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Atmosphere OS

The position

Your work is a file you own. No acquisition can take it.

Every plan in Atmosphere OS lives in your browser and saves to a file on your disk. There is no account behind it. Nothing is uploaded. The server holds catalogues — stem prices, signature atmospheres, planning bands — and if it disappeared tomorrow you would lose the catalogue and keep the evening.

That is not a privacy posture. It is a durability one. A planner works on an event for fourteen months and looks back at it for years afterwards, and in that time the software they used gets bought, repriced, rebuilt or switched off. Those are not rare events in this category. They are the normal life cycle of a venue-facing SaaS product, and every one of them is somebody else deciding what happens to your work.

Diagram · the dependency

Both models look the same until somebody else makes a decision.

Where the work lives, in two modelsIn the subscription model the plan lives on a vendor's server and the planner reaches it through an account, so access depends on the account, the connection and the vendor continuing to exist. In the local-first model the plan is a file in the planner's own browser and on their own disk; the server holds reference data only, and losing it costs the catalogue rather than the plan.THE USUAL ARRANGEMENTYoua browser, an accountneeds a signalTheir serveryour plan is hereWHAT ENDS ITAn acquisition, and a sunset dateA price change you did not chooseA card that lapsed in FebruaryA venue with no barsTHIS ONEYou, and the planthis browser · a file you keepoptionalA servercatalogues onlyWHAT SURVIVES ITThe plan, because it is a file on your diskThe evening, because the app runs offlineThe maths, because the rules are publishedThe catalogue goes; the plan does not

Happening now

Prismm is being switched off, and the dates are not far away.

Cvent acquired Prismm and is folding it into Cvent Event Diagramming. Creating new events in Prismm closed on 8 July 2026. From 1 October 2026 every event, floor plan and report becomes view-and-export only, and on 31 December 2026 access to prismm.com ends and support is turned off. Only events dated 1 January 2022 and later carry across to Cvent Event Diagramming; anything older cannot be reached from it at all. Standard templates do not transfer either — they have to be rebuilt as saved layouts.

Those dates are Cvent's, from its own migration page, and they are the ones to check against rather than this one — a sunset schedule is exactly the kind of thing that moves.

Worth doing before October

  • Export anything dated before 2022 first. That is the set with no destination.
  • Export the reports, not only the pictures. A floor plan PDF is a picture of a decision; the table and guest lists are the decision.
  • Photograph or export your templates. They are the part that is explicitly not migrating.

Source: Cvent, Prismm to Cvent Event Diagramming migration resources (opens in a new tab)

What this application is not

Atmosphere OS is not a 3D room diagramming tool and there is no walkthrough in it. If what you used Prismm for was the render you show a client, this does not replace that and you should go and find something that does.

What it does is the half those tools stop before: turning a design decision into its production consequence — stems into a quote-ready brief, a table shape into a centrepiece count into a rental order into a load-in time — and handing that to the people who have to build it.

How every figure is produced

Bring a plan in

A guest list or a table schedule, out of whatever you were using before.

Export a CSV, a TSV or a JSON list from the other tool, point the columns at what they mean, and check what it would write before it writes it. Nothing is uploaded — the file is read in this tab, and this works with the network off.

It is a file

Save the event to your own disk and open it anywhere. No export tier, no seat, no expiry. The studio is the unit — one flat price, not a charge per person who opens the file. The format is plain JSON and the schema is in the repository.

It runs with no signal

Installed, the whole application works in a building with no bars, which is most of the buildings this work happens in. Not one competitor in this category does.

The maths is published

Every computed figure cites the rule that produced it, and the rulebook is a page anybody can read. The same inputs produce the same answer, this year and next.