Surface inbound AG-UI CUSTOM events as metadata instead of dropping them#694
Surface inbound AG-UI CUSTOM events as metadata instead of dropping them#694PratikDhanave wants to merge 2 commits into
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Pull request overview
This pull request updates the AG-UI provider’s event-to-response mapping so inbound CUSTOM AG-UI events are no longer silently dropped, and become observable to callers as response/message metadata.
Changes:
- Handle
*aguiEvents.CustomEventin(*toolCallAccumulator).onEventby emitting a metadata-onlyResponseUpdatecontainingAdditionalProperties["agui_custom_event"]. - Add an integration-style SSE test to verify a CUSTOM event is surfaced into collected response messages.
Reviewed changes
Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.
| File | Description |
|---|---|
| provider/aguiprovider/agui.go | Adds a CustomEvent case that converts inbound CUSTOM frames into a metadata-only assistant update. |
| provider/aguiprovider/agui_test.go | Adds a test that streams a CUSTOM event and asserts it is surfaced via AdditionalProperties["agui_custom_event"]. |
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| case *aguiEvents.CustomEvent: | ||
| return []*agent.ResponseUpdate{{ | ||
| Role: message.RoleAssistant, | ||
| CreatedAt: eventTime(evt), | ||
| AdditionalProperties: map[string]any{ | ||
| "agui_custom_event": map[string]any{ | ||
| "name": e.Name, | ||
| "value": e.Value, | ||
| }, | ||
| }, | ||
| }}, nil |
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Good catch — fixed in 77bdb0a: each custom event now gets a unique synthetic MessageID (agui-custom-<n>) so it forms its own message instead of being merged into the last assistant message. This stops multiple custom events from overwriting each other under the shared agui_custom_event key via maps.Copy, and keeps them off unrelated assistant content. Added a black-box test that fails without the fix.
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The AG-UI event accumulator dropped decoded CUSTOM events: onEvent had no case for *events.CustomEvent, so every CUSTOM frame fell through to the default arm and was silently discarded. Emit a metadata-only assistant ResponseUpdate carrying the event name and value under AdditionalProperties["agui_custom_event"], matching how the .NET and Python AG-UI clients expose custom events to callers rather than swallowing them.
Custom events previously emitted a ResponseUpdate with no MessageID, so they were merged into the last assistant message. Because Response.Update uses maps.Copy for AdditionalProperties, multiple custom events in a stream overwrote each other under the shared agui_custom_event key and attached to unrelated assistant content. Assign each custom event a unique synthetic MessageID so it forms its own message and is preserved.
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Cross-repo parity review — PR #694Scope: Upstream reference: Parity issues found1.
|
| SDK | Key used |
|---|---|
| Go (this PR) | "agui_custom_event" |
| Python | "ag_ui_custom_event" |
Python uses ag_ui_ (matching the "AG-UI" protocol) while Go uses agui_. Callers that introspect AdditionalProperties cross-SDK will need different key spellings. The Go key should be "ag_ui_custom_event" to stay consistent.
2. thread_id / run_id not included in Go custom-event response
Python's _handle_custom_event always populates thread_id and run_id in additional_properties alongside the custom-event payload (these are tracked state on the converter). The Go implementation omits them, so consumers of the custom-event update lose correlation context they get from the Python SDK.
3. raw_type field not present in Go
Python records the original event type string (raw_event_type) as "raw_type" in the custom event's metadata object. This allows callers to distinguish between CUSTOM and CUSTOM_EVENT spellings at runtime. The Go path handles only *aguiEvents.CustomEvent (a single typed variant) so there may not be an equivalent distinction, but if there is, it should be surfaced for parity.
Upstream Python surface: microsoft/agent-framework → python/packages/ag-ui/agent_framework_ag_ui/_event_converters.py → _handle_custom_event
Recommend aligning the Go key name to "ag_ui_custom_event" and adding thread_id/run_id correlation fields to match Python semantics before merging.
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| MessageID: fmt.Sprintf("agui-custom-%d", a.customSeq), | ||
| CreatedAt: eventTime(evt), | ||
| AdditionalProperties: map[string]any{ | ||
| "agui_custom_event": map[string]any{ |
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Parity issue — key name diverges from Python SDK
The upstream Python _handle_custom_event uses "ag_ui_custom_event" (with underscore after ag) as the additional_properties key. This PR uses "agui_custom_event" (no underscore). Callers inspecting AdditionalProperties cross-SDK will need different spellings.
Suggested rename to "ag_ui_custom_event" to match microsoft/agent-framework → _event_converters.py.
| CreatedAt: eventTime(evt), | ||
| AdditionalProperties: map[string]any{ | ||
| "agui_custom_event": map[string]any{ | ||
| "name": e.Name, |
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Parity issue — missing thread_id/run_id correlation fields
The Python _handle_custom_event includes thread_id and run_id in the additional_properties alongside the custom-event payload (they are tracked state in the converter). Go omits them, so consumers of this update lose run-correlation context that Python callers receive.
Consider adding the AG-UI thread/run IDs here to keep observability parity with the Python SDK.
What
The AG-UI event accumulator in
provider/aguiprovider/agui.gosilently dropped inboundCUSTOMevents.(*toolCallAccumulator).onEventhad no case for*events.CustomEvent, so a decoded CUSTOM frame fell straight through to thedefault:arm and returnednil, nil— the event never reached the caller even though the decoder handled the CUSTOM wire type without error.This adds a case that emits a single metadata-only assistant
ResponseUpdate(noContents) with the event surfaced underAdditionalProperties["agui_custom_event"]as{name, value}. The existingrun()loop already lazily initializesAdditionalPropertiesand injectsagui_thread_id, so the update flows through unchanged.Why
CUSTOM is a first-class AG-UI event type used for application-specific signals (e.g.
predictive_state). The .NET and Python AG-UI clients expose custom events to callers rather than discarding them; dropping them here is a cross-SDK parity gap. Surfacing them as message metadata keeps them out of the assistant text/content stream while still making them observable to consumers.How tested
Added
TestAGUIAgentRun_SurfacesCustomEventAsMetadatainagui_test.go: anhttptestSSE server emitsNewCustomEvent("predictive_state", WithValue(map[string]any{"foo":"bar"})), the agent runs, and the test asserts one collected message carriesAdditionalProperties["agui_custom_event"]with the expected name and value map. The test fails before the fix (no such update is emitted) and passes after.go build ./...,go vet ./provider/aguiprovider/..., andgo test ./provider/aguiprovider/...all pass.