Salvage of #79604 (webtecnica) + #85721 (pierrenode), combined and
rebased onto current main with simplify-code findings folded in.
#79604: update_session_model() wrote the model name to sessions.model
but never persisted the provider into model_config. On resume, the
runtime recombined the persisted model with the config.yaml primary
provider (which may not serve that model), producing auth errors.
Fix: add optional provider parameter to update_session_model, merged
into model_config via the shared _merge_model_config_json helper (not
hand-rolled SQL). Wire both gateway /model call sites to pass
result.target_provider.
#85721: session_gateway_runtime() had no billing_provider fallback.
A CLI session that never ran /model has no gateway_runtime or
top-level provider in model_config — billing_provider (written on
every session's first accounted API call) is the only durable record.
Fix: add billing_provider as the last-resort fallback in
session_gateway_runtime(), filtering bare billing buckets (auto/custom)
that are not routable identities.
Simplify-code findings addressed:
- Use _merge_model_config_json instead of 40 lines of branched SQL
- Share _BARE_BILLING_PROVIDERS from hermes_state.py (was duplicated
as a set in tui_gateway/server.py)
- Merge None-filtering from #85920 with the billing_provider fallback
into one coherent return path
Co-authored-by: pierrenode <298902573+pierrenode@users.noreply.github.com>
