diff --git a/uiserver/webpack.config.js b/uiserver/webpack.config.js
index 133ed34..89214de 100644
--- a/uiserver/webpack.config.js
+++ b/uiserver/webpack.config.js
@@ -545,14 +545,21 @@ module.exports = {
             });
 
             // GET /api/devices
-            // Returns list of unique device/channel pairs
+            // Returns list of unique device/channel pairs (sensors + outputs)
             app.get('/api/devices', (req, res) => {
                 try {
                     if (!db) throw new Error('Database not connected');
-                    // Filter to only numeric channels which can be charted
-                    const stmt = db.prepare("SELECT DISTINCT device, channel FROM sensor_events WHERE data_type = 'number' ORDER BY device, channel");
-                    const rows = stmt.all();
-                    res.json(rows);
+                    // Get sensor channels
+                    const sensorStmt = db.prepare("SELECT DISTINCT device, channel FROM sensor_events WHERE data_type = 'number' ORDER BY device, channel");
+                    const sensorRows = sensorStmt.all();
+
+                    // Add output channels with 'output' as device
+                    const outputRows = OUTPUT_CHANNELS.map(ch => ({
+                        device: 'output',
+                        channel: ch.channel
+                    }));
+
+                    res.json([...sensorRows, ...outputRows]);
                 } catch (err) {
                     res.status(500).json({ error: err.message });
                 }
@@ -576,75 +583,108 @@ module.exports = {
                     const startTime = since || new Date(Date.now() - 24 * 60 * 60 * 1000).toISOString();
                     const endTime = until || new Date().toISOString();
 
-                    // 1. Fetch main data window
-                    let sql = 'SELECT * FROM sensor_events WHERE timestamp > ? AND timestamp <= ? ';
-                    const params = [startTime, endTime];
-
-                    const requestedChannels = []; // [{device, channel}]
+                    const requestedSensorChannels = []; // [{device, channel}]
+                    const requestedOutputChannels = [];  // [channel]
 
                     if (req.query.selection) {
                         const selections = req.query.selection.split(',');
-                        if (selections.length > 0) {
-                            const placeholders = [];
-                            selections.forEach(s => {
-                                const lastColonIndex = s.lastIndexOf(':');
-                                if (lastColonIndex !== -1) {
-                                    const d = s.substring(0, lastColonIndex);
-                                    const c = s.substring(lastColonIndex + 1);
-                                    placeholders.push('(device = ? AND channel = ?)');
-                                    params.push(d, c);
-                                    requestedChannels.push({ device: d, channel: c });
+                        selections.forEach(s => {
+                            const lastColonIndex = s.lastIndexOf(':');
+                            if (lastColonIndex !== -1) {
+                                const d = s.substring(0, lastColonIndex);
+                                const c = s.substring(lastColonIndex + 1);
+                                if (d === 'output') {
+                                    requestedOutputChannels.push(c);
+                                } else {
+                                    requestedSensorChannels.push({ device: d, channel: c });
                                 }
-                            });
-                            if (placeholders.length > 0) {
-                                sql += `AND (${placeholders.join(' OR ')}) `;
                             }
-                        }
+                        });
                     }
 
-                    sql += 'ORDER BY timestamp ASC';
-
-                    const stmt = db.prepare(sql);
-                    const rows = stmt.all(...params);
-
-                    // 2. Backfill: Ensure we have a starting point for each channel
-                    // For each requested channel, check if we have data at/near start. 
-                    // If the first point for a channel is > startTime, we should try to find the previous value.
-                    // We check for the value that started before (or at) startTime AND ended after (or at) startTime (or hasn't ended).
-
-                    const backfillRows = [];
-                    // Find the record that started most recently before startTime BUT was still valid at startTime
-                    const backfillStmt = db.prepare(`
-                        SELECT * FROM sensor_events 
-                        WHERE device = ? AND channel = ? 
-                        AND timestamp <= ? 
-                        AND (until >= ? OR until IS NULL)
-                        ORDER BY timestamp DESC LIMIT 1
-                    `);
-
-                    requestedChannels.forEach(ch => {
-                        const prev = backfillStmt.get(ch.device, ch.channel, startTime, startTime);
-                        if (prev) {
-                            // We found a point that covers the startTime.
-                            backfillRows.push(prev);
-                        }
-                    });
-
-                    // Combine and sort
-                    const allRows = [...backfillRows, ...rows];
-
-                    // Transform to Compact Dictionary Format
-                    // { "device:channel": [ [timestamp, value, until], ... ] }
                     const result = {};
 
-                    allRows.forEach(row => {
-                        const key = `${row.device}:${row.channel}`;
-                        if (!result[key]) result[key] = [];
+                    // 1. Fetch sensor data
+                    if (requestedSensorChannels.length > 0) {
+                        let sql = 'SELECT * FROM sensor_events WHERE timestamp > ? AND timestamp <= ? ';
+                        const params = [startTime, endTime];
 
-                        const pt = [row.timestamp, row.value];
-                        if (row.until) pt.push(row.until);
-                        result[key].push(pt);
-                    });
+                        const placeholders = [];
+                        requestedSensorChannels.forEach(ch => {
+                            placeholders.push('(device = ? AND channel = ?)');
+                            params.push(ch.device, ch.channel);
+                        });
+                        if (placeholders.length > 0) {
+                            sql += `AND (${placeholders.join(' OR ')}) `;
+                        }
+                        sql += 'ORDER BY timestamp ASC';
+
+                        const rows = db.prepare(sql).all(...params);
+
+                        // Backfill for sensors
+                        const backfillStmt = db.prepare(`
+                            SELECT * FROM sensor_events 
+                            WHERE device = ? AND channel = ? 
+                            AND timestamp <= ? 
+                            AND (until >= ? OR until IS NULL)
+                            ORDER BY timestamp DESC LIMIT 1
+                        `);
+
+                        const backfillRows = [];
+                        requestedSensorChannels.forEach(ch => {
+                            const prev = backfillStmt.get(ch.device, ch.channel, startTime, startTime);
+                            if (prev) backfillRows.push(prev);
+                        });
+
+                        [...backfillRows, ...rows].forEach(row => {
+                            const key = `${row.device}:${row.channel}`;
+                            if (!result[key]) result[key] = [];
+                            const pt = [row.timestamp, row.value];
+                            if (row.until) pt.push(row.until);
+                            result[key].push(pt);
+                        });
+                    }
+
+                    // 2. Fetch output data
+                    if (requestedOutputChannels.length > 0) {
+                        let sql = 'SELECT * FROM output_events WHERE timestamp > ? AND timestamp <= ? ';
+                        const params = [startTime, endTime];
+
+                        const placeholders = requestedOutputChannels.map(() => 'channel = ?');
+                        sql += `AND (${placeholders.join(' OR ')}) `;
+                        params.push(...requestedOutputChannels);
+                        sql += 'ORDER BY timestamp ASC';
+
+                        const rows = db.prepare(sql).all(...params);
+
+                        // Backfill for outputs
+                        const backfillStmt = db.prepare(`
+                            SELECT * FROM output_events 
+                            WHERE channel = ? 
+                            AND timestamp <= ? 
+                            AND (until >= ? OR until IS NULL)
+                            ORDER BY timestamp DESC LIMIT 1
+                        `);
+
+                        const backfillRows = [];
+                        requestedOutputChannels.forEach(ch => {
+                            const prev = backfillStmt.get(ch, startTime, startTime);
+                            if (prev) {
+                                backfillRows.push(prev);
+                            } else {
+                                // No data at all - add default 0 value at startTime
+                                backfillRows.push({ channel: ch, timestamp: startTime, value: 0, until: null });
+                            }
+                        });
+
+                        [...backfillRows, ...rows].forEach(row => {
+                            const key = `output:${row.channel}`;
+                            if (!result[key]) result[key] = [];
+                            const pt = [row.timestamp, row.value];
+                            if (row.until) pt.push(row.until);
+                            result[key].push(pt);
+                        });
+                    }
 
                     res.json(result);
                 } catch (err) {