[quickbeard]

Two defects found by the first real in-app sandbox chat on macOS. Either one alone left a sandbox unable to reach a model, so the broker work (#209) has never actually served a completion until now.

1. Gateway URL never resolved

resolveSandboxEgress required base_url from the hub auth file — but that field is only written by the custom-provider flow. An SSO login records gateway_url instead, which is the common case. Result: gateway resolved to null, so the sandbox got no broker routes and a guest config containing only {"permission":"allow"} — no provider at all. Observed directly in the guest:

$ cat /codev-config/codev.json
{ "permission": "allow" }

Fix: fall back to loadGatewayUrl(), which normalizeGatewayBaseUrl turns into exactly the /v1 base the host's own working config uses (verified against ~/.config/codev/codev.jsonc: https://netmind.viettel.vn/gateway/v1).

2. Electron's net.fetch rejects streamed request bodies

With the config fixed, the guest reached the broker and every request came back Bad Gateway: net::ERR_INVALID_ARGUMENT. The broker forwards the guest's request body as a stream (Readable.toWeb) plus duplex: "half"; net.fetch accepts neither. Fix: buffer the body in the desktop's fetchImpl and drop duplex. Model requests are small JSON payloads, and the response stays streamed, which is what token streaming needs.

Verification

A real completion, requested from inside the NIC-less guest over the full chain (guest loopback → vsock → host broker → token swap → gateway):

{"id":"chatcmpl-…","model":"MiniMax/MiniMax-M3",
 "choices":[…],"usage":{"prompt_tokens":185,"total_tokens":195}}

Also confirmed in the same run: the guest config now carries the netgate provider pointed at http://127.0.0.1:8788/llm/v1 with the placeholder key (real token stays host-side), and permission: "allow" from #210.

Fork-only file; no DIVERGENCES row. No CHANGELOG entry — this fixes #209/#212 work that is still under Unreleased, so the existing entry describes the shipped behavior correctly.

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