diff --git a/docs/plans/2026-08-18-implement-leaflet-frontend.md b/docs/plans/2026-08-18-implement-leaflet-frontend.md
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+# Implement Leaflet + OpenStreetMap Frontend
+
+## Overview
+- Add a complete frontend web interface using Leaflet + OpenStreetMap tiles for route visualization
+- Provide a search form for route parameters (from city, to city, date)
+- Display found routes in a list with duration, transfers, and cost
+- Render route geometry as GeoJSON on an interactive map
+- Real segments displayed as solid lines with color by transport type
+- Synthetic segments displayed as dashed lines
+- Transfer points displayed as markers with popup information
+
+## Context
+- Files/components involved:
+  - `static/index.html` - main HTML page with Leaflet + OSM integration
+  - `static/styles.css` - CSS styling for the frontend
+  - `static/app.js` - JavaScript for search form, API calls, and map rendering
+  - `cmd/api/main.go` - update to serve static files and the frontend
+- Related patterns found:
+  - GeoJSON FeatureCollection response from `/v1/routes/{search_id}/{route_id}/geojson`
+  - LineString features with properties: `transport`, `transport_type`, `kind`, `synthetic`, `duration`, `cost`, `is_transfer`, `stroke_color`, `stroke_width`, `stroke_dasharray`
+  - Point features for transfer markers with properties: `marker_type`, `title`, `connection_time`, `connection_time_formatted`, `transfer_type`, `is_transfer`, `stroke_color`, `stroke_width`
+- Dependencies identified:
+  - Leaflet 1.9.4 (CSS and JS from CDN)
+  - OpenStreetMap tiles
+
+## Development Approach
+- **Testing approach**: Regular (code first, then verify)
+- Complete each task fully before moving to the next
+- Make small, focused changes
+- **CRITICAL: ensure all frontend files are properly linked and functional**
+- Maintain backward compatibility with existing API endpoints
+
+## Testing Strategy
+- **Manual testing**: Test search form, route list, map rendering, and popup interactions
+- **UI/UX testing**: Verify responsive layout, loading states, error handling
+
+## Progress Tracking
+- Mark completed items with `[x]` immediately when done
+- Add newly discovered tasks with ➕ prefix
+- Document issues/blockers with ⚠️ prefix
+- Update plan if implementation deviates from original scope
+- Keep plan in sync with actual work done
+
+## What Goes Where
+- **Implementation Steps** (`[ ]` checkboxes): tasks achievable within this codebase - frontend files, Go server updates
+- **Post-Completion** (no checkboxes): items requiring external action - manual testing in browser
+
+## Implementation Steps
+
+### Task 1: Create static directory and HTML structure
+- [x] create `static/` directory
+- [x] create `static/index.html` with Leaflet + OSM integration and search form
+- [x] create `static/styles.css` with styling for layout, routes list, and map
+- [x] create `static/app.js` with API calls and map rendering logic
+
+### Task 2: Update Go server to serve static files
+- [ ] update `cmd/api/main.go` to serve static files from `static/` directory
+- [ ] add route for `/static/*` to serve CSS, JS, and other assets
+- [ ] add route for `/` or `/index.html` to serve the frontend
+
+### Task 3: Verify frontend functionality
+- [ ] verify search form works and calls `/v1/routes/search` endpoint
+- [ ] verify routes list displays correctly with duration, transfers, cost
+- [ ] verify map renders with Leaflet + OpenStreetMap tiles
+- [ ] verify GeoJSON is fetched and rendered on the map
+- [ ] verify transfer markers have popups with connection info
+
+## Technical Details
+- Leaflet CSS: `https://unpkg.com/leaflet@1.9.4/dist/leaflet.css`
+- Leaflet JS: `https://unpkg.com/leaflet@1.9.4/dist/leaflet.js`
+- OpenStreetMap tiles: `https://{s}.tile.openstreetmap.org/{z}/{x}/{y}.png`
+- GeoJSON rendering: use `L.geoJSON()` with custom style functions for real vs synthetic edges
+- Transport colors: plane = `#ff9800` (orange), train = `#1976d2` (blue), bus = `#cddc39` (lime)
+
+## Post-Completion
+*Items requiring manual intervention or external systems - no checkboxes, informational only*
+
+**Manual verification**:
+- Test search form in browser
+- Verify map renders correctly with routes
+- Test popup interactions for transfer points
+- Verify responsive layout on different screen sizes
diff --git a/static/app.js b/static/app.js
new file mode 100644
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--- /dev/null
+++ b/static/app.js
@@ -0,0 +1,294 @@
+// Initialize map
+const map = L.map('map').setView([55.7558, 37.6173], 5);
+
+// Add OpenStreetMap tiles
+L.tileLayer('https://{s}.tile.openstreetmap.org/{z}/{x}/{y}.png', {
+    attribution: '&copy; <a href="https://www.openstreetmap.org/copyright">OpenStreetMap</a> contributors',
+    maxZoom: 18
+}).addTo(map);
+
+// Layers to store map features
+let routeLayers = L.layerGroup().addTo(map);
+let transferMarkers = L.layerGroup().addTo(map);
+
+// Transport colors
+const transportColors = {
+    'plane': '#ff9800',
+    'train': '#1976d2',
+    'bus': '#cddc39',
+    'other': '#9e9e9e'
+};
+
+// Get transport color
+function getTransportColor(feature) {
+    const transportType = feature.properties.transport_type || feature.properties.transport || 'other';
+    return transportColors[transportType] || transportColors.other;
+}
+
+// Get line style based on feature properties
+function getLineStyle(feature) {
+    if (feature.properties && feature.properties.synthetic === 'true') {
+        return {
+            color: getTransportColor(feature),
+            weight: 2,
+            dashArray: '5, 5',
+            opacity: 0.7
+        };
+    }
+
+    return {
+        color: getTransportColor(feature),
+        weight: 3,
+        opacity: 0.8
+    };
+}
+
+// Get marker style based on feature properties
+function getMarkerStyle(feature) {
+    const color = feature.properties.stroke_color || getTransportColor(feature);
+    const width = feature.properties.stroke_width || 3;
+
+    return {
+        color: color,
+        weight: width,
+        fillColor: '#fff',
+        fillOpacity: 1
+    };
+}
+
+// Format duration from seconds to readable format
+function formatDuration(seconds) {
+    if (!seconds || seconds === 0) return '0h';
+
+    const hours = Math.floor(seconds / 3600);
+    const minutes = Math.floor((seconds % 3600) / 60);
+
+    if (hours > 0) {
+        return `${hours}h ${minutes}m`;
+    }
+    return `${minutes}m`;
+}
+
+// Format connection time
+function formatConnectionTime(connectionTime) {
+    if (!connectionTime) return 'N/A';
+    return formatDuration(connectionTime);
+}
+
+// Render GeoJSON on map
+function renderGeoJSON(geojsonData) {
+    // Clear existing layers
+    routeLayers.clearLayers();
+    transferMarkers.clearLayers();
+
+    if (!geojsonData || !geojsonData.features) {
+        return;
+    }
+
+    // Process features
+    geojsonData.features.forEach(feature => {
+        const kind = feature.properties?.kind || feature.type;
+
+        if (kind === 'LineString' || feature.geometry?.type === 'LineString') {
+            // LineString feature - route segment
+            const style = getLineStyle(feature);
+
+            L.geoJSON(feature, {
+                style: function(feature) {
+                    return getLineStyle(feature);
+                },
+                onEachFeature: function(feature, layer) {
+                    layer.addTo(routeLayers);
+                }
+            }).addTo(routeLayers);
+        } else if (kind === 'Point' || feature.geometry?.type === 'Point') {
+            // Point feature - transfer marker
+            const markerType = feature.properties?.marker_type;
+
+            if (markerType === 'transfer' || feature.properties?.is_transfer === 'true') {
+                const style = getMarkerStyle(feature);
+
+                const marker = L.circleMarker([feature.geometry.coordinates[1], feature.geometry.coordinates[0]], {
+                    color: style.color,
+                    weight: style.weight,
+                    fillColor: style.fillColor,
+                    fillOpacity: style.fillOpacity,
+                    radius: 6
+                });
+
+                // Create popup content
+                let popupContent = `<h4>${feature.properties?.title || 'Transfer'}</h4>`;
+
+                if (feature.properties?.connection_time_formatted) {
+                    popupContent += `<p>Connection time: ${feature.properties.connection_time_formatted}</p>`;
+                } else if (feature.properties?.connection_time) {
+                    popupContent += `<p>Connection time: ${formatConnectionTime(feature.properties.connection_time)}</p>`;
+                }
+
+                if (feature.properties?.transfer_type) {
+                    popupContent += `<p>Transfer type: ${feature.properties.transfer_type}</p>`;
+                }
+
+                marker.bindPopup(popupContent);
+                marker.addTo(transferMarkers);
+            }
+        }
+    });
+
+    // Fit map to bounds if there are features
+    if (routeLayers.getLayers().length > 0 || transferMarkers.getLayers().length > 0) {
+        const group = new L.featureGroup([...routeLayers.getLayers(), ...transferMarkers.getLayers()]);
+        map.fitBounds(group.getBounds().pad(0.1));
+    }
+}
+
+// Show loading overlay
+function showLoading() {
+    document.getElementById('loading-overlay').classList.remove('hidden');
+}
+
+// Hide loading overlay
+function hideLoading() {
+    document.getElementById('loading-overlay').classList.add('hidden');
+}
+
+// Show error message
+function showError(message) {
+    const errorEl = document.getElementById('error-message');
+    errorEl.textContent = message;
+    errorEl.classList.remove('hidden');
+
+    setTimeout(() => {
+        errorEl.classList.add('hidden');
+    }, 5000);
+}
+
+// Hide error message
+function hideError() {
+    document.getElementById('error-message').classList.add('hidden');
+}
+
+// Render routes list
+function renderRoutesList(routes) {
+    const routesListEl = document.getElementById('routes-list');
+
+    if (!routes || routes.length === 0) {
+        routesListEl.innerHTML = '<p class="empty-message">No routes found</p>';
+        return;
+    }
+
+    let html = '';
+    routes.forEach((route, index) => {
+        const duration = formatDuration(route.duration_seconds || route.duration || 0);
+        const transfers = route.transfers || route.transfer_count || 0;
+        const cost = route.cost || 0;
+
+        html += `
+            <div class="route-card" data-route-id="${route.id}" data-search-id="${route.search_id}">
+                <div class="route-card-header">
+                    <span class="route-duration">${duration}</span>
+                    <span class="route-cost">${cost > 0 ? cost + ' units' : 'N/A'}</span>
+                </div>
+                <div class="route-details">
+                    <span class="route-transfers">${transfers} transfer${transfers !== 1 ? 's' : ''}</span>
+                </div>
+            </div>
+        `;
+    });
+
+    routesListEl.innerHTML = html;
+
+    // Add click handlers to route cards
+    document.querySelectorAll('.route-card').forEach(card => {
+        card.addEventListener('click', function() {
+            // Remove selected class from all cards
+            document.querySelectorAll('.route-card').forEach(c => c.classList.remove('selected'));
+            this.classList.add('selected');
+
+            // Fetch and render GeoJSON for this route
+            const searchId = this.dataset.searchId;
+            const routeId = this.dataset.routeId;
+            fetchGeoJSON(searchId, routeId);
+        });
+    });
+}
+
+// Fetch GeoJSON for a route
+async function fetchGeoJSON(searchId, routeId) {
+    try {
+        const response = await fetch(`/v1/routes/${searchId}/${routeId}/geojson`);
+        if (!response.ok) {
+            throw new Error(`Failed to fetch GeoJSON: ${response.statusText}`);
+        }
+
+        const geojsonData = await response.json();
+        renderGeoJSON(geojsonData);
+    } catch (error) {
+        console.error('Error fetching GeoJSON:', error);
+        showError('Failed to load route map');
+    }
+}
+
+// Search for routes
+async function searchRoutes(formData) {
+    showLoading();
+    hideError();
+
+    try {
+        const response = await fetch('/v1/routes/search', {
+            method: 'POST',
+            headers: {
+                'Content-Type': 'application/json'
+            },
+            body: JSON.stringify({
+                from: formData.get('from'),
+                to: formData.get('to'),
+                date: formData.get('date')
+            })
+        });
+
+        if (!response.ok) {
+            throw new Error(`Search failed: ${response.statusText}`);
+        }
+
+        const searchData = await response.json();
+
+        // Render routes list
+        if (searchData.routes) {
+            renderRoutesList(searchData.routes);
+        } else if (searchData.routes === null || searchData.routes === undefined) {
+            document.getElementById('routes-list').innerHTML = '<p class="empty-message">No routes found</p>';
+        }
+
+        // If there's only one route, select it automatically
+        const routes = searchData.routes || [];
+        if (routes.length === 1) {
+            const firstCard = document.querySelector('.route-card');
+            if (firstCard) {
+                firstCard.classList.add('selected');
+                fetchGeoJSON(routes[0].search_id, routes[0].id);
+            }
+        }
+
+    } catch (error) {
+        console.error('Error searching routes:', error);
+        showError('Failed to search routes. Please try again.');
+        document.getElementById('routes-list').innerHTML = '<p class="empty-message">Search failed</p>';
+    } finally {
+        hideLoading();
+    }
+}
+
+// Initialize search form
+document.getElementById('search-form').addEventListener('submit', function(e) {
+    e.preventDefault();
+
+    const formData = new FormData(this);
+    searchRoutes(formData);
+});
+
+// Set default date to today
+const dateInput = document.getElementById('travel-date');
+const today = new Date().toISOString().split('T')[0];
+dateInput.value = today;
+dateInput.min = today;
diff --git a/static/index.html b/static/index.html
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--- /dev/null
+++ b/static/index.html
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+<!DOCTYPE html>
+<html lang="en">
+<head>
+    <meta charset="UTF-8">
+    <meta name="viewport" content="width=device-width, initial-scale=1.0">
+    <title>Trip Planner</title>
+    <link rel="stylesheet" href="https://unpkg.com/leaflet@1.9.4/dist/leaflet.css" />
+    <link rel="stylesheet" href="/static/styles.css">
+</head>
+<body>
+    <div class="app-container">
+        <header class="header">
+            <h1>Trip Planner</h1>
+        </header>
+
+        <div class="search-container">
+            <form id="search-form" class="search-form">
+                <div class="form-group">
+                    <label for="from-city">From</label>
+                    <input type="text" id="from-city" name="from" placeholder="Enter departure city" required>
+                </div>
+                <div class="form-group">
+                    <label for="to-city">To</label>
+                    <input type="text" id="to-city" name="to" placeholder="Enter destination city" required>
+                </div>
+                <div class="form-group">
+                    <label for="travel-date">Date</label>
+                    <input type="date" id="travel-date" name="date" required>
+                </div>
+                <button type="submit" id="search-btn" class="search-btn">Search Routes</button>
+            </form>
+        </div>
+
+        <div class="content-container">
+            <div class="routes-panel">
+                <h2>Found Routes</h2>
+                <div id="routes-list" class="routes-list">
+                    <p class="empty-message">Search for routes to see results here</p>
+                </div>
+            </div>
+
+            <div class="map-panel">
+                <div id="map" class="map"></div>
+            </div>
+        </div>
+
+        <div id="loading-overlay" class="loading-overlay hidden">
+            <div class="loading-spinner"></div>
+            <p>Searching for routes...</p>
+        </div>
+
+        <div id="error-message" class="error-message hidden"></div>
+    </div>
+
+    <script src="https://unpkg.com/leaflet@1.9.4/dist/leaflet.js"></script>
+    <script src="/static/app.js"></script>
+</body>
+</html>
diff --git a/static/styles.css b/static/styles.css
new file mode 100644
index 0000000..5eacecb
--- /dev/null
+++ b/static/styles.css
@@ -0,0 +1,292 @@
+* {
+    margin: 0;
+    padding: 0;
+    box-sizing: border-box;
+}
+
+body {
+    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, Cantarell, sans-serif;
+    background-color: #f5f5f5;
+    color: #333;
+    height: 100vh;
+    overflow: hidden;
+}
+
+.app-container {
+    display: flex;
+    flex-direction: column;
+    height: 100vh;
+}
+
+.header {
+    background-color: #2c3e50;
+    color: white;
+    padding: 1rem 2rem;
+    box-shadow: 0 2px 4px rgba(0, 0, 0, 0.1);
+}
+
+.header h1 {
+    font-size: 1.5rem;
+    font-weight: 600;
+}
+
+.search-container {
+    background-color: #fff;
+    padding: 1rem 2rem;
+    box-shadow: 0 1px 3px rgba(0, 0, 0, 0.1);
+}
+
+.search-form {
+    display: flex;
+    gap: 1rem;
+    align-items: flex-end;
+    flex-wrap: wrap;
+}
+
+.form-group {
+    display: flex;
+    flex-direction: column;
+    gap: 0.5rem;
+}
+
+.form-group label {
+    font-size: 0.875rem;
+    font-weight: 500;
+    color: #555;
+}
+
+.form-group input {
+    padding: 0.5rem 0.75rem;
+    border: 1px solid #ddd;
+    border-radius: 4px;
+    font-size: 1rem;
+    min-width: 150px;
+}
+
+.form-group input:focus {
+    outline: none;
+    border-color: #1976d2;
+    box-shadow: 0 0 0 2px rgba(25, 118, 210, 0.1);
+}
+
+.search-btn {
+    padding: 0.5rem 1.5rem;
+    background-color: #1976d2;
+    color: white;
+    border: none;
+    border-radius: 4px;
+    font-size: 1rem;
+    font-weight: 500;
+    cursor: pointer;
+    transition: background-color 0.2s;
+}
+
+.search-btn:hover {
+    background-color: #1565c0;
+}
+
+.search-btn:disabled {
+    background-color: #90caf9;
+    cursor: not-allowed;
+}
+
+.content-container {
+    display: flex;
+    flex: 1;
+    overflow: hidden;
+}
+
+.routes-panel {
+    width: 350px;
+    background-color: #fff;
+    border-right: 1px solid #ddd;
+    display: flex;
+    flex-direction: column;
+    overflow: hidden;
+}
+
+.routes-panel h2 {
+    padding: 1rem;
+    font-size: 1.125rem;
+    font-weight: 600;
+    border-bottom: 1px solid #eee;
+    background-color: #f9f9f9;
+}
+
+.routes-list {
+    flex: 1;
+    overflow-y: auto;
+    padding: 0.5rem;
+}
+
+.empty-message {
+    padding: 2rem;
+    text-align: center;
+    color: #888;
+}
+
+.route-card {
+    background-color: #fff;
+    border: 1px solid #ddd;
+    border-radius: 6px;
+    padding: 1rem;
+    margin-bottom: 0.5rem;
+    cursor: pointer;
+    transition: box-shadow 0.2s, border-color 0.2s;
+}
+
+.route-card:hover {
+    box-shadow: 0 2px 8px rgba(0, 0, 0, 0.1);
+    border-color: #1976d2;
+}
+
+.route-card.selected {
+    border-color: #1976d2;
+    background-color: #e3f2fd;
+}
+
+.route-card-header {
+    display: flex;
+    justify-content: space-between;
+    align-items: center;
+    margin-bottom: 0.5rem;
+}
+
+.route-duration {
+    font-weight: 600;
+    color: #2c3e50;
+}
+
+.route-transfers {
+    font-size: 0.875rem;
+    color: #666;
+}
+
+.route-cost {
+    font-weight: 600;
+    color: #27ae60;
+}
+
+.map-panel {
+    flex: 1;
+    position: relative;
+}
+
+#map {
+    width: 100%;
+    height: 100%;
+}
+
+.loading-overlay {
+    position: fixed;
+    top: 0;
+    left: 0;
+    right: 0;
+    bottom: 0;
+    background-color: rgba(0, 0, 0, 0.5);
+    display: flex;
+    flex-direction: column;
+    justify-content: center;
+    align-items: center;
+    z-index: 1000;
+}
+
+.loading-overlay.hidden {
+    display: none;
+}
+
+.loading-spinner {
+    border: 4px solid #f3f3f3;
+    border-top: 4px solid #1976d2;
+    border-radius: 50%;
+    width: 40px;
+    height: 40px;
+    animation: spin 1s linear infinite;
+    margin-bottom: 1rem;
+}
+
+@keyframes spin {
+    0% { transform: rotate(0deg); }
+    100% { transform: rotate(360deg); }
+}
+
+.loading-overlay p {
+    color: white;
+    font-size: 1rem;
+}
+
+.error-message {
+    position: fixed;
+    top: 1rem;
+    right: 1rem;
+    background-color: #e74c3c;
+    color: white;
+    padding: 1rem;
+    border-radius: 6px;
+    box-shadow: 0 2px 8px rgba(0, 0, 0, 0.2);
+    z-index: 1001;
+    max-width: 400px;
+}
+
+.error-message.hidden {
+    display: none;
+}
+
+/* Leaflet popup styling */
+.leaflet-popup-content {
+    min-width: 200px;
+}
+
+.leaflet-popup-content h4 {
+    margin-bottom: 0.5rem;
+    color: #2c3e50;
+}
+
+.leaflet-popup-content p {
+    margin: 0.25rem 0;
+    font-size: 0.875rem;
+}
+
+/* Transport type colors */
+.transport-plane {
+    color: #ff9800;
+}
+
+.transport-train {
+    color: #1976d2;
+}
+
+.transport-bus {
+    color: #cddc39;
+}
+
+/* Responsive layout */
+@media (max-width: 768px) {
+    .content-container {
+        flex-direction: column;
+    }
+
+    .routes-panel {
+        width: 100%;
+        height: 40%;
+        border-right: none;
+        border-bottom: 1px solid #ddd;
+    }
+
+    .map-panel {
+        height: 60%;
+    }
+
+    .search-form {
+        flex-direction: column;
+        align-items: stretch;
+    }
+
+    .form-group {
+        width: 100%;
+    }
+
+    .form-group input {
+        width: 100%;
+    }
+}