pusta.');
+                    return;
+                }
+                
+                const formData = new FormData();
+                formData.append('instanceId', instanceId);
+                formData.append('transitionId', 'note');
+                formData.append('payload[message]', noteMessage);
+                
+                const originalText = btn.innerHTML;
+                btn.disabled = true;
+                btn.innerHTML = '<span class="spinner-border spinner-border-sm"></span>...';
+                
+                fetch('_apply_transition.php', {
+                    method: 'POST',
+                    body: formData
+                })
+                .then(r => r.json())
+                .then(data => {
+                    if (data.success || !data.error) {
+                        const personId = instanceModalElement.dataset.lastPersonId;
+                        const processId = instanceModalElement.dataset.lastProcessId;
+                        
+                        fetch(`_get_instance_details.php?person_id=${personId}&process_id=${processId}`)
+                            .then(r => r.text())
+                            .then(html => {
+                                instanceModalElement.querySelector('.modal-body').innerHTML = html;
+                            });
+                    } else {
+                        alert('Błąd: ' + (data.error?.message || 'Nieznany błąd'));
+                        btn.disabled = false;
+                        btn.innerHTML = originalText;
+                    }
+                })
+                .catch(err => {
+                    console.error(err);
+                    alert('Błąd sieci');
+                    btn.disabled = false;
+                    btn.innerHTML = originalText;
+                });
+            }
+        });
+        
+        instanceModalElement.addEventListener('change', function(event) {
+            // Task Checkbox
+            if (event.target.classList.contains('task-checkbox-modal')) {
+                const checkbox = event.target;
+                const container = checkbox.closest('.checklist-modal-container');
+                const instanceId = container.dataset.instanceId;
+                const taskCode = checkbox.dataset.taskCode;
+                const isChecked = checkbox.checked;
+                
+                fetch('_update_training_checklist_status.php', {
+                    method: 'POST',
+                    headers: { 'Content-Type': 'application/json' },
+                    body: JSON.stringify({
+                        instance_id: instanceId,
+                        task_code: taskCode,
+                        is_checked: isChecked
+                    })
+                })
+                .then(r => r.json())
+                .then(data => {
+                    if (data.error) {
+                        alert('Błąd: ' + (data.error?.message || 'Nieznany błąd'));
+                        checkbox.checked = !isChecked; // revert
+                    }
+                })
+                .catch(err => {
+                    console.error(err);
+                    alert('Błąd sieci');
+                    checkbox.checked = !isChecked; // revert
+                });
+            }
+        });
+        
+        // Save personId and processId on modal show so we can use it to reload later
+        instanceModalElement.addEventListener('show.bs.modal', function (event) {
+            var button = event.relatedTarget;
+            if(button && button.dataset) {
+                if (button.dataset.personId) instanceModalElement.dataset.lastPersonId = button.dataset.personId;
+                if (button.dataset.processId) instanceModalElement.dataset.lastProcessId = button.dataset.processId;
+            }
+        });
+    }
 });
 </script>
 <?php include '_footer.php'; ?>
diff --git a/lib/WorkflowExceptions.php b/lib/WorkflowExceptions.php
index dbcac1d..d6fdc54 100644
--- a/lib/WorkflowExceptions.php
+++ b/lib/WorkflowExceptions.php
@@ -5,7 +5,7 @@ class WorkflowException extends Exception {
     protected $details;
 
     public function __construct($message = "", $httpCode = 500, $details = [], Throwable $previous = null) {
-        parent::__construct($message, 0, $previous);
+        parent::__construct($message, $httpCode, $previous);
         $this->httpCode = $httpCode;
         $this->details = $details;
     }
@@ -19,19 +19,33 @@ class WorkflowException extends Exception {
     }
 }
 
-class WorkflowNotFoundException extends Exception {}
-class WorkflowNotAllowedException extends Exception {}
-class WorkflowRuleFailedException extends Exception {}
+class WorkflowNotFoundException extends WorkflowException {
+    public function __construct($message = "") {
+        parent::__construct($message, 404);
+    }
+}
 
-class WorkflowEligibilityException extends Exception {
+class WorkflowNotAllowedException extends WorkflowException {
+    public function __construct($message = "") {
+        parent::__construct($message, 403);
+    }
+}
+
+class WorkflowRuleFailedException extends WorkflowException {
+    public function __construct($message = "") {
+        parent::__construct($message, 400);
+    }
+}
+
+class WorkflowEligibilityException extends WorkflowException {
     private $reasons;
 
-    public function __construct($message = "", $reasons = [], $code = 0, Throwable $previous = null) {
-        parent::__construct($message, $code, $previous);
+    public function __construct($message = "", $reasons = []) {
+        parent::__construct($message, 422, ['reasons' => $reasons]);
         $this->reasons = $reasons;
     }
 
     public function getReasons() {
         return $this->reasons;
     }
-}
+}
\ No newline at end of file