pen.dev vs Subframe

pen.dev

An agent can create, edit and export .pen designs without a GUI through the pen CLI, with four compact MCP tools that carry annotations and a documented JSON format. The software is closed and needs a pen.dev account. No changelog, status page or security contact was found, and 14 public issue reports had no reply on 8 October 2026.

Subframe

An agent can read and change pages, components, snippets and themes in a Subframe project through a hosted MCP server with OAuth, and Viewer accounts get a read-only server. The server lists 46 tools, and no status page, rate limits, changelog or security contact were found. Three tools were renamed in September 2026 with no notice found.

pen.dev

1. Call read_skill(), then read_skill({ path: "pen-schema.md" }) and read_skill({ path: "execute.md" }) before the first execute. The tool description alone doesn't document the operations
2. Call get_app_state() and confirm the active document before editing. The MCP server works on whichever .pen file is open in the app
3. In headless pen interactive, call save() before exit(), and keep --in and --out on different paths to preserve the source
4. Check that an export file exists. The docs say an export failure can print an error without a nonzero exit status
5. In CI set PEN_CLI_KEY plus a provider key such as ANTHROPIC_API_KEY. Run pen version, since pen --version is not a flag

Subframe

1. Connect with an MCP client that supports OAuth. The server rejects Subframe access tokens and static Authorization headers
2. Pass projectId on every call. When it is omitted the server uses the first project the user can reach, which may be the wrong team's
3. After design_page, design_component or edit_component, call wait_for_jobs with the jobId before reading the result. Earlier reads return stale content
4. Ask the owner before any delete tool or a theme token deletion. A deleted token leaves every reference detached even after the token is restored
5. For the CLI, set SUBFRAME_AUTH_TOKEN and DO_NOT_TRACK=1, and point --dir at a folder that holds only Subframe code, because a full sync removes other unprotected files