huggingface · ravediamond · Sep 15, 2026
diff --git a/CLAUDE.md b/CLAUDE.md
@@ -39,7 +39,7 @@ Run the Python tests with `pytest` (config in [pyproject.toml](pyproject.toml);
 - [teleoperate.py](lelab/teleoperate.py) — leader→follower teleoperation (wraps `lerobot.teleoperate`).
 - [calibrate.py](lelab/calibrate.py) — step-by-step web calibration with a `CalibrationManager` singleton and `_step_complete` threading.Event.
 - [train.py](lelab/train.py) — wraps the LeRobot training CLI as a subprocess (psutil for lifecycle, queue for log streaming).
-- [datasets.py](lelab/datasets.py) — dataset listing (local cache + Hub, merged under a `source` field) plus the episode-browsing handlers behind `/dataset-episodes`, `/dataset-episode`, `/dataset-frame`, `/dataset-thumbnails`, `/dataset-motion` and `/dataset-video`.
+- [datasets.py](lelab/datasets.py) — dataset listing (local cache + Hub, merged under a `source` field), merging local datasets into a new one (`/merge-datasets`, wraps `lerobot.datasets.dataset_tools.merge_datasets`) plus the episode-browsing handlers behind `/dataset-episodes`, `/dataset-episode`, `/dataset-frame`, `/dataset-thumbnails`, `/dataset-motion` and `/dataset-video`.
 - [episode_media.py](lelab/episode_media.py) — reads the LeRobot v3.0 on-disk layout (`meta/episodes/*.parquet` + `videos/`) and decodes frames with PyAV. Deliberately does **not** go through `LeRobotDataset`, so browsing a dataset never builds a robot config or imports torch. Several episodes share one mp4, so locating an episode resolves both the file and the `from_/to_timestamp` window inside it — which is why `/dataset-video` is addressed by chunk/file rather than by episode.
 - [dataset_repair.py](lelab/dataset_repair.py) — rebuilds `meta/episodes/` for a recording interrupted before `LeRobotDataset.finalize()` ran. Without an episode index LeRobot reads a local dataset as "not downloaded yet" and fetches it from the Hub, which 404s for a dataset that was never pushed. Call `repair_local_dataset(repo_id)` before opening a recorded dataset with `LeRobotDataset`.
 - [utils/config.py](lelab/utils/config.py) — shared paths and persistence: calibration JSON, saved ports, saved config selections. **Import shared constants from here, do not hardcode paths in feature modules.**

diff --git a/frontend/dist/assets/index-BX9JKcmw.js b/frontend/dist/assets/index-BX9JKcmw.js
diff --git a/frontend/dist/assets/index-CLxhDAmf.css b/frontend/dist/assets/index-CLxhDAmf.css
diff --git a/frontend/dist/assets/index-DJuBJMLM.css b/frontend/dist/assets/index-DJuBJMLM.css
diff --git a/frontend/dist/assets/index-DLgsIoRd.js b/frontend/dist/assets/index-DLgsIoRd.js
diff --git a/frontend/dist/index.html b/frontend/dist/index.html
@@ -10,8 +10,8 @@
     <meta property="og:title" content="LeLab" />
     <meta property="og:description" content="LeRobot but on your browser." />
     <meta property="og:type" content="website" />
-    <script type="module" crossorigin src="/assets/index-BX9JKcmw.js"></script>
-    <link rel="stylesheet" crossorigin href="/assets/index-DJuBJMLM.css">
+    <script type="module" crossorigin src="/assets/index-DLgsIoRd.js"></script>
+    <link rel="stylesheet" crossorigin href="/assets/index-CLxhDAmf.css">
   </head>
 
   <body>

diff --git a/frontend/src/components/dataset/MergeDatasetsDialog.tsx b/frontend/src/components/dataset/MergeDatasetsDialog.tsx
@@ -0,0 +1,174 @@
+import React, { useEffect, useState } from "react";
+import { GitMerge, Loader2 } from "lucide-react";
+import { Button } from "@/components/ui/button";
+import { Checkbox } from "@/components/ui/checkbox";
+import { Input } from "@/components/ui/input";
+import { Label } from "@/components/ui/label";
+import {
+  Dialog,
+  DialogContent,
+  DialogDescription,
+  DialogFooter,
+  DialogHeader,
+  DialogTitle,
+} from "@/components/ui/dialog";
+import { useApi } from "@/contexts/ApiContext";
+import { useToast } from "@/hooks/use-toast";
+import { mergeDatasets } from "@/lib/datasetApi";
+
+interface MergeDatasetsDialogProps {
+  open: boolean;
+  onOpenChange: (open: boolean) => void;
+  /** Local datasets available to pick from. */
+  datasets: { repo_id: string }[];
+  /** Pre-checked when the dialog opens (the dataset currently being browsed). */
+  initialRepoId?: string | null;
+  /** Called with the newly merged dataset's repo_id once it's on disk. */
+  onMerged: (outputRepoId: string) => void;
+}
+
+/**
+ * Merge several local datasets into one new local dataset.
+ *
+ * Wraps `lerobot.datasets.dataset_tools.merge_datasets` via `/merge-datasets`,
+ * which concatenates the selected datasets' videos and data files. The result
+ * is written to disk only — merging never touches the Hub.
+ */
+const MergeDatasetsDialog: React.FC<MergeDatasetsDialogProps> = ({
+  open,
+  onOpenChange,
+  datasets,
+  initialRepoId,
+  onMerged,
+}) => {
+  const { baseUrl, fetchWithHeaders } = useApi();
+  const { toast } = useToast();
+
+  const [selected, setSelected] = useState<Set<string>>(new Set());
+  const [outputName, setOutputName] = useState("");
+  const [submitting, setSubmitting] = useState(false);
+
+  useEffect(() => {
+    if (open) {
+      setSelected(new Set(initialRepoId ? [initialRepoId] : []));
+      setOutputName("");
+      setSubmitting(false);
+    }
+  }, [open, initialRepoId]);
+
+  const toggle = (repoId: string) => {
+    setSelected((prev) => {
+      const next = new Set(prev);
+      if (next.has(repoId)) next.delete(repoId);
+      else next.add(repoId);
+      return next;
+    });
+  };
+
+  const canSubmit = selected.size >= 2 && outputName.trim().length > 0 && !submitting;
+
+  const handleSubmit = async () => {
+    if (!canSubmit) return;
+    setSubmitting(true);
+    try {
+      const result = await mergeDatasets(
+        baseUrl,
+        fetchWithHeaders,
+        Array.from(selected),
+        outputName.trim(),
+      );
+      if (!result.success || !result.output_repo_id) {
+        toast({
+          title: "Merge failed",
+          description: result.message ?? "Could not merge the selected datasets.",
+          variant: "destructive",
+        });
+        return;
+      }
+      toast({
+        title: "Datasets merged",
+        description: `${selected.size} datasets merged into ${result.output_repo_id}.`,
+      });
+      onOpenChange(false);
+      onMerged(result.output_repo_id);
+    } catch (e) {
+      toast({
+        title: "Merge failed",
+        description: e instanceof Error ? e.message : "Could not merge the selected datasets.",
+        variant: "destructive",
+      });
+    } finally {
+      setSubmitting(false);
+    }
+  };
+
+  return (
+    <Dialog open={open} onOpenChange={onOpenChange}>
+      <DialogContent className="border-gray-800 bg-gray-950 text-white">
+        <DialogHeader>
+          <DialogTitle className="flex items-center gap-2">
+            <GitMerge className="h-4 w-4 text-orange-500" />
+            Merge datasets
+          </DialogTitle>
+          <DialogDescription className="text-gray-400">
+            Pick at least two local datasets. Their episodes are concatenated into a new
+            dataset — the originals are left untouched.
+          </DialogDescription>
+        </DialogHeader>
+
+        <div className="max-h-64 space-y-1.5 overflow-y-auto rounded-md border border-gray-800 p-2">
+          {datasets.length === 0 && (
+            <p className="p-2 text-xs text-gray-500">No local datasets available.</p>
+          )}
+          {datasets.map((d) => (
+            <label
+              key={d.repo_id}
+              className="flex cursor-pointer items-center gap-2 rounded px-2 py-1.5 text-sm hover:bg-gray-900"
+            >
+              <Checkbox
+                checked={selected.has(d.repo_id)}
+                onCheckedChange={() => toggle(d.repo_id)}
+              />
+              <span className="truncate">{d.repo_id}</span>
+            </label>
+          ))}
+        </div>
+
+        <div className="space-y-1.5">
+          <Label htmlFor="merge-output-name" className="text-xs text-gray-400">
+            New dataset name
+          </Label>
+          <Input
+            id="merge-output-name"
+            value={outputName}
+            onChange={(e) => setOutputName(e.target.value)}
+            placeholder="merged-dataset"
+            className="border-gray-800 bg-gray-900 text-sm text-white"
+          />
+        </div>
+
+        <DialogFooter>
+          <Button
+            variant="outline"
+            size="sm"
+            onClick={() => onOpenChange(false)}
+            className="border-gray-800 bg-gray-900 text-xs text-gray-300 hover:bg-gray-800"
+          >
+            Cancel
+          </Button>
+          <Button
+            size="sm"
+            onClick={handleSubmit}
+            disabled={!canSubmit}
+            className="gap-1.5 bg-orange-600 text-xs hover:bg-orange-700"
+          >
+            {submitting && <Loader2 className="h-3.5 w-3.5 animate-spin" />}
+            Merge {selected.size >= 2 ? `${selected.size} datasets` : ""}
+          </Button>
+        </DialogFooter>
+      </DialogContent>
+    </Dialog>
+  );
+};
+
+export default MergeDatasetsDialog;
diff --git a/frontend/src/lib/datasetApi.ts b/frontend/src/lib/datasetApi.ts
@@ -71,6 +71,26 @@ export interface ThumbnailsResponse {
   thumbnails: Thumbnail[];
 }
 
+export interface MergeDatasetsResponse {
+  success: boolean;
+  message?: string;
+  output_repo_id?: string;
+  num_episodes?: number;
+}
+
+export async function mergeDatasets(
+  baseUrl: string,
+  fetcher: Fetcher,
+  datasetRepoIds: string[],
+  outputRepoId: string,
+): Promise<MergeDatasetsResponse> {
+  return apiRequest<MergeDatasetsResponse>(baseUrl, fetcher, "/merge-datasets", {
+    method: "POST",
+    body: { dataset_repo_ids: datasetRepoIds, output_repo_id: outputRepoId },
+    action: "Merge datasets",
+  });
+}
+
 export async function listEpisodes(
   baseUrl: string,
   fetcher: Fetcher,

diff --git a/frontend/src/pages/EditDataset.tsx b/frontend/src/pages/EditDataset.tsx
@@ -1,6 +1,6 @@
-import React, { useEffect, useMemo } from "react";
+import React, { useEffect, useMemo, useState } from "react";
 import { useNavigate, useSearchParams } from "react-router-dom";
-import { AlertCircle, ArrowLeft, Database, Loader2, Upload } from "lucide-react";
+import { AlertCircle, ArrowLeft, Database, GitMerge, Loader2, Upload } from "lucide-react";
 import {
   Select,
   SelectContent,
@@ -11,6 +11,7 @@ import {
 import { Button } from "@/components/ui/button";
 import EpisodeList from "@/components/dataset/EpisodeList";
 import EpisodeViewer from "@/components/dataset/EpisodeViewer";
+import MergeDatasetsDialog from "@/components/dataset/MergeDatasetsDialog";
 import { useDatasets } from "@/hooks/useDatasets";
 import { useEpisodeDetail, useEpisodes } from "@/hooks/useEpisodes";
 import { formatDuration } from "@/lib/datasetApi";
@@ -33,13 +34,15 @@ const EditDataset = () => {
   const navigate = useNavigate();
   const [searchParams, setSearchParams] = useSearchParams();
 
-  const { datasets, loading: datasetsLoading } = useDatasets();
+  const { datasets, loading: datasetsLoading, refresh: refreshDatasets } = useDatasets();
   // A Hub-only dataset has no videos on disk to decode.
   const localDatasets = useMemo(
     () => datasets.filter((d) => d.source === "local" || d.source === "both"),
     [datasets],
   );
 
+  const [mergeDialogOpen, setMergeDialogOpen] = useState(false);
+
   const repoId = searchParams.get("dataset");
   const episodeParam = searchParams.get("episode");
   const episodeIndex = episodeParam === null ? null : Number(episodeParam);
@@ -113,6 +116,17 @@ const EditDataset = () => {
                 </SelectContent>
               </Select>
             </div>
+            {localDatasets.length >= 2 && (
+              <Button
+                variant="outline"
+                size="sm"
+                onClick={() => setMergeDialogOpen(true)}
+                className="h-9 gap-1.5 border-gray-800 bg-gray-950 text-xs text-gray-300 hover:bg-gray-900"
+              >
+                <GitMerge className="h-3.5 w-3.5" />
+                Merge
+              </Button>
+            )}
             {/* Picking a dataset now lands here rather than on /upload, so the
                 upload + delete flow hangs off the page you browse from. */}
             {repoId && (
@@ -138,6 +152,17 @@ const EditDataset = () => {
           </div>
         </div>
 
+        <MergeDatasetsDialog
+          open={mergeDialogOpen}
+          onOpenChange={setMergeDialogOpen}
+          datasets={localDatasets}
+          initialRepoId={repoId}
+          onMerged={(outputRepoId) => {
+            refreshDatasets();
+            setDataset(outputRepoId);
+          }}
+        />
+
         {!repoId && (
           <div className="rounded-lg border border-gray-800 bg-gray-950 p-10 text-center">
             <Database className="mx-auto mb-3 h-8 w-8 text-gray-700" />

diff --git a/lelab/datasets.py b/lelab/datasets.py
@@ -19,13 +19,20 @@
 from typing import Any
 
 from huggingface_hub.errors import HfHubHTTPError
+from pydantic import BaseModel
 
 from . import episode_media
+from .dataset_repair import DatasetRepairError, repair_local_dataset
 from .utils.hf_auth import cached_whoami, shared_hf_api
 
 logger = logging.getLogger(__name__)
 
 
+class MergeDatasetsRequest(BaseModel):
+    dataset_repo_ids: list[str]
+    output_repo_id: str
+
+
 def _lerobot_cache_root() -> Path:
     return episode_media.lerobot_cache_root()
 
@@ -173,6 +180,74 @@ def list_all_datasets() -> list[dict[str, Any]]:
     return out
 
 
+def _resolve_new_dataset_dir(repo_id: str) -> Path:
+    """Resolve `repo_id` to a not-yet-existing directory inside the cache root.
+
+    Same traversal guard as `handle_delete_dataset` (lelab/record.py): the
+    resolved target must stay strictly inside the cache root.
+    """
+    root = _lerobot_cache_root()
+    try:
+        target = (root / repo_id).resolve()
+    except (ValueError, OSError) as e:
+        raise ValueError(f"Invalid dataset name: {repo_id}") from e
+    if target == root or root not in target.parents:
+        raise ValueError(f"Invalid dataset name: {repo_id}")
+    return target
+
+
+def handle_merge_datasets(dataset_repo_ids: list[str], output_repo_id: str) -> dict[str, Any]:
+    """Merge several local datasets into one new local dataset.
+
+    Wraps lerobot's `dataset_tools.merge_datasets`, which concatenates the
+    source datasets' videos and data files under a new repo_id. Each source
+    dataset is loaded (repairing an unfinalized recording first) and the
+    result is written to disk; nothing is pushed to the Hub.
+    """
+    repo_ids = [r.strip() for r in dataset_repo_ids if r.strip()]
+    if len(repo_ids) < 2:
+        return {"success": False, "message": "Select at least two datasets to merge"}
+
+    output_repo_id = (output_repo_id or "").strip()
+    if not output_repo_id:
+        return {"success": False, "message": "Enter a name for the merged dataset"}
+
+    try:
+        output_dir = _resolve_new_dataset_dir(output_repo_id)
+    except ValueError as e:
+        return {"success": False, "message": str(e)}
+    if output_dir.exists():
+        return {"success": False, "message": f"{output_repo_id} already exists locally"}
+
+    from lerobot.datasets import LeRobotDataset
+    from lerobot.datasets.dataset_tools import merge_datasets as lerobot_merge_datasets
+
+    loaded = []
+    for repo_id in repo_ids:
+        try:
+            repair_local_dataset(repo_id)
+            loaded.append(LeRobotDataset(repo_id))
+        except DatasetRepairError as e:
+            return {"success": False, "message": f"Could not repair {repo_id}: {e}"}
+        except Exception as e:
+            logger.warning(f"Could not load {repo_id} for merge: {e}")
+            return {"success": False, "message": f"Could not load {repo_id}: {e}"}
+
+    try:
+        merged = lerobot_merge_datasets(loaded, output_repo_id=output_repo_id, output_dir=output_dir)
+    except Exception as e:
+        logger.error(f"Failed to merge {repo_ids} into {output_repo_id}: {e}")
+        return {"success": False, "message": f"Failed to merge datasets: {e}"}
+
+    logger.info(f"Merged {repo_ids} into {output_repo_id}")
+    return {
+        "success": True,
+        "message": f"Merged {len(loaded)} datasets into {output_repo_id}",
+        "output_repo_id": output_repo_id,
+        "num_episodes": merged.num_episodes,
+    }
+
+
 # ── episode browsing ────────────────────────────────────────────────────────
 #
 # Everything below reads a *local* dataset only. Browsing a Hub-only dataset