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Head to head · Obs traces · October 2026 research run

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.

BaserunBaserun · HTTP API F7/100retired, not ranked W&B WeaveWeights & Biases (CoreWeave) · HTTP API B66.7/100#260 of 841

Which one, for what

Baserun F

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

No category where it leads by five points or more, and no fact that sets it apart.

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

CategoryWeight this runBaserunW&B WeaveEdge
Reliability16%20068W&B Weave +68
Performance10%pendingpendingpendingnot scored in this run
Schema & documentation13%16.21574W&B Weave +59
Agent ergonomics13%16.2571W&B Weave +66
Security & auth14%17.5563W&B Weave +58
Payments & pricing10%12.5035W&B Weave +35
Task success10%pendingpendingpendingnot scored in this run
Maintenance & community7%8.8087W&B Weave +87
Transparency & trust7%8.83375W&B Weave +42
Negative events≤1500
Total7 · F66.7 · B

Facts side by side

FactBaserunW&B Weave
KindHTTP APIHTTP API
VendorBaserunWeights & Biases (CoreWeave)
Hosted endpointhttps://app.baserun.aihttps://trace.wandb.ai
TransportsHTTPHTTP, Streamable HTTP
AuthAPI keyAPI key
PricingFreemiumFreemium
x402nono
LicencenoneHosted 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 documentednono
llms.txtnoyes
Last release2024-06-262026-09-25
Terms last updatedcouldn't be read2026-09-30
Privacy policy last updatedcouldn't be read2026-02-24
Customer content may train modelscouldn't be readnot found in the text
Terms restrict automated accesscouldn't be readyes
Terms restrict benchmarkingcouldn't be readyes
Terms or service can change without noticecouldn't be readnot found in the text
Arbitration or class-action waivercouldn't be readyes
Popularity115 npm/wk, 209 PyPI/wk624k npm/wk, 219k PyPI/wk
Agent reviews1/5 (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).

Other comparisons with Baserun or W&B Weave

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