[dotnet-port-api] Add compaction-backed history provider

[Michelle Clayton (michelle-clayton-work)]

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The original pull request description is below.

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Summary

Add a compaction-backed history provider in agent/compaction so Go agents can apply reducer-triggered history compaction directly on the history-provider surface instead of only through a separate context provider. The change adds the new provider, covers compacted persistence and summary replay in tests, updates the additional-context sample to use the new API, and refreshes the parity doc to reflect the reduced .NET chat-history gap.

Ported .NET PRs

• None — this is a Go misalignment realignment for the documented .NET chat-history reducer-trigger capability. The local parity baseline tracks .NET commit 5996105a1bf2726918101adc6e9c9857b7f68b98, with workflow/test delta previously checked through 6a0773ba2180e8036d138dbb9794ae64ec2d978b.

Breaking Changes

No.

Tests and Examples

• go test ./agent ./agent/compaction ./examples/02-agents/agents/step17_additional_ai_context
• Added agent/compaction/historyprovider_test.go
• Updated examples/02-agents/agents/step17_additional_ai_context/main.go

Notes

• The live upstream-agent-framework/main fetch was blocked in this environment, so this PR ports the documented chat-history parity gap as a narrow Go realignment instead of tying the change to a freshly inspected upstream PR.
• Other broader chat-history/storage parity gaps remain out of scope for this PR.

Closes #1053

[Copilot]

🟡 Changes recommended

Two critical correctness issues remain in the history provider.

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Pull request overview

Adds a compaction-backed history provider with persistence, tests, an updated example, and refreshed .NET parity documentation.

Changes:

• Adds compaction.NewHistoryProvider.
• Adds compaction persistence and summary replay tests.
• Updates the additional-context example.
• Refreshes the .NET/Go feature comparison.

File summaries

File	Summary
examples/02-agents/agents/step17_additional_ai_context/main.go	Uses the new bounded history provider.
docs/dotnet-go-sdk-feature-comparison.md	Updates chat-history parity status.
agent/compaction/historyprovider.go	Implements persisted compaction. Critical issues remain around including current input before compaction and applying filters before generated summaries; a concurrency test is also needed.
agent/compaction/historyprovider_test.go	Tests compacted persistence and summary replay.
agent/compaction/doc.go	Documents history-provider support.

Review details

Suppressed comments (1)

agent/compaction/historyprovider.go:146

• This provider rewrites shared session state after appending and compacting each turn, but the new tests only exercise sequential Invoked calls. The existing in-memory provider has a same-session concurrent store/race test (agent/history_test.go:80-118); add the analogous test here with a real truncation strategy to verify that concurrent turns are not lost while compaction runs.

			compacted, err := compactHistory(ctx, cfg.Strategy, messages, cfg.TokenCounter, cfg.Logger)

• Files reviewed: 5/5 changed files
• Comments generated: 2
• Review effort level: Lite

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[Michelle Clayton (michelle-clayton-work)]

Copilot address PR feedback

[Copilot]

Copilot address PR feedback

Addressed the review feedback in 941efbc: pre-call compaction now includes filtered persisted history plus the current request exactly once, and filtering occurs before summarization. Added regression coverage for both cases.

[github-actions]

Generated by Go API Consistency Review Agent for #1092 · copilot · auto · 117 AIC · ⌖ 6.8 AIC · ⊞ 9.6K

[Michelle Clayton (michelle-clayton-work)]

Copilot address PR feedback

[Copilot]

Copilot address PR feedback

Addressed the remaining review feedback in b591a02: history compaction now runs at one configurable lifecycle point, defaulting to before retrieval, with an after-message-added option. Added coverage for both modes and updated the bounded-storage sample.

[Michelle Clayton (michelle-clayton-work)]

Copilot fix merge conflicts

[Copilot]

Copilot fix merge conflicts

Resolved the merge conflict with current main in merge commit 9ae6e8e. The obsolete feature-matrix edit was dropped in favor of main’s new symbol-mapping guide, while the provider implementation, tests, and sample remain intact. Targeted race tests and CodeQL pass.

[github-actions]

API consistency review

Result	Scope
aligned	public API, user-visible behavior, examples

Changed Go contract

New exported compaction.NewHistoryProvider, HistoryProviderConfig, and HistoryProviderTriggerEvent (BeforeMessagesRetrieval by default, or AfterMessageAdded). The step17_additional_ai_context example now uses this provider.

Upstream evidence reviewed

Implementation	Source	Contract checked
.NET	InMemoryChatHistoryProviderOptions.cs (ReducerTriggerEvent, ChatReducerTriggerEvent)	The default trigger is BeforeMessagesRetrieval. AfterMessageAdded is the other option.
.NET	InMemoryChatHistoryProvider.cs (ProvideChatHistoryAsync, StoreChatHistoryAsync)	The reducer runs on retrieval or after messages are stored, according to the trigger.
.NET	Compaction/CompactionProvider.cs	Upstream compaction strategies are exposed as an AI context provider.

I did not review the Python sources. I searched only .NET, and only main.

Assessment

The trigger names, the default (BeforeMessagesRetrieval), and the trigger semantics match the upstream in-memory history provider's reducer trigger. The strategy machinery is the existing compaction pipeline. The Go provider is opt-in, so no defaults change for existing users.

One difference is worth a maintainer's look, but I don't treat it as a finding. In BeforeMessagesRetrieval mode, .NET writes the reduced messages back to session state. Go compacts a copy for retrieval only, and Invoked then appends to the uncompacted stored history. Observable prompts should match, but stored session state grows until an AfterMessageAdded trigger is used. Strategies like summarization may also re-run on each retrieval.

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Generated by Go API Consistency Review Agent for #1092 · copilot · auto · 28.7 AIC · ⌖ 9.73 AIC · ⊞ 13.8K · ◷