Pen's chat on your Claude subscription

Pen.app has an agent chat of its own, separate from /pen-design. It does not talk to Anthropic directly — it starts the Claude Code CLI on your machine, so your Claude subscription pays for those prompts.

No Anthropic API key is stored for this — not in Pen's own key field, and not as ANTHROPIC_API_KEY in your environment. A set variable makes Claude Code skip the subscription login and bill that key per token instead, which is the one outcome this path avoids. echo $ANTHROPIC_API_KEY must print nothing before you start; whatever it prints belongs out of your shell profile.

Four steps

1. Install Claude Code, if it is not there yet:

bash

curl -fsSL https://claude.ai/install.sh | bash

Homebrew works too (brew install --cask claude-code), but it does not update itself. claude --version must print a version followed by (Claude Code).

2. Log in once. Start the CLI and follow the browser prompt:

bash

claude

Pick your subscription account — Pro, Max, Team or Enterprise. /login inside a running session switches accounts later.

3. Point Pen at it. In Pen's agent settings under Anthropic Claude Code, select Your Claude Code settings (e.g. subscription) under AUTHENTICATION. The status leaves Checking status… once the CLI is found and logged in.

4. If Pen cannot find the CLI, put the full path into Claude executable under ADVANCED:

bash

which claude

macOS GUI apps do not inherit your shell's PATH, which is why the field exists. A native install sits at ~/.local/bin/claude, Homebrew on Apple Silicon at /opt/homebrew/bin/claude.

The one trap

A Console login looks exactly like a subscription login in the browser, but it creates a "Claude Code" workspace and spends pre-paid credit per token. The account picker is the only place the difference shows.

Not the same as pen login

Two subscriptions meet in Pen and they pay for different things:

	Pays for
Claude subscription	the prompts in Pen's own agent chat, through the Claude Code CLI
pen.dev subscription (pen login)	the pen CLI and pencil MCP that /pen-design drives

Both are subscriptions, and neither wants an agent API key.