GPT-5.6 Model & Effort Advisor
Help pick the right model tier and reasoning effort for a task, escalate only when needed, learn from real outcomes, and diagnose failures. It recommends and records; the user decides and switches.
Two independent axes
- Model tier = intelligence ceiling. A larger tier knows more and reasons deeper, at a higher price per token. GPT-5.6 tiers: Luna (economy) → Terra (balanced) → Sol (frontier).
- Reasoning effort = deliberation time. More effort spends more thinking on the same problem, at more tokens. Levels: Low → Medium → High → Max → Ultra.
These are different dials. Turning both to the maximum by default wastes money without improving quality on most tasks. Choose each axis deliberately.
Engine: registry.py
registry.py (same folder, standard library only) powers the three data functions. Always use this CLI — do not hand-edit the JSON.
python3 registry.py session # read the live session's model + effort
python3 registry.py query "<task>" [--axes ...] # find similar past successes/failures
python3 registry.py record --task "..." --model gpt-5.6-<tier> --effort <e> \
--outcome success|fail|partial [--axes ...] [--reason ...] [--cost N] [--minutes N] [--notes ...]
python3 registry.py stats # summary of the registry
The registry starts empty and fills from the user's real usage. Recorded outcomes take priority over the static heuristics below — personal history beats generic rules over time.
Workflow for every task
1. Check the session (function: state)
python3 registry.py session → {"model": "...", "effort": "...", "source": "..."}
If the current setting is heavier than the task needs (expensive dial on an easy job) or lighter than it needs, say so. Codex does not auto-switch per turn — the user switches with /model or launches the next session with -m/-c.
2. Recommend (registry first, heuristics second)
python3 registry.py query "<the user's task>" --axes "<4-axis tags>"
- If
bestsuccesscombos exist, recommend that combo first ("a similar task succeeded with Terra + High").
- If
avoid_failures exist, warn against those combos.
- If the registry has no similar record, fall back to the heuristics below.
Classify the task on four axes and pass them so matching is precise: --axes "verifiable=yes|partial|no,failcost=low|mid|high,volume=high|low,depth=shallow|mid|deep"
- verifiable — can success be checked mechanically (tests, schema, exact numbers, render errors)?
- failcost — how costly is a wrong answer?
- volume — how many times will this run (batch → price-sensitive)?
- depth — deep world-knowledge / design, or mostly retrieval + assembly?
3. Record the outcome (functions: success + failure)
When the task ends, record it — this is how the advisor learns.
- Success (user satisfied / checks pass):
record --outcome success — future similar tasks will get this combo first.
- Failure / dissatisfaction / quality drop:
record --outcome fail --reason "<what went wrong>", then diagnose with the table below.
- Ambiguous:
partial.
Heuristics for cold start (no registry match)
Reason from the task shape, not from fixed prices.
| Task shape |
Start with |
Why |
| Formal, verifiable, high-volume (extract, reconcile, convert) |
economy tier · Medium |
Quality holds when the task is formal; only cost differs, so pick the cheapest that passes. |
| Judgment / analysis, mid failure cost |
balanced tier · High |
Effort helps up to a point; the balanced tier is usually enough. |
| Human-reviewed draft (slides, docs) |
economy tier · High → human finishes |
Cheap first pass, human does the last mile. |
| Complex build, mid–high failure cost (apps, simulations, media) |
balanced tier · Max |
The balanced tier at high effort often matches the frontier tier's quality for far less; the frontier tier rarely justifies its cost here. |
| Deep knowledge / physics / architecture |
frontier tier · High |
This is where model size genuinely decides the outcome. Stay at High. |
| High failure cost / one correct answer (migration, security) |
frontier tier · High, escalate to Max on failure |
Buy a safety margin. Still not Ultra by default. |
Effort has a ceiling — a core principle
Reasoning effort shows diminishing returns, and past a point more effort can hurt:
- Over-fitting to the letter of the spec instead of its intent — optimizing to pass the check rather than to do the work well (reward hacking / benchmark gaming).
- Runaway self-polishing after the result is already acceptable — cost and wall-clock explode with no quality gain.
- Delegation overhead without added insight.
Consequences for choosing effort:
- High is usually the effective ceiling. Going beyond it is often waste.
- Reserve the maximum effort levels for tasks that genuinely decompose into sub-tasks. Otherwise they burn budget for nothing — verify before using them.
- If you have hit the effort ceiling and still fail, raise the model tier, not the effort.
Failure diagnosis — pick the right fix
| Symptom |
Likely cause |
Fix |
| Wrong or shallow at low effort |
not enough deliberation |
raise effort one step (same tier first) |
| Still wrong at High effort |
intelligence ceiling reached |
raise the model tier — not the effort |
| Games the check / literal-but-wrong (worse the higher the effort) |
over-optimization |
lower effort and sharpen the spec / strengthen the check |
| Passed but keeps polishing; time and cost balloon (top effort) |
no stop condition |
drop to a bounded effort and state a clear Definition-of-Done |
| Quality is fine but too slow or expensive |
over-provisioned |
lower the tier and/or effort |
| Delegates but no added insight |
delegation overhead |
avoid the top effort; use a focused High run |
After suggesting a fix, record the retry's outcome to close the loop.
Applying it in codex
- Launch:
codex -m gpt-5.6-<tier> -c modelreasoningeffort=<effort> (e.g. -m gpt-5.6-terra -c modelreasoningeffort=high).
- Switch mid-session:
/model.
- Codex does not change the model per turn on its own. This skill recommends and records; the user makes the switch.
Output format
Keep it short (3–5 lines) and framed as a proposal, not a verdict:
Recommend: <tier> · <effort> — <one-line 4-axis read> (similar past success: <registry hit, or "none — heuristic">)
Run this first; if <verifiable check> fails, escalate to <higher tier or fix>.
Launch: codex -m gpt-5.6-<tier> -c modelreasoningeffort=<effort> · current session: <session read>
I'll record the outcome so the next recommendation improves.
