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Controlled reasoning-efficiency study

Do Larger Reasoning Models Actually Use Tokens More Efficiently?

Starting from an Interview Claim: A Systematic Test with Open-Weight Reasoning Models

July 17, 2026 · Research Notes

The project began with a Yann Dubois interview

This project did not begin with a benchmark table. It began with Yann Dubois's interview on The MAD Podcast with Matt Turck. Dubois, who co-leads OpenAI's post-training frontiers team, made a direct connection between pretrained model scale and reasoning-token efficiency:

“If you have larger models, the amount of thinking time—so the amount of tokens they will think for—will usually decrease. […] The model already thinks through its weights when it generates a certain token. So you can decrease the number of tokens that you need to generate for thinking by increasing the size of the model […] if you basically pre-train larger models, you will get better efficiency.”
—Yann Dubois, excerpt from 24:34–25:23 in the original interview.

This passage directly motivated the study. It connects three claims: a larger pretrained model, more “thinking” already performed through its weights, and fewer explicit thinking tokens. The mechanism feels intuitive—if more capability is internalized in the parameters, inference may not need to reconstruct the same search through an equally long visible trace.

But intuition is not evidence. This is an interview statement, not an official OpenAI technical report; and “usually decrease” is not a universal claim across every family, task, or budget. A test also cannot simply compare leaderboard scores or treat any shorter output as more efficient: the model may have truncated early or failed to emit a final answer. The controlled question is:

Within the same model family, under matched tasks, output budgets, decoding rules, and repeated-sampling protocols, can the larger model reach equal or better quality with fewer visible thinking tokens?

I was also exploring Auto Research: whether frontier models could help formulate hypotheses, design experiments, orchestrate remote runs, audit artifacts, diagnose failures, and converge the evidence into a reproducible report. I therefore turned Yann's claim into a concrete research question.

Public discussions by Noam Brown and Josh McGrath then supplied two missing pieces. Brown stressed that additional test-time compute becomes useful only when the model is capable enough to exploit it. McGrath proposed judging progress on a two-dimensional quality–token plane, where the valuable movement is up and to the left. Together, the three perspectives define the study: Yann supplies the scale–weights efficiency mechanism, Brown the capability precondition, and McGrath the measurement coordinates.

The experimental design follows from that framing: compare two sizes within each family, keep the task and generation protocol fixed, sweep multiple output budgets, repeat each problem, and admit token-efficiency evidence only when final-answer validity, token partitioning, and truncation pass predefined gates.

GPT-5.5 and GPT-5.6 were research collaborators throughout the process. They helped trace and challenge the hypothesis, design the experimental matrix, audit remote runs, diagnose measurement failures, analyze accepted artifacts, and prepare the report, paper draft, and this article. They are not evidence for the conclusion: the empirical claims in this article come from logged jobs and validated result files.

Figure 1 summarizes eight decisions that materially changed the study's direction. Orange side branches are research paths diagnosed and downgraded to supplementary or boundary evidence, not simply failed executions.

Vertical Auto-Research map showing eight decisions from an interview claim to a validated conditional conclusion.
Figure 1. How the Auto-Research study converged from an interview claim to a validated conclusion. The blue solid line is the adopted research path; orange dashed branches are routes downgraded to boundary evidence after diagnosis, not failed executions by definition.

From a broad model screen to two controlled families

The project did not begin with GPT-OSS and Qwen3.5 as two hand-picked “winners.” The initial candidate pool also included Ministral-3, Qwen3, and GLM-4.5. We ran pilots first, then asked whether each family could support an interpretable within-family scale comparison.

Admission contract. A family needed two meaningfully comparable sizes; matched tokenizer, template, parser, and generation protocol; enough task, budget, and repeated-sampling coverage; and final-validity, token-partition, and truncation quality sufficient for trustworthy token measurement.

GPT-OSS had one additional study-design advantage. OpenAI's official model card already supplied a 20B/120B within-family scale pair, the official Harmony format, and multi-effort evaluations on AIME and GPQA-Diamond. Figure 3 in particular places low, medium, and high reasoning effort on an accuracy-versus-average-CoT+Answer plane, where 120B often reaches a comparable or higher-quality region with shorter output. Those results are not part of our experiment and are not counted below, but they made GPT-OSS unusually well suited to a controlled follow-up: comparable scale points, reliable token channels, and a pre-existing quality–token prior.

GPT-OSS and Qwen3.5 Dense survived that screen and formed the cleanest controlled comparisons. Ministral-3, Qwen3, and GLM-4.5 were excluded from the main matrix because of insufficient measurement validity, architectural or training-recipe confounding, real quality reversals, or strong inference-budget interactions. Their results are retained as failure-mode and boundary evidence.

The final evidence scope was frozen by comparability and measurement validity, not by whether a family confirmed the hypothesis. Families outside the main matrix remain part of the result.

Experimental setup

FamilySmallerLarger
GPT-OSS20B120B
Qwen3.5 Dense9B27B

The experiment uses a unified K=8 protocol. It compares four models across four tasks—MATH500, GPQA-Diamond, AIME 2024, and AIME 2025—and four maximum output budgets of 4K, 8K, 16K, and 32K. Every model–problem–budget cell contains eight independent rollouts.

4models
4tasks
4budgets
8rollouts
TaskIndependent problems nRollouts per problem
MATH5005008
GPQA-Diamond1988
AIME 2024308
AIME 2025308

Inference treats the problem as the independent sampling unit. The paired 95% intervals use 2,000 problem-bootstrap resamples; whenever a problem is sampled, all K=8 rollouts for both model sizes are kept together. K=8 reduces within-problem decoding noise, but AIME still has an effective benchmark sample size of 30 rather than 240.

GPT-OSS high-effort is treated only as an auxiliary analysis and does not gate the primary conclusion; the other candidate families are retained in the failure diagnostics below.

Quality is measured primarily by average accuracy over eight rollouts (avg@8). pass@8 is auxiliary. We separately count thinking tokens, answer tokens, and total generated tokens.

Measurement gate. Strict accuracy always counts a missing or unparsable final answer as wrong. A token-efficiency comparison is admitted only when final validity and thinking/answer partition validity are both at least 95%. A 32K cell must also truncate no more than 5% of the time. Failed cells retain strict accuracy but are excluded from token-efficiency inference.

What the final aggregate says

The result is family-conditional, not universal.

FamilyEligible cellsJoint dominanceQuality-matched savingsVerdict
GPT-OSS544/4Strong support
Qwen3.5 Dense111/1Strong support

The table below reports the paired 32K avg@8 effect, defined as larger minus smaller. An interval excluding zero supports the accuracy direction over the observed benchmark-problem distribution. “Ineligible” limits token-efficiency inference only; strict accuracy and its uncertainty are retained.

FamilyTasknavg@8 differencePaired problem-bootstrap 95% CIToken-efficiency gate
GPT-OSSMATH500500+1.35 pp[+0.60, +2.18] ppeligible
GPT-OSSGPQA-Diamond198+6.25 pp[+3.41, +9.34] ppeligible
GPT-OSSAIME 202430−2.92 pp[−8.33, +2.50] ppeligible
GPT-OSSAIME 202530+9.17 pp[+3.75, +15.00] ppineligible
Qwen3.5 DenseMATH500500+4.68 pp[+3.65, +5.73] ppeligible
Qwen3.5 DenseGPQA-Diamond198+8.14 pp[+5.49, +10.98] ppineligible
Qwen3.5 DenseAIME 202430+8.33 pp[+3.33, +14.17] ppineligible
Qwen3.5 DenseAIME 202530+15.83 pp[+8.75, +23.75] ppineligible
MATH500 quality versus visible thinking tokens across 4K, 8K, 16K, and 32K budgets for GPT-OSS and Qwen3.5, with problem-bootstrap 95% confidence intervals.
Figure 2. The Josh McGrath-style two-dimensional view extended across 4K, 8K, 16K, and 32K budgets on MATH500. Vertical bars are problem-bootstrap 95% intervals over 500 problems, keeping all K=8 rollouts for each sampled problem together. Each family has its own thinking-token x-axis, so absolute lengths are not compared across tokenizers. GPT-OSS 120B is already near its accuracy plateau around 8K; the focused middle panel separates its overlapping readings. Qwen3.5 retains a clearly rising budget trajectory. Hollow points retain strict accuracy but are excluded from token-efficiency claims.
GPQA-Diamond quality versus visible thinking tokens across 4K, 8K, 16K, and 32K budgets for GPT-OSS and Qwen3.5, with problem-bootstrap 95% confidence intervals.
Figure 3. Four-budget trajectories on GPQA-Diamond. Vertical bars are problem-bootstrap 95% intervals over 198 problems. GPT-OSS 120B enters a 71.4%–73.1% plateau from 8K onward; the focused panel makes the overlapping readings legible. At 32K, GPT-OSS uses 60.9% fewer thinking tokens than 20B while accuracy rises from 66.9% to 73.1%; the paired accuracy-difference interval is [+3.41, +9.34] percentage points. Qwen3.5 shows a clear four-budget quality climb, but every GPQA cell fails a measurement gate, so the trajectory remains strict-accuracy description rather than admissible token-efficiency evidence.

Relation to the official GPT-OSS model card. Its Figure 3 already plots 20B/120B quality–CoT+Answer curves on AIME 2025 and GPQA-Diamond. The plotted points align with Table 3's with tools rows and primarily demonstrate test-time scaling as reasoning effort increases. The closest comparison to our no-tools, fixed-medium, hard-cap protocol is instead Table 3's medium / no tools column: GPQA-Diamond is 66.0%→73.1%, nearly identical to our 66.9%→73.1%; AIME 2025 is 72.1%→80.0%, directionally consistent with our 74.2%→83.3%. MATH500 does not appear in the model card.

We therefore do not claim the two-dimensional presentation or the basic GPT-OSS direction as a first discovery. The more accurate contribution is a controlled replication under fixed effort, K=8, and explicit measurement gates, extended with thinking-only tokens, MATH500, and a second family, Qwen3.5. The official numbers serve as external consistency evidence; they are not pooled with our rows, confidence intervals, or acceptance statistics.

GPT-OSS: the clearest positive result

In all five eligible fixed-budget comparisons, GPT-OSS 120B uses fewer thinking tokens than 20B. In four, it is also more accurate. All four quality-matched frontier points show token savings.

  • MATH500 improves from 95.8% to 97.2%. The paired effect is +1.35 pp (95% CI [+0.60, +2.18]), while mean thinking falls by 849 tokens (95% CI [−1,028, −685]).
  • GPQA-Diamond improves from 66.9% to 73.1%. The paired effect is +6.25 pp (95% CI [+3.41, +9.34]), while mean thinking falls by 2,804 tokens (95% CI [−3,289, −2,323]).
  • AIME 2025 improves from 74.2% to 83.3%, a +9.17 pp effect (95% CI [+3.75, +15.00]). The cell is nevertheless ineligible for token-efficiency inference, so only strict accuracy is retained.

AIME 2024 has a directional reversal in the point estimate: accuracy falls from 84.6% to 81.7%. But the paired −2.92 pp effect has a 95% CI of [−8.33, +2.50], and an exact paired sign-flip test is also non-significant (two-sided p=0.383). We therefore treat it as a statistically inconclusive deviation, not an established counterexample. The thinking-token reduction is more stable: a mean difference of −4,252, with a 95% CI of [−6,071, −2,663].

Qwen3.5: positive, but narrower

On MATH500 at 32K, Qwen3.5 27B improves from 93.3% to 98.0%. The paired effect is +4.68 pp (95% CI [+3.65, +5.73]), while mean thinking falls by 1,949 tokens (95% CI [−2,155, −1,752]), corresponding to an 18.7% point estimate.

GPQA-Diamond strict accuracy also rises from 74.1% to 82.2%, a paired +8.14 pp effect (95% CI [+5.49, +10.98]). AIME 2024 and AIME 2025 have effects of +8.33 pp (95% CI [+3.33, +14.17]) and +15.83 pp (95% CI [+8.75, +23.75]). These GPQA/AIME cells fail a final-validity or truncation gate, so they remain strict-accuracy observations and are excluded from token-efficiency inference.

The parser question

Qwen3.5's AIME gate failures could initially be mistaken for a parser problem. Artifact audits show that the thinking/answer partition is valid; the dominant failure occurs during the reasoning-to-final transition, when long reasoning consumes the budget before a terminal answer is emitted.

Increasing the sample count under the same configuration would not remove this systematic finalization behavior. We therefore kept strict accuracy, excluded token-efficiency claims where required, and avoided “repairing” the dataset by selecting only well-finalized traces.

What the three ineligible families taught us

The earlier screening funnel summarized the outcome. Here we separate four diagnostic layers: whether the parser worked, whether the model completed the reasoning-to-final transition, whether scale produced a real quality advantage, and whether architecture or inference settings made the comparison uninterpretable.

FamilyParser and token partitionModel/scale behaviorConfiguration interactionClassification
Ministral-3Official parser handles completed streams; parser is not the primary cause.AIME often fails to finish; 14B is materially worse than 8B on MATH500.Long caps amplify non-finalization and truncation.Measurement failure plus a real quality reversal.
Qwen3No evidence of a primary parser failure.AIME leans larger; MATH500 favors the smaller model in both quality and tokens.MoE activation scale, post-training, and incomplete matrix are confounded.Valid pilot, but scale is not identifiable.
GLM-4.5Token partition is valid, ruling out a global parser failure.Air beats full GLM on AIME; GPQA reverses direction.High truncation and low final validity interact strongly with the 32K cap.A substantive AIME counterexample, not a stable cross-task law.

Ministral-3: not merely a parser bug

The official parser correctly handles completed streams; the main AIME failure occurs earlier, when the model spends its reasoning budget without emitting a final answer. MATH500 at 32K also shows a real reversal—7.0% for 14B versus 31.6% for 8B—so parser repair cannot recover the hypothesis. The report describes a 14B→8B→3B pruning-and-distillation cascade and an RL length increase from 32K to 80K after observed truncation. Those details make distillation path and long-reasoning sensitivity plausible clues, not proven causes. The appropriate classification is measurement failure plus a genuine smaller-model win.

Qwen3: successful execution, but scale is not a clean variable

The Qwen3 pilot showed no primary parser failure, but its direction depends on the task: AIME leans toward 235B-A22B, while on MATH500 the 30B-A3B model is both more accurate (94.2% versus 89.8%) and shorter (3.34K versus 4.04K total tokens). The report shows that the pair also differs in active parameters (3B versus 22B), depth, distillation, and post-training; official AIME inference uses a stop-thinking transition and a 38,912-token cap rather than our hard 32K cutoff. This is therefore a valid but confounded pilot, not an identifiable parameter-scale treatment. Future MoE comparisons should control active scale, training recipe, and finalization protocol together.

GLM-4.5: a real counterexample plus inference-configuration sensitivity

At 32K on AIME, GLM-4.5-Air reaches 64.4% avg@8 versus 55.0% for the full model; valid token partitions rule out a parser explanation. GPQA reverses direction and final validity is low, so the counterexample interacts strongly with output cap and exit-reasoning behavior. The report uses hybrid expert distillation and trains reasoning RL directly at 64K; our 32K cap may amplify the issue, but a seed-0 64K diagnostic still did not restore larger-model dominance. The best classification is a genuine AIME counterexample plus configuration sensitivity, best followed up with targeted budget, template, stop-condition, and forced-finalization ablations.

Three recommendations for future community studies

  1. Verify measurement eligibility before interpreting coverage. Complete coverage does not imply valid finals, valid token partitions, or acceptable truncation. A missing final should count as an error, but its token length should not enter the efficiency comparison.
  2. Control comparability before attributing an effect to scale. Test multiple output caps and report active MoE parameters, routing, and post-training differences so configuration effects are not mistaken for scale effects.
  3. Preserve genuine counterexamples. If the smaller model is better under valid measurement, it should constrain the conclusion rather than be relabeled as dirty data.

Exclusion from the main result does not mean experimental failure: it may indicate invalid measurement, an unidentifiable comparison, or a genuine counterexample.

Takeaways: what the experiment supports—and what it does not

Within some controlled model families, a larger model can achieve equal or better quality with fewer visible reasoning tokens. The confidence intervals support GPT-OSS on MATH500 and GPQA-Diamond and Qwen3.5 on MATH500; the admissible Qwen3.5 scope is narrower.
  • This is a conditional within-family pattern, not a law of parameter scale. The supported 32K accuracy effects are +1.35 pp for GPT-OSS MATH500, +6.25 pp for GPT-OSS GPQA, and +4.68 pp for Qwen3.5 MATH500, while visible thinking also falls. These results do not establish a universal relationship across architectures or training recipes.
  • Reasoning efficiency must combine quality, thinking tokens, and measurement validity. A shorter response that never reaches a valid final answer is not efficient. Final validity, token partitioning, and truncation are part of the metric, not post-hoc cleanup.
  • Families outside the main result reveal measurement failure, comparison confounding, and genuine counterexamples. “Scale” is meaningful only when architecture, post-training, active MoE scale, and tokenizer are sufficiently comparable; counterexamples should not be filtered away to manufacture a clean law.
  • Uncertainty matters most on small benchmarks. AIME has only 30 independent problems; K=8 stabilizes each problem estimate but does not turn it into 240 independent items. GPT-OSS AIME 2024 is therefore an inconclusive deviation, not an established counterexample. Visible tokens also remain different from total compute.

Research scale

Across the two Codex tasks, the validation required approximately 126.2 hours of effective Codex work—about five days and six hours. This counts active execution, tool use, and remote monitoring, while excluding long idle gaps between working sessions.

The final auditable experiment artifacts processed approximately 874 million tokens, including prompts and model generations. That remains a conservative lower bound: some early explorations and failed runs were not consolidated into the ledger, and the figure excludes tokens consumed by the GPT-5.5/GPT-5.6 research agents themselves.

Sources

  1. Noam Brown, Scaling Test Time Compute to Multi-Agent Civilizations, Latent Space, June 20, 2025.
  2. Yann Dubois, OpenAI's Yann Dubois: Why AI Progress Suddenly Feels Real, The MAD Podcast with Matt Turck, May 21, 2026; scale–weights–thinking-token passage at 24:34–25:23.
  3. Josh McGrath, [State of Post-Training] From GPT-4.1 to 5.1: RLVR, Agent & Token Efficiency, December 31, 2025; token-efficiency chapter at 13:12.
  4. Liu et al., Ministral 3, arXiv:2601.08584, 2026.
  5. Yang et al., Qwen3 Technical Report, arXiv:2505.09388, 2025.
  6. Zeng et al., GLM-4.5: Agentic, Reasoning, and Coding (ARC) Foundation Models, arXiv:2508.06471, 2025.