diff --git a/MIGRATION_BASELINE.md b/MIGRATION_BASELINE.md
new file mode 100644
index 0000000..79bbb1e
--- /dev/null
+++ b/MIGRATION_BASELINE.md
@@ -0,0 +1,141 @@
+# TypeScript migration — baseline
+
+The state of this repository **immediately before** the first source file was
+renamed, measured rather than assumed. Everything the migration does is checked
+against these numbers; a figure that moves without a phase claiming it is a
+regression.
+
+Measured on 2026-09-11, on `main` with a clean tree, before any change in
+Milestone 1.
+
+## The numbers
+
+| Check | Command | Baseline |
+|---|---|---|
+| Types | `npm run typecheck` | **FAILS — 71 errors across 27 files** |
+| Lint | `npm run lint` | **PASSES**, exit 0 |
+| Lint (with warnings) | `npx eslint .` | 289 problems — 0 errors, 289 warnings |
+| Files linted | `npx eslint . --format json` | 302 |
+| Behaviour | `npm test` | **1641 / 1642 checks passed** |
+| Build | `npm run build` | succeeds |
+| Owliver, via the suite | `npm test` section 21 | **all green** — schema, skills, routes, and per-context skills, suggestions, prompts and intent routing |
+| Owliver, standalone | `node scripts/owliver-baseline.mjs` | **FAILS — pre-existing, see below** |
+
+### The 71 type errors, by code
+
+| Code | Count | What it is |
+|---|---|---|
+| TS2339 | 38 | Property does not exist on an inferred type |
+| TS2741 | 9 | Missing required prop in JSX |
+| TS2353 | 9 | Unknown property in an object literal |
+| TS2345 | 6 | Argument type mismatch |
+| TS2554 | 2 | Wrong argument count |
+| TS2362 / TS2363 | 4 | Arithmetic on a non-number |
+| TS2739 / TS2559 / TS2349 | 3 | Missing props / no common props / not callable |
+
+These are **pre-existing**. They were not introduced by the migration and the
+migration is not obliged to fix them; they are the backlog it has to avoid
+adding to. Six of them are `import.meta` errors that Phase 1 resolves as a side
+effect of configuring `vite/client`.
+
+Note that `npm run typecheck` **is not run by CI** (`.github/workflows/ci.yml`
+runs lint, test, build and the seed check). That is how 71 errors accumulated
+without anyone seeing them. Wiring it in is the last phase of the migration, not
+the first — it cannot be a gate until it is green.
+
+## The standalone Owliver script is already broken
+
+`node scripts/owliver-baseline.mjs` fails before any of this began — verified by
+stashing every change and running it on a clean `main`, where it fails
+identically. It is **not** caused by the migration.
+
+```
+Failed to scan for dependencies from entries:
+  index.html
+  scripts/__baseline__/activity-page.pre-migration.html
+  … the other seven snapshots …
+  ✘ [ERROR] The server is being restarted or closed. Request is outdated [plugin vite:dep-scan]
+Owliver behaviour has DRIFTED from the baseline.
+```
+
+Two things are going on, and neither is a real drift. Vite's dependency scanner
+treats every `*.html` under the project root as an entry point, so the eight
+captured SSR snapshots in `scripts/__baseline__/` are scanned as if they were
+pages of the app. The script then calls `server.close()` as soon as
+`captureBaseline` returns, while that scan is still running, and the scan
+reports that it was cancelled. The capture comes back incomplete and the
+comparison calls it drift.
+
+**The coverage itself is not lost.** `skill-check.mjs` imports the same
+`captureBaseline` and the same `BASELINE_PATH` and asserts against them in
+section 21, and it does enough other work afterwards that the scan finishes. Run
+`npm test` and the whole section is green:
+
+```
+── Owliver behaviour baseline ──
+[  ok  ] baseline schema matches — expected 1, got 1
+[  ok  ] every skill that existed before the agent layer still registers — 23 kept, 1 added since
+[  ok  ] every route that resolved before resolves the same way — 18 unchanged
+[  ok  ] controlCenter: keeps every skill it had — 7 skill(s), unchanged
+…per context: page key, skills, suggestions, prompts, intent routing
+```
+
+So **`npm test` is the Owliver drift check for the duration of the migration**,
+and the standalone script is a convenience wrapper that needs repairing on its
+own terms — excluding `scripts/__baseline__` from the scan, or awaiting the
+optimizer before closing. That repair is not part of the migration: it changes
+a script's behaviour, and this milestone's whole claim is that it changed none.
+
+## The one failing check
+
+```
+1641/1642 checks passed
+
+Failed:
+  - the backend fixture is in step with this seed (stale — run `npm run seed:fixture`)
+```
+
+`scripts/__baseline__` is intact and `owliver-baseline.mjs` matches; this is not
+an Owliver failure. `seed/fixtures/seed.json` in the sibling `krow-backend`
+checkout has drifted from `src/api/seed.js`.
+
+**This failure predates the migration and is unrelated to it. It is recorded
+here so that it is never mistaken for something the migration caused, and it is
+deliberately left alone** — regenerating the fixture would write into another
+repository and change what the backend seeds, which is a product change wearing
+a migration's clothes. Fix it separately, on its own terms.
+
+## What "unchanged" means for the Owliver / agent flow
+
+The agent flow is ~112 files and 38% of the codebase, and it is converted last,
+by rename and type annotation only. The evidence that it still behaves
+identically is already in the repository and needs nothing new:
+
+- `npm test` — 1642 checks covering skill discovery, routing, context
+  resolution and SSR-rendered markup.
+- `scripts/__baseline__/owliver-baseline.json` — contexts, skill ids and routes.
+- `scripts/__baseline__/*.pre-migration.html` — eight pages of byte-level SSR
+  output.
+- `node scripts/owliver-baseline.mjs` — the drift check.
+- CI's `FLOOR = 900` — fails if the suite silently shrinks.
+
+**These artifacts are read-only for the duration of the migration.** If the
+baseline drifts, revert the change. Regenerating it to clear a red check records
+the regression instead of catching it, which is worse than having no baseline —
+`owliver-baseline.mjs` says as much in its own header.
+
+`src/agents/**/*.md` and `src/skills/**/*.md` are likewise untouched throughout:
+they are the definitions the flow is built from, not code being migrated.
+
+## How to re-measure
+
+```bash
+npm run typecheck; echo "exit=$?"
+npm run typecheck 2>&1 | grep -c "error TS"
+npm run lint; echo "exit=$?"
+npx eslint . --format json | python3 -c "import json,sys;print(len(json.load(sys.stdin)))"
+npm test
+node scripts/owliver-baseline.mjs
+npm run build
+git diff --stat -M
+```
diff --git a/eslint.config.js b/eslint.config.js
index 4daa2f5..5cd9415 100644
--- a/eslint.config.js
+++ b/eslint.config.js
@@ -3,16 +3,68 @@ import pluginJs from "@eslint/js";
 import pluginReact from "eslint-plugin-react";
 import pluginReactHooks from "eslint-plugin-react-hooks";
 import pluginUnusedImports from "eslint-plugin-unused-imports";
+import tseslint from "typescript-eslint";
+
+/**
+ * The rule set, written once and applied to JavaScript and TypeScript alike.
+ *
+ * Shared rather than duplicated because the two blocks below differ in exactly
+ * one thing — which parser reads the file — and a rule that applied to `.jsx`
+ * but not to its `.tsx` successor would make the TypeScript migration look like
+ * it was tidying the code up. It is not; it renames files and adds types.
+ */
+const rules = {
+  "no-unused-vars": "off",
+  "react/jsx-uses-vars": "error",
+  "react/jsx-uses-react": "error",
+  "unused-imports/no-unused-imports": "error",
+  "unused-imports/no-unused-vars": [
+    "warn",
+    {
+      vars: "all",
+      varsIgnorePattern: "^_",
+      args: "after-used",
+      argsIgnorePattern: "^_",
+    },
+  ],
+  "react/prop-types": "off",
+  "react/react-in-jsx-scope": "off",
+  "react/no-unknown-property": [
+    "error",
+    { ignore: ["cmdk-input-wrapper", "toast-close"] },
+  ],
+  "react-hooks/rules-of-hooks": "error",
+};
+
+const plugins = {
+  react: pluginReact,
+  "react-hooks": pluginReactHooks,
+  "unused-imports": pluginUnusedImports,
+};
+
+const settings = { react: { version: "detect" } };
+
+/**
+ * Which files are linted.
+ *
+ * Unchanged from what this config has always covered — `src/lib` and
+ * `src/components/ui` stay out of it — with `ts` and `tsx` added to every
+ * pattern. That addition is the point: ESLint matches on extension, so the
+ * moment a `.jsx` file became `.tsx` it would have dropped out of the run
+ * silently, and `eslint .` would have gone on exiting 0 while linting less and
+ * less of the codebase. A lint that passes because it checked nothing is worse
+ * than one that fails.
+ */
+const directories = ["src/components", "src/pages", "src/layouts", "src/hooks"];
+const ignores = ["src/lib/**/*", "src/components/ui/**/*"];
+
+const filesWith = (extensions) =>
+  directories.map((directory) => `${directory}/**/*.{${extensions}}`);
 
 export default [
   {
-    files: [
-      "src/components/**/*.{js,mjs,cjs,jsx}",
-      "src/pages/**/*.{js,mjs,cjs,jsx}",
-      "src/layouts/**/*.{js,mjs,cjs,jsx}",
-      "src/hooks/**/*.{js,mjs,cjs,jsx}",
-    ],
-    ignores: ["src/lib/**/*", "src/components/ui/**/*"],
+    files: filesWith("js,mjs,cjs,jsx"),
+    ignores,
     ...pluginJs.configs.recommended,
     ...pluginReact.configs.flat.recommended,
     languageOptions: {
@@ -20,42 +72,50 @@ export default [
       parserOptions: {
         ecmaVersion: 2022,
         sourceType: "module",
-        ecmaFeatures: {
-          jsx: true,
-        },
+        ecmaFeatures: { jsx: true },
       },
     },
-    settings: {
-      react: {
-        version: "detect",
+    settings,
+    plugins,
+    rules,
+  },
+
+  /**
+   * The same block for TypeScript, with the TypeScript parser.
+   *
+   * A separate block rather than one widened glob, so that nothing about how
+   * the existing JavaScript is parsed or reported changes on the day this
+   * lands. `typescript-eslint`'s parser accepts plain JavaScript too, and
+   * merging the two would have been shorter — but it would also have quietly
+   * re-parsed 200-odd existing files, and this phase is meant to be provably
+   * inert.
+   *
+   * Deliberately NOT type-aware (no `projectService`): type errors are
+   * `npm run typecheck`'s job, and asking ESLint to build a program as well
+   * would make every lint run pay for it twice.
+   */
+  {
+    files: filesWith("ts,tsx,mts,cts"),
+    ignores,
+    ...pluginReact.configs.flat.recommended,
+    languageOptions: {
+      globals: globals.browser,
+      parser: tseslint.parser,
+      parserOptions: {
+        ecmaVersion: 2022,
+        sourceType: "module",
+        ecmaFeatures: { jsx: true },
       },
     },
-    plugins: {
-      react: pluginReact,
-      "react-hooks": pluginReactHooks,
-      "unused-imports": pluginUnusedImports,
-    },
+    settings,
+    plugins: { ...plugins, "@typescript-eslint": tseslint.plugin },
     rules: {
-      "no-unused-vars": "off",
-      "react/jsx-uses-vars": "error",
-      "react/jsx-uses-react": "error",
-      "unused-imports/no-unused-imports": "error",
-      "unused-imports/no-unused-vars": [
-        "warn",
-        {
-          vars: "all",
-          varsIgnorePattern: "^_",
-          args: "after-used",
-          argsIgnorePattern: "^_",
-        },
-      ],
-      "react/prop-types": "off",
-      "react/react-in-jsx-scope": "off",
-      "react/no-unknown-property": [
-        "error",
-        { ignore: ["cmdk-input-wrapper", "toast-close"] },
-      ],
-      "react-hooks/rules-of-hooks": "error",
+      ...rules,
+      /* TypeScript resolves identifiers itself and reports the ones it cannot,
+         with better messages and without ESLint's browser/node globals list
+         needing to be right. Leaving the core rule on would report every `type`
+         and `interface` name as undefined. */
+      "no-undef": "off",
     },
   },
 ];
diff --git a/package-lock.json b/package-lock.json
index fb6ded6..55277bf 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -57,6 +57,7 @@
         "puppeteer-core": "^23.11.1",
         "tailwindcss": "^3.4.17",
         "typescript": "^5.8.2",
+        "typescript-eslint": "^8.70.0",
         "vite": "^6.1.0"
       }
     },
@@ -3378,6 +3379,301 @@
         "@types/node": "*"
       }
     },
+    "node_modules/@typescript-eslint/eslint-plugin": {
+      "version": "8.70.0",
+      "resolved": "https://registry.npmjs.org/@typescript-eslint/eslint-plugin/-/eslint-plugin-8.70.0.tgz",
+      "integrity": "sha512-/v8HZt6RlyIZxB3ntehELOcUcfxKPVGWXnQdJuHRmzrqgF8nQypcC/oxGW+Ot4VGKDq81XugPKxx0n5PBtf9PA==",
+      "dev": true,
+      "license": "MIT",
+      "dependencies": {
+        "@eslint-community/regexpp": "^4.12.2",
+        "@typescript-eslint/scope-manager": "8.70.0",
+        "@typescript-eslint/type-utils": "8.70.0",
+        "@typescript-eslint/utils": "8.70.0",
+        "@typescript-eslint/visitor-keys": "8.70.0",
+        "ignore": "^7.0.5",
+        "natural-compare": "^1.4.0",
+        "ts-api-utils": "^2.5.0"
+      },
+      "engines": {
+        "node": "^18.18.0 || ^20.9.0 || >=21.1.0"
+      },
+      "funding": {
+        "type": "opencollective",
+        "url": "https://opencollective.com/typescript-eslint"
+      },
+      "peerDependencies": {
+        "@typescript-eslint/parser": "^8.70.0",
+        "eslint": "^8.57.0 || ^9.0.0 || ^10.0.0",
+        "typescript": ">=4.8.4 <6.1.0"
+      }
+    },
+    "node_modules/@typescript-eslint/eslint-plugin/node_modules/ignore": {
+      "version": "7.0.9",
+      "resolved": "https://registry.npmjs.org/ignore/-/ignore-7.0.9.tgz",
+      "integrity": "sha512-brTTsvFRt5C1gGHtPst/281UjPD5t9fBqbgoMPlVWy11ZLTPfu7HxK4ZYqO9H7o/yC9rSTCI85EaQ4OoY12qYw==",
+      "dev": true,
+      "license": "MIT",
+      "engines": {
+        "node": ">= 4"
+      }
+    },
+    "node_modules/@typescript-eslint/parser": {
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+        "@typescript-eslint/visitor-keys": "8.70.0",
+        "debug": "^4.4.3"
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+        "url": "https://opencollective.com/typescript-eslint"
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+        "minimatch": "^10.2.2",
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+      "version": "10.2.6",
+      "resolved": "https://registry.npmjs.org/minimatch/-/minimatch-10.2.6.tgz",
+      "integrity": "sha512-vpLQEs+VLCr1nU0BXS07maYoFwlDAH0gngQuuttxIwutDFEMHq2blX+8vpgxDdK3J1PwjCJiep77OitTZ4Ll1A==",
+      "dev": true,
+      "license": "BlueOak-1.0.0",
+      "dependencies": {
+        "brace-expansion": "^5.0.8"
+      },
+      "engines": {
+        "node": "18 || 20 || >=22"
+      },
+      "funding": {
+        "url": "https://github.com/sponsors/isaacs"
+      }
+    },
+    "node_modules/@typescript-eslint/typescript-estree/node_modules/semver": {
+      "version": "7.8.5",
+      "resolved": "https://registry.npmjs.org/semver/-/semver-7.8.5.tgz",
+      "integrity": "sha512-Y7/KDsb8LjooZpwaqGyulO6DQlksgCncchHGk+sZIY4SBvUocMBEFH5Ur1fI4dV+Jvl0w6cjvucaIi40puRioA==",
+      "dev": true,
+      "license": "ISC",
+      "bin": {
+        "semver": "bin/semver.js"
+      },
+      "engines": {
+        "node": ">=10"
+      }
+    },
+    "node_modules/@typescript-eslint/utils": {
+      "version": "8.70.0",
+      "resolved": "https://registry.npmjs.org/@typescript-eslint/utils/-/utils-8.70.0.tgz",
+      "integrity": "sha512-oZmtKJz/4fufZ2p3+Cn3ijEojcdfR+1zYDH2xKYrEly0dR/Q/1xUPRCOlKGxod78nWlU2UnDe09GZ3TaknBFGA==",
+      "dev": true,
+      "license": "MIT",
+      "dependencies": {
+        "@eslint-community/eslint-utils": "^4.9.1",
+        "@typescript-eslint/scope-manager": "8.70.0",
+        "@typescript-eslint/types": "8.70.0",
+        "@typescript-eslint/typescript-estree": "8.70.0"
+      },
+      "engines": {
+        "node": "^18.18.0 || ^20.9.0 || >=21.1.0"
+      },
+      "funding": {
+        "type": "opencollective",
+        "url": "https://opencollective.com/typescript-eslint"
+      },
+      "peerDependencies": {
+        "eslint": "^8.57.0 || ^9.0.0 || ^10.0.0",
+        "typescript": ">=4.8.4 <6.1.0"
+      }
+    },
+    "node_modules/@typescript-eslint/visitor-keys": {
+      "version": "8.70.0",
+      "resolved": "https://registry.npmjs.org/@typescript-eslint/visitor-keys/-/visitor-keys-8.70.0.tgz",
+      "integrity": "sha512-BoC8PiO4Hkdo0TVJh9Ntxr5MxPDI7/oFsrygN5ADelFSeXG/qgNuucIGA+L5Z6JpPTE/uRfcTWtscjbUaufepQ==",
+      "dev": true,
+      "license": "MIT",
+      "dependencies": {
+        "@typescript-eslint/types": "8.70.0",
+        "eslint-visitor-keys": "^5.0.0"
+      },
+      "engines": {
+        "node": "^18.18.0 || ^20.9.0 || >=21.1.0"
+      },
+      "funding": {
+        "type": "opencollective",
+        "url": "https://opencollective.com/typescript-eslint"
+      }
+    },
+    "node_modules/@typescript-eslint/visitor-keys/node_modules/eslint-visitor-keys": {
+      "version": "5.0.1",
+      "resolved": "https://registry.npmjs.org/eslint-visitor-keys/-/eslint-visitor-keys-5.0.1.tgz",
+      "integrity": "sha512-tD40eHxA35h0PEIZNeIjkHoDR4YjjJp34biM0mDvplBe//mB+IHCqHDGV7pxF+7MklTvighcCPPZC7ynWyjdTA==",
+      "dev": true,
+      "license": "Apache-2.0",
+      "engines": {
+        "node": "^20.19.0 || ^22.13.0 || >=24"
+      },
+      "funding": {
+        "url": "https://opencollective.com/eslint"
+      }
+    },
     "node_modules/@ungap/structured-clone": {
       "version": "1.3.3",
       "resolved": "https://registry.npmjs.org/@ungap/structured-clone/-/structured-clone-1.3.3.tgz",
@@ -9650,6 +9946,19 @@
         "url": "https://github.com/sponsors/wooorm"
       }
     },
+    "node_modules/ts-api-utils": {
+      "version": "2.5.0",
+      "resolved": "https://registry.npmjs.org/ts-api-utils/-/ts-api-utils-2.5.0.tgz",
+      "integrity": "sha512-OJ/ibxhPlqrMM0UiNHJ/0CKQkoKF243/AEmplt3qpRgkW8VG7IfOS41h7V8TjITqdByHzrjcS/2si+y4lIh8NA==",
+      "dev": true,
+      "license": "MIT",
+      "engines": {
+        "node": ">=18.12"
+      },
+      "peerDependencies": {
+        "typescript": ">=4.8.4"
+      }
+    },
     "node_modules/ts-interface-checker": {
       "version": "0.1.13",
       "resolved": "https://registry.npmjs.org/ts-interface-checker/-/ts-interface-checker-0.1.13.tgz",
@@ -9774,6 +10083,30 @@
         "node": ">=14.17"
       }
     },
+    "node_modules/typescript-eslint": {
+      "version": "8.70.0",
+      "resolved": "https://registry.npmjs.org/typescript-eslint/-/typescript-eslint-8.70.0.tgz",
+      "integrity": "sha512-P/W5cz70/cQAuKfY3xwQMWWTV7BvJ0mAQmi+9mBcsVPaBUpd6Ohpa+fECv9rBFrQcig86jAiNBFNWUqnTjr4pw==",
+      "dev": true,
+      "license": "MIT",
+      "dependencies": {
+        "@typescript-eslint/eslint-plugin": "8.70.0",
+        "@typescript-eslint/parser": "8.70.0",
+        "@typescript-eslint/typescript-estree": "8.70.0",
+        "@typescript-eslint/utils": "8.70.0"
+      },
+      "engines": {
+        "node": "^18.18.0 || ^20.9.0 || >=21.1.0"
+      },
+      "funding": {
+        "type": "opencollective",
+        "url": "https://opencollective.com/typescript-eslint"
+      },
+      "peerDependencies": {
+        "eslint": "^8.57.0 || ^9.0.0 || ^10.0.0",
+        "typescript": ">=4.8.4 <6.1.0"
+      }
+    },
     "node_modules/unbox-primitive": {
       "version": "1.1.0",
       "resolved": "https://registry.npmjs.org/unbox-primitive/-/unbox-primitive-1.1.0.tgz",
diff --git a/package.json b/package.json
index 790de62..f33a70d 100644
--- a/package.json
+++ b/package.json
@@ -11,7 +11,7 @@
     "test": "node scripts/skill-check.mjs",
     "seed:fixture": "node scripts/seed-fixture.mjs --write",
     "seed:check": "node scripts/seed-fixture.mjs",
-    "typecheck": "tsc -p ./jsconfig.json",
+    "typecheck": "tsc -p ./tsconfig.json",
     "preview": "vite preview",
     "test:browser": "node scripts/browser-check.mjs"
   },
@@ -65,6 +65,7 @@
     "puppeteer-core": "^23.11.1",
     "tailwindcss": "^3.4.17",
     "typescript": "^5.8.2",
+    "typescript-eslint": "^8.70.0",
     "vite": "^6.1.0"
   }
 }
diff --git a/scripts/owliver-baseline.mjs b/scripts/owliver-baseline.mjs
index f3ccc22..0598ed6 100644
--- a/scripts/owliver-baseline.mjs
+++ b/scripts/owliver-baseline.mjs
@@ -16,6 +16,7 @@ import { readFileSync, writeFileSync, existsSync, mkdirSync } from 'node:fs';
 import { dirname } from 'node:path';
 import { createServer } from 'vite';
 import { BASELINE_PATH, captureBaseline } from './owliver-capture.mjs';
+import { withSourceResolution } from './ssr-resolve.mjs';
 
 const ROOT = process.cwd();
 
@@ -26,6 +27,11 @@ const server = await createServer({
   logLevel: 'error',
 });
 
+/* Resolves the capture's module paths whatever extension they carry during the
+   TypeScript migration. The comparison this script performs is unaffected: it
+   loads the same modules and serialises the same values. */
+withSourceResolution(server, ROOT);
+
 const captured = await captureBaseline(server);
 await server.close();
 
diff --git a/scripts/render-page.mjs b/scripts/render-page.mjs
index cc2402d..d2d93e0 100644
--- a/scripts/render-page.mjs
+++ b/scripts/render-page.mjs
@@ -18,6 +18,7 @@ import { join } from 'node:path';
 import { writeFileSync } from 'node:fs';
 import React from 'react';
 import { renderToStaticMarkup } from 'react-dom/server';
+import { withSourceResolution } from './ssr-resolve.mjs';
 
 /**
  * The design system reads `window` when its modules evaluate, which is a
@@ -97,6 +98,9 @@ if (process.argv[1] && process.argv[1].endsWith('render-page.mjs')) {
     logLevel: 'error',
     resolve: { alias: { 'react-hot-toast': join(process.cwd(), 'scripts/stubs/react-hot-toast.js') } },
   });
+  /* The page path arrives on the command line with whatever extension it has
+     today; during the TypeScript migration that may be .jsx or .tsx. */
+  withSourceResolution(server, process.cwd());
   try {
     const html = await renderPage(server, `/${modulePath.replace(/^\//, '')}`, { route: route || '/' });
     writeFileSync(out, html);
diff --git a/scripts/seed-fixture.mjs b/scripts/seed-fixture.mjs
index 141278d..056f12e 100644
--- a/scripts/seed-fixture.mjs
+++ b/scripts/seed-fixture.mjs
@@ -20,6 +20,7 @@ import { createServer } from 'vite';
 import { readFileSync, writeFileSync, existsSync } from 'node:fs';
 import { join } from 'node:path';
 import { pathToFileURL } from 'node:url';
+import { withSourceResolution } from './ssr-resolve.mjs';
 
 export const FIXTURE_PATH = join(process.cwd(), '..', 'krow-backend', 'seed', 'fixtures', 'seed.json');
 
@@ -51,6 +52,9 @@ if (import.meta.url === pathToFileURL(process.argv[1]).href) {
   const server = await createServer({
     root: process.cwd(), server: { middlewareMode: true }, appType: 'custom', logLevel: 'error',
   });
+  /* `buildFixture` loads `/src/api/seed.js`, which the TypeScript migration
+     will rename. The fixture it generates is unchanged either way. */
+  withSourceResolution(server, process.cwd());
   const built = await buildFixture(server);
   await server.close();
 
diff --git a/scripts/skill-check.mjs b/scripts/skill-check.mjs
index b22c70e..53eef2a 100644
--- a/scripts/skill-check.mjs
+++ b/scripts/skill-check.mjs
@@ -19,6 +19,7 @@ import React from 'react';
 import { renderToStaticMarkup } from 'react-dom/server';
 import { BASELINE_PATH, captureBaseline } from './owliver-capture.mjs';
 import { buildFixture, FIXTURE_PATH } from './seed-fixture.mjs';
+import { withSourceResolution } from './ssr-resolve.mjs';
 
 const ROOT = process.cwd();
 const results = [];
@@ -41,6 +42,12 @@ const server = await createServer({
   resolve: { alias: { 'react-hot-toast': join(ROOT, 'scripts/stubs/react-hot-toast.js') } },
 });
 
+/* Every `ssrLoadModule` path below names a file by its current extension. While
+   the TypeScript migration is under way that extension changes underneath them,
+   so the loader resolves .js/.jsx/.ts/.tsx rather than each call site having to
+   know which one a module is on today. The path as written is tried first. */
+withSourceResolution(server, ROOT);
+
 const reg = await server.ssrLoadModule('/src/lib/skills/registry.js');
 const placement = await server.ssrLoadModule('/src/components/ai-assistant/placement.js');
 
diff --git a/scripts/ssr-resolve.mjs b/scripts/ssr-resolve.mjs
new file mode 100644
index 0000000..a065373
--- /dev/null
+++ b/scripts/ssr-resolve.mjs
@@ -0,0 +1,80 @@
+/**
+ * Extension-agnostic SSR module loading, for the duration of the TypeScript
+ * migration.
+ *
+ * Every script in here addresses modules by literal path — `ssrLoadModule(
+ * '/src/lib/skills/registry.js')` — about a hundred and seventy times across
+ * `skill-check.mjs`, `owliver-capture.mjs`, `render-page.mjs` and
+ * `seed-fixture.mjs`. That is fine while every source file is JavaScript and
+ * fatal the moment one is not: renaming `registry.js` to `registry.ts` turns
+ * the check suite's very first load into a failure, and the suite is the only
+ * evidence the Owliver flow still behaves the way it did.
+ *
+ * Rewriting all those call sites would be a large, noisy, error-prone diff
+ * against the file that guards the migration — exactly the wrong thing to
+ * disturb. So the loader is wrapped once instead and the call sites keep the
+ * paths they already have, which stay readable as the names of real files.
+ *
+ * Resolution is by existence on disk, not by catching a failed load. A load
+ * that fails for a real reason — a syntax error, a bad import inside the module
+ * — must surface as itself; retrying under another extension would bury it
+ * behind a second, more confusing error about a file that was never there.
+ *
+ * The path as written is always tried first, so while a module is still
+ * JavaScript this changes nothing at all.
+ *
+ * This file is temporary. When `src` holds no `.js` or `.jsx` any more, the
+ * call sites can be renamed in one pass and this wrapper deleted.
+ */
+import { existsSync } from 'node:fs';
+import { join } from 'node:path';
+
+/**
+ * The candidate paths for one module specifier, in the order they are tried.
+ *
+ * Only `.js` and `.jsx` are rewritten. Anything else — a bare specifier, a
+ * `.mjs` file, something under `/node_modules` — is returned untouched, because
+ * nothing in this migration renames it.
+ *
+ * `.js` is allowed to become `.tsx` as well as `.ts`. Not because any `.js`
+ * file here contains JSX today — none of the 93 does, checked with a parser
+ * rather than a guess — but because one may be renamed that way: the only
+ * `.js` under `src/pages` is `admin/positions/nodes.js`, sitting among seven
+ * sibling `nodes.jsx` files, and whoever converts that directory will
+ * reasonably want all eight to end in `.tsx`. The extra candidate costs one
+ * `existsSync` that answers no.
+ */
+export function candidatesFor(path) {
+  const specifier = String(path);
+  if (!/\.jsx?$/.test(specifier)) return [specifier];
+  const stem = specifier.replace(/\.jsx?$/, '');
+  return [...new Set([specifier, `${stem}.ts`, `${stem}.tsx`])];
+}
+
+/**
+ * Wraps `server.ssrLoadModule` so it finds a module whichever of the four
+ * extensions it currently carries.
+ *
+ * Mutates and returns the server, so it reads as one line after `createServer`
+ * and every later call — including the dynamically-built paths, which is why
+ * this is done here rather than at the call sites — goes through it.
+ *
+ * `root` is where the leading-slash paths are rooted; it defaults to the
+ * process's working directory, which is what every caller here uses.
+ */
+export function withSourceResolution(server, root = process.cwd()) {
+  const load = server.ssrLoadModule.bind(server);
+
+  server.ssrLoadModule = (path, options) => {
+    for (const candidate of candidatesFor(path)) {
+      if (existsSync(join(root, candidate.replace(/^\//, '')))) {
+        return load(candidate, options);
+      }
+    }
+    /* Nothing on disk under any extension. Load the path as written so the
+       error names what the caller actually asked for. */
+    return load(path, options);
+  };
+
+  return server;
+}
diff --git a/src/assets/brand.js b/src/assets/brand.ts
similarity index 100%
rename from src/assets/brand.js
rename to src/assets/brand.ts
diff --git a/src/lib/employeeRoleModel.js b/src/lib/employeeRoleModel.ts
similarity index 82%
rename from src/lib/employeeRoleModel.js
rename to src/lib/employeeRoleModel.ts
index f125e17..4cffc05 100644
--- a/src/lib/employeeRoleModel.js
+++ b/src/lib/employeeRoleModel.ts
@@ -8,6 +8,18 @@
  * worker WANTS rather than what a posting OFFERS.
  */
 
+/**
+ * `draft` is a EmployeeRole record, typed `any` deliberately.
+ *
+ * The shared types in `src/types/` describe the transport and the signed-in
+ * user; they do not describe entity records yet. That shape is derivable — the
+ * backend generates a column registry from `information_schema` — but it
+ * belongs with the phase that converts the transport layer. A partial interface
+ * written here would be a guess that every later reader treats as settled.
+ * `any` states what is actually known today and is one annotation to replace.
+ */
+type EmployeeRoleDraft = any;
+
 /** English levels, in the order the schema declares them. */
 export const EMPLOYEE_ROLE_STATUSES = ['seeking', 'placed', 'inactive'];
 
@@ -35,7 +47,7 @@ export const defaultEmployeeRole = () => ({
  * A maximum of zero means "no ceiling stated" rather than "free", which is why
  * it is not rendered as a range ending at nothing.
  */
-export function desiredPayLabel(record = {}) {
+export function desiredPayLabel(record: EmployeeRoleDraft = {}): string | null {
   const min = Number(record.desired_pay_min) || 0;
   const max = Number(record.desired_pay_max) || 0;
   if (!min && !max) return null;
@@ -56,7 +68,7 @@ export function desiredPayLabel(record = {}) {
  * defaults one, or falls back to another record's; an absent email reaches the
  * server absent, and the server refuses it.
  */
-export function toNewWorkerWithRolePayload(draft = {}) {
+export function toNewWorkerWithRolePayload(draft: EmployeeRoleDraft = {}) {
   const role = toEmployeeRolePayload(draft);
   /* The identity fields belong to the worker. The server copies them onto the
      role from the row it just created, so sending them twice would let the two
@@ -82,7 +94,7 @@ export function toNewWorkerWithRolePayload(draft = {}) {
  * deliberately: both are the server's, derived from the session, and a value
  * sent for either is dropped before the insert.
  */
-export function toEmployeeRolePayload(draft = {}) {
+export function toEmployeeRolePayload(draft: EmployeeRoleDraft = {}) {
   const record = { ...defaultEmployeeRole(), ...draft };
   return {
     ...record,
diff --git a/src/lib/krowScore.js b/src/lib/krowScore.ts
similarity index 71%
rename from src/lib/krowScore.js
rename to src/lib/krowScore.ts
index b2da1c7..9c9320d 100644
--- a/src/lib/krowScore.js
+++ b/src/lib/krowScore.ts
@@ -1,10 +1,47 @@
+/**
+ * The records this engine reads — WorkerProfile, JobPosting, Course and
+ * LearningPath — are typed `any` deliberately.
+ *
+ * `src/types/` describes the transport and the signed-in user; it does not
+ * describe entity records yet. Those shapes are derivable from the backend's
+ * generated column registry, but they belong with the phase that converts the
+ * transport layer. Written here they would be a guess, and this is the file
+ * where a wrong guess is most expensive: these weights decide what a worker's
+ * score is and which jobs they are shown.
+ *
+ * `computeProfileCompletion` additionally indexes the profile by a field name
+ * held in a list (`profile[f]`), which no partial interface would permit
+ * without either widening it back to `any` or rewriting the loop — and
+ * rewriting it would be a behaviour change in a scoring path.
+ */
+type ProfileRecord = any;
+type JobPostingRecord = any;
+type CourseRecord = any;
+type LearningPathRecord = any;
+
+/** The score, its headline inputs, and the per-dimension breakdown a reader sees. */
+export interface KrowScoreResult {
+  krow_score: number;
+  reliability: number;
+  breakdown: {
+    /** `null`, not 0, where there is no record — an absent dimension renders "—". */
+    attendance: number | null;
+    performance: number;
+    education: number;
+    clientReviews: number;
+    supervisorReviews: number;
+    growth: number;
+    experience: number;
+  };
+}
+
 // Engine 6 — KROW Score Engine (formula-based, auto-recalculated)
 // Reliability = Attendance×.30 + Performance×.25 + Education×.10 + ClientReviews×.15 + SupervisorReviews×.10 + Growth×.05 + Experience×.05
 // KROW Score   = Reliability×.40 + AI Interview×.25 + Education×.15 + Growth×.10 + Experience×.10
 
-const clamp = (n) => Math.max(0, Math.min(100, n));
+const clamp = (n: number) => Math.max(0, Math.min(100, n));
 
-export function computeKrowScore(profile) {
+export function computeKrowScore(profile: ProfileRecord): KrowScoreResult {
   /**
    * Attendance defaults to 100 for *display*: an unrated worker shows a full bar
    * rather than an accusatory 0. That default must not become a scoring input.
@@ -64,7 +101,7 @@ export function computeKrowScore(profile) {
 
 const CORE_FIELDS = ['full_name', 'email', 'phone', 'address', 'current_position', 'desired_position', 'career_goals', 'transportation', 'resume_url'];
 
-export function computeProfileCompletion(profile) {
+export function computeProfileCompletion(profile: ProfileRecord): number {
   let filled = 0;
   for (const f of CORE_FIELDS) if (profile[f]) filled++;
   if (profile.languages?.length) filled++;
@@ -83,7 +120,7 @@ export function computeProfileCompletion(profile) {
 }
 
 /** Returns only the recomputed fields — merge into an update patch */
-export function recalcProfilePatch(profile) {
+export function recalcProfilePatch(profile: ProfileRecord) {
   const { krow_score, reliability, breakdown } = computeKrowScore(profile);
   return {
     krow_score,
@@ -95,7 +132,7 @@ export function recalcProfilePatch(profile) {
 
 // Engine 11 (light) — recommendation helpers
 
-export function recommendNextCourse(profile, learningPaths = [], courses = []) {
+export function recommendNextCourse(profile: ProfileRecord, learningPaths: LearningPathRecord[] = [], courses: CourseRecord[] = []) {
   const p = profile || {};
   const completedIds = new Set((p.completed_courses || []).map(c => c.course_id));
   const desired = (p.desired_position || '').toLowerCase();
@@ -116,14 +153,17 @@ export function recommendNextCourse(profile, learningPaths = [], courses = []) {
   return uncompleted[0] ? { course: uncompleted[0], path: null } : { course: null, path };
 }
 
-export function computeJobMatch(profile, job) {
+export function computeJobMatch(profile: ProfileRecord, job: JobPostingRecord): number {
   const p = profile || {};
   let score = 0;
   const desired = (p.desired_position || '').toLowerCase();
   if (desired && (job.title?.toLowerCase().includes(desired) || job.role_category?.toLowerCase().includes(desired))) score += 35;
 
-  const profileSkills = new Set((p.skills || []).map(s => s.toLowerCase()));
-  const profileCerts = new Set((p.earned_badges || []).map(b => b.name?.toLowerCase()).filter(Boolean));
+  /* `new Set(x)` where x is `any` infers `Set<unknown>`, and the loops below
+     call `.includes` on the members. Naming the element type is the whole
+     fix; the values put into the set are unchanged. */
+  const profileSkills = new Set<string>((p.skills || []).map(s => s.toLowerCase()));
+  const profileCerts = new Set<string>((p.earned_badges || []).map(b => b.name?.toLowerCase()).filter(Boolean));
   const reqSkills = (job.qualifications || []).map(q => q.toLowerCase());
   const reqCerts = (job.certifications_required || []).map(c => c.toLowerCase());
 
@@ -144,7 +184,7 @@ export function computeJobMatch(profile, job) {
   return Math.min(100, Math.round(score));
 }
 
-export function recommendJobs(profile, jobPostings = [], limit = 3) {
+export function recommendJobs(profile: ProfileRecord, jobPostings: JobPostingRecord[] = [], limit = 3) {
   return jobPostings
     .filter(j => j.status === 'active')
     .map(j => ({ job: j, match: computeJobMatch(profile, j) }))
diff --git a/src/lib/provingGround.js b/src/lib/provingGround.ts
similarity index 67%
rename from src/lib/provingGround.js
rename to src/lib/provingGround.ts
index c540ab1..62b5095 100644
--- a/src/lib/provingGround.js
+++ b/src/lib/provingGround.ts
@@ -1,5 +1,57 @@
 import { base44 } from '@/api/base44Client';
 
+/**
+ * Course, WorkerProfile and the conversation turns are typed `any`
+ * deliberately — `src/types/` does not describe entity records yet, and a
+ * partial interface written here would be a guess later readers treat as
+ * settled. See the same note in `krowScore.ts`.
+ */
+type CourseRecord = any;
+type ProfileRecord = any;
+
+/** One turn of the roleplay transcript, as the challenge runner stores it. */
+interface ChallengeTurn {
+  role: string;
+  content: string;
+}
+
+/**
+ * The body sent to `InvokeLLM`, built up across branches.
+ *
+ * Annotated rather than inferred because the code assigns `file_urls` and
+ * `prompt` onto the object AFTER creating it. TypeScript permits that in a
+ * `.js` file — it treats a JavaScript object literal as expandable — and
+ * refuses it in a `.ts` file, where the literal's type is fixed at creation.
+ * That difference is the only thing this interface exists to absorb: the
+ * assignments, their order and their values are untouched, and the emitted
+ * JavaScript is the same either way.
+ */
+interface ChallengeEvalCall {
+  response_json_schema: unknown;
+  model: string;
+  file_urls?: string[];
+  prompt?: string;
+}
+
+/** What the evaluator is asked to return; the schema below is its contract. */
+export interface ChallengeEvaluation {
+  verdict: 'verified' | 'needs_work' | 'failed';
+  score: number;
+  rubric: Record<string, number>;
+  feedback: string;
+  strengths: string[];
+  concerns: string[];
+}
+
+/** The inputs a challenge submission carries, by challenge type. */
+export interface ChallengeSubmission {
+  type: string;
+  mediaUrl?: string;
+  transcript?: string;
+  identified?: { label: string; x: number; y: number }[];
+  workerName?: string;
+}
+
 const CHALLENGE_EVAL_SCHEMA = {
   type: 'object',
   properties: {
@@ -13,7 +65,7 @@ const CHALLENGE_EVAL_SCHEMA = {
 };
 
 /** Real-work unlock gate — shifts, reliability, and badges must be earned first. */
-export function isUnlocked(course, profile = {}) {
+export function isUnlocked(course: CourseRecord, profile: ProfileRecord = {}) {
   const req = course?.unlock_requirements;
   if (!req) return { unlocked: true, reasons: [] };
   const reasons = [];
@@ -27,7 +79,7 @@ export function isUnlocked(course, profile = {}) {
 }
 
 /** One sharp follow-up question during a roleplay challenge. */
-export async function challengeFollowUp(course, history) {
+export async function challengeFollowUp(course: CourseRecord, history: ChallengeTurn[]) {
   const convo = history.map((m) => `${m.role === 'user' ? 'Worker' : 'KROW'}: ${m.content}`).join('\n');
   const prompt = `You are "KROW", running a short proving-ground challenge for the skill "${course?.proof_skill || course?.title}".
 Challenge scenario: ${course?.challenge?.prompt || course?.description}
@@ -41,7 +93,7 @@ Ask your follow-up now. Respond with only the question.`;
 
 /** Evaluate a worker's proof — transcript for roleplay, attached media for photo/video,
  *  identified hazards for photo_identify (with the scene image attached). */
-export async function evaluateChallenge(course, { type, mediaUrl, transcript, identified, workerName }) {
+export async function evaluateChallenge(course: CourseRecord, { type, mediaUrl, transcript, identified, workerName }: ChallengeSubmission) {
   const ch = course?.challenge || {};
   const skill = course?.proof_skill || course?.title;
   const criteria = (ch.rubric || []).map((r) => r.criterion).join(', ') || 'overall_performance';
@@ -50,7 +102,7 @@ export async function evaluateChallenge(course, { type, mediaUrl, transcript, id
     : 'Score "overall_performance" 0-100 in the rubric object.';
 
   let mediaPart;
-  const call = { response_json_schema: CHALLENGE_EVAL_SCHEMA, model: 'claude_sonnet_4_6' };
+  const call: ChallengeEvalCall = { response_json_schema: CHALLENGE_EVAL_SCHEMA, model: 'claude_sonnet_4_6' };
 
   if (type === 'photo_identify') {
     const list = (identified || []).map((h) => `- "${h.label}" at (${Math.round(h.x * 100)}%, ${Math.round(h.y * 100)}%)`).join('\n') || '(no hazards marked)';
diff --git a/src/lib/query-client.js b/src/lib/query-client.ts
similarity index 100%
rename from src/lib/query-client.js
rename to src/lib/query-client.ts
diff --git a/src/lib/roleCategories.js b/src/lib/roleCategories.ts
similarity index 100%
rename from src/lib/roleCategories.js
rename to src/lib/roleCategories.ts
diff --git a/src/lib/talentHome.js b/src/lib/talentHome.ts
similarity index 51%
rename from src/lib/talentHome.js
rename to src/lib/talentHome.ts
index 56086d4..6980ce0 100644
--- a/src/lib/talentHome.js
+++ b/src/lib/talentHome.ts
@@ -1,15 +1,56 @@
 // Derives the Talent "credit score" dimensions and motivational metrics
 // from a WorkerProfile. Keeps the UI honest by mapping to real fields only.
-const clamp = (n, min = 0, max = 100) => Math.max(min, Math.min(max, Math.round(Number(n) || 0)));
 
-export function getTalentScore(profile = {}) {
+/**
+ * `profile` is a WorkerProfile record, typed `any` deliberately.
+ *
+ * The shared types do not describe entity records yet — that shape is derivable
+ * from the backend's generated column registry and belongs with the phase that
+ * converts the transport layer, not with this one. Writing a partial
+ * WorkerProfile here would be a guess wearing an interface, and every reader
+ * after it would treat the guess as settled. `any` says what is actually known
+ * today, which is nothing, and it is one annotation to replace when the real
+ * record type exists.
+ */
+type WorkerProfileRecord = any;
+
+/**
+ * One row of the reputation breakdown.
+ *
+ * `big` marks the headline dimension — Talent Score — which renders larger and
+ * is the one `getFactors` filters out. It is set on exactly one entry and
+ * absent from the other six, so it is optional rather than `boolean`: writing
+ * it as required would describe an object this module never builds.
+ */
+export interface ReputationDimension {
+  key: string;
+  label: string;
+  value: number;
+  big?: boolean;
+}
+
+/** A dimension carrying the weight it contributes, as `getFactors` returns it. */
+export interface ReputationFactor extends ReputationDimension {
+  weight: number;
+}
+
+/** The credit-rating tier for a score, with the colour it renders in. */
+export interface ScoreBand {
+  label: string;
+  color: string;
+}
+
+const clamp = (n: unknown, min = 0, max = 100) =>
+  Math.max(min, Math.min(max, Math.round(Number(n) || 0)));
+
+export function getTalentScore(profile: WorkerProfileRecord = {}) {
   return clamp(profile.krow_score || 0);
 }
 
 // Career Score — FICO-style 300–850 scale, the number shown on the KROW ID.
-export const toFICO = (s) => 300 + Math.round((clamp(s) / 100) * 550);
+export const toFICO = (s: number) => 300 + Math.round((clamp(s) / 100) * 550);
 
-export function getStars(profile = {}) {
+export function getStars(profile: WorkerProfileRecord = {}) {
   const s = getTalentScore(profile);
   if (s >= 90) return 5;
   if (s >= 75) return 4;
@@ -20,18 +61,18 @@ export function getStars(profile = {}) {
 }
 
 // Market value uplift ($/hr) derived from Talent Score
-export function getMarketValue(profile = {}) {
+export function getMarketValue(profile: WorkerProfileRecord = {}) {
   const s = getTalentScore(profile);
   return Math.max(0, Math.round((s - 70) / 5));
 }
 
 // Approximate growth this month (motivational, derived from XP)
-export function getGrowth(profile = {}) {
+export function getGrowth(profile: WorkerProfileRecord = {}) {
   const xp = Number(profile.xp) || 0;
   return clamp(Math.round(xp / 25), 0, 99);
 }
 
-export function getReputation(profile = {}) {
+export function getReputation(profile: WorkerProfileRecord = {}): ReputationDimension[] {
   const s = profile || {};
   const courses = s.completed_courses || [];
   const learning = clamp(courses.length * 8 + (Number(s.xp) || 0) / 10);
@@ -47,7 +88,7 @@ export function getReputation(profile = {}) {
 }
 
 // Weight each reputation factor like a credit score (FICO-style, sums to 100)
-export const FACTOR_WEIGHTS = {
+export const FACTOR_WEIGHTS: Record<string, number> = {
   reliability: 25,
   attendance: 20,
   communication: 15,
@@ -57,7 +98,7 @@ export const FACTOR_WEIGHTS = {
 };
 
 // Score band — the "credit rating" tier for the talent
-export function getScoreBand(score = 0) {
+export function getScoreBand(score = 0): ScoreBand {
   if (score >= 90) return { label: 'Elite', color: '#0838E0' };
   if (score >= 75) return { label: 'Excellent', color: '#16A34A' };
   if (score >= 60) return { label: 'Solid', color: '#2563EB' };
@@ -66,7 +107,7 @@ export function getScoreBand(score = 0) {
   return { label: 'No score yet', color: '#D1D5DB' };
 }
 
-export function getFactors(profile = {}) {
+export function getFactors(profile: WorkerProfileRecord = {}): ReputationFactor[] {
   return getReputation(profile)
     .filter((d) => !d.big)
     .map((d) => ({ ...d, weight: FACTOR_WEIGHTS[d.key] || 0 }));
diff --git a/src/lib/talentInsights.js b/src/lib/talentInsights.ts
similarity index 58%
rename from src/lib/talentInsights.js
rename to src/lib/talentInsights.ts
index 0eba062..54a81a8 100644
--- a/src/lib/talentInsights.js
+++ b/src/lib/talentInsights.ts
@@ -2,8 +2,27 @@
 // client endorsements. Used by both the talent card and the talent detail
 // modal so the two stay in sync.
 
+/**
+ * `profile` is a WorkerProfile record, typed `any` deliberately.
+ *
+ * The shared types in `src/types/` describe the transport and the signed-in
+ * user; they do not describe entity records yet. That shape is derivable — the
+ * backend generates a column registry from `information_schema` — but it
+ * belongs with the phase that converts the transport layer. A partial interface
+ * written here would be a guess that every later reader treats as settled.
+ * `any` states what is actually known today and is one annotation to replace.
+ */
+type WorkerProfileRecord = any;
+
+/** One derived endorsement row, as the talent card and detail modal render it. */
+export interface ClientEndorsement {
+  company: string;
+  role: string;
+  stars: number;
+}
+
 // ESAT — Employee Skills Assessment Transcript; derived from AI interview score
-export function esatTag(profile) {
+export function esatTag(profile: WorkerProfileRecord) {
   const s = Math.round(profile?.ai_interview_score || 0);
   if (s > 0) return { label: `${s}/100`, cls: 'bg-[#FFF7ED] text-[#B45309]' };
   return { label: 'Pending', cls: 'bg-[#F3F4F6] text-[#6B7280]' };
@@ -11,13 +30,13 @@ export function esatTag(profile) {
 
 // Recent job history (last 3 years). experience entries carry a duration
 // (`years`) rather than dates, so we surface the most recent up to 3.
-export function recentJobs(profile) {
+export function recentJobs(profile: WorkerProfileRecord) {
   return (profile?.experience || []).slice(0, 3).filter((e) => e && (e.role || e.company));
 }
 
 // Up to 3 client endorsements, deterministically derived from companies the
 // worker has been placed at, rated off their aggregate client rating.
-export function clientEndorsements(profile) {
+export function clientEndorsements(profile: WorkerProfileRecord): ClientEndorsement[] {
   const companies = (profile?.experience || [])
     .map((e) => e?.company)
     .filter(Boolean);
diff --git a/src/lib/userTracking.js b/src/lib/userTracking.ts
similarity index 64%
rename from src/lib/userTracking.js
rename to src/lib/userTracking.ts
index 847a5b3..f98b27b 100644
--- a/src/lib/userTracking.js
+++ b/src/lib/userTracking.ts
@@ -1,6 +1,10 @@
 import { base44 } from '@/api/base44Client';
+import type { User } from '@/types/user';
 
-let _cachedUser = null;
+/* The signed-in user, or null when nobody is or the lookup failed. Fetched
+   once per page load: this is best-effort logging, and a tracking call must
+   never become a second round trip on a user action. */
+let _cachedUser: User | null = null;
 let _userFetched = false;
 
 async function getCurrentUser() {
@@ -14,8 +18,30 @@ async function getCurrentUser() {
   return _cachedUser;
 }
 
+/**
+ * The optional context an event may carry.
+ *
+ * Every field is optional because every call site supplies a different subset —
+ * the shape is "whatever this particular event knows". The id fields are the
+ * records the event is about; they are written onto the record only when
+ * supplied, so an event with no application does not get an
+ * `application_id: null` that later reads as a missing link.
+ */
+export interface ActivityExtra {
+  email?: string;
+  name?: string;
+  account_type?: string;
+  details?: string;
+  position_id?: string;
+  application_id?: string;
+  candidate_id?: string;
+  interview_id?: string;
+  worker_email?: string;
+  metadata?: unknown;
+}
+
 /** Best-effort activity logging — never throws, never blocks the main flow. */
-export async function logActivity(eventType, extra = {}) {
+export async function logActivity(eventType: string, extra: ActivityExtra = {}) {
   try {
     const me = await getCurrentUser();
     const record = {
diff --git a/src/lib/utils.js b/src/lib/utils.ts
similarity index 56%
rename from src/lib/utils.js
rename to src/lib/utils.ts
index 3d8d2cb..9561ee8 100644
--- a/src/lib/utils.js
+++ b/src/lib/utils.ts
@@ -1,4 +1,4 @@
-import { clsx } from "clsx"
+import { clsx, type ClassValue } from "clsx"
 import { extendTailwindMerge } from "tailwind-merge"
 
 /**
@@ -27,7 +27,18 @@ const twMerge = extendTailwindMerge({
   },
 })
 
-export function cn(...inputs) {
+/**
+ * `ClassValue` is clsx's own type, so this accepts exactly what clsx accepts
+ * and nothing has to be kept in step by hand: strings, numbers, `null`,
+ * `undefined`, `false`, arrays of any of those, and `{ 'class-name': boolean }`
+ * objects, nested to any depth. That breadth is deliberate — the conditional
+ * forms are most of why callers reach for `cn` at all.
+ *
+ * The body is untouched. `clsx(inputs)` is passed the rest array rather than
+ * spread into it, which is not the usual shape but is what this has always
+ * done, and clsx flattens an array argument to the same string either way.
+ */
+export function cn(...inputs: ClassValue[]): string {
   return twMerge(clsx(inputs))
 }
 
diff --git a/src/types/api.ts b/src/types/api.ts
new file mode 100644
index 0000000..584146a
--- /dev/null
+++ b/src/types/api.ts
@@ -0,0 +1,129 @@
+/**
+ * The shapes the Krow API speaks in.
+ *
+ * Types only — this module emits nothing. Import it with `import type` so it is
+ * erased at build time and never becomes a runtime dependency of the transport.
+ *
+ * Every declaration here is transcribed from the API's own contract
+ * (`krow-backend/docs/api-contract.md`, §1, §4 and §5) and cross-read against
+ * what `src/api/httpClient.js` actually does with the response today. Where the
+ * two could differ, the running code wins, because the callers were written
+ * against it.
+ *
+ * Nothing in `src` imports this yet. It exists so that the transport layer has
+ * a vocabulary to be converted INTO, rather than one invented halfway through
+ * converting it.
+ */
+
+/**
+ * Collection metadata, from the `meta` half of a list response.
+ *
+ * Present on `list` and `filter` only; a single record carries no `meta`.
+ *
+ * Worth knowing before anyone reaches for it: `httpClient.request` returns
+ * `payload.data` and **drops `meta` on the floor**. That is deliberate — §4.2
+ * records that nothing reads it, and surfacing it would change what the six
+ * entity methods return, which the transport swap was not allowed to do. So
+ * this type describes a value that is real on the wire and currently
+ * unreachable from application code. Typing it costs nothing and means the
+ * shape is already written down on the day someone wants `total`.
+ *
+ * `truncated` is `true` when `total > offset + returned`, which is the silent
+ * data-hiding bug §12.2 describes. It is not a bug this type fixes.
+ */
+export interface ApiMeta {
+  total: number;
+  limit: number;
+  offset: number;
+  returned: number;
+  truncated: boolean;
+}
+
+/**
+ * What comes back on the wire, before `request` unwraps it.
+ *
+ * A successful response is always `{ data: … }`; a collection adds `meta`. The
+ * envelope exists so `meta` has somewhere to live (§1.1) and is unwrapped in
+ * exactly one place, so no hook, page or component has ever seen it.
+ */
+export interface ApiEnvelope<T> {
+  data: T;
+  meta?: ApiMeta;
+}
+
+/**
+ * The eight codes the API is allowed to return (§5).
+ *
+ * A closed union rather than `string`, because these are a fixed vocabulary the
+ * server owns and the client branches on — `isUnauthenticated` tests for
+ * `'unauthorized'` by name.
+ *
+ * `'unreachable'` is NOT in this union and is deliberately kept out: it is not
+ * an API code. `httpClient` synthesises it when `fetch` itself rejects and
+ * there is no response, no status and no envelope to read a code from. It
+ * belongs to `KrowApiError` below, where the distinction between "the API said
+ * no" and "there was no API" stays visible.
+ */
+export type ApiErrorCode =
+  | 'unauthorized'
+  | 'forbidden'
+  | 'rate_limited'
+  | 'not_found'
+  | 'validation_failed'
+  | 'invalid_query'
+  | 'conflict'
+  | 'internal';
+
+/**
+ * The body of a non-2xx response.
+ *
+ * `details` maps field → reason on `validation_failed` and is `{}` otherwise.
+ */
+export interface ApiErrorBody {
+  code: ApiErrorCode;
+  message: string;
+  details: Record<string, unknown>;
+}
+
+/** A non-2xx response, whole. */
+export interface ApiErrorResponse {
+  error: ApiErrorBody;
+}
+
+/**
+ * The error a failed request becomes on the client.
+ *
+ * An **interface, not a class**, and that is the load-bearing decision in this
+ * file. `httpClient` builds these by constructing a plain `Error` and assigning
+ * four properties onto it:
+ *
+ *     const error = new Error(body?.message || `Request failed with status ${status}`);
+ *     error.name = 'KrowApiError';
+ *     error.status = status;
+ *     error.code = body?.code || 'internal';
+ *     error.details = body?.details || {};
+ *
+ * Declaring a `class KrowApiError extends Error` would be the tidier-looking
+ * conversion and would change behaviour: it alters the prototype chain, so
+ * `instanceof` starts answering differently, and anything comparing
+ * `error.name === 'KrowApiError'` is relying on a string that a class would set
+ * by a different route. The migration's whole claim is that it changes nothing,
+ * so the shape is described rather than rebuilt — Phase 4 casts the constructed
+ * `Error` to this interface and the emitted JavaScript stays identical.
+ *
+ * `code` widens to include `'unreachable'` because `fetch` rejecting is not an
+ * API answer: that path sets `status: 0`, `details: {}` and a `cause`, and its
+ * message names the URL that did not respond rather than anything the server
+ * said.
+ *
+ * `status` is `0` for that transport failure and the HTTP status otherwise.
+ * Both `isUnauthenticated` and the 429 branch in `pages/admin/Login.jsx` read
+ * it, which is why it is required rather than optional.
+ */
+export interface KrowApiError extends Error {
+  name: 'KrowApiError';
+  status: number;
+  code: ApiErrorCode | 'unreachable';
+  details: Record<string, unknown>;
+  cause?: unknown;
+}
diff --git a/src/types/entities.ts b/src/types/entities.ts
new file mode 100644
index 0000000..d31f5ed
--- /dev/null
+++ b/src/types/entities.ts
@@ -0,0 +1,135 @@
+/**
+ * Which entities exist, and the surface each one presents.
+ *
+ * Types only — nothing here emits. Import with `import type`.
+ *
+ * This file exists because the list of entities is currently written down
+ * **twice**: as the keys of `RESOURCE_PATHS` in `src/api/httpClient.js`, and as
+ * the `ENTITY_NAMES` array in `src/api/base44Client.js`. They hold the same
+ * eighteen names in a different order, and nothing checks that they agree. They
+ * agree today; they are one careless edit from not doing so, and the symptom
+ * would be `base44.entities.Whatever` being `undefined` at runtime with no
+ * warning from anywhere.
+ *
+ * Note what this file does NOT do: it does not replace either list. Both stay
+ * exactly where they are, because collapsing them into one is a runtime
+ * refactor and this phase changes no runtime behaviour. What it adds is a
+ * single type the two can be checked against once they are TypeScript, which
+ * turns a silent divergence into a compile error.
+ *
+ * Verified against the backend on 2026-09-11: fifteen of these eighteen appear
+ * in `krow-backend/go-api/internal/domain/resources_gen.go` — a registry
+ * generated from `information_schema`, so it cannot drift from the migrations —
+ * and every one of those fifteen paths matches character for character. The
+ * three that are absent from it are served by dedicated handlers rather than
+ * the generic entity machinery: `AgentDefinition` and `SkillDefinition` by
+ * `httpserver/definitions.go`, and the user by `httpserver/me.go`.
+ */
+
+/**
+ * Every entity name the client knows, spelled as the frontend spells it.
+ *
+ * PascalCase and used verbatim in error messages — §5.1 of the API contract
+ * makes the entity name load-bearing in a `not_found` message, which reads
+ * `"<EntityName> <id> not found"` using this spelling rather than the table
+ * name.
+ *
+ * `'User'` is in this union because it is in both runtime lists, not because it
+ * works. There is no `/api/v1/users` route on the backend, and nothing in `src`
+ * calls `base44.entities.User` — a call would 404. It is recorded here as it
+ * is, dead entry and all, because removing it from the union while both runtime
+ * lists still carry it would make the type a description of something other
+ * than this codebase. Whether the entry should exist at all is a product
+ * question, not a migration one.
+ */
+export type EntityName =
+  | 'JobPosting'
+  | 'JobApplication'
+  | 'AIInterview'
+  | 'Staff'
+  | 'WorkerProfile'
+  | 'EmployeeRole'
+  | 'Course'
+  | 'Badge'
+  | 'LearningPath'
+  | 'Certification'
+  | 'RoleCategory'
+  | 'UserActivity'
+  | 'Evidence'
+  | 'User'
+  | 'Assignment'
+  | 'ShiftRecord'
+  | 'AgentDefinition'
+  | 'SkillDefinition';
+
+/**
+ * The URL segment each entity lives under.
+ *
+ * Kebab-case plural, with mass nouns left singular — `staff`, `evidence`,
+ * `user-activity` (§1). Declared rather than derived, for the reason
+ * `httpClient` gives at the site of the real map: a rule that turns
+ * `AIInterview` into `ai-interviews` and `Staff` into `staff` and `UserActivity`
+ * into `user-activity` is three special cases wearing a trench coat, and a
+ * wrong guess is a 404 at run time instead of a mistake anyone can see.
+ */
+export type EntityResourcePath =
+  | 'job-postings'
+  | 'job-applications'
+  | 'ai-interviews'
+  | 'staff'
+  | 'worker-profiles'
+  | 'employee-roles'
+  | 'courses'
+  | 'badges'
+  | 'learning-paths'
+  | 'certifications'
+  | 'role-categories'
+  | 'user-activity'
+  | 'evidence'
+  | 'users'
+  | 'assignments'
+  | 'shift-records'
+  | 'agent-definitions'
+  | 'skill-definitions';
+
+/**
+ * What `createEntity(name)` hands back: one entity's client surface.
+ *
+ * Eight members, transcribed from `src/api/httpClient.js` — the six methods
+ * `store.js` declared, plus `bulkCreate` and the `entityName` the object
+ * carries around.
+ *
+ * The defaults are part of the signature rather than incidental. `store.js`
+ * declared `list(sort = '-created_date', limit = 100)` and several call sites
+ * rely on them instead of passing their own, so a conversion that dropped them
+ * would change what those callers fetch.
+ *
+ * `T` is the record type, left open here. Phase 2 deliberately does not define
+ * the eighteen record shapes: they are derivable — `resources_gen.go` carries
+ * every column with its type, nullability and enum values — but nothing
+ * consumes them until the transport layer is converted, and transcribing some
+ * five hundred field declarations by hand ahead of a consumer is how a type
+ * becomes confidently wrong. They belong with Phase 4, generated from that
+ * registry rather than retyped from it.
+ *
+ * Until then `EntityClient<T>` describes the shape of the surface without
+ * asserting anything about the records that travel through it, which is exactly
+ * as much as is known today.
+ */
+export interface EntityClient<T = unknown> {
+  entityName: EntityName;
+  list(sort?: string, limit?: number): Promise<T[]>;
+  filter(query?: Record<string, unknown>, sort?: string, limit?: number): Promise<T[]>;
+  get(id: string): Promise<T>;
+  create(data: Partial<T>): Promise<T>;
+  update(id: string, data: Partial<T>): Promise<T>;
+  /** Resolves to `{ id }`, matching what `store.js` returned (§4.3). */
+  delete(id: string): Promise<{ id: string }>;
+  /**
+   * Sequential creates, not a batch endpoint and not `Promise.all`: there is no
+   * bulk write in the contract (§12.1), and doing them one at a time keeps the
+   * failure behaviour identical — the first rejection stops the run and the
+   * records written before it stay written.
+   */
+  bulkCreate(records?: Partial<T>[]): Promise<T[]>;
+}
diff --git a/src/types/global.d.ts b/src/types/global.d.ts
new file mode 100644
index 0000000..4a43dc3
--- /dev/null
+++ b/src/types/global.d.ts
@@ -0,0 +1,26 @@
+export {};
+
+/**
+ * Globals this app adds to the browser's own.
+ *
+ * There is exactly one, and it is a custom event rather than anything hung off
+ * `window` — nothing in `src` ever assigns a property to `window`, and this
+ * should stay true.
+ *
+ * `krow:open-owliver` is how a component that is nowhere near the assistant
+ * asks for the assistant to open. The talent shell listens for it
+ * (`src/layouts/Layout.jsx`) and two buttons plus the employee dashboard
+ * dispatch it. Declaring it in `WindowEventMap` is what lets
+ * `addEventListener` and `dispatchEvent` agree on the name: without it both
+ * sides fall back to the untyped string overload, and a misspelling on either
+ * side is a listener that never fires and nothing that says why.
+ *
+ * The payload is an unparameterised `CustomEvent` because the event carries no
+ * detail — it is a signal, not a message. If it ever gains one, give it
+ * `CustomEvent<{ … }>` here and both ends are checked against it at once.
+ */
+declare global {
+  interface WindowEventMap {
+    'krow:open-owliver': CustomEvent;
+  }
+}
diff --git a/src/types/user.ts b/src/types/user.ts
new file mode 100644
index 0000000..def5d3e
--- /dev/null
+++ b/src/types/user.ts
@@ -0,0 +1,132 @@
+/**
+ * The signed-in user, and the preferences that travel with the account.
+ *
+ * Types only — nothing here emits. Import with `import type`.
+ *
+ * Transcribed from the projection the server actually selects, not from the
+ * documentation of it. `krow-backend/go-api/internal/httpserver/me.go` builds
+ * every user record from one constant:
+ *
+ *     const userColumns = `id::text AS id, legacy_id, full_name, email::text AS email,
+ *         role, account_type, status,
+ *         to_char(created_date …) AS created_date,
+ *         to_char(updated_date …) AS updated_date`
+ *
+ * and then attaches `preferences`. That is ten fields. The contract document's
+ * worked example in §9 shows seven — it omits `status` and `updated_date`, and
+ * it is the older of the two. The code is what answers the request, so the code
+ * is what is written down here.
+ */
+
+/**
+ * What the account is allowed to do.
+ *
+ * A closed union because the database closes it: `users_role_check` is
+ * `CHECK (role IN ('admin', 'employer', 'talent'))`, so no other value can be
+ * stored and none can be returned.
+ *
+ * This is the authorization field. It is server-owned — `PATCH /me` ignores it,
+ * deliberately, because when it was writable any signed-in user could promote
+ * themselves to admin with a one-line request.
+ */
+export type UserRole = 'admin' | 'employer' | 'talent';
+
+/**
+ * Whether the account may sign in.
+ *
+ * Closed for the same reason: `users_status_check` is
+ * `CHECK (status IN ('active', 'suspended'))`. Also server-owned.
+ */
+export type UserStatus = 'active' | 'suspended';
+
+/**
+ * Product preferences, stored on the account.
+ *
+ * Three named keys and an open tail, and the open tail is not a hedge — it is
+ * the shape. The `user_preferences` table has exactly three boolean columns
+ * plus an `extra jsonb` blob, and the server merges that blob into the same
+ * flat object it returns. Everything account-authored lives in there:
+ * `customSkills` and `customAgents`, written by `WorkspaceSkills.jsx`,
+ * `SkillEditor.jsx`, `OwliverSkillEditor.jsx` and `useAgents.js`.
+ *
+ * The index signature is therefore a true statement about the runtime value,
+ * not a shortcut. Naming `customSkills` and `customAgents` explicitly was
+ * tempting and rejected: their contents are the authored-definition shapes,
+ * which belong to the agent layer, and this phase does not describe the agent
+ * layer.
+ *
+ * The three named keys are the one place field naming diverges from the
+ * database — camelCase here, snake_case in the columns. The server does that
+ * translation; nothing on this side should.
+ */
+export interface UserPreferences {
+  owliverDefault: boolean;
+  compactDensity: boolean;
+  emailDigest: boolean;
+  [key: string]: unknown;
+}
+
+/**
+ * The user as `GET /me` returns it.
+ *
+ * Four fields are optional, and the reason is worth stating because it is not
+ * laziness. `base44.auth.me()` does not always resolve to a server response: on
+ * the path through `readCachedUser` it returns
+ * `{ ...DEMO_USER, ...JSON.parse(raw) }`, and `DEMO_USER` — the default shape
+ * in `src/api/demoUser.js` that has to resolve during the first render, before
+ * the server has answered — carries only `id`, `full_name`, `email`, `role`,
+ * `account_type`, `created_date` and `preferences`.
+ *
+ * So a value of this type may genuinely lack `legacy_id`, `status` and
+ * `updated_date`. Marking them required would describe the server's answer
+ * accurately and the runtime value inaccurately, and the second is the one that
+ * reaches components.
+ *
+ * `legacy_id` is additionally nullable at the source — `legacy_id text UNIQUE`,
+ * no NOT NULL — so it is `string | null` when present. It holds the original
+ * seeded identifier (`user_demo`); `id` is the uuid and is the only addressable
+ * one.
+ */
+export interface User {
+  id: string;
+  full_name: string;
+  email: string;
+  role: UserRole;
+  /**
+   * Which product surface the person is looking at, Employer or Talent.
+   *
+   * Plain `string`, not a union, and that is checked rather than assumed: the
+   * column is `account_type text NOT NULL DEFAULT 'employer'` with **no CHECK
+   * constraint**, and the frontend reads it as open text — `|| 'applicant'`,
+   * `|| 'unknown'`, `|| '—'` all appear at call sites. There is no closed set
+   * to write down, so none is invented.
+   *
+   * Explicitly not an authorization field. `role` authorizes; this is display.
+   */
+  account_type: string;
+  created_date: string;
+  preferences: UserPreferences;
+  legacy_id?: string | null;
+  status?: UserStatus;
+  updated_date?: string;
+}
+
+/**
+ * What `auth.updatePreferences()` resolves to.
+ *
+ * Not a bare user, and the reason is a bug rather than a preference: a
+ * swallowed `QuotaExceededError` once silently lost account-authored skills, so
+ * a caller storing something it needs back after a reload has to be able to
+ * tell a write that landed from one the browser refused. The cache is updated
+ * either way — the change is real for the session even when it could not be
+ * stored.
+ *
+ * Over HTTP a failed write is already a non-2xx, so the client synthesises
+ * `{ user, persisted: true, error: null }` on success and lets the throw path
+ * handle failure. `src/lib/skills/saveFeedback.js` is the only consumer.
+ */
+export interface PreferencesUpdateResult {
+  user: User;
+  persisted: boolean;
+  error: Error | null;
+}
diff --git a/src/vite-env.d.ts b/src/vite-env.d.ts
new file mode 100644
index 0000000..bd336d6
--- /dev/null
+++ b/src/vite-env.d.ts
@@ -0,0 +1,43 @@
+/// <reference types="vite/client" />
+
+/**
+ * Vite's build-time additions to `import.meta`, and the environment this app
+ * actually reads from it.
+ *
+ * The reference above is what supplies `import.meta.env`, `import.meta.glob`
+ * and the `?raw` module shape. Without it the two registries that discover
+ * agents and skills from the filesystem do not typecheck at all, and one of
+ * them carries a hand-written `@ts-ignore` saying so.
+ *
+ * The interface below names the two variables this codebase reads. It does not
+ * restrict `import.meta.env` to them — this declaration MERGES with Vite's,
+ * which carries an open `[key: string]: any`, so `import.meta.env.VITE_ANYTHING`
+ * still compiles and still comes back as `any`. Typing cannot close that hole;
+ * only reading this list can.
+ *
+ * Declaring them is therefore documentation as much as typing: these are
+ * inlined at build time, so a variable missing when the bundle is built is
+ * missing for the life of that bundle, and a typo is not a runtime error
+ * anywhere — it is a silent `undefined` and a fallback taken forever.
+ *
+ *   VITE_API_BASE_URL  src/api/httpClient.js — where the entity API lives.
+ *                      Defaults to the same-origin '/api/v1', which is the
+ *                      supported arrangement: the session cookie is HttpOnly
+ *                      and SameSite=Lax, so a cross-origin value breaks auth.
+ *   VITE_AGENT_API     src/components/ai-assistant/provider.js — the agent
+ *                      endpoint. Unset means the local engine answers.
+ *
+ * VITE_API_PROXY_TARGET is deliberately absent: it is read by `vite.config.js`
+ * through `loadEnv` at dev-server startup and never reaches `import.meta.env`.
+ *
+ * Both are optional because both have fallbacks, and typing them as required
+ * would claim a guarantee the build does not make.
+ */
+interface ImportMetaEnv {
+  readonly VITE_API_BASE_URL?: string;
+  readonly VITE_AGENT_API?: string;
+}
+
+interface ImportMeta {
+  readonly env: ImportMetaEnv;
+}
diff --git a/tsconfig.json b/tsconfig.json
new file mode 100644
index 0000000..45bf27e
--- /dev/null
+++ b/tsconfig.json
@@ -0,0 +1,84 @@
+{
+  /* The TypeScript configuration, succeeding `jsconfig.json`.
+     Deliberately a translation of what was already there rather than a fresh
+     start: every option below that existed in jsconfig carries its old value,
+     so the first day of the migration checks exactly what the last day before
+     it checked. The four additions are marked.
+
+     `jsconfig.json` is left in place for now and is inert — TypeScript ignores
+     it wherever a `tsconfig.json` sits beside it. It is removed in the final
+     phase, once nothing is asking for it. */
+  "compilerOptions": {
+    "baseUrl": ".",
+    "paths": {
+      "@/*": ["./src/*"]
+    },
+    "jsx": "react-jsx",
+    "module": "esnext",
+    "moduleResolution": "bundler",
+    "lib": ["esnext", "dom", "dom.iterable"],
+    "target": "esnext",
+
+    /* Vite builds; this config only ever checks. Stating it means no stray
+       output can appear next to a source file if anyone runs `tsc` directly. */
+    "noEmit": true,
+
+    /* The two that make an incremental migration possible. `allowJs` lets a
+       `.ts` file and a `.js` file import each other with no ceremony, so files
+       can be converted one at a time instead of in one unreviewable commit;
+       `checkJs` keeps the JSDoc-typed JavaScript under the same scrutiny it
+       has had all along, so nothing is lost in the meantime. Both go away at
+       the end of the migration, not before. */
+    "allowJs": true,
+    "checkJs": true,
+
+    /* NEW. esbuild compiles each file on its own and cannot see across them, so
+       a construct that needs whole-program knowledge — re-exporting a type as
+       if it were a value, most often — works under `tsc` and breaks in the
+       bundle. This makes tsc refuse what esbuild could not have done anyway. */
+    "isolatedModules": true,
+
+    /* NEW. macOS does not distinguish `Button` from `button`; CI does. Without
+       this, a mis-cased import is a green local build and a red pipeline. */
+    "forceConsistentCasingInFileNames": true,
+
+    "skipLibCheck": true,
+    "allowSyntheticDefaultImports": true,
+    "esModuleInterop": true,
+    "resolveJsonModule": true,
+
+    /* CHANGED, from `[]`. The empty list suppressed every ambient type package,
+       which is why `import.meta.env` and `import.meta.glob` — Vite build-time
+       APIs, absent from the standard `ImportMeta` — were reported as errors in
+       eight places across the app.
+
+       Named explicitly rather than left to default, because the default pulls
+       in EVERYTHING under node_modules/@types, and `@types/node` is installed.
+       In browser code that would make `setTimeout` return a `NodeJS.Timeout`
+       instead of a number, which is wrong and quietly infectious: three
+       components store a timer handle in a `useRef` and would be typed against
+       a runtime they do not run on. Node's types belong to `vite.config.js` and
+       `scripts/`, neither of which this project includes. */
+    "types": ["vite/client"],
+
+    /* Off for now, and turned on a flag at a time later in the migration —
+       `noImplicitAny`, then `strictNullChecks`, then the rest. Enabling it here
+       would bury the ~70 real errors this project already has under several
+       hundred more, and the point of going file by file is that each step is
+       small enough to read. */
+    "strict": false
+  },
+
+  "include": ["src/**/*"],
+
+  /* Unchanged from jsconfig, and temporary. These three trees hold the densest
+     logic in the app — the transport layer, every hook, and the vendored UI
+     primitives — and none of it has ever been checked. Each exclusion is
+     removed by the phase that converts the tree behind it, so the error count
+     rises deliberately and in one identifiable place at a time.
+
+     Note that excluding a file only keeps it out of the root set: one that an
+     included file imports is still checked, which is why errors from `src/api`
+     and `src/lib` already show up today. */
+  "exclude": ["node_modules", "dist", "src/components/ui", "src/api", "src/lib"]
+}