feat: querypad mcp-attach - bridge stdio to an app-hosted MCP socket - #27
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The desktop app's data channel (ROADMAP step 8 phase 3) works by hosting the MCP conversation on a Unix socket the app owns: the app spawns querypad mcp over stdio, listens on the socket, and proxies frames between the two - which puts every tool call and result set in the app's hands to drive native panels. Claude Code cannot connect to a socket; it spawns a stdio command or calls HTTP. This is the missing wire: claude mcp add datactx -- querypad mcp-attach /tmp/datactx.sock Deliberately dumb - no framing, no parsing, no buffering policy. The app and the engine own the protocol. The engine is untouched, which keeps the architecture rule intact: surfaces stay thin, and stdio remains the only transport the server knows. e2e-tested both directions through a real socket, plus the loud failure when the socket is absent.
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Why
The desktop app's data channel (ROADMAP step 8 phase 3) hosts the MCP conversation on a Unix socket the app owns: the app spawns
querypad mcpover stdio, listens on the socket, and proxies frames between the two. That puts every tool call and result set in the app's hands to drive native panels - the difference between a pretty terminal and a data cockpit.Claude Code cannot connect to a socket; it spawns a stdio command or calls HTTP. This is the missing wire:
What
A byte-for-byte stdio-to-socket bridge, ~35 lines. Deliberately dumb: no framing, no parsing, no buffering policy of its own - the app and the engine own the protocol.
The engine is untouched, which keeps the architecture rule intact: surfaces stay thin, and stdio remains the only transport the server knows.
Verification
npm run checkexit 0;npm run test:cli150 pass / 0 fail🤖 Generated with Claude Code
https://claude.ai/code/session_01CKZ9UVgw2Mhiu6T5YAG7k6