Scaling Reasoning Models To Longer Chains

via “reasoning chain annotation and step-by-step decomposition”

Multi-turn conversation dataset for steerable models.

Unique: Explicitly annotates intermediate reasoning steps within conversation data, treating reasoning as a learnable component rather than an emergent behavior. Enables supervised training of reasoning quality, not just answer correctness.

vs others: More structured than datasets that only include final answers (like basic Q&A datasets) because it provides explicit supervision for intermediate reasoning steps, enabling more reliable and verifiable model reasoning.

via “reasoning and problem decomposition with chain-of-thought patterns”

This is a series of models designed to replicate the prose quality of the Claude 3 models, specifically Sonnet(https://openrouter.ai/anthropic/claude-3.5-sonnet) and Opus(https://openrouter.ai/anthropic/claude-3-opus). The model is fine-tuned on top of [Qwen2.5 72B](https://openrouter.ai/qwen/qwen-...

Unique: Inherits Claude's explicit chain-of-thought training approach, which emphasizes showing reasoning work as part of the output rather than reasoning internally, making reasoning patterns visible and auditable

vs others: More transparent reasoning than models without explicit chain-of-thought training, but less specialized than models fine-tuned specifically on mathematical reasoning datasets or formal logic

via “extended reasoning with implicit chain-of-thought”

Grok 4 is xAI's latest reasoning model with a 256k context window. It supports parallel tool calling, structured outputs, and both image and text inputs. Note that reasoning is not...

Unique: Implicit reasoning allocation based on problem complexity, with reasoning traces integrated into output without explicit token budget management, contrasting with OpenAI's explicit reasoning token approach

vs others: More transparent reasoning than GPT-4o (which hides reasoning) but less controllable than o1 (which offers explicit reasoning token budgets); better for exploratory reasoning where depth is problem-dependent

via “extended-chain-of-thought-generation”

Hermes 4 70B is a hybrid reasoning model from Nous Research, built on Meta-Llama-3.1-70B. It introduces the same hybrid mode as the larger 405B release, allowing the model to either...

Unique: Combines 70B parameter scale with process-reward modeling to maintain reasoning coherence across 10+ step chains, whereas smaller models typically degrade after 3-4 steps due to context drift and accumulated errors

vs others: Produces more reliable multi-step reasoning than GPT-3.5 while being more cost-effective than GPT-4 for reasoning tasks, with explicit step visibility that proprietary models don't expose

via “semantic-reasoning-with-chain-of-thought-decomposition”

GPT-5.2 is the latest frontier-grade model in the GPT-5 series, offering stronger agentic and long context perfomance compared to GPT-5.1. It uses adaptive reasoning to allocate computation dynamically, responding quickly...

Unique: Combines chain-of-thought reasoning with adaptive computation allocation, enabling transparent reasoning that automatically allocates more tokens to complex steps

vs others: More efficient reasoning than GPT-4 Turbo due to adaptive allocation, and more transparent than Claude 3.5 Sonnet for step-by-step problem decomposition

via “extended-reasoning-chain-of-thought-generation”

o3 is a well-rounded and powerful model across domains. It sets a new standard for math, science, coding, and visual reasoning tasks. It also excels at technical writing and instruction-following....

Unique: Implements internal extended thinking with computational budget allocation — the model allocates more inference compute to reasoning phases before answer generation, unlike standard LLMs that generate reasoning and answers in a single forward pass. This is achieved through a two-phase architecture where reasoning tokens are generated in a hidden reasoning phase before final output.

vs others: Outperforms GPT-4 and Claude 3.5 on math olympiad problems and complex reasoning tasks by 15-40% due to extended thinking budget, but at significantly higher latency and cost than standard models

via “reasoning and chain-of-thought decomposition”

The Qwen3.5 27B native vision-language Dense model incorporates a linear attention mechanism, delivering fast response times while balancing inference speed and performance. Its overall capabilities are comparable to those of...

Unique: Linear attention enables efficient reasoning over long chains of thought without quadratic slowdown — can maintain coherent reasoning across 50+ intermediate steps, whereas quadratic attention models degrade significantly with reasoning depth

vs others: More efficient reasoning than Llama 3.2 for long chains of thought due to linear attention, but less capable than Claude 3.5 Sonnet or GPT-4 for highly complex multi-domain reasoning due to smaller parameter count

via “reasoning and problem-solving with chain-of-thought decomposition”

GPT-5.3 Chat is an update to ChatGPT's most-used model that makes everyday conversations smoother, more useful, and more directly helpful. It delivers more accurate answers with better contextualization and significantly...

Unique: GPT-5.3 uses improved training on reasoning-heavy tasks and synthetic chain-of-thought data to produce more reliable intermediate steps and better error detection compared to GPT-4, with architectural support for longer reasoning traces without proportional quality degradation

vs others: Produces more coherent and verifiable reasoning chains than Llama 2 or Mistral due to superior training on mathematical and logical reasoning tasks, though specialized reasoning models (e.g., AlphaProof) may outperform on formal mathematics

via “extended-reasoning-chain-of-thought-generation”

ERNIE-4.5-21B-A3B-Thinking is Baidu's upgraded lightweight MoE model, refined to boost reasoning depth and quality for top-tier performance in logical puzzles, math, science, coding, text generation, and expert-level academic benchmarks.

Unique: Uses proprietary A3B (Adaptive Attention-Based Branching) mechanism that dynamically allocates compute across reasoning paths rather than fixed-depth chains, enabling adaptive reasoning depth based on problem complexity. This differs from static chain-of-thought approaches by treating reasoning as a branching tree with learned pruning heuristics.

vs others: Outperforms GPT-4 and Claude on mathematical reasoning benchmarks while maintaining 21B parameter efficiency through MoE architecture, making it faster and cheaper for reasoning-heavy workloads than larger closed-source models

via “reasoning chain decomposition and step-by-step problem solving”

Qwen Plus 0728, based on the Qwen3 foundation model, is a 1 million context hybrid reasoning model with a balanced performance, speed, and cost combination.

Unique: Implements chain-of-thought reasoning through prompt-based guidance rather than architectural modifications, enabling flexible reasoning depth control without model retraining

vs others: More cost-effective than specialized reasoning models (o1) for moderate complexity problems; produces transparent reasoning vs black-box outputs; trades off reasoning depth vs cost and latency

via “reasoning and chain-of-thought problem solving”

Meta's Llama 3.1 — high-quality text generation and reasoning

Unique: Explicitly trained for chain-of-thought reasoning across all three variants, with the 405B model claiming state-of-the-art performance. Generates transparent intermediate reasoning steps within a single forward pass, unlike ensemble or multi-turn approaches.

vs others: Provides transparent reasoning comparable to Claude 3.5 Sonnet and GPT-4o, but runs locally without API calls. Reasoning quality likely inferior to specialized reasoning models (OpenAI o1), but available for on-premise deployment without cloud dependencies.

via “reasoning and chain-of-thought decomposition”

GPT-4.1 Mini is a mid-sized model delivering performance competitive with GPT-4o at substantially lower latency and cost. It retains a 1 million token context window and scores 45.1% on hard...

Unique: Learns chain-of-thought patterns from training data rather than using explicit prompting tricks, enabling more natural and flexible reasoning decomposition that adapts to problem complexity without manual prompt engineering

vs others: More reliable reasoning than GPT-3.5 Turbo and comparable to GPT-4o on hard problems, while maintaining lower latency through architectural efficiency rather than brute-force scaling

via “reasoning and multi-step problem solving”

A 12B parameter model with a 128k token context length built by Mistral in collaboration with NVIDIA. The model is multilingual, supporting English, French, German, Spanish, Italian, Portuguese, Chinese, Japanese,...

Unique: Mistral Nemo's instruction-tuning includes reasoning tasks and chain-of-thought examples, enabling it to generate explicit reasoning steps when prompted. The 128k context window enables longer reasoning chains than smaller-context models.

vs others: Reasoning capability is weaker than larger models (70B+) but sufficient for many reasoning tasks. Prompt-based chain-of-thought is more transparent than implicit reasoning but less efficient than specialized reasoning architectures.

via “natural-language-reasoning-with-chain-of-thought”

As a 30B-class SOTA model, GLM-4.7-Flash offers a new option that balances performance and efficiency. It is further optimized for agentic coding use cases, strengthening coding capabilities, long-horizon task planning,...

Unique: 30B-class model with explicit optimization for long-horizon reasoning tasks, enabling effective chain-of-thought reasoning without the token overhead of much larger models — balances reasoning depth with efficiency

vs others: More efficient than 70B+ models for chain-of-thought tasks while maintaining reasoning quality; more transparent than smaller models that may skip reasoning steps

via “extended-reasoning-chain-of-thought-generation”

The latest and strongest model family from OpenAI, o1 is designed to spend more time thinking before responding. The o1 model series is trained with large-scale reinforcement learning to reason...

Unique: Uses large-scale reinforcement learning (not just supervised fine-tuning) to train the model to dynamically allocate internal computation time based on problem difficulty, with an opaque but learned reasoning process that explores multiple solution paths before responding. This differs from standard models that apply fixed computation per token.

vs others: Outperforms GPT-4 and Claude on math, coding, and formal reasoning benchmarks by 10-30% due to learned reasoning allocation, but trades latency and cost for accuracy on hard problems.

via “natural language reasoning with chain-of-thought decomposition”

GPT-5 Chat is designed for advanced, natural, multimodal, and context-aware conversations for enterprise applications.

Unique: Extended generation with explicit reasoning tokens allows the model to allocate compute to intermediate steps, improving accuracy on complex reasoning through token-level transparency rather than post-hoc explanation

vs others: Native chain-of-thought generation is more reliable than prompting alternatives to 'explain your reasoning', and provides genuine intermediate steps rather than retrofitted explanations

via “reasoning-and-planning-with-extended-chain-of-thought”

Compared with GLM-4.5, this generation brings several key improvements: Longer context window: The context window has been expanded from 128K to 200K tokens, enabling the model to handle more complex...

Unique: Extended context window enables multi-page chain-of-thought reasoning without truncation, allowing the model to explore multiple reasoning paths, backtrack, and reconsider assumptions within a single generation rather than requiring multiple API calls

vs others: Produces more transparent and verifiable reasoning than models with shorter context windows because it can maintain full reasoning history; enables human-in-the-loop validation of intermediate steps rather than just final answers

via “reasoning and logical inference with chain-of-thought patterns”

Trinity-Large-Preview is a frontier-scale open-weight language model from Arcee, built as a 400B-parameter sparse Mixture-of-Experts with 13B active parameters per token using 4-of-256 expert routing. It excels in creative writing,...

Unique: Instruction-tuned on chain-of-thought datasets enabling explicit reasoning trace generation, with sparse MoE architecture potentially enabling reasoning-specialized experts for improved inference quality, though routing transparency is limited

vs others: Open-weight model allows fine-tuning with domain-specific reasoning patterns unlike proprietary models, and explicit reasoning traces provide auditability compared to black-box inference

via “semantic reasoning and chain-of-thought explanation”

The latest GPT-4 Turbo model with vision capabilities. Vision requests can now use JSON mode and function calling. Training data: up to December 2023.

Unique: Implements learned chain-of-thought patterns from training data rather than using external reasoning frameworks, producing natural language reasoning that mirrors human problem-solving without requiring separate symbolic reasoning engines

vs others: More natural and interpretable reasoning chains than symbolic reasoners, but less formally verifiable; outperforms Claude 3 on mathematical reasoning benchmarks due to larger training dataset on math problems

via “reasoning-chain generation with step-by-step problem decomposition”

DeepSeek-V3 is the latest model from the DeepSeek team, building upon the instruction following and coding abilities of the previous versions. Pre-trained on nearly 15 trillion tokens, the reported evaluations...

Unique: Instruction-tuned on 15 trillion tokens to reliably generate explicit reasoning chains without requiring special prompting techniques, whereas most models require careful chain-of-thought prompt engineering to produce transparent reasoning. Demonstrates stronger reasoning consistency across diverse problem types.

vs others: More reliable reasoning traces than GPT-3.5 and comparable to GPT-4, but with lower latency and cost; however, OpenAI's o1 model provides superior reasoning on complex mathematical and scientific problems through reinforcement learning on reasoning quality