Use ChatGPT (GPT-5.4) inside Freebuff with BYOK

Bring your own ChatGPT key for free, deeper reasoning passes.

FT
The Freebuff TeamBuilding the free coding agent
··5 min read

TL;DR

  • Freebuff supports BYOK for OpenAI — use your ChatGPT account’s API key.
  • The agent loop stays free; only token usage on your key counts.
  • Best fit: deep architecture passes, hard debugging, security review.

When to BYOK ChatGPT#

  • Hard architecture decisions where you want GPT-5.4 Pro’s extended reasoning.
  • Security review of authentication or crypto code.
  • Cross-paradigm refactors (e.g., callbacks → async/await across 40 files).
  • Final pass before a critical PR.

Setup (90 seconds)#

# 1. Get a key at platform.openai.com
export OPENAI_API_KEY=sk-...

# 2. Start Freebuff
freebuff

# 3. Switch to GPT-5.4 in-session
/model gpt-5.4-medium

Freebuff keeps the agent loop, tool calls, and subagent orchestration free. You’re only paying OpenAI for the tokens the planner consumes.

Best workflow: free model for execution, BYOK for planning#

FeatureFreebuffBYOK-only setups (OpenCode, Aider)
Agent loop costFreePaid (per call)
Plan with GPT-5.4$0.40 – $1.50 / hour activeSame
Execute with free modelsYes — DeepSeek V4 Pro freeNo
Browser-use includedYesNo
Subagents9 specialized1

Get ChatGPT in your CLI for free

Install Freebuff and bring your existing OpenAI key.

Install Freebuff

About the author

FT

The Freebuff Team· Building the free coding agent

We build Freebuff — the free CLI coding agent — and Freebuff Web, the free way to ship full-stack apps. No subscription, no setup, no lock-in.

Topics:byok chatgptchatgpt inside freebuffgpt-5 cli agentfree chatgpt coding agentopenai key with freebufffree codex alternativefree claude code

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