model_with_provider_context() passed any slash-bearing model ID through
bare when the session provider was not OpenRouter/ACP/plugin and not
listed under config.yaml -> providers:. That dropped the hint for portal
providers (nous, nvidia, opencode-zen, opencode-go) and named custom
providers (custom:<slug>), so resolve_model_provider() fell back to the
profile default provider + base_url and sent a vendor-scoped id to the
wrong endpoint (HTTP 404, e.g. upstage/solar-pro4:free to api.x.ai).
Emit an explicit @provider:model hint for any known routable provider
that differs from the configured default; keep the bare passthrough for
unknown/ambiguous provider slugs so custom/proxy base_url routing stays
in charge. Closes#7333.
Manny7717
da367cc692