Use your own Claude or ChatGPT subscription in other apps: the cost, the rules, what to check

If you already pay for Claude Pro or Max, or ChatGPT Plus or Pro, running other apps on that plan is usually far cheaper than paying per token with an API key, because agent work burns tokens and a flat plan caps the bill. OpenAI has officially supported this since 29 September 2026 through Sign in with ChatGPT. Anthropic is stricter: the permitted route is an app that drives the official Claude Code you signed into yourself, not an app that asks for your Claude login.

That is the short answer. The rest of this post shows the maths from the providers' own price pages, the exact policy wording on each side, and the checks we run before listing an app on BringYourSubs.

How much cheaper is a Claude or ChatGPT plan than the API?

Here is what each billing route costs today, taken from the official pricing pages on 3 October 2026.

Route	Price	What you get	Where it runs out
Claude Pro	$20/month ($17/month billed annually)	Claude chat, Claude Code, Opus and Sonnet	Five-hour session limits plus weekly limits
Claude Max 5x / 20x	$100 / $200 a month	5x or 20x Pro's usage	Same windows, larger allowance
ChatGPT Plus	$20/month	Codex in web, CLI, IDE and iOS; GPT-6.1 Sol and GPT-6 Luna	Five-hour estimates (15 to 160 local GPT-6.1 Sol messages) and weekly limits
ChatGPT Pro	$100, $200 or $500 a month	Everything in Plus, more usage	OpenAI says Pro currently has no five-hour limit
Claude API, Opus 5.5	$4 per million input tokens, $20 per million output, $0.20 per million cache hits	Pay per token, no cap	Your card
OpenAI API, gpt-6.1-sol	$2 per million input, $10 per million output (short context)	Pay per token, no cap	Your card

Anthropic publishes the number that matters most. Its Claude Code cost docs say that across enterprise deployments "the average cost is around $13 per developer per active day and $150-250 per developer per month, with costs remaining below $30 per active day for 90% of users." A typical API user is already spending more than Max 5x, and the subscription puts a ceiling on the bad months.

To see why agent work gets expensive, take one long coding session on Opus 5.5 at list price. Say the agent takes 40 turns, re-reads 150,000 tokens of cached project context each turn, adds 20,000 fresh input tokens and writes 3,000 output tokens. That is 6 million cache-read tokens ($1.20), 800,000 input tokens ($3.20) and 120,000 output tokens ($2.40): about $6.80 before cache-write charges. Three sessions a day for 20 working days comes to roughly $400 a month. This is our own illustration using Anthropic's published rates, not a measured workload, but it shows the shape: agents loop, and every loop is billed.

Power users report bigger gaps. One r/ClaudeCode user posted that their last 30 days on a $100 Max plan would have cost $1,593 via the API. That is a self-reported figure, but it matches the direction of Anthropic's own averages.

The API still wins in three cases. OpenAI recommends an API key for "automation in shared environments like CI". Anthropic's legal page says developers building products or services for other people "should use API key authentication". And if you only use an agent a few times a month, metered billing can come in under $20.

Does OpenAI allow you to use your ChatGPT plan in other apps?

Yes, officially. At DevDay on 29 September 2026 OpenAI added plan usage to Sign in with ChatGPT, as TechCrunch reported, with 16 launch partners. OpenAI's help page spells out the rules:

• Eligible ChatGPT Plus and Pro subscribers can let an app use their plan for AI requests. Signing in and using your plan are separate permissions.
• "App usage counts toward your existing plan limits. Connecting an app does not add a new allowance, and the app may have its own fees."
• "Using your plan does not give the app access to your ChatGPT conversations or memories."
• Under Settings, Usage you can cap each app's weekly share of your plan. OpenAI calls that cap "a cap, not a separate allowance".

Notebookcheck found one detail worth knowing: signing out of the app does not stop the usage. You have to disconnect the app under ChatGPT Settings, Security and login.

On the developer side, OpenAI's docs say plan usage is currently open to open-source projects, personal projects that run locally and selected private apps. Paid or remotely hosted apps go through an interest form, which is why the commercial list is short for now.

Apps on BringYourSubs that OpenAI lists for plan usage: Amp, Conductor, Dactyl, Devin, Hermes Agent, Hyperagent, Kilo Code, Notion, v0 by Vercel and Warp, plus the open-source integrations OpenClaw, OpenCode and T3 Code. The full set is on works with ChatGPT and Codex.

Does Anthropic allow you to use your Claude subscription in other apps?

Only in one specific way, and the rules moved four times this year, so read this with today's date in mind.

Anthropic's Claude Code legal page says subscription OAuth "is intended exclusively for purchasers of Claude Free, Pro, Max, Team, and Enterprise subscription plans and is designed to support ordinary use of Claude Code and other native Anthropic applications." It adds: "Anthropic does not permit third-party developers to offer Claude.ai login into their own applications, or to route requests through Free, Pro, or Max plan credentials on behalf of their users."

The same page leaves one door open. The rule does not "prevent an end user from signing in to the unmodified Claude Code binary with their own Claude subscription, including where a platform hosts Claude Code."

How we got here:

• 20 February 2026. Anthropic updated its legal page to say OAuth tokens from consumer plans may not be used in other products, reported by The Register.
• 4 April 2026. Subscriptions stopped covering third-party harnesses such as OpenClaw, per VentureBeat. Boris Cherny, Anthropic's head of Claude Code, wrote that "our subscriptions weren't built for the usage patterns of these third-party tools."
• 13 May 2026. Anthropic announced that from 15 June, Agent SDK and third-party app usage would move to a separate monthly credit billed at API rates.
• 15 June 2026. Anthropic paused that change. Its help page now reads: "For now, nothing has changed: Claude Agent SDK, claude -p, and third-party app usage still draw from your subscription's usage limits." Ars Technica covered the reversal, and Anthropic says it will share any new plan before it takes effect.

The practical reading: an app that runs the official Claude Code you logged into on your own machine is on the permitted path. On BringYourSubs that includes Conductor, T3 Code, Happy, Munder Difflin, Cline through its Claude Code provider, and Zed. An app that asks you to paste a Claude token, or opens a Claude.ai login inside its own window, matches the pattern Anthropic's page prohibits. See the full list on works with Claude.

Is running apps on your own subscription better for privacy and control?

Partly, and the trade-off is worth knowing.

On control, plans are easier to live with. There is no API key sitting in someone else's database with your card behind it, OpenAI's per-app caps limit how much any one tool can spend, and you can disconnect an app in one place.

On data, the terms change. Consumer plans run under consumer terms. Anthropic's August 2025 update says Free, Pro and Max accounts, "including when you use Claude Code from accounts associated with those plans", may be used to train models if the setting is on, with five-year retention when it is on and 30 days when it is off. API use falls under Anthropic's Commercial Terms and is excluded. If your code is sensitive, check that setting in Claude's privacy controls before you route work through your plan. On the OpenAI side, connecting a plan does not expose your chats or memories to the app, but the app still sees whatever you send it.

What should you check before connecting your plan to an app?

These are the checks we apply to every listing.

1. It uses the provider's official route. Sign in with ChatGPT for OpenAI plans, or the unmodified Claude Code CLI for Claude plans. Avoid proxies and token-copying plugins.
2. It is honest about what stays on its own bill. Your plan covers model usage, not everything else. Notion's plan support needs a Notion Business or Enterprise workspace, and Dactyl charges $20 a month for its Builder plan to publish apps.
3. It shows usage and respects caps. You should see what a session costs your allowance and the app should stop cleanly at your limit rather than fail halfway through a task.
4. It runs a model strong enough for the job. Apps that load many tools or skills need frontier models; we explain why in why frontier models handle heavy tool loads.
5. You can read the code if you want to. OpenCode, Cline, Kilo Code, Zed, OpenClaw and T3 Code are open source.

The point of a plan is a known monthly cost for frontier models. The right app keeps it that way.