bjornmelin/codex-delegate

Codex Delegate

Hand a task to the gpt-5.6 family through the Codex CLI. This is the delegation path per MODELS.md: the main loop (Fable) 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 Fable 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 | |---|---|---| | bulk | gpt-5.6-luna + "high" (high ONLY) | retrieval, repo mapping, inventories, dependency tracing, evidence extraction, routine low-risk clear-spec bulk edits | | worker | gpt-5.6-sol + "medium" | implementation, debugging, code review, bounded analysis/synthesis | | lead | gpt-5.6-sol + "high" | consequential/cross-cutting backend work, difficult debugging, planning, research synthesis | | validator | gpt-5.6-terra + "max" (max ONLY) | one independent adversarial check or alternate solution AFTER Sol high - not a routine worker or generic escalation tier | | last resort | gpt-5.6-sol + "max" | root-gated; see below |

Escalation ladder: Luna high → Sol medium → Sol high, then one of: Fable finishes the hard part inline, Terra max runs one adversarial/alternate pass, or (rarely) Sol max.

Bans: no Sol xhigh or ultra; no Luna effort other than high; no Terra effort other than max; never mini/spark-class models. Sol max requires one of: critical blast radius with no cheap deterministic oracle; unresolved disagreement after Sol high + Terra max; two failed strong attempts; a hard implementation that materially benefits from Codex repo/tool context. Only one active Sol max call.

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, bulk lane)
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, worker lane) - ALWAYS pass the sandbox
# explicitly; never inherit the config default (danger-full-access)
codex exec -C "<repo>" -m gpt-5.6-sol -c model_reasoning_effort="medium" --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 Fable closes it:

1. git diff - review what Codex actually changed before accepting it.
2. Run the relevant deterministic checks (tests / type-check / lint / build) and iterate until green.
3. 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-4.8/Fable inline) without asking - judge the output, not the price.