Add nvim debugging for python

config/nvim/README.md

@@ -72,6 +72,16 @@ LSP buffer keymaps (set on `LspAttach`, see `plugins/lsp.lua`):
 - `rn` — rename
 - `ff` (visual) — format selection
 
+### Debugging (`plugins/dap.lua`)
+
+- **[nvim-dap](https://github.com/mfussenegger/nvim-dap)** — Debug Adapter Protocol client
+  - `<leader>db` — toggle breakpoint
+  - `<leader>dc` — continue / start debugging
+  - `<leader>di` / `<leader>do` / `<leader>dO` — step into / over / out
+  - `<leader>dr` — toggle REPL
+  - `<leader>dq` — terminate session
+- **[nvim-dap-python](https://github.com/mfussenegger/nvim-dap-python)** — configures nvim-dap for Python using `debugpy`. Requires `:MasonInstall debugpy`; without it, debugging is skipped with a warning.
+
 ### Formatting & linting (`plugins/format.lua`)
 
 - **[conform.nvim](https://github.com/stevearc/conform.nvim)** — format-on-save (prettier, ruff_format, rustfmt, stylua per filetype)

config/nvim/lua/plugins/dap.lua

@@ -0,0 +1,33 @@
+return {
+  {
+    "mfussenegger/nvim-dap",
+    keys = {
+      { "<leader>db", function() require("dap").toggle_breakpoint() end, desc = "Toggle breakpoint" },
+      { "<leader>dc", function() require("dap").continue() end, desc = "Debug: continue" },
+      { "<leader>di", function() require("dap").step_into() end, desc = "Debug: step into" },
+      { "<leader>do", function() require("dap").step_over() end, desc = "Debug: step over" },
+      { "<leader>dO", function() require("dap").step_out() end, desc = "Debug: step out" },
+      { "<leader>dr", function() require("dap").repl.toggle() end, desc = "Debug: toggle REPL" },
+      { "<leader>dq", function() require("dap").terminate() end, desc = "Debug: terminate" },
+    },
+  },
+  {
+    -- Configures nvim-dap for Python using debugpy, installed via Mason
+    -- (:MasonInstall debugpy) so it lives in an isolated venv rather than
+    -- needing debugpy in every project's own environment.
+    "mfussenegger/nvim-dap-python",
+    dependencies = { "mfussenegger/nvim-dap" },
+    ft = "python",
+    config = function()
+      local python = vim.fn.stdpath("data") .. "/mason/packages/debugpy/venv/bin/python"
+      if vim.fn.executable(python) == 0 then
+        vim.notify(
+          "debugpy not installed: run :MasonInstall debugpy to enable Python debugging",
+          vim.log.levels.WARN
+        )
+        return
+      end
+      require("dap-python").setup(python)
+    end,
+  },
+}