🤖 feat: add stable/nightly Electron update channels (#2430)

## Summary

Adds a user-selectable update channel (Stable / Nightly) to the Mux
Electron app. Users can switch channels from the About dialog; the
choice is persisted in `~/.mux/config.json` and takes effect immediately
at runtime.

## Background

The Electron app currently updates only from official GitHub Releases
("Stable"). This PR adds support for a "Nightly" channel that pulls
pre-release builds published from `main`. This gives users who want
bleeding-edge features an opt-in path without disrupting the default
stable experience.

## Implementation

### Config layer (`src/node/config.ts`)
- New `UpdateChannel` type (`"stable" | "nightly"`) with
`parseUpdateChannel()` validation.
- Persisted in config.json — only non-default values are written (stable
is the default, so the key is omitted when on stable).

### Desktop updater (`src/desktop/updater.ts`)
- `applyChannel()` configures `autoUpdater`: `allowPrerelease`,
`channel`, feed URL `releaseType`.
- `setChannel()` method with state guards (blocks switching during
download/install).
- Transient error filtering (404s, network timeouts) to avoid noisy
errors during manifest propagation.

### oRPC surface (`src/common/orpc/schemas/api.ts`,
`src/node/orpc/router.ts`)
- `update.getChannel` / `update.setChannel` endpoints with Zod-validated
`UpdateChannelSchema`.

### Frontend (`src/browser/components/About/AboutDialog.tsx`)
- Channel picker using standard `ToggleGroup` segmented control
(size="sm", matching other consumers).
- Race condition protection via `channelRequestTokenRef` counter.
- Channel state initialized to `null` until fetched, preventing layout
flicker.
- Local `pendingAction` state gives immediate click feedback (spinner +
disabled) for Check, Download, and Install buttons while waiting for the
backend status stream to catch up.

### Button press feedback (`src/browser/components/ui/button.tsx`)
- Added `active:scale-[0.98]` press animation and `transition-all` so
all buttons give tactile click feedback.

### CI: manifest naming (`scripts/set-package-version.js`)
- Detects prerelease suffix (e.g. `-nightly.N`) and sets
`build.publish.channel` in `package.json` so electron-builder generates
channel-specific manifests (`nightly.yml`, `nightly-mac.yml`) instead of
`latest.yml`.

## Validation

- All static checks pass locally (`make static-check`: typecheck, lint,
fmt, broken links).
- Updater test suite (`src/desktop/updater.test.ts`) covers channel
switching, state guards, and transient error handling.

## Risks

- **macOS code signing**: The manifest naming fix
(set-package-version.js) ensures electron-updater finds the correct
`nightly-mac.yml` manifest. Previously, the build produced
`latest-mac.yml` which caused signature validation failures when the
client expected `nightly-mac.yml`.

---

_Generated with `mux` • Model: `anthropic:claude-opus-4-6` • Thinking:
`xhigh` • Cost: `$26.04`_

<!-- mux-attribution: model=anthropic:claude-opus-4-6 thinking=xhigh
costs=26.04 -->

Author: ibetitsmike

scripts/set-package-version.js

@@ -16,7 +16,26 @@ if (!nextVersion || typeof nextVersion !== "string" || nextVersion.trim().length
 
 const packageJsonPath = "package.json";
 const packageJson = JSON.parse(fs.readFileSync(packageJsonPath, "utf8"));
-packageJson.version = nextVersion.trim();
+const version = nextVersion.trim();
+packageJson.version = version;
+
+// When version includes a prerelease suffix like "-nightly.N", tell
+// electron-builder to generate channel-specific manifests (e.g. nightly.yml,
+// nightly-mac.yml) instead of the default latest.yml. electron-updater on
+// the client uses autoUpdater.channel to resolve the matching manifest name.
+const prereleaseMatch = version.match(/-([a-z]+)\./);
+if (prereleaseMatch && packageJson.build?.publish) {
+  const channel = prereleaseMatch[1]; // e.g. "nightly"
+  if (Array.isArray(packageJson.build.publish)) {
+    for (const pub of packageJson.build.publish) {
+      pub.channel = channel;
+    }
+  } else if (typeof packageJson.build.publish === "object") {
+    packageJson.build.publish.channel = channel;
+  }
+  console.log(`Set publish channel to "${channel}"`);
+}
+
 fs.writeFileSync(packageJsonPath, `${JSON.stringify(packageJson, null, 2)}\n`);
 
 console.log(`Set package.json version to ${packageJson.version}`);

src/browser/components/About/AboutDialog.tsx

@@ -1,4 +1,4 @@
-import { useEffect, useState } from "react";
+import { useEffect, useRef, useState } from "react";
 import { Download, Loader2, RefreshCw } from "lucide-react";
 import { VERSION } from "@/version";
 import type { UpdateStatus } from "@/common/orpc/types";
@@ -9,6 +9,7 @@ import { useAPI } from "@/browser/contexts/API";
 import { useAboutDialog } from "@/browser/contexts/AboutDialogContext";
 import { Button } from "@/browser/components/ui/button";
 import { Dialog, DialogContent, DialogTitle } from "@/browser/components/ui/dialog";
+import { ToggleGroup, ToggleGroupItem } from "@/browser/components/ui/toggle-group";
 
 interface VersionRecord {
   buildTime?: unknown;
@@ -65,6 +66,10 @@ export function AboutDialog() {
   const MuxLogo = theme === "dark" || theme.endsWith("-dark") ? MuxLogoDark : MuxLogoLight;
   const { gitDescribe, buildTime } = parseVersionInfo(VERSION satisfies unknown);
   const [updateStatus, setUpdateStatus] = useState<UpdateStatus>({ type: "idle" });
+  const [channel, setChannel] = useState<"stable" | "nightly" | null>(null);
+  const [channelLoading, setChannelLoading] = useState(false);
+  const [pendingAction, setPendingAction] = useState<"check" | "download" | "install" | null>(null);
+  const channelRequestTokenRef = useRef(0);
 
   const isDesktop = typeof window !== "undefined" && Boolean(window.api);
 
@@ -84,6 +89,7 @@ export function AboutDialog() {
             break;
           }
           setUpdateStatus(status);
+          setPendingAction(null);
         }
       } catch (error) {
         if (!signal.aborted) {
@@ -97,32 +103,86 @@ export function AboutDialog() {
     };
   }, [api, isDesktop, isOpen]);
 
+  useEffect(() => {
+    if (!isOpen || !isDesktop || !api) {
+      return;
+    }
+
+    let active = true;
+    // Ignore stale getChannel() responses when a newer request or manual selection has already happened.
+    const requestToken = ++channelRequestTokenRef.current;
+
+    api.update
+      .getChannel()
+      .then((nextChannel) => {
+        if (active && requestToken === channelRequestTokenRef.current) {
+          setChannel(nextChannel);
+        }
+      })
+      .catch(console.error);
+
+    return () => {
+      active = false;
+    };
+  }, [api, isDesktop, isOpen]);
+
   const canUseUpdateApi = isDesktop && Boolean(api);
   const isChecking =
-    canUseUpdateApi && (updateStatus.type === "checking" || updateStatus.type === "downloading");
+    canUseUpdateApi &&
+    (updateStatus.type === "checking" ||
+      updateStatus.type === "downloading" ||
+      pendingAction === "check");
+
+  const handleChannelChange = (next: "stable" | "nightly") => {
+    if (!api || next === channel || channelLoading) {
+      return;
+    }
+
+    // Invalidate any in-flight getChannel() request so late responses cannot overwrite user intent.
+    channelRequestTokenRef.current += 1;
+    setChannelLoading(true);
+    api.update
+      .setChannel({ channel: next })
+      .then(() => setChannel(next))
+      .catch(console.error)
+      .finally(() => setChannelLoading(false));
+  };
 
   const handleCheckForUpdates = () => {
     if (!api) {
       return;
     }
 
-    api.update.check({ source: "manual" }).catch(console.error);
+    setPendingAction("check");
+    api.update
+      .check({ source: "manual" })
+      .catch(console.error)
+      // Clear pending if the backend no-ops (e.g. already downloaded) and emits no status event.
+      .finally(() => setPendingAction((prev) => (prev === "check" ? null : prev)));
   };
 
   const handleDownload = () => {
     if (!api) {
       return;
     }
 
-    api.update.download(undefined).catch(console.error);
+    setPendingAction("download");
+    api.update
+      .download(undefined)
+      .catch(console.error)
+      .finally(() => setPendingAction((prev) => (prev === "download" ? null : prev)));
   };
 
   const handleInstall = () => {
     if (!api) {
       return;
     }
 
-    api.update.install(undefined).catch(console.error);
+    setPendingAction("install");
+    api.update
+      .install(undefined)
+      .catch(console.error)
+      .finally(() => setPendingAction((prev) => (prev === "install" ? null : prev)));
   };
 
   return (
@@ -160,6 +220,38 @@ export function AboutDialog() {
             <div className="text-muted text-xs">Connecting to desktop update service…</div>
           ) : (
             <>
+              {channel !== null && (
+                <div className="space-y-2">
+                  <div className="flex items-center gap-2">
+                    <span className="text-muted text-xs">Channel</span>
+                    <ToggleGroup
+                      type="single"
+                      value={channel}
+                      onValueChange={(next) => {
+                        if (next === "stable" || next === "nightly") {
+                          handleChannelChange(next);
+                        }
+                      }}
+                      disabled={channelLoading}
+                      aria-label="Update channel"
+                      size="sm"
+                    >
+                      <ToggleGroupItem value="stable" size="sm">
+                        Stable
+                      </ToggleGroupItem>
+                      <ToggleGroupItem value="nightly" size="sm">
+                        Nightly
+                      </ToggleGroupItem>
+                    </ToggleGroup>
+                  </div>
+                  <div className="text-muted text-xs">
+                    {channel === "stable"
+                      ? "Official releases only."
+                      : "Nightly pre-release builds from main."}
+                  </div>
+                </div>
+              )}
+
               <Button
                 variant="outline"
                 size="sm"
@@ -179,8 +271,16 @@ export function AboutDialog() {
                   <div className="text-foreground text-xs">
                     Update available: <span className="font-mono">{updateStatus.info.version}</span>
                   </div>
-                  <Button size="sm" onClick={handleDownload}>
-                    <Download className="h-3.5 w-3.5" />
+                  <Button
+                    size="sm"
+                    onClick={handleDownload}
+                    disabled={pendingAction === "download"}
+                  >
+                    {pendingAction === "download" ? (
+                      <Loader2 className="h-3.5 w-3.5 animate-spin" />
+                    ) : (
+                      <Download className="h-3.5 w-3.5" />
+                    )}
                     Download
                   </Button>
                 </div>
@@ -197,9 +297,13 @@ export function AboutDialog() {
                   <div className="text-foreground text-xs">
                     Ready to install: <span className="font-mono">{updateStatus.info.version}</span>
                   </div>
-                  <Button size="sm" onClick={handleInstall}>
-                    <RefreshCw className="h-3.5 w-3.5" />
-                    Install & restart
+                  <Button size="sm" onClick={handleInstall} disabled={pendingAction === "install"}>
+                    {pendingAction === "install" ? (
+                      <Loader2 className="h-3.5 w-3.5 animate-spin" />
+                    ) : (
+                      <RefreshCw className="h-3.5 w-3.5" />
+                    )}
+                    {pendingAction === "install" ? "Installing…" : "Install & restart"}
                   </Button>
                 </div>
               )}
@@ -223,18 +327,40 @@ export function AboutDialog() {
                   </div>
                   <div className="flex items-center gap-2">
                     {updateStatus.phase === "download" && (
-                      <Button size="sm" onClick={handleDownload}>
-                        <Download className="h-3.5 w-3.5" />
+                      <Button
+                        size="sm"
+                        onClick={handleDownload}
+                        disabled={pendingAction === "download"}
+                      >
+                        {pendingAction === "download" ? (
+                          <Loader2 className="h-3.5 w-3.5 animate-spin" />
+                        ) : (
+                          <Download className="h-3.5 w-3.5" />
+                        )}
                         Retry download
                       </Button>
                     )}
                     {updateStatus.phase === "install" && (
-                      <Button size="sm" onClick={handleInstall}>
-                        <RefreshCw className="h-3.5 w-3.5" />
+                      <Button
+                        size="sm"
+                        onClick={handleInstall}
+                        disabled={pendingAction === "install"}
+                      >
+                        {pendingAction === "install" ? (
+                          <Loader2 className="h-3.5 w-3.5 animate-spin" />
+                        ) : (
+                          <RefreshCw className="h-3.5 w-3.5" />
+                        )}
                         Try install again
                       </Button>
                     )}
-                    <Button variant="outline" size="sm" onClick={handleCheckForUpdates}>
+                    <Button
+                      variant="outline"
+                      size="sm"
+                      onClick={handleCheckForUpdates}
+                      disabled={isChecking}
+                    >
+                      {isChecking ? <Loader2 className="h-3.5 w-3.5 animate-spin" /> : null}
                       {updateStatus.phase === "check" ? "Try again" : "Check again"}
                     </Button>
                   </div>

src/browser/components/ui/button.tsx

@@ -4,7 +4,7 @@ import { cva, type VariantProps } from "class-variance-authority";
 import { cn } from "@/common/lib/utils";
 
 const buttonVariants = cva(
-  "inline-flex items-center justify-center gap-2 whitespace-nowrap rounded-md text-sm font-medium transition-colors focus-visible:outline-none focus-visible:ring-1 focus-visible:ring-accent disabled:pointer-events-none disabled:opacity-50 [&_svg]:pointer-events-none [&_svg]:size-4 [&_svg]:shrink-0",
+  "inline-flex items-center justify-center gap-2 whitespace-nowrap rounded-md text-sm font-medium transition-all active:scale-[0.98] focus-visible:outline-none focus-visible:ring-1 focus-visible:ring-accent disabled:pointer-events-none disabled:opacity-50 [&_svg]:pointer-events-none [&_svg]:size-4 [&_svg]:shrink-0",
   {
     variants: {
       variant: {

src/browser/stories/mocks/orpc.ts

@@ -1302,6 +1302,8 @@ export function createMockORPCClient(options: MockORPCClientOptions = {}): APICl
         yield* [];
         await new Promise<void>(() => undefined);
       },
+      getChannel: () => Promise.resolve("stable" as const),
+      setChannel: () => Promise.resolve(undefined),
     },
     policy: {
       get: () => Promise.resolve(policyResponse),

src/common/orpc/schemas/api.ts

@@ -1593,6 +1593,8 @@ export const splashScreens = {
 };
 
 // Update
+export const UpdateChannelSchema = z.enum(["stable", "nightly"]);
+
 export const update = {
   check: {
     input: z.object({ source: z.enum(["auto", "manual"]).optional() }).optional(),
@@ -1610,6 +1612,14 @@ export const update = {
     input: z.void(),
     output: eventIterator(UpdateStatusSchema),
   },
+  getChannel: {
+    input: z.void(),
+    output: UpdateChannelSchema,
+  },
+  setChannel: {
+    input: z.object({ channel: UpdateChannelSchema }),
+    output: z.void(),
+  },
 };
 
 // Editor config schema for openWorkspaceInEditor

src/common/types/project.ts

@@ -21,8 +21,18 @@ export type ProjectConfig = z.infer<typeof ProjectConfigSchema>;
 
 export type FeatureFlagOverride = "default" | "on" | "off";
 
+/**
+ * Update channel preference for Electron desktop app.
+ * Keep in sync with `UpdateChannelSchema` in `src/common/orpc/schemas/api.ts`.
+ */
+export type UpdateChannel = "stable" | "nightly";
+
 export interface ProjectsConfig {
   projects: Map<string, ProjectConfig>;
+  /**
+   * Update channel preference for Electron desktop app. Defaults to "stable".
+   */
+  updateChannel?: UpdateChannel;
   /**
    * Bind host/interface for the desktop HTTP/WS API server.
    *