[BOT ISSUE] Add instrumentation support for Rig (rig-core) LLM framework

[braintrust-bot]

Summary

The Braintrust Rust SDK has no instrumentation support for Rig (rig-core), the most widely adopted Rust framework for building LLM-powered applications. Rig is not instrumented by any other Braintrust SDK either (Python, JS, Go, Ruby, Java, .NET), making this a completely uninstrumented library across the Braintrust ecosystem.

What is missing

Rig provides execution-oriented API surfaces that could be instrumented to automatically capture spans:

• Agent trait — high-level interface with .prompt() and .chat() async methods for LLM interactions
• CompletionModel trait — common interface for completion requests across providers (OpenAI, Anthropic, Cohere, Gemini, Mistral, and 13+ others)
• EmbeddingModel trait — consistent API for embedding operations
• Tool macro/trait — tool calling during agent execution
• RAG workflows — via VectorStoreIndex trait for retrieval-augmented generation

Wrapping these traits/methods would enable automatic tracing of Rig-based applications, capturing inputs, outputs, token usage, latency, and tool call data for any provider Rig supports.

Library significance

• 472,000+ total downloads on crates.io
• 94 dependent crates (68 direct)
• Latest version: 0.34.0 (actively maintained, 52 releases)
• 18+ provider integrations built-in (OpenAI, Anthropic, Cohere, Gemini, Mistral, DeepSeek, Perplexity, etc.)
• Production users including St Jude, Coral Protocol, and others
• Official documentation at https://docs.rig.rs/

Braintrust docs status

not_found — No mention of Rig in Braintrust documentation. Rig is not listed on the SDK integrations page or any other Braintrust docs page.

Upstream sources

• Rig official site: https://rig.rs/
• Rig documentation: https://docs.rig.rs/
• Rig API reference: https://docs.rs/rig-core/latest/rig/
• Rig GitHub repository: https://github.com/0xPlaygrounds/rig
• Rig on crates.io: https://crates.io/crates/rig-core

Local files inspected

• src/extractors.rs — only OpenAI and Anthropic usage extractors; no Rig-related code
• src/stream.rs — stream aggregator for OpenAI Chat Completions format only
• src/types.rs — core types; no Rig integration types
• src/lib.rs — public API exports; no Rig references
• Cargo.toml — no rig-core dependency
• Full codebase search for "rig", "rig-core", "CompletionModel", "EmbeddingModel" — zero results