REVIEW 4 major objections 6 minor 1 cited by
Large Reasoning Models are not thinking straight: on the unreliability of thinking trajectories
T0 review · 4 major / 6 minor · reviewed 2026-08-06 · deepseek-v4-flash
Pith's one-line read Large reasoning models often disregard correct solutions injected directly into their own chain of thought, and continue reasoning to a wrong answer.
desk verdict A genuinely intriguing observation about reasoning models ignoring injected correct answers, but the protocol doesn't yet prove it; deserves a careful referee. read the letter →
The pith
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
The reading
What carries the argument
The load-bearing mechanism is the injection prompt $P_t = R[:t] \oplus V \oplus Y$: take the model's own trace up to the $t$-th thought, concatenate a naturalistic transition phrase $V$, then concatenate the ground-truth solution $Y$. A thought-separator heuristic based on keywords such as "Alternatively" and "Wait" splits the trace into thoughts, defines the injection points, and lets the authors count "overthinking tokens" generated after the injection. This construction turns a static benchmark problem into a counterfactual experiment: if the model genuinely reasons from its premises, it should recognise $Y$ as a valid resolution and stop; if it instead continues and errs, the trace is shown to be decoupled from correctness. The same setup supplies the paper's quantitative measures, including the completion ratio and the number of overthinking tokens produced before a correct or incorrect answer.
What would settle it
On a problem where the model rejects the injected ground truth, rewrite the solution using the model's own baseline phrasing, token choices, and punctuation, then re-inject it; if the model accepts the rewritten solution but not the original, the reported failure is an artifact of the injection format rather than a general inability to integrate correct information.
Extended reading notes
Core claim
The central claim is that large reasoning models frequently fail to accept an explicitly provided correct solution even when it is placed inside their own ongoing reasoning trace. The authors construct prompts $P_t = R[:t] \oplus V \oplus Y$, where $R[:t]$ is the model's own generated reasoning up to thought $t$, $Y$ is the ground-truth solution (reasoning plus final answer), and $V$ is a short prefix ("$\langle$think$\rangle$ Okay, so" at $t=0$, "Alternatively," otherwise) meant to make $Y$ look like the model's own continuation. Rather than adopting $Y$, the models typically produce hundreds or thousands of additional overthinking tokens, question the injected solution, and often commit to an incorrect final answer. This behavior appears across all three tested models (LLaMA 70B, Qwen 7B, DeepScalR 1.5B) and across AIME2024 problems, although the amount of overthinking is strongly problem-dependent. In the rare positive cases, the model accepted the solution only after many thoughts, sometimes explicitly out of resignation or time pressure rather than recognition of correctness.
Load-bearing premise
The load-bearing premise is that inserting the ground-truth solution with the prefix V makes it read to the model as one of its own prior thoughts, so ignoring it counts as a failure to integrate a correct answer rather than a reaction to foreign text.
Editorial extensions
If this is right
- Chain-of-thought traces cannot be taken at face value as the model's reasoning: a model can write a long, plausible-looking trace while ignoring a correct solution it was just given.
- External correction or human feedback injected at test time is unlikely to steer current reasoning models reliably, since they often reject the correct information rather than integrate it.
- Benchmark gains from spending more inference compute may partly reflect spending more tokens on the same fragile heuristics rather than better understanding.
- Evaluation metrics based on completion length or number of thoughts will mislead, because the same models show both overthinking and underthinking depending on the problem.
- New training or prompting techniques are needed to make reasoning models receptive to corrective signals, which the paper identifies as the main direction for future work.
Reading between the lines
- A direct test of the paper's interpretation would be to rewrite the injected ground-truth solution in the model's own discovered phrasing, tokens, and punctuation from its baseline trace; if the model then accepts the solution, the original rejection was an artifact of the injection format rather than an inability to use correct information.
- The same disregard for externally provided correct information may extend beyond mathematics to code repair, document analysis, or any task where a correct answer is present in context while the model persists with its initial plan; the paper only tests AIME2024.
- The behavior is consistent with reward hacking during reinforcement learning: if long traces and correct final answers are correlated in the training signal, the model may learn to keep generating tokens regardless of content, but that causal story is not established by this study.
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The paper reports an empirical study of three reasoning models (Llama-70B, Qwen-7b, DeepScalR-1.5B) on the AIME2024 benchmark. The authors generate baseline chains of thought, segment them into 'thoughts' using a keyword heuristic, and inject the official ground-truth solution Y into the trajectory at position t via P_t = R[:t] ⊕ V ⊕ Y, with V chosen to mimic the model's writing style. They observe that the models often continue generating tokens after the injection, sometimes discarding the injected correct solution and ending on a wrong answer. They interpret this as evidence that large reasoning models lack robust mechanisms to integrate corrective signals, thereby questioning the reliability of chain-of-thought as a transparent indicator of reasoning. The paper is explicitly preliminary and ends with a limitations section.
Significance. If the effect is robust, this is a meaningful contribution to the overthinking and underthinking literature: it would challenge the view that CoT tokens are causally relevant for correctness and would have implications for human-in-the-loop correction and reward modeling. The experimental setup is simple and reproducible in principle, and it uses an external benchmark with known ground-truth answers. However, the current evidence is largely anecdotal and qualitative: there are no control conditions, no precise metric definition, no confidence intervals, and no per-model aggregate success rates after injection. The significance is therefore conditional on validation of the injection protocol, which is the load-bearing assumption of the paper.
major comments (4)
- [§3.2, Eq. (1)] The load-bearing assumption is that V = '<think> Okay, so ' or 'Alternatively, ' makes the appended official solution Y appear as the model's own prior thought. The paper provides no evidence for this. Official AIME solutions are human-written and can lie outside the model's RL-shaped continuation distribution, and the prefix 'Alternatively, ' may in fact signal a candidate that is later rejected, since such candidates are often abandoned in these models' trajectories. The observed disregard could therefore be a reaction to foreign or negatively cued text rather than an inability to integrate correct information. Please (i) report the model's log-probability of Y under its continuation distribution, (ii) include control injections of neutral filler text and of a plausible but incorrect solution, (iii) ablate the prefix V, and (iv) ask the model to explicitly verify Y. Without these, Eq. (1) does not establish the central claim.
- [§3.1, Figures 1–3] The central quantitative claim that models 'often' disregard correct solutions is not backed by aggregate statistics. The term 'overthinking tokens' is never defined precisely, and the figures provide no error bars, no number of runs or seeds, no sampling temperature, and no per-model accuracy numbers after injection. Please define the metric, report how many of the 30 AIME2024 problems led to final incorrect answers after injection for each model and each injection position t, and include confidence intervals or a statistical test to support the word 'often.'
- [§3.2, no control condition] There is no baseline in which the model is allowed to continue from R[:t] without any injection, and no comparison with injecting a non-solution text. Such controls are necessary to distinguish 'the model rejects correct information' from 'the model ignores any appended text,' which would be a weaker and less surprising claim. A minimal control set would compare final accuracy and token counts after injection of Y, after injection of a random wrong answer, and after no injection.
- [Limitations] The limitations paragraph concedes that the injection heuristic 'might not fully align with the models' internal reasoning dynamics.' This heuristic is exactly the premise on which the paper's main conclusion rests, so the concession should be treated as a validation requirement rather than a peripheral caveat. The manuscript should report experiments that directly test this alignment, such as the probability checks and control injections listed above.
minor comments (6)
- [§1] The phrase 'are not apart from this issue' should be 'are not exempt from this issue.'
- [Figure 1 caption] The caption refers to 'all four models,' but the paper states that three models were tested; please reconcile this mismatch.
- [§3.2, Figure 2] Please define 'completion ratio' and clarify the coloring scheme in the caption; the current description is difficult to parse.
- [Figure 2 caption] The typo 'wether' should be corrected to 'whether.'
- [References] The references list contains Ma et al. 2025a and Ma et al. 2025b, which appear to be the same preprint; please merge or distinguish them.
- [§3.2, quoted trace] The quoted statement 'But perhaps given the time I have...' is not accompanied by the full generated trace; please include trace excerpts in an appendix for verification.
Circularity Check
No significant circularity; the central claim is an externally benchmarked empirical observation, with protocol-fairness concerns that are validity issues, not circular reductions.
full rationale
The paper contains no derivation that reduces a predicted quantity to a fitted input. Its core evidence is a controlled prompting experiment: Eq. (1) defines Pt = R[:t] ⊕ V ⊕ Y, and the model's continuation is compared against the known AIME 2024 answer, an external benchmark. The reader's circularity score of 0 is correct. The only load-bearing assumption is that the V prefix makes Y appear as the model's own thought; Section 3.2 asserts this ('as if it was generated by the model itself') rather than proving it, and the Limitations section concedes that the injection 'might not fully align with the models' internal reasoning dynamics.' That is a threat to construct or external validity—the experiment may probe reactions to out-of-distribution text rather than an inability to integrate corrections—but it is not circularity: the observed disregard is not equivalent to the prompt by definition, and no fitted parameter is relabeled as a prediction. The paper also does not rely on a load-bearing self-citation chain; references to related work (Wang et al. 2025; Chen et al. 2025) motivate but do not constitute the result. Hence score 0.
Assumptions & free parameters
assumptions (4)
- domain assumption AIME2024 ground-truth solutions are correct and constitute valid corrective information.
- ad hoc to paper The keyword-based heuristic using 'Alternatively' and 'Wait' accurately segments reasoning into meaningful thought units.
- ad hoc to paper The prefix V ('<think> Okay, so ' or 'Alternatively, ') makes the injected solution appear as the model's own generated thought.
- domain assumption The three tested models are representative of large reasoning models across training paradigms.
Cite this review
Pith. "Pith review of Large Reasoning Models are not thinking straight: on the unreliability of thinking trajectories." pith.science (2026). https://pith.science/paper/PQJ73JLM
@misc{pith2026250700711,
author = {Pith},
title = {Pith review of: Large Reasoning Models are not thinking straight: on the unreliability of thinking trajectories},
year = {2026},
howpublished = {\url{https://pith.science/paper/PQJ73JLM}},
note = {Machine review of arXiv:2507.00711}
}
read the original abstract
Large Language Models (LLMs) trained via Reinforcement Learning (RL) have recently achieved impressive results on reasoning benchmarks. Yet, growing evidence shows that these models often generate longer but ineffective chains of thought (CoTs), calling into question whether benchmark gains reflect real reasoning improvements. We present new evidence of overthinking, where models disregard correct solutions even when explicitly provided, instead continuing to generate unnecessary reasoning steps that often lead to incorrect conclusions. Experiments on three state-of-the-art models using the AIME2024 math benchmark reveal critical limitations in these models ability to integrate corrective information, posing new challenges for achieving robust and interpretable reasoning.
Figures
Forward citations
Cited by 1 Pith paper
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Cognitive Demand Steering for Adaptive Meta-Reasoning in Large Language Models
A training-free meta-reasoning loop that tracks remaining cognitive demand and steers an LLM's next action improves average accuracy by about 9 percent over chain-of-thought across three models and six benchmarks.
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[40]
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Reviewed August 6, 2026 · model on record in the stance chip above.
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