Plugins belong to the project, and they load before it: the project file gained the field plugins: ["demo-plugin.js"] (default empty, no formatVersion bump), the Plugins tab's switch writes into it as an ordinary undo step (SetPluginActiveCommand) instead of into a server-wide plugins.json, and the start order is turned around - startPlugins only fetches the list of files, then editor.boot() runs and ProjectStore.load(id, prepare) hands the raw JSON through before it is deserialized, where pluginsOf(raw) reads the list and PluginManager.syncTo() activates exactly those; that is the point of the issue, because what a plugin registers has to stand there before normalizeGraph would throw it away as unknown (#126, #127), a project switch first stops what the new project does not name and then starts what it does, a file the server does not have is passed over silently, and after signing out the manager is dead so a late event cannot start anything in a torn-down session; on the server plugins.json, PluginStore::setActive, isActive, the route PUT ?r=plugins/{file} and the 403 for inactive modules are gone and GET ?r=plugins only answers {file,bytes,updatedAt}, which makes every plugin file fetchable - the consequence accepted in #117, written down in the wiki for #115 and #116; publishPlugins(root) only copies files now, the seeder switches the demo plugin on in the fixture project, and the Plugins tab carries a puzzle piece as its icon while only a plugin's own tab still goes without one (the knob and the socket are cubic curves, not arcs, which Pixi's parser draws as a spike after an L); 3 new e2e checks in module 38 and 5 new unit tests cover the project as the owner of the switch, its undo, the order, pluginsOf against crude input and an unknown file name (#119)

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

src/editor/Editor.ts

@@ -2,6 +2,7 @@ import type { Application, Ticker } from 'pixi.js';
 import type { Asset } from '../core/model/Asset';
 import { findAsset, findObjectHolder } from '../core/model/Project';
 import type { ProjectStore } from '../core/store/ProjectStore';
+import { pluginsOf } from '../core/store/projectPlugins';
 import type { FontStore } from '../core/store/FontStore';
 import type { SoundStore } from '../core/store/SoundStore';
 import type { TextureStore } from '../core/store/TextureStore';
@@ -39,7 +40,7 @@ import { resolveList } from './list/slot';
 import { AnimationEditor } from './animation/AnimationEditor';
 import { TileEditor } from './tile/TileEditor';
 import { AssetPanel } from './panels/AssetPanel';
-import { ASSET_ICON_SVG, GAME_ICON_SVG, LIST_ICON_SVG } from './panels/assetIcons';
+import { ASSET_ICON_SVG, GAME_ICON_SVG, LIST_ICON_SVG, PLUGINS_ICON_SVG } from './panels/assetIcons';
 import { HierarchyPanel } from './panels/HierarchyPanel';
 import { TilemapPanel } from './panels/TilemapPanel';
 import { Toolbar } from './panels/Toolbar';
@@ -125,10 +126,11 @@ const TAB_LABELS: Record<CentreTab, string> = {
   plugins: 'Plugins',
 };
 
-/** Icons of the fixed tabs (#176); the Plugins tab has none, as plugins have no picture of their own. */
+/** Icons of the fixed tabs (#176); a plugin's own tab has none, it brings no picture of its own. */
 const FIXED_TAB_ICONS: Partial<Record<FixedTab, string>> = {
   scene: ASSET_ICON_SVG.scene,
   game: GAME_ICON_SVG,
+  plugins: PLUGINS_ICON_SVG,
 };
 
 function isDocument(tab: StripTab): tab is DocumentId {
@@ -247,9 +249,16 @@ export class Editor implements PlayHost {
         this.viewport.setEditorWorld(world);
       },
     });
-    this.projects = new ProjectSession(state, store, () => {
-      if (this.play.isPlaying) this.play.stop();
-    });
+    this.projects = new ProjectSession(
+      state,
+      store,
+      () => {
+        if (this.play.isPlaying) this.play.stop();
+      },
+      // Every project brings its own plugins (#119); until `startPlugins` has run there is no
+      // manager, and a project with plugins simply has none of them.
+      async (raw) => void (await this.plugins?.syncTo(pluginsOf(raw))),
+    );
 
     this.graphEditor.canvas.traceProvider = (assetId) => this.play.traceFor(assetId);
     this.graphEditor.canvas.timeProvider = () => this.play.time;