diff --git a/api.php b/api.php
index 4c3d1a2..9e37142 100644
--- a/api.php
+++ b/api.php
@@ -42,7 +42,7 @@ function get_csv_sample($filePath) {
     return implode('\n', $sample);
 }
 
-function call_openai_api($inputSample, $outputSample) {
+function call_openai_api($inputSample, $outputSample, $customInstructions) {
     $apiKey = getenv('OPENAI_API_KEY');
     if (!$apiKey) {
         return ['error' => 'OpenAI API key not configured.'];
@@ -50,7 +50,10 @@ function call_openai_api($inputSample, $outputSample) {
 
     $prompt = "I have two CSV files. I want to convert the input file to the output file format.\n\n";
     $prompt .= "Here is a sample of the input CSV file:\n---\n" . $inputSample . "\n---\n\n";
-    $prompt .= "Here is a sample of the output CSV file:\n---\n" . $outputSample . "\n---\n\n";
+    $prompt .= "Here is a sample of the output CSV file:\n---" . $outputSample . "---\n\n";
+    if (!empty($customInstructions)) {
+        $prompt .= "Additionally, here are some custom instructions to follow:\n---" . $customInstructions . "---\n\n";
+    }
     $prompt .= "Please generate a PHP script that contains a single function `convert_csv($input_file_path, $output_file_path)`.\n";
     $prompt .= "This function should read the data from the `$input_file_path`, transform it into the format of the output sample, and write the result to `$output_file_path`.\n";
     $prompt .= "The script should handle CSV headers correctly. Do not include any explanations, just the raw PHP code starting with `<?php`.";
@@ -103,6 +106,32 @@ function call_openai_api($inputSample, $outputSample) {
 load_env(__DIR__ . '/.env');
 $action = $_POST['action'] ?? $_GET['action'] ?? '';
 
+function sanitize_filename($filename) {
+    // Remove PHP extension if present
+    if (substr($filename, -4) === '.php') {
+        $filename = substr($filename, 0, -4);
+    }
+    // Replace spaces and special characters with hyphens
+    $filename = preg_replace('/[^a-zA-Z0-9_\.-]/', '-', $filename);
+    // Remove leading/trailing hyphens
+    $filename = trim($filename, '-');
+    // Ensure it's not empty
+    if (empty($filename)) {
+        return 'mapping-' . time();
+    }
+    return $filename . '.php';
+}
+
+if ($action === 'list_mappings') {
+    $mappingDir = __DIR__ . '/mappings';
+    $files = glob($mappingDir . '/*.php');
+    $mappings = array_map(function($file) {
+        return basename($file);
+    }, $files);
+    echo json_encode(['success' => true, 'mappings' => $mappings]);
+    exit;
+}
+
 if ($action === 'build_mapping') {
     if (!isset($_FILES['inputSample']) || !isset($_FILES['outputSample'])) {
         echo json_encode(['success' => false, 'error' => 'Input and output sample files are required.']);
@@ -114,13 +143,14 @@ if ($action === 'build_mapping') {
 
     $inputSampleContent = get_csv_sample($inputTmpPath);
     $outputSampleContent = get_csv_sample($outputTmpPath);
+    $customInstructions = $_POST['customInstructions'] ?? '';
 
     if ($inputSampleContent === null || $outputSampleContent === null) {
         echo json_encode(['success' => false, 'error' => 'Failed to read sample files.']);
         exit;
     }
 
-    $result = call_openai_api($inputSampleContent, $outputSampleContent);
+    $result = call_openai_api($inputSampleContent, $outputSampleContent, $customInstructions);
 
     if (isset($result['error'])) {
         echo json_encode(['success' => false, 'error' => $result['error'], 'details' => $result['details'] ?? null]);
@@ -131,10 +161,20 @@ if ($action === 'build_mapping') {
     if (!is_dir($mappingDir)) {
         mkdir($mappingDir, 0775, true);
     }
-    $mappingFile = 'mappings/mapping_' . time() . '.php';
-    file_put_contents($mappingFile, $result['code']);
 
-    echo json_encode(['success' => true, 'mapping_file' => $mappingFile]);
+    $mappingName = $_POST['mappingName'] ?? '';
+    if (empty($mappingName)) {
+        $inputName = pathinfo($_FILES['inputSample']['name'], PATHINFO_FILENAME);
+        $outputName = pathinfo($_FILES['outputSample']['name'], PATHINFO_FILENAME);
+        $mappingName = $inputName . '-to-' . $outputName;
+    }
+
+    $mappingFile = sanitize_filename($mappingName);
+    $mappingPath = $mappingDir . '/' . $mappingFile;
+
+    file_put_contents($mappingPath, $result['code']);
+
+    echo json_encode(['success' => true, 'mapping_file' => 'mappings/' . $mappingFile]);
     exit;
 }
 
diff --git a/assets/js/main.js b/assets/js/main.js
index ad989d5..c26aec4 100644
--- a/assets/js/main.js
+++ b/assets/js/main.js
@@ -8,8 +8,8 @@ document.addEventListener('DOMContentLoaded', function () {
 
     const fullInputFile = document.getElementById('fullInputFile');
     const convertBtn = document.getElementById('convertBtn');
+    const existingMappings = document.getElementById('existingMappings');
 
-    const convertSection = document.getElementById('convertSection');
     const convertResult = document.getElementById('convertResult');
     const mappingFileInput = document.getElementById('mappingFile');
 
@@ -17,13 +17,41 @@ document.addEventListener('DOMContentLoaded', function () {
         buildMappingBtn.disabled = !(inputSample.files.length > 0 && outputSample.files.length > 0);
     }
 
-    function checkConvertFile() {
-        convertBtn.disabled = !(fullInputFile.files.length > 0);
+    function checkConvertState() {
+        const mappingSelected = mappingFileInput.value !== '';
+        const fileSelected = fullInputFile.files.length > 0;
+        convertBtn.disabled = !(mappingSelected && fileSelected);
+    }
+
+    function loadMappings() {
+        fetch('api.php?action=list_mappings')
+            .then(response => response.json())
+            .then(data => {
+                if (data.success && data.mappings.length > 0) {
+                    existingMappings.innerHTML = '<option value="" selected>Select a mapping</option>';
+                    data.mappings.forEach(mapping => {
+                        const option = document.createElement('option');
+                        option.value = `mappings/${mapping}`;
+                        option.textContent = mapping;
+                        existingMappings.appendChild(option);
+                    });
+                } else {
+                    existingMappings.innerHTML = '<option value="" selected>No mappings found</option>';
+                }
+            })
+            .catch(error => {
+                console.error('Error loading mappings:', error);
+                existingMappings.innerHTML = '<option value="" selected>Error loading mappings</option>';
+            });
     }
 
     inputSample.addEventListener('change', checkMappingFiles);
     outputSample.addEventListener('change', checkMappingFiles);
-    fullInputFile.addEventListener('change', checkConvertFile);
+    fullInputFile.addEventListener('change', checkConvertState);
+    existingMappings.addEventListener('change', function() {
+        mappingFileInput.value = this.value;
+        checkConvertState();
+    });
 
     mappingForm.addEventListener('submit', function (e) {
         e.preventDefault();
@@ -42,7 +70,12 @@ document.addEventListener('DOMContentLoaded', function () {
             if (data.success) {
                 alert('Mapping built successfully!');
                 mappingFileInput.value = data.mapping_file;
-                convertSection.classList.remove('d-none');
+                loadMappings(); // Refresh the list
+                // Select the new mapping in the dropdown
+                setTimeout(() => {
+                    existingMappings.value = data.mapping_file;
+                    checkConvertState();
+                }, 500); // Give it a moment to reload
             } else {
                 let errorMsg = 'Error building mapping: ' + data.error;
                 if(data.details) {
@@ -89,6 +122,10 @@ document.addEventListener('DOMContentLoaded', function () {
         .finally(() => {
             convertBtn.disabled = false;
             convertBtn.innerHTML = '<i class="fas fa-sync-alt me-2"></i>Convert';
+            checkConvertState();
         });
     });
-});
\ No newline at end of file
+
+    // Initial load
+    loadMappings();
+});
diff --git a/index.php b/index.php
index 97524a7..b0bd09c 100644
--- a/index.php
+++ b/index.php
@@ -29,19 +29,33 @@
 
     <main class="container my-5">
         <div class="row g-5">
-            <div class="col-lg-6">
-                <div class="card h-100">
-                    <div class="card-body d-flex flex-column">
-                        <h2 class="card-title h4 mb-4"><span class="badge bg-primary me-2">1</span>Build Mapping</h2>
+            <div class="col-12">
+                <div class="card">
+                    <div class="card-body">
+                        <h2 class="card-title h4 mb-4"><span class="badge bg-primary me-2">1</span>Build New Mapping</h2>
                         <p class="text-muted">Provide input and output sample files (CSV or XLSX) to generate a mapping configuration using AI.</p>
-                        <form id="mappingForm" class="mt-auto">
-                            <div class="mb-3">
-                                <label for="inputSample" class="form-label">Input Sample</label>
-                                <input class="form-control" type="file" id="inputSample" name="inputSample" accept=".csv, .xlsx" required>
+                        <form id="mappingForm">
+                            <div class="row">
+                                <div class="col-md-6">
+                                    <div class="mb-3">
+                                        <label for="inputSample" class="form-label">Input Sample</label>
+                                        <input class="form-control" type="file" id="inputSample" name="inputSample" accept=".csv, .xlsx" required>
+                                    </div>
+                                </div>
+                                <div class="col-md-6">
+                                    <div class="mb-3">
+                                        <label for="outputSample" class="form-label">Output Sample</label>
+                                        <input class="form-control" type="file" id="outputSample" name="outputSample" accept=".csv, .xlsx" required>
+                                    </div>
+                                </div>
                             </div>
                             <div class="mb-3">
-                                <label for="outputSample" class="form-label">Output Sample</label>
-                                <input class="form-control" type="file" id="outputSample" name="outputSample" accept=".csv, .xlsx" required>
+                                <label for="mappingName" class="form-label">Mapping Name (Optional)</label>
+                                <input type="text" class="form-control" id="mappingName" name="mappingName" placeholder="e.g., my-custom-mapping">
+                            </div>
+                            <div class="mb-3">
+                                <label for="customInstructions" class="form-label">Custom Instructions (Optional)</label>
+                                <textarea class="form-control" id="customInstructions" name="customInstructions" rows="3" placeholder="e.g., map this field to that, use ; instead of ,"></textarea>
                             </div>
                             <button type="submit" id="buildMappingBtn" class="btn btn-primary w-100" disabled>
                                 <i class="fas fa-cogs me-2"></i>Build Mapping
@@ -50,18 +64,34 @@
                     </div>
                 </div>
             </div>
-            <div id="convertSection" class="col-lg-6 d-none">
-                <div class="card h-100">
-                    <div class="card-body d-flex flex-column">
-                        <h2 class="card-title h4 mb-4"><span class="badge bg-secondary me-2">2</span>Convert Data</h2>
-                        <p class="text-muted">Use the generated mapping to convert your full input file.</p>
-                        <form id="convertForm" class="mt-auto">
+        </div>
+
+        <hr class="my-5">
+
+        <div id="convertSection" class="row g-5">
+            <div class="col-12">
+                <div class="card">
+                    <div class="card-body">
+                        <h2 class="card-title h4 mb-4"><span class="badge bg-secondary me-2">2</span>Convert Data with Mapping</h2>
+                        <form id="convertForm">
                             <input type="hidden" id="mappingFile" name="mappingFile">
-                            <div class="mb-3">
-                                <label for="fullInputFile" class="form-label">Full Input File</label>
-                                <input class="form-control" type="file" id="fullInputFile" name="fullInputFile" accept=".csv, .xlsx" required>
+                            <div class="row align-items-end">
+                                <div class="col-md-6">
+                                    <div class="mb-3">
+                                        <label for="existingMappings" class="form-label">Use Existing Mapping</label>
+                                        <select class="form-select" id="existingMappings" name="existingMappings">
+                                            <option value="" selected>Select a mapping</option>
+                                        </select>
+                                    </div>
+                                </div>
+                                <div class="col-md-6">
+                                    <div class="mb-3">
+                                        <label for="fullInputFile" class="form-label">Full Input File</label>
+                                        <input class="form-control" type="file" id="fullInputFile" name="fullInputFile" accept=".csv, .xlsx" required>
+                                    </div>
+                                </div>
                             </div>
-                            <button type="submit" id="convertBtn" class="btn btn-secondary w-100" disabled>
+                            <button type="submit" id="convertBtn" class="btn btn-secondary w-100 mt-3" disabled>
                                 <i class="fas fa-sync-alt me-2"></i>Convert
                             </button>
                         </form>
diff --git a/mappings/mapping_1760650861.php b/mappings/mapping_1760650861.php
new file mode 100644
index 0000000..ef35c9c
--- /dev/null
+++ b/mappings/mapping_1760650861.php
@@ -0,0 +1,108 @@
+<?php
+function convert_csv($inputFile, $outputFile) {
+    $strip_bom = function ($s) {
+        if ($s === null) return '';
+        if (strncmp($s, "\xEF\xBB\xBF", 3) === 0) {
+            return substr($s, 3);
+        }
+        return $s;
+    };
+
+    $in = @fopen($inputFile, 'r');
+    if ($in === false) {
+        return false;
+    }
+
+    // Read header
+    $header = fgetcsv($in, 0, ',', '"', '\\');
+    if ($header === false) {
+        fclose($in);
+        return false;
+    }
+
+    // Normalize header names and build index map
+    $index = [];
+    foreach ($header as $i => $name) {
+        $name = trim($strip_bom($name));
+        $index[$name] = $i;
+    }
+
+    $get = function ($row, $name) use ($index) {
+        if (!isset($index[$name])) return '';
+        $i = $index[$name];
+        return isset($row[$i]) ? trim($row[$i]) : '';
+    };
+
+    $out = @fopen($outputFile, 'w');
+    if ($out === false) {
+        fclose($in);
+        return false;
+    }
+
+    // Output header using semicolon separator
+    $outHeader = [
+        'Data księgowania',
+        'Nadawca / Odbiorca',
+        'Adres nadawcy / odbiorcy',
+        'Rachunek źródłowy',
+        'Rachunek docelowy',
+        'Tytuł',
+        'Kwota'
+    ];
+    fputcsv($out, $outHeader, ';');
+
+    while (($row = fgetcsv($in, 0, ',', '"', '\\')) !== false) {
+        // Skip completely empty rows
+        $nonEmpty = false;
+        foreach ($row as $v) {
+            if ($v !== null && $v !== '') { $nonEmpty = true; break; }
+        }
+        if (!$nonEmpty) continue;
+
+        $date = $get($row, 'Date completed (UTC)');
+        if ($date === '') {
+            $date = $get($row, 'Date started (UTC)');
+        }
+
+        $description = $get($row, 'Description');
+        $payer = $get($row, 'Payer');
+        $counterparty = $description !== '' ? $description : $payer;
+
+        $sourceAccount = $get($row, 'Account');
+
+        $benefIban = $get($row, 'Beneficiary IBAN');
+        $benefAccNo = $get($row, 'Beneficiary account number');
+        $destAccount = $benefIban !== '' ? $benefIban : $benefAccNo;
+
+        $reference = $get($row, 'Reference');
+        $type = $get($row, 'Type');
+        $title = $reference !== '' ? $reference : str_replace('_', ' ', $type);
+        if ($title === '' && $counterparty !== '') {
+            $title = $counterparty;
+        }
+
+        // Prefer Amount, then Total amount, then Orig amount
+        $amount = $get($row, 'Amount');
+        if ($amount === '') $amount = $get($row, 'Total amount');
+        if ($amount === '') $amount = $get($row, 'Orig amount');
+
+        // Normalize decimal separator just in case
+        $amount = str_replace(',', '.', $amount);
+
+        $outputRow = [
+            $date,
+            $counterparty,
+            '',
+            $sourceAccount,
+            $destAccount,
+            $title,
+            $amount
+        ];
+
+        fputcsv($out, $outputRow, ';');
+    }
+
+    fclose($in);
+    fclose($out);
+    return true;
+}
\ No newline at end of file
diff --git a/outputs/converted_1760650923.csv b/outputs/converted_1760650923.csv
new file mode 100644
index 0000000..8347ce6
--- /dev/null
+++ b/outputs/converted_1760650923.csv
@@ -0,0 +1,47 @@
+"Data księgowania";"Nadawca / Odbiorca";"Adres nadawcy / odbiorcy";"Rachunek źródłowy";"Rachunek docelowy";Tytuł;Kwota
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+2025-08-23;"Web Innovative Softwar";;"EUR Card EUR";;"CARD PAYMENT";-0.24
+2025-08-23;"Web Innovative Softwar";;"EUR Card EUR";;"CARD PAYMENT";-34.35
+2025-08-23;"Web Innovative Softwar";;"EUR Card EUR";;"CARD PAYMENT";-0.24
+2025-08-23;"Discord* 12xserverboos";;"EUR Card EUR";;"CARD PAYMENT";-44.54
+2025-08-22;"To Flatlogic Poland";;"EUR Main";PL51109025900000000161061759;"Przelew na wlasne konto";-50.00
+2025-08-22;Cloudflare;;"EUR Card EUR";;"CARD PAYMENT";-8.03
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+2025-08-14;"Main · EUR → Main · PLN";;"EUR Main";;"Transfer to Main to recover negative balance";-41.07
+2025-08-14;"Money added from MOGANADEN MOORGHEN";;"EUR Main";;"July 2025 software development";6468.75
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+2025-08-04;"Main · EUR → Card USD · USD";;"EUR Main";;EXCHANGE;-3460.84
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+2025-07-28;"To Flatlogic EU";;"EUR Main";;"Invoice FL EU #759";-400.00
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+2025-07-23;"Discord* 12xserverboos";;"EUR Card EUR";;"CARD PAYMENT";-44.27
+2025-07-21;"To Flatlogic Poland";;"EUR Main";PL51109025900000000161061759;"Przelew na wlasne konto";-450.00
+2025-07-20;Cloudflare;;"EUR Card EUR";;"CARD PAYMENT";-25.83
+2025-07-20;Calendly;;"EUR Card EUR";;"CARD PAYMENT";-42.36
+2025-07-18;"Main · EUR → Main · USD";;"EUR Main";;EXCHANGE;-972.24
+2025-07-18;"To Flatlogic Poland";;"EUR Main";PL51109025900000000161061759;"Przelew na wlasne konto";-250.00
+2025-07-17;"Openai *chatgpt Subscr";;"EUR Card EUR";;"CARD PAYMENT";-186.18
+2025-07-16;"To Card EUR";;"EUR Main";;TRANSFER;-500.00
+2025-07-16;"From Main";;"EUR Card EUR";;TRANSFER;500.00
+2025-07-16;"Veed.io Basic";;"EUR Card EUR";;"CARD PAYMENT";-44.00
+2025-07-14;"Main · EUR → Main · PLN";;"EUR Main";;"Transfer to Main to recover negative balance";-8.49
+2025-07-14;"Main · EUR → Main · USD";;"EUR Main";;EXCHANGE;-17.12
+2025-07-14;"Main · EUR → Main · USD";;"EUR Main";;EXCHANGE;-2121.00
+2025-07-14;"Main · EUR → Main · USD";;"EUR Main";;EXCHANGE;-1711.65
+2025-07-14;"Money added from MOGANADEN MOORGHEN";;"EUR Main";;TOPUP;1631.25