ClickStack Demo Day (2026-08-28) - Span links, in both directions

Span links were only usable from the consumer side. A span showed the links it carries as bare "Open trace" actions, and there was no way to start from a producer span and find the spans that link back to it. A user asked for exactly that in a GitHub issue. The Span Links section now resolves each link's target and shows the span name, service, duration and timestamp instead of a bare action, which matters as soon as a span carries more than one link. Open trace remains the fallback when the target can't be found. A new "Linked from" section lists the spans whose links reference the selected span, with the same navigation as forward links. Navigation is breadcrumb-aware. Following a link back to the span directly behind you in the stack pops back to it rather than pushing a duplicate, so you can move between two spans without the stack growing forever. If something sits between them, the entry is added as normal. The reverse lookup finds the row whose span links contain the selected span id, then confirms the trace id. Trace-id lookups are fast because of the bloom filter index on that column, but this one scans, so a much larger traces table may be slower. An index on the link span id is the obvious optimization if it turns out to need one. Part of the ClickStack Demo Day series. See the full post at https://clickhouse.com/docs/use-cases/observability/clickstack/demo-days/2026/2026-08-28