on_post_llm_call extracted usage via `if response is not None:`, taking the
response-object path. But post_api_request delivers `response` as a sanitized
dict (no `.usage` attribute) alongside a separate `usage` summary dict, so
`getattr(response, "usage")` was always None and token/cost data was dropped
for every gateway turn (traces showed usage 0 / cost 0).
Gate on a real `.usage` attribute so the existing usage-dict fallback is
reached. Real response objects (post_llm_call / legacy) still take the
response-object path. Adds regression tests for both paths.
* fix(langfuse): reject placeholder credentials with one-shot warning
When operators leave HERMES_LANGFUSE_PUBLIC_KEY / HERMES_LANGFUSE_SECRET_KEY
at a template value like 'placeholder', 'test-key', or 'your-langfuse-key',
the Langfuse SDK silently accepts the credentials at construction time and
drops every trace at flush time. No warning, no error — just an empty
Langfuse dashboard the operator only notices hours later.
Add prefix-based validation in _get_langfuse() against the documented
'pk-lf-' / 'sk-lf-' prefixes that Langfuse always issues server-side.
Anything else fires a single warning naming the offending env var(s)
with a log-safe value preview (full string for short placeholders so the
operator knows which template they left in place; truncated for long
values so a real secret pasted into the wrong field never hits the log),
then short-circuits via the existing _INIT_FAILED cache so the warning
fires once per process, not once per hook invocation.
The check sits after the 'Langfuse is None' SDK-installed guard so hosts
without the optional langfuse SDK don't see misleading 'set real keys'
hints when the actionable fix is 'pip install langfuse'. Missing
credentials remains the documented opt-out path and stays silent — no
log noise for unconfigured installs.
Fixes#22763Fixes#23823
* fix(langfuse): use actual API request messages for generation input
on_pre_llm_request previously used the messages kwarg alone, which
could be None when Hermes passes the payload via request_messages,
conversation_history, or user_message instead. Add _coerce_request_messages
to pick the first available list across all variants, falling back to a
synthetic user message. Generations now show the real outbound payload
rather than an empty input.
* fix(langfuse): record tool call outputs in traces
Tool observations showed input (arguments) but output was always
undefined. Root cause: when tool_call_id is empty, pre_tool_call stored
observations under a unique time-based key that post_tool_call could
never reconstruct, so every tool span was closed without output by the
_finish_trace sweep.
Fix pre/post matching by routing empty-tool_call_id tools through a
per-name FIFO queue (pending_tools_by_name) instead of the time-based
key. Tools with a tool_call_id continue to use the id-keyed dict.
Also:
- Preserve OpenAI-style nested function shape in serialized tool calls
so Langfuse renders name/arguments correctly
- Keep name + tool_call_id on role:tool messages for proper pairing
- Backfill tool results onto the matching turn_tool_calls entry so the
generation's tool-call record carries the result alongside arguments
- Coerce request messages from whichever field the runtime provides
(request_messages, messages, conversation_history, user_message)
* fix(langfuse): salvage-review polish — drop dead is_first_turn, shallow-copy request_messages, real threaded FIFO test
Self-review of the combined #22345 + #23831 salvage surfaced three issues
worth fixing in the same PR rather than as follow-ups:
1. Drop is_first_turn from the pre_api_request hook. The boolean expression
`not bool(conversation_history)` was wrong: conversation_history is
reassigned to None mid-run after compression (5 sites in run_agent.py),
so the value flips False -> True mid-conversation on every post-compression
API call. The langfuse plugin never consumed it, so the kwarg was both
misleading AND dead.
2. Replace copy.deepcopy(request_messages) with shallow list() copy. The
pre_api_request hook contract discards return values (invoke_hook never
writes back to api_kwargs), and the langfuse plugin's _serialize_messages
already builds its own snapshot dicts via _safe_value. A deepcopy on every
API call would walk every tool result and base64 image — significant
overhead for no real isolation benefit. Shallow copy of the outer list
protects against later mutations of api_messages without paying for the
inner-dict walk.
3. Rename test_empty_tool_call_id_concurrent_fifo_order ->
test_empty_tool_call_id_observations_are_fifo_within_tool_name and add a
real test_threaded_post_calls_preserve_fifo_under_lock that spawns 8
threads behind a barrier to actually exercise _STATE_LOCK on the
pending_tools_by_name queue. The original test was sequential and only
validated Python list semantics; this one validates the lock discipline.
4. Fix stale 'Cleared by reset_cache_for_tests()' comment on _INIT_FAILED —
that function does not exist. Tests reload the module via sys.modules.pop
+ importlib.import_module instead.
Tests: 37 langfuse plugin tests pass, 658 plugin tests overall pass.
---------
Co-authored-by: xxxigm <tuancanhnguyen706@gmail.com>
Co-authored-by: Brian Conklin <brian@dralth.com>
Opt-in Langfuse tracing for Hermes conversations — LLM calls, tool
usage, usage/cost breakdown per span. Hooks into pre/post_api_request,
pre/post_llm_call, pre/post_tool_call. SDK is optional; missing SDK or
credentials renders the plugin inert.
Salvaged from PR #16845 by @kshitijk4poor, who wrote the plugin
(~875 LOC, 6 hooks, Langfuse usage-details/cost-details normalization,
read_file payload summarization).
Salvage scope (why this isn't PR #16845 as-authored):
- Lives at plugins/observability/langfuse/ (standalone kind, opt-in via
plugins.enabled) instead of a new parallel optional-plugins/
directory. Standalone bundled plugins are already opt-in — only their
plugin.yaml is scanned at startup; the Python module is not imported
unless the user enables it. The premise of optional-plugins/ (avoid
import cost for users who don't want it) is already solved by the
existing plugin system.
- Dropped the triple activation gate (plugins.enabled +
plugins.langfuse.enabled + HERMES_LANGFUSE_ENABLED). The Hermes plugin
system's own enable/disable is authoritative; runtime credentials
gate whether the hook actually traces.
- Rewrote _is_enabled() → cached _get_langfuse() with an _INIT_FAILED
sentinel. The original called hermes_cli.config.load_config() from
every hook invocation (full yaml parse + deep merge + env expansion
on every pre/post_tool_call, potentially 100+ times per turn). The
cached version reads env once and returns the cached client or None
on every subsequent call with zero further work.
- hermes tools → Langfuse Observability post-setup adds
observability/langfuse to plugins.enabled directly (via
_save_enabled_set) instead of going through an install-copy flow.
Enable:
hermes tools # interactive
hermes plugins enable observability/langfuse # manual
Required env (set by `hermes tools` or in ~/.hermes/.env):
HERMES_LANGFUSE_PUBLIC_KEY
HERMES_LANGFUSE_SECRET_KEY
HERMES_LANGFUSE_BASE_URL # optional
Co-authored-by: kshitijk4poor <kshitijk4poor@gmail.com>
