I’ve built a new app in Retool using the new app builder, but I want to let my users access it via our current Classic app (and slowly rebuild it over time).
I’ve already tried embedding it via an iFrame (in different ways) but nothing seems to work.
Anyone had any luck with doing something similar?
Fundamentally I want to put the new app under the module header I already have in place so I don’t have it feel like it switches to a whole new app.
Summary
Built an app in the new app builder and wants to surface it inside an existing Classic app (under the existing module header) so users don't feel like they're switching apps, but embedding the new app via an iFrame isn't working.
AI Response
Embedding a new app builder app inside a Classic app via the IFrame component is not currently a supported flow. A Retool staff member confirmed this exact scenario is not supported yet, though it is being tracked internally as a high-priority request. The failure is expected: new app builder pages set a restrictive frame-src content security policy, which blocks them from rendering in an iFrame, and the auth callback also breaks in that context. For now, the reliable path is to link out to the new app rather than iFrame it, and to keep classic-app reuse within modules (a Classic app concept). Watching the linked threads is the best way to catch when native support ships.
Sources
Embedding new Retool AI app into Classic app
Same scenario (embedding a new app builder app in a Classic app via iFrame yields an 'Invalid auth callback' error); Retool staff confirm it isn't currently supported but is being tracked as high priority.
Explains that the new React app builder page enforces a restrictive frame-src CSP header, which is why iFrame embedding of these apps fails.
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Hey @SamH, welcome to the community! So glad to see you're diving into the new app builder.
This isn't something we support just yet, but it's firmly on our radar. I've already updated the internal ticket with the details you shared here, and I'll follow up the moment I have an update for you!
Hello again @SamH, this is on our to-do list right now, thanks for your patience! 
@ChiEn Hello! I’m new to retool - our org just signed the contract last month. We’re absolutely loving the new react app/builder experience.
I do have what seems to be the same issue as OP, but I want to confirm with you -
We have a legacy pricing calculator app (hosted on netlify) which is exposed in our salesforce quote page as an iframe. I’ve already ported this app over to retool and the goal is to show it in an iframe. I made sure the CSP entry was made and auto-login is enabled (we have SSO), but it looks like in-frame, cross-site embeds are not supported by retool for these new react apps.
You mentioned that you have a fix on your to-do list - will that fix help me in the use case I described above?