Preserve sidebar section when creating a thread in an environment

apps/app/src/components/secondary-panel/ThreadMetadataContent.tsx

@@ -241,6 +241,7 @@ export function EnvironmentRow({
   const createThreadInEnvironment = useCreateThreadInEnvironment({
     projectId: thread.projectId,
     environmentId: environment?.id ?? "",
+    sectionId: thread.sectionId,
   });
   const { providers } = useSystemEnvironmentProviders();
   const { providers: machineProviders } = useSystemMachineProviders();

apps/app/src/components/sidebar/ProjectRow.tsx

@@ -1064,6 +1064,7 @@ const EnvironmentThreadGroupRow = memo(function EnvironmentThreadGroupRow({
   const createThreadInEnvironment = useCreateThreadInEnvironment({
     projectId,
     environmentId,
+    sectionId: representativeThread.sectionId,
   });
   const threads = useMemo(() => nodes.map((node) => node.thread), [nodes]);
   const { archiveThreadsPending, onArchiveThreads } =

apps/app/src/hooks/useCreateThreadInEnvironment.test.ts

@@ -4,6 +4,7 @@ import { renderHook } from "@testing-library/react";
 import { describe, expect, it, vi } from "vitest";
 import {
   hasSingleUseRootComposeTargetState,
+  readRootComposeSectionTargetFromLocationState,
   shouldStartComposingFromLocationState,
 } from "@/views/RootComposeView";
 import { useCreateThreadInEnvironment } from "./useCreateThreadInEnvironment";
@@ -19,19 +20,27 @@ vi.mock("@/lib/root-compose-selection", () => ({
 }));
 
 describe("useCreateThreadInEnvironment", () => {
-  it("navigates with state that opens the composer and seeds the environment", () => {
-    navigate.mockClear();
-    const { result } = renderHook(() =>
-      useCreateThreadInEnvironment({
-        projectId: "proj_personal",
-        environmentId: "env_1",
-      }),
-    );
+  it.each(["sec_a", null])(
+    "opens the composer in the source environment and section %s",
+    (sectionId) => {
+      navigate.mockClear();
+      const { result } = renderHook(() =>
+        useCreateThreadInEnvironment({
+          projectId: "proj_personal",
+          environmentId: "env_1",
+          sectionId,
+        }),
+      );
 
-    result.current();
+      result.current();
 
-    const state = navigate.mock.calls[0][1].state;
-    expect(shouldStartComposingFromLocationState(state)).toBe(true);
-    expect(hasSingleUseRootComposeTargetState(state)).toBe(true);
-  });
+      const state = navigate.mock.calls[0][1].state;
+      expect(state.reuseEnvironmentId).toBe("env_1");
+      expect(readRootComposeSectionTargetFromLocationState(state)).toEqual(
+        sectionId ? { kind: "set", sectionId } : { kind: "clear" },
+      );
+      expect(shouldStartComposingFromLocationState(state)).toBe(true);
+      expect(hasSingleUseRootComposeTargetState(state)).toBe(true);
+    },
+  );
 });

apps/app/src/hooks/useCreateThreadInEnvironment.ts

@@ -6,18 +6,24 @@ import { useSetRootComposeProjectId } from "@/lib/root-compose-selection";
 interface UseCreateThreadInEnvironmentArgs {
   projectId: string;
   environmentId: string;
+  sectionId: string | null;
 }
 
 export function useCreateThreadInEnvironment({
   projectId,
   environmentId,
+  sectionId,
 }: UseCreateThreadInEnvironmentArgs): () => void {
   const navigate = useRouteNavigate();
   const setRootComposeProjectId = useSetRootComposeProjectId();
   return useCallback(() => {
     setRootComposeProjectId(projectId);
     navigate(getRootComposeRoutePath(), {
-      state: { focusPrompt: true, reuseEnvironmentId: environmentId },
+      state: {
+        focusPrompt: true,
+        reuseEnvironmentId: environmentId,
+        sectionId,
+      },
     });
-  }, [environmentId, navigate, projectId, setRootComposeProjectId]);
+  }, [environmentId, navigate, projectId, sectionId, setRootComposeProjectId]);
 }

apps/app/src/views/thread-detail/ThreadDetailView.tsx

@@ -1213,6 +1213,7 @@ function ThreadDetailViewInternal(props: ThreadRoutePathArgs) {
   const createThreadInEnvironment = useCreateThreadInEnvironment({
     projectId,
     environmentId: thread?.environmentId ?? "",
+    sectionId: thread?.sectionId ?? null,
   });
   const { providers: registeredEnvironmentProviders } =
     useSystemEnvironmentProviders();