This paper introduce Context Language Models (CLMs), a novel approach that enables language models to natively manage their own context by treating it as an editable file rather than relying on traditional append-only histories or external harnesses. By granting models unrestricted read and write access to their context, CLMs achieve superior performance and greater efficiency across long-horizon coding, deep research, and open discovery tasks. The literature demonstrates that these models can be further enhanced through in-context learning, natural-language steering, and online reinforcement learning with success-gated efficiency rewards. To address the computational challenges of frequent context edits, the authors propose Suffix Cache Reuse (SCR), an advanced serving optimization that reuses cached states for surviving suffix tokens to significantly reduce server-side compute. Ultimately, this paradigm shift from external harness control to intrinsic model behavior unlocks more adaptive, creative, and resource-efficient context-management strategies.