diff --git a/server/src/services/discordBotService.js b/server/src/services/discordBotService.js
index 94955a15..ce26ec56 100644
--- a/server/src/services/discordBotService.js
+++ b/server/src/services/discordBotService.js
@@ -298,13 +298,60 @@ async function buildReplayVideo({ cameraId = null } = {}) {
   }
   const tmpDir = await fsp.mkdtemp(path.join(os.tmpdir(), 'rover-replay-'));
   try {
+    const firstFrameByCamera = new Map();
     for (let i = 0; i < frames.length; i += 1) {
       const filename = `frame-${String(i + 1).padStart(4, '0')}.jpg`;
       await fsp.writeFile(path.join(tmpDir, filename), frames[i].buffer);
+      const cameraId = frames[i].camera?.id;
+      if (cameraId && !firstFrameByCamera.has(cameraId)) {
+        firstFrameByCamera.set(cameraId, filename);
+      }
     }
     const outPath = path.join(tmpDir, 'replay.mp4');
     const delayMs = getRoomCameraReplayDelayMs();
-    const fps = (1000 / delayMs).toFixed(3);
+    const fpsValue = 1000 / delayMs;
+    const fps = fpsValue.toFixed(3);
+    let maxWidth = 0;
+    let maxHeight = 0;
+    for (const filename of firstFrameByCamera.values()) {
+      try {
+        const { stdout } = await execFileAsync('ffprobe', [
+          '-v',
+          'error',
+          '-select_streams',
+          'v:0',
+          '-show_entries',
+          'stream=width,height',
+          '-of',
+          'csv=p=0',
+          path.join(tmpDir, filename),
+        ]);
+        const [widthRaw, heightRaw] = stdout.trim().split(',');
+        const width = Number(widthRaw);
+        const height = Number(heightRaw);
+        if (Number.isFinite(width) && Number.isFinite(height)) {
+          maxWidth = Math.max(maxWidth, width);
+          maxHeight = Math.max(maxHeight, height);
+        }
+      } catch (err) {
+        logger.warn('Failed to probe replay frame size', err.message);
+      }
+    }
+    const MAX_REPLAY_WIDTH = 1280;
+    const MAX_REPLAY_HEIGHT = 720;
+    let targetWidth = maxWidth || MAX_REPLAY_WIDTH;
+    let targetHeight = maxHeight || MAX_REPLAY_HEIGHT;
+    if (targetWidth > MAX_REPLAY_WIDTH || targetHeight > MAX_REPLAY_HEIGHT) {
+      const scale = Math.min(MAX_REPLAY_WIDTH / targetWidth, MAX_REPLAY_HEIGHT / targetHeight);
+      targetWidth = Math.max(2, Math.floor((targetWidth * scale) / 2) * 2);
+      targetHeight = Math.max(2, Math.floor((targetHeight * scale) / 2) * 2);
+    }
+    const sizeFilter = `scale=${targetWidth}:${targetHeight}:force_original_aspect_ratio=decrease:flags=lanczos,pad=${targetWidth}:${targetHeight}:(ow-iw)/2:(oh-ih)/2:color=black,setsar=1`;
+    const maxBytes = Math.floor(9.5 * 1024 * 1024);
+    const durationSec = Math.max(1, frames.length / fpsValue);
+    const targetBitrateKbps = Math.max(300, Math.floor((maxBytes * 8) / durationSec / 1000));
+    const maxrateKbps = Math.floor(targetBitrateKbps * 1.1);
+    const bufsizeKbps = Math.floor(targetBitrateKbps * 2);
     await execFileAsync('ffmpeg', [
       '-y',
       '-hide_banner',
@@ -314,8 +361,16 @@ async function buildReplayVideo({ cameraId = null } = {}) {
       fps,
       '-i',
       'frame-%04d.jpg',
+      '-vf',
+      sizeFilter,
       '-c:v',
       'libx264',
+      '-b:v',
+      `${targetBitrateKbps}k`,
+      '-maxrate',
+      `${maxrateKbps}k`,
+      '-bufsize',
+      `${bufsizeKbps}k`,
       '-pix_fmt',
       'yuv420p',
       outPath,