3.1. Framework Overview
The goal of this framework is to provide a comprehensive characterization of LLM reasoning quality that supports deployment decisions in high-stakes domains. Achieving this goal is inherently a multi-dimensional problem: decades of cognitive science research establish that reasoning quality cannot be reduced to a single property such as correctness, because a reliable reasoner must simultaneously produce accurate conclusions, maintain coherent inferential chains, remain stable under equivalent reformulations, and allocate computational resources efficiently [
2,
3,
4,
5]. Collapsing these properties into a single score, therefore, discards information that is critical for deployment decisions.
The choice of six dimensions follows directly from this theoretical account. Correctness (CQ) captures epistemic accuracy [
33,
34]; Consistency (CS) operationalizes rational invariance [
3,
12]; Robustness (RS) addresses stability under perturbation [
13,
14]; Local Logical Coherence (LS) reflects constraint-satisfaction in inferential chains [
4,
11]; Efficiency (ES) embodies bounded rationality [
2,
5]; and Stability (SS) captures behavioral reliability across stochastic runs [
24]. Together, these six properties constitute a theoretically motivated core set rather than an exhaustive taxonomy of reasoning quality. Other dimensions, such as calibration, uncertainty awareness, causal faithfulness, and self-correction, are plausible extensions, and we make no claim of completeness. The six dimensions are conceptually distinct by design, each motivated independently by the cognitive-science account above; whether they are also
empirically independent is a separate question we test rather than assume. The discriminant validity analysis in
Section 4.5 finds that they are not uniformly independent: 6 of 15 dimension pairs show acceptable discriminant separation (
), while the remaining pairs cluster into an outcome-level group (CQ, CS, RS, and ES) that is strongly intercorrelated once computed from a shared canonicalized answer representation.
This two-layer organization is examined empirically in
Section 4.
Observation derived from the evaluated models and datasets, not an assumption built into the framework’s design; Local Logical Coherence (LS) is the dimension that empirically remains most clearly orthogonal to the rest.
Reasoning quality is, thus, modeled as follows:
We refer to this six-dimensional behavioral model as RQEval (Reasoning Quality Evaluation) throughout the remainder of the paper.
3.2. Metric Definitions
We next translate each of these theoretically motivated dimensions into an operational metric.
Table 2 defines all symbols used in the metric formulas below.
and
were chosen as a practical compromise between estimation reliability and computational cost: each additional repeated generation multiplies API cost and wall-clock time across seven models, four datasets, and 975 items, and
is the minimum value that permits pairwise agreement to be computed as a non-degenerate statistic (a single pair at
provides only a binary match/mismatch signal, with no way to distinguish a model that is occasionally inconsistent from one that is consistently inconsistent). We view
as sufficient to detect substantial behavioral instability of the magnitude observed in this study (
Section 4), but not as a precision instrument for fine-grained consistency estimation; larger
K would reduce sampling variance in the CS and SS estimates and is a direct avenue for future work under a larger compute budget.
Correctness (CQ) measures final-answer accuracy: the epistemic goal of reasoning as the production of conclusions that accurately correspond to the underlying problem structure [
33,
34]. Because LLM outputs are often verbose (
“John has 8 apples.” rather than
“8”),
is extracted from the raw generation using a type-aware canonicalization procedure. The matching rule is selected from the gold-answer type before comparison. For numeric answers, the pipeline uses the value following a
#### delimiter when present (GSM8K’s standard final-answer marker [
30]) and otherwise extracts the final number in the generation; values are compared within a tolerance of
. Binary answers require an unambiguous
yes/
no lexical signal. Multiple-choice answers require a structurally anchored option letter A–D, such as a letter following
“answer is” or
“correct option is”, rather than an arbitrary occurrence of that letter. Other free-text answers use normalized string equality or containment after lowercasing, trailing-punctuation removal, and whitespace collapse. Restricting containment to free-text answers prevents short numeric and categorical labels from matching incidentally inside unrelated tokens. If no applicable canonical answer can be extracted, the response is scored as incorrect. The same canonicalization procedure is used for CQ, CS, and RS. The full implementation is available in the released code (
Section 3.4).
Consistency (CS) evaluates output stability across
independent responses per instance at temperature
:
Robustness (RS) measures performance under
semantic-preserving perturbations generated via a fixed rule-based pipeline: (i) one WordNet synonym substitution among content words, using the most frequent synset and accepting the best candidate only when its cosine similarity under spaCy
en_core_web_md exceeds
; (ii) syntactic reordering with the same spaCy dependency parser, either by moving a fronted subordinate clause or by swapping coordinated clauses while preserving logical scope; and (iii) surface paraphrasing through English → French → English back-translation with
facebook/nllb-200-distilled-600M. A strategy that cannot produce a distinct perturbation retains its fixed slot and contributes zero to the
denominator; the original question is never substituted for a failed perturbation. Semantic preservation was assessed in a double-annotated validation sample, yielding Cohen’s
. RS is computed exclusively over originally correct instances
C to prevent trivially high scores for consistently-wrong models [
13,
14]:
By construction, RS is downstream of CQ: it is undefined for models with zero correctness and structurally correlated with CQ across models. This dependency is by design—robustness is only meaningful given a correct baseline—but practitioners should treat CQ–RS and CQ–ES correlations as structural rather than informative signals. For computational completeness, the implementation returns when C is empty.
Local Logical Coherence (LS) evaluates step-to-step consistency of reasoning traces using the
cross-encoder/nli-deberta-v3-small model to classify each consecutive step pair
as
contradiction,
neutral, or
entailment [
4,
11];
is the resulting binary contradiction indicator (top predicted label), not a probability. Reasoning steps are obtained by splitting generated responses at period boundaries; line breaks in locally generated responses are normalized before this split. Consecutive pairs are supplied as
premise [SEP] hypothesis, with truncation at 512 tokens and a batch size of 32. If a batched NLI call fails, the implementation assigns a neutral label to the affected pairs; if the NLI model is unavailable, it falls back to a documented lexical-negation heuristic. Models producing single-sentence responses receive
by convention, since a single atomic step admits no internal contradiction by definition. We acknowledge this is conservative: a single-sentence response may avoid reasoning entirely, and high LS should not be interpreted as evidence of deep reasoning soundness but rather as absence of detected local contradiction.
Efficiency (ES) measures the tradeoff between correctness and token cost via a harmonic mean, grounding the framework in bounded rationality [
2,
5]. Let
be the min–max normalized token count of item
i’s output, relative to the minimum and maximum token counts observed across the evaluated set for that model (
Table 2):
Stability (SS) measures the semantic similarity of reasoning traces across
runs via BERTScore F1, operationalizing Liu et al. [
24]’s finding that process stability and output consistency are decoupled. For each pair of traces
, the implementation uses BERTScore
with
distilbert-base-uncased, English language settings, and no baseline rescaling. The three pairwise comparisons induced by
are computed in a single batch and averaged. Missing or failed traces remain in the fixed
K denominator and contribute zero; Jaccard similarity is used only as a runtime fallback when BERTScore is unavailable:
For each evaluation item, the primary response is used to compute CQ, LS, and ES and also serves as the first of the responses used for CS and SS. Two additional independent responses complete the fixed-K sample, and three fixed perturbation slots are evaluated for RS. Final answers are canonicalized using the same type-aware procedure for CQ, CS, and RS, whereas LS and SS operate directly on the generated reasoning traces. Finally, the six dimension scores are aggregated using either equal weights or a deployment-specific weight vector.
3.4. Experimental Setup
The experimental design was constructed to capture variation along two axes: model access and reasoning-task structure. The model panel includes closed-source API systems, a large open-weight model accessed through an API, and smaller locally executed open-weight models. This selection enables comparisons across model scale, access conditions, and deployment constraints. The benchmark suite covers open-ended arithmetic reasoning, multiple-choice knowledge and reasoning, binary commonsense reasoning, and controlled synthetic stress tests. Accordingly, the model-by-dataset design evaluates whether the proposed dimensions remain informative across heterogeneous answer formats and reasoning demands.
Seven LLMs spanning closed-source API models and open-weight local models were evaluated (
Table 4). API models accessed via the ASU CreateAI gateway (GPT-4o-mini, Claude-Haiku-4.5, Gemini-2.5-Flash, LLaMA-3.1-70B) were queried at temperature
with
max_tokens , with the exception of Gemini-2.5-Flash, for which
max_tokens was increased to 1024: this model’s internal reasoning consumes tokens against the same budget as the visible response, and at 256 tokens responses were systematically truncated before an answer was produced (verified on held-out probes) and 1024 tokens left ample headroom (observed completions of 200–430 tokens) while imposing no change to the extraction or scoring pipeline. A minimal neutral system prompt (
“You are a helpful assistant.”) was supplied to all gateway-routed models to suppress the gateway’s own default template injection, which otherwise prepended several hundred to several thousand tokens of boilerplate context ahead of the query. DeepSeek-V3 was queried directly via the DeepSeek API (temperature
,
max_tokens , and no system prompt required). Local models (Qwen2.5-1.5B, Phi-2) were executed on an NVIDIA GTX 1650 (4 GB VRAM). Phi-2 (2.7B parameters) was loaded in float16 and Qwen2.5-1.5B (1.5B parameters) required 4-bit (NF4) quantization via
bitsandbytes to remain within the available VRAM budget alongside the evaluation pipeline’s other memory demands (tokenizer, NLI and BERTScore models loaded for LS/SS computation). Phi-2’s float16 footprint (5.56 GB peak resident memory, measured via
torch.cuda.max_memory_allocated() during a diagnostic generation pass) exceeds the GPU’s 4.30 GB dedicated VRAM capacity by approximately 1.3 GB. Execution, nonetheless, completed successfully, which we attribute to Windows’ WDDM driver-level memory virtualization: a corresponding increase in Task Manager’s Shared GPU Memory counter was observed during model loading, consistent with transparent spillover of the excess allocation into system RAM. This execution mode is functionally comparable to, although slower than, native VRAM residency. Nevertheless, because ES is computed from output token counts rather than wall-clock latency, this difference in execution speed does not affect the ES calculation, though it may partly explain the longer wall-clock runtime observed for Phi-2 relative to Qwen2.5-1.5B during evaluation.
Reproducibility note. During reproduction of the original experiments on this gateway, we identified and corrected two methodological issues in the evaluation pipeline, which are detailed here for transparency. First, the multi-strategy answer-extraction pipeline (described under Correctness below) exhibited a short-gold substring leak: for single-character or short numeric gold answers, strategy (ii) (substring containment) could match incidentally inside an unrelated token (e.g., gold “D” matching the d in “drastic”; gold “5” matching inside “25”). This inflated CQ on MMLU and StrategyQA in particular. We replaced the substring strategy, for short categorical golds, with type-aware canonical matching: numeric answers are compared as parsed floating-point values (respecting a ####-delimited final answer when present); yes/no answers require an unambiguous lexical signal (e.g., negation markers) rather than raw substring presence and multiple-choice answers require a structurally anchored option letter (e.g., following “answer is”, “correct option is”, or as the first token of the response) rather than any bare occurrence of the letter. Second, Consistency (CS) was originally computed as full-text equality across the K runs, which collapsed to near-zero for any model that rephrased a correct answer differently across runs (e.g., “The answer is 30.” vs. “5 × 6 = 30” were scored as inconsistent). CS is now computed over the same canonicalized answers used for CQ, so that paraphrases of the same underlying answer are scored as consistent. Both corrections are implemented in the released code and were applied uniformly to all seven models; all CQ, CS, RS, and ES values reported below reflect the corrected protocol. LS and SS, which operate on reasoning traces rather than extracted answers, are unaffected.
We evaluate across 975 items from four benchmarks: GSM8K [
30] (250 items; arithmetic word problems; and primarily exercises CQ and ES), MMLU [
31] (225 items from 9 reasoning subjects: logical fallacies, formal logic, abstract algebra, elementary/high-school/college mathematics, statistics, conceptual physics, and philosophy; and controlled environment for CS and SS), StrategyQA [
35] (250 items; implicit multi-step commonsense reasoning; binary yes/no; and informative for LS), and a Synthetic dataset (250 items constructed by the authors: 100 arithmetic word problems with numerical variation, 75 adversarial instances embedding deliberate logical contradictions into otherwise valid premises, and 75 robustness probes pairing each item with two surface-level paraphrases, all designed to stress-test RS and CS. Items were manually reviewed for semantic validity and absence of overlap with GSM8K training splits). Items were sampled uniformly at random from each benchmark’s designated test split using a fixed random seed (seed
), with no filtering beyond the subject categories listed above for MMLU.
Table 5 provides representative examples from each Synthetic subset.