Span Timeline Events Agent Skill

Span Timeline Events

The trace view's right panel shows a timeline of events for the selected span. These are OTel span events rendered by app/utils/timelineSpanEvents.ts and the SpanTimeline component.

How They Work

• Span events in OTel are attached to a parent span. In ClickHouse, they're stored as separate rows with kind: "SPAN_EVENT" sharing the parent span's span_id. The #mergeRecordsIntoSpanDetail method reassembles them into the span's events array at query time.
• The timeline only renders events whose name starts with trigger.dev/ - all others are silently filtered out.
• The display name comes from properties.event (not the span event name), mapped through getFriendlyNameForEvent().
• Events are shown on the span they belong to - events on one span don't appear in another span's timeline.

ClickHouse Storage Constraint

When events are written to ClickHouse, spanEventsToTaskEventV1Input() filters out events whose start_time is not greater than the parent span's startTime. Events at or before the span start are silently dropped. This means span events must have timestamps strictly after the span's own startTimeUnixNano.

Timeline Rendering (SpanTimeline component)

The SpanTimeline component in app/components/run/RunTimeline.tsx renders:

• Events (thin 1px line with hollow dots) - all events from createTimelineSpanEventsFromSpanEvents()
• "Started" marker (thick cap) - at the span's startTime
• Duration bar (thick 7px line) - from "Started" to "Finished"
• "Finished" marker (thick cap) - at startTime + duration

The thin line before "Started" only appears when there are events with timestamps between the span start and the first child span. For the Attempt span this works well (Dequeued -> Pod scheduled -> Launched -> etc. all happen before execution starts). Events all get lineVariant: "light" (thin) while the execution bar gets variant: "normal" (thick).

Trace View Sort Order

Sibling spans (same parent) are sorted by start_time ASC from the ClickHouse query. The createTreeFromFlatItems function preserves this order. Event timestamps don't affect sort order - only the span's own start_time.

Event Structure

// OTel span event format
{
  name: "trigger.dev/run",        // Must start with "trigger.dev/" to render
  timeUnixNano: "1711200000000000000",
  attributes: [
    { key: "event", value: { stringValue: "dequeue" } },  // The actual event type
    { key: "duration", value: { intValue: 150 } },         // Optional: duration in ms
  ]
}

Admin-Only Events

getAdminOnlyForEvent() controls visibility. Events default to admin-only (true).

| Event | Admin-only | Friendly name |

|-------|-----------|---------------|

| dequeue | No | Dequeued |

| fork | No | Launched |

| import | No (if no fork event) | Importing task file |

| create_attempt | Yes | Attempt created |

| lazy_payload | Yes | Lazy attempt initialized |

| pod_scheduled | Yes | Pod scheduled |

| (default) | Yes | (raw event name) |

Adding New Timeline Events

• Add OTLP span event with name: "trigger.dev/<scope>" and properties.event: "<type>"
• Event timestamp must be strictly after the parent span's startTimeUnixNano (ClickHouse drops earlier events)
• Add friendly name in getFriendlyNameForEvent() in app/utils/timelineSpanEvents.ts
• Set admin visibility in getAdminOnlyForEvent()
• Optionally add help text in getHelpTextForEvent()

Key Files

• app/utils/timelineSpanEvents.ts - filtering, naming, admin logic
• app/components/run/RunTimeline.tsx - SpanTimeline component (thin line + thick bar rendering)
• app/presenters/v3/SpanPresenter.server.ts - loads span data including events
• app/v3/eventRepository/clickhouseEventRepository.server.ts - spanEventsToTaskEventV1Input() (storage filter), #mergeRecordsIntoSpanDetail (reassembly)