[FEATURE] No way to enable break-on-exception — uncaught exceptions terminate instead of pausing

[debugmcpdev]

🚀 Feature Request

While validating #214 end-to-end we found that an uncaught exception in a Python debuggee terminates the session rather than pausing at the crash site: debugpy only breaks on exceptions when the client sends setExceptionBreakpoints with filters ('uncaught'/'raised'), and mcp-debugger never sends it for top-level sessions (only the js-debug child-session bootstrap does, with empty filters). There is also no MCP tool through which an agent could enable it.

Why it matters

Combined with #214's lastStop (now exposing reason: 'exception' when a stop occurs), break-on-uncaught is the missing half of crash diagnosis: pausing at the crash site with the traceback frame live is exactly the agent workflow — inspect locals at the point of failure instead of re-running with print statements.

Proposal

• Either a dedicated tool (set_exception_breakpoints with a filters array validated against the adapter's exceptionBreakpointFilters capability), or an option on start_debugging (e.g. breakOnUncaught: true).
• Consider defaulting uncaught on for Python launch sessions: for an agent-driven debugger, pausing at a crash is almost always more useful than losing the session — and after Stop reason (breakpoint vs. exception) is discarded after the first stop — no way to detect a crash #214 the pause is clearly labeled reason: 'exception'.
• The python adapter already validates filters in sendDapRequest('setExceptionBreakpoints', ...); the plumbing exists, only the tool surface is missing.

Repro

Set a breakpoint, start_debugging, continue_execution past a ZeroDivisionError: the session goes straight to state: 'stopped' — indistinguishable from a clean exit (no exit code is surfaced either).

[debugmcpdev]

Prioritizing this as the single highest-value tool-surface gap for agentic debugging: an agent investigating a crash needs the session to pause at the uncaught exception (with stack + locals intact), not terminate. DAP's setExceptionBreakpoints is broadly supported (debugpy, js-debug, Delve, CodeLLDB, JDI, netcoredbg), so the shape is likely a breakOnExceptions: "uncaught" | "all" | "none" option on create_debug_session/start_debugging plus surfacing the exception stop reason and exception details. Related roadmap: #235 (logpoints), #236 (breakpoint management), #237 (redaction), #238 (restart).