Windows 11 September 2025 Update: On-Device Copilot AI Binaries and UI Enhancements

Microsoft’s September cumulative for Windows 11 landed as more than a routine Patch Tuesday — it bundles visible UI polish, several quality-of-life fixes, and a new tranche of staged, hardware‑gated AI features, but it also carries a practical sting: unusually large offline installers that include on‑device Copilot model binaries and push significant download and storage demands onto every PC that receives the update. (support.microsoft.com)

Background / Overview​

Microsoft published the September cumulative for Windows 11 (KB5065426, OS Build 26100.6584) on September 9, 2025. The package mixes security fixes with new OS behavior and on‑device AI components intended to power Copilot and Copilot+ experiences on qualifying hardware. The company’s engineering approach is explicit: ship client code and model binaries inside the cumulative, then enable features selectively (server‑side) depending on device hardware, licensing, and region. (support.microsoft.com)
This release is notable for two reasons that will affect both everyday users and IT teams: first, several headline features are exclusive to Copilot+ certified PCs (devices with NPUs or other accelerators and specific OEM/firmware attestation); second, the combined installers are roughly 3.7–3.8 GB per architecture — far larger than a typical monthly cumulative — because model binaries are included for on‑device AI. Multiple independent outlets and catalog entries confirm the size figures and Microsoft’s intent to deliver on‑device AI payloads in the cumulative. (berrall.com)

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What’s new — the headline features you’ll notice​

Copilot+‑only features: Recall home page, Click to Do tutorial, and expanded on‑device agents​

• Recall home page (Copilot+ PCs only): Recall — Microsoft’s opt‑in, local snapshot history that helps users resume prior activity — now opens to a dedicated Home landing page showing recent snapshots, top apps and websites, and a left navigation rail for Timeline, Feedback and Settings. Recall remains opt‑in and protected by local encryption and Windows Hello gating on Copilot+ hardware. (support.microsoft.com)
• Click to Do tutorial (Copilot+ PCs): A first‑run, interactive tutorial for Click to Do improves discoverability for the overlay assistant that surfaces actions from on‑screen content. This aims to reduce the friction for people who haven’t used contextual AI actions before. (techradar.com)
• Agent in Settings expands to AMD and Intel Copilot+ machines: The on‑device Agent in Settings (sometimes called the Settings agent, powered by a small local language model) that answers natural‑language queries and suggests settings or repairs has been expanded from Snapdragon/ARM Copilot+ devices to eligible AMD and Intel Copilot+ hardware (English initially). The agent runs locally, proposes changes, and requires explicit user confirmation before it commits system modifications. This capability is hardware‑gated and controllable by administrators. (techradar.com)

Together, these Copilot+ features underline Microsoft’s strategy of shifting inference to local silicon where available, improving latency and offline responsiveness, while gating rollout by hardware capability and licensing.

Windows Search and Task Manager polish​

• Image grid view in Search and indexing progress: The Windows Search experience now displays image results in a grid, simplifying photo discovery. Search also surfaces a visible indexing progress indicator so users can tell whether results are complete or still being prepared. These are classic quality‑of‑life improvements for people who search for local photos frequently. (windowscentral.com)
• Task Manager CPU reporting standardized: Microsoft has revised the Task Manager’s CPU calculation so that the values displayed in Processes, Performance, and Users pages line up with one another and match industry norms. The previous discrepancy — where Processes might show a process as 100% even if only one core was used — is being replaced by a standardized metric. For backward compatibility, an optional “CPU Utility” column preserves the legacy calculation for scripts or workflows that relied on it. Independent coverage and Microsoft’s notes both confirm the change. (pcworld.com)

Other visible polish and small wins​

• Lock screen widget selection: Users can now choose which widgets appear on the lock screen (add, remove, rearrange), an expansion of earlier regional experiments; this increases personalization without forcing unwanted content on the lock surface. (reddit.com)
• Windows Hello and notification UX updates: Windows Hello received a refreshed sign‑in UI; the notification center can optionally show a larger clock including seconds; permission prompts dim the background for clarity. These are discrete but meaningful refinements that improve discoverability and focus.
• Windows Studio Effects and camera routing: Copilot+ devices gain broader Windows Studio Effects support (background blur, voice focus, simulated eye contact), and Microsoft is extending these effects to external webcams via per‑camera toggles in Settings, subject to hardware/NPU support. (windowscentral.com)

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The size problem: why this update is unusually large​

The practical complaint many users are seeing is simple: the September cumulative’s offline installers approach ~3.7–3.8 GB per architecture. Published direct downloads and catalog entries show the x64 package at ~3.81 GB and ARM64 near ~3.69 GB. Independent aggregators and update catalogs trace the bulk of that footprint to on‑device AI model binaries included in the cumulative so that Copilot+ features can work offline or with lower latency. (berrall.com)
Why Microsoft shipped model binaries inside the LCU:

• To enable offline inference and low‑latency Copilot experiences on qualifying hardware.
• To provide a single servicing artifact that can be delivered broadly while the company uses server flags and entitlement checks to enable features on supported hardware.

Operational consequence: even non‑Copilot+ PCs receive the large installer blobs (they will not necessarily get the Copilot+ UI enabled, but the model data is packaged alongside). That design saves Microsoft complexity but shifts storage and bandwidth costs onto all customers. (support.microsoft.com)

Real‑world impact​

• Devices with small SSDs (e.g., 64–128 GB) will feel immediate pressure during download and installation.
• Metered or capped connections will incur larger monthly downloads.
• Organizations managing large fleets must factor increased bandwidth, storage staging, and potential user helpdesk churn into deployment timelines.

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Who gets what — the Copilot+ gating story explained​

Microsoft’s rollout model places enabling logic in three places:

• The LCU (cumulative) delivers code and model binaries to the device.
• Server‑side flags, device attestation, and licensing checks decide whether the device sees the Copilot+ experience.
• Hardware: Copilot+ certification typically requires an NPU or equivalent accelerator, firmware/TPM attestation, and OEM provisioning.

That means two otherwise identical machines can show different post‑update behavior: one with Copilot+ features available, the other without. The gating is explicit in Microsoft’s public notes and documented in the update’s component list (Settings Model, Semantic Analysis, Image Search component versions are part of the package). (support.microsoft.com)
Implication: being updated does not guarantee you’ll get the “new” AI UI — but it does mean you incur the download and storage cost.

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Privacy, security, and enterprise governance concerns​

Recall and screen‑history privacy​

Recall stores local snapshots of screen and activity to enable resumption. Microsoft emphasizes opt‑in behavior, local encryption, and Windows Hello gating on Copilot+ PCs, but the feature’s existence raises legitimate questions:

• What gets captured by default and how easy is it to avoid sensitive captures (credentials, PHI, PII)?
• How are retention and purge policies configured for enterprise‑managed devices?
• What audit trails and administrative controls exist to detect misuse?

Microsoft’s implementation includes local encryption and Windows Hello for unlocking saved content, but administrative policies, documented retention and purge controls, and clear user consent flows will be essential before broad enterprise enablement. Community reporting and Microsoft’s own documentation flag these governance points.

On‑device models and telemetry​

On‑device inference reduces cloud exposure, but administrators and privacy teams must still understand:

• What telemetry (if any) is emitted by model inference or feature usage?
• Which features require cloud fallbacks or M365 entitlements that may transmit content?
• How does Microsoft surface per‑feature diagnostics in telemetry so administrators can audit usage?

Microsoft’s docs and support notes indicate per‑feature controls and “recent AI activity” tracking in Settings, but organizations should test and validate behavior under their telemetry baseline before enabling Copilot+ broadly. (windowscentral.com)

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Known issues and hard requirements​

Microsoft’s KB page for KB5065426 (OS Build 26100.6584) lists the update’s highlights and known issues and notes that the release includes updated AI components (Image Search, Content Extraction, Semantic Analysis, Settings Model). The support page also highlighted ancillary concerns — for example, Secure Boot certificate expirations that organizations must plan for well in advance of June 2026. Review of Microsoft’s release notes is the authoritative starting point for any deployment. (support.microsoft.com)
Real‑world testing from community and coverage outlets has documented additional risk vectors:

• Driver incompatibilities can still cause blue screens or update rollback scenarios on certain machine/driver combinations.
• Some copilot features were regionally staged (e.g., widget dashboards and lock screen experiments initially in Europe).
• Insiders and early adopters have reported occasional regressions in Recall and Click to Do during early flights.

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Recommended approach for home users and enthusiasts​

Follow a pragmatic, staged approach to installing and evaluating this update:

• Free up storage and check space: Ensure you have at least 10–15 GB free on the system drive prior to installing large cumulatives; that buffer helps avoid temporary space exhaustion during patch staging.
• Backup important files: Create a system image or at least file backups before a major cumulative that includes new components.
• Install on a test device first: If you have multiple machines, update a non‑critical PC first to validate driver compatibility and user‑profile behavior.
• Delay or pause if constrained: If a device has limited storage or you rely on metered data, use the Windows Update pause or schedule download during off‑peak windows.
• Review and toggle features: For privacy‑sensitive setups, check Settings > Privacy & security for Recall, AI activity controls, and diagnostic settings before enabling Copilot‑enabled features. (support.microsoft.com)

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Practical steps for IT and enterprise administrators​

Enterprises should treat KB5065426 as a non‑routine cumulative with operational implications:

• Inventory and classify endpoints: Identify which devices are Copilot+ certified, which have limited SSD capacity, and which run legacy drivers that historically caused update problems.
• Prepare bandwidth and content staging: Use Delivery Optimization, WSUS, or SCCM/Intune staging to distribute the large payloads efficiently, and consider peer caching for remote offices.
• Pilot ring: Deploy the update to a small, representative pilot group (including Copilot+ and non‑Copilot machines) for at least one week to capture telemetry on battery, thermal, driver, and UX impacts.
• Audit privacy and compliance: Define policies for Recall and any snapshot/storage features, including automatic purge durations, encryption keys, and role‑based access to stored artifacts.
• Communicate with users: Publish guidance that explains why the update is large, how to reclaim space, and how to opt in/out of AI features where appropriate. (support.microsoft.com)

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Risk assessment — strengths and tradeoffs​

Strengths and strategic opportunities​

• Faster, local AI experiences: On‑device inference yields lower latency and offline capability, improving dictation, camera effects, contextual actions, and accessibility features for qualifying hardware.
• Incremental polish: UX improvements — standardized Task Manager metrics, clearer indexing status, lock screen tweakability, and a refreshed Windows Hello — make the everyday experience feel smoother.
• Privacy options: Running models locally reduces cloud exposure compared with cloud‑only inference scenarios, a material plus for regulated or privacy‑conscious deployments. (windowscentral.com)

Notable risks​

• Update bloat for all devices: Packaging model binaries in the cumulative increases download and storage costs for every device, even those that will never enable Copilot+ features.
• Uneven user experience: Hardware gating and server‑side flags lead to inconsistent UI/UX between otherwise identical endpoints — a support overhead for helpdesks.
• Governance and privacy complexity: Features like Recall add questions around capture scope, retention, and legal/regulatory compliance that organizations must resolve before enabling.
• Driver compatibility: As with past 24H2 deployments, certain drivers (audio, camera, GPU) remain potential sources of post‑update disruption. (windowslatest.com)

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Mitigations and practical fixes​

• Use Delivery Optimization or WSUS/Update Catalog to pre-stage the large .msu packages and avoid saturating WAN links; peer caching helps remote sites.
• Configure Intune policies to control feature enablement or hide Copilot elements until testing and governance are complete.
• Disable or defer Recall and other Copilot+ features via Group Policy or MDM profiles until audit and consent workflows are in place.
• Keep device drivers and firmware current; treat firmware updates (OEM device platforms and NPU drivers) as preconditions to Copilot+ enablement.
• For constrained devices, leverage the Windows Disk Cleanup and Storage Sense tools to reclaim staging and temporary file space before update. (support.microsoft.com)

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Final verdict — what this means for Windows users​

The September cumulative for Windows 11 is an evolutionary update with strategic intent: Microsoft is embedding on‑device Copilot model binaries so local AI features can be delivered at low latency and (in some cases) offline. That future is compelling — better dictation, smarter camera effects, and contextual helpers that reduce friction are real productivity wins for those on compatible hardware. (techradar.com)
However, Microsoft chose a tradeoff that will sting many users today: packaging model binaries into broadly distributed cumulative installers raises download and storage demands for everyone, including traditional systems that won’t get Copilot+ features enabled. The result is an uneven rollout experience and operational friction for constrained devices and managed fleets. Administrators and savvy home users should assume this is the new normal for near‑term releases and plan accordingly: stage patches, audit privacy settings, validate drivers, and postpone or pilot where appropriate. (berrall.com)
The big picture is clear: Windows is evolving into an agentic, AI‑augmented OS with on‑device intelligence where hardware permits. That progression offers real benefits, but the industry and Microsoft still need to refine delivery strategy so feature gains do not impose disproportionate costs on the many devices that will never fully use those models. Until then, the September update is both a meaningful step forward and a reminder that software architecture choices — particularly around update packaging and gating — have immediate consequences for users and IT teams. (support.microsoft.com)

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Quick checklist (actionable items)​

• Free up at least 10–15 GB on small SSD systems before installing this cumulative.
• Pilot KB5065426 on a non‑critical machine first.
• Verify driver and firmware currency (audio, GPU, camera).
• Configure Delivery Optimization or WSUS for managed environments.
• Review privacy settings for Recall and other Copilot features before enabling.

The September cumulative is worth attention: it delivers polished improvements and a preview of a more agentive Windows, but the operational and privacy tradeoffs are tangible. Prepare now, pilot carefully, and treat Copilot+ features as opt‑in benefits rather than automatic upgrades. (support.microsoft.com)

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Source: Observer Voice Windows 11 Update Introduces Top Features with Notable Drawback