Cursor’s Debug Mode introduces an agent loop that uses runtime information and human verification to tackle bugs that routine model-only approaches struggle with.
Overview
Debug Mode is presented as an interactive, human-in-the-loop debugging workflow. Rather than attempting an immediate code rewrite, the agent performs a measured investigation: it reads the codebase, forms multiple hypotheses, instruments code with logging, and relies on reproduced runtime data to guide fixes. The workflow is structured around three core phases: describe, reproduce, and verify.
Describe the bug
From a dropdown selection, the developer chooses Debug Mode and provides a detailed description of the issue. The agent inspects the repository and generates multiple hypotheses about potential causes — some conventional, others less obvious. This hypothesis-driven approach steers the next step toward targeted data collection instead of speculative edits.
Instrument & reproduce
The agent inserts logging statements designed to test the hypotheses. During bug reproduction, the agent collects runtime logs capturing variable states, execution paths, and timing information. Those logs give concrete visibility into what actually occurs during the failure, allowing the agent to isolate the root cause with more confidence than static analysis alone.
Targeted fix & verification
With runtime data in hand, the agent proposes a focused fix — often a minimal change such as a two- or three-line modification rather than a broad speculative rewrite. The developer then reproduces the issue with the proposed fix in place. If the bug is resolved, the agent removes the instrumentation, leaving a clean change ready to ship. If the problem persists or the fix doesn’t feel correct, the agent adds more logging and iterates on hypotheses until the issue is addressed.
Why this matters for developers
The emphasis on instrumentation-driven diagnosis and human confirmation shifts the agent from a generator of best-effort patches to a diagnostic partner that collects evidence and narrows fixes. The human-in-the-loop step preserves judgment where fixes have behavioral or UX implications, while the agent handles repetitive instrumentation and log analysis.
Documentation for Debug Mode is available in the Debug Mode docs: https://cursor.com/docs/agent/modes#debug.
Original source: Debug Mode Overview