Set Up ASI:One for Coding

Set Up ASI:One in T3 Code

Overview

T3 Code is a desktop and web app for driving the coding agents installed on your machine. It doesn’t talk to ASI:One directly. It runs ASI:One through an agent you’ve already set up, either OpenCode or the Codex CLI. Pick the one you use:

OpenCodeCodex CLI
Set up firstOpenCode with ASI:OneCodex with ASI:One
Extra setup in T3 CodeNone. Models come from your OpenCode config.A separate Codex home, plus the models added by hand.

Prerequisites

  • T3 Code installed.
  • An ASI:One plan that includes asi1-ultra. The same key also works for asi1, asi1-ultra-1m and asi1-mini.
  • OpenCode or the Codex CLI set up with ASI:One, as described in the section for that agent below.

With OpenCode

T3 Code starts its own OpenCode server and lists whatever models OpenCode knows about, so the ASI:One provider from your OpenCode setup carries over.

Set up OpenCode

  1. Follow Set Up ASI:One in OpenCode through Verify. T3 Code needs OpenCode 1.14.19 or newer.
  2. Put the asi provider in ~/.config/opencode/opencode.json, not a project’s opencode.json. T3 Code threads run in many folders, and the global config makes ASI:One available in all of them.

Enable the provider

  1. Open Settings → Providers and turn on OpenCode. Leave Server URL empty so T3 Code starts OpenCode for you.
  2. Click Refresh provider status.

Run it

Start a thread, pick the OpenCode provider, and choose ASI1 Ultra. The model names are the name values from your opencode.json.

T3 Code caches OpenCode’s config while its OpenCode server is running. After editing opencode.json, wait about 30 seconds without refreshing, then click Refresh provider status so the change is picked up.

With the Codex CLI

This path needs macOS or Linux, like the Codex setup it builds on.

Follow Set Up ASI:One in Codex through Run it, and confirm codex exec -p asi -m asi1-mini "Reply with exactly: pong" replies.

Create the Codex home

We need to give it a separate Codex home to use ASI:One, built from the profile you already made:

mkdir -p ~/.codex-asi && chmod 700 ~/.codex-asi
cp ~/.codex/asi.config.toml ~/.codex-asi/config.toml

T3 Code won’t start Codex unless it reports a login. Log the new home in with the same key. This reads the key out of the config file, so it never lands in your shell history:

grep '^args = ' ~/.codex-asi/config.toml \
  | cut -d'"' -f2 \
  | CODEX_HOME="$HOME/.codex-asi" codex login --with-api-key

Then confirm it prints Logged in using an API key:

CODEX_HOME="$HOME/.codex-asi" codex login status

Use $HOME, not ~, inside CODEX_HOME=.... The tilde isn’t expanded there, and Codex reports that the folder doesn’t exist.

Add the provider

  1. Open Settings → Providers and add a Codex instance. Name it, for example, “Codex ASI”.
  2. Set CODEX_HOME path to ~/.codex-asi. If T3 Code doesn’t accept ~, use the full path. Leave Shadow home empty.
  3. Save, then click Refresh provider status.

Add the models

T3 Code’s picker lists OpenAI models only and doesn’t read the default model from config.toml, so add the ASI:One models by hand.

  1. Still in the “Codex ASI” instance, scroll to Models and click + Add custom model.
  2. Enter asi1-ultra.
  3. Repeat for asi1, asi1-ultra-1m and asi1-mini if you want them in the picker too.
  4. Make sure each one’s toggle is on.

Run it

Start a thread, pick the “Codex ASI” instance, and choose asi1-ultra.

Keep your regular Codex instance for OpenAI models. Threads in the ASI instance don’t show up in your normal Codex history.

Troubleshooting

OpenCode

SymptomCause and fix
No ASI:One models in the pickerThe asi provider is in a project opencode.json instead of ~/.config/opencode/opencode.json, or T3 Code is still using its cached config. Move it, wait 30 seconds, then click Refresh provider status.
The provider reports a version errorOpenCode is older than 1.14.19. Upgrade it, then refresh.
Error: failed to authenticate user or 401The key in OpenCode’s auth.json is missing or wrong. Re-run the credential step from the OpenCode setup.

Codex CLI

SymptomCause and fix
The instance reports it isn’t logged inRe-run the login step, then click Refresh provider status.
404 model not foundAn OpenAI model was picked in the ASI instance, or a custom model name is misspelled. Use asi1, asi1-ultra, asi1-ultra-1m or asi1-mini.
context_length_exceeded, or 400 tool type 'web_search' is not supported~/.codex-asi/config.toml is missing a setting from the Codex profile. Copy ~/.codex/asi.config.toml over it again.
401The key is wrong or has been revoked. Create a new one at asi1.ai/developer, update both config files, and re-run the login step.

T3 Code runs the same agentic harness underneath, so anything else is covered in the troubleshooting for OpenCode or Codex.

Next steps

  1. OpenCode: the same models in OpenCode
  2. Codex: the same models in the Codex CLI
  3. ASI:One Models: choosing between asi1, asi1-ultra, asi1-ultra-1m and asi1-mini