generated: '2026-08-13'
method: searched
source: https://experienceleague.adobe.com/en/docs/marketo/using/release-notes/current
docs: https://experienceleague.adobe.com/en/docs/marketo/using/release-notes/current
scheme: monthly named release
current: August 2026 release
current_release_date: '2026-08-14'
page_last_updated: '2026-08-10'
note: >-
  Marketo Engage ships a dated monthly release note rather than a per-version API
  changelog. There is no separate developer changelog and no RSS/Atom feed; API
  behaviour changes appear in the "Announcements" section of the product release
  note, mixed in with UI features. That placement is the finding — four of the
  five API-affecting changes below, including two breaking ones, are announced
  nowhere an integrator would be watching. Recent window only; the live page is
  the source of truth.
entries:
  - version: August 2026
    date: '2026-08-14'
    rollout: Phased through August 2026; feature availability varies by edition.
    breaking:
      - id: access-token-parameter-removal
        summary: >-
          The `access_token` query parameter used to authenticate REST API calls
          is deprecated and will not be available after 2026-08-31. Callers must
          use the `Authorization` header.
        effective: '2026-08-31'
        affects: every REST operation
      - id: static-list-size-limit-activities
        summary: >-
          From 2026-09-30, Get Lead Activities and Get Lead Changes calls that
          include a `listId` fail with error 1003 when the target static list
          contains 10,000 or more leads.
        effective: '2026-09-30'
        affects: [getLeadActivitiesUsingGET, getLeadChangesUsingGET]
      - id: merge-leads-25-id-limit
        summary: >-
          As of 2026-07-31, Merge Leads calls with more than 25 IDs in `leadIds`
          return error 1080 and are skipped.
        effective: '2026-07-31'
        affects: [mergeLeadsUsingPOST]
    fixes:
      - id: campaign-run-id-formatting
        summary: >-
          Campaign Run ID on an activity was sometimes returned double-quoted
          ("campaignRunId": ""102938""). From the August release it is always
          returned as a number.
        affects: [getLeadActivitiesUsingGET]
    additions:
      - summary: >-
          Marketo Engage New UI — refreshed interface, menus, icons and layout.
          Visual only; no functional or workflow change.
        status: Phased rollout throughout August 2026
      - summary: Email Designer Script Builder — AI-assisted personalization script authoring.
        status: Coming soon
      - summary: >-
          Disable Campaigns on Archive — archiving a folder now disables and
          deschedules every campaign in that folder tree.
        status: Coming soon
  - version: July 2026
    date: '2026-07-31'
    breaking:
      - id: soap-api-retired
        summary: >-
          The SOAP API is deprecated and no longer available. All development
          moves to the REST API.
        effective: '2026-07-31'
        source: https://experienceleague.adobe.com/en/docs/marketo-developer/marketo/rest/rest-api
related:
  lifecycle: lifecycle/marketo-lifecycle.yml
  errors: errors/marketo-error-codes.yml
  rate_limits: rate-limits/marketo-rate-limits.yml