Hand a task to the gpt-5.6 family through the Codex CLI. This is the delegation path per MODELS.md: the main loop (Root) invokes Codex directly through Bash - no Claude shim, and never a Claude worker whose only job is to launch, wait for, or relay a Codex call.
Delegation gate (from MODELS.md - check before delegating at all)
Delegate only when at least one shape applies: independence (fresh-eyes or
adversarial value), context (repo/research mass stays out of the root
context), contract (clear-spec implementation with a written contract,
roughly >=2h), or parallel (independent taste-free lanes save wall-clock).
Otherwise Root works inline. Cap concurrent model lanes at 2-3.
Never route design/UI/copy/naming/API-ergonomics or final architecture decisions to codex.
Model + effort routing (always pin BOTH -m and effort - never inherit defaults)
| lane | pin | use |
|---|---|---|
| default | gpt-5.6-luna + "max" |
almost everything: implementation, debugging, code review, retrieval, repo mapping, inventories, dependency tracing, bounded analysis and synthesis |
| fast | gpt-5.6-luna + "high" |
latency-sensitive work: exploration, file and symbol location, shallow inventories, a quick second read - anywhere a fast good answer beats a slow better one |
| maximum intelligence | gpt-5.6-terra + "max" |
one independent adversarial check or alternate solution, and the rare task Luna max cannot carry |
| last resort | gpt-5.6-sol + "max" |
rare and root-gated; burns quota disproportionately |
Rationale, per the MODELS.md recalibration dated 2026-08-01: Luna is substantially cheaper than when the old Sol ladder was written and its weekly limits are effectively unlimited, so it is the default at max effort; Terra earns its premium over Luna max only when the last few points of capability are load-bearing. The Sol medium/high worker tiers are retired.
These are commercial terms, not stable facts — they were true at that recalibration and will drift. Re-check them against current provider pricing before treating cost as the reason for a routing decision, and prefer the measured latency figures below, which do not depend on pricing.
Quota is no longer the binding constraint on Luna; wall-clock is. Measured on one read-only analysis lane over a single component and its imports:
| effort | wall clock | tokens | findings |
|---|---|---|---|
high |
~4 min | ~75k | 2 of 6 |
max |
~14 min | ~153k | 6 of 6 |
The gap is traversal depth, not polish: the fast lane never entered
node_modules, so it missed everything that depended on what an installed
dependency actually does — including a high-confidence defect. Treat high as a
genuinely shallower read, not a cheaper version of the same read. Use it for
exploration and location, where a fast partial answer is the point, and max
for depth-sensitive work where the answer turns on what a dependency or a
distant file actually does.
Effort is a depth signal, not a completeness guarantee. Nothing about a
reasoning tier establishes that the scope was covered or the claims verified -
only explicit scope, coverage, and verification evidence does that. Do not
report a max lane as complete merely because it ran at max.
Escalation ladder: Luna high → Luna max → Terra max → Root finishes the hard part inline (or an Opus high worker when a delegation shape holds). Sol max requires one of: critical blast radius with no cheap deterministic oracle; unresolved disagreement after Luna max and Terra max; two failed strong attempts. Only one active Sol max call.
Bans: no Sol xhigh or ultra; no Terra effort other than max; never mini/spark-class models.
Consequential or cross-cutting implementation still routes to Opus high workers or Root inline per MODELS.md; Codex is the independent second opinion there, or the primary when Claude quota is the binding constraint.
Composing the prompt
Codex sees NONE of the Claude conversation - prompts must be fully
self-contained: objective and expected deliverable, exact scope/files and
ownership, relevant context and constraints, permitted edits and sandbox,
required checks, output format and completion criteria. For structured
returns, pass --output-schema <schema.json>.
Invocation
# Investigation / retrieval (read-only, default lane)
codex exec -C "<repo>" -m gpt-5.6-luna -c model_reasoning_effort="max" --sandbox read-only --output-last-message "<scratchpad>/codex-out-<ts>.md" "<self-contained prompt>"
# Fast exploration (read-only) - trade depth for latency
codex exec -C "<repo>" -m gpt-5.6-luna -c model_reasoning_effort="high" --sandbox read-only --output-last-message "<scratchpad>/codex-out-<ts>.md" "<self-contained prompt>"
# Implementation (write-capable) - ALWAYS pass the sandbox
# explicitly; never inherit the config default (danger-full-access)
codex exec -C "<repo>" -m gpt-5.6-luna -c model_reasoning_effort="max" --sandbox workspace-write --output-last-message "<scratchpad>/codex-out-<ts>.md" "<self-contained prompt>"
Rules:
- ONE bare command per call - no pipes, no
cd &&chains (keeps the RTK hook inert). - Outside a git repository, add
--skip-git-repo-check(codex exec errors there otherwise). - Short blocking calls: foreground Bash. Long or parallel calls: Bash
run_in_background: true; read the result file when the harness notifies - inspect logs only on failure or empty output. Never attach a Monitor just to detect completion. - Use isolated worktrees when parallel writers could overlap; one owner per file/domain.
- Follow-ups continue the same Codex session:
codex exec resume --last "<follow-up instruction>". Sessions are looked up from the working directory, so run this from the same cwd/repo scope as the original call (or pass the recorded session id instead of--last).
Closing the loop
Delegated output is provisional until Root closes it:
git diff- review what Codex actually changed before accepting it.- Run the relevant deterministic checks (tests / type-check / lint / build) and iterate until green.
- If Codex went beyond the delegated scope, revert the extra scope and re-delegate with tighter constraints.
If output misses the bar, escalate up the ladder (or redo on opus-5/Root inline) without asking - judge the output, not the price.