While recent advances in reasoning models have demonstrated cognitive behaviors through reinforcement learning, existing approaches struggle to invoke deep reasoning capabilities in multi-turn agents with long-horizon interactions. We propose DeepMiner, a framework that elicits such abilities in deep search agents by introducing a dynamic context window and challenging training tasks. We design a dynamic context management strategy that utilizes a sliding window to selectively drop distant tool responses while preserving all assistant reasoning traces, eliminating the dependency on external summarization models. To provide training tasks that genuinely demand long-horizon reasoning, DeepMiner further employs a reverse construction method to generate complex yet verifiable question-answer pairs from authentic web sources, ensuring both difficulty and reliability. Through reinforcement learning on Qwen3-32B, we develop DeepMiner-32B, which achieves substantial performance improvements across multiple search agent benchmarks. DeepMiner attains 33.5% accuracy on BrowseComp-en, surpassing the much larger DeepSeek-V3.1-671B, and demonstrates consistent improvements on BrowseComp-zh, XBench-DS, and GAIA. Notably, our dynamic context management enables sustained interactions of nearly 100 turns within commonly used 32k context length, effectively addressing the context limitations that constrain existing multi-turn agents.

Generative Reward Models (GenRMs) and LLM-as-a-Judge exhibit deceptive alignment by producing correct judgments for incorrect reasons, as they are trained and evaluated to prioritize Outcome Accuracy, which undermines their ability to generalize during RLHF. We introduce Rationale Consistency, a fine-grained metric that quantifies the alignment between the model’s reasoning process and human judgment. Our evaluation of frontier models reveals that rationale consistency effectively discriminates among state-of-the-art models and detects deceptive alignment, while outcome accuracy falls short in both respects. To mitigate this gap, we introduce a hybrid signal that combines rationale consistency with outcome accuracy for GenRM training. Our training method achieves state-of-the-art performance on RM-Bench (87.1%) and JudgeBench (82%), surpassing outcome-only baselines by an average of 5%. Using RM during RLHF, our method effectively improves performance as demonstrated on Arena Hard v2, notably yielding a 7% improvement in creative writing tasks. Further analysis confirms that our method escapes the deceptive alignment trap, effectively reversing the decline in rationale consistency observed in outcome-only training.