---
title: "Passthrough"
description: "Forward provider-native requests through Bifrost with full core pipeline processing, including logs and observability."
icon: "route"
---
## Overview
Passthrough integrations let you call provider-native API paths and payloads through Bifrost without route-level request/response conversion.
When you use passthrough endpoints, the request still flows through Bifrost core logic. You keep Bifrost features such as logging and observability while sending provider-native paths and bodies.
---
## Endpoints
- `/openai_passthrough`
Default provider: `openai`
- `/anthropic_passthrough`
Default provider: `anthropic`
- `/azure_passthrough`
Default provider: `azure`
- `/genai_passthrough`
Default provider: `gemini` (with automatic Vertex detection for clients configured to use Vertex)
---
## How It Works
1. Send your request to a passthrough endpoint (OpenAI, Anthropic, Azure, or GenAI passthrough).
2. The integration strips the passthrough prefix and forwards the remaining provider-native path/body.
3. Bifrost handles provider execution through core inference and plugin pipelines.
4. Response status, headers, and body are returned as passthrough output (for both stream and non-stream requests).
---
## Provider Selection Rules
### OpenAI Passthrough
- Uses `openai` as the default provider.
### Anthropic Passthrough
- Uses `anthropic` as the default provider.
### Azure Passthrough
- Uses `azure` as the default provider.
- Requires an Azure key with `endpoint` configured. `api-version` is injected automatically:
- **Key config `api_version`** takes priority (consistent with how auth is handled).
- Falls back to any `api-version` the client supplied in the query string.
### GenAI Passthrough
- Uses `gemini` by default.
- Automatically switches to `vertex` when Vertex patterns are detected, such as:
- URL path containing `/projects/{PROJECT_ID}/locations/{LOCATION}/`
- Request body `model` containing a Vertex resource path
- OAuth token pattern typically used for Vertex (`Bearer ya29...`)
---
## Usage Examples
### OpenAI Passthrough
```python
import openai
client = openai.OpenAI(
base_url="http://localhost:8080/openai_passthrough/v1",
api_key="dummy-key"
)
response = client.chat.completions.create(
model="gpt-4o-mini",
messages=[{"role": "user", "content": "hello from passthrough"}]
)
print(response.choices[0].message.content)
```
```bash
curl -X POST "http://localhost:8080/openai_passthrough/v1/chat/completions" \
-H "content-type: application/json" \
-H "authorization: Bearer sk-your-openai-key" \
-d '{
"model": "gpt-4o-mini",
"messages": [{"role":"user","content":"hello from passthrough"}]
}'
```
### Anthropic Passthrough
```python
import anthropic
client = anthropic.Anthropic(
base_url="http://localhost:8080/anthropic_passthrough",
api_key="dummy-key"
)
response = client.messages.create(
model="claude-sonnet-4-20250514",
max_tokens=1024,
messages=[{"role": "user", "content": "hello from passthrough"}]
)
print(response.content[0].text)
```
```bash
curl -X POST "http://localhost:8080/anthropic_passthrough/v1/messages" \
-H "content-type: application/json" \
-H "x-api-key: your-anthropic-key" \
-H "anthropic-version: 2023-06-01" \
-d '{
"model": "claude-sonnet-4-20250514",
"max_tokens": 1024,
"messages": [{"role":"user","content":"hello from passthrough"}]
}'
```
### Azure Passthrough
```python
from openai import AzureOpenAI
client = AzureOpenAI(
azure_endpoint="http://localhost:8080/azure_passthrough",
api_key="dummy-key",
api_version="2024-10-21", # overridden by key config api_version if set
)
response = client.chat.completions.create(
model="gpt-4o", # your Azure deployment name
messages=[{"role": "user", "content": "hello from azure passthrough"}]
)
print(response.choices[0].message.content)
```
```python
from openai import OpenAI
client = OpenAI(
base_url="http://localhost:8080/azure_passthrough/openai/v1/",
api_key="dummy-key",
)
response = client.responses.create(
model="gpt-4.1", # your Azure deployment name
input="hello from azure passthrough",
)
print(response.output_text)
```
```python
import anthropic
client = anthropic.Anthropic(
base_url="http://localhost:8080/azure_passthrough",
api_key="dummy-key",
)
response = client.messages.create(
model="claude-sonnet-4-20250514",
max_tokens=1024,
messages=[{"role": "user", "content": "hello from azure passthrough"}]
)
print(response.content[0].text)
```
```bash
curl -X POST "http://localhost:8080/azure_passthrough/openai/deployments/gpt-4o/chat/completions" \
-H "content-type: application/json" \
-d '{
"messages": [{"role": "user", "content": "hello from azure passthrough"}]
}'
```
### GenAI Passthrough (Gemini)
```python
from google import genai
from google.genai.types import HttpOptions
client = genai.Client(
api_key="dummy-key",
http_options=HttpOptions(base_url="http://localhost:8080/genai_passthrough")
)
response = client.models.generate_content(
model="gemini-2.5-flash",
contents="hello from passthrough"
)
print(response.text)
```
```bash
curl -X POST "http://localhost:8080/genai_passthrough/v1beta/models/gemini-2.5-flash:generateContent" \
-H "content-type: application/json" \
-H "x-goog-api-key: your-gemini-key" \
-d '{
"contents":[{"parts":[{"text":"hello from passthrough"}]}]
}'
```
### GenAI Passthrough (Vertex-style request)
```python
from google import genai
from google.genai.types import HttpOptions
client = genai.Client(
vertexai=True,
api_key="dummy-key",
http_options=HttpOptions(base_url="http://localhost:8080/genai_passthrough")
)
response = client.models.generate_content(
model="gemini-2.5-flash",
contents="hello from vertex passthrough"
)
print(response.text)
```
```bash
curl -X POST "http://localhost:8080/genai_passthrough/v1/projects/my-project/locations/us-central1/publishers/google/models/gemini-2.5-flash:generateContent" \
-H "content-type: application/json" \
-H "authorization: Bearer ya29.your-vertex-token" \
-d '{
"contents":[{"parts":[{"text":"hello from vertex passthrough"}]}]
}'
```
---
## Notes
- Use passthrough when you need a provider endpoint that is not directly supported by Bifrost integration routes yet.
- For Azure passthrough, auth headers (`api-key`, `x-api-key`, OAuth token) are always sourced from the Bifrost key config and never forwarded from the client request.