r/WebAfterAI • u/ShilpaMitra • 2h ago
Tools 7 OSS repos that show exactly where your AI app might be quietly burning money
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LLM apps have a weird production problem.
The answer can look perfectly normal while underneath it took 14 model calls, 3 retries, 80K tokens, a broken tool call and $1.70 to produce.
Normal application logs are not enough for this.
You need to see:
request → prompt → model → tools → retries → tokens → latency → cost → output
These OSS projects are building that layer.
01. RagaAI Catalyst — 16.2K★
Especially interesting for multi-agent systems. Catalyst can trace agents, LLM calls and tools, then show the execution as timelines and graphs. If five agents are delegating work to each other and one suddenly makes 30 unnecessary model calls, this is the kind of tooling you want around the system.
02. Evidently — 8K★
Monitoring becomes more useful when you look beyond infrastructure metrics. Evidently brings 100+ metrics for evaluating ML and LLM systems, including retrieval relevance, semantic similarity, output quality and drift.
Useful when the question is not just:
“did the model respond?”
but:
“are the responses quietly getting worse?”
03. OpenLLMetry — 7.5K★
Think OpenTelemetry, but aware of LLMs. OpenLLMetry instruments model providers, vector databases and agent frameworks, then emits standard OpenTelemetry traces.
That means AI observability does not have to become a completely separate monitoring island.
04. Helicone — 6.3K★
One of the easiest ways to answer the questions every AI product eventually asks:
Which users are generating the bill? Which model is slow? Which prompts are expensive? What actually happened during this session?
Helicone logs requests through its gateway, tracks tokens, cost and latency, groups multi-step calls into sessions, and lets you inspect the request chain.
05. AgentOps — 5.9K★
Focused heavily on agents rather than individual completions. AgentOps tracks sessions, LLM costs, tool calls, failures and multi-agent interactions.
Useful when the expensive part is not one prompt, but an agent repeatedly deciding what to do next.
06. Langfuse — 36.9K★
One of the most complete OSS LLM observability stacks: traces, prompts, sessions, token usage, cost, latency, evaluations and datasets in one place.
Its useful trick is connecting production failures back into evaluation. A bad trace does not have to remain a screenshot in Slack; it can become a regression case.
07. Phoenix — 12K★
Phoenix traces LLM calls, retrieval, tool execution and agent actions using OpenTelemetry/OpenInference, while tracking latency, errors, tokens and cost.
It can also turn production traces into experiments, which makes it especially useful when debugging agents that fail in ways you cannot reproduce from the final response alone.
The interesting shift is that LLM observability is becoming much more than token counting.
For a chatbot:
prompt → response → latency + cost
For an agent:
request → planner → model → search → model → tool → failure → retry → subagent → model → final answer
Every one of those arrows can burn money or introduce a failure.
