diff --git a/theatre/core/src/projects/Project.ts b/theatre/core/src/projects/Project.ts
index 472c727..76e6533 100644
--- a/theatre/core/src/projects/Project.ts
+++ b/theatre/core/src/projects/Project.ts
@@ -57,6 +57,7 @@ export default class Project {
       historic: config.state ?? {
         sheetsById: {},
         definitionVersion: globals.currentProjectStateDefinitionVersion,
+        revisionHistory: [],
       },
       ephemeral: {
         loadingState: {
diff --git a/theatre/core/src/projects/initialiseProjectState.ts b/theatre/core/src/projects/initialiseProjectState.ts
index 9717ccd..03405a7 100644
--- a/theatre/core/src/projects/initialiseProjectState.ts
+++ b/theatre/core/src/projects/initialiseProjectState.ts
@@ -7,7 +7,7 @@ import globals from '@theatre/shared/globals'
 
 /**
  * @todo this could be turned into a simple derivation, like:
- * editor.isReady: IDerivation<{isReady: true} | {isReady: false, readon: 'conflictBetweenDiskStateAndBrowserState'}>
+ * editor.isReady: IDerivation<{isReady: true} | {isReady: false, reason: 'conflictBetweenDiskStateAndBrowserState'}>
  */
 export default async function initialiseProjectState(
   studio: Studio,
@@ -42,6 +42,7 @@ export default async function initialiseProjectState(
       drafts.historic.coreByProject[projectId] = {
         sheetsById: {},
         definitionVersion: globals.currentProjectStateDefinitionVersion,
+        revisionHistory: [],
       }
     }
 
@@ -81,9 +82,8 @@ export default async function initialiseProjectState(
         useBrowserState()
       } else {
         if (
-          !browserState.exportBookkeeping ||
-          browserState.exportBookkeeping.basedOnRevisions.indexOf(
-            onDiskState.exportBookkeeping.revision,
+          browserState.revisionHistory.indexOf(
+            onDiskState.revisionHistory[onDiskState.revisionHistory.length - 1],
           ) == -1
         ) {
           browserStateIsNotBasedOnDiskState(onDiskState)
diff --git a/theatre/core/src/projects/store/storeTypes.ts b/theatre/core/src/projects/store/storeTypes.ts
index 1372434..57bc6c0 100644
--- a/theatre/core/src/projects/store/storeTypes.ts
+++ b/theatre/core/src/projects/store/storeTypes.ts
@@ -1,13 +1,9 @@
 import type {StrictRecord} from '@theatre/shared/utils/types'
 import type {SheetState_Historic} from './types/SheetState_Historic'
 
-export interface ProjectLoadedState {
-  type: 'loaded'
-}
-
 type ProjectLoadingState =
   | {type: 'loading'}
-  | ProjectLoadedState
+  | {type: 'loaded'}
   | {
       type: 'browserStateIsNotBasedOnDiskState'
       onDiskState: OnDiskState
@@ -34,7 +30,11 @@ export interface ProjectEphemeralState {
  */
 export interface ProjectState_Historic {
   sheetsById: StrictRecord<string, SheetState_Historic>
-  exportBookkeeping?: {revision: string; basedOnRevisions: string[]}
+  /**
+   * The last 50 revision IDs this state is based on, starting with the most recent one.
+   * The most recent one is the revision ID of this state
+   */
+  revisionHistory: string[]
   definitionVersion: string
 }
 
@@ -44,6 +44,4 @@ export interface ProjectState {
   ephemeral: ProjectEphemeralState
 }
 
-export interface OnDiskState extends ProjectState_Historic {
-  exportBookkeeping: {revision: string; basedOnRevisions: string[]}
-}
+export interface OnDiskState extends ProjectState_Historic {}
diff --git a/theatre/shared/src/testUtils.ts b/theatre/shared/src/testUtils.ts
index 965bc04..d142f1a 100644
--- a/theatre/shared/src/testUtils.ts
+++ b/theatre/shared/src/testUtils.ts
@@ -17,6 +17,7 @@ export async function setupTestSheet(sheetState: SheetState_Historic) {
     sheetsById: {
       Sheet: sheetState,
     },
+    revisionHistory: [],
   }
   const project = getProject('Test Project ' + lastProjectN++, {
     state: projectState,
diff --git a/theatre/studio/src/Studio.ts b/theatre/studio/src/Studio.ts
index 571f53a..6a347cf 100644
--- a/theatre/studio/src/Studio.ts
+++ b/theatre/studio/src/Studio.ts
@@ -17,6 +17,7 @@ import SimpleCache from '@theatre/shared/utils/SimpleCache'
 import type {IProject, ISheet} from '@theatre/core'
 import PaneManager from './PaneManager'
 import type * as _coreExports from '@theatre/core/coreExports'
+import type {OnDiskState} from '@theatre/core/projects/store/storeTypes'
 
 export type CoreExports = typeof _coreExports
 
@@ -173,7 +174,7 @@ export class Studio {
     this._store.redo()
   }
 
-  createExportedStateOfProject(projectId: string): string {
+  createExportedStateOfProject(projectId: string): OnDiskState {
     return this._store.createExportedStateOfProject(projectId)
   }
 }
diff --git a/theatre/studio/src/StudioStore/StudioStore.ts b/theatre/studio/src/StudioStore/StudioStore.ts
index 56a07bd..22c888b 100644
--- a/theatre/studio/src/StudioStore/StudioStore.ts
+++ b/theatre/studio/src/StudioStore/StudioStore.ts
@@ -28,6 +28,7 @@ import {persistStateOfStudio} from './persistStateOfStudio'
 import {isSheetObject} from '@theatre/shared/instanceTypes'
 import globals from '@theatre/shared/globals'
 import {nanoid} from 'nanoid'
+import type {OnDiskState} from '@theatre/core/projects/store/storeTypes'
 
 export type Drafts = {
   historic: Draft<StudioHistoricState>
@@ -271,23 +272,29 @@ export default class StudioStore {
     this._reduxStore.dispatch(studioActions.historic.redo())
   }
 
-  createExportedStateOfProject(projectId: string): string {
+  createExportedStateOfProject(projectId: string): OnDiskState {
+    const revision = nanoid(16)
+    // let's assume projectId is already loaded
+
+    this.tempTransaction(({drafts}) => {
+      const state = drafts.historic.coreByProject[projectId]
+
+      const maxNumOfRevisionsToKeep = 50
+      state.revisionHistory.unshift(revision)
+      if (state.revisionHistory.length > maxNumOfRevisionsToKeep) {
+        state.revisionHistory.length = maxNumOfRevisionsToKeep
+      }
+    }).commit()
+
     const projectHistoricState =
       this._reduxStore.getState().$persistent.historic.innerState.coreByProject[
         projectId
       ]
-    const revision = nanoid(16)
 
-    const s = {
-      revision,
-      definitionVersion: globals.currentProjectStateDefinitionVersion,
-      projectState: projectHistoricState,
+    const generatedOnDiskState: OnDiskState = {
+      ...projectHistoricState,
     }
 
-    // pushOnDiskRevisionBrowserStateIsBasedOn.originalReducer(s, revision)
-
-    const exportString = JSON.stringify(s, null, 2)
-
-    return exportString
+    return generatedOnDiskState
   }
 }
diff --git a/theatre/studio/src/UIRoot/BrowserStateIsNotBasedOnDiskStateModal.tsx b/theatre/studio/src/UIRoot/BrowserStateIsNotBasedOnDiskStateModal.tsx
deleted file mode 100644
index a508c41..0000000
--- a/theatre/studio/src/UIRoot/BrowserStateIsNotBasedOnDiskStateModal.tsx
+++ /dev/null
@@ -1,13 +0,0 @@
-import React from 'react'
-
-const BrowserStateIsNotBasedOnDiskStateModal: React.FC<{
-  projectId: string
-}> = (_props) => {
-  /*
-   * const projectId = props.projectId
-   * @todo implement me
-   */
-  return <div>@todo BrowserStateIsNotBasedOnDiskStateModal</div>
-}
-
-export default BrowserStateIsNotBasedOnDiskStateModal
diff --git a/theatre/studio/src/UIRoot/EnsureProjectsDontHaveErrors.tsx b/theatre/studio/src/UIRoot/EnsureProjectsDontHaveErrors.tsx
deleted file mode 100644
index 33f1dd7..0000000
--- a/theatre/studio/src/UIRoot/EnsureProjectsDontHaveErrors.tsx
+++ /dev/null
@@ -1,24 +0,0 @@
-import {usePrism} from '@theatre/dataverse-react'
-import {val} from '@theatre/dataverse'
-import React from 'react'
-import BrowserStateIsNotBasedOnDiskStateModal from './BrowserStateIsNotBasedOnDiskStateModal'
-import getStudio from '@theatre/studio/getStudio'
-
-const EnsureProjectsDontHaveErrors: React.FC<{}> = ({children}) => {
-  return usePrism(() => {
-    const projects = val(getStudio().projectsP)
-
-    const projectIds = Object.keys(projects)
-    for (const projectId of projectIds) {
-      const project = projects[projectId]
-      const loadingStateType = val(project.pointers.ephemeral.loadingState.type)
-      if (loadingStateType === 'browserStateIsNotBasedOnDiskState') {
-        return <BrowserStateIsNotBasedOnDiskStateModal projectId={projectId} />
-      }
-    }
-
-    return <div>{children}</div>
-  }, [children])
-}
-
-export default EnsureProjectsDontHaveErrors
diff --git a/theatre/studio/src/panels/DetailPanel/ProjectDetails.tsx b/theatre/studio/src/panels/DetailPanel/ProjectDetails.tsx
index 49fffde..5624e80 100644
--- a/theatre/studio/src/panels/DetailPanel/ProjectDetails.tsx
+++ b/theatre/studio/src/panels/DetailPanel/ProjectDetails.tsx
@@ -1,15 +1,19 @@
 import type Project from '@theatre/core/projects/Project'
 import getStudio from '@theatre/studio/getStudio'
-import React from 'react'
+import React, {useCallback, useState} from 'react'
 
 const ProjectDetails: React.FC<{
   projects: Project[]
 }> = ({projects}) => {
   const project = projects[0]
 
-  const exportProject = () => {
-    const str = getStudio().createExportedStateOfProject(
-      project.address.projectId,
+  const [downloaded, setDownloaded] = useState(false)
+
+  const exportProject = useCallback(() => {
+    const str = JSON.stringify(
+      getStudio().createExportedStateOfProject(project.address.projectId),
+      null,
+      2,
     )
     const file = new File([str], 'state.json', {type: 'application/json'})
     const objUrl = URL.createObjectURL(file)
@@ -17,12 +21,27 @@ const ProjectDetails: React.FC<{
     a.href = objUrl
     a.target = '_blank'
     a.setAttribute('download', 'state.json')
+    a.rel = 'noopener'
     a.click()
-  }
+
+    setDownloaded(true)
+    setTimeout(() => {
+      setDownloaded(false)
+    }, 2000)
+
+    setTimeout(() => {
+      URL.revokeObjectURL(objUrl)
+    }, 40000)
+  }, [])
 
   return (
     <div>
-      <button onClick={exportProject}>Export project</button>
+      <button
+        onClick={!downloaded ? exportProject : undefined}
+        disabled={downloaded}
+      >
+        Export project {downloaded ? 'Done' : ''}
+      </button>
     </div>
   )
 }