Cursor/Claude debug‑agent demo

A developer posted a demo showing Cursor running a Claude-powered “/debug-agent” loop that adds logs, reproduces a bug, and then tries to patch it. (cursor.com) Cursor said its Debug Mode shipped on December 10, 2025 as part of Cursor 2.2. The company described it as an agent workflow built around runtime information and human verification, not a one-shot code rewrite. (cursor.com) In Cursor’s description, the agent starts by reading the codebase and generating multiple hypotheses about the bug. It then instruments the code with logging statements so the developer can reproduce the issue while the agent collects runtime data. (cursor.com) After that reproduction step, Cursor said the agent uses the logs to identify the root cause and propose a targeted fix. The workflow ends with the developer testing the patched version again and marking whether the bug is actually fixed. (cursor.com) That sequence turns debugging into a repeatable loop: describe the bug, reproduce it, inspect what happened, and verify the fix. Cursor’s documentation says the feature is meant to “find root causes and fix tricky bugs” with hypothesis generation, log instrumentation, and runtime analysis. (cursor.com) The demo matters because it shows coding agents moving beyond autocomplete and code generation into runtime debugging, where the hard part is often observing a failure rather than writing syntax. Cursor’s blog says some bugs “consistently stump” coding agents when they work from source code alone. (cursor.com) Cursor also says the agent removes the added instrumentation after a fix is verified, leaving a smaller final patch. In the company’s example, the result can be a two- or three-line change instead of a larger speculative rewrite. (cursor.com) The idea had been circulating in Cursor’s community before the release. In an August 12, 2025 feature request, a user asked for agent access to debugger-style runtime information, arguing that understanding program behavior from code alone is “really hard” in larger systems. (forum.cursor.com) Cursor framed the release as a response to that gap. Its December 10, 2025 release notes said Debug Mode “instruments your app with runtime logs” to help reproduce and fix bugs across stacks, languages, and models. (forum.cursor.com) The social post put that product idea into a short, watchable workflow: the agent logs first, reproduces second, and edits last. That is a narrower claim than fully autonomous debugging, but it is the one Cursor itself has documented and shipped. (cursor.com)