[wangbill (YunchuWang)]

Summary

What changed?

• Traverse CompleteOrchestrationAction.CarryoverEvents through the existing history-event payload mapping and bounded upload runner.
• Apply the existing UTF-8 externalization threshold and MaxPayloadBytes checks to native carryover payloads without changing event identity, order, names, or completion metadata.
• Add 40 regression cases covering all 18 mapped history-event types, ASCII/multibyte boundaries, protobuf round-trip hydration, oversized responses, cancellation, bounded concurrency, drainage, and permanent/transient upload failures.
• Add a release note to CHANGELOG.md.

Why is this change needed?

• Completion carryover events were not collected for externalization, allowing their payloads to bypass both configured size limits and leave a continue-as-new response above the transport bound.
• Oversized carryover payloads must use the existing non-retriable failed-completion conversion rather than remain inline or be abandoned indefinitely.

Issues / work items

• Resolves Azure Blob payload interceptor skips continue-as-new carryover payloads #819.
• Related Fix payload retries and entity cleanup after storage failures #816; inspected but intentionally not included in this fix.

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Project checklist

• Release notes are not required for the next release
  • Otherwise: Notes added to release_notes.md
• Backport is not required
  • Otherwise: Backport tracked by issue/PR N/A (maintainer decision pending)
• All required tests have been added/updated (unit tests, E2E tests)
• Breaking change?
  • If yes:
    • Impact: N/A.
    • Migration guidance: N/A.

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AI-assisted code disclosure (required)

Was an AI tool used? (select one)

• No
• Yes, AI helped write parts of this PR (e.g., GitHub Copilot)
• Yes, an AI agent generated most of this PR

If AI was used:

• Tool(s): GitHub Copilot.
• AI-assisted areas/files: The sidecar payload interceptor, its regression tests, and CHANGELOG.md.
• What you changed after AI output: Agent iteration resolved a nullable boundary-test value and preserved unrelated changelog bytes. No human post-edit or verification is claimed.

AI verification (required if AI was used):

• I understand the code and can explain it
• I verified referenced APIs/types exist and are correct
• I reviewed edge cases/failure paths (timeouts, retries, cancellation, exceptions)
• I reviewed concurrency/async behavior
• I checked for unintended breaking or behavior changes

Human attestations and the backport decision are left for review.

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Testing

Automated tests

• Result: Passed; 99 focused tests, 0 failed, 0 skipped. The extension also builds for all four target frameworks.

dotnet restore .\test\Grpc.IntegrationTests\Grpc.IntegrationTests.csproj --configfile .\nuget.config --verbosity minimal
# Passed; performed after the initial --no-restore attempt reported missing assets (NETSDK1004).

dotnet test .\test\Grpc.IntegrationTests\Grpc.IntegrationTests.csproj --configuration Release --no-restore --filter "FullyQualifiedName~AzureBlobPayloadsSideCarInterceptorTests|FullyQualifiedName~LargePayloadTests|FullyQualifiedName~AutochunkTests" --logger "console;verbosity=minimal" --verbosity quiet
# Passed: 99, Failed: 0, Skipped: 0; includes all 40 new carryover cases.

dotnet build .\src\Extensions\AzureBlobPayloads\AzureBlobPayloads.csproj --configuration Release --no-restore --verbosity quiet
# Passed for netstandard2.0, net6.0, net8.0, and net10.0; 0 errors.
# Existing nullable, obsolete-API, and StyleCop warnings remain.

git --no-pager diff --check
# Passed on the complete patch before committing.

The focused reproduction was also run before the production fix:

dotnet test .\test\Grpc.IntegrationTests\Grpc.IntegrationTests.csproj --configuration Release --no-restore --filter FullyQualifiedName~ShrinksNativeCarryoverAndHydratesAfterProtobufRoundTrip --logger "console;verbosity=minimal" --verbosity quiet
# Failed as expected before the fix: expected 5 carryover uploads, observed 0.
# Passed after the fix as part of the 99-test run above.

The full solution and live Azure/DTS tests were not run.

Manual validation (only if runtime/behavior changed)

• Environment (OS, .NET version, components): Windows, .NET SDK 10.0.403; in-memory payload store and the existing local gRPC integration harness.
• Steps + observed results: Automated checks above, not manual cloud validation:
  1. Five native CarryoverEvents each contain exactly 1 MiB of serialized event input. Their original protobuf response exceeds 4 MiB; externalization uploads all five and reduces it below 4 MiB. Parsing the response from protobuf bytes and hydrating its events through the incoming worker-work-item path restores the complete original response, including event IDs, timestamps, order, names, completion token, version, tags, and continued-as-new status.
  2. ASCII, two-byte characters, and supplementary Unicode characters exercise inclusive threshold/maximum boundaries. A payload one byte above the maximum performs no upload and becomes a non-retriable failed completion.
  3. Gated carryover uploads verify the eight-operation bound, cancellation-token forwarding, stopping queued work, and drainage before return. Permanent 403 failures retain failed-completion conversion; transient 500 failures propagate without replacing the continued-as-new completion.
• Evidence (optional): The original five-event regression failed before the traversal was added. No live Azure Blob Storage or DTS execution is claimed.

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Notes for reviewers

• No breaking change — public/protected APIs, protobuf fields, token format, serializer defaults, and orchestration replay logic are unchanged. The existing inbound history resolver restores externalized values before replay.
• The production change is five lines and uses the same history-event mapping already used for rewind history. The shared concurrency runner and storage-failure conversion are unchanged.
• Adjacent Fix payload retries and entity cleanup after storage failures #816 remains open. Its retry-idempotency, entity-cleanup, and worker-preparation changes are deliberately outside this PR.
• Release notes are recorded in the existing CHANGELOG.md; this repository does not have the template's release_notes.md.

[Copilot]

🟢 Approval recommended

There are no active review issues for the carryover payload externalization change.

No open issues 🎉

What changed in this PR

Fixes #819 by including native continue-as-new carryover payloads in Azure Blob externalization, reusing the SDK’s existing size checks and bounded upload handling.

Changes:

• Processes completion carryover events through the existing history-event payload mapping.
• Adds 40 regression cases covering payload mappings, UTF-8 size boundaries, round-trip hydration, concurrency, cancellation, and failure handling.
• Adds an unreleased changelog entry; related #816 changes remain out of scope.

File	Description
test/​Grpc.IntegrationTests/​AzureBlobPayloadsSideCarInterceptorTests.cs	Adds carryover externalization and hydration regression coverage.
src/​Extensions/​AzureBlobPayloads/​Interceptors/​AzureBlobPayloadsSideCarInterceptor.cs	Includes carryover history events in the bounded externalization runner.
CHANGELOG.md	Documents the carryover payload fix.

_{Review effort: Balanced}