Best LLM observability tool for startups

Combined ranking

1. 1
   Langfuse—15 pts

   GPT #1Claude #1Gemini #1

   Best overall balance: quick hosted setup, broad SDK and OpenTelemetry support, strong tracing, sessions, cost tracking, prompt management, and evaluations; the free cloud tier includes 50k units monthly with 30-day access, while MIT-licensed self-hosting preserves an exit path.

   Claude The default startup pick — open-source with a hosted cloud whose free tier (~50k observations/month) covers most pre-scale usage, SDK setup in minutes across Python/JS with decorators or OTel, and it bundles tracing, prompt management, and evals so a small team needs only one tool; hosted cloud means zero ops, self-hosting stays available as an exit ramp. Assumption: team wants breadth over any single best-in-class feature.

   Gemini Near-tied with Helicone for the top spot. It wins for teams needing deep tracing; it offers an outstanding developer experience, combining rich nested traces, prompt management, and evaluations on a generous cloud tier (50k events/month) or via unlimited MIT-licensed self-hosting.

   Where it falls short

   per GPT The two-user free-cloud limit is restrictive, and self-hosting shifts meaningful ClickHouse and platform operations onto the startup.

   per Claude The UI and query ergonomics get sluggish at high trace volume, and advanced evals/playground features push you toward paid tiers — heavy enterprise-scale shops outgrow it.

   per Gemini It requires code-level instrumentation via SDKs or OpenTelemetry, making it more intrusive to implement than a DNS-level proxy gateway.

2. 2
   Helicone—10 pts

   GPT #4Claude #2Gemini #2

   Literally the fastest setup in the category — swap your OpenAI/Anthropic base URL to its proxy and you have logging, cost tracking, and caching with no SDK integration at all; open-source, and the free tier (~10k requests/month) plus usage-based pricing fits pre-revenue startups.

   Gemini Near-tied with Langfuse. It wins for teams needing absolute simplicity; it offers the fastest setup and lowest integration overhead by acting as an LLM API proxy (changing base URL and API key), with a solid free tier and Apache 2.0 self-hosting.

   GPT Near-tie with LangSmith when setup speed outweighs evaluation depth: proxy-based instrumentation can take one endpoint change, and the free plan offers 10,000 requests plus useful latency, cost, session, user, prompt, and gateway visibility.

   Where it falls short

   per GPT Free usage is capped at one seat, 10 logs per minute, and seven-day retention; advanced querying, alerts, and reports require the $79-per-month plan.

   per Claude Proxy-in-the-request-path is the trade-off — it adds a (small) latency/availability dependency on every LLM call, and deep multi-step agent tracing is weaker than span-native tools; teams wanting rich eval workflows need to pair it with something else.

   per Gemini Being proxy-centric makes it poorly suited for capturing deep, non-networked application logic, local function traces, or offline agent steps without manual span instrumentation.

3. 3
   Arize Phoenix—8 pts

   GPT #2Claude #4Gemini #4

   Near-tie with Langfuse for teams prioritizing open standards and evaluation depth; excellent OpenTelemetry-native tracing, agent graphs, experiments, prompt iteration, and evaluators, with a managed free tier covering 25k spans monthly and an open-source local option.

   Claude Fully open-source and free with no gating — pip install and it runs locally or in a notebook, built natively on OpenTelemetry/OpenInference so instrumentation is standard and portable; best-in-class trace visualization and eval tooling for the price of zero.

   Gemini The gold standard for zero-ops local debugging and evaluations, running via a simple terminal command (pip install) inside Jupyter notebooks or local servers. Natively built on OpenTelemetry standards, allowing easy telemetry migrations without vendor lock-in.

   Where it falls short

   per GPT The managed free tier is single-developer, limited to 1 GB and 15-day retention, while self-hosting sacrifices the minimal-ops advantage.

   per Claude Minimal-ops it is not once you leave the laptop — persistent team deployments mean self-hosting it yourself (or moving to paid Arize AX), so it suits teams comfortable running a container over those wanting a managed dashboard.

   per Gemini Lacks a managed, startup-friendly cloud free tier for production logging, forcing teams to choose between the operational overhead of self-hosting or upgrading to the expensive enterprise-oriented Arize Cloud.

4. 4
   LangSmith—6 pts

   GPT #3Claude #3Gemini —

   Fastest path for LangChain or LangGraph applications and still straightforward elsewhere through provider integrations, wrappers, and OpenTelemetry; unusually cohesive tracing, datasets, annotation, evaluation, monitoring, and cost analysis.

   Claude The most polished hosted experience if you're already on LangChain/LangGraph — tracing is automatic with two env vars, and its debugging UX for agent runs is arguably the best available; free developer tier (5k traces/month) is enough to start. Assumption: rank assumes meaningful LangChain-ecosystem usage.

   Where it falls short

   per GPT The card-free developer tier allows only 5,000 traces monthly, collaboration requires a paid shared organization, and useful trace interactions can trigger costlier extended retention.

   per Claude Closed-source with per-seat + per-trace pricing that climbs fast, and it's noticeably less compelling if you don't use LangChain — framework-agnostic teams get less for the lock-in.

5. 5
   Braintrust—3 pts

   GPT #5Claude #5Gemini #5

   Strong choice when observability must feed directly into evaluations and release decisions; it combines easy auto-instrumentation, rich traces, datasets, playgrounds, experiments, 10k monthly scores, unlimited users, and 1 GB of free monthly ingestion.

   Claude Eval-first observability that startups shipping fast actually use to prevent regressions — logging, datasets, and CI-integrated evals in one hosted product with a generous free tier (~1M trace spans), near-tie with Phoenix and W&B Weave for this slot.

   Gemini Extremely powerful for teams focused on rigorous evaluations, regressions, and testing. The free tier is massive (1 million trace spans and 10k scores/month with unlimited users), making it highly collaborative for early-stage prototyping.

   Where it falls short

   per GPT Free retention is only 14 days, custom charts are paid, and overages are usage-billed without a hard spending cutoff.

   per Claude It's evals-with-logging rather than deep production tracing — cost dashboards and infra-level observability are thinner, and pricing jumps steeply once you exceed the free tier.

   per Gemini It is closed-source, has a steep learning curve focused on CI/CD evaluations rather than simple dashboarding, and features a steep price jump (Pro starts at $249/month) once the free limits are exceeded.

6. 6
   Portkey—3 pts

   GPT —Claude —Gemini #3

   Integrates an AI gateway and observability stack with a fast proxy setup. The hosted Developer plan is free forever for up to 10k logs/month and gracefully continues execution (drops logs only) if limits are hit, providing built-in routing, retries, and caching.

   Where it falls short

   per Gemini The advanced UI and control plane features are heavily tied to Portkey's cloud, making it harder to self-host compared to completely open-source alternatives.

Just missed the top 5

By model

Tracked by ModelsAgree · rank 1 = 5 pts … rank 5 = 1 pt · re-polled continuously