codex-cli --reasoning-effort flag does not exist (v0.128.0). Scripts using codex exec --model X --reasoning-effort high will 100% fail at first auth’d invocation despite parsing successfully when the model is wrong/missing.
Diagnosis
codex-cli (v0.128.0) exposes reasoning effort ONLY via the TOML config-override pattern: -c model_reasoning_effort=<low|medium|high>. There is no --reasoning-effort CLI flag. The flag was assumed during initial CCVS gate-script design and would have failed silently parsing-wise but caused immediate auth/exec failures when first run authenticated. Premortem #3 (“codex exec flag syntax must be verified”) explicitly predicted this risk class.
Fix
Use -c model_reasoning_effort=<level> config override. Works on both codex exec and codex exec review subcommands. --profile <tier> only works on top-level codex exec, NOT on codex exec review — for review subcommand always use -c. Other essential flags: --skip-git-repo-check (hooks may run outside repo), --ephemeral (no session pollution), -o <file> (clean last-message extraction). Don’t pin -m gpt-5.5 — let it auto-resolve via codex login auth (Pro tier auto-engages on Pro login).