Why: when mcpd's inference proxy is unreachable, clients with a local
vllm-managed provider should be able to substitute — but only if they still
have view permission on the centralized Llm. Otherwise revoking an Llm
wouldn't actually stop a misbehaving client.
Infrastructure (the agent + mcplocal HTTP-mode wire-up will land separately
when those clients pivot to mcpd's proxy):
- LlmProviderFileEntry gains optional `failoverFor: <central llm name>`. The
entry is otherwise the same local provider it always was; the new field
just declares which central Llm it can substitute for.
- ProviderRegistry tracks a failover map (registerFailover / getFailoverFor /
listFailovers). Unregister removes any failover entry pointing at the
removed provider so we don't end up with dangling references.
- New FailoverRouter wraps a primary inference call. On primary failure: if
a local provider is registered for the Llm, HEAD-probe `mcpd /api/v1/llms/
:name` with the caller's bearer to verify view permission, then either
invoke the local provider (allowed) or re-throw the primary error (403,
401, network unreachable, anything else — all fail-closed).
- Server: GET /api/v1/llms/:idOrName accepts both CUID and human name. Lets
FailoverRouter probe by name without a separate id-resolution call. HEAD
derives automatically from GET in Fastify, which runs the same RBAC hook
and drops the body — exactly what the probe needs.
Tests: 11 failover unit tests (registry map, decision flow, fail-closed for
forbidden + unreachable, checkAuth status mapping) + 4 new route tests
(name lookup, HEAD existing/missing). Full suite 1844/1844 (+14 from Phase
2's 1830). TypeScript clean across mcpd + mcplocal.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
