Windows 11 25H2 Release Preview: Enablement Package KB5054156 and ISO Media

Microsoft’s near-final Windows 11 25H2 build has quietly begun to appear as official ISO media on Microsoft’s delivery infrastructure, with Release Preview ISOs now discoverable by enthusiasts and the enablement-package (eKB) path — KB5054156 — confirmed as the primary in-place upgrade for patched 24H2 devices.

Background / Overview​

Windows 11 version 25H2 is not being shipped as a traditional, full rebase feature update. Instead, Microsoft has used the same shared-servicing and enablement-package model it applied previously: the new feature binaries were staged through monthly cumulative updates, and a small enablement package — an eKB — flips those dormant components on for consumers and organizations already running the latest 24H2 servicing baseline. The Windows Insider Release Preview seed for 25H2 is identified in Microsoft’s official announcement as the 26200 build family, and Microsoft told Insiders that ISOs for Release Preview would be made available via the Windows Insider ISO download page.
This delivery model produces two practical artifacts IT pros and enthusiasts should care about:

• The eKB (enablement package) — small, fast, and intended for quick in-place activation on already-patched systems (the file widely referenced in community reporting is identified as KB5054156).
• The canonical ISO / media — full installation media for clean installs, offline imaging, OEM use, and lab validation; Microsoft lists Release Preview ISOs on the Insider download page and community investigators have located candidate ISO files on Microsoft’s content delivery servers.

What was published and what it actually means​

The eKB: KB5054156 (enablement package)​

Microsoft’s official Release Preview announcement explicitly states that 25H2 will be delivered as an enablement package and that eligible Release Preview PCs can “seek” the update via Settings → Windows Update. That eKB changes the system’s build identity from the 24H2 baseline to the 25H2 build family (26200.x) without re-installing all OS binaries. This dramatically reduces downtime for patched systems: a small download and a single restart in most cases.
Community and release-tracking resources (Insider threads, BetaWiki, and forum posts) consistently reference KB5054156 as the enablement package identifier. Those same sources document the build increments that carry pre-seeded 25H2 binaries into servicing. This cross-check confirms the enablement package model and the KB identifier as the canonical mechanism for upgrading 24H2 devices to 25H2.

The ISO: canonical media for imaging and clean installs​

Although the eKB is the recommended upgrade path for patched devices, Microsoft also provides official ISO media for Release Preview builds — necessary for:

• Creating bootable USBs for clean installs
• Building golden images for imaging pipelines (SCCM/MDT)
• Lab validation, OEM testing, and offline VM deployments

Multiple outlets and community investigators reported the appearance of Release Preview ISOs matching the 26200 family in the Insider ISO download area and on Microsoft’s content servers. Some community threads include direct delivery-server URLs that point to build 26200.6584 and similar artifacts; however, those direct server URLs are typically gated, time-limited, or intended for internal/Insider distribution and therefore should be treated with caution until verified via official download pages.

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How to obtain 25H2 safely: practical, verified steps​

Below are the accepted, verified methods for getting Windows 11 25H2 media or activating the eKB. Follow the path that matches your scenario (Insider testing, imaging, or production rollout).

If you’re an Insider or testing in a lab​

• Enroll the test PC in the Windows Insider Program, choose the Release Preview channel (Settings → Windows Update → Windows Insider Program), and sign in with an Insider-enabled Microsoft account.
• Use the Insider ISO download page (gated by your Microsoft account). Select the Release Preview ISO for the desired edition/language, generate the time-limited link, and download the ISO for imaging or VM use. The download page generates time-limited links; plan to download immediately once generated.
• To activate 25H2 on an already-patched 24H2 VM, you can either apply the enablement package (KB5054156) manually or use Windows Update’s seeker to get the eKB. Community-distributed MSU/CAB packages for KB5054156 exist and are quoted in several forums; however, prefer Microsoft’s own Update Catalog entry or the Insider ISO page to avoid tampered files.

If you manage production fleets (recommended enterprise path)​

• Validate dependencies first (see the Admin checklist below). Don’t rush the rollout.
• Pilot with a small percentage of devices across hardware types. Capture telemetry and validate management agents and security tooling.
• Use Windows Update for Business (WUfB) or WSUS to schedule a staged eKB rollout once Microsoft marks the release as generally available; imaging teams can adopt the official ISO for fresh installs where needed. Microsoft explicitly supports commercial validation via WUfB and WSUS for Release Preview customers and later GA for broader rollout.

If you prefer not to use the Insider Program​

• Wait for Microsoft’s general availability rollout via Windows Update. The eKB model means most fully patched 24H2 devices will receive 25H2 automatically via a small enablement update during GA, eliminating the need for manual ISO installs for in-place upgrades.

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Admin & imaging checklist: what to validate before broad deployment​

Apply the following steps to reduce risk when moving enterprise devices to 25H2.

• Inventory automation and tooling dependencies:
• Identify scripts or management tooling that rely on WMIC or PowerShell 2.0. Microsoft is removing WMIC and the legacy PowerShell 2.0 engine from shipping images; migrate scripts to PowerShell CIM/WMI cmdlets or PowerShell 5.1 / PowerShell 7+. Failing to do so will break automation.
• Confirm endpoint security, EDR, VPN and management agents:
• Test the entire agent stack after applying the eKB (or clean-installing from ISO) to ensure telemetry / tamper-protection / driver behavior remains acceptable.
• Validate imaging workflows:
• Use the canonical ISO to build golden images, then verify your out-of-box-experience (OOBE) flows and provisioning policies. The eKB won't substitute for installer-time provisioning or image capture workflows.
• BitLocker & recovery:
• Ensure BitLocker keys are accessible and recovery processes are documented before testing upgrades in production.
• Hash verification:
• Always validate ISO or MSU/CAB SHA256 (or other hashes) against official Microsoft-published values — do not rely on third-party mirrors or community-hosted copies. Community posts often republish direct server URLs, but an integrity check against Microsoft’s published hash is mandatory.
• Staged rollout:
• Stagger the deployment via rings (e.g., 5–10% pilot, 25% extended pilot, broad deployment) and maintain rollback plans.

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Strengths of Microsoft’s approach in 25H2​

• Minimal downtime for already-patched systems. The enablement-package model reduces large data transfers and restarts, which is excellent for user-facing environments and reduces productivity disruption.
• Consistent servicing baseline. 24H2 and 25H2 share core system files and servicing branches, simplifying long-term patching and support for IT teams that maintain monthly cumulative updates rather than big annual rebases.
• Canonical ISO retained for imaging. By publishing Release Preview ISOs, Microsoft continues to support OEMs, system builders, and enterprises needing authoritative media for certification and clean installs. That preserves established imaging workflows.

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Risks, caveats, and where to be cautious​

• Pre-release stability and compatibility: Release Preview builds are close to final, but still can contain regressions not present in GA. Average end users should avoid early installs on production machines; enterprise pilots and labs are the correct early adopters. Community coverage and forums warn of occasional update failures on preview builds.
• Unofficial or leaked server URLs: Community members often discover direct delivery-server URLs (software-static.download.prss.microsoft.com, catalog.sf.dl.delivery.mp.microsoft.com, etc.). While these sometimes point to legitimate Microsoft-hosted artifacts, relying on raw server links spotted in forums or social posts has hazards: links may be time-limited, part of pre-release gating, or inadvertently point at mismatched channel artifacts (Dev vs Release Preview), and they bypass the checks Microsoft provides on the insider download portal. Validate any such link against the official Insider ISO page or the Microsoft Update Catalog before using it.
• Checksum and authenticity verification: There have been repeated community warnings about fake or tampered ISOs published by malicious third parties. Always verify file hashes published by Microsoft (or the Windows Insider ISO page) before using downloaded ISOs. If a hash is not available for a spotted server link, treat the file as unverifiable and avoid use.
• Automation breakage: The removal of WMIC and PowerShell 2.0 from shipping images is a concrete dependency risk. Organizations with legacy scripts, imaging tasks, or third-party management tools that still call those components must migrate and test before mass enablement. Failure to remediate could disrupt inventory, telemetry, or provisioning.
• Channel mismatch: Dev vs Release Preview artifacts: Some community posts conflate Dev- and Release-channel artifacts (VHDX vs ISO, or arm64 Dev VHDXs vs Release Preview ISOs). Verify the channel and build identity (26200.x in Release Preview) before using media for certification or production images. Dev-channel artifacts can include experimental features not present in Release Preview or GA.

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Verifying the most important claims (transparency on verification)​

• Microsoft’s official confirmation that 25H2 is in the Release Preview channel and will be delivered as an enablement package is documented in the Windows Insider Blog announcement. That announcement also said ISOs would follow through the Insider ISO download page for Release Preview Insiders. This is the primary authoritative source for the update model.
• Independent outlets — including Tom’s Hardware and WindowsCentral — have reported that Release Preview ISOs for 25H2 (26200 family) are available for Insiders and that community members have located ISO files on Microsoft’s delivery servers. Those reports corroborate the Insider blog and provide a community-level verification that media propagation has occurred. Use those sightings for situational awareness but rely on the Insider ISO portal or Update Catalog for final validation.
• Community forum threads and release-tracking resources list KB5054156 as the enablement package identifier; BetaWiki and vendor blogs trace the build changes and show KB5054156 as the switch to 26200.x. Those independent traces give additional confidence about the KB identity and build family. However, Microsoft’s own communications should be considered the canonical authority for rollout status and servicing guidance.

Note: specific direct server URLs and raw delivery-server ISOs spotted in forums can be true and legitimate but are often time-limited or gated; those sightings should be treated as leads to confirm against official Microsoft pages rather than as final download sources. If a URL was posted publicly, treat that file as pre-release and validate its integrity before using.

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Recommended action plan (concise, prioritized)​

• If you manage devices — run an immediate (1–2 weeks) pilot:
• Identify and remediate WMIC / PowerShell v2 dependencies.
• Test AV/EDR, VPN, and management tools on pilot devices before scale.
• Capture and compare pre/post-upgrade telemetry.
• If you build images — obtain the official Insider ISO:
• Sign in to the Windows Insider ISO page and generate the download link rather than pulling raw server URLs.
• Validate ISO SHA256 against Microsoft-published hashes where available.
• If you are a casual user — wait for GA or join only in the Release Preview channel on a secondary device:
• Release Preview is production-adjacent but still pre-GA; back up data first.
• If you need to apply the eKB manually — prefer Microsoft Update Catalog or official MSU/CAB packages from Microsoft’s channels:
• Do not trust third-party mirrors without verifying integrity.

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What to expect next: rollout cadence and lifecycle implications​

• Microsoft’s common pattern is to seed Release Preview for final validation and then move to GA within days to weeks, depending on telemetry and last-minute fixes. The enablement-package approach means devices that adopt 25H2 will continue to receive monthly cumulative updates on the same servicing branch; enterprises should see no change to monthly servicing cadence but should test the first cumulative update after enablement for agent compatibility.
• Publishing the canonical ISO is primarily an operational convenience: it does not negate the eKB upgrade path, nor does it change the recommended production deployment model for already-patched devices (use eKB, pilot, then staged rollout). ISOs remain important for clean installs, golden images, and offline scenarios.

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Conclusion​

Windows 11 version 25H2 is effectively a feature-flip release: Microsoft shipped the major binaries through servicing and provides a small enablement package (KB5054156) to activate the new build identity for up-to-date 24H2 systems, while retaining official Release Preview ISOs for imaging and test purposes. The hybrid model reduces downtime for end users but increases the operational requirement for administrators to validate scripts, agents, and provisioning flows — especially considering the removal of legacy tools such as WMIC and PowerShell 2.0.
Community sightings of ISO files on Microsoft’s distribution servers and a Reddit user extracting direct links are useful signals that media propagation is underway, but organizations should obtain ISOs and eKB packages through the official Windows Insider ISO page or Microsoft Update Catalog and always verify hashes. Treat early Release Preview media as a final validation step in a controlled pilot — not a wholesale production rollout trigger — and prioritize compatibility checks for automation and security tooling before broad deployment.

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Source: Neowin Download links for Windows 11 25H2 ISOs now available before official Microsoft release

 

[ChatGPT]

Microsoft has quietly made the full installation ISOs and the enablement package (eKB) for Windows 11, version 25H2 available to testers and administrators — a move that signals the update is in its final validation window and is likely to begin broader distribution soon.

Background​

Microsoft seeded Windows 11, version 25H2 to the Windows Insider Release Preview channel as the 26200 family (initial seed Build 26200.5074) and confirmed that this annual feature update will be delivered as an enablement package (eKB) on devices already running the servicing baseline (24H2). That model means most up‑to‑date devices will switch to 25H2 with a very small download and a single reboot, while the canonical ISO remains necessary for imaging, clean installs, validation, and OEM certification.
This arrangement — feature binaries staged into the servicing stream and activated by an eKB — is now Microsoft’s established pattern for fall refreshes. The immediate practical effect is twofold: users who apply monthly cumulative updates to 24H2 will get a near‑instant activation to 25H2 via the eKB, while administrators and imaging teams can obtain the official ISO for offline work.

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What’s actually available right now​

• Official ISOs for 25H2 — Microsoft has posted Release Preview ISOs for the 26200 build family on the Windows Insider Preview ISO download portal. These files are gated behind the Windows Insider sign‑in and are intended for testers and validation audiences. Reported ISO sizes vary by edition and language (community reports place many x64 ISOs roughly between 5.5 GB and ~7.1 GB).
• Enablement package (eKB) — Windows Update offers a seeker experience for Release Preview Insiders to apply the eKB and flip installed feature binaries from dormant to active, converting a current 24H2 device into 25H2 with minimal downtime. The eKB is the recommended path for most consumer and managed devices that are already fully patched.
• Cumulative updates and preview KBs — Since the Release Preview seed, Microsoft has continued to publish cumulative updates for the 24H2/25H2 servicing baseline (examples include KB5065426 for the September cumulative and KB5065789 delivered as a Release Preview collection for 26100.x and 26200.x families). These cumulative updates are the monthly servicing units that ensure feature binaries are present on disk before the eKB flips them on.

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Build identities and the small print​

Understanding build IDs and KB mappings is essential for precise change control in enterprise environments.

• Windows 11, version 25H2 is associated with the 26200 build family. The initial Release Preview seed was identified as Build 26200.5074.
• Microsoft has continued to ship cumulative updates in parallel for both 24H2 (26100 family) and 25H2 (26200 family). Recent Release Preview cumulative builds have included identifiers such as 26200.6584 and 26200.6713 in the 26200 series. Those cumulative updates show up as KB packages (for example, community and tracking posts list KB5065426 and KB5065789 in September windows flight windows).
• The important operational takeaway: the eKB does not typically contain large runtime binaries; it changes activation state and metadata. The servicing cumulative updates are where the substantive binary changes land and must already be present on device to keep upgrades small and fast.

Note: some community and media posts have observed slight revision differences between the Release Preview ISO builds and the initial Release Preview seed; the build family remains 26200.x and incremental build revisions have been published during the preview window. Treat a specific patch-level build number (for example, .6584 vs .6713) as the practical identifier for your validation targets.

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Why the ISO still matters (even with an eKB model)​

The enablement package dramatically reduces downtime for devices that are already patched — but that convenience doesn’t replace the need for an ISO in professional scenarios:

• OEMs and system builders need the full ISO for preinstallation and certification.
• Imaging and deployment teams (SCCM/MDT, offline Windows Update for Business, custom provisioning pipelines) require a reproducible, offline artifact for golden images.
• Security, EDR, and logging vendors depend on a canonical ISO to reproduce installer‑time telemetry and confirm detection rules.
• Labs and QA teams must exercise first‑boot / OOBE scenarios and provisioning paths that the eKB path does not exercise.

Enterprise validation should therefore include both eKB activation tests and clean‑install tests from ISO media.

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What’s changed in 25H2 that IT teams need to know​

At a glance, 25H2 is an operational, manageability‑focused update rather than a large consumer-facing feature overhaul. Key items highlighted by Microsoft and community coverage include:

• Enablement‑first delivery model — 25H2 is primarily an enablement package on top of the 24H2 servicing baseline. This results in fast, low-downtime upgrades for patched devices.
• Removals and deprecations — shipping images will no longer include PowerShell 2.0 and the classic WMIC (wmic.exe) binary. Organizations still relying on these tools must migrate scripts and automation to PowerShell 5.1 / PowerShell 7+ and to modern CIM/WMI cmdlets (for example, Get‑CimInstance). This is an operationally critical change for automation and systems management.
• New admin controls — a Group Policy / MDM CSP was added to allow Enterprise and Education administrators to remove selected preinstalled Microsoft Store apps during provisioning and imaging. That change matters for controlled images in managed fleets.
• Incremental UI and AI rollouts — consumer‑facing tweaks in Start, File Explorer, Search, and AI/agent based actions have been staged in servicing and may be enabled by 25H2 for eligible systems. Many of these features were already present in the servicing stream; the eKB simply flips them on.

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Known issues and early problems — what to watch for​

Early Release Preview and cumulative update rollouts have uncovered a small set of practical issues worth flagging to admins and testers:

• Patch installation failures for some cumulative KBs — community and support forums have reported installation loops and error codes (for example, 0x800F0991, 0x800F081F and others) with the September cumulative update KB5065426 on some machines. Microsoft Q&A threads and independent outlets recorded cases where updates either failed or stalled; admins should treat new cumulative updates cautiously in large fleets until local pilot results are verified.
• Feature gating and staged rollouts — certain AI or agent experiences are being rolled out gradually and may not be present on all hardware or in all regions even after 25H2 activation. Validation labs should include hardware parity checks for Copilot+ or other hardware‑dependent experiences.
• Imaging / driver compatibility — as always with a new build family, early driver or imaging tool incompatibilities can show up. Test critical drivers (storage, networking, VPN, endpoint security) from the golden‑image path and confirm driver packages across supported SKUs.

If any of these issues affect your early pilots, prepare rollback and mitigation strategies before a broad rollout.

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Practical deployment checklist for IT (prioritized)​

• Build a small pilot group (5–25 machines) and use both the eKB and ISO paths:
• Apply the eKB path to representative patched devices and measure upgrade time, telemetry effects, and user impact.
• Run a parallel clean install from the Insider ISO on identical hardware to validate imaging, OOBE, driver injection, and provisioning flows.
• Verify servicing baseline:
• Confirm machines have the latest cumulative updates for 24H2 (26100.x) that include the feature binaries necessary for 25H2 activation.
• If you use WSUS / WUfB, confirm the relevant packages appear as expected and that your servicing chains match Microsoft’s published deliveries.
• Check automation and scripts:
• Inventory any reliance on PowerShell v2 or WMIC and migrate scripts to PowerShell 5.1/7+ or to CIM‑based cmdlets (for example, replace Get‑WmiObject/WMIC with Get‑CimInstance or CIM cmdlets).
• Update runbooks and automation in SCCM/Intune/MDM accordingly.
• Validate endpoint protection and EDR:
• Confirm vendor support for 26200.x build family and request updated EDR/uninstaller testing if necessary. Reproduce installer-time telemetry with the ISO to confirm detection rules.
• Test Group Policy / MDM CSP changes:
• If you rely on minimizing inbox apps or custom provisioning, test the new administrative CSP that can remove some preinstalled Store packages during imaging.
• Prepare rollback and recovery:
• Ensure image restore points, golden image backups, and recovery media are current. If a cumulative update fails, a tested image or in-place reimage path can be the fastest recovery.
• Verify download and integrity:
• If you use the ISO, verify file hashes before using them in production imaging. Treat publicly shared hashes from third parties with skepticism — generate your own verification as part of the process.

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Step‑by‑step: testing tips for the eKB and the ISO​

• eKB path (recommended for patched devices)
• Enroll one test device in Release Preview (if you’re using the Insider path).
• Ensure the device has the latest cumulative updates for 24H2.
• In Settings > Windows Update, use the seeker experience to download and install the 25H2 optional update.
• Monitor upgrade duration, user prompts, driver reboots, and Windows Update logs (Get-WindowsUpdateLog / Event Viewer).
• Confirm build identity post‑upgrade with winver or systeminfo (should report 26200.x build family).
• ISO path (recommended for imaging, OOBE tests, clean installs)
• Obtain the official Insider ISO from the Windows Insider Preview ISO page (Windows account enrolled in the Insider Program required).
• Validate the ISO hash and create bootable media (8 GB USB recommended).
• Perform both an in-place upgrade and a clean install on lab machines.
• Run imaging tools (SCCM/MDT) and the provisioning flows you use in production.
• Validate first‑boot provisioning, TPM/BitLocker flows, and automated application installs.

Microsoft’s official guidance for using ISOs and for applying Insider builds remains the canonical walkthrough for these actions.

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Risk assessment and recommendations​

• Strengths
• The eKB model is operationally efficient: smaller downloads, reduced downtime, and faster adoption curves for patched clients.
• ISOs are available to allow imaging, validation, and security vendor verification, preserving enterprise control.
• Removal of legacy engines (PowerShell 2.0 / WMIC) is a long‑overdue modernization step that reduces attack surface and encourages modern scripting.
• Risks
• The deprecation of PowerShell 2.0 / WMIC poses immediate migration work for organizations with legacy automation. Failure to address this will lead to script breakage after broad deployment.
• Early cumulative updates (for example, KB5065426) have shown installation problems for some users in preview windows; applying new cumulative updates at scale without staged pilots risks widespread update failures.
• Hardware or driver incompatibilities can surface during the first broad rollouts; these are routine but costly if they occur at scale without a tested rollback plan.
• Mitigations
• Run comprehensive pilots that use both the eKB activation and the full ISO.
• Inventory scripts and automation and assign remediation owners to update PowerShell/WMIC dependencies before mass deployment.
• Have a verified, current image as a fall‑back and ensure WSUS/WUfB distribution is functioning for incremental cumulative packages.

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Timeline and rollout expectations​

Microsoft’s Release Preview activity and the Insider ISO availability put 25H2 in the final phase before general availability. Historically Microsoft finishes the Release Preview funnel and broad GA rollout on or near a Patch Tuesday cadence; community reporting and commentary have suggested a stable GA rollout targeting the October Patch Tuesday window. While some reporters have projected October 14 as a plausible GA date, that is a community expectation rather than a formal Microsoft public release date — official GA scheduling must be confirmed by Microsoft’s public announcement. Treat the Insider ISO availability as an operational signpost: the release is near, but not necessarily final until Microsoft’s GA announcement.

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Final assessment — what this means for Windows environments​

The appearance of both the official ISOs and the eKB for Windows 11, version 25H2 completes a necessary release scaffolding step for enterprises, OEMs, and imaging teams. The enablement-package strategy continues to reduce upgrade friction for end users, while the official ISO is preserved as the authoritative artifact for imaging, certification, and offline testing. For administrators the practical priorities are:

• Inventory and remediate legacy automation (PowerShell v2, WMIC).
• Run disciplined pilots using both the eKB and the ISO, including first‑boot and provisioning tests.
• Validate cumulative updates in controlled rings before broad deployment, because some cumulative KBs have shown installation instability in preview windows.

Organizations that invest the time to pilot and validate will turn Microsoft’s lower‑downtime model into an operational advantage; those that shortcut testing risk avoidable disruption when 25H2 flips across broader fleets.

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Conclusion
Windows 11, version 25H2 is now tangible for testing and validation: insiders can download Release Preview ISOs and use the eKB path to flip their devices to the 26200 build family. The release emphasizes manageability, removes legacy components, and preserves enterprise imaging workflows via the official ISO. Proceed with staged pilots, verify patch and driver compatibility, and prioritize migration off PowerShell v2/WMIC before a broad rollout. The presence of ISOs today means final general availability is likely near, but the exact GA timing remains conditional on Microsoft’s public release plan.

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Source: Thurrott.com Windows 11 Version 25H2 ISOs and eKBs Are Available