Custom subagent role silently inherits parent model/effort on CLI 0.144.5 (Windows)

Related to #14671, which was closed, but reproducible on the current Windows CLI.

Environment

• Codex CLI 0.144.5
• Windows
• Parent session: gpt-5.6-terra / medium
• multi_agent_v2 enabled for this one test invocation

Reproduction

Created a valid custom role at $CODEX_HOME/agents/luna-canary.toml:

name = "luna_canary"
model = "gpt-5.6-luna"
model_reasoning_effort = "low"
description = "Canary profile for a narrow, read-only sub-agent model-routing test."
developer_instructions = "You are a canary sub-agent. Complete only the requested read-only task. Do not edit files or run shell commands."

Then ran a read-only canary requesting exactly one luna_canary child. The named custom subagent was accepted, spawned, and returned CANARY_OK.

Actual behavior

The persisted child-session turn_context recorded:

model = "gpt-5.6-terra"
effort = "medium"
multi_agent_version = "v2"

Those are the parent settings, not the role's explicit Luna/low settings. The role name and instructions were applied, but its model and reasoning configuration were silently ignored.

Expected behavior

The child should run as gpt-5.6-luna with low effort, or Codex should fail clearly before spawning. Silent substitution makes cost and compute governance impossible.

Please expose the effective child model/effort in the UI and logs, and ensure that valid role overrides either take effect or produce an explicit error.