663fa68cd4 added an unguarded `agent._read_reasoning_echo_from_config()` call
to switch_model's core field swap. The fake agent here carries only the
attributes switch_model touches, so the new call raises AttributeError inside
the rollback-protected block — every field the test asserts on gets restored
to its pre-swap value and all four cases fail on main with
`assert 'opencode-go' == 'moa'`.
Teach the fake the reader, matching the production AIAgent shape.
The gateway/CLI /model switch path (switch_model in agent_runtime_helpers)
built the MoAClient facade but left agent.api_mode at the value
determine_api_mode / the resolved aggregator transport produced (e.g.
codex_responses or anthropic_messages). The conversation loop dispatches on
agent.api_mode, so a non-chat_completions value made the primary/acting call
go through client.responses.create — which the MoAClient facade has no
.responses for — and fall through to the moa://local placeholder, 404 three
times, then fall back to a reference model (issues #54259, #54669).
agent_init.py already pins api_mode=chat_completions for provider==moa; mirror
that in the live switch so the primary call always routes through
MoAClient.chat.completions. The aggregator's real transport is resolved and
applied inside the reference/aggregator fan-out, not on the outer call.
Brooklyn Nicholson