A free open-source thinking partner for coding agents — mediates dialogue between Claude Code, Codex CLI, Cursor, Cline, and more via MCP.
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 # Quill — *ask another mind.* **Free, MIT-licensed open source. A working product *and* an active research project on coding-agent collaboration.** Quill mediates dialogue between the AI doing the work and a second AI giving perspective. The headline: **if you have a Claude Pro and a Codex Pro subscription, you have a free dual-AI coding setup.** No API key required, no per-token cost — Quill shells out to whichever CLIs you have installed and relays their conversation. Built by [YG3](https://yg3.ai). See [RESEARCH.md](RESEARCH.md) for the research direction. Four skills available in any agentic CLI Quill is installed in: - **`consult`** — for stuck/frustrated moments. Quill's advisor reframes what's actually going on. - **`perspective`** — for exploring/curious moments. Layers in a vantage the doer hasn't taken. - **`assumptions`** — for "what choices is the AI making that I don't understand?" Translates technical assumptions into plain-language yes/no questions. - **`mosaic`** *(new in v0.2)* — for multi-aspect tasks. Decomposes the task into 2-4 voice-assigned slices, runs them in parallel with independent priors preserved, cross-reviews for consistency without homogenizing voice. The seams between agents stay visible *on purpose* — preserved texture diversity is the value. See [MOSAIC_DESIGN.md](MOSAIC_DESIGN.md) for the design rationale. In Claude Code specifically, you also get safety hooks (gatekeeper for risky shell commands) and pre-push quality scans (secrets, debug statements, TODOs, .env files). ## The four ways to run Quill Pick the doer (the agent in your terminal) × the advisor (who Quill calls when you ask for perspective): | Doer (your terminal) | Advisor (Quill calls) | Cost | Setup | |---|---|---|---| | **Claude Code** | **Codex CLI** | Free (Codex Pro) | `ADVISOR_BACKEND=codex_cli` | | **Codex CLI** | **Claude CLI** | Free (Claude Pro) | `ADVISOR_BACKEND=claud…
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