Responses API retries reference non-persisted items (store=false) with no way to enable store in .NET SDK

[MMiooiMM]

Summary

When using GitHub.Copilot.SDK for .NET (v0.1.21) with WireApi = "responses", the SDK may retry or continue a session using response item IDs (e.g. rs_...) even though the underlying request is sent with store=false.

Because the .NET SDK does not expose any way to set store=true, this results in unrecoverable 400 errors:

CAPIError: 400 Item with id 'rs_...' not found.
Items are not persisted when `store` is set to false.
Try again with `store` set to true, or remove this item from your input.

At the moment, there is no way for a .NET SDK user to resolve this, even though the error message explicitly instructs to set store=true.

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Environment

• GitHub.Copilot.SDK: 0.1.21
• .NET: net8.0
• Provider: Azure OpenAI
• Wire API: responses
• Model: gpt-5.2-codex
• ReasoningEffort: xhigh

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Root Cause

• The Responses API requires store=true if response items are later referenced (e.g. via retry or continuation).
• The .NET SDK MessageOptions does not expose a Store property:

public class MessageOptions
{
    public string Prompt { get; set; }
    public List<UserMessageDataAttachmentsItem>? Attachments { get; set; }
    public string? Mode { get; set; }
}

• As a result, all requests are effectively sent with store=false.
• The SDK/runtime still retries or chains requests using response item IDs (rs_...), which cannot be resolved.

This creates a hard failure with no user-level workaround.

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[github-actions]

Thank you for opening this issue, @MMiooiMM!

I've labeled this as a bug affecting the sdk/dotnet implementation. Your report is excellent—you've provided clear environment details, root cause analysis, and the specific missing functionality (Store property in MessageOptions).

This is a blocking issue for .NET SDK users working with the Responses API and retries/continuations. The team will review and prioritize accordingly.

AI generated by Issue Triage Agent