Skip to content

Multi-provider

In this guide: run OpenAI, Anthropic, and Gemini through a single Reel proxy at the same time.

The two routing styles

Reel decides which upstream to forward to based on the request URL path. There are two ways to do it:

  1. Path-based auto-routing — Reel inspects the path and infers the provider from its shape (/v1/chat/completions -> OpenAI, /v1/messages -> Anthropic, /v1beta/models/.../generateContent -> Gemini).
  2. Explicit /<provider>/... URL prefix — unambiguous, useful when the same path exists in multiple providers or when you want to be explicit in tests.

Both work against the same cassette. The captured provider field records which upstream each call went to, so replay is never ambiguous.

One proxy, three SDKs

Start the proxy once:

uv run reel auto --cassette tests/cassettes/multi.jsonl

Then point each SDK at the same http://127.0.0.1:7878 and let path-based routing handle the rest:

from openai import OpenAI

client = OpenAI(base_url="http://127.0.0.1:7878/v1")
resp = client.chat.completions.create(
    model="gpt-5",
    messages=[{"role": "user", "content": "Say hi"}],
)

from anthropic import Anthropic

client = Anthropic(base_url="http://127.0.0.1:7878")
resp = client.messages.create(
    model="claude-opus-4",
    max_tokens=128,
    messages=[{"role": "user", "content": "Say hi"}],
)

import google.generativeai as genai

genai.configure(
    api_key="...",
    transport="rest",
    client_options={"api_endpoint": "http://127.0.0.1:7878"},
)
model = genai.GenerativeModel("gemini-2.0-flash")
resp = model.generate_content("Say hi")

All three calls land in the same JSONL cassette. Each entry's provider field tells you who it spoke to.

Explicit provider prefix

When path-based routing can't disambiguate (or when you want to make the routing decision explicit), prefix the path with /<provider>:

http://127.0.0.1:7878/openai/v1/chat/completions
http://127.0.0.1:7878/anthropic/v1/messages
http://127.0.0.1:7878/gemini/v1beta/models/gemini-2.0-flash:generateContent

The prefix is stripped before forwarding upstream. Cassettes still record the canonical provider path.

Different upstreams per provider

The default --upstream only configures the OpenAI fallback. Anthropic and Gemini route to their public APIs unconditionally. If you front any provider with a custom gateway, set the provider-specific environment variables before starting the proxy:

export REEL_OPENAI_UPSTREAM=https://my-openai-gateway.example.com
export REEL_ANTHROPIC_UPSTREAM=https://my-anthropic-gateway.example.com
export REEL_GEMINI_UPSTREAM=https://my-gemini-gateway.example.com

uv run reel auto --cassette tests/cassettes/multi.jsonl

Matching is provider-aware

Each provider's adapter normalizes requests before fingerprinting (OpenAI keys are sorted, Anthropic system is folded into messages, Gemini contents is canonicalized). Two semantically-equal requests across whitespace and key-order differences still match.

See Architecture for the per-provider matching details.

Next