This work order is complete for the original PR implementation. The 2026-09-15
amendment in Task 02 supersedes its implicit
strict predicate. Its transport, warning, and validated-reuse fixes remain.
The original scope below is historical, not the current compatibility contract.
Change
Apply the shared start-model policy before the first inference on every
launch path: initial session start, context reset, and fresh ACP
workspace-rebind sessions. A concrete profile with a non-empty model,
auto_fallback=false, and no fallback_model must fail the launch before
a prompt or tool call when the executor does not advertise the configured
model; no speculative SetModel is sent for an unadvertised model.
Workflow step entry must also isolate stale runtime identity: a parked
session whose persisted provider model disagrees with the destination
profile's configured model policy is replaced with a fresh session before
any auto-start prompt runs. Explicit fallback_model and auto_fallback
profiles remain the only authorized deviation paths, each with one durable
warning.
Verification
go test ./internal/agent/runtime/lifecycle covers
TestApplyStartModelPolicy behavior for advertised, fallback, and
unauthorized substitution cases (start_model.go,
start_model_executor_authority_test.go).
go test ./internal/orchestrator covers session isolation on workflow
entry (event_handlers_workflow.go,
event_handlers_workflow_profile_session_policy_resolution_test.go,
event_handlers_workflow_profile_session_policy_test.go).
Turn/message attribution and pre-prompt warnings agree on the effective
model; failures never expose credentials or provider secrets.
Alassane
739eabc49a