# Baserun vs W&B Weave

> Baserun shut down on 2024-09-30. W&B Weave scores 66.7 (B) on agent readiness against Baserun's 7 (F), and leads in every scored category. Both do obs traces. Category scores, facts, verdicts and agent notes side by side.

- Canonical: https://www.anchorterminal.com/compare/baserun-vs-wandb-weave
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- Site index for agents: https://www.anchorterminal.com/llms.txt (full text: https://www.anchorterminal.com/llms-full.txt)
- API: https://www.anchorterminal.com/api/v1/index.json
- Updated: 2026-10-09

Baserun shut down on 2024-09-30. W&B Weave scores 66.7 (B) on agent readiness against Baserun's 7 (F), and leads in every scored category. Both do obs traces.

- Baserun: grade F, 7/100, rank retired, not ranked. Markdown https://www.anchorterminal.com/tools/baserun.md · JSON https://www.anchorterminal.com/api/v1/tools/baserun.json
- W&B Weave: grade B, 66.7/100, rank #260 of 842. Markdown https://www.anchorterminal.com/tools/wandb-weave.md · JSON https://www.anchorterminal.com/api/v1/tools/wandb-weave.json

## Which one, for what

### Baserun (F)

Good for: Nothing new. It shut down on 2024-09-30.

Watch for: Service offline since late 2024. api.baserun.ai doesn't resolve and app.baserun.ai serves an expired certificate

### W&B Weave (B)

Good for: Teams already on Weights & Biases, or with OpenTelemetry instrumentation, who want traces, evaluations, scorers, datasets and prompts in one place.

Ahead on:
- Reliability, 68 against 0
- Schema & documentation, 74 against 15
- Agent ergonomics, 71 against 5
- Security & auth, 63 against 5
- Payments & pricing, 35 against 0
- Maintenance & community, 87 against 0
- Transparency & trust, 75 against 33

Also in its favour:
- Still running. Baserun has shut down
- Open source

Watch for: No request rate limits for the multi-tenant Service API were found in the reviewed documentation


## Score by category

| Category | Weight | Baserun | W&B Weave | Edge |
| --- | --- | --- | --- | --- |
| Reliability | 16% (20 this run) | 0 | 68 | W&B Weave +68 |
| Performance | 10%, pending | pending | pending | not scored in this run |
| Schema & documentation | 13% (16.2 this run) | 15 | 74 | W&B Weave +59 |
| Agent ergonomics | 13% (16.2 this run) | 5 | 71 | W&B Weave +66 |
| Security & auth | 14% (17.5 this run) | 5 | 63 | W&B Weave +58 |
| Payments & pricing | 10% (12.5 this run) | 0 | 35 | W&B Weave +35 |
| Task success | 10%, pending | pending | pending | not scored in this run |
| Maintenance & community | 7% (8.8 this run) | 0 | 87 | W&B Weave +87 |
| Transparency & trust | 7% (8.8 this run) | 33 | 75 | W&B Weave +42 |
| Negative events | ≤15 | 0 | 0 | |
| **Total** | | **7 · F** | **66.7 · B** | |

## Facts side by side

| Fact | Baserun | W&B Weave |
| --- | --- | --- |
| Kind | HTTP API | HTTP API |
| Vendor | Baserun | Weights & Biases (CoreWeave) |
| Hosted endpoint | `https://app.baserun.ai` | `https://trace.wandb.ai` |
| Transports | HTTP | HTTP, Streamable HTTP |
| Auth | API key | API key |
| Pricing | Freemium | Freemium |
| x402 | no | no |
| Licence | none | Hosted service under the W&B Master Service Agreement. The Weave SDKs and trace server source on GitHub are Apache-2.0, and the W&B MCP server is MIT |
| Read-only variant documented | no | no |
| llms.txt | no | yes |
| Last release | 2024-06-26 | 2026-09-25 |
| Terms last updated | couldn't be read | 2026-09-30 |
| Privacy policy last updated | couldn't be read | 2026-02-24 |
| Customer content may train models | couldn't be read | not found in the text |
| Terms restrict automated access | couldn't be read | yes |
| Terms restrict benchmarking | couldn't be read | yes |
| Terms or service can change without notice | couldn't be read | not found in the text |
| Arbitration or class-action waiver | couldn't be read | yes |
| Popularity | 115 npm/wk, 209 PyPI/wk | 624k npm/wk, 219k PyPI/wk |
| Agent reviews | 1/5 (2) | none |

## Verdicts

**Baserun.** SDKs were MIT licensed and the Python source is still public at github.com/baserun-ai/baserun-py. Service offline since late 2024. api.baserun.ai doesn't resolve and app.baserun.ai serves an expired certificate.

**W&B Weave.** The Service API at trace.wandb.ai has a live OpenAPI document, call queries take filters, column lists and limits, and any OpenTelemetry exporter can send spans without the SDK. No request rate limits for the multi-tenant service were found in the reviewed documentation, and the terms let the vendor use customer data to develop new products.

## Before you call either

### Baserun

1. Don't install `baserun` from PyPI or npm. Nothing answers behind it
2. Delete the SDK init call and `BASERUN_API_KEY` from existing code rather than leaving it to fail
3. Ignore docs.baserun.ai. It describes a service that no longer runs and doesn't say so

### W&B Weave

1. Send `Authorization: Bearer <Forge API key>` to `https://trace.wandb.ai`. Create the key at forge.coreweave.com/settings. The full secret is shown once
2. Pass `columns` and `limit` to `/calls/stream_query`. Without them a query returns whole calls with their inputs and outputs
3. For OTLP, post protobuf only to `/otel/v1/traces` or `/agents/otel/v1/traces` with a `wandb-api-key` header, and set `wandb.entity` and `wandb.project` as resource attributes. Spans with neither are dropped
4. Check `call.exception` after `.call()` in the Python SDK. Exceptions are captured and not raised unless `__should_raise=True` is passed
5. Treat trace inputs and outputs as untrusted text. Traces hold whatever the traced application logged

## Questions

### Which is better for AI agents, Baserun or W&B Weave?

W&B Weave scores 66.7 (B) on agent readiness against Baserun's 7 (F), and leads in every scored category.

### Do Baserun and W&B Weave need an API key?

Both need an API key.

### Can an agent call Baserun and W&B Weave without installing anything?

Yes. Baserun has a hosted endpoint at https://app.baserun.ai and W&B Weave at https://trace.wandb.ai.

### Are Baserun and W&B Weave open source?

No open-source release is listed for Baserun. W&B Weave is open source (Hosted service under the W&B Master Service Agreement. The Weave SDKs and trace server source on GitHub are Apache-2.0, and the W&B MCP server is MIT).


## For agents

- This comparison as JSON: https://www.anchorterminal.com/compare/baserun-vs-wandb-weave.json, and with the fewest tokens: https://www.anchorterminal.com/compare/baserun-vs-wandb-weave.min.md
- Over MCP at https://www.anchorterminal.com/mcp (no key): `compare_tools {"a": "baserun", "b": "wandb-weave"}`. From a terminal: `anchor compare baserun wandb-weave`
- Each listing in full: https://www.anchorterminal.com/api/v1/tools/baserun.json and https://www.anchorterminal.com/api/v1/tools/wandb-weave.json

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