Show and filter by event group markers

[laurakwhit]

Description & motivation 💭

This PR surfaces event group markers in event details and adds a filter for them on Workflow /history and /timeline.

Event details

• Events with markers get an Event Groups row in the event card (a comma-separated list of the groups the event belongs to).
• Explicit labels (createEventGroup) are decoded through the configured codec. When there's no label payload the marker ID is shown instead.
• Implicit markers use the source event: <signal name> (<event id>) from WorkflowExecutionSignaled, and <update name> (<update id>) from the update's Admitted or Accepted event. Without a name they fall back to the event type, and before the source event loads they fall back to the ID.

Event Groups filter

• A new Event Groups button next to Filter on /history and /timeline. It only is shown when the history has markers.
• Searchable checkbox list with event counts. Rows show up to 100 matches plus anything selected, with a "Showing N of M" note when more exist.
• Filters whole lifecycle rows containing a marked event. Selected groups combine with OR among themselves and with AND against the existing category filter. The JSON view filters individual events the same way.
• The selection is stored in ?groups= (URL-encoded marker keys) and carries over between History and Timeline. Keys not in the current run are ignored, so stale links never empty the view.

How it works

• A per-run registry (event-group-markers.ts) resolves markers into shared entries as events are converted. It handles events arriving out of order from the two-direction history fetch.
• Decoded labels are cached by payload object in a WeakMap, so each label is decoded once per loaded history.
• The grouped event buffer indexes groups as events arrive (event count, first event, lifecycle groups touched). Filtering is one set lookup per row.

A note on dependency updates

• @temporalio/* 1.22 → 1.24 – the first versions with the event-group API.
• nexus-rpc 0.0.2 → 0.0.3 – in devDependencies and peerDependencies since SDK 1.24 requires it.
• The protobufjs override is split by major version – <8 stays pinned to >=7.6.5 <7.7.0 for @grpc/proto-loader and >=8 <9 pins >=8.8.0 <8.9.0 for the SDK.
• Type fixes for proto 1.24 – HistoryEvent omits proto's new attributes field (which names the set attributes field), and the system Nexus demo caller workflow uses a type-only proto import.

Screenshots (if applicable) 📸

Event details	Event Group filter	Event Group filter w/ 100+ groups

Design Considerations 🎨

Testing 🧪

How was this tested 👻

• Manual testing
• E2E tests added
• Unit tests added

Steps for others to test: 🚶🏽‍♂️🚶🏽‍♀️

1. pnpm catalog dev, then run Event marker groups from the catalog.
2. Open the run's /history. Expand an event and check the Event Groups row.
3. Open Event Groups in the filter bar. Search, select one or more groups, and confirm /history, /timeline and the JSON view narrow. Reload, and switch between /history and /timeline`, to confirm the selection persists.
4. Open a run with no markers and confirm the button doesn't appear.

Checklists

Draft Checklist

Merge Checklist

Issue(s) closed

FE-211

Docs

Any docs updates needed?

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Project	Deployment	Actions	Updated
holocene	Ready	Preview	Oct 7, 2026 3:04am UTC