diff --git a/README.md b/README.md
index 3ff36d9..5270f2f 100644
--- a/README.md
+++ b/README.md
@@ -18,13 +18,14 @@ src/
   domain/       Framework-agnostic types + logic (compatibility rules, BOM math,
                 the built-in connector/cable/device library). No React, no
                 React Flow — safe to unit test or reuse from a future backend.
-  data/         Storage abstraction. `ProjectRepository` is the interface the
-                rest of the app codes against; `LocalStorageProjectRepository`
-                is the only implementation today. Swapping in a real backend
-                later (REST/GraphQL) means adding one new implementation of
-                that interface, not touching state/UI code.
-  state/        Zustand store (`projectStore`) — the single source of truth for
-                the current project. Auto-saves to the repository (debounced)
+  data/         Storage abstraction. `DiagramRepository` is the interface the
+                rest of the app codes against; `SupabaseDiagramRepository` is
+                the active implementation, with `LocalStorageDiagramRepository`
+                kept as a reference/fallback. Swapping storage means adding
+                one new implementation of that interface, not touching
+                state/UI code.
+  state/        Zustand store (`diagramStore`) — the single source of truth for
+                the current diagram. Auto-saves to the repository (debounced)
                 on every change.
   components/
     canvas/     React Flow wiring surface: custom device node, custom cable
@@ -40,17 +41,19 @@ src/
 - **PortType** — a connector kind (HDMI, XLR, Cat5e/6, ...). Two ports can be
   wired together only if their PortTypes share a compatibility `family`.
 - **DeviceTemplate** — a reusable device shape (its ports), shown in the
-  palette. Built-ins live in `domain/library.ts`; custom ones are saved on the
-  project.
+  palette. Built-ins live in `domain/library.ts` and seed the public catalog;
+  custom ones are your own private catalog entries (or submitted for public
+  review).
 - **Device** — an instance placed on the canvas, with its own copy of ports
   (editing an instance never mutates its template).
 - **CableType** — a physical cable spec, scoped to a PortType family.
 - **Connection** — a wire between two ports, referencing a CableType and an
   optional user-entered distance (there's no floor plan / scale model, so
   length is a manual estimate per connection).
-- **Project** — devices + connections + any custom library entries. This is
-  the one object persisted (auto-saved to `localStorage`, or explicitly
-  exported/imported as JSON).
+- **Diagram** — devices + connections. This is the one object persisted
+  (auto-saved to Supabase, or explicitly exported/imported as JSON); the
+  catalog (PortType/CableType/DeviceTemplate/category) is shared and global,
+  not part of any one diagram.
 
 ## Development
 
diff --git a/src/components/bom/BomPanel.tsx b/src/components/bom/BomPanel.tsx
index bd2574d..8d97968 100644
--- a/src/components/bom/BomPanel.tsx
+++ b/src/components/bom/BomPanel.tsx
@@ -1,7 +1,7 @@
 import { Fragment, useMemo, useState } from 'react'
 import { computeBom } from '../../domain/bom'
 import { useCatalogStore } from '../../state/catalogStore'
-import { useProjectStore } from '../../state/projectStore'
+import { useDiagramStore } from '../../state/diagramStore'
 import Chevron from '../common/Chevron'
 
 function formatCost(value: number): string {
@@ -9,9 +9,9 @@ function formatCost(value: number): string {
 }
 
 export default function BomPanel() {
-  const project = useProjectStore((s) => s.project)
+  const diagram = useDiagramStore((s) => s.diagram)
   const catalog = useCatalogStore((s) => s.catalog)
-  const bom = useMemo(() => computeBom(project, catalog), [project, catalog])
+  const bom = useMemo(() => computeBom(diagram, catalog), [diagram, catalog])
   // Collapsed by default, per cable type — most diagrams only need the
   // per-type totals; the length breakdown is there when you're ready to
   // actually go buy cables.
diff --git a/src/components/canvas/FlowCanvas.tsx b/src/components/canvas/FlowCanvas.tsx
index 6732138..5883508 100644
--- a/src/components/canvas/FlowCanvas.tsx
+++ b/src/components/canvas/FlowCanvas.tsx
@@ -15,9 +15,9 @@ import {
 import '@xyflow/react/dist/style.css'
 import { useCallback, useMemo } from 'react'
 import { validateConnection } from '../../domain/compatibility'
-import { allCableTypes, allPortTypes, cableTypesForConnection, deviceCategoryName, getPortType } from '../../domain/project'
+import { allCableTypes, allPortTypes, cableTypesForConnection, deviceCategoryName, getPortType } from '../../domain/diagram'
 import { useCatalogStore } from '../../state/catalogStore'
-import { useProjectStore } from '../../state/projectStore'
+import { useDiagramStore } from '../../state/diagramStore'
 import CableEdge, { type CableFlowEdge } from './CableEdge'
 import DeviceNode, { type DeviceFlowNode, type PortInfo } from './DeviceNode'
 import { buildHandleId, parsePortId } from './handleIds'
@@ -28,19 +28,19 @@ const nodeTypes: NodeTypes = { device: DeviceNode }
 const edgeTypes: EdgeTypes = { cable: CableEdge }
 
 function FlowCanvasInner() {
-  const project = useProjectStore((s) => s.project)
-  const selectedDeviceId = useProjectStore((s) => s.selectedDeviceId)
-  const selectedConnectionId = useProjectStore((s) => s.selectedConnectionId)
-  const updateDevicePosition = useProjectStore((s) => s.updateDevicePosition)
-  const removeDevice = useProjectStore((s) => s.removeDevice)
-  const removeConnection = useProjectStore((s) => s.removeConnection)
-  const addConnection = useProjectStore((s) => s.addConnection)
-  const addDeviceFromTemplate = useProjectStore((s) => s.addDeviceFromTemplate)
-  const selectDevice = useProjectStore((s) => s.selectDevice)
-  const selectConnection = useProjectStore((s) => s.selectConnection)
+  const diagram = useDiagramStore((s) => s.diagram)
+  const selectedDeviceId = useDiagramStore((s) => s.selectedDeviceId)
+  const selectedConnectionId = useDiagramStore((s) => s.selectedConnectionId)
+  const updateDevicePosition = useDiagramStore((s) => s.updateDevicePosition)
+  const removeDevice = useDiagramStore((s) => s.removeDevice)
+  const removeConnection = useDiagramStore((s) => s.removeConnection)
+  const addConnection = useDiagramStore((s) => s.addConnection)
+  const addDeviceFromTemplate = useDiagramStore((s) => s.addDeviceFromTemplate)
+  const selectDevice = useDiagramStore((s) => s.selectDevice)
+  const selectConnection = useDiagramStore((s) => s.selectConnection)
   const { screenToFlowPosition } = useReactFlow()
   const catalog = useCatalogStore((s) => s.catalog)
-  const access = useProjectStore((s) => s.access)
+  const access = useDiagramStore((s) => s.access)
   // Owner/edit-collaborator/(a Super Admin, who getAccess always reports as
   // 'edit') can edit; a view-only collaborator can look but not touch —
   // organized-ideas.md §8's per-collaborator permissions. `access` is only
@@ -53,10 +53,10 @@ function FlowCanvasInner() {
 
   const nodes: DeviceFlowNode[] = useMemo(
     () =>
-      project.devices.map((device) => {
+      diagram.devices.map((device) => {
         const portInfos: PortInfo[] = device.ports.map((port) => {
           const portType = portTypes.find((pt) => pt.id === port.portTypeId)
-          const connectionCount = project.connections.filter(
+          const connectionCount = diagram.connections.filter(
             (c) => c.sourcePortId === port.id || c.targetPortId === port.id,
           ).length
           const max = portType?.maxConnections ?? 1
@@ -70,12 +70,12 @@ function FlowCanvasInner() {
           data: { device, categoryName: deviceCategoryName(catalog, device.category), portInfos },
         }
       }),
-    [project, catalog, portTypes, selectedDeviceId],
+    [diagram, catalog, portTypes, selectedDeviceId],
   )
 
   const edges: CableFlowEdge[] = useMemo(
     () =>
-      project.connections.map((connection) => {
+      diagram.connections.map((connection) => {
         const cableType = cableTypes.find((ct) => ct.id === connection.cableTypeId)
         return {
           id: connection.id,
@@ -92,7 +92,7 @@ function FlowCanvasInner() {
           },
         }
       }),
-    [project.connections, cableTypes, selectedConnectionId],
+    [diagram.connections, cableTypes, selectedConnectionId],
   )
 
   const isValidConnection = useCallback(
@@ -101,14 +101,14 @@ function FlowCanvasInner() {
       const sourcePortId = parsePortId(c.sourceHandle)
       const targetPortId = parsePortId(c.targetHandle)
       if (!canEdit || !c.source || !c.target || !sourcePortId || !targetPortId) return false
-      return validateConnection(project, catalog, {
+      return validateConnection(diagram, catalog, {
         sourceDeviceId: c.source,
         sourcePortId,
         targetDeviceId: c.target,
         targetPortId,
       }).valid
     },
-    [project, catalog, canEdit],
+    [diagram, catalog, canEdit],
   )
 
   const onConnect = useCallback(
@@ -117,8 +117,8 @@ function FlowCanvasInner() {
       const sourcePortId = parsePortId(connection.sourceHandle)
       const targetPortId = parsePortId(connection.targetHandle)
       if (!connection.source || !connection.target || !sourcePortId || !targetPortId) return
-      const sourceDevice = project.devices.find((d) => d.id === connection.source)
-      const targetDevice = project.devices.find((d) => d.id === connection.target)
+      const sourceDevice = diagram.devices.find((d) => d.id === connection.source)
+      const targetDevice = diagram.devices.find((d) => d.id === connection.target)
       const sourcePort = sourceDevice?.ports.find((p) => p.id === sourcePortId)
       const targetPort = targetDevice?.ports.find((p) => p.id === targetPortId)
       const sourcePortType = sourcePort && getPortType(catalog, sourcePort.portTypeId)
@@ -134,7 +134,7 @@ function FlowCanvasInner() {
         cableTypeId: defaultCableType.id,
       })
     },
-    [project, catalog, canEdit, addConnection],
+    [diagram, catalog, canEdit, addConnection],
   )
 
   const onNodesChange = useCallback(
diff --git a/src/components/common/CategorySelect.tsx b/src/components/common/CategorySelect.tsx
index 1bcd5bd..f1560b3 100644
--- a/src/components/common/CategorySelect.tsx
+++ b/src/components/common/CategorySelect.tsx
@@ -1,5 +1,5 @@
 import { useMemo, useState } from 'react'
-import { allDeviceCategories } from '../../domain/project'
+import { allDeviceCategories } from '../../domain/diagram'
 import { useCatalogStore } from '../../state/catalogStore'
 
 const NEW_CATEGORY_VALUE = '__new__'
diff --git a/src/components/inspector/ConnectionInspector.tsx b/src/components/inspector/ConnectionInspector.tsx
index a717ea8..a111688 100644
--- a/src/components/inspector/ConnectionInspector.tsx
+++ b/src/components/inspector/ConnectionInspector.tsx
@@ -1,19 +1,19 @@
 import { useMemo } from 'react'
-import { cableTypesForConnection, getPortType } from '../../domain/project'
+import { cableTypesForConnection, getPortType } from '../../domain/diagram'
 import { useCatalogStore } from '../../state/catalogStore'
-import { useProjectStore } from '../../state/projectStore'
+import { useDiagramStore } from '../../state/diagramStore'
 
 export default function ConnectionInspector({ connectionId }: { connectionId: string }) {
-  const project = useProjectStore((s) => s.project)
+  const diagram = useDiagramStore((s) => s.diagram)
   const catalog = useCatalogStore((s) => s.catalog)
-  const access = useProjectStore((s) => s.access)
+  const access = useDiagramStore((s) => s.access)
   const canEdit = access?.myPermission !== 'view'
-  const updateConnection = useProjectStore((s) => s.updateConnection)
-  const removeConnection = useProjectStore((s) => s.removeConnection)
+  const updateConnection = useDiagramStore((s) => s.updateConnection)
+  const removeConnection = useDiagramStore((s) => s.removeConnection)
 
-  const connection = project.connections.find((c) => c.id === connectionId)
-  const sourceDevice = project.devices.find((d) => d.id === connection?.sourceDeviceId)
-  const targetDevice = project.devices.find((d) => d.id === connection?.targetDeviceId)
+  const connection = diagram.connections.find((c) => c.id === connectionId)
+  const sourceDevice = diagram.devices.find((d) => d.id === connection?.sourceDeviceId)
+  const targetDevice = diagram.devices.find((d) => d.id === connection?.targetDeviceId)
   const sourcePort = sourceDevice?.ports.find((p) => p.id === connection?.sourcePortId)
   const targetPort = targetDevice?.ports.find((p) => p.id === connection?.targetPortId)
 
diff --git a/src/components/inspector/DeviceInspector.tsx b/src/components/inspector/DeviceInspector.tsx
index c38ff61..6452611 100644
--- a/src/components/inspector/DeviceInspector.tsx
+++ b/src/components/inspector/DeviceInspector.tsx
@@ -1,25 +1,25 @@
 import { useMemo, useState } from 'react'
 import { PORT_DIRECTIONS } from '../../domain/constants'
-import { allPortTypes } from '../../domain/project'
+import { allPortTypes } from '../../domain/diagram'
 import type { PortDirection } from '../../domain/types'
 import { useCatalogStore } from '../../state/catalogStore'
-import { useProjectStore } from '../../state/projectStore'
+import { useDiagramStore } from '../../state/diagramStore'
 import CategorySelect from '../common/CategorySelect'
 
 export default function DeviceInspector({ deviceId }: { deviceId: string }) {
-  const project = useProjectStore((s) => s.project)
+  const diagram = useDiagramStore((s) => s.diagram)
   const catalog = useCatalogStore((s) => s.catalog)
-  const access = useProjectStore((s) => s.access)
+  const access = useDiagramStore((s) => s.access)
   const canEdit = access?.myPermission !== 'view'
-  const updateDevice = useProjectStore((s) => s.updateDevice)
-  const removeDevice = useProjectStore((s) => s.removeDevice)
-  const addPort = useProjectStore((s) => s.addPort)
-  const clonePort = useProjectStore((s) => s.clonePort)
-  const updatePort = useProjectStore((s) => s.updatePort)
-  const removePort = useProjectStore((s) => s.removePort)
+  const updateDevice = useDiagramStore((s) => s.updateDevice)
+  const removeDevice = useDiagramStore((s) => s.removeDevice)
+  const addPort = useDiagramStore((s) => s.addPort)
+  const clonePort = useDiagramStore((s) => s.clonePort)
+  const updatePort = useDiagramStore((s) => s.updatePort)
+  const removePort = useDiagramStore((s) => s.removePort)
   const [focusPortId, setFocusPortId] = useState<string | null>(null)
 
-  const device = project.devices.find((d) => d.id === deviceId)
+  const device = diagram.devices.find((d) => d.id === deviceId)
   const portTypes = useMemo(
     () => [...allPortTypes(catalog)].sort((a, b) => a.name.localeCompare(b.name)),
     [catalog],
@@ -28,7 +28,7 @@ export default function DeviceInspector({ deviceId }: { deviceId: string }) {
   if (!device) return null
 
   const connectionCountForPort = (portId: string) =>
-    project.connections.filter((c) => c.sourcePortId === portId || c.targetPortId === portId).length
+    diagram.connections.filter((c) => c.sourcePortId === portId || c.targetPortId === portId).length
 
   return (
     <fieldset disabled={!canEdit} className="m-0 space-y-3 border-0 p-3">
diff --git a/src/components/layout/AppShell.tsx b/src/components/layout/AppShell.tsx
index 8136213..3ad5f88 100644
--- a/src/components/layout/AppShell.tsx
+++ b/src/components/layout/AppShell.tsx
@@ -2,7 +2,7 @@ import { useEffect } from 'react'
 import { useAdminReviewStore } from '../../state/adminReviewStore'
 import { useAuthStore } from '../../state/authStore'
 import { useCatalogStore } from '../../state/catalogStore'
-import { useProjectStore } from '../../state/projectStore'
+import { useDiagramStore } from '../../state/diagramStore'
 import { useSubmissionStore } from '../../state/submissionStore'
 import FlowCanvas from '../canvas/FlowCanvas'
 import DevicePalette from '../palette/DevicePalette'
@@ -12,8 +12,8 @@ import TopBar from './TopBar'
 import ViewOnlyBanner from './ViewOnlyBanner'
 
 export default function AppShell() {
-  const isLoaded = useProjectStore((s) => s.isLoaded)
-  const loadInitialDiagram = useProjectStore((s) => s.loadInitialDiagram)
+  const isLoaded = useDiagramStore((s) => s.isLoaded)
+  const loadInitialDiagram = useDiagramStore((s) => s.loadInitialDiagram)
   const isCatalogLoaded = useCatalogStore((s) => s.isLoaded)
   const loadCatalog = useCatalogStore((s) => s.loadCatalog)
   const loadMySubmissions = useSubmissionStore((s) => s.loadMySubmissions)
diff --git a/src/components/layout/ConnectionErrorBanner.tsx b/src/components/layout/ConnectionErrorBanner.tsx
index 73559f8..c591fbb 100644
--- a/src/components/layout/ConnectionErrorBanner.tsx
+++ b/src/components/layout/ConnectionErrorBanner.tsx
@@ -1,9 +1,9 @@
 import { useEffect } from 'react'
-import { useProjectStore } from '../../state/projectStore'
+import { useDiagramStore } from '../../state/diagramStore'
 
 export default function ConnectionErrorBanner() {
-  const error = useProjectStore((s) => s.lastConnectionError)
-  const clear = useProjectStore((s) => s.clearConnectionError)
+  const error = useDiagramStore((s) => s.lastConnectionError)
+  const clear = useDiagramStore((s) => s.clearConnectionError)
 
   useEffect(() => {
     if (!error) return
diff --git a/src/components/layout/DiagramManagerModal.tsx b/src/components/layout/DiagramManagerModal.tsx
index 5c1a6b0..a274a9d 100644
--- a/src/components/layout/DiagramManagerModal.tsx
+++ b/src/components/layout/DiagramManagerModal.tsx
@@ -1,5 +1,5 @@
 import { useEffect } from 'react'
-import { useProjectStore } from '../../state/projectStore'
+import { useDiagramStore } from '../../state/diagramStore'
 import Modal from '../common/Modal'
 
 function formatUpdatedAt(iso: string): string {
@@ -8,25 +8,25 @@ function formatUpdatedAt(iso: string): string {
 }
 
 export default function DiagramManagerModal({ onClose }: { onClose: () => void }) {
-  const project = useProjectStore((s) => s.project)
-  const diagramList = useProjectStore((s) => s.diagramList)
-  const refreshDiagramList = useProjectStore((s) => s.refreshDiagramList)
-  const newProject = useProjectStore((s) => s.newProject)
-  const switchToDiagram = useProjectStore((s) => s.switchToDiagram)
-  const deleteDiagram = useProjectStore((s) => s.deleteDiagram)
+  const diagram = useDiagramStore((s) => s.diagram)
+  const diagramList = useDiagramStore((s) => s.diagramList)
+  const refreshDiagramList = useDiagramStore((s) => s.refreshDiagramList)
+  const newDiagram = useDiagramStore((s) => s.newDiagram)
+  const switchToDiagram = useDiagramStore((s) => s.switchToDiagram)
+  const deleteDiagram = useDiagramStore((s) => s.deleteDiagram)
 
   useEffect(() => {
     refreshDiagramList()
   }, [refreshDiagramList])
 
   const handleOpen = async (id: string) => {
-    if (id === project.id) return
+    if (id === diagram.id) return
     await switchToDiagram(id)
     onClose()
   }
 
   const handleNew = async () => {
-    await newProject()
+    await newDiagram()
     onClose()
   }
 
@@ -52,7 +52,7 @@ export default function DiagramManagerModal({ onClose }: { onClose: () => void }
 
         <ul className="space-y-1">
           {diagramList.map((d) => {
-            const isCurrent = d.id === project.id
+            const isCurrent = d.id === diagram.id
             return (
               <li
                 key={d.id}
diff --git a/src/components/layout/RightPanel.tsx b/src/components/layout/RightPanel.tsx
index 04b39e8..d4a8eb9 100644
--- a/src/components/layout/RightPanel.tsx
+++ b/src/components/layout/RightPanel.tsx
@@ -2,13 +2,13 @@ import { useState } from 'react'
 import BomPanel from '../bom/BomPanel'
 import ConnectionInspector from '../inspector/ConnectionInspector'
 import DeviceInspector from '../inspector/DeviceInspector'
-import { useProjectStore } from '../../state/projectStore'
+import { useDiagramStore } from '../../state/diagramStore'
 
 type Tab = 'inspector' | 'bom'
 
 export default function RightPanel() {
-  const selectedDeviceId = useProjectStore((s) => s.selectedDeviceId)
-  const selectedConnectionId = useProjectStore((s) => s.selectedConnectionId)
+  const selectedDeviceId = useDiagramStore((s) => s.selectedDeviceId)
+  const selectedConnectionId = useDiagramStore((s) => s.selectedConnectionId)
   const [tab, setTab] = useState<Tab>('inspector')
 
   return (
diff --git a/src/components/layout/TopBar.tsx b/src/components/layout/TopBar.tsx
index 5b0877b..79d8a58 100644
--- a/src/components/layout/TopBar.tsx
+++ b/src/components/layout/TopBar.tsx
@@ -1,9 +1,9 @@
 import { useMemo, useRef, useState } from 'react'
-import { downloadProjectFile, readProjectFile, ProjectImportError } from '../../data/exportImport'
+import { downloadDiagramFile, readDiagramFile, DiagramImportError } from '../../data/exportImport'
 import { supabase } from '../../data/supabaseClient'
 import { useAdminReviewStore } from '../../state/adminReviewStore'
 import { useAuthStore } from '../../state/authStore'
-import { useProjectStore } from '../../state/projectStore'
+import { useDiagramStore } from '../../state/diagramStore'
 import { useSubmissionStore } from '../../state/submissionStore'
 import AdminUsersModal from '../admin/AdminUsersModal'
 import DiagramSharingModal from '../sharing/DiagramSharingModal'
@@ -33,11 +33,11 @@ function setLastSeenSubmissionsAt(iso: string): void {
 }
 
 export default function TopBar() {
-  const project = useProjectStore((s) => s.project)
-  const access = useProjectStore((s) => s.access)
+  const diagram = useDiagramStore((s) => s.diagram)
+  const access = useDiagramStore((s) => s.access)
   const canEdit = access?.myPermission !== 'view'
-  const renameProject = useProjectStore((s) => s.renameProject)
-  const importProject = useProjectStore((s) => s.importProject)
+  const renameDiagram = useDiagramStore((s) => s.renameDiagram)
+  const importDiagram = useDiagramStore((s) => s.importDiagram)
   const mySubmissions = useSubmissionStore((s) => s.mySubmissions)
   const username = useAuthStore((s) => s.username)
   const role = useAuthStore((s) => s.role)
@@ -66,7 +66,7 @@ export default function TopBar() {
     setLastSeenSubmissionsAt(new Date().toISOString())
   }
 
-  const handleExport = () => downloadProjectFile(project)
+  const handleExport = () => downloadDiagramFile(diagram)
 
   const handleImportClick = () => fileInputRef.current?.click()
 
@@ -75,10 +75,10 @@ export default function TopBar() {
     event.target.value = ''
     if (!file) return
     try {
-      const imported = await readProjectFile(file)
-      await importProject(imported)
+      const imported = await readDiagramFile(file)
+      await importDiagram(imported)
     } catch (err) {
-      const message = err instanceof ProjectImportError ? err.message : 'Could not read that file.'
+      const message = err instanceof DiagramImportError ? err.message : 'Could not read that file.'
       window.alert(`Import failed: ${message}`)
     }
   }
@@ -88,8 +88,8 @@ export default function TopBar() {
       <div className="flex items-center gap-2">
         <span className="text-sm font-semibold text-indigo-700">AV Planner</span>
         <input
-          value={project.name}
-          onChange={(e) => renameProject(e.target.value)}
+          value={diagram.name}
+          onChange={(e) => renameDiagram(e.target.value)}
           disabled={!canEdit}
           className="rounded border border-transparent px-2 py-1 text-sm text-slate-700 hover:border-slate-200 focus:border-slate-300 focus:outline-none disabled:cursor-not-allowed disabled:opacity-60"
         />
diff --git a/src/components/layout/ViewOnlyBanner.tsx b/src/components/layout/ViewOnlyBanner.tsx
index d7f8132..f3a0ce7 100644
--- a/src/components/layout/ViewOnlyBanner.tsx
+++ b/src/components/layout/ViewOnlyBanner.tsx
@@ -1,4 +1,4 @@
-import { useProjectStore } from '../../state/projectStore'
+import { useDiagramStore } from '../../state/diagramStore'
 
 /** Shown when the current user only has view access to the open diagram
  *  (organized-ideas.md §8's per-collaborator permissions) — the canvas and
@@ -6,7 +6,7 @@ import { useProjectStore } from '../../state/projectStore'
  *  FlowCanvas/DeviceInspector/ConnectionInspector), this just makes that
  *  visible instead of leaving it to be discovered by a control not working. */
 export default function ViewOnlyBanner() {
-  const access = useProjectStore((s) => s.access)
+  const access = useDiagramStore((s) => s.access)
   if (access?.myPermission !== 'view') return null
 
   return (
diff --git a/src/components/palette/CableTypeManager.tsx b/src/components/palette/CableTypeManager.tsx
index b39bfc8..7113bef 100644
--- a/src/components/palette/CableTypeManager.tsx
+++ b/src/components/palette/CableTypeManager.tsx
@@ -1,5 +1,5 @@
 import { useMemo, useState } from 'react'
-import { allCableTypes, allPortTypes } from '../../domain/project'
+import { allCableTypes, allPortTypes } from '../../domain/diagram'
 import type { CableType, PortType } from '../../domain/types'
 import { cableTypeToRow } from '../../data/catalogRowMapping'
 import { useAdminReviewStore } from '../../state/adminReviewStore'
diff --git a/src/components/palette/DevicePalette.tsx b/src/components/palette/DevicePalette.tsx
index a1272bf..cf6b679 100644
--- a/src/components/palette/DevicePalette.tsx
+++ b/src/components/palette/DevicePalette.tsx
@@ -1,11 +1,11 @@
 import { useMemo, useState } from 'react'
 import { deviceTemplateToRow } from '../../data/catalogRowMapping'
-import { allDeviceCategories, allDeviceTemplates, hiddenDeviceTemplates } from '../../domain/project'
+import { allDeviceCategories, allDeviceTemplates, hiddenDeviceTemplates } from '../../domain/diagram'
 import type { DeviceTemplate } from '../../domain/types'
 import { useAdminReviewStore } from '../../state/adminReviewStore'
 import { useAuthStore } from '../../state/authStore'
 import { useCatalogStore } from '../../state/catalogStore'
-import { useProjectStore } from '../../state/projectStore'
+import { useDiagramStore } from '../../state/diagramStore'
 import { useSubmissionStore } from '../../state/submissionStore'
 import { TEMPLATE_DRAG_MIME } from '../canvas/FlowCanvas'
 import Chevron from '../common/Chevron'
@@ -19,10 +19,10 @@ type EditorTarget =
   | { mode: 'adminEdit'; template: DeviceTemplate }
 
 export default function DevicePalette() {
-  const project = useProjectStore((s) => s.project)
-  const access = useProjectStore((s) => s.access)
+  const diagram = useDiagramStore((s) => s.diagram)
+  const access = useDiagramStore((s) => s.access)
   const canEdit = access?.myPermission !== 'view'
-  const addDeviceFromTemplate = useProjectStore((s) => s.addDeviceFromTemplate)
+  const addDeviceFromTemplate = useDiagramStore((s) => s.addDeviceFromTemplate)
   const catalog = useCatalogStore((s) => s.catalog)
   const hiddenPublicIds = useCatalogStore((s) => s.hiddenPublicDeviceTemplateIds)
   const removeCustomDeviceTemplate = useCatalogStore((s) => s.removeCustomDeviceTemplate)
@@ -81,7 +81,7 @@ export default function DevicePalette() {
   const handleQuickAdd = (template: DeviceTemplate) => {
     if (!canEdit) return
     // Cascade placement so repeated quick-adds don't stack exactly on top of each other.
-    const offset = (project.devices.length % 8) * 24
+    const offset = (diagram.devices.length % 8) * 24
     addDeviceFromTemplate(catalog, template.id, { x: 80 + offset, y: 80 + offset })
   }
 
diff --git a/src/components/palette/DeviceTemplateEditor.tsx b/src/components/palette/DeviceTemplateEditor.tsx
index 5ecb5f5..13450e6 100644
--- a/src/components/palette/DeviceTemplateEditor.tsx
+++ b/src/components/palette/DeviceTemplateEditor.tsx
@@ -1,7 +1,7 @@
 import { useMemo, useState } from 'react'
 import { deviceTemplateToRow } from '../../data/catalogRowMapping'
 import { PORT_CATEGORIES, PORT_DIRECTIONS } from '../../domain/constants'
-import { allPortTypes, expandCompatibleFamilyIds, incrementPortName } from '../../domain/project'
+import { allPortTypes, expandCompatibleFamilyIds, incrementPortName } from '../../domain/diagram'
 import type { DeviceTemplate, PortDirection } from '../../domain/types'
 import { useCatalogStore } from '../../state/catalogStore'
 import { useSubmissionStore } from '../../state/submissionStore'
diff --git a/src/components/palette/PortTypeManager.tsx b/src/components/palette/PortTypeManager.tsx
index 6ae6a36..34adfb1 100644
--- a/src/components/palette/PortTypeManager.tsx
+++ b/src/components/palette/PortTypeManager.tsx
@@ -1,6 +1,6 @@
 import { useMemo, useState } from 'react'
 import { PORT_CATEGORIES } from '../../domain/constants'
-import { allPortTypes, expandCompatibleFamilyIds } from '../../domain/project'
+import { allPortTypes, expandCompatibleFamilyIds } from '../../domain/diagram'
 import type { PortType } from '../../domain/types'
 import { portTypeToRow } from '../../data/catalogRowMapping'
 import { useAdminReviewStore } from '../../state/adminReviewStore'
diff --git a/src/components/sharing/DiagramSharingModal.tsx b/src/components/sharing/DiagramSharingModal.tsx
index fca58be..31f24ba 100644
--- a/src/components/sharing/DiagramSharingModal.tsx
+++ b/src/components/sharing/DiagramSharingModal.tsx
@@ -2,14 +2,14 @@ import { useEffect, useState } from 'react'
 import type { CollaboratorPermission } from '../../data/DiagramCollaboratorRepository'
 import { SelfCollaboratorError, UnknownUsernameError } from '../../data/DiagramCollaboratorRepository'
 import { useDiagramCollaboratorStore } from '../../state/diagramCollaboratorStore'
-import { useProjectStore } from '../../state/projectStore'
+import { useDiagramStore } from '../../state/diagramStore'
 import Modal from '../common/Modal'
 
 export default function DiagramSharingModal({ onClose }: { onClose: () => void }) {
-  const project = useProjectStore((s) => s.project)
-  const access = useProjectStore((s) => s.access)
+  const diagram = useDiagramStore((s) => s.diagram)
+  const access = useDiagramStore((s) => s.access)
   const isOwner = access?.myPermission === 'owner'
-  const diagramId = project.id
+  const diagramId = diagram.id
 
   const collaborators = useDiagramCollaboratorStore((s) => s.collaborators)
   const isLoaded = useDiagramCollaboratorStore((s) => s.isLoaded)
@@ -52,7 +52,7 @@ export default function DiagramSharingModal({ onClose }: { onClose: () => void }
   }
 
   return (
-    <Modal title={`Share "${project.name}"`} onClose={onClose} width="max-w-md">
+    <Modal title={`Share "${diagram.name}"`} onClose={onClose} width="max-w-md">
       <div className="space-y-3">
         {isOwner && (
           <div className="space-y-1.5 rounded border border-slate-200 bg-slate-50 p-2">
diff --git a/src/components/sharing/VersionHistoryModal.tsx b/src/components/sharing/VersionHistoryModal.tsx
index 92fa2f4..1f79253 100644
--- a/src/components/sharing/VersionHistoryModal.tsx
+++ b/src/components/sharing/VersionHistoryModal.tsx
@@ -1,6 +1,6 @@
 import { useEffect, useState } from 'react'
 import { useDiagramSnapshotStore } from '../../state/diagramSnapshotStore'
-import { useProjectStore } from '../../state/projectStore'
+import { useDiagramStore } from '../../state/diagramStore'
 import Modal from '../common/Modal'
 
 function formatDateTime(iso: string): string {
@@ -8,10 +8,10 @@ function formatDateTime(iso: string): string {
 }
 
 export default function VersionHistoryModal({ onClose }: { onClose: () => void }) {
-  const project = useProjectStore((s) => s.project)
-  const access = useProjectStore((s) => s.access)
+  const diagram = useDiagramStore((s) => s.diagram)
+  const access = useDiagramStore((s) => s.access)
   const canRestore = access?.myPermission === 'owner' || access?.myPermission === 'edit'
-  const diagramId = project.id
+  const diagramId = diagram.id
 
   const snapshots = useDiagramSnapshotStore((s) => s.snapshots)
   const isLoaded = useDiagramSnapshotStore((s) => s.isLoaded)
@@ -37,7 +37,7 @@ export default function VersionHistoryModal({ onClose }: { onClose: () => void }
   }
 
   return (
-    <Modal title={`Version History — "${project.name}"`} onClose={onClose} width="max-w-md">
+    <Modal title={`Version History — "${diagram.name}"`} onClose={onClose} width="max-w-md">
       <div className="space-y-1.5">
         <p className="text-[11px] text-slate-500">
           Checkpoints saved periodically while editing (up to the 50 most recent).
diff --git a/src/components/submissions/MySubmissionsModal.tsx b/src/components/submissions/MySubmissionsModal.tsx
index f100d45..0d921ec 100644
--- a/src/components/submissions/MySubmissionsModal.tsx
+++ b/src/components/submissions/MySubmissionsModal.tsx
@@ -1,7 +1,7 @@
 import { useState } from 'react'
 import { cableTypeToRow, portTypeToRow, rowToCableTypeFields, rowToDeviceTemplateFields, rowToPortTypeFields } from '../../data/catalogRowMapping'
 import type { CatalogSubmission } from '../../data/SubmissionRepository'
-import { allPortTypes } from '../../domain/project'
+import { allPortTypes } from '../../domain/diagram'
 import type { CableType, Catalog, DeviceTemplate, PortType } from '../../domain/types'
 import { useCatalogStore } from '../../state/catalogStore'
 import { useSubmissionStore } from '../../state/submissionStore'
diff --git a/src/data/DiagramRepository.ts b/src/data/DiagramRepository.ts
index eb15cbe..7115ce5 100644
--- a/src/data/DiagramRepository.ts
+++ b/src/data/DiagramRepository.ts
@@ -1,4 +1,4 @@
-import type { Project } from '../domain/types'
+import type { Diagram } from '../domain/types'
 
 /** Lightweight metadata for listing diagrams without fetching each one's
  *  full (potentially large) data payload. */
@@ -8,17 +8,6 @@ export interface DiagramSummary {
   updatedAt: string
 }
 
-/**
- * Storage abstraction the rest of the app codes against. `LocalStorageDiagramRepository`
- * and `SupabaseDiagramRepository` both implement it — the store/UI layers don't need to
- * know or care which one is active.
- *
- * Named for the "Diagram" terminology decided in organized-ideas.md §8 (renamed from
- * "Project"). This is a deliberately scoped rename: only the storage layer's naming
- * changed here. The domain type (`Project`), the Zustand store (`useProjectStore`), and
- * user-facing copy still say "Project" — that's a separate, larger mechanical rename
- * across the whole app, tracked as its own task rather than bundled into this one.
- */
 /** Your relationship to a diagram — who owns it, and what you personally
  *  can do with it (organized-ideas.md §8's per-collaborator view/edit
  *  permissions). Drives the frontend's own view-only lockdown, since RLS
@@ -29,13 +18,18 @@ export interface DiagramAccess {
   myPermission: 'owner' | 'edit' | 'view'
 }
 
+/**
+ * Storage abstraction the rest of the app codes against. `LocalStorageDiagramRepository`
+ * and `SupabaseDiagramRepository` both implement it — the store/UI layers don't need to
+ * know or care which one is active.
+ */
 export interface DiagramRepository {
   /** Every diagram visible to the current user, most recently updated first. */
   list(): Promise<DiagramSummary[]>
   /** One diagram's full data by id, or null if it doesn't exist / isn't visible. */
-  loadById(id: string): Promise<Project | null>
-  /** Upsert a diagram, matched by the project's own id. */
-  save(project: Project): Promise<void>
+  loadById(id: string): Promise<Diagram | null>
+  /** Upsert a diagram, matched by its own id. */
+  save(diagram: Diagram): Promise<void>
   /** Permanently delete one diagram by id. */
   deleteById(id: string): Promise<void>
   /** Who owns this diagram and what the current user can do with it. */
diff --git a/src/data/DiagramSnapshotRepository.ts b/src/data/DiagramSnapshotRepository.ts
index a7997dc..b25000a 100644
--- a/src/data/DiagramSnapshotRepository.ts
+++ b/src/data/DiagramSnapshotRepository.ts
@@ -1,4 +1,4 @@
-import type { Project } from '../domain/types'
+import type { Diagram } from '../domain/types'
 
 export interface DiagramSnapshotSummary {
   id: string
@@ -20,7 +20,7 @@ export interface DiagramSnapshotRepository {
    *  it already knows the live state is an unmodified copy of a snapshot
    *  that still exists (e.g. restoring again right after an earlier
    *  restore, with no edits in between), so a second copy of it would just
-   *  be a duplicate. Returns the restored Project so the caller can update
+   *  be a duplicate. Returns the restored Diagram so the caller can update
    *  the open diagram in place. */
-  restore(diagramId: string, snapshotId: string, writeSafetySnapshot: boolean): Promise<Project | null>
+  restore(diagramId: string, snapshotId: string, writeSafetySnapshot: boolean): Promise<Diagram | null>
 }
diff --git a/src/data/LocalStorageDiagramRepository.ts b/src/data/LocalStorageDiagramRepository.ts
index 7ba5fc1..9b24a17 100644
--- a/src/data/LocalStorageDiagramRepository.ts
+++ b/src/data/LocalStorageDiagramRepository.ts
@@ -1,10 +1,10 @@
-import type { Project } from '../domain/types'
+import type { Diagram } from '../domain/types'
 import type { DiagramAccess, DiagramRepository, DiagramSummary } from './DiagramRepository'
-import { normalizeProject } from './exportImport'
+import { normalizeDiagram } from './exportImport'
 
 const STORAGE_KEY = 'av-planner:diagrams:v1'
 
-type StoredDiagrams = Record<string, Project>
+type StoredDiagrams = Record<string, Diagram>
 
 function readAll(): StoredDiagrams {
   try {
@@ -20,10 +20,11 @@ function writeAll(diagrams: StoredDiagrams): void {
   window.localStorage.setItem(STORAGE_KEY, JSON.stringify(diagrams))
 }
 
-/** Kept around (no longer the active repository — see projectStore.ts) as a
- *  reference implementation and a safe fallback if Supabase is unreachable.
- *  Multiple diagrams are stored as one JSON object keyed by id, matching the
- *  shape the Supabase-backed repository presents to the rest of the app. */
+/** Kept around (no longer the active repository — see state/diagramStore.ts)
+ *  as a reference implementation and a safe fallback if Supabase is
+ *  unreachable. Multiple diagrams are stored as one JSON object keyed by
+ *  id, matching the shape the Supabase-backed repository presents to the
+ *  rest of the app. */
 export class LocalStorageDiagramRepository implements DiagramRepository {
   async list(): Promise<DiagramSummary[]> {
     const diagrams = Object.values(readAll())
@@ -32,14 +33,14 @@ export class LocalStorageDiagramRepository implements DiagramRepository {
       .sort((a, b) => b.updatedAt.localeCompare(a.updatedAt))
   }
 
-  async loadById(id: string): Promise<Project | null> {
+  async loadById(id: string): Promise<Diagram | null> {
     const diagram = readAll()[id]
-    return diagram ? normalizeProject(diagram) : null
+    return diagram ? normalizeDiagram(diagram) : null
   }
 
-  async save(project: Project): Promise<void> {
+  async save(diagram: Diagram): Promise<void> {
     const all = readAll()
-    all[project.id] = project
+    all[diagram.id] = diagram
     writeAll(all)
   }
 
diff --git a/src/data/SupabaseDiagramRepository.ts b/src/data/SupabaseDiagramRepository.ts
index 2e73646..1606427 100644
--- a/src/data/SupabaseDiagramRepository.ts
+++ b/src/data/SupabaseDiagramRepository.ts
@@ -1,11 +1,11 @@
-import type { Project } from '../domain/types'
+import type { Diagram } from '../domain/types'
 import type { DiagramAccess, DiagramRepository, DiagramSummary } from './DiagramRepository'
-import { normalizeProject } from './exportImport'
+import { normalizeDiagram } from './exportImport'
 import { supabase } from './supabaseClient'
 
 /**
  * Backs the app with the local (or eventually production) Supabase
- * `diagrams` table instead of localStorage. The whole `Project` domain
+ * `diagrams` table instead of localStorage. The whole `Diagram` domain
  * object is stored as-is in the `data` JSONB column — see the schema
  * migration's header comment for why diagrams are a document, not
  * normalized relational rows.
@@ -27,7 +27,7 @@ export class SupabaseDiagramRepository implements DiagramRepository {
     return (data ?? []).map((row) => ({ id: row.id, name: row.name, updatedAt: row.updated_at }))
   }
 
-  async loadById(id: string): Promise<Project | null> {
+  async loadById(id: string): Promise<Diagram | null> {
     const { data: row, error } = await supabase.from('diagrams').select('data').eq('id', id).maybeSingle()
 
     if (error) {
@@ -35,10 +35,10 @@ export class SupabaseDiagramRepository implements DiagramRepository {
       return null
     }
     if (!row) return null
-    return normalizeProject(row.data as Project)
+    return normalizeDiagram(row.data as Diagram)
   }
 
-  async save(project: Project): Promise<void> {
+  async save(diagram: Diagram): Promise<void> {
     const {
       data: { user },
     } = await supabase.auth.getUser()
@@ -52,15 +52,15 @@ export class SupabaseDiagramRepository implements DiagramRepository {
     // to whoever saves last — once diagram sharing (§8) is in play, an
     // edit-collaborator saving changes must never be able to overwrite who
     // owns the diagram.
-    const { data: existing } = await supabase.from('diagrams').select('id, data').eq('id', project.id).maybeSingle()
+    const { data: existing } = await supabase.from('diagrams').select('id, data').eq('id', diagram.id).maybeSingle()
     if (existing) {
-      await this.maybeWriteSnapshot(project.id, existing.data as Project, user.id)
+      await this.maybeWriteSnapshot(diagram.id, existing.data as Diagram, user.id)
     }
-    const payload = { name: project.name, data: project, updated_at: new Date().toISOString() }
+    const payload = { name: diagram.name, data: diagram, updated_at: new Date().toISOString() }
 
     const { error } = existing
-      ? await supabase.from('diagrams').update(payload).eq('id', project.id)
-      : await supabase.from('diagrams').insert({ id: project.id, owner_id: user.id, ...payload })
+      ? await supabase.from('diagrams').update(payload).eq('id', diagram.id)
+      : await supabase.from('diagrams').insert({ id: diagram.id, owner_id: user.id, ...payload })
 
     if (error) {
       console.error('Failed to save diagram to Supabase', error)
@@ -73,7 +73,7 @@ export class SupabaseDiagramRepository implements DiagramRepository {
   // keystroke-adjacent change instead of meaningful recovery points.
   private static readonly SNAPSHOT_INTERVAL_MS = 5 * 60 * 1000
 
-  private async maybeWriteSnapshot(diagramId: string, previousData: Project, userId: string): Promise<void> {
+  private async maybeWriteSnapshot(diagramId: string, previousData: Diagram, userId: string): Promise<void> {
     const { data: lastSnapshot } = await supabase
       .from('diagram_snapshots')
       .select('created_at')
diff --git a/src/data/SupabaseDiagramSnapshotRepository.ts b/src/data/SupabaseDiagramSnapshotRepository.ts
index 2fb0120..7dd05c0 100644
--- a/src/data/SupabaseDiagramSnapshotRepository.ts
+++ b/src/data/SupabaseDiagramSnapshotRepository.ts
@@ -1,6 +1,6 @@
-import type { Project } from '../domain/types'
+import type { Diagram } from '../domain/types'
 import type { DiagramSnapshotRepository, DiagramSnapshotSummary } from './DiagramSnapshotRepository'
-import { normalizeProject } from './exportImport'
+import { normalizeDiagram } from './exportImport'
 import { supabase } from './supabaseClient'
 
 interface SnapshotRow {
@@ -36,7 +36,7 @@ export class SupabaseDiagramSnapshotRepository implements DiagramSnapshotReposit
     }))
   }
 
-  async restore(diagramId: string, snapshotId: string, writeSafetySnapshot: boolean): Promise<Project | null> {
+  async restore(diagramId: string, snapshotId: string, writeSafetySnapshot: boolean): Promise<Diagram | null> {
     const { data: snapshot, error } = await supabase.from('diagram_snapshots').select('data').eq('id', snapshotId).maybeSingle()
     if (error) console.error('Failed to load snapshot from Supabase', error)
     if (!snapshot) return null
@@ -59,7 +59,7 @@ export class SupabaseDiagramSnapshotRepository implements DiagramSnapshotReposit
       }
     }
 
-    const restored = normalizeProject(snapshot.data as Project)
+    const restored = normalizeDiagram(snapshot.data as Diagram)
     const { error: updateError } = await supabase
       .from('diagrams')
       .update({ data: restored, name: restored.name, updated_at: new Date().toISOString() })
diff --git a/src/data/exportImport.ts b/src/data/exportImport.ts
index d95b554..5e96fce 100644
--- a/src/data/exportImport.ts
+++ b/src/data/exportImport.ts
@@ -1,15 +1,15 @@
-import type { Project } from '../domain/types'
+import type { Diagram } from '../domain/types'
 
-export function projectToJson(project: Project): string {
-  return JSON.stringify(project, null, 2)
+export function diagramToJson(diagram: Diagram): string {
+  return JSON.stringify(diagram, null, 2)
 }
 
-export function downloadProjectFile(project: Project): void {
-  const json = projectToJson(project)
+export function downloadDiagramFile(diagram: Diagram): void {
+  const json = diagramToJson(diagram)
   const blob = new Blob([json], { type: 'application/json' })
   const url = URL.createObjectURL(blob)
   const a = document.createElement('a')
-  const safeName = project.name.trim().replace(/[^a-z0-9-_]+/gi, '_') || 'project'
+  const safeName = diagram.name.trim().replace(/[^a-z0-9-_]+/gi, '_') || 'diagram'
   a.href = url
   a.download = `${safeName}.avplan.json`
   document.body.appendChild(a)
@@ -18,44 +18,44 @@ export function downloadProjectFile(project: Project): void {
   URL.revokeObjectURL(url)
 }
 
-class ProjectImportError extends Error {}
+class DiagramImportError extends Error {}
 
 /** Minimal structural check — enough to catch "wrong file" without pulling
  *  in a schema validation library for a single call site. */
-function assertLooksLikeProject(value: unknown): asserts value is Project {
+function assertLooksLikeDiagram(value: unknown): asserts value is Diagram {
   if (typeof value !== 'object' || value === null) {
-    throw new ProjectImportError('File does not contain a JSON object.')
+    throw new DiagramImportError('File does not contain a JSON object.')
   }
-  const p = value as Partial<Project>
-  if (typeof p.id !== 'string' || typeof p.name !== 'string') {
-    throw new ProjectImportError('File is missing required project fields.')
+  const d = value as Partial<Diagram>
+  if (typeof d.id !== 'string' || typeof d.name !== 'string') {
+    throw new DiagramImportError('File is missing required diagram fields.')
   }
-  if (!Array.isArray(p.devices) || !Array.isArray(p.connections)) {
-    throw new ProjectImportError('File is missing devices/connections arrays.')
+  if (!Array.isArray(d.devices) || !Array.isArray(d.connections)) {
+    throw new DiagramImportError('File is missing devices/connections arrays.')
   }
 }
 
-export async function readProjectFile(file: File): Promise<Project> {
+export async function readDiagramFile(file: File): Promise<Diagram> {
   const text = await file.text()
   let parsed: unknown
   try {
     parsed = JSON.parse(text)
   } catch {
-    throw new ProjectImportError('File is not valid JSON.')
+    throw new DiagramImportError('File is not valid JSON.')
   }
-  assertLooksLikeProject(parsed)
-  return normalizeProject(parsed)
+  assertLooksLikeDiagram(parsed)
+  return normalizeDiagram(parsed)
 }
 
-/** Strips any legacy per-project catalog fields (customDeviceTemplates,
+/** Strips any legacy per-diagram catalog fields (customDeviceTemplates,
  *  customPortTypes, etc.) that might still be present in an older export
  *  file or a localStorage diagram saved before the catalog moved to
  *  Supabase (see state/catalogStore.ts) — that data now lives in the shared
  *  catalog, not the diagram, so it's just discarded here rather than
  *  crashing on an unexpected shape. */
-export function normalizeProject(project: Project): Project {
-  const { id, name, createdAt, updatedAt, devices, connections } = project
+export function normalizeDiagram(diagram: Diagram): Diagram {
+  const { id, name, createdAt, updatedAt, devices, connections } = diagram
   return { id, name, createdAt, updatedAt, devices, connections }
 }
 
-export { ProjectImportError }
+export { DiagramImportError }
diff --git a/src/domain/bom.ts b/src/domain/bom.ts
index 6bb1b39..f69aa57 100644
--- a/src/domain/bom.ts
+++ b/src/domain/bom.ts
@@ -1,5 +1,5 @@
-import { allCableTypes } from './project'
-import type { CableType, Catalog, Connection, Device, Project } from './types'
+import { allCableTypes } from './diagram'
+import type { CableType, Catalog, Connection, Device, Diagram } from './types'
 
 /** One length within a cable type's group — e.g. "3 × 10ft". `distance`
  *  is undefined for the bucket of connections that have no length entered
@@ -82,7 +82,7 @@ function connectionCost(connection: Connection, cableType: CableType | undefined
   return undefined
 }
 
-export function computeBom(project: Project, catalog: Catalog): Bom {
+export function computeBom(diagram: Diagram, catalog: Catalog): Bom {
   const cableTypes = new Map(allCableTypes(catalog).map((ct) => [ct.id, ct]))
 
   const cableLines = new Map<string, BomCableLine>()
@@ -92,7 +92,7 @@ export function computeBom(project: Project, catalog: Catalog): Bom {
   // addressable by (cableTypeId, distance) while building them up.
   const lengthLines = new Map<string, Map<number | undefined, BomCableLengthLine>>()
 
-  for (const connection of project.connections) {
+  for (const connection of diagram.connections) {
     const cableType = cableTypes.get(connection.cableTypeId)
     const name = cableType?.name ?? 'Unknown Cable'
     const unit = cableType?.unit ?? 'ft'
@@ -155,7 +155,7 @@ export function computeBom(project: Project, catalog: Catalog): Bom {
   }
 
   const deviceLines = new Map<string, BomDeviceLine>()
-  for (const device of project.devices) {
+  for (const device of diagram.devices) {
     const key = deviceGroupKey(device)
     const existing = deviceLines.get(key) ?? {
       key,
diff --git a/src/domain/compatibility.ts b/src/domain/compatibility.ts
index 4725df7..aaeda98 100644
--- a/src/domain/compatibility.ts
+++ b/src/domain/compatibility.ts
@@ -1,5 +1,5 @@
-import { acceptedFamilies, getPortType, hasBridgingCableType } from './project'
-import type { Catalog, Connection, Device, PortType, Project } from './types'
+import { acceptedFamilies, getPortType, hasBridgingCableType } from './diagram'
+import type { Catalog, Connection, Device, Diagram, PortType } from './types'
 
 /**
  * Two ports connect if the sets of families they each accept (their own
@@ -36,10 +36,10 @@ export interface ConnectionValidation {
  * server-side later since it only depends on plain domain data.
  */
 export function validateConnection(
-  project: Project,
+  diagram: Diagram,
   catalog: Catalog,
   candidate: ConnectionCandidate,
-  existingConnections: Connection[] = project.connections,
+  existingConnections: Connection[] = diagram.connections,
 ): ConnectionValidation {
   const { sourceDeviceId, sourcePortId, targetDeviceId, targetPortId } = candidate
 
@@ -47,8 +47,8 @@ export function validateConnection(
     return { valid: false, reason: 'A port cannot connect to itself.' }
   }
 
-  const sourceDevice = project.devices.find((d) => d.id === sourceDeviceId)
-  const targetDevice = project.devices.find((d) => d.id === targetDeviceId)
+  const sourceDevice = diagram.devices.find((d) => d.id === sourceDeviceId)
+  const targetDevice = diagram.devices.find((d) => d.id === targetDeviceId)
   const sourcePort = sourceDevice?.ports.find((p) => p.id === sourcePortId)
   const targetPort = targetDevice?.ports.find((p) => p.id === targetPortId)
 
diff --git a/src/domain/constants.ts b/src/domain/constants.ts
index 7e58d13..a06a3cd 100644
--- a/src/domain/constants.ts
+++ b/src/domain/constants.ts
@@ -1,7 +1,7 @@
 import type { PortCategory, PortDirection } from './types'
 
-// Device categories are no longer a fixed list — see `domain/project.ts`'s
-// `allDeviceCategories` (built-ins + project-custom, merged).
+// Device categories are no longer a fixed list — see `domain/diagram.ts`'s
+// `allDeviceCategories` (public catalog + your own private ones, merged).
 
 export const PORT_DIRECTIONS: { value: PortDirection; label: string }[] = [
   { value: 'input', label: 'Input' },
diff --git a/src/domain/project.ts b/src/domain/diagram.ts
similarity index 97%
rename from src/domain/project.ts
rename to src/domain/diagram.ts
index 5ee9fe7..f9b4df4 100644
--- a/src/domain/project.ts
+++ b/src/domain/diagram.ts
@@ -1,5 +1,5 @@
 import { v4 as uuid } from 'uuid'
-import type { CableType, Catalog, Device, DeviceCategoryDef, DeviceTemplate, PortType, Project } from './types'
+import type { CableType, Catalog, Device, DeviceCategoryDef, Diagram, DeviceTemplate, PortType } from './types'
 
 export function allPortTypes(catalog: Catalog): PortType[] {
   return catalog.portTypes
@@ -125,7 +125,7 @@ export function expandCompatibleFamilyIds(selectedPortTypeIds: string[], allType
   return [...families]
 }
 
-export function createEmptyProject(name = 'Untitled Project'): Project {
+export function createEmptyDiagram(name = 'Untitled Diagram'): Diagram {
   const now = new Date().toISOString()
   return {
     id: uuid(),
diff --git a/src/domain/types.ts b/src/domain/types.ts
index a331b90..e50a94a 100644
--- a/src/domain/types.ts
+++ b/src/domain/types.ts
@@ -16,11 +16,12 @@ export type PortCategory =
   | 'other'
 
 /** A device category id (references a DeviceCategoryDef). Kept as a plain
- *  string rather than a fixed union so projects can define their own. */
+ *  string rather than a fixed union so users can define their own. */
 export type DeviceCategory = string
 
 /** A device grouping shown in the palette and category pickers. Built-ins
- *  ship in `library.ts`; users can add their own, scoped to the project. */
+ *  ship in `library.ts`; users can add their own private ones via the
+ *  shared catalog (see state/catalogStore.ts), not scoped to any one diagram. */
 export interface DeviceCategoryDef {
   id: string
   name: string
@@ -134,7 +135,7 @@ export interface Connection {
   notes?: string
 }
 
-export interface Project {
+export interface Diagram {
   id: string
   name: string
   createdAt: string
diff --git a/src/state/catalogStore.ts b/src/state/catalogStore.ts
index 6d188e2..8b25951 100644
--- a/src/state/catalogStore.ts
+++ b/src/state/catalogStore.ts
@@ -10,7 +10,7 @@ const repository: CatalogRepository = new SupabaseCatalogRepository()
 
 // Which public device templates you've hidden from your own palette — a
 // per-user UI preference, not catalog data, so it's not a Supabase row: hiding
-// a public entry only affects your view of it (see domain/project.ts's
+// a public entry only affects your view of it (see domain/diagram.ts's
 // allDeviceTemplates/hiddenDeviceTemplates), never the shared entry itself.
 const HIDDEN_PUBLIC_TEMPLATES_KEY = 'av-planner:hiddenPublicDeviceTemplateIds'
 function loadHiddenPublicIds(): Set<string> {
diff --git a/src/state/diagramSnapshotStore.ts b/src/state/diagramSnapshotStore.ts
index 3ff7d0e..37670db 100644
--- a/src/state/diagramSnapshotStore.ts
+++ b/src/state/diagramSnapshotStore.ts
@@ -1,8 +1,8 @@
 import { create } from 'zustand'
 import type { DiagramSnapshotRepository, DiagramSnapshotSummary } from '../data/DiagramSnapshotRepository'
 import { SupabaseDiagramSnapshotRepository } from '../data/SupabaseDiagramSnapshotRepository'
-import type { Project } from '../domain/types'
-import { useProjectStore } from './projectStore'
+import type { Diagram } from '../domain/types'
+import { useDiagramStore } from './diagramStore'
 
 const repository: DiagramSnapshotRepository = new SupabaseDiagramSnapshotRepository()
 
@@ -12,12 +12,12 @@ interface DiagramSnapshotStoreState {
 
   load: (diagramId: string) => Promise<void>
   /** Restores a snapshot and applies it to the open diagram (via
-   *  projectStore.applyRestoredProject) in one step. Skips writing a
+   *  diagramStore.applyRestoredDiagram) in one step. Skips writing a
    *  pointless duplicate safety snapshot when the live diagram is already
    *  an unmodified copy of a snapshot still sitting in the list — see
-   *  projectStore's restoredFromSnapshotId/restoredProjectUpdatedAt.
-   *  Returns the restored Project, or null if the restore failed. */
-  restore: (diagramId: string, snapshotId: string) => Promise<Project | null>
+   *  diagramStore's restoredFromSnapshotId/restoredDiagramUpdatedAt.
+   *  Returns the restored Diagram, or null if the restore failed. */
+  restore: (diagramId: string, snapshotId: string) => Promise<Diagram | null>
 }
 
 export const useDiagramSnapshotStore = create<DiagramSnapshotStoreState>((set) => ({
@@ -30,13 +30,13 @@ export const useDiagramSnapshotStore = create<DiagramSnapshotStoreState>((set) =
   },
 
   restore: async (diagramId, snapshotId) => {
-    const { project, restoredFromSnapshotId, restoredProjectUpdatedAt } = useProjectStore.getState()
+    const { diagram, restoredFromSnapshotId, restoredDiagramUpdatedAt } = useDiagramStore.getState()
     const knownUnmodifiedSinceLastRestore =
-      restoredFromSnapshotId !== null && project.updatedAt === restoredProjectUpdatedAt
+      restoredFromSnapshotId !== null && diagram.updatedAt === restoredDiagramUpdatedAt
 
     const restored = await repository.restore(diagramId, snapshotId, !knownUnmodifiedSinceLastRestore)
     if (restored) {
-      useProjectStore.getState().applyRestoredProject(restored, snapshotId)
+      useDiagramStore.getState().applyRestoredDiagram(restored, snapshotId)
       const snapshots = await repository.list(diagramId)
       set({ snapshots })
     }
diff --git a/src/state/projectStore.ts b/src/state/diagramStore.ts
similarity index 75%
rename from src/state/projectStore.ts
rename to src/state/diagramStore.ts
index 1186e06..e4a7194 100644
--- a/src/state/projectStore.ts
+++ b/src/state/diagramStore.ts
@@ -1,8 +1,8 @@
 import { v4 as uuid } from 'uuid'
 import { create } from 'zustand'
 import { validateConnection } from '../domain/compatibility'
-import { allDeviceTemplates, createDeviceFromTemplate, createEmptyProject, incrementPortName } from '../domain/project'
-import type { Catalog, Connection, Device, DeviceCategory, Port, Project } from '../domain/types'
+import { allDeviceTemplates, createDeviceFromTemplate, createEmptyDiagram, incrementPortName } from '../domain/diagram'
+import type { Catalog, Connection, Device, DeviceCategory, Diagram, Port } from '../domain/types'
 import type { DiagramAccess, DiagramRepository, DiagramSummary } from '../data/DiagramRepository'
 import { SupabaseDiagramRepository } from '../data/SupabaseDiagramRepository'
 
@@ -34,14 +34,14 @@ function setLastDiagramId(id: string): void {
   }
 }
 
-async function loadMostRecent(): Promise<Project | null> {
+async function loadMostRecent(): Promise<Diagram | null> {
   const list = await repository.list()
   if (list.length === 0) return null
   return repository.loadById(list[0].id)
 }
 
-interface ProjectStoreState {
-  project: Project
+interface DiagramStoreState {
+  diagram: Diagram
   isLoaded: boolean
   /** Every diagram the current user can see, most recently updated first.
    *  Populated by refreshDiagramList — not kept live-synced on every store
@@ -57,8 +57,8 @@ interface ProjectStoreState {
   access: DiagramAccess | null
   /** Set to a snapshot's id right after restoring it, meaning the live
    *  diagram data is verbatim identical to that already-existing snapshot
-   *  row — see applyRestoredProject. `restoredProjectUpdatedAt` is the
-   *  project's own `updatedAt` at that moment; touch() always advances
+   *  row — see applyRestoredDiagram. `restoredDiagramUpdatedAt` is the
+   *  diagram's own `updatedAt` at that moment; touch() always advances
    *  `updatedAt` on a genuine edit, so comparing the two later is a free
    *  way to tell "has anything changed since this restore" without
    *  hooking every mutating action. Both null once anything invalidates
@@ -67,7 +67,7 @@ interface ProjectStoreState {
    *  snapshot when the user restores several old versions in a row without
    *  editing in between. */
   restoredFromSnapshotId: string | null
-  restoredProjectUpdatedAt: string | null
+  restoredDiagramUpdatedAt: string | null
   selectedDeviceId: string | null
   selectedConnectionId: string | null
   lastConnectionError: string | null
@@ -79,17 +79,17 @@ interface ProjectStoreState {
   refreshDiagramList: () => Promise<void>
   /** Creates a new diagram, makes it current, and persists it immediately
    *  (not just via the debounced autosave) so it shows up in the list right away. */
-  newProject: (name?: string) => Promise<void>
-  renameProject: (name: string) => void
+  newDiagram: (name?: string) => Promise<void>
+  renameDiagram: (name: string) => void
   /** Imports diagram data under a fresh id, so it's added as a new diagram
    *  rather than risking a collision with (or silently overwriting) an
    *  existing one that happens to share the file's id. */
-  importProject: (project: Project) => Promise<void>
+  importDiagram: (diagram: Diagram) => Promise<void>
   /** Applies a diagram that was already persisted by something else (the
    *  version-history "Restore" action already wrote the restored data to
    *  Supabase) — just reflects it in the currently open canvas, without
    *  re-triggering an import-style "treat this as a brand new diagram". */
-  applyRestoredProject: (project: Project, snapshotId: string) => void
+  applyRestoredDiagram: (diagram: Diagram, snapshotId: string) => void
   /** Switches the active diagram to another one of the user's own. */
   switchToDiagram: (id: string) => Promise<void>
   /** Permanently deletes a diagram. If it's the currently open one, falls
@@ -132,17 +132,17 @@ interface ProjectStoreState {
   removeConnection: (id: string) => void
 }
 
-function touch(project: Project): Project {
-  return { ...project, updatedAt: new Date().toISOString() }
+function touch(diagram: Diagram): Diagram {
+  return { ...diagram, updatedAt: new Date().toISOString() }
 }
 
-export const useProjectStore = create<ProjectStoreState>((set, get) => ({
-  project: createEmptyProject(),
+export const useDiagramStore = create<DiagramStoreState>((set, get) => ({
+  diagram: createEmptyDiagram(),
   isLoaded: false,
   diagramList: [],
   access: null,
   restoredFromSnapshotId: null,
-  restoredProjectUpdatedAt: null,
+  restoredDiagramUpdatedAt: null,
   selectedDeviceId: null,
   selectedConnectionId: null,
   lastConnectionError: null,
@@ -151,10 +151,10 @@ export const useProjectStore = create<ProjectStoreState>((set, get) => ({
   loadInitialDiagram: async () => {
     const lastId = getLastDiagramId()
     const loaded = lastId ? await repository.loadById(lastId) : null
-    const project = loaded ?? (await loadMostRecent()) ?? createEmptyProject()
-    setLastDiagramId(project.id)
-    const access = await repository.getAccess(project.id)
-    set({ project, access, isLoaded: true, restoredFromSnapshotId: null, restoredProjectUpdatedAt: null })
+    const diagram = loaded ?? (await loadMostRecent()) ?? createEmptyDiagram()
+    setLastDiagramId(diagram.id)
+    const access = await repository.getAccess(diagram.id)
+    set({ diagram, access, isLoaded: true, restoredFromSnapshotId: null, restoredDiagramUpdatedAt: null })
     get().refreshDiagramList()
   },
 
@@ -163,45 +163,45 @@ export const useProjectStore = create<ProjectStoreState>((set, get) => ({
     set({ diagramList })
   },
 
-  newProject: async (name = 'Untitled Project') => {
-    const project = createEmptyProject(name)
-    setLastDiagramId(project.id)
+  newDiagram: async (name = 'Untitled Diagram') => {
+    const diagram = createEmptyDiagram(name)
+    setLastDiagramId(diagram.id)
     set({
-      project,
+      diagram,
       selectedDeviceId: null,
       selectedConnectionId: null,
       restoredFromSnapshotId: null,
-      restoredProjectUpdatedAt: null,
+      restoredDiagramUpdatedAt: null,
     })
-    await repository.save(project)
-    const access = await repository.getAccess(project.id)
+    await repository.save(diagram)
+    const access = await repository.getAccess(diagram.id)
     set({ access })
     get().refreshDiagramList()
   },
 
-  renameProject: (name) => {
-    set((state) => ({ project: touch({ ...state.project, name }) }))
+  renameDiagram: (name) => {
+    set((state) => ({ diagram: touch({ ...state.diagram, name }) }))
   },
 
-  applyRestoredProject: (project, snapshotId) => {
+  applyRestoredDiagram: (diagram, snapshotId) => {
     set({
-      project,
+      diagram,
       selectedDeviceId: null,
       selectedConnectionId: null,
       restoredFromSnapshotId: snapshotId,
-      restoredProjectUpdatedAt: project.updatedAt,
+      restoredDiagramUpdatedAt: diagram.updatedAt,
     })
   },
 
-  importProject: async (project) => {
-    const fresh = touch({ ...project, id: uuid() })
+  importDiagram: async (diagram) => {
+    const fresh = touch({ ...diagram, id: uuid() })
     setLastDiagramId(fresh.id)
     set({
-      project: fresh,
+      diagram: fresh,
       selectedDeviceId: null,
       selectedConnectionId: null,
       restoredFromSnapshotId: null,
-      restoredProjectUpdatedAt: null,
+      restoredDiagramUpdatedAt: null,
     })
     await repository.save(fresh)
     const access = await repository.getAccess(fresh.id)
@@ -210,34 +210,34 @@ export const useProjectStore = create<ProjectStoreState>((set, get) => ({
   },
 
   switchToDiagram: async (id) => {
-    if (id === get().project.id) return
+    if (id === get().diagram.id) return
     const loaded = await repository.loadById(id)
     if (!loaded) return
     setLastDiagramId(loaded.id)
     const access = await repository.getAccess(loaded.id)
     set({
-      project: loaded,
+      diagram: loaded,
       access,
       selectedDeviceId: null,
       selectedConnectionId: null,
       restoredFromSnapshotId: null,
-      restoredProjectUpdatedAt: null,
+      restoredDiagramUpdatedAt: null,
     })
   },
 
   deleteDiagram: async (id) => {
     await repository.deleteById(id)
-    if (get().project.id === id) {
-      const next = (await loadMostRecent()) ?? createEmptyProject()
+    if (get().diagram.id === id) {
+      const next = (await loadMostRecent()) ?? createEmptyDiagram()
       setLastDiagramId(next.id)
       const access = await repository.getAccess(next.id)
       set({
-        project: next,
+        diagram: next,
         access,
         selectedDeviceId: null,
         selectedConnectionId: null,
         restoredFromSnapshotId: null,
-        restoredProjectUpdatedAt: null,
+        restoredDiagramUpdatedAt: null,
       })
     }
     get().refreshDiagramList()
@@ -247,37 +247,37 @@ export const useProjectStore = create<ProjectStoreState>((set, get) => ({
   selectConnection: (id) => set({ selectedConnectionId: id, selectedDeviceId: null }),
 
   addDeviceFromTemplate: (catalog, templateId, position) => {
-    const { project } = get()
+    const { diagram } = get()
     const template = allDeviceTemplates(catalog).find((t) => t.id === templateId)
     if (!template) return
     const device = createDeviceFromTemplate(template, position)
-    set({ project: touch({ ...project, devices: [...project.devices, device] }), selectedDeviceId: device.id })
+    set({ diagram: touch({ ...diagram, devices: [...diagram.devices, device] }), selectedDeviceId: device.id })
   },
 
   updateDevicePosition: (id, position) => {
     set((state) => ({
-      project: touch({
-        ...state.project,
-        devices: state.project.devices.map((d) => (d.id === id ? { ...d, position } : d)),
+      diagram: touch({
+        ...state.diagram,
+        devices: state.diagram.devices.map((d) => (d.id === id ? { ...d, position } : d)),
       }),
     }))
   },
 
   updateDevice: (id, patch) => {
     set((state) => ({
-      project: touch({
-        ...state.project,
-        devices: state.project.devices.map((d) => (d.id === id ? { ...d, ...patch } : d)),
+      diagram: touch({
+        ...state.diagram,
+        devices: state.diagram.devices.map((d) => (d.id === id ? { ...d, ...patch } : d)),
       }),
     }))
   },
 
   removeDevice: (id) => {
     set((state) => ({
-      project: touch({
-        ...state.project,
-        devices: state.project.devices.filter((d) => d.id !== id),
-        connections: state.project.connections.filter(
+      diagram: touch({
+        ...state.diagram,
+        devices: state.diagram.devices.filter((d) => d.id !== id),
+        connections: state.diagram.connections.filter(
           (c) => c.sourceDeviceId !== id && c.targetDeviceId !== id,
         ),
       }),
@@ -288,9 +288,9 @@ export const useProjectStore = create<ProjectStoreState>((set, get) => ({
   addPort: (deviceId, port) => {
     const newId = uuid()
     set((state) => ({
-      project: touch({
-        ...state.project,
-        devices: state.project.devices.map((d) =>
+      diagram: touch({
+        ...state.diagram,
+        devices: state.diagram.devices.map((d) =>
           d.id === deviceId ? { ...d, ports: [...d.ports, { ...port, id: newId }] } : d,
         ),
       }),
@@ -300,9 +300,9 @@ export const useProjectStore = create<ProjectStoreState>((set, get) => ({
 
   updatePort: (deviceId, portId, patch) => {
     set((state) => ({
-      project: touch({
-        ...state.project,
-        devices: state.project.devices.map((d) =>
+      diagram: touch({
+        ...state.diagram,
+        devices: state.diagram.devices.map((d) =>
           d.id === deviceId
             ? { ...d, ports: d.ports.map((p) => (p.id === portId ? { ...p, ...patch } : p)) }
             : d,
@@ -314,9 +314,9 @@ export const useProjectStore = create<ProjectStoreState>((set, get) => ({
   clonePort: (deviceId, portId) => {
     const newId = uuid()
     set((state) => ({
-      project: touch({
-        ...state.project,
-        devices: state.project.devices.map((d) => {
+      diagram: touch({
+        ...state.diagram,
+        devices: state.diagram.devices.map((d) => {
           if (d.id !== deviceId) return d
           const index = d.ports.findIndex((p) => p.id === portId)
           if (index === -1) return d
@@ -331,12 +331,12 @@ export const useProjectStore = create<ProjectStoreState>((set, get) => ({
 
   removePort: (deviceId, portId) => {
     set((state) => ({
-      project: touch({
-        ...state.project,
-        devices: state.project.devices.map((d) =>
+      diagram: touch({
+        ...state.diagram,
+        devices: state.diagram.devices.map((d) =>
           d.id === deviceId ? { ...d, ports: d.ports.filter((p) => p.id !== portId) } : d,
         ),
-        connections: state.project.connections.filter(
+        connections: state.diagram.connections.filter(
           (c) => c.sourcePortId !== portId && c.targetPortId !== portId,
         ),
       }),
@@ -344,8 +344,8 @@ export const useProjectStore = create<ProjectStoreState>((set, get) => ({
   },
 
   addConnection: (catalog, { sourceDeviceId, sourcePortId, targetDeviceId, targetPortId, cableTypeId }) => {
-    const { project } = get()
-    const validation = validateConnection(project, catalog, {
+    const { diagram } = get()
+    const validation = validateConnection(diagram, catalog, {
       sourceDeviceId,
       sourcePortId,
       targetDeviceId,
@@ -364,7 +364,7 @@ export const useProjectStore = create<ProjectStoreState>((set, get) => ({
       cableTypeId,
     }
     set({
-      project: touch({ ...project, connections: [...project.connections, connection] }),
+      diagram: touch({ ...diagram, connections: [...diagram.connections, connection] }),
       lastConnectionError: null,
       selectedConnectionId: connection.id,
       selectedDeviceId: null,
@@ -374,18 +374,18 @@ export const useProjectStore = create<ProjectStoreState>((set, get) => ({
 
   updateConnection: (id, patch) => {
     set((state) => ({
-      project: touch({
-        ...state.project,
-        connections: state.project.connections.map((c) => (c.id === id ? { ...c, ...patch } : c)),
+      diagram: touch({
+        ...state.diagram,
+        connections: state.diagram.connections.map((c) => (c.id === id ? { ...c, ...patch } : c)),
       }),
     }))
   },
 
   removeConnection: (id) => {
     set((state) => ({
-      project: touch({
-        ...state.project,
-        connections: state.project.connections.filter((c) => c.id !== id),
+      diagram: touch({
+        ...state.diagram,
+        connections: state.diagram.connections.filter((c) => c.id !== id),
       }),
       selectedConnectionId: state.selectedConnectionId === id ? null : state.selectedConnectionId,
     }))
@@ -393,22 +393,22 @@ export const useProjectStore = create<ProjectStoreState>((set, get) => ({
 
 }))
 
-// Debounced autosave: fires whenever `project` changes (skipped until the
+// Debounced autosave: fires whenever `diagram` changes (skipped until the
 // initial load completes, so we don't immediately overwrite storage with a
-// blank project on first mount).
+// blank diagram on first mount).
 let saveTimeout: ReturnType<typeof setTimeout> | undefined
-useProjectStore.subscribe((state, prevState) => {
+useDiagramStore.subscribe((state, prevState) => {
   // Skip the isLoaded:false -> true transition itself (that's the initial
-  // load, not a user edit) and any tick where `project` didn't change.
+  // load, not a user edit) and any tick where `diagram` didn't change.
   if (!prevState.isLoaded) return
-  if (state.project === prevState.project) return
+  if (state.diagram === prevState.diagram) return
   // Defense in depth: the UI shouldn't expose any mutating control to a
   // view-only collaborator in the first place (see FlowCanvas/inspectors),
   // but skip the write here too rather than relying on RLS's silent no-op.
   if (state.access?.myPermission === 'view') return
   if (saveTimeout) clearTimeout(saveTimeout)
   saveTimeout = setTimeout(() => {
-    repository.save(state.project).catch((err) => console.error('Autosave failed', err))
+    repository.save(state.diagram).catch((err) => console.error('Autosave failed', err))
   }, 400)
 })
 
diff --git a/supabase/migrations/20260910010000_admin_review_queue.sql b/supabase/migrations/20260910010000_admin_review_queue.sql
index e25ad2f..4c863f6 100644
--- a/supabase/migrations/20260910010000_admin_review_queue.sql
+++ b/supabase/migrations/20260910010000_admin_review_queue.sql
@@ -26,7 +26,7 @@ create policy "catalog_submissions_insert" on public.catalog_submissions for ins
 -- ----------------------------------------------------------------------
 -- Usage-impact aggregate function.
 --
--- A diagram's `data` JSONB mirrors the exported Project shape (see
+-- A diagram's `data` JSONB mirrors the exported Diagram shape (see
 -- data/exportImport.ts / domain/types.ts): devices[].templateId,
 -- devices[].category, devices[].ports[].portTypeId, and
 -- connections[].cableTypeId are the four places a catalog entity id can be