PATCH /global/config cannot remove a config entry (null is rejected)

Description

PATCH /global/config can add and change config entries but can never delete one.

The body is merged into the existing config, so omitting a key preserves it and {} is a no-op. The only way a merge can express a removal is null, and null is rejected by the payload schema:

$ curl -s -X PATCH localhost:4096/global/config \
    -H 'content-type: application/json' \
    -d '{"provider":{"my-endpoint":null}}'
{"_tag":"BadRequest",...}   # Expected ProviderConfig, got null

{"provider":{"my-endpoint":{}}} returns 200 but leaves the key in place, so there is no workaround through the endpoint.

This means an API client can create a provider / agent / mcp / reference entry but has no supported way to remove it — the only route left is editing opencode.jsonc behind opencode's back, which loses the in-memory update and races the next PATCH.

Worth noting the delete already works internally: both write paths drop a member whose value is undefined (jsonc-parser's modify deletes the key, JSON.stringify omits it) — writableGlobal already relies on this to clear shell. The gap is only that JSON can't carry undefined over the wire, and null isn't accepted in its place.

Plugins

No response

OpenCode version

1.18.10

Steps to reproduce

1. opencode serve
2. curl -X PATCH localhost:4096/global/config -H 'content-type: application/json' -d '{"provider":{"x":{"options":{"baseURL":"http://x"}}}}' — the provider is added
3. curl -X PATCH localhost:4096/global/config -H 'content-type: application/json' -d '{"provider":{"x":null}}' — 400
4. curl -X PATCH localhost:4096/global/config -H 'content-type: application/json' -d '{"provider":{"x":{}}}' — 200, but x is still there

Screenshot and/or share link

No response

Operating System

Ubuntu 24.04

Terminal

iTerm2