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Jaeger

Jaeger is the original distributed-tracing UI from Uber. Modern versions (≥ 1.35) accept OTLP/HTTP natively — no collector needed in the middle.

Signals: traces only. Deployment: local (single container). Cost: OSS, no account needed.

Local setup​

The plugin ships a single-container compose file:

cd ~/.hermes/plugins/hermes_otel
docker compose -f docker-compose/jaeger/docker-compose.yaml up -d

Then:

export OTEL_JAEGER_ENDPOINT="http://localhost:4318/v1/traces"
export OTEL_PROJECT_NAME="hermes-otel-jaeger"

UI at http://localhost:16686.

That file runs jaegertracing/all-in-one, the v1 line that ended with 1.76.0. For the OpenTelemetry-Collector-based Jaeger v2 (what the Helm chart deploys) use docker-compose/jaeger-v2/docker-compose.yaml: UI on http://localhost:16696, OTLP/HTTP on http://localhost:4368/v1/traces. Export works the same. On the read side v2 serves only /api/v3/... on the UI port (the classic /api/traces is 404, #245); the dashboard's Jaeger adapter probes once per query URL (the classic /api/services first, which wins when it answers, then /api/v3/services) and speaks whichever API the server has, so a v1 and a v2 entry need the same two keys (endpoint, query_port). The classic API is preferred because Jaeger 1.x's all-in-one also exposes an /api/v3 gateway, with snake_case parameters that differ from v2's. query_api: v1 or v3 on the entry pins it. Verified on 2.21.0 (2026-10-09): search, filters, keyset paging and the trace detail all come from /api/v3/traces.

Multi-backend config​

backends:
  - type: jaeger
    endpoint: http://localhost:4318/v1/traces

What you'll see​

Jaeger shows the plugin's spans as a standard trace tree — the service-map view picks up the parent/child relationships between session, llm, api, and tool spans. Each span's attributes are rendered in the "Tags" panel (a long list with everything the plugin emitted).

Jaeger is not LLM-specific, so:

  • Message content appears as the raw input.value / gen_ai.content.prompt tag rather than pretty-printed.
  • Token counts are tags, not first-class fields — look for gen_ai.usage.input_tokens / llm.token_count.prompt.
  • Tool args / results are JSON in the input.value / output.value tags.

For LLM-native UI, pair Jaeger with a fan-out to Phoenix or Langfuse — see Multi-backend.

Metrics caveat​

Jaeger is traces-only — no OTLP metrics ingest. The plugin auto-detects this and skips the metrics exporter when Jaeger is the only backend.

If you want the plugin's token / tool / cost metrics alongside Jaeger traces, route metrics to a Prometheus-compatible sink via a separate backend entry, or fan out to Phoenix / SigNoz in parallel.

Troubleshooting​

"Spans are arriving but the service-map is empty"

  • Jaeger builds the service-map from service.name on the resource. The plugin sets this from OTEL_PROJECT_NAME. If it's unset, every span ends up on an "unknown-service" node — set the env var and restart.

"OTLP export 404s"

  • Check your Jaeger version. OTLP ingest was added in 1.35. Older Jaegers need the separate jaeger-collector sidecar. The bundled compose uses a modern version.

"The path format looks wrong"

  • Jaeger's OTLP endpoint is /v1/traces (exactly like Phoenix, SigNoz, etc.). If you see /api/traces, you're looking at the query API, not the ingest API. The plugin writes to the ingest endpoint.