Codiner

Reply to your coding agent the way you mark up a draft.

Codiner is a web UI for Claude Code. Select any passage of the agent's answer and comment on it in the margin. Answer its questions where it asks them. Send everything in one go. Run many sessions side by side, each with a small critter that shows what it is doing.

Install Source on GitHub Free and open source. Needs Claude Code.

This is a live copy, not a picture. Select text to comment on it. React, answer, dismiss, open the steps, or press Run in Terminal. It starts over a few seconds after you stop.

Reply in the margin

A chat box makes you quote by hand. In Codiner you select a passage and type your note beside it, the way you review a draft. A reaction is one click. A suggested answer is one click. Codiner turns all of it into one plain message.

What you see (try it)
What the agent sees
Comments

Select, then type

A comment card opens in the right margin, level with the passage. Cards stack so they never overlap. Sent comments stay as read-only cards.

Reactions

An emoji on any paragraph

Move the pointer to a paragraph and click the faint emoji at its left. Press and hold for your most used ones. A reaction on an item counts as a reply to it.

One send

Nothing slips past

A panel lists the open questions and items. If you send while some are still open, Codiner tells you first. The agent gets one line for the items you set aside.

Five kinds of content

Codiner tells the agent to mark each part of its reply. Each kind looks different, so you can see at a glance what needs you.

Answer

The direct answer, first, in the accent colour.

Consider

A problem, risk or trade-off that wants your attention. Reply, dismiss it, or mark it done.

Ask

A question in place, with suggested answers to click and a box for your own.

Details

Supporting detail, folded until you open it. The steps fold too: thinking, commands and edits, each with its input and output.

Run

A command you must run yourself. Run in Terminal opens it in a new window, and the exit code and output go back to the agent.

Many sessions, one critter each

Run sessions side by side, grouped by folder. Each agent dresses its own critter, so you can tell them apart. The pose shows the status. The face shows how full the context is: the eyes droop, it sweats, then it falls asleep.

Working
Needs permission
Has a question
Your turn
Context filling
Time to compact
Lead agent

One agent to watch the rest

The Lead view shows every session as a card, beside a chat with one more agent. It can read, message, start and compact the other sessions. Its messages wait in an inbox for you to send, unless you turn on Auto-send.

History

Pick up any conversation

Resume… lists every Claude Code conversation on your machine, including the ones you started in a terminal. Edit or delete a sent message, and the agent forgets everything after it.

Slash commands

Your skills, your commands

Type / for the commands of the session, with descriptions. A message that is only a slash command runs as if you typed it in the terminal.

Every session is Claude Code

Codiner is a window onto Claude Code, not a replacement for it. You must have Claude Code installed and logged in. Codiner does not talk to any model itself.

  • Each session is a real claude process, which Codiner starts in Claude Code's documented headless mode.
  • Every command, file edit and tool call goes through Claude Code, with its permission prompts. Codiner shows the prompts, and you answer them.
  • Your subscription, settings, hooks, CLAUDE.md, skills and MCP servers all apply, as in the terminal.
  • Codiner removes API keys from the environment of the process, so a session cannot bill per token by accident.
  • The server listens on 127.0.0.1 only and rejects requests from other origins. A web page you visit cannot reach it.

Codiner is an independent open-source project. It is not affiliated with, endorsed by or sponsored by Anthropic. Claude and Claude Code are trademarks of Anthropic, PBC.

Install

You need Claude Code, logged in, and Node 23.6 or later.

Let your agent do it

Paste this into a terminal

claude "Install Codiner for me: clone https://github.com/huttj/codiner into ~/codiner, run npm install, then start it with npm start in the background. Tell me when http://localhost:4545 answers."

Claude Code asks before it runs each command.

By hand

Four commands

git clone https://github.com/huttj/codiner ~/codiner
cd ~/codiner
npm install
npm start

Then open http://localhost:4545. Use npm run dev to work on Codiner itself.

✍️

From the makers of Marginer. Codiner's comments use Marginer's text anchoring and its > quote + note format. Marginer does the same for any web page: highlight, add a note or a reaction, and paste the notes anywhere.

Questions

Does it cost anything?

Codiner is free and MIT licensed. Your sessions use your own Claude Code plan, the same as in the terminal.

Is my code sent anywhere new?

No. Codiner runs on your machine and talks only to the claude processes it starts. Claude Code talks to Anthropic as it always does.

Can I still use the terminal?

Yes. Claude Code keeps its own transcripts, so claude --resume picks up any Codiner session, and Codiner can open any terminal session.

Can I tell every session how to write?

Yes. ~/.codiner/AGENTS.md goes into the system prompt of every session. Edit it in Settings. By default it asks the agent to write in Simplified Technical English.

Does it work on Windows or Linux?

The server is plain Node, so it should. Run in Terminal and the native folder dialog are macOS only.

Is Codiner made by Anthropic?

No. Codiner is an independent open-source project, and Anthropic does not endorse it. Claude and Claude Code are trademarks of Anthropic, PBC.