diff --git a/.gitignore b/.gitignore
index 639d0f7f..b312110f 100644
--- a/.gitignore
+++ b/.gitignore
@@ -47,9 +47,7 @@ Thumbs.db
 .vscode/*
 !.vscode/extensions.json
 !.vscode/settings.json
-!.vscode/tasks.json
 !.vscode/launch.json
-!.vscode/debug-converter.js
 *.swp
 *.swo
 
diff --git a/.vscode/launch.json b/.vscode/launch.json
index a2012823..dd946bd2 100644
--- a/.vscode/launch.json
+++ b/.vscode/launch.json
@@ -28,6 +28,19 @@
         "NODE_ENV": "test"
       }
     },
+    {
+      "type": "node",
+      "request": "launch",
+      "name": "Debug Current Test File (AVA)",
+      "skipFiles": ["<node_internals>/**"],
+      "program": "${workspaceFolder}/node_modules/ava/entrypoints/cli.js",
+      "args": ["${file}", "--serial", "--concurrency=1"],
+      "console": "integratedTerminal",
+      "cwd": "${workspaceFolder}",
+      "env": {
+        "NODE_ENV": "test"
+      }
+    },
     {
       "type": "node",
       "request": "launch",
diff --git a/.vscode/settings.json b/.vscode/settings.json
index 67d5c078..2e8a2fff 100644
--- a/.vscode/settings.json
+++ b/.vscode/settings.json
@@ -6,7 +6,7 @@
   "files.insertFinalNewline": true,
   "files.eol": "\n", // LF line endings (matches .editorconfig)
 
-  // ESLint (flat config, neostandard style) is the project linter
+  // ESLint flat config (ESLint 10) is the project linter
   "eslint.useFlatConfig": true,
   "javascript.preferences.quoteStyle": "single",
 
@@ -16,21 +16,22 @@
     "source.fixAll.eslint": "explicit"
   },
 
-  // Markdown Linting (Project Standard - matches .markdownlint.mjs)
-  "markdownlint.config": {
-    "line-length": false, // MD013: Allow long lines (links, tables, code examples)
-    "MD013": false // Deprecated alias for backward compatibility
-  },
+  // Markdown linting follows the project's .markdownlint.mjs / .markdownlint-cli2.mjs,
+  // which the extension auto-discovers — no inline mirror to drift out of sync.
 
-  // TypeScript - Use JSDoc for type checking
+  // TypeScript - JSDoc type checking; pin the editor to the workspace TypeScript
+  // (node_modules) so in-editor checks use the same tsc version as CI.
   "javascript.validate.enable": true,
   "typescript.validate.enable": true,
+  "typescript.tsdk": "node_modules/typescript/lib",
+  "typescript.enablePromptUseWorkspaceTsdk": true,
 
   // Project Build Artifacts & Performance
   "search.exclude": {
     "**/node_modules": true,
     "**/coverage": true,
     "**/dist": true,
+    "**/*.d.ts": true,
     "**/.nyc_output": true,
     "**/package-lock.json": true,
     "**/.claude": true,
diff --git a/src/tsconfig.json b/src/tsconfig.json
new file mode 100644
index 00000000..33b8bbb2
--- /dev/null
+++ b/src/tsconfig.json
@@ -0,0 +1,14 @@
+{
+  // Editor-only: type-checks all of src/ with checkJs in VS Code, matching what
+  // CI enforces (tsconfig.build.json checks src/**/*.js with checkJs). The
+  // include below is recursive (**/*.js) on purpose — all of src/ is meant to be
+  // checkJs-clean, so any new file or subdir is checked here AND gated by CI.
+  // The root tsconfig.json keeps checkJs off and covers test/scripts/bench,
+  // which CI does not type-check — so without this file the editor would either
+  // miss src/ errors or flood those dirs with phantom ones. CI does not use this.
+  "extends": "../tsconfig.json",
+  "compilerOptions": {
+    "checkJs": true
+  },
+  "include": ["**/*.js"]
+}
diff --git a/tsconfig.build.json b/tsconfig.build.json
index ca07c35b..88ab5831 100644
--- a/tsconfig.build.json
+++ b/tsconfig.build.json
@@ -9,6 +9,6 @@
     "outDir": ".",
     "rootDir": "."
   },
-  "include": ["src/*.js", "src/utils/*.js"],
+  "include": ["src/**/*.js"],
   "exclude": ["node_modules", "dist", "test", "bench", "scripts"]
 }
diff --git a/tsconfig.json b/tsconfig.json
index c4b1a987..e427356e 100644
--- a/tsconfig.json
+++ b/tsconfig.json
@@ -17,8 +17,10 @@
 
     "types": ["node"]
   },
+  // src/ is type-checked by src/tsconfig.json (checkJs) to match CI; this root
+  // config covers the rest for editor IntelliSense without checkJs (CI does not
+  // type-check test/scripts/bench, so flagging them in-editor would be phantom).
   "include": [
-    "src/**/*.js",
     "test/**/*.js",
     "scripts/**/*.js",
     "bench/**/*.js"