feat(desktop): download updates in background

apps/desktop/src/updates/DesktopUpdates.test.ts

@@ -274,7 +274,7 @@ describe("DesktopUpdates", () => {
     }).pipe(Effect.provide(Layer.merge(TestClock.layer(), harness.layer)));
   });
 
-  it.effect("updates and broadcasts state from updater events", () => {
+  it.effect("downloads and broadcasts an available update immediately", () => {
     const harness = makeHarness();
 
     return Effect.scoped(
@@ -286,10 +286,10 @@ describe("DesktopUpdates", () => {
         yield* flushCallbacks;
 
         const state = yield* updates.getState;
-        assert.equal(state.status, "available");
+        assert.equal(state.status, "downloading");
         assert.equal(state.availableVersion, "1.2.4");
         assert.isNotNull(state.checkedAt);
-        assert.equal(harness.sentStates.at(-1)?.status, "available");
+        assert.equal(harness.sentStates.at(-1)?.status, "downloading");
       }),
     ).pipe(Effect.provide(Layer.merge(TestClock.layer(), harness.layer)));
   });
@@ -321,7 +321,7 @@ describe("DesktopUpdates", () => {
         yield* flushCallbacks;
 
         const state = yield* updates.getState;
-        assert.equal(state.status, "available");
+        assert.equal(state.status, "downloading");
         assert.deepEqual(state.releaseNotes, [
           {
             version: "1.2.4-nightly.20260709.766",
@@ -407,7 +407,7 @@ describe("DesktopUpdates", () => {
     );
   });
 
-  it.effect("recovers download state after an unexpected setup failure", () => {
+  it.effect("leaves an automatic download available to retry after setup failure", () => {
     let disableDifferentialCalls = 0;
     const harness = makeHarness({
       setDisableDifferentialDownload: Effect.suspend(() => {
@@ -425,10 +425,6 @@ describe("DesktopUpdates", () => {
         harness.emit("update-available", { version: "1.2.4" });
         yield* flushCallbacks;
 
-        const result = yield* updates.download;
-        assert.isTrue(result.accepted);
-        assert.isFalse(result.completed);
-
         const failedState = yield* updates.getState;
         assert.equal(failedState.status, "available");
         assert.equal(failedState.errorContext, "download");
@@ -451,6 +447,9 @@ describe("DesktopUpdates", () => {
             return Effect.void;
           }
           if (disableDifferentialCalls === 2) {
+            return Effect.die(new Error("automatic download setup failed"));
+          }
+          if (disableDifferentialCalls === 3) {
             return Deferred.succeed(actionStarted, undefined).pipe(Effect.andThen(Effect.never));
           }
           return Effect.void;
@@ -470,7 +469,10 @@ describe("DesktopUpdates", () => {
 
           const interruptedState = yield* updates.getState;
           assert.equal(interruptedState.status, "available");
-          assert.isNull(interruptedState.message);
+          assert.equal(
+            interruptedState.message,
+            "Desktop update download action failed unexpectedly.",
+          );
 
           const retry = yield* updates.download;
           assert.isTrue(retry.accepted);

apps/desktop/src/updates/DesktopUpdates.ts

@@ -575,14 +575,16 @@ export const make = Effect.gen(function* () {
 
           const checkedAt = yield* currentIsoTimestamp;
           const releaseNotes = normalizeDesktopUpdateReleaseNotes(info.releaseNotes, info.version);
-          yield* setState(
+          yield* Ref.set(
+            updateStateRef,
             reduceDesktopUpdateStateOnUpdateAvailable(state, info.version, checkedAt, releaseNotes),
           );
           yield* Ref.set(lastLoggedDownloadMilestoneRef, -1);
           yield* logUpdaterInfo("update available", {
             version: info.version,
             releaseNoteGroups: releaseNotes.length,
           });
+          yield* downloadAvailableUpdate;
         }),
       ),
       Effect.catchCause((cause) => {

apps/web/src/components/sidebar/SidebarUpdatePill.tsx

@@ -243,7 +243,7 @@ function SidebarUpdateControl() {
               type="button"
               aria-label={tooltip}
               aria-disabled={disabled || isActionPending || undefined}
-              disabled={disabled || isActionPending}
+              disabled={isActionPending || (!isUpdateState && disabled)}
               className={cn(
                 "inline-flex size-8 items-center justify-center rounded-full outline-hidden ring-ring transition-colors enabled:cursor-pointer focus-visible:ring-2 disabled:cursor-not-allowed disabled:opacity-60",
                 isUpdateState
@@ -254,6 +254,8 @@ function SidebarUpdateControl() {
             >
               {action === "install" ? (
                 <RotateCwIcon className="size-4" />
+              ) : isDownloading ? (
+                <RefreshCwIcon className="size-4 animate-spin" />
               ) : isUpdateState ? (
                 <DownloadIcon className="size-4" />
               ) : (

docs/user/updating.md

@@ -20,6 +20,12 @@ connection will disappear briefly and work that is still running may be interrup
 
 The update does not remove saved threads, settings, or project files.
 
+## Desktop App Updates
+
+The desktop app downloads its own updates in the background. Once an update is ready, select
+**Restart to update** when you are ready to close T3 Code. T3 Code always asks for confirmation
+before restarting, and a failed background download remains available to retry.
+
 ## Choose the Action You See
 
 | Action                     | What to do                                                                                                                                                                  |