Shift-1 FAQ

What is Shift-1?

Shift-1 is a state-of-the-art coding router that cuts cost by 55% with no drop in quality. You can use it in Codex or Claude Code by installing it at shift.ac and then selecting Shift-1 in the model picker. Shift-1 routes each LLM request between GPT-6 Astra and GPT-6.1-Sol in Codex, and between Claude Opus 5.5 and Claude Sonnet 5 in Claude Code.

Who is it for?

Developers who use Codex or Claude Code and want to control their costs.

Does it use my ChatGPT or Claude subscription?

No. Shift-1 runs on your own OpenAI or Anthropic API key, so every turn is billed at the provider’s API prices to the account that owns that key.

Can I still use other models?

Yes. Shift-1 sits in the model picker next to the OpenAI or Anthropic models you use.

How does the router work?

A custom decision model, trained with AC2, Applied Compute’s training and inference cloud for open models, makes every routing decision. Before each request it picks which model should take the next step. It tends to send exploring, diagnosing and planning to the stronger model, then hands the rest of the work to the lower-cost model, which picks up with everything done so far.

Can my company train its own router?

Yes. Shift-1’s router was trained on general coding and knowledge work, but the same approach adapts to your workload and the models you use. Get in touch to train one on AC2.

Does routing happen once per conversation or per request?

Per request. Each step of a turn, such as a tool call, is routed on its own, so one session can move between the two models many times. The Logs page at shift.ac shows which model served each request and marks each switch in the conversation view.

Is every request routed?

Conversation turns are. Claude Code’s small side requests, such as chat titles, summaries and classifiers, go straight to a small Anthropic model on your key. Codex compacts long conversations in the background on a standard OpenAI model.

Which models does Shift-1 route between?

Shift-1 routes between two models from one provider, chosen by the app you use:

App	Stronger model	Lower-cost model
Codex (CLI and desktop)	GPT-6 Astra	GPT-6.1-Sol
Claude Code and Claude Desktop	Claude Opus 5.5	Claude Sonnet 5

Does Shift-1 change how my app behaves?

As little as possible.

Is every feature supported?

No. Some features of Codex and Claude Code aren’t supported through Shift-1. If something you rely on doesn’t work, let us know.

Can I change the model pair?

No. Shift-1 always uses the pair for your app, but we’re working on supporting more models in the future. If you want to train your own custom router for your workload, reach out.

How are savings calculated?

Savings are what your Shift-1 turns would have cost on the stronger model, minus what they actually cost on the model that served them.

Where do I see my savings?

On the Logs page at shift.ac.

Will this match my provider’s bill?

Not exactly. These are estimates from recorded token usage and published API prices. Your OpenAI or Anthropic invoice is the source of truth and can differ because of credits, negotiated discounts or price changes.

Privacy and zero data retention (ZDR)

Zero data retention is on by default. With it on, Shift doesn’t store the prompts or responses of new requests; it records only usage, cost and savings, so the Logs page can’t show how requests were routed. You can turn it off during setup or under Settings → Privacy at shift.ac.

What is stored when ZDR is off?

Each request’s prompt and response are saved as a trace so you can review conversations on the Logs page.

What is stored when ZDR is on?

Metadata only: time, model served, token counts, status, cost and savings. No prompt or response content is kept.

Does Shift’s ZDR change what OpenAI or Anthropic keep?

The provider’s own data policies for your API key apply. If you need zero data retention from OpenAI or Anthropic, arrange it with them for your organization.

Keys and billing

Shift uses two keys: your provider API key (OpenAI for Codex, Anthropic for Claude), which pays for the models, and a Shift key, which lets your apps use Shift.

Who bills me for model usage?

OpenAI or Anthropic, at their API prices, on the account that owns your API key. That covers every routed turn and every side request.

How is my provider key stored?

Encrypted in Shift’s database. It’s decrypted only to make requests on your behalf.

How do I revoke a Shift key?

In Settings → Shift keys, click Revoke, then Confirm revoke. Shift checks the key on every request, so the next request with that key is refused. Run acshift install to set up a new key.

How do I replace or remove my provider key?

In Settings, under your OpenAI or Anthropic key, paste a new key to replace it, or click Remove. Shift-1 stops working in the apps that use that provider until you connect a key again.

Installing Shift-1

One command installs the Shift CLI and asks which apps to connect:

$ curl -fsSL https://shift.ac/install.sh | sh

What do I need first?

At least one supported app: Codex 0.148 or later (CLI or desktop), Claude Code 2.1.257 or later, or Claude Desktop on macOS.
macOS or Linux. Windows isn’t supported yet.
An OpenAI API key for Codex, an Anthropic API key for Claude, or both.

Uninstalling Shift-1

acshift uninstall puts your apps back the way they were before setup.

Quit Codex (desktop app and CLI sessions) so your chats can be moved back.

Run one of these:

acshift uninstall                  # disconnect every app
acshift uninstall --agent codex    # Codex only
acshift uninstall --agent claude   # Claude Code and Claude Desktop only

At shift.ac, go to Settings, revoke your Shift keys, and remove your provider keys if you don’t plan to come back.
Optionally, delete the Shift CLI itself: rm ~/.local/bin/acshift.
Restart your apps.

What happens to Codex chats I started on Shift-1?

They stay on your machine under the Shift provider. Uninstalling doesn’t delete them.

Can I switch back without uninstalling?

In Codex, pick a different model in the /model picker. In Claude Desktop, choose Anthropic sign-in on the sign-in screen. For Claude Code, run acshift uninstall --agent claude.

Does uninstalling delete my data at shift.ac?

No. Your account and any stored traces stay until they expire. Email [email protected] if you want your data deleted.