Sync vector store dimensions with embedding output across upstream and dotnet parity

[Copilot]

Description

This PR pulls in the upstream 3502c22 behavior change and applies the matching functionality to the C# codebase. It also audits the dotnet implementation against the recent Python changes and closes the only remaining parity gap in this area: vector-store dimensions drifting from the actual embedding model output.

Related Issues

Addresses the upstream sync and C# parity audit work for recent GraphRAG changes.

Proposed Changes

• Upstream merge

  • Apply the Python validate_config.py change from upstream so embedding validation now captures the embedding response and realigns vector_store.vector_size and index schema dimensions to the detected embedding width.
  • Add the corresponding semversioner patch metadata from upstream.

• Dotnet parity

  • Add GraphRagConfig.SyncVectorStoreDimensions(...) to update vector-store dimensions when the configured embed-text model returns a different embedding width.
  • Add VectorStoreConfig.WithVectorSize(...) and IndexSchema.WithVectorSize(...) so dimension updates propagate consistently through the immutable dotnet config model.

• Audit follow-up

  • Update the upstream sync note for 3502c222 to document the parity decision and resulting dotnet implementation.
  • Confirm there were no other missed Python changes after the last sync beyond this vector-size alignment behavior.

Example of the new dotnet parity surface:

var updatedConfig = config.SyncVectorStoreDimensions(
    embeddingModelId,
    new LlmEmbeddingResponse([[1.0f, 2.0f, 3.0f]])
);

Checklist

• I have tested these changes locally.
• I have reviewed the code changes.
• I have updated the documentation (if necessary).
• I have added appropriate unit tests (if applicable).

Additional Notes

The dotnet implementation does not have a direct equivalent of Python's validate_config.py, so the parity change is implemented at the configuration-model layer instead of in CLI validation flow. This keeps the change minimal while preserving the same functional outcome once embedding dimensions are known.

---

💡 You can make Copilot smarter by setting up custom instructions, customizing its development environment and configuring Model Context Protocol (MCP) servers. Learn more Copilot coding agent tips in the docs.

[Copilot]

Pull request overview

This PR syncs vector-store dimensions to the actual embedding model output, matching upstream behavior in Python and adding equivalent parity support in the dotnet immutable configuration layer.

Changes:

• Python: capture the embedding probe response during config validation and realign vector_store.vector_size + index schema vector sizes to the detected embedding width.
• Dotnet: add GraphRagConfig.SyncVectorStoreDimensions(...) plus WithVectorSize(...) helpers on VectorStoreConfig and IndexSchema, with unit tests covering the copy/sync behavior.
• Docs/metadata: update the upstream sync note for 3502c222 and add semversioner patch metadata.

Reviewed changes

Copilot reviewed 9 out of 9 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
packages/graphrag/graphrag/index/validate_config.py	Sync Python vector store and index schema dimensions to detected embedding width during validation.
dotnet/src/GraphRag/Config/Models/GraphRagConfig.cs	Add SyncVectorStoreDimensions API to return an updated config when embedding width differs.
dotnet/src/GraphRag.Vectors/VectorStoreConfig.cs	Add WithVectorSize helper to update vector size and propagate to schema.
dotnet/src/GraphRag.Vectors/IndexSchema.cs	Add WithVectorSize helper to update schema vector dimension immutably.
dotnet/tests/GraphRag.Tests.Unit/Vectors/VectorStoreConfigTests.cs	Unit test VectorStoreConfig.WithVectorSize updates copy and synchronizes schema.
dotnet/tests/GraphRag.Tests.Unit/Vectors/IndexSchemaTests.cs	Unit test IndexSchema.WithVectorSize returns updated copy without mutating original.
dotnet/tests/GraphRag.Tests.Unit/Config/GraphRagConfigMethodTests.cs	Unit tests for GraphRagConfig.SyncVectorStoreDimensions matching/mismatch/empty-response cases.
docs/upstream-sync/upstream-3502c222.md	Document manual review results and dotnet parity approach for this upstream change.
.semversioner/next-release/patch-20260315024056229023.json	Add patch note for the vector-size reconfiguration behavior.