Add EventCompaction support to EventActions and compaction filtering in contents_processor.go

[yashrajshuklaaa]

Is your feature request related to a specific problem?

Yes. I'm working on adding compaction support to kagent's Go ADK runtime to match the existing Python ADK behavior. The Go ADK has no compaction primitives at all
I checked every released version from v0.1.0 to v1.4.0.
EventActions has no Compaction field and contents_processor.go has no filtering step for compaction markers.
Without these primitives , after a compaction runs the raw events stay in the backing store and get re-sent to the LLM on every subsequent request, which defeats the purpose of compaction entirely.

Proposed Solution

Three things need to be added to mirror what Python ADK already does in events/event_actions.py, apps/compaction.py and flows/llm_flows/contents.py -

• An EventCompaction struct in session/session.go carrying the compacted time range and compacted content

• A Compaction field on EventActions to hold the marker

• Compaction filtering in internal/llminternal/contents_processor.go when building LLM contents raw events whose timestamps fall within a compaction marker's range should be replaced by the marker's compacted content

Impact on your work

This is blocking a PR I have open at kagent (#1971) to add Go-runtime compaction. The kagent maintainer specifically pointed out that without these primitives the implementation cannot match Python ADK semantics. Compaction is important for long-running agents so the sooner the better though no hard deadline.

Willingness to contribute

Yes happy to submit a PR
Just wanted to check with maintainers first before touching core session and flow internals.

Additional Context

Related downstream PR: kagent #1971
this is what is blocked on this feature.

[yashrajshuklaaa]

@wolo-lab PTAL

[indurireddy-TF]

Hi @yashrajshuklaaa Thank you for submitting this. This is a valid enhancement request.
Without these changes, raw events are not filtered in contents_processor.go and continue to be sent to the LLM, which defeats the purpose of the compaction feature. @kdroste-google @baptmont @karolpiotrowicz any thoughts on this when you have a moment?

[QuentinBisson]

I've implemented this in a fork and have a working reference if it helps move a PR forward.

Fork: https://github.com/QuentinBisson/adk-go/tree/feat/event-compaction

What's in the diff:

• session/session.go: EventCompaction struct (StartTimestamp, EndTimestamp, CompactedContent *genai.Content) + Compaction *EventCompaction field on EventActions
• internal/llminternal/contents_processor.go: applyCompaction pass in buildContentsDefault — collects active (non-subsumed) compaction markers, replaces events in each compacted range with the summary content, hides the marker events themselves

The pass runs after transcription aggregation and before the async-function-response rearrangement step. Subsumed compactions (where a later compaction's range fully contains an earlier one) are silently dropped.

Downstream: kagent PR kagent-dev/kagent#2025 uses this via a replace directive and is tested against Anthropic and OpenAI. Happy to open a PR here based on this if useful.