The Rust side has Langfuse tracing already (gateway/v1/langfuse_trace.rs);
this commit lands Go-side parity so the multi-coord stress harness can
emit traces visible at http://localhost:3001.
internal/langfuse/client.go:
- Minimal Trace + Span + Flush API mirroring what the Rust emitter
uses. Auth: Basic over public_key:secret_key.
- Best-effort posture: errors are slog.Warn'd, never block calling
paths. Same fail-open as observerd's persistor (ADR-005 Decision
5.1) — observability is a witness, not a gate.
- Events buffered until 50, then auto-flushed; explicit Flush() at
process exit.
- Each Trace/Span returns its id so callers can build hierarchies.
multi_coord_stress driver wiring:
- New --langfuse-env flag (default /etc/lakehouse/langfuse.env).
Empty / missing / unparseable file → skip tracing with a logged
warning; run still proceeds.
- Phase 1c (inbox burst) now emits one parent trace + 4 spans per
inbox event:
1. observerd.inbox.record (post to /v1/observer/inbox)
2. llm.parse_demand (qwen2.5 → structured fields)
3. matrix.search (parsed query → top-K)
4. llm.judge_top1 (rate top-1 vs original body)
Each span carries input/output JSON + start/end times so the
Langfuse UI shows a full waterfall per event.
Run #009 result:
Trace landed: "multi_coord_stress phase 1c inbox burst"
Observations attached: 24 (= 6 events × 4 spans)
Tags: stress, phase-1c, inbox
Browseable at http://localhost:3001 by tag query.
Other harness metrics: diversity 0.016, determinism 1.000,
verbatim handover 4/4, paraphrase handover 4/4 — all unchanged
by the tracing addition (best-effort post in parallel).
Phase 1c is the proof-of-concept; future commits can wrap other
phases (baseline / merge / handover / split) in traces too. Once
that's done, the entire stress run becomes scrubbable in Langfuse
without grepping the events JSON.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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