Understanding the inter-relations and interactions between tasks is crucial for multitask dense prediction. Existing methods predominantly utilize convolutional layers and attention mechanisms to explore task-level interactions. In this work, we introduce a novel decoder-based framework, parameter-aware Mamba model (PAMM), specifically designed for dense prediction in multitask learning (MTL) setting. Distinct from approaches that employ Transformers to model holistic task relationships, PAMM leverages the rich, scalable parameters of state-space models (SSMs) to enhance task interconnectivity. It features dual state-space parameter experts (PEs) that integrate and set task-specific parameter priors (PPs), capturing the intrinsic properties of each task. This approach not only facilitates precise multitask interactions but also allows for the global integration of task priors through the structured state-space sequence (S4) model. Furthermore, we employ the multidirectional Hilbert scanning (MDHS) method to construct multiangle feature sequences, thereby enhancing the sequence model's perceptual capabilities for 2-D data. Extensive experiments on the NYUD-v2 and PASCAL-Context benchmarks demonstrate the effectiveness of our proposed method. Our code is available at https://github.com/CQC-gogopro/PAMM.

Multi-task dense prediction improves pixel-level performance by leveraging shared representations and inter-task collaboration. However, existing approaches either rely on implicit task relationships or neglect frequency-domain cues that are essential for preserving fine-grained details and enhancing cross-task feature learning at multiple scales. As a result, they face persistent challenges in multi-scale feature fusion, effective task interaction, and accurate decoding. To address these issues, we propose a hierarchical frequency-driven framework, termed Hierarchical Frequency-Adaptive Network (HiFAN), that facilitates cross-task collaborative optimization via frequency-domain analysis. Specifically, we first design a task-adaptive fusion module that exploits multi-scale frequency-domain information to enhance spatial details. This module generates dynamic convolutional kernels with task-specific parameters and positional biases to adaptively accommodate diverse task requirements. Next, we introduce an efficient cross-task interaction module that leverages compact low-frequency representations to enable global context exchange across tasks. Finally, we present a high-frequency-aware decoder that mitigates feature smoothing and detail loss commonly introduced by Transformer-based decoders. We demonstrate the effectiveness of HiFAN on two standard multi-task learning benchmarks, PASCAL-Context and NYUD-v2, achieving strong and competitive performance across multiple tasks. The code and model weights are available in HiFAN.