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Beyond Exponential Decay: Rethinking Error Accumulation in Large Language Models

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Beyond Exponential Decay:
Rethinking Error Accumulation in Large Language
Models

Anonymous Author(s)
Affiliation
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Abstract

A common pessimistic argument holds that autoregressive language models suffer
exponential decay in correctness over long outputs: if each token has independent
error probability e, then (1 − e) n → 0 as n grows. The argument is clean to state
and widely cited. It is also brittle, and three lines of recent empirical work make the
cracks visible. The first is that only a small subset of tokens—roughly 5% to 10%
in the studies that have actually measured it—genuinely depends on long-range
context; the rest get more predictable, not less, as context accumulates. The second
is geometric: LLM embeddings organize into stratified low-dimensional manifolds,
so once a model is working inside one semantic region it tends to stay there
even when individual tokens slip. The third concerns what happens when models
do err on the consequential tokens—errors turn out to be idiosyncratic across
samples rather than systematic, which is why majority-vote ensembles recover
so much accuracy. Pulling these together gives a two-rate model, P (correct) ≈
(1−e key ) k ·(1−e non ) n−k , in which k scales sublinearly with n and e non approaches
zero with sufficient context. The predicted decay is, at worst, stretched-exponential;
often power-law; and when k saturates at some task-specific k max , constant in n.
A number of recent capabilities—anchor compression at 99% context reduction,
128K-token retrieval on consumer GPUs, self-consistency gains on reasoning
benchmarks—then read as natural consequences of one structural fact rather than
independent engineering wins: long-context reliability hinges on a handful of
decision points, not on uniform per-token accuracy.

1

Introduction

Autoregressive language models, the argument goes, are doomed for long outputs. If each token has
even a 1% error rate then a 100-token chain is correct only (0.99) 100 ≈ 37% of the time, and longer
chains decay exponentially toward zero [LeCun, 2023, Dziri et al., 2023]. The argument is clean, and
it has been used to predict a hard ceiling on what autoregressive systems can do.

What modern LLMs actually do is harder to square with this picture. Multi-page outputs hold
together. Mid-generation self-correction is routine—later tokens revise earlier interpretations, a
behavior Gwern [2023] called out as incompatible with monotonically increasing error. The attention
patterns are lopsided: 96% of cumulative attention weight in Llama-3 concentrates on ∼ 1% of the
context [Liu et al., 2024], and only about 9% of tokens in natural text show meaningful dependence
on distant context [Fang et al., 2024]. With the right test-time strategy, a 1B-parameter model can
match or beat a 405B model on specific reasoning tasks [Venture Research, 2025]. None of this is
consistent with uniform per-token error.

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Our reading is that the independent-error model fails because it averages over a heterogeneous
population of tokens. A small fraction—key tokens—carry the load of long-range dependency and
global coherence. The rest are constrained by local syntax and the accumulating context, and their
error rate goes to zero rather than to a constant. Three threads of recent work make this concrete:
Fang et al. [2024] on which tokens actually need long context, Li and Sarwate [2025] on the stratifiedmanifold organization of embeddings, and Wang et al. [2023] on the convergence of correct reasoning
paths under sampling. Combined, they produce a refined model:

P (correct) ≈ (1 − e key ) k · (1 − e non ) n−k ,

(1)

where k is the number of key tokens, e key their error rate, and e non the much lower error rate for the
remaining n − k. Because k scales sublinearly with n—logarithmically, as a fractional power, or
saturating at some k max —and because e non → 0 with context, the predicted decay is far gentler than
(1 − e) n .

Contributions. (1) A two-rate error model that distinguishes key from non-key tokens and makes
the dependence on k(n) explicit (§3). (2) A synthesis of evidence from three recent research streams—
attention sparsity, embedding geometry, and ensemble convergence—that supports each component
of the model (§4). (3) An accounting of how this framework reframes existing systems-level results
(anchor compression, retrieval-augmented attention, self-consistency, tool integration) as predictable
consequences of a single structural fact rather than independent engineering wins (§5).

2

Related Work

Error compounding. The exposure-bias problem is old. Bengio et al. [2015] formalized it:
models trained with teacher forcing must, at inference time, condition on their own potentially noisy
output, so small errors can compound through state updates. LeCun [2023] extended the worry to
autoregressive LLMs in the now-familiar form—if each token has error probability e, sequence-level
correctness decays as (1 − e) n . The bound is tight when independence really holds, and loose
otherwise; transformers attending backward over their own output is exactly the case where it goes
loose, and Gwern’s inner-monologue evidence [Gwern, 2023] of error rates that decrease at certain
points in a sequence is hard to reconcile with strict monotonic accumulation. We keep the per-token
decomposition but partition tokens by their long-range dependency.

Long-context utilization. Liu et al. [2023] documented the lost-in-the-middle effect—models
disproportionately attend to material near the beginning and end of the prompt. The same skew was
given a sharper edge by Fang et al. [2024], whose long-short difference (LSD) metric finds only ∼ 9%
of tokens in natural text scoring LSD> 2. Liu et al. [2024] showed 96% of cumulative attention
weight concentrating on ∼ 1,000 tokens out of 100,000 in Llama-3, and used the observation to
enable 128K-token contexts on consumer GPUs. Anchor compression [Pang et al., 2024] reaches
99% context reduction with < 1.5% accuracy loss. Each of these papers treats sparsity as an empirical
fact about a particular system; we read them as direct evidence for k ≪ n.

Embedding geometry. Li and Sarwate [2025] probed LLM embedding spaces with sparse mixtureof-experts and found a stratified-manifold structure: a union of low-dimensional submanifolds aligned
with semantic domain. The story gets more concrete with Robinson et al. [2025], who distinguished
signal from noise dimensions in token embeddings—perturbing signal dimensions reroutes outputs,
perturbing noise dimensions does not. Viswanathan et al. [2024] link intrinsic dimensionality to
prediction loss; high-confidence contexts collapse to lower-dimensional representations. And Gao
et al. [2023], probing intermediate layers, recover the correct answer from the model’s internals more
than 80% of the time even when the surface output was wrong. Compartmentalized representations,
signal/noise separation, dimensional collapse under confidence: this is what lets the model absorb the
small token-level slips without breaking coherence at the semantic level.

Ensemble reasoning. Self-consistency, in Wang et al. [2023]’s formulation, is almost embarrassingly simple: sample multiple reasoning paths, take the majority answer. The gain was +17.9 points
on GSM8K, with no retraining. Tree-of-Thoughts [Yao et al., 2023] extends the idea with structured
tree search at high-uncertainty branch points and pulls GPT-4 on Game-of-24 from 4% to 74%. Li
et al. [2023] sort the effects by error type, separating systematic errors (knowledge gaps—similar

2

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across samples) from idiosyncratic ones (variable across samples), and that distinction explains
why ensembles work for reasoning but not for retrieval. The size of these effects is the part the
independent-error model cannot absorb. If errors compounded uniformly, multiple samples would
yield multiple failures, not a more accurate mode.

3

Theoretical Framework

We develop the two-rate model in three stages: the partition of tokens into key and non-key, the
manifold dynamics that structure error correlation, and the redundancy gain that ensemble methods
extract.

3.1

The independent-error argument assumes every token carries equal weight in the failure probability.
It does not. Key tokens are the ones whose correctness genuinely depends on long-range context
or global knowledge—factual claims, logical operators, points of co-reference, transitions between
topics. Non-key tokens are governed by local regularity: syntax, frequent collocations, content
already established by the surrounding text. Their error rate is small and decreases as more context
accumulates.

Two-Rate Error Model

In a sequence of length n, let k count the key tokens. The empirical estimate of k/n from Fang et al.
[2024] is ∼ 9%; adversarial-perturbation studies converge on a similar range [Morris et al., 2022].
We hypothesize that k grows sublinearly with n, possibly saturating at a task-specific k max : even
a book-length argument operates within a finite knowledge frame requiring a bounded number of
critical decisions. With per-token error rates e key (large) and e non (small, decreasing in context), Eq. 1
gives three regimes:

1. Logarithmic key-token growth (k ∼ log n): polynomial decay n −c , much slower than
exponential.
√
2. Fractional-power growth (k ∼ n): stretched-exponential decay.
3. Saturating (k → k max ): reliability becomes constant in n once the key facts are committed.

The third regime is the strange one. Pang et al. [2024] achieved 99% context reduction with < 1.5%
accuracy loss—a result that requires k to be effectively bounded for the relevant tasks. There is no
way to express that under exponential decay; the functional form forbids it.

3.2

Stratified Manifold and Error Correlation

The (1 − e) n form also assumes errors are independent across positions. They are not. The
embedding space’s stratified structure [Li and Sarwate, 2025] introduces correlation, and we can
read the dynamics off it directly. Treat the model’s hidden state as moving along a manifold M C
determined by the prevailing context. Most errors are minor—a synonym substitution, a grammatical
slip, a momentary wobble that stays on M C and has no downstream effect. Disruptive errors are
different: a key-token mistake jumps the trajectory onto a different manifold M C ′ , after which
subsequent tokens cohere with the wrong commitment. The result is a fluent-but-wrong continuation.
Errors cluster rather than scatter.

This correlation structure cuts the union-bound failure probability. For small k,

P (any disruptive error) ≤ k · e key ,

(2)

which, when k ≪ n, is substantially below 1 − (1 − e) n . The manifold structure also explains
the compartmentalization Gao et al. [2023] document: intermediate layers preserve correct internal
representations even when the surface output strays, because the hidden-state trajectory remains on
the correct manifold even when token sampling does not.

3.3

When key-token errors are idiosyncratic across samples—different paths fail at different junctions—
majority-vote ensembles can recover the correct answer. For m samples with error correlation

Self-Consistency and Redundancy Gain

3

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ρ,

e (eff)
key = f (ρ, m) · e key ,

(3)

where f → 1 at ρ = 1 (perfect correlation, no gain) and f → e m−1
at ρ = 0 (independent errors,
key
exponential gain). Wang et al.’s self-consistency results [Wang et al., 2023] sit closer to the ρ = 0
regime than to ρ = 1, which is why a method that adds no parameters and no training data can lift
GSM8K accuracy by 17.9 points: the gain is structural, not a property of the sampling temperature.

Costello et al. [2025] push this further: as a model’s Pass@1 accuracy improves through iterative
self-training, the marginal gain from majority voting falls. Correct reasoning paths cluster on a narrow
manifold; incorrect ones fan out. Ensemble methods only help when the model’s spread of guesses
straddles the right region.

4

Empirical Evidence

Three predictions, three lines of evidence. The framework says k/n is small and stable; that token
errors correlate via manifold geometry; and that correct reasoning paths converge while incorrect
ones diverge. The supporting work for each comes from a different methodology, which is what
makes the convergence interesting.

4.1

The most direct measurement is Fang et al. [2024]’s LSD metric: 9% of tokens in natural text
qualify as key (LSD> 2), and perplexity restricted to those tokens correlates with downstream task
performance at Pearson ≈ −0.96. Perplexity on the other 91% tracks task success at essentially
zero correlation. Adversarial robustness work, working from the opposite direction, lands in the
same band—Morris et al. [2022] flip model decisions by perturbing 5%–10% of strategically chosen
tokens, while random perturbation of much larger fractions does nothing. The 5%–10% figure recurs
across methodologies built to measure different things; that is what one would expect if it were a
structural property of natural language rather than a dataset artifact.

Key-Token Sparsity

The systems-level corollary is sharp. Liu et al. [2024] reach 128K-token effective context on consumer
GPUs by computing attention only over the top ∼ 1,000 tokens by attention mass, recovering > 90%
of full-attention scores in the process. Anchor-LLM [Pang et al., 2024] compresses sequence
information into a single token at 99% reduction with < 1.5% accuracy loss. Neither method would
work if token importance were uniform; both work because it is not.

4.2

Li and Sarwate [2025]’s sparse-MoE probe of frozen LLM embeddings finds a union of lowdimensional manifolds aligned with semantic domain (scientific text, dialogue, code), with measurably different intrinsic dimension across regions. Robinson et al. [2025]’s fiber-bundle analysis
distinguishes regular-neighborhood tokens (manifold interior; perturbation has minimal effect) from
irregular-neighborhood tokens (manifold junctions; perturbation reroutes generation). The mapping
to our key/non-key partition is direct: irregular-neighborhood tokens are exactly the points where a
small input change can move the trajectory between manifolds.

Stratified Manifold Structure

Viswanathan et al. [2024] link this to confidence: prompts that elicit low-intrinsic-dimensional
representations correlate with lower prediction loss. The model’s state contracts as confidence rises—
which is why the per-token error rate e non should fall, not stay constant, as context accumulates.

Gao et al. [2023] probe intermediate layers and recover correct answers from > 80% of cases where
the final output was wrong. The information was preserved internally; only the surface form failed.
This is the manifold-stays-correct behavior our framework predicts.

4.3

Wang et al. [2023] showed that self-consistency lifts GSM8K by 17.9 points and SVAMP by 11.0,
with no model change. The mechanism, on our reading, is that correct paths concentrate near a
low-dimensional attractor while incorrect ones disperse—so majority voting picks out the attractor’s

Convergent Reasoning Paths

4

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mode. Yao et al. [2023]’s Tree-of-Thoughts moves GPT-4 on Game-of-24 from 4% to 74% by
branching at high-uncertainty points specifically. Li et al. [2023] explain why these methods work
for reasoning and not for knowledge retrieval: knowledge gaps produce systematic errors (every
sample fails the same way); reasoning slips produce idiosyncratic ones (samples fail differently).
The framework’s two error rates accommodate both: e key rises uniformly when the model lacks the
relevant fact, and ensembling cannot help.

A summary of how the systems-level results map onto the framework’s three pillars appears in
Appendix B.

5

Practical Implications

The framework is not just a description of why (1 − e) n is wrong. It also predicts where computation
should go, how context should be managed, and what to evaluate.

Sparse attention and context compression. If k ≪ n, attention does not need to be dense.
Pang et al. [2024]’s anchor compression and Liu et al. [2024]’s top-k attention are the existing
demonstrations; Wu et al. [2024]’s dynamic KV-cache selection is another point on the same curve.
These methods stop being clever tricks and become predictable: dense attention pays a quadratic cost
to recover a sparse signal.

Targeted compute at decision points. Errors concentrate at manifold transitions, so compute
should too. Moshkov et al. [2025]’s tool-integrated reasoning fires Python execution at high-entropy
spans rather than uniformly. Adaptive computation time [Xin et al., 2023] lets confident tokens skip
layers altogether, saving 40%–60% on SST-2 and TriviaQA. The adaptive-temperature decoding
of Zhu et al. [2024] raises exploration at uncertain tokens and damps it elsewhere. Three different
prescriptions, one underlying instruction: spend cycles where the manifold is about to fork.

Strategic ensembles. Wang et al. [2023]’s self-consistency, Yao et al. [2023]’s tree search, and
Moshkov et al. [2025]’s GenSelect all exploit the convergence-of-correct-paths structure. The
framework explains why they work—and predicts when they will not, namely when errors are
systematic rather than idiosyncratic, as in pure knowledge-retrieval tasks [Li et al., 2023].

Evaluation aligned with key tokens. Plain perplexity averages over a population the model is
trying to handle separately, which is why it underperforms as a predictor. Fang et al. [2024]’s
LongPPL restricts perplexity to key tokens and lifts the correlation with downstream performance
to r = −0.96 from a near-zero baseline. Costello et al. [2025]’s success-plateau curves show what
reliability looks like up close: sharp drops after extended plateaus—the staircase one would expect
under our model, not the smooth exponential decay of the alternative.

A more speculative implication—modular reasoning architectures that route by manifold region,
building on the alignment-not-scale results of Costello et al. [2025]—we defer to Appendix A.

6

Limitations

The framework is a synthesis, not a derivation. Three cautions belong on record. The two-rate model
is descriptive: k, e key , and e non are observable in principle but not yet jointly measured on a single
benchmark, so the predicted decay regimes are arguments from supporting evidence rather than fitted
curves. The manifold-structure account leans on Li and Sarwate [2025] and Robinson et al. [2025]
for direct geometric evidence; both are recent, and replication on larger model scales would tighten
the claim. The convergent-paths claim holds where Li et al. [2023] call errors idiosyncratic; we have
no quantitative criterion for distinguishing the idiosyncratic from the systematic regime in advance,
only the post-hoc observation that ensemble methods help in one and not the other.

7

Conclusion

The independent-error argument was always going to fail in one of two places. Either some tokens
would matter more than others, breaking the per-token uniformity; or errors would correlate, breaking

5

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the independence. As it turns out, both fail at once. The empirical literature has been steadily
accumulating the evidence: 5%–10% of tokens carry the long-range dependency, embeddings stratify
into manifolds that compartmentalize errors, and ensemble methods extract gains that any uniformerror model rules out.

The two-rate model in Eq. 1 is a small change to the algebra and a large change to the predicted
behavior. Reliability depends on k key decisions, not on n tokens; and k scales sublinearly, often
saturating. Modern LLMs hold coherence across thousands of tokens not because the underlying
(1 − e) n is being beaten by clever engineering, but because (1 − e) n was the wrong functional form
to begin with.

The systems-level consequences are already visible. Anchor compression, retrieval-augmented
attention, tool-integrated reasoning, and self-consistency all gain explanatory unity once they are
read as instances of a single principle: identify where the manifold forks, and put the compute
there. Future work should make k(n) measurable on a fixed benchmark, derive tighter bounds from
attention-pattern statistics rather than from heuristic union bounds, and connect token-level decay to
the reasoning-step decay that bears more directly on agentic systems.

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A

Architectural Implications: Modular Reasoning

The stratified-manifold view suggests an architectural prescription the main body only gestures at:
instead of scaling monolithic models, route reasoning subtasks to specialized models aligned with
manifold regions. The clearest existing evidence comes from alignment-not-scale work. Costello et al.
[2025]’s Trace-Prune-Train pipeline shows that smaller models (2–9B parameters) iteratively finetuned on their own pruned reasoning traces can match models 30× larger on GSM8K—improving
Gemma2-2B from 41.9% to 57.6% Pass@1, Gemma2-9B to 82% (matching LLaMA-3.1-70B), and
LLaMA-3.1-70B to 91% (above GPT-4o’s 82%). Whether explicit routing on top of these aligned
smaller models compounds the gains, or runs into a ceiling once the routed-to manifold is itself
stratified, is the natural next question; we are not aware of a definitive empirical answer.

The pattern across these systems is consistent. Fitting the manifold beats expanding the parameter
count, when the task population is narrow enough that the manifold is well-defined. The open
question is how broad a domain a single specialized model can cover before its internal stratification
reasserts itself and the routing problem reappears one level down. We do not attempt to settle that
here; it is a question for empirical work that systematically varies routing granularity.

B

Extended Case Studies in Advanced Reasoning Systems

The main body summarizes the systems-level evidence at a high level. Three case studies bear closer
reading.

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AIMO-2 (Moshkov et al. [2025]). The winning solution to the AI Mathematical Olympiad combines all three pillars of the framework. Tool integration fires at high-entropy spans, addressing
key-token uncertainty directly; the dataset-creation pipeline exploits the structured nature of correct
reasoning paths to generate training data; GenSelect leverages the convergent-paths property to
pick the best candidate solution from many. The system reaches state-of-the-art on AIME and
Harvard-MIT Mathematics Tournament problems. Most striking, the GenSelect mechanism works
on compressed summaries of reasoning traces, which would be impossible if errors were spread
uniformly across the full output: the summaries would lack the discriminating signal.

Test-time compute scaling (NVIDIA AI Research [2023], Venture Research [2025]). Optimal
test-time strategy depends on problem difficulty and model size. Beam search dominates best-of-
N on hard problems for sub-7B models; the order reverses on easier problems for larger models.
The framework reads this as a direct consequence of k varying with task: harder tasks have more
decision points to traverse correctly, rewarding search-based exploration; easier ones have few,
rewarding sampling-based ensembling. The two-orders-of-magnitude result—an optimized 1B model
outperforming a 405B model on specific reasoning tasks [Venture Research, 2025]—is exactly what
an independent-error model rules out and what the two-rate model predicts under saturation.

Attention concentration in production models (Liu et al. [2024]). Llama-3 places 96% of
cumulative attention weight on ∼ 1,000 tokens out of 100,000. RetrievalAttention exploits this
directly: at generation time, only the top-mass tokens enter attention, with the rest treated as a
nearest-neighbor lookup. The result is 128K effective context on a single RTX 4090. The structural
claim is the same one k ≪ n encodes; the engineering is just paying attention to it.

A consolidated summary of how each result maps onto the framework’s three pillars appears in
Table 1.

Table 1: How systems-level results map onto the framework’s three pillars.

Challenge

Independent-error
view

Two-rate view

Exemplar systems

han-

Uniform attention over
all tokens

Sparse retrieval focused
on key tokens

Anchor LLMs [Pang et al.,
2024]; RetrievalAttention
[Liu et al., 2024]

Compute allocation

Equal resources for all
tokens

Targeted at manifold
transitions

Tool integration [Moshkov
et al., 2025]; ACT [Xin
et al., 2023]

Error reduction

Independent samples,
multiplicative gain

Branching at uncertain
junctions

Self-consistency
[Wang
et al., 2023]; GenSelect
[Moshkov et al., 2025]

Evaluation

Uniform perplexity

Key-token-restricted
metrics

LongPPL [Fang et al.,
2024];
success-plateau
curves [Costello et al.,
2025]

Architecture

Scale monolithic models

Alignment over scale

TPT [Costello et al., 2025]

Long-context
dling

8

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NeurIPS Paper Checklist

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