Fix FICC tool_calls/tool ordering with approvals and service-managed chat history

[westey-m]

Fixes #7616

Summary

When FunctionInvokingChatClient (FICC) resumes an approval-gated function call in service-managed history mode (a non-empty ConversationId is set), it omits the reconstructed assistant(tool_calls) message (the service already holds it) but still appends the executed tool result to the tail of the outgoing message list. If the caller supplies any message after the ToolApprovalResponseContent on the continuation turn, that trailing message ends up wedged between the service-held assistant(tool_calls) and its tool result:

assistant(tool_calls) -> user(<trailing message>) -> tool(result)

Providers enforcing tool_calls→tool adjacency (e.g. OpenAI) reject this with HTTP 400.

Fix

Instead of always appending the reconstructed tool-call/tool-result messages at the tail, they are now inserted just before any caller-supplied trailing messages, keeping the tool result adjacent to the assistant message that owns the matching tool_call_id:

• ProcessFunctionCallsAsync gains an optional int? insertIndex — when set, results are inserted at that index rather than appended.
• ProcessFunctionApprovalResponses computes the trailing-message count (messages after the last approval-content message) and inserts the reconstructed assistant(tool_calls) + rejected results just before them, returning the running insert index.
• The index is threaded through InvokeApprovedFunctionApprovalResponsesAsync so approved tool results land adjacent to the tool-call.
• Applied to both the streaming and non-streaming approval paths.

When there are no trailing messages the insert position degrades to the original tail-append behavior, so existing scenarios are unaffected. The invoked function still receives the full input (trailing messages remain in context.Messages during invocation; only the result placement changes).

Resulting valid ordering:

assistant(tool_calls) -> tool(result) -> user(<trailing message>)

Tests

Added regression tests (streaming + non-streaming) covering trailing messages after an approval response in both service-managed and client-managed history modes:

• ApprovedResponsesStayAdjacentToToolCallWhenTrailingMessagesPresentWithServiceThreadsAsync
• ApprovedResponsesStayAdjacentToToolCallWhenTrailingMessagesPresentWithClientHistoryAsync

All existing FunctionInvokingChatClient approval tests continue to pass.

Microsoft Reviewers: Open in CodeFlow

CC @jozkee

[Copilot]

Pull request overview

Fixes an ordering bug in FunctionInvokingChatClient when resuming approval-gated tool calls in service-managed history mode (ConversationId set): tool results are now inserted ahead of any caller-supplied trailing messages so providers that require strict assistant(tool_calls) -> tool(result) adjacency don’t reject the request.

Changes:

• Add an insertion-index path for generated tool result messages so they can be placed before trailing caller messages rather than always appended.
• Compute and thread an “approved result insert index” through the approval-response handling (streaming + non-streaming) to keep tool results adjacent to their tool-call.
• Add regression tests for both service-managed and client-managed history modes when trailing messages are present after approval responses.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
src/Libraries/Microsoft.Extensions.AI/ChatCompletion/FunctionInvokingChatClient.cs	Inserts reconstructed tool-call / tool-result messages at the approval anchor (before trailing messages) and threads an insert index through approval execution to preserve tool_calls→tool adjacency.
test/Libraries/Microsoft.Extensions.AI.Tests/ChatCompletion/FunctionInvokingChatClientApprovalsTests.cs	Adds streaming and non-streaming regression tests validating correct tool result placement with trailing messages in both service-managed and client-managed history modes.

[dotnet-comment-bot]

‼️ Found issues ‼️

Project	Coverage Type	Expected	Actual
Microsoft.Extensions.Diagnostics.Testing	Line	99	98.65 🔻
Microsoft.Extensions.Telemetry	Line	93	92.64 🔻
Microsoft.Extensions.AI	Line	89	88.67 🔻
Microsoft.Extensions.AI	Branch	89	88.59 🔻
Microsoft.Extensions.AI.OpenAI	Line	75	62.75 🔻
Microsoft.Extensions.AI.OpenAI	Branch	75	50.26 🔻
Microsoft.Extensions.DataIngestion.MarkItDown	Line	75	4.46 🔻
Microsoft.Extensions.DataIngestion.MarkItDown	Branch	75	0 🔻
Microsoft.Extensions.Diagnostics.ResourceMonitoring	Line	99	96.03 🔻
Microsoft.Extensions.Diagnostics.ResourceMonitoring	Branch	99	92.76 🔻
Microsoft.Extensions.Diagnostics.ResourceMonitoring.Kubernetes	Line	99	97.73 🔻
Microsoft.Extensions.ServiceDiscovery.Dns	Line	75	69.93 🔻
Microsoft.Extensions.ServiceDiscovery.Abstractions	Line	75	42.11 🔻
Microsoft.Extensions.ServiceDiscovery.Abstractions	Branch	75	42.86 🔻
Microsoft.Extensions.ServiceDiscovery	Line	75	67.96 🔻
Microsoft.Extensions.ServiceDiscovery	Branch	75	71.43 🔻
Microsoft.Extensions.ServiceDiscovery.Yarp	Line	75	73.85 🔻
Microsoft.Extensions.ServiceDiscovery.Yarp	Branch	75	70 🔻
Microsoft.Extensions.VectorData.Abstractions	Line	75	37.39 🔻
Microsoft.Extensions.VectorData.Abstractions	Branch	75	22.73 🔻

🎉 Good job! The coverage increased 🎉
Update MinCodeCoverage in the project files.

Project	Expected	Actual
Microsoft.Gen.BuildMetadata	97	100
Microsoft.Gen.MetadataExtractor	57	73
Microsoft.Gen.MetricsReports	67	69
Microsoft.Extensions.AI.Abstractions	82	86
Microsoft.Extensions.AI.Evaluation.NLP	0	78
Microsoft.Extensions.Caching.Hybrid	82	84
Microsoft.Extensions.DataIngestion	75	89
Microsoft.Extensions.DataIngestion.Markdig	75	90
Microsoft.Extensions.Http.Resilience	97	100

Full code coverage report: https://dev.azure.com/dnceng-public/public/_build/results?buildId=1501578&view=codecoverage-tab