diff --git a/README.md b/README.md
index 06a499d..6150568 100644
--- a/README.md
+++ b/README.md
@@ -18,7 +18,7 @@ nodes:
   - id: camera
     git: ssh://git@gitea.liria.cl:5001/liria/dora-webcam.git
     tag: v0.1.0
-    build: pip install .
+    build: uv pip install .
     path: dora-webcam
     inputs:
       tick: dora/timer/millis/33
@@ -26,24 +26,30 @@ nodes:
       - image
 ```
 
-Run the dataflow with `--uv` (`dora run dataflow.yml --uv`) so the node gets its own
-managed environment.
+Run the dataflow with `--uv` (`dora run dataflow.yml --uv`): the build command is
+`uv pip install .`, so the node gets its own managed environment and never installs into
+an ambient one.
 
-### Runnable dataflows
+### Runnable dataflow
 
-Two dataflows live here, run one at a time — dora has no cross-dataflow wiring, so each
-declares the camera itself:
+[`dataflow.yml`](dataflow.yml) is the camera on its own, and is what CI runs:
 
-Run either with `dora run <file> --uv`:
+```bash
+dora run dataflow.yml --uv
+```
 
-| File | Contents |
-|---|---|
-| [`dataflow.yml`](dataflow.yml) | The camera alone |
-| [`dataflow_view.yml`](dataflow_view.yml) | The camera into `dora-image-view` |
+Nothing consumes the frames, so to actually see them set `PREVIEW`:
 
-`dataflow_view.yml` is the end-to-end check of the pair: it wires this node's `image`
-output into the viewer's `image` input, so a window opens showing the webcam. It fetches
-the viewer over the network, which is why CI validates and runs `dataflow.yml` only.
+```bash
+PREVIEW=true dora run dataflow.yml --uv
+```
+
+A window opens showing the frames as they are published. Press `q` to stop. That is
+enough to check a camera, an encoding or a flip without wiring a second node — which is
+why there is one dataflow here rather than one per consumer.
+
+For a real pipeline, wire `image` into a viewer such as `dora-image-view` from your own
+dataflow.
 
 ## Output
 
@@ -73,6 +79,7 @@ compressed encoding, `width` and `height` are the image's dimensions, not the le
 | `ENCODING` | `bgr8` | One of `bgr8`, `rgb8`, `yuv420`, `jpeg`/`jpg`/`jpe`, `png`, `bmp`, `webp`. |
 | `JPEG_QUALITY` | `95` | Quality 0-100, used only by the JPEG encodings. |
 | `FLIP` | unset | `VERTICAL`, `HORIZONTAL` or `BOTH`. |
+| `PREVIEW` | unset | `true` opens a window of the published frames; `q` stops the node. |
 | `CAPTURE_FRAMES` | `0` | Stop after this many frames. 0 runs until the tick closes. |
 
 Resizing only happens when both `IMAGE_WIDTH` and `IMAGE_HEIGHT` are set.
@@ -94,8 +101,8 @@ Every dependency ships prebuilt wheels for linux-x86_64, linux-aarch64 and macos
 so the node installs with no system packages and no compiler.
 
 **Requirements:** dora 1.0+ (verified with `dora-cli 1.0.1`), Python 3.11+, `uv`, and a
-V4L2 camera. On a bare Linux image `opencv-python` also needs the libGL shared libraries
-(`libgl1`, `libglib2.0-0`), which it links at import time.
+V4L2 camera. `PREVIEW` also needs a display. On a bare Linux image `opencv-python` needs
+the libGL shared libraries (`libgl1`, `libglib2.0-0`), which it links at import time.
 
 ## Test
 
diff --git a/dataflow.yml b/dataflow.yml
index 6e0a046..bd947cd 100644
--- a/dataflow.yml
+++ b/dataflow.yml
@@ -6,11 +6,12 @@ strict_types: true
 nodes:
   - id: camera
     path: dora-webcam
-    build: pip install .
+    build: uv pip install .
     inputs:
       tick: dora/timer/millis/33
     outputs:
       - image
 
-  # Nothing consumes the frames here; the point is that the node opens, encodes
-  # and publishes. dataflow_view.yml is the pair that shows them.
+  # Nothing consumes the frames: the point is that the node opens, encodes and
+  # publishes. Set PREVIEW=true to watch them in a local window instead of
+  # wiring a viewer node.
diff --git a/dataflow_view.yml b/dataflow_view.yml
deleted file mode 100644
index c499cac..0000000
--- a/dataflow_view.yml
+++ /dev/null
@@ -1,23 +0,0 @@
-# The camera into the viewer: the end-to-end check of the pair.
-#
-# Not run by CI. It fetches dora-image-view over the network, and it needs a
-# tag to exist in that repository; CI validates and runs dataflow.yml, which
-# needs neither.
-strict_types: true
-
-nodes:
-  - id: camera
-    path: dora-webcam
-    build: pip install .
-    inputs:
-      tick: dora/timer/millis/33
-    outputs:
-      - image
-
-  - id: view
-    git: ssh://git@gitea.liria.cl:5001/liria/dora-image-view.git
-    tag: v0.1.0
-    build: pip install .
-    path: dora-image-view
-    inputs:
-      image: camera/image
diff --git a/dora-node.yml b/dora-node.yml
index 3feabe1..7819196 100644
--- a/dora-node.yml
+++ b/dora-node.yml
@@ -13,10 +13,10 @@ keywords: [opencv, camera, webcam, video, capture, image, v4l2]
 
 runtime: python
 entrypoint: dora-webcam
-# `dora build --uv` / `dora run --uv` rewrites this to `uv pip install .` and
-# gives the node its own managed venv under `.dora/python-envs/`, so the
-# dependencies it sees at runtime are the ones installed here.
-build: pip install .
+# Run the dataflow with --uv, which gives the node its own managed venv under
+# `.dora/python-envs/`, so what it imports at runtime is what was installed
+# here. Without --uv this needs a virtualenv to install into.
+build: uv pip install .
 dora: ">=1.0"
 
 inputs:
@@ -59,6 +59,12 @@ env:
     description: Quality 0-100, used only by the JPEG encodings.
   FLIP:
     description: Flip the frame. One of VERTICAL, HORIZONTAL or BOTH. Unset means no flip.
+  PREVIEW:
+    type: bool
+    description: >-
+      Open a local window showing the frames as they are published, so a camera
+      can be checked without wiring a viewer. Press q to stop the node. Ignored
+      under CI, where there is no display.
   CAPTURE_FRAMES:
     type: int
     default: 0
@@ -76,7 +82,7 @@ example: |
   - id: camera
     git: ssh://git@gitea.liria.cl:5001/liria/dora-webcam.git
     tag: v0.1.0
-    build: pip install .
+    build: uv pip install .
     path: dora-webcam
     inputs:
       tick: dora/timer/millis/33
diff --git a/dora_webcam/main.py b/dora_webcam/main.py
index b2c4f93..6f2b837 100644
--- a/dora_webcam/main.py
+++ b/dora_webcam/main.py
@@ -1,8 +1,8 @@
 """A dora webcam source: captures frames and publishes them as std/media/v1/Image.
 
 Each `tick` reads one frame, optionally flips and resizes it, encodes it, and
-sends it. The node stops when the tick input closes, or after CAPTURE_FRAMES
-frames if that is set.
+sends it. The node stops when the tick input closes, after CAPTURE_FRAMES
+frames if that is set, or when `q` is pressed in the preview window.
 """
 
 import argparse
@@ -11,7 +11,7 @@ import os
 import cv2
 from dora import Node
 
-from dora_webcam import camera, encode, image
+from dora_webcam import camera, encode, image, preview
 
 FLIPS = {
     "VERTICAL": 0,
@@ -43,6 +43,8 @@ def main() -> None:
     # 0 runs until the tick closes; a positive count is what lets CI run the
     # dataflow to completion instead of killing it on a timeout.
     limit = _int("CAPTURE_FRAMES") or 0
+    # Never under CI: there is no display there, and imshow would fail.
+    previewing = os.getenv("PREVIEW", "").lower() in ("1", "true") and not ci
 
     node = Node(args.name)
     sent = 0
@@ -66,6 +68,11 @@ def main() -> None:
             if width and height and (frame.shape[1], frame.shape[0]) != (width, height):
                 frame = cv2.resize(frame, (width, height))
 
+            # After the flip and the resize, so what is on screen is what is
+            # published rather than what came off the sensor.
+            if previewing and preview.show(frame):
+                break
+
             # Taken before encoding: a compressed payload's byte count is not
             # its pixel dimensions.
             frame_height, frame_width = frame.shape[:2]
@@ -87,6 +94,9 @@ def main() -> None:
     finally:
         capture.release()
 
+        if previewing:
+            preview.close()
+
 
 def _parse_args() -> argparse.Namespace:
     parser = argparse.ArgumentParser(
diff --git a/dora_webcam/preview.py b/dora_webcam/preview.py
new file mode 100644
index 0000000..4b0558b
--- /dev/null
+++ b/dora_webcam/preview.py
@@ -0,0 +1,36 @@
+"""An optional local preview window.
+
+A source node showing its own frames overlaps with what a viewer node does, and
+that is the point: it means checking that a camera works needs this repository
+only, not a second node wired into a dataflow. It is off unless asked for, and
+never opens under CI.
+"""
+
+import cv2
+import numpy as np
+
+WINDOW = "dora-webcam"
+
+
+def show(frame: np.ndarray) -> bool:
+    """Display one frame and report whether the viewer asked to quit.
+
+    Parameters
+    ----------
+    frame : np.ndarray
+        The captured BGR frame, before encoding, which is what a person wants
+        to look at.
+
+    Returns
+    -------
+    bool
+        True when `q` was pressed, which stops the node.
+
+    """
+    cv2.imshow(WINDOW, frame)
+    return cv2.waitKey(1) & 0xFF == ord("q")
+
+
+def close() -> None:
+    """Tear the window down, if one was ever opened."""
+    cv2.destroyAllWindows()