How to Resolve Error (Status Code 403) When Using the O3 Model in OpenAI Integration via OpenRouter

This article explains how to resolve the 403 Forbidden error encountered when using the OpenAI O3 model through OpenRouter. This issue typically occurs when the required OpenAI API key tier is not configured correctly under OpenRouter’s Bring Your Own Key (BYOK) integration.

Why This Error Occurs

Requests to the O3 model may fail in the following situations:

The OpenAI API key used is not Tier 3 or higher, which is mandatory for O3.
The API key is not correctly added to the OpenRouter BYOK Integrations page.
Daily usage limits (e.g., 50 requests/day free or 1,000/day with credits) have been exceeded.

Note: OpenAI Tier 3 typically requires approximately $100+ in payments and at least 7 days since your first successful payment, based on OpenAI’s usage tier system.

Prerequisites

Before proceeding, ensure the following:

A valid OpenAI API key with Tier 3 or higher.
An OpenRouter account to manage the BYOK setup.

Resolution Steps

Step 1: Generate an OpenAI API Key

1. Log in to OpenAI

Go to the OpenAI Platform and sign in using your account.

2. Create an API Key

Navigate to API Keys in the OpenAI dashboard.
Select Create API Key.
Assign a recognizable name (e.g., “OpenRouter O3 Key”).
Copy the key and store it safely.

Step 2: Add Your API Key to OpenRouter

Sign Up or Log In to OpenRouter

Visit OpenRouter and access your user dashboard.
Open Integrations Page

Navigate to Settings → Integrations (BYOK)

3. Add Your Key

Select OpenAI as the provider.

Paste your Tier 3+ OpenAI API key into the field.
Click Save to link the key with your OpenRouter account.

OpenRouter will validate the key and authorize the O3 model for your requests.

Step 3: Monitor and Manage Usage

To prevent future 403 errors:

Daily Limits:
1. Free accounts: 50 requests/day
2. Accounts with credits: 1,000 requests/day
Review your token usage and associated costs via the OpenRouter dashboard.
Ensure you do not exceed rate limits enforced by OpenAI for your tier level.

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