Observability

Glue writes spans and debug events to local JSONL files, and can also export the same spans to any OTLP/HTTP-compatible collector (Phoenix, Tempo, Jaeger, Honeycomb, etc.).

Debug Logging

Toggle verbose logging during a session with /debug, or start with --debug / GLUE_DEBUG=1. Span records are written to daily JSONL files in ~/.glue/logs/spans-YYYY-MM-DD.jsonl.

TIP

Debug logging is useful for inspecting prompt assembly, tool calls, and token usage. Use jq or grep on the JSONL files to slice the stream.

Local JSONL schema

Each span is serialized with snake_case keys:

{
  "trace_id": "...",
  "span_id": "...",
  "parent_span_id": "...",
  "name": "llm.stream",
  "kind": "llm",
  "start_time": "2026-04-19T12:00:00.000Z",
  "end_time": "2026-04-19T12:00:01.234Z",
  "duration_ms": 1234,
  "attributes": {}
}

OpenTelemetry export

When an OTLP endpoint is configured, the same spans are forwarded to a collector via an OtlpHttpTraceSink. Spans flush every 5 seconds while a session is running.

Configure under observability.otel in ~/.glue/config.yaml:

observability:
  debug: false
  max_body_bytes: 65536
  redact: true
  otel:
    enabled: true
    endpoint: https://app.phoenix.arize.com/s/your-space
    headers:
      Authorization: Bearer <token>
    service_name: glue
    resource_attributes:
      openinference.project.name: glue

Supported config keys

Key	Type	Notes
observability.otel.enabled	boolean	Defaults to on when an endpoint is set and OTEL_SDK_DISABLED ≠ 1
observability.otel.endpoint	string	OTLP/HTTP traces endpoint
observability.otel.headers	map	Sent on every export request (auth tokens, project headers)
observability.otel.service_name	string	Defaults to glue
observability.otel.resource_attributes	map	Merged into the OTLP Resource block

Environment-variable fallbacks

If a key is not set in config.yaml, Glue reads the standard OTEL env vars:

Setting	Environment variables (first match wins)
Endpoint	OTEL_EXPORTER_OTLP_TRACES_ENDPOINT, OTEL_EXPORTER_OTLP_ENDPOINT, PHOENIX_COLLECTOR_ENDPOINT
Headers	OTEL_EXPORTER_OTLP_TRACES_HEADERS, OTEL_EXPORTER_OTLP_HEADERS, PHOENIX_API_KEY
Service name	OTEL_SERVICE_NAME
Resource attrs	OTEL_RESOURCE_ATTRIBUTES, PHOENIX_PROJECT_NAME
Master kill switch	OTEL_SDK_DISABLED=1 disables export even when an endpoint is set

PHOENIX_PROJECT_NAME, when set, is mapped to the openinference.project.name resource attribute (and a default of glue is applied if nothing else provides one) so traces show up under the expected Phoenix project.

A richer per-session event schema (messages, tool calls, runtime events) is being introduced separately — see the session JSONL schema plan.

See also

• ObservabilityConfig
• DebugController
• FileSink