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Release record

macOS 15.8

macOS Sequoia 15.8 is a point release on the legacy macOS 15 train. It entered release-candidate testing on August 17, 2026 and had not reached general availability on that date. Apple's release notes describe it as providing important security fixes recommended for all users.

Full article
Cycle active
Latest milestone
RC 2
Last recorded
Aug 24, 2026
Forecast status
Anomaly
Recorded milestones
2

Forecast window passed

Public release not recorded

Anomalous delay

Expected Aug 27, 2026 – Aug 28, 2026

Historical median
Aug 28, 2026
Comparable cycles
3
Label agreement
100%

Forecast paused: the expected next milestone window passed without a recorded milestone. This is anomalous against recent comparable Apple release cycles, though rare historical exceptions exist; it does not mean the release is cancelled or that the public release is late. A newer milestone is needed before publishing another estimate.

Why this is marked anomalous

15.8 has gone 22 days since RC 2. In 3 comparable cycles, the middle half reached the next milestone 3–4 days later (median 4). The expected window ended Aug 28, 2026.

This flags a late next milestone, not a late public release. The comparable public-release window still runs Aug 27, 2026 – Aug 28, 2026 (median Aug 28, 2026).

Rare historical exceptions are documented in the forecast methodology.

View all forecasts →Read the methodology →

Release notes

Overview

Editorial synthesis with inline references and a source ledger when citations are available.

macOS Sequoia 15.8 entered release-candidate testing on August 17, 2026 as build 24H16. Apple followed with RC 2 build 24H20 on August 24, advancing the numeric portion of the build by four over seven days.[1][2]

Both records are prerelease appearances. Apple had not listed macOS Sequoia 15.8 as a public security release as of August 29, so the archive does not assign a public release date or infer security contents from the candidate label.[3][4]

Source ledger

References

Sources are linked to the claims they support. Publication and access dates are shown when available.

  1. Second Release Candidates for macOS Tahoe 26.7 and macOS Sequoia 15.8 now available

    9to5Mac · 2026-08-24T00:00:00Z · macOS Sequoia 15.8 RC 2, build 24H20, August 24, 2026

    Back to text ↑
  2. Apple rolls out macOS Tahoe 26.7 and macOS Sequoia 15.8 RCs

    9to5Mac · 2026-08-17T00:00:00Z · macOS Sequoia 15.8 release candidate, build 24H16, August 17, 2026

    Back to text ↑
  3. Apple security releases

    Apple Support · Apple · 2026-07-27T00:00:00.000Z · Apple security releases table reviewed August 29, 2026; no macOS Sequoia 15.8 public row

    Back to text ↑
  4. Second Release Candidates for macOS Tahoe 26.7 and macOS Sequoia 15.8 now available

    9to5Mac · 2026-08-24T00:00:00Z · RC 2 distribution and build number

    Back to text ↑
  5. Apple Releases macOS 27 Beta 6, Plus Release Candidates for Tahoe and Sequoia [Download]

    iClarified · 2026-08-17T00:00:00Z · macOS Sequoia 15.8 (24H16); release candidate, August 17, 2026

  6. Apple rolls out macOS Tahoe 26.7 and macOS Sequoia 15.8 RCs

    9to5Mac · 2026-08-17T00:00:00Z · macOS Sequoia 15.8 (24H16); release candidate, August 17, 2026

  7. Second Release Candidates for macOS Tahoe 26.7 and macOS Sequoia 15.8 now available

    9to5Mac · 2026-08-24T00:00:00Z · macOS Sequoia 15.8 RC 2, build 24H20

  8. Apple rolls out macOS Tahoe 26.7 and macOS Sequoia 15.8 RCs

    9to5Mac · 2026-08-17T00:00:00Z · macOS Sequoia 15.8 RC, build 24H16

Milestones

Release history

Every recorded channel appearance in chronological order. Open an appearance for any available build, scope, notes, and sources.

  2. +7 days

    Release candidate

    RC 2

    Full articleEditorially verified

    Apple seeded macOS Sequoia 15.8 RC 2 on August 24, 2026 as build 24H20, seven days after the first candidate build 24H16. This is a prerelease appearance, not a public release, and no detailed change list accompanied the report.

    Build
    24H20
    Availability
    available
    Sources
    5 linked
    Open this appearance

Historical context

Cycle comparison

Pace, intervals, and duration compared with earlier releases on the same platform.

Historical avg for .8 releases

160 days, 2.0 milestones

Based on 1 previous macOS .8 releases

22 days since last beta

Gaps this long have happened 11 times

Most recently: macOS 26.3 had a 28-day gap (Beta 1 → Beta 2)

Pace at day 29

2 milestones (avg: 1.0)

Ahead of pace — previous .8 releases averaged 1.0 milestones at this point

Previous .8 releases (macOS)

Previous comparable macOS releases
VersionYearCycleMilestonesAvg. Interval
macOS 10.82012160d2160d

Scroll horizontally to compare every historical field.