instance.go:
- Add Router *routing.Router and LightCandidates []FallbackCandidate
to AgentInstance.
- At agent creation, when routing.enabled and light_model resolves
successfully in model_list, pre-build the Router and resolve the
light model candidates once. If the light model isn't in model_list,
log a warning and disable routing for that agent gracefully.
loop.go:
- Add selectCandidates(agent, userMsg, history) helper.
It calls Router.SelectModel and returns either agent.Candidates /
agent.Model (primary tier) or agent.LightCandidates / light_model
(light tier). Returns primary unchanged when routing is disabled.
- In runLLMIteration, resolve (activeCandidates, activeModel) once
before entering the tool-iteration loop. The model tier is sticky
for the entire turn so a multi-step tool chain doesn't switch
models mid-way.
- Replace hard-coded agent.Candidates / agent.Model references in
callLLM and the debug log with the resolved active values.
The fallback chain and retry logic are untouched. When light_model
returns an error the fallback chain handles escalation normally.
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