fix(web): threads without a project start on the primary environment (#26301)

Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>

Author: juliusmarminge

apps/web/src/components/CommandPalette.tsx

@@ -622,9 +622,7 @@ function OpenCommandPaletteDialog(props: {
   const currentProjectEnvironmentId =
     activeThread?.environmentId ?? activeDraftThread?.environmentId ?? null;
   const currentProjectId = activeThread?.projectId ?? activeDraftThread?.projectId ?? null;
-  const scratchTargetEnvironmentId = scratchEnvironmentId(
-    currentProjectEnvironmentId ?? primaryEnvironmentId,
-  );
+  const scratchTargetEnvironmentId = scratchEnvironmentId(currentProjectEnvironmentId);
   const supportsTriage = (environmentId: EnvironmentId | null) =>
     environments.find((environment) => environment.environmentId === environmentId)?.serverConfig
       ?.environment.capabilities.triage === true;

apps/web/src/components/chat/DraftHeroHeadline.tsx

@@ -143,12 +143,11 @@ export function DraftHeroHeadline({
             project.environmentId === activeProjectRef.environmentId &&
             project.id === activeProjectRef.projectId,
         ) ?? null);
-  const scratchTargetEnvironmentId = scratchEnvironmentId(
-    activeProjectRef?.environmentId ?? primaryEnvironmentId,
-  );
+  const scratchTargetEnvironmentId = scratchEnvironmentId(activeProjectRef?.environmentId ?? null);
   const scratchWorkspaceRoot = scratchWorkspaceRootFor(scratchTargetEnvironmentId);
   const isScratchDraft =
-    activeProject !== null && isScratchProject(activeProject, scratchWorkspaceRoot);
+    activeProject !== null &&
+    isScratchProject(activeProject, scratchWorkspaceRootFor(activeProject.environmentId));
 
   const pickerItems: readonly PickerItem[] = [
     ...menuEntries.map(({ group }) => ({ value: group.projectKey, label: group.displayName })),

apps/web/src/components/promptLinks/NewThreadLinkView.tsx

@@ -175,8 +175,7 @@ export function NewThreadLinkView({ link }: { readonly link: NewThreadLink }) {
   };
 
   const openScratchDraft = async () => {
-    const environmentId =
-      scratchEnvironmentId(lastActiveEnvironmentId()) ?? scratchEnvironmentId(null);
+    const environmentId = scratchEnvironmentId(lastActiveEnvironmentId());
     const project = environmentId === null ? null : await openScratchProject(environmentId);
     if (project === null) {
       setState({

apps/web/src/hooks/useScratchProject.test.ts

@@ -0,0 +1,49 @@
+import type { EnvironmentId } from "@t3tools/contracts";
+import { AtomRegistry } from "effect/reactivity";
+import { describe, expect, it } from "vite-plus/test";
+
+import { createScratchProjectActions } from "./useScratchProject";
+
+const local = "local" as EnvironmentId;
+const remote = "remote" as EnvironmentId;
+const other = "other" as EnvironmentId;
+
+function scratchEnvironment(environmentId: EnvironmentId, scratchWorkspaceRoot: string | null) {
+  return {
+    environmentId,
+    connection: { phase: "connected" },
+    serverConfig: { scratchWorkspaceRoot },
+  } as never;
+}
+
+function actions(
+  primary: EnvironmentId | null,
+  localRoot: string | null,
+  remoteRoot: string | null = "/remote/scratch",
+) {
+  const environments = [
+    scratchEnvironment(local, localRoot),
+    scratchEnvironment(remote, remoteRoot),
+    scratchEnvironment(other, "/other/scratch"),
+  ];
+  return createScratchProjectActions({
+    environments: () => environments,
+    primaryEnvironmentId: () => primary,
+    registry: AtomRegistry.make(),
+    handleNewThread: async () => null,
+  });
+}
+
+describe("scratchEnvironmentId", () => {
+  it("prefers the primary environment over the one on screen", () => {
+    expect(actions(local, "/local/scratch").scratchEnvironmentId(remote)).toBe(local);
+    expect(actions(local, "/local/scratch").scratchEnvironmentId(null)).toBe(local);
+  });
+
+  it("falls back when the primary environment offers no scratch root", () => {
+    expect(actions(local, null).scratchEnvironmentId(remote)).toBe(remote);
+    expect(actions(null, null).scratchEnvironmentId(remote)).toBe(remote);
+    expect(actions(null, null, null).scratchEnvironmentId(remote)).toBe(other);
+    expect(actions(local, null).scratchEnvironmentId(null)).toBeNull();
+  });
+});

apps/web/src/hooks/useScratchProject.ts

@@ -12,7 +12,11 @@ import type { AtomRegistry } from "effect/reactivity";
 import { useContext } from "react";
 
 import { stackedThreadToast, toastManager } from "~/components/ui/toast";
-import { type EnvironmentPresentation, useEnvironments } from "~/state/environments";
+import {
+  type EnvironmentPresentation,
+  useEnvironments,
+  usePrimaryEnvironmentId,
+} from "~/state/environments";
 import { projectEnvironment } from "~/state/projects";
 import { type NewThreadHandler, useNewThreadHandler } from "./useHandleNewThread";
 
@@ -32,6 +36,7 @@ type ScratchEnvironment = Pick<EnvironmentPresentation, "connection" | "serverCo
 
 export function createScratchProjectActions(input: {
   readonly environments: () => Iterable<ScratchEnvironment>;
+  readonly primaryEnvironmentId: () => EnvironmentId | null;
   readonly registry: AtomRegistry.AtomRegistry;
   readonly handleNewThread: NewThreadHandler;
 }) {
@@ -43,8 +48,11 @@ export function createScratchProjectActions(input: {
     return availableScratchWorkspaceRoot(environment?.connection.phase, environment?.serverConfig);
   };
 
-  const scratchEnvironmentId = (current: EnvironmentId | null): EnvironmentId | null => {
-    if (current !== null) return scratchWorkspaceRootFor(current) !== null ? current : null;
+  // The primary (local) environment wins; `fallback` only applies when it offers no scratch root.
+  const scratchEnvironmentId = (fallback: EnvironmentId | null): EnvironmentId | null => {
+    const primary = input.primaryEnvironmentId();
+    if (primary !== null && scratchWorkspaceRootFor(primary) !== null) return primary;
+    if (fallback !== null && scratchWorkspaceRootFor(fallback) !== null) return fallback;
     const offering = [...input.environments()].filter(
       (entry) => scratchWorkspaceRootFor(entry.environmentId) !== null,
     );
@@ -85,10 +93,12 @@ export function createScratchProjectActions(input: {
 
 export function useScratchProject() {
   const { environments } = useEnvironments();
+  const primaryEnvironmentId = usePrimaryEnvironmentId();
   const registry = useContext(RegistryContext);
   const handleNewThread = useNewThreadHandler();
   return createScratchProjectActions({
     environments: () => environments,
+    primaryEnvironmentId: () => primaryEnvironmentId,
     registry,
     handleNewThread,
   });

apps/web/src/shortcuts/chatRouteCommands.ts

@@ -39,6 +39,7 @@ export function installChatRouteCommands(router: AnyRouter): () => void {
       [...appAtomRegistry.get(environmentPresentations.presentationsAtom)].map(
         ([environmentId, presentation]) => ({ ...presentation, environmentId }),
       ),
+    primaryEnvironmentId: () => appAtomRegistry.get(primaryEnvironmentIdAtom),
     registry: appAtomRegistry,
     handleNewThread,
   });
@@ -109,9 +110,7 @@ export function installChatRouteCommands(router: AnyRouter): () => void {
       "chat.newWithoutProject": (event) => {
         const { activeThread, activeDraftThread } = readThreadContext();
         const environmentId = scratch.scratchEnvironmentId(
-          activeThread?.environmentId ??
-            activeDraftThread?.environmentId ??
-            appAtomRegistry.get(primaryEnvironmentIdAtom),
+          activeThread?.environmentId ?? activeDraftThread?.environmentId ?? null,
         );
         if (environmentId === null) return;
         claim(event);