REVIEW 4 major objections 5 minor 24 references
Hyperparameter brittleness in offline goal-conditioned RL is largely a consequence of bootstrapped value objectives, not an unavoidable property of RL.
Reviewed by Pith at T0; open to challenge. T0 means a machine referee read the full paper against a public rubric. the ladder, T0–T4 →
T0 review · deepseek-v4-flash
2026-08-03 04:12 UTC pith:M4GQN4NW
load-bearing objection A careful, honestly hedged empirical study of hyperparameter landscape geometry in offline GCRL; worth refereeing once the arXiv abstract is corrected and the phase-boundary artifact is addressed. the 4 major comments →
Beyond Success Rates: Trainability and Extractability for Offline GCRL
The pith
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
Core claim
In offline goal-conditioned RL with fixed datasets and controlled data quality, the choice of value-learning objective changes not just peak success but the entire geometry and transferability of the hyperparameter performance landscape. QRL, which learns a quasimetric distance-to-goal without bootstrapping, keeps a large fraction of configurations near-optimal and keeps its important hyperparameters stable across phases once about 20% expert data is present. HIQL, which learns a value function via bootstrapped TD expectile regression, shows tighter optima, stronger interactions between learning rate and discount factor, and larger phase-to-phase drift, especially under scheduled improvement
What carries the argument
The central instrument is the phased hyperparameter-landscape analysis paired with an inter-goal gradient-alignment diagnostic. Landscapes are built by training a fixed set of hyperparameter configurations from shared checkpoints, evaluating at phase boundaries, and summarizing geometry with ε-optimality mass (the fraction of configurations within, say, 90% of the best), phase-to-phase drift (mean normalized performance change), and early-selection regret (loss from committing to a configuration chosen in an early phase). The mechanistic diagnostic computes, for a single minibatch and multiple goal relabelings, the cosine similarity between critic-loss gradients; negative values indicate des
Load-bearing premise
The phase boundaries used to define training stages are derived from when a single hand-tuned default configuration first reaches 95% of its final success rate, and since QRL and HIQL converge at very different speeds, the phases may compare the two algorithms at different effective training progress — so the reported drift differences could be partly an artifact of boundary placement.
What would settle it
On a fixed offline dataset, take a quasimetric objective and add a bootstrapped target term to its critic loss: if the inter-goal gradient cosine-similarity distribution gains a heavier negative tail and the hyperparameter landscape becomes sharper and more phase-sensitive (lower ε-optimality mass, higher phase-to-phase drift), the paper's causal story is supported; if those metrics stay unchanged, the attribution of brittleness to bootstrapping is falsified.
If this is right
- Offline goal-conditioned RL hyperparameter landscapes are generally more benign than online RL landscapes: even with degraded data, large fractions of configurations stay near-optimal, and most landscape reorganization happens early in training.
- With at least modest expert data, non-bootstrapped quasimetric objectives can make narrow, phase-specific hyperparameter schedules unnecessary, since near-optimal regions stay broad and stable.
- Bootstrapped TD methods require more careful and stage-dependent tuning, and early good configurations can become suboptimal under scheduled data-quality shifts.
- Inter-goal gradient-alignment measurements offer a low-cost proxy for predicting which objectives or configurations will be brittle: a heavier negative tail in critic gradient cosine similarity co-occurs with lower performance and sharper optima.
- Objective design could target reducing cross-goal gradient conflicts while retaining bootstrapping's sample-efficiency benefits.
Where Pith is reading between the lines
- If the gradient-interference story generalizes, any relabeling-based TD learner (including hindsight experience replay in online settings) should show the same phase-dependent brittleness; measuring cosine similarity between gradient updates from different relabelings in those settings is a direct test.
- The comparison is observational, but it suggests a verifiable causal claim: adding a bootstrapped target term to QRL's critic loss should shift its gradient-alignment distribution toward a heavier negative tail and sharpen its landscape, while removing the bootstrap term from HIQL should do the reverse.
- The phase-boundary calibration could be checked by recomputing drift and ε-optimality mass with boundaries aligned at equal training steps or equal performance progress; if the HIQL-versus-QRL gap shrinks, part of the reported effect is an artifact of the protocol.
- The gradient-alignment diagnostic could be turned into an online monitor: track the negative-tail mass during training and trigger a learning-rate adjustment when it grows, effectively replacing hand-tuned phase schedules with a signal-driven schedule.
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The full text of the manuscript (title: "When Are RL Hyperparameters Benign? A Study in Offline Goal-Conditioned RL") studies whether hyperparameter sensitivity in offline goal-conditioned RL is intrinsic to the problem or amplified by the training objective. It compares the bootstrapped TD method HIQL with the non-bootstrapped quasimetric method QRL under controlled stationary and scheduled data-quality regimes. Using phase-resolved hyperparameter landscapes, fANOVA importance profiles, and an inter-goal gradient-alignment diagnostic, it reports that (i) offline GCRL landscapes are generally more benign than online RL landscapes, (ii) once modest expert data is present, QRL exhibits broad and stable near-optimal regions while HIQL shows sharper optima and larger phase-to-phase drift, and (iii) HIQL's critic gradients show a heavier negative tail of inter-goal cosine similarity, which co-occurs with the observed sensitivity. The paper frames the gradient result as a descriptive diagnostic rather than a proof of causality.
Significance. If the reported findings hold, they would be a useful contribution to AutoRL and offline GCRL: they suggest that the choice of learning objective, not just the data distribution or exploration, can shape the geometry of hyperparameter response surfaces and that non-bootstrapped objectives may be substantially easier to tune. The study is computationally extensive (128 configurations, 5 seeds per phase, multiple AntMaze variants), defines quantitative landscape metrics (ε-optimality mass, drift, early-selection regret), and includes explicit limitations. The gradient-interference diagnostic is an interesting mechanistic hypothesis that is clearly distinguished from an optimality criterion. However, the paper's central cross-algorithm comparison is built on only two algorithms that differ in many dimensions beyond bootstrapping, and the phase-alignment protocol introduces a potential confound (Appendix D.1, Table 10). The manuscript also contains a severe internal inconsistency: the abstract supplied at the top describes a different paper (four methods, AWR temperature, Cube/Scene) from the full text (two methods, learning rate/discount factor, AntMaze variants). As it stands, the su
major comments (4)
- [Abstract vs. Full Text] The abstract states that the paper studies four methods (GCIQL, GCIVL, QRL, CRL) under a shared AWR extractor, with landscapes over learning rate and AWR temperature, evaluated on AntMaze, Cube, and Scene. The full text studies two methods (HIQL, QRL) over learning rate and discount factor, on AntMaze variants and related mazes, with no AWR temperature or Cube/Scene experiments. These are irreconcilably different studies. The reader cannot determine which claims are actually being made. This must be resolved before any further review.
- [Appendix D.1 / Table 10] Phase boundaries are defined from the last time a single hand-tuned default configuration crosses 95% of its final success rate. For antmaze-medium-v0 at 0% explore, this occurs at 18,461 steps for QRL and 99,734 steps for HIQL, a >5x difference. The four phases therefore cover very different absolute training windows for the two algorithms. The paper acknowledges this in D.1 but dismisses it as 'not problematic' because the goal is only to find interesting time steps. That dismissal is not valid for cross-algorithm comparisons of drift, near-optimal mass, and importance stability: if QRL's default is relatively well-tuned or its 95% bar is reached quickly, QRL's landscapes are sampled at systematically earlier absolute steps. The reported differences may be artifacts of the phase protocol rather than properties of the objectives. The authors should provide a sensitivity analysis with al
- [Tables 2–3 / Section 4.2] The headline quantitative differences are not statistically robust. For example, scheduled HIQL ρ0.9 = 0.12±0.10 vs. QRL 0.35±0.25 overlap within one standard deviation; across-phase change for HIQL 0.22±0.16 vs. QRL 0.17±0.11 also overlap. Moreover, HIQL and QRL differ in objective, architecture, regularization, and update rules, so the specific attribution to bootstrapping is not supported by the design. The limitations section correctly notes this, but the abstract and conclusion present the contrast as a finding. A concrete test would be a bootstrapped vs. non-bootstrapped variant of the same algorithm family, or an explicit statement that the paper only reports a two-point comparison.
- [Appendix E / Section 4.1] fANOVA importances are computed from SMAC/Hypersweeper optimization traces, not from a uniform design (Appendix E). This makes the importance vectors design-dependent: SMAC's proposal distribution changes over time and differs by algorithm. The phase-to-phase cosine distances in Table 1 and the perplexity/stability plots in Figure 2 could therefore reflect differences in the optimization trajectory rather than intrinsic shifts in which hyperparameters matter. The authors should either recompute importances on the fixed Sobol configuration set or justify why the non-uniform design does not affect the cross-algorithm comparisons.
minor comments (5)
- [Throughout] The full text contains multiple typos and inconsistencies in references/citations: 'Howeer' (Appendix A), 'Adavantage', 'quaismetric', 'explciitly', 'ICL' truncated citations, and incomplete venue entries. A careful proofread is needed.
- [Table 4] Table 4 reports phase-to-phase change aggregated over both algorithms, despite the text discussing algorithm-specific differences. Please split by algorithm or clarify that the table is a pooled summary.
- [Section 3 / Eq. (7)–(8)] The gradient diagnostic κ(g,g') uses gradients with respect to the critic trunk. It would help to state explicitly how 'critic trunk' is defined for HIQL and QRL, and whether the comparison is on the same parameter dimensionality. The Pearson correlation of 0.43 in Section 4.3 should also report sample size and confidence interval.
- [Figure 1 / Caption] The caption says 'top-10%' near-optimal region, while the text and Eq. (4) define ε-optimality mass with ε thresholds. Please use consistent terminology and indicate which ε is shown.
- [Appendix F.1] The definition of 'last intersection with the performance threshold' should specify interpolation details and how ties are handled, since phase boundary placement is load-bearing for the conclusions.
Circularity Check
No significant circularity; the empirical comparison and diagnostics are measured independently of the conclusions.
full rationale
The paper is an empirical landscape study, not a derivation, and its central comparisons do not reduce to their inputs by construction. Phase boundaries (Appendix D.1) are set from a single default configuration's 95% convergence point; the paper explicitly warns that 'this approach may yield phases that vary widely across algorithms' and that results 'should therefore not be used to compare convergence speed across algorithms or datasets.' That is a real protocol limitation for cross-algorithm comparability, but the landscape metrics (Eqs. 4-6) are not algebraically determined by the phase-boundary choice: rho_epsilon, Delta, and regret are measured from actual configuration evaluations in each phase. The gradient-interference diagnostic (Eqs. 7-8) is computed directly from critic gradients under each algorithm's own loss; it is not fitted to reproduce the landscape pattern, and the authors explicitly call it 'a descriptive mechanism consistent with the observed patterns rather than a definitive explanation' and state that 'cross-algorithm comparisons alone do not establish causality.' The heavy citation of Mohan et al. (2023) supplies the phased-pipeline methodology and IGPR visualization, not the paper's load-bearing claim, and the algorithms, datasets, and HPO tools (OGBench, SMAC, DeepCAVE) are external. No equation in the paper is equivalent by construction to an input, and no fitted parameter is renamed as a prediction. The D.1 phase-calibration limitation and the Section 4.3 causal-identification caveat are correctly acknowledged; they lower confidence in the strength of the HIQL-vs-QRL comparison but are not circularity. Verdict: no significant circularity.
Axiom & Free-Parameter Ledger
axioms (5)
- domain assumption Offline datasets with goal relabeling provide a standardized learning signal that allows fair comparison of different objectives on identical task structure (Section 1, Preliminaries).
- ad hoc to paper Phase boundaries defined by last crossing of 95% of final success rate of a hand-tuned default configuration align 'crucial points' across algorithms (Appendix D.1).
- domain assumption Inter-goal gradient cosine similarity on critic parameters is a valid diagnostic of destructive interference for both objectives (Section 3, Eq. 7-8).
- domain assumption Hyperparameter landscapes in offline GCRL are representative of RL tuning difficulty generally (title, abstract, Section 5).
- standard math fANOVA variance decomposition and Sobol sampling assumptions (Hutter et al. 2014; Sobol 1967) hold for the evaluated configuration sets.
read the original abstract
Offline goal-conditioned reinforcement learning (GCRL) is typically benchmarked by the best tuned success rate of each method. This score measures attainable performance, but it does not reveal how reliably a learned goal-conditioned signal can be extracted into a policy: a method could succeed across many value-learning and extraction settings, or only at a narrow, hard-to-find configuration. We study this gap across four methods, GCIQL, GCIVL, QRL, and CRL, under a shared advantage-weighted regression (AWR) extractor. For each method, we construct trainability landscapes over the optimizer learning rate, which affects value learning and actor optimization, and AWR temperature, which controls how selectively the actor imitates high-advantage transitions. Across AntMaze, Cube, and Scene, we observe distinct regimes: high-scoring methods may be broadly accessible or brittle, while broad relative basins may still sit below low absolute ceilings. To interpret these differences, we pair landscapes with post-hoc diagnostics of future-vs-random goal discrimination and AWR weight concentration. Their relationship to downstream success is task-dependent. On AntMaze, where future goals align with path-like progress, these diagnostics explain landscape regimes. On Cube and Scene, goal ranking and manipulation control decouple: methods can rank goals well while failing downstream, or succeed through action-conditioned advantages despite weak future-vs-random separation. These results show that peak tuned success alone does not establish broadly extractable goal-conditioned behavior. Trainability landscapes expose this gap, while extraction diagnostics offer a lower-cost lens on how learned signals become policies.
Figures
Reference graph
Works this paper leans on
-
[7]
Kumar, A
A. Kumar, A. Zhou, G. Tucker, and S. Levine. Conser- vative q-learning for offline reinforcement learning. In Larochelle et al. (2020). H. Larochelle, M. Ranzato, R. Hadsell, M.-F. Balcan, and H. Lin, editors.Proceedings of the 34th International Conference on Advances in Neural Information Process- ing Systems (NeurIPS’20),
2020
-
[9]
URL https://arxiv.org/abs/2005.01643. M. Lindauer, K. Eggensperger, M. Feurer, A. Biedenkapp, D. Deng, C. Benjamins, T. Ruhkopf, R. Sass, and F. Hut- ter. SMAC3: A versatile bayesian optimization package for Hyperparameter Optimization.Journal of Machine Learning Research, 23(54):1–9,
Pith/arXiv arXiv 2005
-
[10]
Y . Mao, H. Zhang, C. Chen, Y . Xu, and X. Ji. Supported value regularization for offline reinforcement learning. In Oh et al. (2023). A. Mohan, C. Benjamins, K. Wienecke, A. Dockhorn, and M. Lindauer. Autorl hyperparameter landscapes. In A. Faust, C. White, F. Hutter, R. Garnett, and J. Gardner, editors,Proceedings of the Second International Confer- enc...
2023
-
[11]
V . Myers, C. Ji, and B. Eysenbach. Horizon generalization in reinforcement learning. InThe Thirteenth International Conference on Learning Representations (ICLR’25)ICL (2025). Published online:iclr.cc. V . Myers, B. Chunyuan Zheng, B. Eysenbach, and S. Levine. Offline goal-conditioned reinforcement learning with quasimetric representations. InProceedings...
Pith/arXiv arXiv 2025
-
[14]
R. Sass, E. Bergman, A. Biedenkapp, F. Hutter, and M. Lin- dauer. Deepcave: An interactive analysis tool for auto- mated machine learning. In M. Mutny, I. Bogunovic, W. Neiswanger, S. Ermon, Y . Yue, and A. Krause, ed- itors,ICML Adaptive Experimental Design and Active Learning in the Real World (ReALML Workshop 2022),
2022
- [17]
-
[18]
15 B.2 Hierarchical Implicit Q-Learning (HIQL)
12 When Are RL Hyperparameters Benign? Appendix Table of Contents A Related Work 13 B Algorithmic Details 15 B.1 Self-Supervised Goal Relabeling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 B.2 Hierarchical Implicit Q-Learning (HIQL) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 B.3 Quasimetric RL...
2018
-
[19]
This differs from weight-space loss landscape analyses in deep networks, which study geometric properties of the training objective in parameter space
for studying structure in thehyperparameter response surface(configuration → performance), including robustness, modality, and the geometry of near-optimal regions (Pitzer and Affenzeller, 2012; Malan, 2021). This differs from weight-space loss landscape analyses in deep networks, which study geometric properties of the training objective in parameter spa...
2012
-
[21]
A recent line of work in this domain focuses explciitly on non-TD objectives (Wang et al., 2023; Myers et al., 2025a;b; Zheng et al.,
that interpret parts of goal-reaching as near-supervised representation/behavior learning. A recent line of work in this domain focuses explciitly on non-TD objectives (Wang et al., 2023; Myers et al., 2025a;b; Zheng et al.,
2023
-
[22]
that utilize the (quaismetric) structure of goal distances (Mohan et al., 2024). This structure is central to our study: it lets us vary data quality systematically while holding interaction budgets fixed, and it exposes how bootstrapping-based objectives (e.g., IQL/HIQL-style backups) can change the optimization problem even when exploration is not a con...
2024
-
[24]
All configurations within a phase are evaluated from the same reference checkpoint to ensure comparability
Inputs to fANOV A.For eachphase t,algorithm(QRL, HIQL), anddataset regime(constant mixture or scheduled data quality), we collect a set of evaluated configurations Ct ={(λ (i), ft(λ(i)))}nt i=1, where λ(i) is a hyperparameter configuration and ft(λ(i)) is the corresponding phase-indexed evaluation score produced by our phased protocol (Section 3). All con...
2023
-
[512]
For details, refer to OGBench (Park et al., 2025a). D. Phased Training To gather data during training, we apply the phased pipeline proposed by Mohan et al. (2023), as shown in Figure 4, to offline GCRL. The resulting data will allow us to study the hyperparameter landscapes throughout the training process. First, we start training a set of configurations...
2023
-
[1996]
T. Wang, A. Torralba, P. Isola, and A. Zhang. Optimal goal- reaching reinforcement learning via quasimetric learning. In Krause et al. (2023). R. Yang, Y . Lu, W. Li, H. Sun, M. Fang, Y . Du, X. Li, L. Han, and C. Zhang. Rethinking goal-conditioned supervised learning and its connection to offline rl. InThe Tenth International Conference on Learning Repre...
2023
-
[2002]
Fujimoto and S
S. Fujimoto and S. Gu. A minimalist approach to offline reinforcement learning. In Ranzato et al. (2021). S. Fujimoto, D. Meger, and D. Precup. Off-policy deep rein- forcement learning without exploration. In K. Chaudhuri and R. Salakhutdinov, editors,Proceedings of the 36th In- ternational Conference on Machine Learning (ICML’19), volume
2021
-
[2008]
Kostrikov, A
I. Kostrikov, A. Nair, and S. Levine. Offline reinforce- ment learning with implicit q-learning. InThe Tenth International Conference on Learning Representations (ICLR’22)ICL (2022). Published online:iclr.cc. A. Krause, E. Brunskill, K. Cho, B. Engelhardt, S. Sabato, and J. Scarlett, editors.Proceedings of the 40th Interna- tional Conference on Machine Le...
2022
-
[2014]
near-optimal
via DeepCA VE (Segel et al., 2025). This yields marginal importance scores for individual hyperparameters as well as interaction mass capturing higher-order effects. To quantify changes in importance profiles across phases, we computed cosine distance between phase-wise importance vectors. F.5. Reproducibility details All experiments are conducted with fi...
2025
-
[2015]
and hindsight relabeling (Andrychowicz et al., 2017), and connects to goal-conditioned supervised learning perspectives (Yang et al.,
2017
-
[2018]
Tarasov, A
D. Tarasov, A. Nikulin, D. Akimov, V . Kurenkov, and S. Kolesnikov. Corl: Research-oriented deep offline rein- forcement learning library. In Oh et al. (2023). J. Tsitsiklis and B. Van Roy. Analysis of temporal- diffference learning with function approximation
2023
-
[2019]
Ghosh, C
D. Ghosh, C. Bhateja, and S. Levine. Reinforcement learn- ing from passive data via latent intentions. In Krause et al. (2023). P. Henderson, R. Islam, P. Bachman, J. Pineau, D. Precup, and D. Meger. Deep reinforcement learning that matters. In S. McIlraith and K. Weinberger, editors,Proceedings of the Thirty-Second Conference on Artificial Intelligence (...
2023
-
[2020]
Agarwal, M
R. Agarwal, M. Schwarzer, P. Samuel Castro, A. C. Courville, and M. G. Bellemare. Deep reinforcement learning at the edge of the statistical precipice. In Ran- zato et al. (2021). M. Andrychowicz, F. Wolski, A. Ray, J. Schneider, R. Fong, P. Welinder, B. McGrew, J. Tobin, P. Abbeel, and W. Zaremba. Hindsight experience replay. InProceed- ings of the 32nd ...
2021
-
[2021]
Eimer, M
T. Eimer, M. Lindauer, and R. Raileanu. Hyperparameters in reinforcement learning and how to tune them. In Krause et al. (2023). L. Engstrom, A. Ilyas, S. Santurkar, D. Tsipras, F. Janoos, L. Rudolph, and A. Madry. Implementation matters in deep RL: A case study on PPO and TRPO. InThe Eigth International Conference on Learning Representations (ICLR’20). ICLR,
2023
-
[2022]
X. Peng, A. Kumar, G. Zhang, and S. Levine. Advantage- weighted regression: Simple and scalable off-policy re- inforcement learning.arXiv preprint arXiv:1910.00177,
Pith/arXiv arXiv 1910
-
[2023]
Curran Asso- ciates. S. Park, D. Ghosh, B. Eysenbach, and S. Levine. Hiql: Offline goal-conditioned rl with latent states as actions. In Oh et al. (2023). S. Park, K. Frans, B. Eysenbach, and S. Levine. Og- bench: Benchmarking offline goal-conditioned rl. In The Thirteenth International Conference on Learning Representations (ICLR’25)ICL (2025). Published...
2023
-
[2025]
ICLR. Published on- line:iclr.cc. M. Jaderberg, V . Dalibard, S. Osindero, W. Czarnecki, J. Donahue, A. Razavi, O. Vinyals, T. Green, I. Dunning, K. Simonyan, C. Fernando, and K. Kavukcuoglu. Popula- tion based training of neural networks.arXiv:1711.09846 [cs.LG],
discussion (0)
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