LLM observability pack: free tracing plans for Langfuse, PostHog, LangSmith and more

Once an LLM app or agent leaves your laptop, you need to see what it actually did: which prompts went out, what came back, how long each step took and where it failed. Almost every tracing and eval tool has a free plan for that, but each one counts usage differently: units, events, spans, base traces, requests, logs, gigabytes or credits. This new pack collects 14 of those offers in one place.

Eleven are free plans that need only a signup. Three are startup deals with their own eligibility rules. Two of the free plans are new on Perq today: Langfuse Hobby and PostHog's free allowance, which includes AI observability events. Every row was checked on the vendor's own page; each card shows the quote and when we last verified it.

LLM observability pack

The offers

• Langfuse (Hobby plan: 50k units / month included, free (no card))
• PostHog (Monthly free allowance on every product: 1M analytics events, 5K session recordings, 1M feature flag requests, 100K AI observability events)
• LangChain (LangSmith) (Developer plan $0: up to 5k base traces/month)
• Helicone (10,000 free requests/month)
• Comet (Opik) (Free cloud plan: 25k spans per month, up to 10 team members)
• Traceloop (Free forever: up to 50K spans/month)
• Laminar (Free: 1 GB of trace data, 7-day data access, 1 project)
• Pydantic Logfire ($20/month of free usage (10 million spans, logs or metrics) on every plan)
• Arize AI (AX Free: 25k trace spans and 1 GB ingestion per month, 15-day retention, unlimited users)
• Portkey (Developer plan free forever: 10k recorded logs per month)
• Braintrust ($10 credits/month included on Starter ($0))
• Langfuse (50% off entire Langfuse bill for 12 months)
• LangChain (LangSmith) ($10K in LangSmith credits available for 1 year)
• Braintrust (Pro plan free for 6–12 months)

New today

Langfuse (Hobby plan: 50k units / month included, free (no card))

PostHog (Monthly free allowance on every product: 1M analytics events, 5K session recordings, 1M feature flag requests, 100K AI observability events)

What each free plan gives you

• Langfuse Hobby: 50k units / month, 30 days of data access and 2 users, with no credit card required.
• PostHog: the free allowance renews every month and covers every product, including 100K AI observability events. Useful if you already use PostHog for product analytics and want LLM traces next to it.
• LangSmith Developer: up to 5k base traces per month for a solo user.
• Helicone Hobby: 10,000 free requests per month.
• Opik (Comet): 25k spans per month with 60-day retention and up to 10 team members; Opik can also be self-hosted.
• Traceloop: up to 50K spans per month and 5 seats, but only 24 hours of data retention.
• Laminar: 1 GB of trace data, 7-day data access and 1 project.
• Pydantic Logfire: every plan includes $20 of free usage a month (10 million spans, logs or metrics); the Personal plan is hard-capped at $0.
• Arize AX Free: 25k trace spans and 1 GB ingestion per month, 15-day retention, unlimited users.
• Portkey Developer: 10k recorded logs per month on its AI gateway; requests keep working past the limit, they just aren't recorded.
• Braintrust Starter: $10 credits / month included on a $0 plan.

Startup deals

• LangSmith for startups: $10K in LangSmith credits, available for 1 year.
• Langfuse for startups: 50% off your entire Langfuse bill for 12 months.
• Braintrust for startups: the Pro plan free for 6–12 months for qualifying startups.

LangChain (LangSmith) ($10K in LangSmith credits available for 1 year)

A sensible order

1. Decide whether you want a dedicated LLM tool or tracing inside a tool you already run. If your product analytics are on PostHog, or your app logs go to Logfire, start there.
2. Otherwise pick one dedicated tracer and instrument your app once. Check retention before volume: Traceloop keeps 24 hours, Laminar 7 days, Arize AX 15 days, Langfuse Hobby 30 days, Opik 60 days.
3. Add evals when you have traffic worth scoring. Arize AX Free lists unlimited evals; Braintrust Starter gives $10 credits / month to start with.
4. Apply to a startup deal only once you know which tool you'll keep, since each one is tied to a single vendor.

Free plans change. Check the source link on each card before you build around a limit, and see the full pack page for the live list. For databases, metrics and logs beyond LLM tracing, see the data and observability pack.

Originally published on Perq, where every listing carries a source link and a last-verified date. Perq is run by Avatar 8 LLC.