Both trace agents, run offline and online evals with LLM judges and code, route traces to human reviewers and version prompts. Maxim AI adds multi-turn text and voice simulation before release and a gateway that can block content, including MCP tool-call arguments; Opik is the one whose evaluation platform you can run yourself at no cost.[1][4]
Maxim AI is a proprietary, hosted platform for simulating, evaluating and tracing agents, including voice agents, sold alongside Bifrost, its Apache-2.0 AI gateway. Opik is Comet's Apache-2.0 tracing and evaluation platform that you can self-host for free. With Maxim the open-source part is the gateway; with Opik it is the evaluation platform itself.
| Decision factor | Maxim AI | Opik |
|---|---|---|
| Ownership | Independent (H3 Labs Inc.); $3M seed led by Elevation Capital in 2024 | Comet ML, independent; reports $70M in total funding |
| What is open source | Bifrost gateway and SDKs (Apache-2.0); platform proprietary | Core platform, UI, backend and SDKs (Apache-2.0) |
| Self-hosting the eval platform | Enterprise in-VPC only, on AWS, GCP or Azure | Free; Kubernetes for production; user administration excluded |
| Pre-release testing | Multi-turn text and voice simulation; scheduled runs and CI | Datasets, experiments, Test Suites with plain-text assertions |
| Run-time checks | Bifrost guardrails on inputs, outputs and MCP tool calls (Bifrost Enterprise) | Guardrails your code calls; a failed check raises an exception |
| Gateway | Bifrost: failover, load balancing, caching, virtual keys, MCP gateway | Opik LLM Gateway in beta, for development and testing only |
| Free tier | Developer: 3 seats, 10k logs a month, 3-day retention | Free Cloud: 10 members, 25k spans a month, 60-day retention |
| First paid tier | Professional: $29 per seat a month, 100k logs, 7-day retention | Pro Cloud: $19 a month, 100k spans, up to 50 members |
| Capability | Maxim AI | Opik | Prefactor |
|---|---|---|---|
| Observe | |||
| LLM call tracing | ✓ | ✓ | ✓ |
| Multi-step agent tracing (tool calls, nested spans) | ✓ | ✓ | ✓ |
| Cost tracking | ✓ | ✓ | ✓ |
| OpenTelemetry support | ✓ | ✓ | ✓ |
| Evaluate | |||
| Offline evals (datasets, experiments) | ✓ | ✓ | ✓ |
| Online evals on production traffic | ✓ | ✓ | ✓ |
| LLM-as-a-judge scoring | ✓ | ✓ | ✓ |
| Code-based evaluators | ✓ | ✓ | ✓ |
| Human review and annotation | ✓ | ✓ | ✓ |
| Prompt versioning and playground | ✓ | ✓ | — |
| Act on findings | |||
| Runtime controls on live agent actions | ✓ | Partial | ✓ |
| Gateway or proxy in the request path | ✓ | Partial | — |
| Licence and deployment | |||
| Open source | Partial | ✓ | Partial |
| Self-hosting | ✓ | ✓ | Partial |
Both vendors publish Apache-2.0 code, but not the same layer. Opik's repository holds the platform itself: tracing, evaluation, the UI, the backend and the SDKs. You can run it on Kubernetes without a contract, and the self-hosted version has every feature except user administration.
Maxim AI's open-source project is Bifrost, an OpenAI-compatible gateway that self-hosts through Docker, Kubernetes or a Go binary, along with its Python, JavaScript and Go SDKs. The simulation, evaluation and observability platform is proprietary. Running that platform in your own cloud is an Enterprise in-VPC deployment, either fully isolated or as a data plane peered to Maxim's control plane.
Both accept OpenTelemetry. Maxim AI ingests OTLP over HTTP with GenAI, OpenInference and AI SDK conventions and can forward traces to New Relic, Snowflake or any OTel collector. Opik accepts OTLP over HTTP only.
Maxim AI's distinctive feature is simulation: multi-turn text and voice conversations run against an agent before it ships, with test runs over datasets for prompts, no-code agents and agents behind an HTTP endpoint, on a schedule or from GitHub Actions. Its evaluators include agent trajectory, tool selection and task success, and annotation queues can include external raters invited by email.
Opik starts from the trace. It offers datasets and experiments, Test Suites with plain-text assertions, more than 30 built-in judge metrics, custom Python metrics, and online rules that score sampled production traffic. Its Prompt Optimizer runs six optimisation algorithms, and annotation queues can fill automatically from score conditions since October 2026.
One limit to weigh on the Maxim side: its public changelog shows no dated 2026 entries and the newest monthly update post covers December 2025, so recent platform changes are hard to verify. In October 2026 its homepage and main pricing page began leading with Bifrost, with the evaluation product moved under /evals.
Maxim AI blocks content only through Bifrost. Its guardrails check inputs, outputs and MCP tool-call arguments and results, and can detect, block, redact or transform content. Maxim's pricing page lists guardrails as a Bifrost Enterprise feature; the evaluation platform itself sends alerts but does not block live actions.
Opik's guardrails (PII, topic, prompt injection, LLM judge and custom classifier) are a blocking validate() call your code makes and must handle. PII and topic checks are English only, and self-hosted guards need a separate server with a GPU recommended. Neither vendor documents approval holds on agent actions.
Bifrost also handles routing: provider failover, load balancing, semantic caching, and virtual keys with budgets and rate limits per key, team and customer. Opik has no production gateway of its own; its LLM Gateway is in beta, and it integrates with LiteLLM, Portkey, OpenRouter, Kong AI Gateway and others.
As of 20 October 2026, Maxim AI charges per seat with log caps. Developer is free for up to three seats and 10k logs a month, kept for three days. Professional is $29 per seat a month with 100k logs and 7-day retention, and Business is $49 per seat a month with 500k logs and 30-day retention. Paid tiers charge $1 per 10k extra logs. Bifrost open source is free; Bifrost Enterprise is custom.
Opik charges a flat plan price by spans, with a member limit rather than a per-seat fee. Free Cloud covers 25k spans a month for up to 10 members, and Pro Cloud is $19 a month for 100k spans and up to 50 members, then $5 per 100k. Default retention on both cloud plans is 60 days. Retention differs more than headline prices, so check Maxim AI's pricing and Opik's pricing against how far back you need to look.
Maxim AI lists online evaluation of production logs from the Professional plan upwards, so its free tier is mainly for pre-release testing.
We sell the layer this section describes. Read it with that in mind.
Stated plainly, since Prefactor publishes this page: Prefactor is an agent evaluation platform that scores each step of a run and acts on what it finds through runtime policies on tool calls and data access, approval holds for risky actions, and a kill switch for a run, an agent or a team. Maxim AI's Bifrost guardrails come closest of these two, checking content in model and MCP traffic on its Enterprise tier; Opik's guardrails run where your code calls them. Neither holds an action for a person to approve. Prefactor has no prompt playground or prompt registry and its platform is hosted, so for prompt iteration, voice simulation or free self-hosting, Maxim AI or Opik is the better pick. See the full comparison of 15 platforms.
Reviewed against public product and documentation pages on October 20, 2026. If a vendor has changed a feature, product name, or positioning since then, send a correction and we will update it. Numbered source links in the page body point to the ordered sources below.
Prefactor scores each step of every agent run and can hold or stop an action when a score says it should not happen. Start on the free tier: 5,000 spans a month, no credit card required.
Prefactor helps teams observe, evaluate, and improve their AI agents in production, across every framework and provider.