hermes-agent/docs/observability/relay-shared-metrics.md

NeMo Relay Shared Metrics

Hermes includes NeMo Relay as a normal runtime dependency on platforms for which Relay publishes a native wheel. The shared-metrics integration is built into Hermes and does not require hermes plugins enable observability/nemo_relay. Hermes remains importable without Relay on other native targets. Those targets use an explicit reduced-capability no-op host: Hermes execution remains available, while Relay scopes, middleware, plugins, and subscribers are unavailable. The hermes-agent[nemo-relay] extra remains as a no-op compatibility alias for existing installation commands.

Hermes requires NeMo Relay 0.6.0 or later within the 0.6 release line. That release establishes the lossless provider-codec contract used for Anthropic Messages, OpenAI Chat Completions, and OpenAI Responses requests.

Runtime Dependency and Data Boundary

Hermes installs the platform-specific nemo-relay native wheel from the bounded >=0.6.0,<0.7 dependency range. The published package is built from the NVIDIA NeMo Relay repository. Unsupported platforms use the explicit no-op runtime described above rather than downloading a different implementation.

When Relay managed execution is active, the provider request and response pass through that native module in the Hermes process so configured interceptors can operate on the real call. This is separate from the shared-metrics data contract. Shared-metrics mode installs no network exporter and its subscriber accepts only the versioned, allowlisted projection described below. Enabling a separately configured rich-observability or dynamic plugin can create a different data path and requires its own policy review.

Collection remains off unless Hermes policy enables it:

telemetry:
  shared_metrics:
    enabled: true

This choice is read from the profile's own config.yaml. A machine-managed configuration overlay cannot enable or disable shared metrics on the profile's behalf.

The existing observability/nemo_relay plugin remains separate. Enable that plugin only for its opt-in rich observability exporters, adaptive execution, or dynamic Relay plugins.

Hermes core owns one Relay host and one isolated Relay session scope per Hermes session. Core lifecycle producers use hermes_cli.observability.relay_runtime to obtain the shared session handle or run Relay scope, LLM, tool, and mark APIs in that session context. New product marks do not require Hermes plugin registration. Shared-metrics marks must still contain only fields approved by the versioned allowlist; the hard dependency does not change the collection or privacy policy.

Current Slices

The current vertical slices record logical model calls and top-level task runs:

Hermes turn, API, and tool hooks
  -> Relay session, task, and LLM lifecycle
  -> Hermes shared-metrics subscriber
  -> SQLite counters
  -> immutable JSON delta package

Hermes sends an empty LLMRequest into the metrics-owned lifecycle. This does not describe the separate managed-execution call through the native runtime documented above. The terminal metrics event contains only bounded model family, provider family, locality, call role, and outcome values. Prompts, responses, exact model IDs, endpoints, errors, session IDs, task IDs, and request IDs are not included in the metrics event or package.

Each task run is a Relay Function scope named hermes.task_run, parented to the owning Hermes session. The start counter contains only bounded execution surface and entrypoint values. The terminal counter contains bounded outcome, end reason, termination status, duration, logical model-call count, terminal tool-call count, and provider-retry count buckets. Retries are additional provider attempts for the same Hermes API request ID; they do not inflate the logical model-call count. Tool calls are deduplicated by their Hermes tool-call ID after a terminal tool result is observed. The outer AIAgent execution boundary closes the task for normal returns, early returns, exceptions, and cancellations. Active task ownership follows the task ID if Hermes rotates its conversation session during context compression.

Local state is written under:

$HERMES_HOME/telemetry/shared_metrics/metrics.sqlite3
$HERMES_HOME/telemetry/shared_metrics/outbox/*.json

The database keeps transactional aggregate and package-outbox state. Package files are immutable delta documents that conform to a closed JSON schema and are written with atomic replacement. Fully packaged aggregate rows and successfully exported package rows and files are retained locally for 30 days. Pending package rows and counters with unexported deltas are never pruned.

Each package contains an install_id generated as a random UUID. Despite the schema field name, its current scope is one HERMES_HOME, so it is more precisely a persistent pseudonymous profile identifier. It is not derived from hardware, account, host, path, or credential data. It remains stable across packages from that profile and can therefore link those local packages. Deleting $HERMES_HOME/telemetry/shared_metrics resets the identifier together with all aggregates and package files.

This slice has no remote-delivery path. A future remote exporter must not reuse the persistent local identifier by default. It requires a separate product and privacy decision covering consent, identity scope, rotation or keyed pseudonymization, reset behavior, retention, and deletion.

Smoke Test

Run a real Hermes CLI turn against the deterministic local model server:

./.venv/bin/python scripts/smoke_nemo_relay_shared_metrics.py

The script uses the installed nemo-relay dependency by default. Pass --relay-python ../nemo-relay/python only when testing a locally built Relay binding.

The smoke verifies the model request reached the local server, model and task counters were stored, one package was exported, and prompt, response, and exact-model canaries are absent from the package.