Both cover tracing, offline and online evals, human review and prompt versioning. Maxim AI leads on simulation, including voice, and on evals that non-engineers can run from the UI; W&B Weave, now part of CoreWeave Forge, is a Python toolkit that lives next to your model training.[1][6]
Maxim AI is a hosted platform for simulating, evaluating and tracing agents, including voice agents, sold alongside its open-source Bifrost gateway; W&B Weave is a code-first tracing and evaluation toolkit from Weights & Biases. CoreWeave acquired W&B in May 2025, and since 30 September 2026 Weave is sold inside CoreWeave Forge. Maxim suits product and engineering teams testing before release; Weave suits teams already on Weights & Biases.
| Decision factor | Maxim AI | W&B Weave |
|---|---|---|
| Ownership | H3 Labs Inc., independent; $3M seed led by Elevation Capital in 2024 | CoreWeave, which completed its acquisition of W&B in May 2025; sold in CoreWeave Forge since 30 September 2026 |
| Simulation | Multi-turn text and voice simulation | Not documented |
| Who runs evals | UI or SDK, for prompts, no-code agents and HTTP endpoints | Code: Evaluation API with scorers |
| Run-time checks | Through Bifrost: guardrails on model and MCP tool calls (Enterprise feature) | Partial: Python guardrail scorers on inputs and outputs |
| Gateway | Bifrost, Apache-2.0, self-hostable | None found |
| Self-hosting | Enterprise in-VPC on AWS, GCP or Azure | Kubernetes, with a W&B Platform install and a Weave-enabled licence |
| Free tier | Developer: up to 3 seats, 10k logs a month, 3-day retention | Forge Free: up to 5 model seats, 1 GB Weave ingestion a month |
| First paid tier | Professional: $29 per seat a month, 100k logs | Forge Pro: from $60 a month, 1.5 GB ingestion, teams under 50 people |
| Capability | Maxim AI | W&B Weave | 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 | ✓ | Not stated | — |
| Licence and deployment | |||
| Open source | Partial | Partial | Partial |
| Self-hosting | ✓ | ✓ | Partial |
Both products now sit inside something larger. CoreWeave completed its acquisition of Weights & Biases on 5 May 2025 and on 30 September 2026 launched CoreWeave Forge, which bundles W&B Models, Weave and other CoreWeave tools; hosted W&B accounts now sign in through Forge. CoreWeave recommends Agent Lens, a separate product in public preview sharing Weave's trace backend, for agent tracing.
Maxim AI is independent, but its emphasis has moved. In October 2026 its homepage and pricing page began leading with Bifrost, its open-source AI gateway, and the evaluation platform moved under getmaxim.ai/evals. Its public changelog shows no dated 2026 entries and the newest monthly update post covers December 2025, so recent changes to the evaluation product are hard to verify. For either vendor, confirm the roadmap for the product you are buying before a long commitment.
Maxim is designed for product and engineering to test agents together. Test runs cover prompts, no-code agents and any agent behind an HTTP endpoint, from the UI or SDK, on a schedule or in GitHub Actions. Simulations play out multi-turn conversations in text or voice, with integrations for LiveKit, ElevenLabs and the OpenAI Realtime API. Evaluators include pre-built LLM judges, custom judges with your chosen model and scale, JavaScript or Python code, and API-based checks, with agent-specific ones for trajectory and tool selection. Human raters, including external raters added by email, work through annotation queues.
Weave is designed for engineers in code. You trace functions with @weave.op, run the Evaluation API over datasets with LLM-judge, function or class-based scorers, compare runs and share leaderboards. Annotation queues route selected traces to reviewers, and versioned prompts and a Playground let you compare models side by side. The TypeScript SDK lacks class-based scorers, guardrails and cost tracking.
If you are building a voice agent, or want non-engineers running test suites, Maxim covers more. If your team already lives in Weights & Biases and writes Python, Weave adds less friction.
Maxim's run-time checks come through Bifrost. Its guardrails check model inputs and outputs and MCP tool-call arguments and results, and can block, redact or transform content. Maxim's pricing page lists guardrails as a Bifrost Enterprise feature, and the evaluation platform itself alerts rather than blocks.
Weave's guardrails are scorers called from Python application code that can block or modify inputs and outputs before they reach users. That needs code changes, and the TypeScript SDK does not support it. Neither vendor documents approval holds on agent actions.
Hosting options differ in shape. Maxim's in-VPC deployment on AWS, GCP or Azure can be fully isolated or a data plane peered to Maxim's cloud control plane, and is listed only on Enterprise; Bifrost's open-source edition runs on Docker, Kubernetes or as a Go binary. Weave offers multi-tenant SaaS, a single-tenant Dedicated Cloud, and a self-hosted option on Kubernetes that needs a W&B licence and platform install.
As of 20 October 2026, Maxim's Developer plan is free for up to three seats and 10k logs a month with three days of retention. Professional is $29 per seat a month with 100k logs and seven days of retention, Business is $49 per seat a month with 500k logs and 30 days, and paid overage is $1 per 10k logs. Online evaluation of production logs starts on Professional.
Weave is billed through CoreWeave Forge plans. Forge Free includes up to five model seats and 1 GB of Weave ingestion a month; Forge Pro starts at $60 a month with ten seats and 1.5 GB, for teams under 50 people, with overage listed at $0.10 per MB. Maxim's short retention on lower tiers and Weave's small ingestion allowances are the limits to model first. See Maxim AI's pricing and CoreWeave Forge pricing.
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's Bifrost guardrails cover model and MCP tool-call content on its Enterprise edition, and Weave's guardrails run in Python code; neither holds an action for a person to approve. Prefactor has no prompt playground or prompt registry, no voice simulation, and its platform is hosted. 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.