feat: add Baseten provider support

[Joshalphonse]

Summary

• add Baseten as an OpenAI-compatible language and embedding provider, including env/runtime credential support and base URL normalization
• reapply the provider work on top of the latest main changes and update docs/examples so Baseten support is reflected across the current codebase
• add Baseten coverage in unit tests and fix small upstream SDK typing mismatches so the rebased branch typechecks cleanly

Testing

• npm run typecheck
• npm exec vitest run tests/unit/providers-baseten.test.ts tests/unit/language-codes.test.ts tests/unit/transcripts.test.ts tests/unit/shots.test.ts

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Note

Medium Risk
Adds a new AI provider and updates core model/credential resolution paths, which can affect workflow execution and configuration. Most changes are additive with tests and documentation updates, but misconfiguration of Baseten base URLs/models could surface at runtime.

Overview
Adds Baseten as a first-class provider option for language and embedding workflows, implemented as an OpenAI-compatible backend with required BASETEN_* env/runtime credentials and base-URL normalization.

Updates provider/model resolution utilities to support Baseten defaults (BASETEN_MODEL / BASETEN_EMBEDDING_MODEL with fallbacks), adds Baseten API key handling in workflow credentials/types, and explicitly excludes Baseten from Evalite insights generation for now.

Refreshes docs, env examples, and CLI examples to advertise/select baseten, and adds unit coverage for Baseten model/default/baseURL behavior; also tweaks a few Mux SDK calls and transcript language confidence parsing to keep typechecking clean.

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[claude]

Claude Code Review

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[cursor]

Cursor Bugbot has reviewed your changes and found 1 potential issue.

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[cursor]

Credential-over-env precedence broken for embedding base URL

Medium Severity

The embedding candidate array interleaves credential and env sources: [basetenEmbeddingBaseUrl, env.BASETEN_EMBEDDING_BASE_URL, basetenBaseUrl, env.BASETEN_BASE_URL]. Because candidates.find(Boolean) picks the first truthy value, env.BASETEN_EMBEDDING_BASE_URL can override a credential-provided basetenBaseUrl. This breaks the credential-over-env precedence pattern used everywhere else in the codebase (e.g., API key resolution always prefers credential values over env vars). The credential's generic basetenBaseUrl — intended as a fallback for all Baseten endpoints per the WorkflowCredentials type doc — loses to a stale or unrelated env var.

 

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[monsieurBoutte]

thanks for starting this work! closing in favor of #205