Migrate Application Customizer tutorial series to heft build system

[Ashlesha-MSFT]

Category

• Content fix

Related issues

• fixes SPFx Docs Update for Heft toolchain: build-a-hello-world-extension.md #10573
• fixes SPFx Docs Update for Heft toolchain: using-page-placeholder-with-extensions.md #10574
• fixes SPFx Docs Update for Heft toolchain: serving-your-extension-from-sharepoint.md #10575
• fixes SPFx Docs Update for Heft toolchain: hosting-extension-from-office365-cdn.md #10576

What's in this Pull Request?

Migrate Application Customizer tutorial series to heft build system

• Updated build-a-hello-world-extension.md with heft commands
• Updated using-page-placeholder-with-extensions.md with heft commands
• Removed gulp-to-heft migration WIP banners from both files
• Updated dates to 01/12/2026
• Changed gulp serve to heft start
• Updated prose text references from 'Gulp' to 'Heft'
• Removed outdated note about alias length validation

These changes complete the migration of the Application Customizer Hello World tutorial series (parts 1 & 2) from gulp to the heft build system (SPFx v1.22+).

[learn-build-service-prod]

PoliCheck Scan Report

The following report lists PoliCheck issues in PR files. Before you merge the PR, you must fix all severity-1 and severity-2 issues. The AI Review Details column lists suggestions for either removing or replacing the terms. If you find a false positive result, mention it in a PR comment and include this text: #policheck-false-positive. This feedback helps reduce false positives in future scans.

✅ No issues found

More information about PoliCheck

Information: PoliCheck | Severity Guidance | Term
For any questions: Try searching the learn.microsoft.com contributor guides or post your question in the Learn support channel.

[learn-build-service-prod]

Learn Build status updates of commit f3badd1:

✅ Validation status: passed

File	Status	Preview URL	Details
docs/spfx/extensions/get-started/build-a-hello-world-extension.md	✅Succeeded	View
docs/spfx/extensions/get-started/using-page-placeholder-with-extensions.md	✅Succeeded	View

For more details, please refer to the build report.

[learn-build-service-prod]

PoliCheck Scan Report

The following report lists PoliCheck issues in PR files. Before you merge the PR, you must fix all severity-1 and severity-2 issues. The AI Review Details column lists suggestions for either removing or replacing the terms. If you find a false positive result, mention it in a PR comment and include this text: #policheck-false-positive. This feedback helps reduce false positives in future scans.

✅ No issues found

More information about PoliCheck

Information: PoliCheck | Severity Guidance | Term
For any questions: Try searching the learn.microsoft.com contributor guides or post your question in the Learn support channel.

[learn-build-service-prod]

Learn Build status updates of commit df4c02b:

✅ Validation status: passed

File	Status	Preview URL	Details
docs/spfx/extensions/get-started/build-a-hello-world-extension.md	✅Succeeded	View
docs/spfx/extensions/get-started/serving-your-extension-from-sharepoint.md	✅Succeeded	View
docs/spfx/extensions/get-started/using-page-placeholder-with-extensions.md	✅Succeeded	View

For more details, please refer to the build report.

[learn-build-service-prod]

PoliCheck Scan Report

The following report lists PoliCheck issues in PR files. Before you merge the PR, you must fix all severity-1 and severity-2 issues. The AI Review Details column lists suggestions for either removing or replacing the terms. If you find a false positive result, mention it in a PR comment and include this text: #policheck-false-positive. This feedback helps reduce false positives in future scans.

✅ No issues found

More information about PoliCheck

Information: PoliCheck | Severity Guidance | Term
For any questions: Try searching the learn.microsoft.com contributor guides or post your question in the Learn support channel.

[learn-build-service-prod]

Learn Build status updates of commit 2a739a5:

✅ Validation status: passed

File	Status	Preview URL	Details
docs/spfx/extensions/get-started/build-a-hello-world-extension.md	✅Succeeded	View
docs/spfx/extensions/get-started/hosting-extension-from-office365-cdn.md	✅Succeeded	View
docs/spfx/extensions/get-started/serving-your-extension-from-sharepoint.md	✅Succeeded	View
docs/spfx/extensions/get-started/using-page-placeholder-with-extensions.md	✅Succeeded	View

For more details, please refer to the build report.