iOS 27 beta 4 ships with new Siri voices and dual-battery iPhone code

After a week with no Apple builds, Monday July 20 brought both iOS 27 beta 4 (build 24A5390f) and the iOS 26.6 release candidate (build 23G71). Beta 4 redesigns Siri's voice picker, adds a ProRes Log 2 camera option, removes the wallpaper cutout beta 3 introduced, and hides Battery Health strings for an iPhone with two batteries. The 26.6 RC's notes confirm it optimizes the Spotlight index to prepare for iOS 27, doing the reindexing work now so the week-long battery drain beta testers hit shouldn't return for everyone in September.

iOS 27 beta 4: what changed, what broke, and whether to install

Apple seeded iOS 27 beta 4 to developers on Monday, build 24A5390f replacing beta 3's 24A5380h (iClarified, AppleInsider). It's a developer beta; public beta testers are still on public beta 1 from July 13, and 9to5Mac expects this same code to reach them as public beta 2 "next week."

For normal users. Apple removed the wallpaper cutout beta 3 added, where swiping the Notification Center showed a cutout of your wallpaper's subject on the Home Screen. 9to5Mac frames it as "the depth effect bug that beta 3 introduced. It was fun while it lasted." Photos gains a "Zoom Photos to Fill" toggle (Settings > Photos) that slightly zooms pictures that nearly match your screen's aspect ratio, on by default. The Apple TV app gets an Automatic Downloads toggle that grabs the next two episodes of a show you start in Continue Watching and deletes them when you finish.

For power users. The Siri voice picker is redesigned: on phones without a customizable voice it now shows the custom-voice interface with voices and accents to pick; on phones with custom Siri, more voice options appear labeled "coming soon." Two enhanced Siri voices now have pace and expressivity working, while five legacy voices still show those sliders as "coming soon" (9to5Mac). Customizable voice stays limited to the iPhone 17 Pro, 17 Pro Max, and iPhone Air, the 12GB RAM phones. Siri settings add a control for how long previews run in the Siri app (up to five lines or none), Accessibility adds an "Always Show Request" toggle that prints a transcription of what you say to Siri on screen, and invoking Siri from the Dynamic Island or a swipe-down now shows a splash screen. Camera gets a ProRes Log format picker: with ProRes on, tap ProRes Log Video Encoding and choose Log or Log 2, with Log 2 retaining more data for color grading. Wi-Fi lets you toggle Connectivity Assist per network, independent of the master switch, and AirPods options in Control Center are redesigned with more Adaptive mode choices.

What broke and what's fixed. Apple's release notes confirm beta 4 fixes the deeply-discharged battery bug where a phone could get stuck on the red dead-battery screen and fail to boot until you restarted it or replugged the adapter. Beta 3 drew real battery-drain complaints tied to indexing, including a MacRumors forum thread from July 8 titled "INSANE BATTERY DRAIN"; beta 4 is only a day old, so the real battery verdict needs a few more days, though MacObserver says it appears focused on bug fixes and stability.

Verdict. Developers, install on a spare device with the usual caution. If you're on the public beta, wait for public beta 2 next week, which is the same code, rather than switching to the dev channel.

iOS 26.6 RC: the next version for everyone, and it preps your phone for iOS 27

Apple also shipped the iOS 26.6 release candidate on Monday, build 23G71 replacing beta 5 (AppleInsider). The official release notes, confirmed publicly for the first time, read: "This update includes bug fixes, security updates and optimizes the Spotlight index to prepare for iOS 27."

That last clause is the interesting one. When the iOS 27 beta first shipped in June, developers noticed their iPhones reindexing for a week or longer, the same drain public beta testers later lived through. Apple is using 26.6 to do much of that Spotlight indexing work now, so the public iOS 27 rollout in September is smoother. If you install 26.6 and notice Spotlight indexing, that's why.

The two changes already known from the beta cycle carry into the RC: a warning when you hit the blocked-contacts limit (20,000, under Family Sharing), and an anti-snatch auto-lock feature sitting in code, using the accelerometer to detect a yank, Apple Watch Bluetooth distance to detect separation, and Stolen Device Protection rules, with no toggle and no Apple announcement, so it may not ship switched on. Security, one sentence: the notes confirm security updates are included, but Apple hasn't published the detailed CVE list yet, which arrives with the public release. Companion RCs, iPadOS, watchOS, tvOS, visionOS, macOS Tahoe, and HomePod Software 26.6, all landed the same day.

Verdict. The RC is the final build unless Apple finds a last-minute bug. 9to5Mac expects the public release on or around Monday July 27, which lines up with history (iOS 18.6 landed July 29, 2025; 17.6 on July 29, 2024). If you're on iOS 26.5.2, wait the roughly one week for the public release rather than installing the dev RC, then yes, install it, and especially before iOS 27 in September so the pre-indexing is already done.

Beta 4 hides Battery Health strings for an iPhone with two batteries

Macworld's Filipe Espósito dug into beta 4 and found new Battery Health strings written in the plural, and MacRumors confirmed they're in the build: "The batteries in this iPhone are performing as expected," "The health of the batteries in this iPhone has significantly degraded," and "one of the batteries could not be verified as a genuine Apple battery."

No current iPhone uses the plural wording. The most likely fit is the foldable iPhone Ultra, expected to split its battery into two cells, one on each side of the hinge, the standard layout for book-style foldables. Supply-chain filings pointed to cells of 1,921mAh and 2,962mAh for a combined 4,883mAh. The "one of the batteries" phrasing implies per-cell authentication, which could mean two separate parts-pairing checks at repair time.

This stacks on the foldable code already found in iOS 27 since beta 1 on June 8: fold-state detection, hinge-angle APIs, and multi-display references. AppleInsider adds a caveat that the plural could be a red herring, noting the 2017 iPhone X used two battery cells in one body, but the cumulative foldable code across all four betas makes the foldable explanation the stronger one. The iPhone Ultra is expected to debut in September alongside the iPhone 18 Pro.