Pipepost v0.9.0 — Substack publishing + the agent-loop transcript

#mcp #claudecode #substack #typescript

Pipepost v0.9.0 — Substack publishing + the agent-loop transcript

You can now publish to Substack from Claude Code. That makes 6 CMS platforms in a single MCP server: Dev.to, Ghost, Hashnode, WordPress, Medium, and Substack.

But the more interesting part of v0.9.0 isn't a new platform. It's a transcript showing what an agent-loop publishing pipeline actually looks like.

What an agent loop replaces

If you publish to multiple platforms today, the manual flow is roughly:

Open Dev.to, paste, format, tag, save draft
Open Ghost admin, paste, format, set canonical URL, save draft
Open Hashnode, paste, format, set canonical URL, save draft
Open WordPress, paste, format, set canonical URL, save draft
Open Substack, paste, format, save draft
Open three SEO tools — one for scoring, one for meta tags, one for schema
Open Twitter compose, write a thread of 4 tweets
Open LinkedIn, write a professional version of the same post
Open Bluesky, write a 287-character version
Open Bing Webmaster Tools, paste the URL, click submit

Realistic time: 45 to 90 minutes of context switching.

The agent-loop version of that flow is one prompt:

Take this draft, audit it, score it for SEO, fix any issues, cross-publish to Dev.to, Ghost, Hashnode, WordPress and Substack as drafts with the Dev.to URL as the canonical, generate Twitter + LinkedIn + Bluesky posts, and submit the Dev.to URL to IndexNow.

Claude Code chains the calls, threads the canonical URL between them, prints the output, and asks if you want to flip the drafts to published.

The full annotated transcript is in the repo: docs/demo/agent-loop.md.

The Substack piece

Substack does not have a public API. The publish tool now talks to Substack's reverse-engineered endpoints:

POST /api/v1/drafts to create
POST /api/v1/drafts/{id}/publish to publish
Cookie auth via connect.sid (DevTools → Application → Cookies → substack.com)
Markdown converted to ProseMirror documents (paragraphs, headings, code blocks, blockquotes, bullet lists, inline bold/italic/code/links)
user_id resolved from /api/v1/user/profile/self on first publish, then cached in ~/.pipepost/config.json

Setup:

npx pipepost-mcp init
# then in Claude Code:
# setup platform=substack connect_sid=<cookie> publication_url=https://you.substack.com
# publish platform=substack title="..." content="..." status=draft