fix(web): allow folder references on saved local desktop servers

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

@@ -261,7 +261,7 @@ import { useMediaQuery } from "../../hooks/useMediaQuery";
 import { useSoftwareKeyboardOpen } from "../../hooks/useSoftwareKeyboardOpen";
 import { useStableCallback } from "../../hooks/useStableCallback";
 import { usePanelAnimationSettings } from "../../panelAnimations";
-import { readEnvironmentScope } from "../../state/session";
+import { readEnvironmentScope, readPreparedConnection } from "../../state/session";
 import type { ReviewCommentContext } from "../../reviewCommentContext";
 import { useComposerRestingTransition } from "./useComposerRestingTransition";
 import { ComposerCommandMenuLayer } from "./ComposerCommandMenuLayer";
@@ -2522,11 +2522,13 @@ export const ChatComposer = memo(function ChatComposer(props: ChatComposerProps)
       localEnvironmentDisabled: isLocalEnvironmentDisabled(),
       environmentId,
       primaryEnvironmentId,
+      connection: readPreparedConnection(environmentId),
+      isDesktopRenderer: window.desktopBridge !== undefined,
     });
     if (target === "remote") {
       toastManager.add({
         type: "error",
-        title: "Folders can only be referenced in the local desktop environment",
+        title: "Folders can only be referenced on a server running on this computer",
       });
       return;
     }

apps/web/src/components/chat/folderDrop.test.ts

@@ -0,0 +1,82 @@
+import {
+  BearerConnectionTarget,
+  RelayConnectionTarget,
+  SshConnectionTarget,
+} from "@t3tools/client-runtime/connection";
+import { EnvironmentId } from "@t3tools/contracts";
+import { describe, expect, it } from "vite-plus/test";
+
+import { folderDropTarget } from "./folderDrop";
+
+const environmentId = EnvironmentId.make("saved-local");
+const base = { environmentId, label: "server" };
+const savedServer = (httpBaseUrl: string, connectionId = "saved-1") => ({
+  target: new BearerConnectionTarget({ ...base, connectionId }),
+  httpBaseUrl,
+});
+const thinClient = {
+  localEnvironmentDisabled: true,
+  environmentId,
+  primaryEnvironmentId: null,
+  isDesktopRenderer: true,
+};
+
+describe("folderDropTarget", () => {
+  it.each([
+    [
+      "the bundled primary",
+      {
+        ...thinClient,
+        localEnvironmentDisabled: false,
+        primaryEnvironmentId: environmentId,
+        connection: null,
+      },
+      "local",
+    ],
+    [
+      "a saved loopback server on desktop",
+      { ...thinClient, connection: savedServer("http://127.0.0.1:3773") },
+      "local",
+    ],
+    [
+      "a saved LAN server",
+      { ...thinClient, connection: savedServer("http://192.168.1.20:3773") },
+      "remote",
+    ],
+    [
+      "a saved loopback server in a browser",
+      { ...thinClient, isDesktopRenderer: false, connection: savedServer("http://localhost:3773") },
+      "remote",
+    ],
+    [
+      "a desktop WSL backend",
+      { ...thinClient, connection: savedServer("http://127.0.0.1:3774", "local:wsl-ubuntu") },
+      "remote",
+    ],
+    [
+      "an SSH forward on loopback",
+      {
+        ...thinClient,
+        connection: {
+          target: new SshConnectionTarget({ ...base, connectionId: "ssh-1" }),
+          httpBaseUrl: "http://127.0.0.1:41000",
+        },
+      },
+      "remote",
+    ],
+    [
+      "a relay connection",
+      {
+        ...thinClient,
+        connection: {
+          target: new RelayConnectionTarget(base),
+          httpBaseUrl: "https://relay.t3.codes",
+        },
+      },
+      "remote",
+    ],
+    ["an unprepared connection", { ...thinClient, connection: null }, "remote"],
+  ] as const)("targets %s", (_name, input, expected) => {
+    expect(folderDropTarget(input)).toBe(expected);
+  });
+});

apps/web/src/components/chat/folderDrop.ts

@@ -1,18 +1,43 @@
+import type { PreparedConnection } from "@t3tools/client-runtime/connection";
 import type { EnvironmentId } from "@t3tools/contracts";
 
+import { isDesktopLocalConnectionTarget } from "~/connection/desktopLocal";
+import { isLoopbackHostname } from "~/environments/primary/target";
+
 export function folderDropTarget(input: {
   localEnvironmentDisabled: boolean;
   environmentId: EnvironmentId;
   primaryEnvironmentId: EnvironmentId | null;
+  connection: Pick<PreparedConnection, "target" | "httpBaseUrl"> | null;
+  isDesktopRenderer: boolean;
 }): "local" | "remote" {
   if (
-    input.localEnvironmentDisabled ||
-    input.primaryEnvironmentId === null ||
-    input.environmentId !== input.primaryEnvironmentId
+    !input.localEnvironmentDisabled &&
+    input.primaryEnvironmentId !== null &&
+    input.environmentId === input.primaryEnvironmentId
   ) {
-    return "remote";
+    return "local";
+  }
+  return input.isDesktopRenderer &&
+    input.connection !== null &&
+    isSavedLoopbackConnection(input.connection)
+    ? "local"
+    : "remote";
+}
+
+// A direct saved connection to loopback shares the desktop's filesystem; WSL backends and SSH forwards do not.
+function isSavedLoopbackConnection({
+  target,
+  httpBaseUrl,
+}: Pick<PreparedConnection, "target" | "httpBaseUrl">): boolean {
+  if (target._tag !== "BearerConnectionTarget" || isDesktopLocalConnectionTarget(target)) {
+    return false;
+  }
+  try {
+    return isLoopbackHostname(new URL(httpBaseUrl).hostname);
+  } catch {
+    return false;
   }
-  return "local";
 }
 
 export function resolveDroppedFolderPath(