34b475e2ce
#116713 parsed HERMES_LANGFUSE_MAX_DEPTH inside `_safe_value`, i.e. once per captured prompt, response, tool input and tool output. With an invalid value (`abc`) every captured field logged the same "Invalid ... Falling back to 4" WARNING for the life of the process — one multi-tool turn fills agent.log. Resolve the depth in `_resolve_max_depth`, an lru_cache keyed on the raw env string: the warning fires once per distinct bad value, a changed env var is still picked up by a long-lived process (mirrors `_capture_mode`, which also reads per call and warns once), and valid values skip the int() parse after the first call. Follow-up to #116713 (independent review finding).
Langfuse Observability Plugin
This plugin ships bundled with Hermes but is opt-in — it only loads when you explicitly enable it.
Enable
Pick one:
# Interactive: walks you through credentials + SDK install + enable
hermes tools # → Langfuse Observability
# Manual
pip install langfuse
hermes plugins enable observability/langfuse
Required credentials
Set these in ~/.hermes/.env (or via hermes tools):
HERMES_LANGFUSE_PUBLIC_KEY=pk-lf-...
HERMES_LANGFUSE_SECRET_KEY=sk-lf-...
HERMES_LANGFUSE_BASE_URL=https://cloud.langfuse.com # or your self-hosted URL
Without the SDK or credentials the hooks no-op silently — the plugin fails open.
Verify
hermes plugins list # observability/langfuse should show "enabled"
hermes chat -q "hello" # then check Langfuse for a "Hermes turn" trace
Generation observations include the Hermes system prompt when the provider
uses a separate system param (Anthropic Messages API). Open an LLM call
child span to inspect role: system (truncated via HERMES_LANGFUSE_MAX_CHARS).
Optional tuning
HERMES_LANGFUSE_ENV=production # environment tag
HERMES_LANGFUSE_RELEASE=v1.0.0 # release tag
HERMES_LANGFUSE_SAMPLE_RATE=0.5 # sample 50% of traces
HERMES_LANGFUSE_MAX_CHARS=12000 # max chars per field (default: 12000)
HERMES_LANGFUSE_MAX_DEPTH=4 # max payload depth (default: 4)
HERMES_LANGFUSE_CAPTURE=sanitized # content capture mode (see below)
HERMES_LANGFUSE_DEBUG=true # verbose plugin logging
HERMES_LANGFUSE_MAX_DEPTH controls nested payload capture in both sanitized
and full modes, including tool arguments and JSON tool results. The root is
depth 0; each dictionary value or array element adds one level. Values beyond
the limit become <max-depth>, including scalars. For deeper MCP responses,
set it to a higher non-negative integer (for example, 10) in the Hermes
process environment. Unset or blank values default to 4; invalid or negative
values log a warning and fall back to 4. 0 keeps only the root level.
Increasing the depth exports more content and may produce larger traces;
secret redaction, string-length limits, and the 50-item collection limit remain
unchanged. metadata mode still omits content.
Capture modes
HERMES_LANGFUSE_CAPTURE controls how much content (prompts, responses,
tool arguments/results) is exported. Structural metadata — IDs, roles, tool
names, token usage, cost, timing — is always captured in every mode.
| mode | behavior |
|---|---|
metadata |
No content. Each content field is replaced by a shape/size stub ({"omitted": true, "type": "text", "chars": N}). |
sanitized |
(default) Content is exported after secret-pattern redaction (API keys, tokens, JWTs, private keys, password=-style assignments) and truncation. Redaction runs before truncation. |
full |
Raw content, truncated only. Explicit opt-in — traces will contain whatever passed through the conversation, including injected memory and file contents. |
The active mode is recorded on every trace as metadata.capture_mode.
Note: sanitized is pattern-based defense in depth, not a DLP guarantee.
For personal sessions or shared Langfuse projects, prefer metadata.
Error + shutdown coverage
- Failed model requests (
api_request_errorhook) close their generation withlevel=ERROR, status code, retry counters, and a capture-mode-scrubbed error message. Non-retryable failures also finish the turn trace. - Session end/finalize closes any still-open traces for that session and flushes queued events, so interrupted or tool-only turns don't dangle.
Disable
hermes plugins disable observability/langfuse