OpenAI launched 'Sign in with ChatGPT' at DevDay, letting users log into third-party apps with their ChatGPT account and spend their own plan's usage allowance inside those apps — so developers don't have to cover users' token costs. Sixteen launch partners: Cognition's Devin, Notion, Vercel, Warp, Amp, T3, Kilo Code, Conductor, Dactyl, Hyperagent, Vorflux, Hermes Agent, OpenCode, OpenClaw and Pi, with Lovable 'coming soon'. Airtable, Canva, GitLab, HubSpot and Supabase offer identity sign-in without the allowance.

The user sets a spending cap per app in ChatGPT settings; the app sees only a name, email and picture — never the user's conversations. Plus and Pro users' eligible usage counts toward their plan limits. On stage the framing was that builders can now 'compete on how good your product is, not on how many tokens you can afford to give away.'

The trade is dependency: the app's login, users' limits and cost structure all run through OpenAI's account system — a distribution and lock-in play aimed at ChatGPT's 1.2 billion weekly users. It sits alongside the day's other platform moves: plugin extensions turning plugins into full in-app experiences, MCP Events wiring automations, and the new Marketplace letting enterprise customers spend OpenAI commitments on partner software.