Sephir

The agent layer for the browser

Don’t just chatwith AI.Run an agent in every tab.

Multi-turn conversations, tool calls, and cross-tab workflows — powered by the ChatGPT, Claude or Gemini subscription you already pay for. Local-first. One-time payment.

Install for ChromeWatch the agent run· 47s

Already paying for ChatGPT Plus, Claude Pro or Gemini Advanced? Sephir uses them. · 7-day trial, no credit card

Works withChatGPT PlusClaudeGeminiMistralOpenRouter
sephir · compare-tabs
agent · 0.0k
Compare these three tabs on price, weight, and warranty.
  • extractPageText(tab 1)
  • extractPageText(tab 2)
  • extractPageText(tab 3)
ItemPriceWeight
Cybex Pro$2491.8 kg
Helix Mk II$2891.5 kg
Aerion Lite$2191.6 kg
0 tools · runningcost · —

The 30-second proof

Three tabs, one prompt, one comparison.

The kind of workflow the agent runs without prompting tricks. Pin a few pages, type one line, and watch a real tool-using loop turn three tabs into a Markdown table you can copy and ship.

  1. Cybex Pro — Spec
    Helix Mk II — Specs
    Aerion Lite — Specs

    3 tabs · ready

    Pin three product pages.

    Tabs the agent will read.

  2. Compare these tabs on price, weight, and warranty.

    /compare

    Type one prompt.

    Compare these on price, weight, warranty.

    • extractPageText(tab 1)
    • extractPageText(tab 2)
    • extractPageText(tab 3)
    • 3 calls · 0 errors

    Watch the tool calls.

    extractPageText runs across each tab — auditable, in order.

  4. markdown
    Item$kg
    Cybex Pro2491.8
    Helix Mk II2891.5
    Aerion Lite2191.6

    Get a Markdown table.

    Streams in. Copy button. Saved to your conversation history.

Use what you already pay for

Sign in with ChatGPT Plus. Pay nothing per token.

You already pay $20 a month to OpenAI. Sephir uses that — not a second API budget we resell to you with markup. ChatGPT Plus is the only major AI subscription that allows it, and Sephir is one of the few extensions that actually does. For everything else — Claude, Gemini, Mistral, OpenRouter — bring your own key. Either way, your tokens stay on your account.

Live · OAuth

ChatGPT Plus

Codex routes over your ChatGPT Plus or Pro subscription — the only major AI provider that allows it.

Sign in with OAuth
cost·$0 in tokens
BYOK

Anthropic Claude

Anthropic doesn't expose subscription OAuth. Paste your API key and your Claude Pro usage stays where it is.

Bring your own key
cost·pay Anthropic directly
BYOK

Google Gemini

Google AI subscriptions aren't OAuth-able. Use your Google AI Studio API key — billed by Google, not us.

Bring your own key
cost·pay Google directly
BYOK

OpenAI, Mistral, OpenRouter

Every other provider via plain API key. We never proxy or resell.

Bring your own key
cost·pay your provider

We never proxy your prompts through our servers. We never bundle credits. We never set a token markup. If you cancel your ChatGPT Plus subscription tomorrow, your Sephir install keeps working with any API key you paste in. That’s the meaning of bring-your-own.

In 2023 I built the original ChatGPT File Uploader. One hundred and twenty thousand people installed it. Sephir is its proper successor. Broader in scope, built around the same principles — transparent, BYOK, maintained.

From the maker

Honest pricing. BYOK from day one. Cancel button on the main settings page, not behind three clicks. Local-first storage. Updates within 48 hours of every ChatGPT, Claude, Gemini redesign.

— the original creator

Pricing

Lifetime. Not a subscription.

One payment unlocks the agent surface forever. No monthly fee, no auto-renew, no token reselling. BYOK is always free.

Free

$0forever

No account required. Install and you’re in.

  • BYOK across every major provider
  • Sign in with ChatGPT Plus (Codex OAuth)
  • Single-turn chat in any tab
  • Selection popover & page summarize
  • Conversation history stored locally on your device
Install for Chrome

Pro · Lifetime

$39$99one-time

Limited early-adopter seats — first 100 only.

Pay once. All future Sephir updates included, forever.

  • Everything in Free
  • Multi-turn agent loop with tool calls
  • extractPageText · openTab · compareTabs · bookmark RAG
  • Saved skills + schema-aware extraction
  • Conversation export & full audit timeline
  • All future updates included, forever
Start 7-day trial

Refund within 30 days · Lifetime means lifetime · No credit card for trial

If we ever ship our own hosted AI, it’ll be a separate, opt-in usage subscription. Your lifetime licence is for the surface — not for inference we host.

See the full breakdown

Frequently asked

Honest answers, not marketing.

  • Yes. Connect any OpenAI, Anthropic, Gemini, Mistral, or OpenRouter account. Your prompts go straight from your browser to your provider — we never proxy them through our servers.

  • One payment. All future updates to the Sephir extension included. No major-version upgrade fee, ever. If we ship our own hosted AI someday, it ships as a separate opt-in usage subscription — your lifetime licence covers the agent surface, not the inference we host.

  • Because every multi-AI sidebar runs one and most users complain about auto-renew traps. We'd rather sell once, ship updates, and stay focused. If we ever change our minds, you keep the lifetime licence you bought at the price you paid.

  • There's nothing recurring to cancel — that's the point. If you want a refund within 30 days of purchase, the button is on your account page. We honour it without an email thread.

  • Different incentives. They run on monthly subscriptions backed by a proprietary credit pool — you pay them for AI you could otherwise pay your provider for directly, and their 1-star reviews are dominated by auto-renew traps and missing cancel buttons. Sephir is a one-time lifetime payment with BYOK direct to your provider (or ChatGPT Plus via OAuth) — Sephir never sits between you and your token bill. Feature-wise we overlap a lot; the difference is the billing model and what we'll never do (no credit pool, no auto-renew, no overlay ads on chatgpt.com).

  • Yes. We attach source recipes to each host page and update them within 48 hours of every interface redesign. A public status page tracks compatibility per release.

  • Conversation history, keys, and tokens live in chrome.storage.local on your device. We don't sync them to our servers by default. If we ever ship optional encrypted cloud sync, it stays opt-in with the keys derived per install — we won't be able to read your data even if we wanted to.

  • Form-filling tools are partial. Cloud sync is on the roadmap, not shipping today. Edge isn't a first-class target — the Chrome listing usually works there but isn't tested. Skills marketplace (sharing saved skills across users) is further out.

  • Forever. Free covers BYOK across all providers, ChatGPT Plus OAuth, single-turn chat, selection popover, and page summarize. Pro Lifetime unlocks the multi-turn agent loop, tool calls, saved skills, and full audit timeline.

  • The team behind the original ChatGPT File Uploader (2023, 120,000 users). Sephir is its proper successor — broader in scope, transparent on price, maintained with the same principles.

One more thing

Install Sephir. Use the AI you already pay for.

Install for ChromeSee pricing
lifetime
$39
early-adopter seats
limited
trial
7 days, no card
refund window
30 days