Codex + MCP video editing tutorial

How to merge video clips with Codex MCP and Medux

Use Codex and Medux through MCP to combine multiple video clips into one ordered MP4. This guide covers input preparation, the approval gate, task monitoring, and a concrete output check.

Watch the video editing overview: merge, split, trim, and process videos with Codex, MCP, and Medux.Watch on YouTube ↗

What you will do

Merge sample-clip-3s.mp4 and sample-clip-7s.mp4, then save and verify the output.

CodexMCPMeduxMP4Video merge

Codex-specific workflow

Run Merge Video Clips as a Codex MCP task

Use the active workspace as the source of truth. Ask Codex to identify the source video clips in the intended playback order, select the Medux video merge tool, and keep the Medux task ID and returned output with the rest of the project. Naming the input roles and the expected result prevents an agent from guessing which file should be used where.

Codex prompt pattern

In this workspace, use the Medux video merge tool through Medux MCP to merge video clips.
First inspect and identify the source video clips in the intended playback order.
Show me the exact tool arguments before execution.
After the task completes, return the merged MP4 and verify that every clip appears once in the correct order and the final video plays from start to finish.

Approval gate

Before approving the call, compare the selected tool, file or asset IDs, ordering, timing, and output settings with the request. If a local filename was mapped to an uploaded Medux file ID, keep that mapping visible so it can be audited later.

Result verification

Let Codex monitor an asynchronous task until it reaches a terminal state, then save or report the merged MP4. The final check is explicit: confirm that every clip appears once in the correct order and the final video plays from start to finish.

Before you start

Connect Medux to Codex

Make sure the Medux MCP server is available in Codex and your Medux credentials are configured.

Prepare the source clips

Place both MP4 files in the same workspace. Similar resolution, frame rate, codec, and audio settings help produce a cleaner join.

Merge two video clips in five steps

01

Describe the result in one prompt

Name the source files and ask Codex to use Medux. The tutorial starts with this focused request:

Use Medux to merge two video clips:
sample-clip-3s.mp4 and sample-clip-7s.mp4.
Codex prompt asking Medux to merge two MP4 video clips
Codex receives the two filenames and the desired output operation.
02

Let Codex inspect the workspace and request upload URLs

Codex confirms that both clips exist, identifies the Medux video merge tool, and requests temporary upload URLs and file IDs through MCP. Approve the Medux calls when Codex asks.

Codex requesting approval for the Medux file upload URL tool
Medux creates the temporary upload destination and asset identity for each clip.
03

Upload each MP4 to its signed URL

Codex uploads the local clips with curl. The real signed URLs are generated by Medux and expire, so do not hard-code them into a reusable script.

curl -sS -X PUT \
  -H "Content-Type: video/mp4" \
  --upload-file "./sample-clip-3s.mp4" \
  "SIGNED_UPLOAD_URL_FOR_CLIP_1"

curl -sS -X PUT \
  -H "Content-Type: video/mp4" \
  --upload-file "./sample-clip-7s.mp4" \
  "SIGNED_UPLOAD_URL_FOR_CLIP_2"
Responsive command blocks: long URLs and paths wrap at any point, so this page stays within the viewport on desktop and mobile.
Codex running curl commands to upload video clips to Medux
Codex can retry the upload if a signed storage path needs URL normalization.
04

Start the Medux merge task and monitor it

After both uploads succeed, Codex sends the two Medux file IDs in the intended order to the video merge tool. It keeps querying the same task until processing finishes.

Both uploads are complete.
Merge FILE_ID_1 followed by FILE_ID_2 with Medux,
then keep checking the task until the result is ready.
Medux video merge task queued and monitored by Codex
Codex monitors the queued Medux task instead of asking you to check it manually.
05

Download, preview, and verify the merged video

When Medux returns the result URL, Codex downloads the output as merged-sample-clips.mp4. The demo verifies a duration of 10.023220 seconds and a file size of approximately 9.2 MB.

Codex reports the merged video filename duration and size
Codex returns the local file and verification details.
Preview of the completed merged MP4 video
Preview the final MP4 and confirm clip order, transition timing, audio continuity, and playback quality.

Workflow at a glance

Describe the merge
Create upload URLs
Upload both clips
Run and monitor
Verify the MP4

Why use Codex, MCP, and Medux?

Codex handles the planning and coordination; MCP gives it a standard connection to Medux; Medux performs the media processing. You avoid building a custom upload interface, writing a dedicated API client, or switching between separate editing dashboards.

Result: one natural-language request becomes a repeatable video merge workflow and a verified MP4 output.

Frequently asked questions

Can Codex merge videos through MCP?

Yes. Once Medux is connected, Codex can create upload destinations, send the clips, start the merge task, poll its status, and download the finished MP4.

What should I check before merging clips?

Confirm the intended clip order and compare resolution, aspect ratio, frame rate, video codec, and audio settings. Similar source properties generally create a cleaner result.

What should I verify after the merge?

Check the clip order, transition point, total duration, audio continuity, playback quality, resolution, and output file size.

Continue with another practical Medux workflow for video, image, audio, or document processing.

Related Medux tutorials

How to Merge Video Clips with Claude MCP and Medux How to Replace a Video Character with Codex MCP and Medux How to Remove Video Subtitles with Codex MCP and Medux How to Create a Lip-Synced Avatar Video with Codex MCP and Medux

Quick answer

How do I run Merge Video Clips with Codex MCP?

Codex can use the Medux video merge tool through Medux MCP to combine multiple video clips into one ordered MP4. The workflow identifies the exact inputs, reviews the tool arguments, monitors processing, and verifies the returned result.

What does this Medux tutorial cover?

Codex can use the Medux video merge tool through Medux MCP to combine multiple video clips into one ordered MP4. The workflow identifies the exact inputs, reviews the tool arguments, monitors processing, and verifies the returned result.

Related topics: Merge Video Clips · Merge Video Clips with Codex MCP · Medux MCP tutorial

Build with the API

API reference for this workflow

Use the API reference to automate this workflow, or follow the matching guide in our official GitHub repository.