Overview

Prerequisites

What You'll Learn

What You'll Need

What You'll Build

Environment Setup

Clone and Run Setup

git clone https://github.com/Snowflake-Labs/sfquickstarts.git
cd sfquickstarts/site/sfguides/src/build-multi-tenant-ai-chat-application-with-cortex-rest-api/assets

bash setup.sh

Project Structure

Configure Environment Variables

SNOWFLAKE_ACCOUNT=YOUR_ACCOUNT_IDENTIFIER

ALPHA_SNOWFLAKE_USER=COCO_USER_ALPHA
ALPHA_PRIVATE_KEY_PATH=keys/alpha_rsa_key.p8

BETA_SNOWFLAKE_USER=COCO_USER_BETA
BETA_PRIVATE_KEY_PATH=keys/beta_rsa_key.p8

COCO_PORT=8000
LOG_LEVEL=INFO

Replace YOUR_ACCOUNT_IDENTIFIER with your Snowflake account identifier (e.g., MYORG-MYACCOUNT).

Accounts with underscores: If your account identifier contains underscores (e.g., MYORG-MY_ACCOUNT), the auto-generated Cortex URL will fail due to SSL hostname validation. Add this line using your account locator instead:

CORTEX_BASE_URL_OVERRIDE=https://YOUR_ACCOUNT_LOCATOR.snowflakecomputing.com/api/v2/cortex

Find your account locator by running SELECT CURRENT_ACCOUNT(); in Snowsight.

Snowflake RBAC Setup

Step 1: Create Roles and Users

USE ROLE ACCOUNTADMIN;

-- Create tenant roles
CREATE ROLE IF NOT EXISTS COCO_TENANT_ALPHA;
CREATE ROLE IF NOT EXISTS COCO_TENANT_BETA;

-- Grant Cortex access to both roles
GRANT DATABASE ROLE SNOWFLAKE.CORTEX_USER TO ROLE COCO_TENANT_ALPHA;
GRANT DATABASE ROLE SNOWFLAKE.CORTEX_USER TO ROLE COCO_TENANT_BETA;

-- Create service users (TYPE=SERVICE means no interactive login)
CREATE USER IF NOT EXISTS COCO_USER_ALPHA
    TYPE = SERVICE
    DEFAULT_ROLE = COCO_TENANT_ALPHA;
CREATE USER IF NOT EXISTS COCO_USER_BETA
    TYPE = SERVICE
    DEFAULT_ROLE = COCO_TENANT_BETA;

-- Assign roles
GRANT ROLE COCO_TENANT_ALPHA TO USER COCO_USER_ALPHA;
GRANT ROLE COCO_TENANT_BETA TO USER COCO_USER_BETA;

-- Register RSA public keys (replace with your actual keys)
ALTER USER COCO_USER_ALPHA SET RSA_PUBLIC_KEY='MIIBIjANBgkqhki...your-alpha-key...';
ALTER USER COCO_USER_BETA  SET RSA_PUBLIC_KEY='MIIBIjANBgkqhki...your-beta-key...';

Tip: Extract the key content without the BEGIN/END lines:

awk 'NR>1 && !/END/' keys/alpha_rsa_key.pub | tr -d '\n'

Step 2: Enable Model RBAC

USE ROLE ACCOUNTADMIN;

CALL SNOWFLAKE.MODELS.CORTEX_BASE_MODELS_REFRESH();
ALTER ACCOUNT SET CORTEX_MODELS_ALLOWLIST = 'None';

-- Alpha models
GRANT APPLICATION ROLE SNOWFLAKE."CORTEX-MODEL-ROLE-CLAUDE-4-SONNET" TO ROLE COCO_TENANT_ALPHA;
GRANT APPLICATION ROLE SNOWFLAKE."CORTEX-MODEL-ROLE-MISTRAL-LARGE2" TO ROLE COCO_TENANT_ALPHA;

-- Beta models
GRANT APPLICATION ROLE SNOWFLAKE."CORTEX-MODEL-ROLE-OPENAI-GPT-4.1" TO ROLE COCO_TENANT_BETA;
GRANT APPLICATION ROLE SNOWFLAKE."CORTEX-MODEL-ROLE-LLAMA3.1-70B" TO ROLE COCO_TENANT_BETA;
GRANT APPLICATION ROLE SNOWFLAKE."CORTEX-MODEL-ROLE-DEEPSEEK-R1" TO ROLE COCO_TENANT_BETA;

How the Gateway Works

JWT Token Factory (app/core/jwt_helper.py)

payload = {
    "iss": f"{self.qualified_username}.{self._public_key_fp}",
    "sub": self.qualified_username,
    "iat": iat,
    "exp": exp,
}
token = jwt.encode(payload, self._private_key, algorithm="RS256")

Tenant Registry (app/core/tenants.py)

Cortex REST API Client (app/services/cortex_client.py)

url = f"{self.base_url}/v1/chat/completions"
body = {
    "model": model,
    "messages": messages,
    "max_completion_tokens": request.max_tokens,
    "temperature": request.temperature,
    "stream": True,
}

Auth Guard (app/api/v1/dependencies.py)

How the Streamlit Chat Works

Flow

with httpx.stream("POST", f"{GATEWAY_URL}/v1/chat/stream",
                   json=payload, headers=headers, timeout=60.0) as response:
    for line in response.iter_lines():
        if line.startswith("data:"):
            data = json.loads(line[len("data:"):].strip())
            if current_event == "delta":
                full_response += data.get("content", "")
                placeholder.markdown(full_response + "▌")

Model access is Snowflake-native: The models list in the UI is a hint. Real enforcement happens via Model RBAC — if a model is listed but not granted to the tenant's role, Snowflake returns 403.

Run and Test

Start the Gateway

source venv/bin/activate
python3 -m uvicorn app.main:app --host 0.0.0.0 --port 8000 --reload

curl http://localhost:8000/healthz
# {"status":"ok"}

Start the Streamlit App

source venv/bin/activate
cd streamlit_app
streamlit run streamlit_app.py --server.port 8501

Test Streaming Chat via curl

curl -N -X POST http://localhost:8000/v1/chat/stream \
  -H "Content-Type: application/json" \
  -H "X-API-Key: sk-alpha-secret-key-001" \
  -d '{"message": "What is Snowflake Cortex?", "model": "claude-4-sonnet"}'

event: meta
data: {"id": "coco_req_abc123", "model": "claude-4-sonnet", "tenant_id": "tenant-alpha"}

event: delta
data: {"content": "Snowflake"}

event: delta
data: {"content": " Cortex"}
...

event: done
data: {"id": "coco_req_abc123", "latency_ms": 2340, "usage": {"prompt_tokens": 12, "completion_tokens": 89}}

Test RBAC Denial

curl -N -X POST http://localhost:8000/v1/chat/stream \
  -H "Content-Type: application/json" \
  -H "X-API-Key: sk-beta-secret-key-001" \
  -d '{"message": "Hello", "model": "claude-4-sonnet"}'

Bonus: Extending to Cortex Agents

Tip: To restrict an agent to only certain tenants, simply omit the GRANT for that role. Snowflake will return a permission error — no application code changes needed.

Conclusion And Resources

What You Learned

Related Resources