Certified Predictive Value-of-Advice Gating for Cost-Aware Language-Model Guidance in Reinforcement Learning
Organizations: Department of Computer Science, Iowa State University · Standard Chartered, Bangladesh · Department of Computer Science and Engineering, BRAC University, Bangladesh
Abstract
Language-model advice can accelerate reinforcement learning, but calls are costly and returned actions may be stale or wrong. We formulate advice acquisition as a response-contingent metareasoning problem: before querying, the controller predicts possible parsed responses, evaluates the decision and declared continuation that would follow each response, and queries only when a lower confidence bound on predictive value exceeds the priced cost. Execution is governed separately by an action-specific certificate. Under explicit assumptions, certified advice is near-optimal, a wrapped learner inherits fallback regret only under intervention stability, and conservative allocation loses at most the declared query-value estimation error relative to a myopic oracle. On BabyAI, a proxy-calibrated controller with Qwen2.5-1.5B and 7B advisors improves GoToObj return over no querying by 0.029 +/- 0.016 and 0.030 +/- 0.015 across 20 seeds while reducing calls by more than 97% relative to always-query. GoToLocal is a null result. Exactly matched-call tests show an advantage over random placement only for the 1.5B advisor and no advantage over an equal-budget early schedule. Mondrian calibration improves decision-relevant empirical coverage from 0.47 to 0.85, still below the 0.90 target, while the formally covered radius is vacuous. The demonstrated benefit is therefore robust sparse advice volume on a useful task, not a proven per-state placement advantage.
Figures & tables
| Study | Question answered |
|---|---|
| Real advisor | Does selective advice improve return and reduce calls? |
| Matched calls | Is gain due to placement or only volume/schedule? |
| Calibration | Does the deployed radius cover relevant errors? |
| Price sweep | Do actual calls respond to the declared query cost? |
| Corruption | Does the certificate reject harmful advice? |
| Shift/cache | Does invalidation help with budget reserved after shift? |
| Task family | Role | Split/tasks | Horizon | Advisor | Seeds |
|---|---|---|---|---|---|
| BabyAI | Core | GoToObj, GoToLocal | 64 | Qwen2.5-1.5B and 7B | 20 |
| ALFWorld | Extension | pick-and-place, look-at-object | 50 | Simulated ( ) | 5 |
| Crafter | Extension | procedural seed split | 200 | Simulated ( ) | 5 |
| Controlled chain/grid | Diagnostic | exact or clonable | task-specific | known/corrupted | 5 to 20 |
| Estimator | Query-value error | Posterior log score | Surrogate loss | Return | Calls |
|---|---|---|---|---|---|
| No query | 0 | ||||
| Marginal factorization | 0 | ||||
| Candidate-only value | 12 | ||||
| Response-conditioned value | 12 |
| Fallback/history | Fallback gap | Width sum | Bound holds | Log-log slope | Return |
|---|---|---|---|---|---|
| Optimistic, standalone | 20/20 | ||||
| Optimistic, wrapped | 20/20 | ||||
| PSRL, standalone | n/a | conditional | |||
| PSRL, wrapped | n/a | conditional |
| Qwen-1.5B | Qwen-7B | ||||
|---|---|---|---|---|---|
| Task | Method | Return | Calls | Return | Calls |
| GoToObj | Never query | 0 | 0 | ||
| Always query | 3408 | 3403 | |||
| ASK/uncertainty | 557 | 557 | |||
| Ours, | 139 | 144 | |||
| Ours, | 75 | 82 | |||
| Task (advisor) | Baseline | Return (calls) | vs ours |
|---|---|---|---|
| GoToObj (1.5B) | Ours, | ( ) | n/a |
| random exact | ( ) | ||
| early schedule | ( ) | ||
| GoToObj (7B) | Ours, | ( ) | n/a |
| random exact | ( ) | ||
| early schedule | ( ) |
| Quantity | GoToObj | GoToLocal |
|---|---|---|
| Median residual | ||
| Median | ||
| Median | ||
| Held-out marginal coverage | ||
| Decision-relevant marginal | ||
| Decision-relevant Mondrian |
| Diagnostic | Supported conclusion |
|---|---|
| Formal radius | MC term dominates; controller abstains |
| Faithful price sweep | realized calls decrease monotonically to zero |
| Five-task volume | robust return without per-task tuning; no optimal-volume tracking |
| Leave-one-task-out | competitive mean utility, but loses on low-headroom tasks |
| Certificate sweep | acceptance and return trade-off under corruption |
| Shift pilot | inconclusive because post-shift budget is nearly exhausted |
Appendix figures & tables33 assets
Supplementary material from the paper’s appendix.
Appendix
| Task family | Role | Train/eval split | Horizon | Advisor(s) | Parser | Seeds |
|---|---|---|---|---|---|---|
| MiniGrid/BabyAI | Core | GoToObj / GoToLocal (random layout) | Qwen2.5-1.5B & 7B | constrained action (7 admissible) | 20 | |
| TextWorld/ALFWorld | Core | pick_and_place / look_at_obj (task split) | simulated ( ) | admissible command | 5 | |
| Crafter | Extension | procedural world seeds (train/eval split) | simulated ( ) | skill/action (17 admissible) | 5 |
| Estimator | Query-value error | Posterior log score | Surrogate loss | Return | Calls |
|---|---|---|---|---|---|
| No query | 0 | ||||
| Marginal factorization | 0 | ||||
| Candidate-only value | 12 | ||||
| Response-conditioned value | 12 |
| Fallback and history | Fallback gap | Width sum | Gap ? | Growth slope | Final return |
|---|---|---|---|---|---|
| Optimistic, standalone | yes (20/20) | ||||
| Optimistic, wrapped | yes (20/20) | ||||
| PSRL, standalone | — | conditional | |||
| PSRL, wrapped | — | conditional |
| Task | Method | Return / success | Calls | Tokens | Latency | Cost-adjusted return |
|---|---|---|---|---|---|---|
| BabyAI-GoToObj | Never query | 0 | 0 | 0 | ||
| ASK / uncertainty gate | 3362 | 93/call | 2033s | |||
| VOE/Q | 3362 | 93/call | 2032s | |||
| Ours (surrogate) | 686 | 93/call | 414s | |||
| BabyAI-GoToLocal | Never query | 0 | 0 | 0 | ||
| ASK / uncertainty gate | 3391 | 105/call | 2125s |
| Task | Method | Return | vs never (paired) | Calls | Cost-adj. | Cert. accept |
|---|---|---|---|---|---|---|
| GoToObj | Never query | — | — | |||
| Always query | (sig) | — | ||||
| ASK / uncertainty | ||||||
| Ours, | ||||||
| Ours, | ||||||
| Ours, | — |
| Qwen-1.5B | Qwen-7B | |||||
|---|---|---|---|---|---|---|
| Task | Baseline | Isolates | Return | vs ours | Return | vs ours |
| GoToObj | Ours, | — | — | — | ||
| Random matched | placement | |||||
| Schedule matched | placement | |||||
| Ours, cert-off | certificate | |||||
| Ours, global-pred | predictor | |||||
| Task (advisor) | Baseline | Return (calls) | vs ours |
|---|---|---|---|
| GoToObj (1.5B) | Ours, | ( ) | — |
| random_exact | ( ) | ||
| schedule matched | ( ) | ||
| GoToObj (7B) | Ours, | ( ) | — |
| random_exact | ( ) | ||
| schedule matched | ( ) |
| Task | Method | Return | vs never (paired) | Calls | Cost-adj. | Cert. accept |
|---|---|---|---|---|---|---|
| GoToObj | Never query | — | — | |||
| Always query | (sig) | |||||
| ASK / uncertainty | ||||||
| Ours, | ||||||
| Ours, | ||||||
| Ours, | — |
| Task | v25 | v50 | v75 | v100 | v150 | best fixed | (calls) | never |
| Qwen2.5-1.5B advisor | ||||||||
| GoToObj | v50 | ( ) | ||||||
| GoToLocal | v150 | ( ) | ||||||
| GoToObjDoor | v75 | ( ) | ||||||
| Open | v50 | ( ) | ||||||
| Pickup | v75 | ( ) | ||||||
| Quantity | GoToObj | GoToLocal |
|---|---|---|
| Mean estimator residual (median over seeds) | ||
| Median | ||
| IQR | ||
| Median (MC-dominated) | ||
| Held-out coverage ( ; mean / min over seeds) | ||
| Conditional coverage on decision-relevant states ( ) | mean ( ) | |
| Coverage on stratum | GoToObj | GoToLocal | overall |
|---|---|---|---|
| Marginal radius | |||
| Mondrian per-stratum radius | |||
| (marginal coverage, all opportunities) |
| corruption rate | |||||
| wrong-advice acceptance (cert on; cert-off where queries occur; over seeds) | |||||
| — | |||||
| — | |||||
| — | |||||
| — | |||||
| Task | metric | ||||||
|---|---|---|---|---|---|---|---|
| GoToObj | calls/ep | ||||||
| (never ) | ret ( CI) | ||||||
| util | |||||||
| GoToLocal | calls/ep | ||||||
| (never ) | ret ( CI) | ||||||
| util |
| Task | Method | Return | Calls/ep | Net utility | Pareto efficient? | |
|---|---|---|---|---|---|---|
| BabyAI-GoToObj | ASK / uncertainty | 0.01 | no | |||
| Ours | 0.01 | no | ||||
| ASK / uncertainty | 0.02 | no | ||||
| Ours | 0.02 | no | ||||
| ASK / uncertainty | 0.05 | no | ||||
| Ours | 0.05 | yes |
| Advisor condition | Certificate | Return | Calls | Accept rate | Unsafe accept | Correct reject | Prevented loss |
|---|---|---|---|---|---|---|---|
| Natural (real LLM) | off | 686 | 1.00 | n/l | — | — | |
| Natural (real LLM) | on | 686 | 0.884 | n/l | 0.116 | ||
| 25% corruption (real LLM) | off | 387 | 1.00 | n/l | — | — | |
| 25% corruption (real LLM) | on | 387 | 0.801 | n/l | 0.199 | ||
| Correlated error (simulated) | off | 400 | 1.00 | 0.884 | — | — | |
| Correlated error (simulated) | on | 400 | 0.272 | 0.234 | 0.650 |
| Variant | Query-value ECE | Return | Calls |
|---|---|---|---|
| Rich-BLL VOI (ours) | |||
| Deep ensemble | |||
| Novelty proxy | |||
| Variance (overconfident) | — | ||
| Variance (calibrated) | — | ||
| Variance (underconfident) | — |
| Variant | Marginal cov. | Trajectory cov. | Median | Abstain rate | Surrogate loss | |||
|---|---|---|---|---|---|---|---|---|
| No radius, | 200 | 5 | 20 | 0.518 | 0.000 | 0 | 0.000 | 0.001 |
| Constant conformal radius | 200 | 5 | 20 | 0.900 | 0.255 | 0.057 | 0.131 | 0.005 |
| Scaled conformal radius | 200 | 5 | 20 | 0.886 | 0.160 | 0.000 | 0.115 | 0.005 |
| Bonferroni trajectory radius | 200 | 5 | 20 | 0.997 | 0.960 | 0.138 | 0.241 | 0.016 |
| Predictor | Predictor error | Resolutions | Queries used | Rank |
|---|---|---|---|---|
| Uniform | 12 | 5 | ||
| Global frequency (cached) | 12 | 4 | ||
| Per-context online (state) | 12 | 3 | ||
| Feature-generalizing online | 12 | 2 | ||
| Replay oracle, diagnostic | 12 | 1 |
| Variant | Predictor | Values | Certificate | Return | Calls | Unsafe accept | Allocation loss | |
|---|---|---|---|---|---|---|---|---|
| VOE/Q-style value gate | no | no | no | 0 | 36.8 | 0.200 | 1.91 | |
| Marginal predictor, raw action | yes | no | no | 0 | 32.3 | 0.201 | 2.23 | |
| Response-contingent gate | yes | yes | no | 0 | 32.3 | 0.093 | 2.24 | |
| Response-contingent + certificate | yes | yes | yes | 0 | 32.4 | 0.088 | 2.18 | |
| Full conservative controller | yes | yes | yes | calibrated | 16.9 | 0.056 | 2.98 |
| Cache policy | Pre-shift return | Final return | Recovery episodes | Post-shift calls |
|---|---|---|---|---|
| No cache | ||||
| Time-to-live | ||||
| Epistemic (certificate) |
| 0.0 | 0.25 | 0.5 | 0.75 | 1.0 | |
|---|---|---|---|---|---|
| Queries, measured | 60.0 | 38.6 | 24.2 | 15.9 | 12.0 |
| Strict comparator | 96.0 | 72.0 | 48.0 | 24.0 | 0.0 |
| Method | Return | Calls | Cost-adjusted |
|---|---|---|---|
| Never-query | 0.182 | 0 | 0.182 |
| Fixed-period | 0.186 | 90 | -0.714 |
| Random-gated | -0.48 | 60 | -1.08 |
| Novelty-gated | 0.850 | 90 | -0.050 |
| Ensemble-gated | 0.850 | 65.4 | 0.196 |
| Always-query | -0.48 | 90 | -1.38 |
| Advisor property | Rate |
|---|---|
| Local response-rule adherence | 1.000 |
| Optimal-action accuracy | n/a (no oracle) |
| Obstacle-conflict rate | n/a (not instrumented) |
| Parser failure | 0.000 |
| Certificate acceptance | 0.884 |
| Reliability | Return | Calls |
|---|---|---|
| 0.85 | 51.6 | |
| 0.52 | 61.4 | |
| 0.19 | 64.4 | |
| -0.15 | 77.6 | |
| 0.18 | 87.0 |
| Reliability | Return | Calls | Unsafe accept |
|---|---|---|---|
| 0.850 | 51.6 | 0.000 | |
| 0.850 | 62.8 | 0.046 | |
| 0.186 | 73.0 | 0.150 | |
| 0.514 | 78.2 | 0.163 | |
| 0.182 | 75.8 | 0.275 |
| Estimator / variant | ECE | Calls | Return |
|---|---|---|---|
| Rich-BLL gate | 0.262 | 51.6 | 0.850 |
| Ensemble | 0.698 | 65.4 | 0.850 |
| Novelty | 0.675 | 90.0 | 0.850 |
| Variance , overconfident | — | 20.8 | 0.186 |
| Variance , nominal | — | 51.6 | 0.850 |
| Variance , underconfident | — | 51.6 | 0.850 |
| Method | 0.001 | 0.005 | 0.010 | 0.020 |
|---|---|---|---|---|
| Fixed-period | +0.096 | -0.264 | -0.714 | -1.614 |
| Novelty gate | +0.760 | +0.400 | -0.050 | -0.950 |
| Ensemble gate | +0.785 | +0.523 | +0.196 | -0.458 |
| Oracle response model | +0.798 | +0.592 | +0.334 | -0.182 |
| Safe Rich-BLL gate | +0.798 | +0.592 | +0.334 | -0.182 |
| Quantity | ||
|---|---|---|
| Never-query return | 0.18 | 0.75 |
| Gate return | 0.85 | 0.75 |
| Gate calls | 51.6 | 90.4 |
| Gate cost-adjusted return | 0.33 | -0.15 |
| Always-query cost-adjusted return | -1.38 | -0.45 |
| Return lift over never-query | 0.67 | 0.00 |
| Cache strategy | Pre-shift | Final return | Recovery ep. | Post-shift calls |
|---|---|---|---|---|
| No cache | -0.810 | +0.194 | 92.4 | 1.6 |
| Time-to-live | -0.810 | -0.122 | 108.0 | 1.2 |
| Epistemic invalidation | -0.810 | -0.810 | 150.0 | 1.0 |
| Predictor | Resolutions / budget | Predictor error |
|---|---|---|
| Oracle | 10.2 | 0.00 |
| Feature-generalizing online | 8.8 | 0.20 |
| Per-state online | 5.5 | 0.26 |
| Cached global frequency | 5.5 | 0.39 |
| Uniform | 5.5 | 0.40 |
| Regime | Acquisition | Execution |
|---|---|---|
| query positive lower-bound value | certified action only | |
| no fresh query | fallback or certified cache | |
| Reliable advisor | sparse discovery and refresh | often accepted |
| Correlated wrong advisor | predictor should suppress repeats | rejected if uncertified |
| Execution rule | Return | Calls | Advice acceptance | Wrong-advice acceptance | Prevented loss |
|---|---|---|---|---|---|
| Variance-only cache rule | 37.3 | 1.000 | 1.000 | — | |
| Action-gap certificate | 38.7 | 0.772 | 0.180 | 42% | |
| Certificate without conservative query LCB | 32.5 | 0.752 | 0.041 | 48% | |
| Full controller | 20.4 | 0.740 | 0.255 | 46% |