Questions on Upgrade Path from Pega 24.1.1 to Future Pega 26 Release

Hi Team,

Please note that Pega 26 has not been released yet. This is a proactive initiative to help us prepare and understand the potential upgrade path and associated considerations.

We are currently running a large enterprise application on Pega Platform 24.1.1 using UI Kit and are planning the following upgrade path:

24.1.1 → Latest 25.x Patch → 26

We would appreciate guidance on the following questions:

1. Is Pega recommending customers upgrade to the latest 25.x patch before moving to 26, or will there be a supported direct upgrade path from 24.1.1 to 26?

2. For customers remaining on UI Kit:

  • Will UI Kit continue to be fully supported on Pega 26?

  • Are there any known limitations, restrictions, or deprecation plans?

3. Is it recommended to run the Constellation Modernization Assessment even if there is no immediate plan to migrate to Constellation?

  • What value does it provide during upgrade planning?

4. Can Upgrade Impact Analyzer be executed from the current 24.1.1 environment against a future target version (25.x/26)?

  • What is the recommended approach?

5. With Infinity Studio becoming the primary development experience, what is the recommended development approach for UI Kit applications after upgrading to 25.x or 26?

6. Are there any known upgrade considerations for applications using:

  • Pega Customer Service

  • Knowledge Management

  • SRS/Search

  • Email Channels

  • Interaction Portals

7. Have customers experienced any issues related to:

  • PDF generation

  • Styling

  • Document rendering

during upgrades from 24.x to 25.x or 26, particularly for applications with customized PDF frameworks?

8. What are the recommended pre-upgrade and post-upgrade validation activities for:

  • SRS

  • Elasticsearch-based search

9. For applications with custom JavaScript, custom sections, custom harnesses, and custom CSS:

  • Which areas typically require the most remediation after upgrading to 25.x or 26?

10. For organizations that have already upgraded UI Kit applications from 24.x to 25.x or are participating in early adoption programs for 26:

- What were the top challenges encountered?

- What best practices helped reduce upgrade effort and risk?

Any guidance, lessons learned, recommendations, or references to relevant documentation would be greatly appreciated.

Thank you.

Pega recommends upgrading to the latest patch of the immediately previous major release whenever practical because because you get cumulative fixes, schema improvements,engine fixes and reduced number of upgrade jumps. However, if it will be a hectic and lengthy approach for your organization, you can directly upgrade from 24.1.1 to 26 once the documentation is released.

Pega’s current messaging has consistently been that UI Kit is supported but Constellation is the strategic direction. I would expect that UI Kit will still be supported with limited new UI features as the current engineering investment is completely focused on Constellation and long-term migration is encouraged.

Yes, even if Constellation migration is months or years away, it gives technical debt visibility, remediation planning and upgrade risk indicators. The assessment will provide custom controls inventory,custom sections,custom harnesses,unsupported controls,JavaScript inventory,CSS inventory,deprecated controls and estimated modernization effort.

Once 26 is released, Upgrade Imapct Analyzer will likely receive updated rules and datasets.I would not expect today’s 24.1.1 UIA to understand 26 before 26 ships. However, you can run it against 25.x.
Before upgrading, run UIA against latest supported version(25.x) and remediate warnings, rerun after upgrading and rerun once 26 support is added.

For UI Kit applications:

  • continue maintaining rules in Dev Studio where needed
  • use Infinity Studio where supported
  • do not rewrite UI solely because Studio exists
  • gradually adopt Studio for supported rule types

For 6-
For Customer Service, I will proabably go with verifying interaction portals,mashups,CTI,widgets,service cases and agent desktop.

For Knowledge Management, Verify - search, categories, article rendering, attachments, publishing workflow

For SRS, Validate - indexing,queue processors,indexing jobs,search latencynode communication

For Email Channels, Validate - OAuth,listeners,email routing,attachments,HTML rendering

For Interaction Portal, Verify- custom sections,gadgets,mashups,composite portals,custom widgets

These tend to be common regression areas.

7. Typical issues after upgrades include CSS differences,fonts,spacing,page breaks,barcode rendering,image scaling,merged PDFs and third-party library compatibility especially if using custom HTML,custom CSS,Apache FOP,iText integrations and PDF templates.

Regression testing should compare pixel-level output where possible.

8. SRS validation

Pre-upgrade:

node health
indexing backlog
document count
search latency
replication status

Post-upgrade:

full reindex (if recommended)
compare document counts
execute representative searches
validate faceted search
monitor indexing throughput
review logs for indexing failures

Elasticsearch validation:

If still applicable in your deployment:

Verify:

cluster health
shard allocation
index size
mappings
search response time
failed indexing jobs

(Note that newer Pega deployments emphasize Search and Reporting Service (SRS), so the exact validation depends on your architecture.

9. Historically these consume most upgrade effort.

High-risk areas include:

JavaScript - DOM selectors,custom events,deprecated APIs,inline scripts

Sections - deprecated controls,visibility conditions,layouts,dynamic containers,Harnesses,custom headers,custom portals,custom navigation

CSS - overridden skin styles,responsive layouts,z-index,Bootstrap conflicts,Custom controls

These often require the highest remediation effort.

10. Organizations upgrading large UI Kit applications to 24.x and 25.x have generally reported these challenges:

  • custom JavaScript regressions
  • deprecated controls
  • portal customizations
  • search configuration
  • PDF rendering differences
  • third-party integrations
  • custom authentication
  • browser compatibility
  • skin overrides
  • performance regressions

thanks for the generic answers , looking for specific answers , if anyone has already started their journey towards upgrading to 26 , trying to understand challenges faced and lessons learnt