MCP OAuth: browser-open + callback forwarding (desktop + WSL) (flakes-mqe9)


Status	Todo
Type	Feature
Priority	normal
Tags	mcp, containers
Parent	Container-first infrastructure (flakes-qbvb)
Subtasks	Host-desktop: callback forward + xdg-open auto-open (flakes-ok62)
	WSL: callback forward + wslview auto-open (flakes-q3l5)
	Phase A: container browser-open script (OSC) (flakes-vzo1)

Completes the MCP OAuth bridge: the container-side callback relay is done (flakes-wq6s). This bean covers opening the authorize URL where the human actually is and routing the callback back, for the two real access patterns (there is no Mac/lima in this setup — superseding the original external-Mac framing).

Access patterns

Case 1 — host Linux desktop → incus exec → container. Browser = host xdg-open. Callback localhost:3118 = the host.
Case 2 — Windows → WSL (Ubuntu, home-manager-managed by this repo) → ssh host → incus exec → container. Browser = Windows default browser, opened from WSL via wslview/cmd.exe /c start. Callback localhost:3118 = Windows → WSL localhost forwarding.

Unification

The container always reaches the host at its bridge gateway (10.100.0.1), self-discoverable inside the container via ip -4 route show default (must be derived in the container, not the attach wrapper — on the host default is the uplink). No hardcoded IPs; optional me.hostBridgeIp override for odd setups. Host-side listeners bind the incus bridge address (incus network get incusbr0 ipv4.address).

	Case 1 (host desktop)	Case 2 (Windows→WSL→SSH)
Detect (attach)	no `SSH_CONNECTION`, `WAYLAND_DISPLAY` set	`SSH_CONNECTION` set
Open URL	container→`gateway:OPEN`→host `xdg-open` listener	container→`gateway:OPEN`→host `ssh -R`→WSL listener→`wslview`
Callback	host `127.0.0.1:3118 → container:3118` (socat/systemd-proxy)	WSL `ssh -L 3118:<container>:3118`

Phasing

Phase A (universal, no detection): container $BROWSER (+ xdg-open shim) writes the URL to the human’s TTY as OSC 8 hyperlink + OSC 52 clipboard + plain text + bell. Lands on whichever terminal the human is at (host desktop or Windows Terminal via WSL/SSH), survives zellij detach/reattach, one click. → child bean (implemented first).
Phase B (zero-click): Case 1 host systemd --user xdg-open listener on the bridge IP; Case 2 WSL wslview listener + ssh -R back-tunnel + host sshd GatewayPorts clientspecified. Attach-time detection injects BROWSER_ROUTE; OSC stays the fallback for moved/stale sessions.

Callback forwards (needed even in Phase A)

Case 1: host socat/systemd-socket-proxyd 127.0.0.1:3118 → 10.100.0.100:3118.
Case 2: WSL programs.ssh.matchBlocks.<host> LocalForward 3118 10.100.0.100:3118 (Windows localhost:3118 → WSL → host → container Caddy bridge → CC).

Children

Phase A — container browser-open script (OSC).
Host-desktop side — callback socat + Phase B xdg-open listener.
WSL side — callback LocalForward + Phase B wslview auto-open + host sshd GatewayPorts.