VS Code Copilot Chat BYOK — Definitive Guide

Complete Bring Your Own Key (BYOK) configuration for VS Code Copilot Chat with Groq, Cerebras, OpenRouter, and Google Gemini, including a workaround for the No lowest priority node found bug in the prompt-tsx renderer.

What is this?

This repository contains all the configuration, scripts, and documentation needed to set up GitHub Copilot Chat in VS Code using your own API keys from 5 providers:

Groq (Llama 3.3 70B, Llama 4 Scout, Qwen3, GPT-OSS 120B/20B)
Cerebras (GPT-OSS 120B, Zai GLM 4.7, Gemma 4 31B — ultra-fast inference)
OpenRouter (2 keys — 23 free models including Nemotron 550B, Qwen3 Coder, Hermes 405B)
Google Gemini (Gemini 2.5 Flash/Pro, Gemini 3.5 Flash, etc.)

After 9 iterations (v1 to v9), a working configuration was achieved that:

Enables Agent mode (file creation, code editing, tool calling) with Llama 4 Scout from Groq
Enables Ask mode with all other models
Solves the No lowest priority node found bug in the prompt-tsx renderer
Solves the Missing Authentication header bug with custom endpoints
Preserves native OpenRouter and Gemini providers

Features

Automated setup with a single PowerShell script
API keys stored in Windows Credential Manager (not in plaintext)
Models grouped by use case (Agent, Ask, Cerebras Ultra Fast)
Pinned models automatically in the picker
Corrupt state cleanup integrated
Live tool calling debug against each provider
Complete documentation of every bug found and its root cause
Automatic backup before every change

Project Stats

Metric	Value
Script iterations	9 (v1 → v9)
Bugs solved	7
Supported providers	5
Configured models	31 (in full configuration)
GitHub issues analyzed	12+
Documentation lines	1,500+
PowerShell script lines	~410
Python script lines	~50

Quick Start

# 1. Clone the repo
git clone https://github.com/your-username/vscode-byok-copilot.git
cd vscode-byok-copilot

# 2. Edit the API keys in the script
notepad scripts/byok-master.ps1
# Replace the $keys values with your real API keys

# 3. Run the script
powershell -ExecutionPolicy Bypass -File .\scripts\byok-master.ps1

# 4. Follow the on-screen instructions

Important: Before running the script, you must add the 5 providers via VS Code UI (Chat: Manage Language Models → Add Models) so the API keys are stored in Windows Credential Manager. The -SetupMode script flag shows detailed instructions.

Repository Structure

vscode-byok-copilot/
├── README.md                          # This file
├── LICENSE                            # MIT License
├── .gitignore
├── CHANGELOG.md                       # Version history
├── docs/
│   ├── complete-report.md             # Full technical report (1,500+ lines)
│   ├── bugs-found.md                  # Analysis of each bug and its solution
│   ├── architecture.md                # Request flow diagram
│   └── images/                        # Screenshots
├── scripts/
│   ├── byok-master.ps1                # Master script (full setup)
│   ├── debug-tools.ps1                # Live tool calling debug
│   ├── clean-chats.ps1                # Quick cleanup of corrupt chats
│   ├── test-keys.ps1                  # API key verification
│   ├── show-models.ps1                # Discover available models
│   └── modify_state.py                # Modify state.vscdb (Python)
├── config/
│   ├── chatLanguageModels.json        # Final config (template)
│   ├── settings.json                  # VS Code settings (template)
│   └── examples/                      # Example configurations
└── references/
    └── links.md                       # Links to official docs and issues

Prerequisites

Software

Component	Min Version	How to verify
VS Code	1.122+ (1.127+ recommended)	`Help → About`
GitHub Copilot	latest	Extensions panel
GitHub Copilot Chat	latest	Extensions panel
PowerShell	5.1+	`$PSVersionTable`
Python	3.8+ (with `py` launcher)	`py --version`
Git	any version	`git --version`

Accounts and API Keys

Create an account and generate an API key on each platform:

Provider	URL to get key	Free tier
Groq	https://console.groq.com/keys	No credit card required
Cerebras	https://cloud.cerebras.ai/	Free trial, 1M tokens/day
OpenRouter	https://openrouter.ai/keys	Up to 5 keys per account
Google Gemini	https://aistudio.google.com/apikey	20 req/day per model

Installation

Step 1: Clone the repository

git clone https://github.com/your-username/vscode-byok-copilot.git
cd vscode-byok-copilot

Step 2: Configure your API keys

Edit scripts/byok-master.ps1 and replace the $keys values:

$keys = @{
    Groq        = "gsk_YOUR_KEY_HERE"
    Cerebras    = "csk_YOUR_KEY_HERE"
    OpenRouter1 = "sk-or-v1_YOUR_KEY_1_HERE"
    OpenRouter2 = "sk-or-v1_YOUR_KEY_2_HERE"
    Gemini      = "AIza_YOUR_KEY_HERE"
}

Step 3: Add providers via UI (CRITICAL)

This is essential for API keys to be stored in Windows Credential Manager.

Open VS Code
Ctrl+Shift+P → Chat: Manage Language Models
Click + Add Models
Add the 5 providers following the script instructions:

powershell -ExecutionPolicy Bypass -File .\scripts\byok-master.ps1 -SetupMode

Close VS Code completely

Step 4: Run the master script

powershell -ExecutionPolicy Bypass -File .\scripts\byok-master.ps1

The script:

Closes VS Code
Backs up current configuration
Cleans corrupt chats and caches
Writes chatLanguageModels.json with configured models
Writes settings.json with critical settings
Modifies state.vscdb to pin models
Verifies API keys work
Opens VS Code

Step 5: Enable models in the picker

Ctrl+Shift+P → Developer: Reload Window
Ctrl+Shift+P → Chat: Manage Language Models
Click the > arrow next to each group to expand
Hover over each model → click the eye icon to show it
To pin: hover → click the pin icon

Step 6: Test

Open a new chat (Ctrl+Alt+I)
Select Llama 4 Scout - Main Agent
Agent mode
Prompt: "Create a file factorial.py with a recursive factorial function"

Usage

Agent Mode (with tool calling)

For creating files, editing code, full projects.

Model	Provider	Recommended for
Llama 4 Scout	Groq	Main agent, quick files
Nemotron 3 Ultra 550B	OpenRouter (free)	Full projects, 1M context
Qwen3 Coder	OpenRouter (free)	Code, 1M context
Gemini 2.5 Pro	Google	Heavy reasoning
Gemini 3.5 Flash	Google	Quick tasks with tools

Ask Mode (without tool calling)

For questions, generating snippets, explaining code.

Model	Provider	Recommended for
Llama 3.3 70B	Groq	Generating standalone functions
GPT-OSS 120B	Groq	Reasoning without tools
GPT-OSS 120B	Cerebras	Ultra fast (3000 tok/s)
Zai GLM 4.7	Cerebras	Max speed (1000 tok/s)

How to switch modes

In the VS Code chat, above the input, there's a dropdown that says Agent or Ask. Click to switch.

Troubleshooting

`No lowest priority node found`

Cause: The prompt-tsx renderer corrupts when processing tool calls from custom endpoints when maxInputTokens is less than the tools payload (~25k tokens).

Solutions:

New chat: Don't reuse chats that errored
Use Llama 4 Scout (TPM=30,000) for Agent mode
Switch to Ask mode for other models

Run quick cleanup:

powershell -ExecutionPolicy Bypass -File .\scripts\clean-chats.ps1

`Invalid API Key` / `Missing Authentication header`

Cause: Plaintext API key doesn't work with toolCalling: true.

Solution: Add the provider via UI so VS Code stores the key in Credential Manager with reference ${input:chat.lm.secret.xxx}.

`413 Request too large`

Cause: VS Code's payload (25k-37k tokens with tools) exceeds the free tier TPM.

Solutions:

Switch to Ask mode (no tools, ~1k token payload)
Use Llama 4 Scout (TPM=30,000)
Reduce maxInputTokens (but > 21k to avoid pruning bug)

`context_length_exceeded` in Cerebras

Cause: Cerebras has a context window of 8,192 tokens (not 30k).

Solution: Reduce maxInputTokens to 7000. Don't attach large files.

Models don't appear in picker

Cause 1: You're in Agent mode and the model has toolCalling: false. Solution: Switch to Ask mode.

Cause 2: The model is hidden in state.vscdb. Solution: Chat: Manage Language Models → click the model's eye icon.

See docs/bugs-found.md for the complete analysis of each error.

Free Tier Limits

Groq Free Tier (March 2026)

Model	RPM	RPD	TPM	TPD
`llama-3.1-8b-instant`	30	14,400	6,000	500,000
`llama-3.3-70b-versatile`	30	1,000	12,000	100,000
`meta-llama/llama-4-scout-17b-16e-instruct`	30	1,000	30,000	500,000
`qwen/qwen3-32b`	60	1,000	6,000	500,000
`openai/gpt-oss-120b`	30	1,000	8,000	200,000
`openai/gpt-oss-20b`	30	1,000	8,000	200,000

Cerebras Free Trial

Model	RPM	TPM	Context window
`gpt-oss-120b`	5	30,000	8,192
`zai-glm-4.7`	5	30,000	8,192
`gemma-4-31b`	1	30,000	8,192

OpenRouter Free Tier

23 :free models available (June 2026)
Up to 1M tokens of context in some models
They change constantly

Gemini Free Tier

20 requests/day per model
39 models available

Documentation

Complete Report — Exhaustive technical documentation (1,500+ lines)
Bugs Found — Analysis of each bug and its root cause
Architecture — Request flow diagram
References — Links to official docs and GitHub issues

Contributing

Contributions are welcome! Please:

Fork the repository
Create a feature branch (git checkout -b feature/new-feature)
Commit your changes (git commit -m 'Add new feature')
Push to the branch (git push origin feature/new-feature)
Open a Pull Request

Areas needing help

Adapt scripts for Linux/macOS (bash/zsh)
Support for more providers (Mistral, DeepSeek, Together AI)
Uninstall script
Automated tests
CI/CD with GitHub Actions

Acknowledgments

Microsoft VS Code team — for the official BYOK documentation
Groq — for the generous free tier
Cerebras — for ultra-fast inference
OpenRouter — for the model aggregator
Google AI Studio — for the Gemini free tier
r/GithubCopilot community — for reporting bugs and sharing solutions

Disclaimer

This project is NOT affiliated with Microsoft, GitHub, Groq, Cerebras, OpenRouter, or Google
API keys used in examples are for illustration and should be replaced with your own
Each provider's free tier may change without notice
The No lowest priority node found bug is a VS Code bug, not a bug in this project

Found this useful? Star the repo and share it with the community.

Name		Name	Last commit message	Last commit date
Latest commit History 5 Commits
config		config
docs		docs
references		references
scripts		scripts
.gitignore		.gitignore
CHANGELOG.md		CHANGELOG.md
LICENSE		LICENSE
README.md		README.md

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