[RKS (rksharma-owg)]

Fixes #6854.

Parallel endpoints can reuse a response model before its discriminator factory exists. The backward-compatible C#/Go response path immediately clones that factory and can throw Sequence contains no matching element.

Initialize the factory signature alongside serialization members before publishing the model. Populate discriminator mappings after property discovery as before. No waits or lifecycle locks are added. The changelog entry remains under Unreleased.

Validation for be0b847e5b0ecfdb2509994fa35e1ccfc870ac0c against main 1b6cb197f1ba48f4298477eaab4e6be73b13294b:

• Local restore, formatting, build and full solution: 3,054 passed, three existing skips.
• .NET/platform checks: five platform binaries, VS Code tests and packaging pass. Controlled C#/Go regressions fail on the untouched baseline and pass on the candidate on Linux, Windows and macOS.
• CodeQL, surface area and supplemental production coverage pass. The coverage check reruns all tests and verifies nonempty production classes in all three reports; upstream's default coverage reports remain empty.
• Integration: 161 cases pass; seven execute and fail under existing documented upstream suppressions, including the Notion/PHP nullability issue tracked in Primitive collection nullability is incompatible with generated non-nullable element types kiota-php#117. These seven are not counted as passing.
• Idempotency: 110 comparisons pass; two execute and fail under existing upstream suppressions (Go/Twitter and Java/Stripe). No matrix cells are skipped.

Existing upstream suppressions and analyzers are unchanged. Approval-held upstream workflows remain separate from completed fork validation.

[Copilot]

Copilot review overview

🟢 Approval recommended

The narrowly scoped lifecycle change preserves existing mapping behavior and is covered by a deterministic regression test.

Review effort: Balanced
Findings: None

What changed in this PR

Moves model factory initialization before model publication to prevent concurrent C#/Go backward-compatible response generation failures.

Changes:

• Initializes factory signatures before shared-model reuse.
• Populates discriminator mappings after property discovery.
• Adds deterministic concurrency regression coverage and changelog documentation.

File	Description
src/​Kiota.Builder/​KiotaBuilder.cs	Fixes concurrent factory availability.
tests/​Kiota.Builder.Tests/​KiotaBuilderTests.ModelFactory.cs	Tests controlled C#/Go interleaving.
CHANGELOG.md	Documents the fix.

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[Copilot]

Copilot review overview

🟢 Approval recommended

The initialization ordering fixes the reported race and is covered by focused concurrency tests.

Review effort: Balanced
Findings: None

[Copilot]

🟢 Approval recommended

The targeted initialization change resolves the race while preserving mapping behavior and includes focused regression coverage.

0 open findings

🧠 Review effort: Balanced

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[RKS (rksharma-owg)]

The failed Notion/PHP job reports StringOrStringArray::setString() receiving array<mixed> where PHPStan expects array<string>|null. This is the collection-nullability issue tracked in microsoft/kiota-php#117; main now includes the scoped workaround from #8377. The same error appeared on both #8347 and #8367. I have not changed their implementations or weakened PHPStan to work around it.

[Copilot]

🟢 Approval recommended

The targeted initialization change addresses the reported race, includes regression coverage, and has no identified blocking issues.

0 open findings

🧠 Review effort: Balanced

[github-actions]

Conflicts have been resolved. A maintainer will take a look shortly.

[Copilot]

🟢 Approval recommended

The targeted initialization change addresses the reported race, with regression coverage for both affected languages and no unresolved findings.

No open issues 🎉

_{Review effort: Balanced}