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AdditionalPropertiesAllowed is not serialized into additionalProperties even when explicitly set to false #2664

Closed as duplicate
Closed as duplicate
AdditionalPropertiesAllowed is not serialized into additionalProperties even when explicitly set to false#2664
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Description

@shazamViz
shazamViz
opened on Dec 30, 2025

Describe the bug

When generating an OpenAPI document using Microsoft.OpenApi, setting
OpenApiSchema.AdditionalPropertiesAllowed = false does not result in
additionalProperties: false being emitted in the generated OpenAPI document.

As a result, it is currently impossible to generate a "closed" object schema
(using additionalProperties: false) through the public API, even though
AdditionalPropertiesAllowed exists on OpenApiSchema.

This leads to incorrect OpenAPI output and breaks downstream tools such as
NSwag, OpenAPI Generator, Kiota, etc.

Expected behavior

When AdditionalPropertiesAllowed is explicitly set to false, the generated
OpenAPI should contain:

additionalProperties: false

Activity

  1. baywet commented on Jan 5, 2026

    @baywet
    Vincent Biret (baywet)
    on Jan 5, 2026
    Member

    Hi shazamViz
    Thank you for using the SDK and for reaching out.

    What version of the library are you using? could you please double check you're on the latest version for that major?

    We had a very similar issue a couple of weeks ago which was fixed and relased:

    Let us know if you have any additional comments or questions.

  2. Vincent Biret (baywet)
    added
    status:waiting-for-author-feedbackIssue that we've responded but needs author feedback to close
    on Jan 5, 2026

  3. shazamViz commented on Jan 6, 2026

    @shazamViz
    shazamViz
    on Jan 6, 2026
    Author

    Hi,

    Thanks for your answer and sorry for not specifying which version I was using.
    I was using v2.3.12 (released on december 15) for compatibility purpose with Microsoft.AspNetCore.OpenApi v10.0.1, I missed december 16 and december 17 upgrades, it's working as expected with the latest version.

  4. microsoft-github-policy-service
    added
    Needs: Attention 👋
    and removed
    status:waiting-for-author-feedbackIssue that we've responded but needs author feedback to close
    on Jan 6, 2026

  5. baywet commented on Jan 6, 2026

    @baywet
    Vincent Biret (baywet)
    on Jan 6, 2026
    Member

    Thank you for the additional information.
    Closing

  6. Vincent Biret (baywet)
    closed this as a duplicateof Explicit additionalProperties: false should be emitted in OpenAPI 3.1 when AdditionalPropertiesAllowed = false #2646 on Jan 6, 2026
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