diff --git a/.github/workflows/rust.yml b/.github/workflows/rust.yml
index a139515..1aff814 100644
--- a/.github/workflows/rust.yml
+++ b/.github/workflows/rust.yml
@@ -77,6 +77,12 @@ jobs:
       # (the runtime half) runs in the `test` job's `npm run test`. Deps were installed by the
       # `npm ci --ignore-scripts` above.
       run: npm --prefix engine/web run lint
+    - name: Typecheck dashboard client (tsc --noEmit)
+      # JEF-399: eslint's no-unused-vars (JEF-499) catches unused imports; it does not type-check.
+      # `tsc --noEmit` over engine/web/src (tsconfig.json: checkJs, jsx: react-jsx / preact, offline —
+      # no `.d.ts` fetch) fails the build on a real type error (e.g. a JSX prop of the wrong type)
+      # slipping into the bundle. Deps were installed by the `npm ci --ignore-scripts` above.
+      run: npm --prefix engine/web run typecheck
     - name: Format
       run: cargo fmt --check
     - name: Clippy
diff --git a/engine/web/package-lock.json b/engine/web/package-lock.json
index 63c89d3..2813f36 100644
--- a/engine/web/package-lock.json
+++ b/engine/web/package-lock.json
@@ -19,6 +19,7 @@
         "globals": "17.7.0",
         "jsdom": "^25.0.1",
         "preact": "10.29.7",
+        "typescript": "7.0.2",
         "vitest": "^3.2.6",
         "vitest-axe": "0.1.0"
       }
@@ -1323,6 +1324,346 @@
       "dev": true,
       "license": "MIT"
     },
+    "node_modules/@typescript/typescript-aix-ppc64": {
+      "version": "7.0.2",
+      "resolved": "https://registry.npmjs.org/@typescript/typescript-aix-ppc64/-/typescript-aix-ppc64-7.0.2.tgz",
+      "integrity": "sha512-MTKKkWB7p/0E9xi1d1tHtZ5PiLkGEMIq88pK2CubZjOsLtYTLqhgIgi6zepFa+9GHZ6h05NMCkQxGKiPXMxXtQ==",
+      "cpu": [
+        "ppc64"
+      ],
+      "dev": true,
+      "license": "Apache-2.0",
+      "optional": true,
+      "os": [
+        "aix"
+      ],
+      "engines": {
+        "node": ">=16.20.0"
+      }
+    },
+    "node_modules/@typescript/typescript-darwin-arm64": {
+      "version": "7.0.2",
+      "resolved": "https://registry.npmjs.org/@typescript/typescript-darwin-arm64/-/typescript-darwin-arm64-7.0.2.tgz",
+      "integrity": "sha512-gowzar9MwS/aRWp6f3a4KUqzRjAZjOsmGNCM6LcTgXum+dBfgsBVMN+AgvOCCbguXyick6LJhpBszxMebJ8syA==",
+      "cpu": [
+        "arm64"
+      ],
+      "dev": true,
+      "license": "Apache-2.0",
+      "optional": true,
+      "os": [
+        "darwin"
+      ],
+      "engines": {
+        "node": ">=16.20.0"
+      }
+    },
+    "node_modules/@typescript/typescript-darwin-x64": {
+      "version": "7.0.2",
+      "resolved": "https://registry.npmjs.org/@typescript/typescript-darwin-x64/-/typescript-darwin-x64-7.0.2.tgz",
+      "integrity": "sha512-SZ9xZInqApNlNGc9s0W1VSsktYSOe9cFqNOIqmN1Gs8SmkjKZYFt017G4VwPxASInODuAdbTW7sXiFUf893RgA==",
+      "cpu": [
+        "x64"
+      ],
+      "dev": true,
+      "license": "Apache-2.0",
+      "optional": true,
+      "os": [
+        "darwin"
+      ],
+      "engines": {
+        "node": ">=16.20.0"
+      }
+    },
+    "node_modules/@typescript/typescript-freebsd-arm64": {
+      "version": "7.0.2",
+      "resolved": "https://registry.npmjs.org/@typescript/typescript-freebsd-arm64/-/typescript-freebsd-arm64-7.0.2.tgz",
+      "integrity": "sha512-W5NH4y/J0plIIS5b2xvTEkU7JFxyqdMAOgf+Ilhl0vHQXKO5dZoxd+C/jEtq56c4F3wk71RB4BMRQ2XdI+bwYQ==",
+      "cpu": [
+        "arm64"
+      ],
+      "dev": true,
+      "license": "Apache-2.0",
+      "optional": true,
+      "os": [
+        "freebsd"
+      ],
+      "engines": {
+        "node": ">=16.20.0"
+      }
+    },
+    "node_modules/@typescript/typescript-freebsd-x64": {
+      "version": "7.0.2",
+      "resolved": "https://registry.npmjs.org/@typescript/typescript-freebsd-x64/-/typescript-freebsd-x64-7.0.2.tgz",
+      "integrity": "sha512-UMGDx5sTpzNw3WiPebH7l90IWfJggEd+egHt/q6p7/Cm3zqoV7VxkGXt+3DxPIw8CcmvAB0j3sVVfbhX+M4Tpw==",
+      "cpu": [
+        "x64"
+      ],
+      "dev": true,
+      "license": "Apache-2.0",
+      "optional": true,
+      "os": [
+        "freebsd"
+      ],
+      "engines": {
+        "node": ">=16.20.0"
+      }
+    },
+    "node_modules/@typescript/typescript-linux-arm": {
+      "version": "7.0.2",
+      "resolved": "https://registry.npmjs.org/@typescript/typescript-linux-arm/-/typescript-linux-arm-7.0.2.tgz",
+      "integrity": "sha512-gffT3xPz9sR7j/YJExkyPntrI0P2EP9XbOyWzth2/Gs0RstK+90RBcO0ncXoXy/beYll1SXw846Nf2zdnEz0QQ==",
+      "cpu": [
+        "arm"
+      ],
+      "dev": true,
+      "license": "Apache-2.0",
+      "optional": true,
+      "os": [
+        "linux"
+      ],
+      "engines": {
+        "node": ">=16.20.0"
+      }
+    },
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+      "version": "7.0.2",
+      "resolved": "https://registry.npmjs.org/@typescript/typescript-linux-arm64/-/typescript-linux-arm64-7.0.2.tgz",
+      "integrity": "sha512-Qh4eU4/y3yDjnfjjyPYihMj5/ODIlmt+Bzu17OI+fiSRDW57QmU5SiN63exPRNJPKUzcc1INa1NXdrJ+MqHjUQ==",
+      "cpu": [
+        "arm64"
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+      "dev": true,
+      "license": "Apache-2.0",
+      "optional": true,
+      "os": [
+        "linux"
+      ],
+      "engines": {
+        "node": ">=16.20.0"
+      }
+    },
+    "node_modules/@typescript/typescript-linux-loong64": {
+      "version": "7.0.2",
+      "resolved": "https://registry.npmjs.org/@typescript/typescript-linux-loong64/-/typescript-linux-loong64-7.0.2.tgz",
+      "integrity": "sha512-uEHck9i8hoAzXPiYRib1O7miOnz23SxIeVl6F4LXox+qov1K35jHcEW6VHKvZI+pyvl7fZEP4MCU5LYvIq1GuQ==",
+      "cpu": [
+        "loong64"
+      ],
+      "dev": true,
+      "license": "Apache-2.0",
+      "optional": true,
+      "os": [
+        "linux"
+      ],
+      "engines": {
+        "node": ">=16.20.0"
+      }
+    },
+    "node_modules/@typescript/typescript-linux-mips64el": {
+      "version": "7.0.2",
+      "resolved": "https://registry.npmjs.org/@typescript/typescript-linux-mips64el/-/typescript-linux-mips64el-7.0.2.tgz",
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+      "cpu": [
+        "mips64el"
+      ],
+      "dev": true,
+      "license": "Apache-2.0",
+      "optional": true,
+      "os": [
+        "linux"
+      ],
+      "engines": {
+        "node": ">=16.20.0"
+      }
+    },
+    "node_modules/@typescript/typescript-linux-ppc64": {
+      "version": "7.0.2",
+      "resolved": "https://registry.npmjs.org/@typescript/typescript-linux-ppc64/-/typescript-linux-ppc64-7.0.2.tgz",
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+      "cpu": [
+        "ppc64"
+      ],
+      "dev": true,
+      "license": "Apache-2.0",
+      "optional": true,
+      "os": [
+        "linux"
+      ],
+      "engines": {
+        "node": ">=16.20.0"
+      }
+    },
+    "node_modules/@typescript/typescript-linux-riscv64": {
+      "version": "7.0.2",
+      "resolved": "https://registry.npmjs.org/@typescript/typescript-linux-riscv64/-/typescript-linux-riscv64-7.0.2.tgz",
+      "integrity": "sha512-wf0jqEDOjrPRnKwYRyyJDRo11KMbvMFrU+q4zqKyChODBzvlkbhNQfKvLxQCcwTpdDaXSHZTVuh0JoCrKCUMHQ==",
+      "cpu": [
+        "riscv64"
+      ],
+      "dev": true,
+      "license": "Apache-2.0",
+      "optional": true,
+      "os": [
+        "linux"
+      ],
+      "engines": {
+        "node": ">=16.20.0"
+      }
+    },
+    "node_modules/@typescript/typescript-linux-s390x": {
+      "version": "7.0.2",
+      "resolved": "https://registry.npmjs.org/@typescript/typescript-linux-s390x/-/typescript-linux-s390x-7.0.2.tgz",
+      "integrity": "sha512-IkwJc3L7yhytWd/ewjyxNDfOmswCm9GWMJT/ue/dU4aZNbwZeYAetq42VyLmsmSjvoX7z74X6ZaYCtzAr0EuGw==",
+      "cpu": [
+        "s390x"
+      ],
+      "dev": true,
+      "license": "Apache-2.0",
+      "optional": true,
+      "os": [
+        "linux"
+      ],
+      "engines": {
+        "node": ">=16.20.0"
+      }
+    },
+    "node_modules/@typescript/typescript-linux-x64": {
+      "version": "7.0.2",
+      "resolved": "https://registry.npmjs.org/@typescript/typescript-linux-x64/-/typescript-linux-x64-7.0.2.tgz",
+      "integrity": "sha512-EYdf2cNg7rgCWJnxCdJ+F3V39O8ihb37eHAu1LK8oAFizgTQbPOK7zHHXbPt8rX24COqODXeI3sIf0fCXG7H/A==",
+      "cpu": [
+        "x64"
+      ],
+      "dev": true,
+      "license": "Apache-2.0",
+      "optional": true,
+      "os": [
+        "linux"
+      ],
+      "engines": {
+        "node": ">=16.20.0"
+      }
+    },
+    "node_modules/@typescript/typescript-netbsd-arm64": {
+      "version": "7.0.2",
+      "resolved": "https://registry.npmjs.org/@typescript/typescript-netbsd-arm64/-/typescript-netbsd-arm64-7.0.2.tgz",
+      "integrity": "sha512-+polYF4MF04aPpO5FTkHran9yUQDSXqy5GiSDKpsll5jy3l3+g9QLhpf39T+ePtefhXLOGrLl0QIjkQP6VnelA==",
+      "cpu": [
+        "arm64"
+      ],
+      "dev": true,
+      "license": "Apache-2.0",
+      "optional": true,
+      "os": [
+        "netbsd"
+      ],
+      "engines": {
+        "node": ">=16.20.0"
+      }
+    },
+    "node_modules/@typescript/typescript-netbsd-x64": {
+      "version": "7.0.2",
+      "resolved": "https://registry.npmjs.org/@typescript/typescript-netbsd-x64/-/typescript-netbsd-x64-7.0.2.tgz",
+      "integrity": "sha512-8YIT0EHM/3dq10ZOVF/A7pc/YSMtbcecct4rWtexrnSCHOPcpC2KTLXfTCR6vDpnSiY12heNb1GiN/wu+T/FyA==",
+      "cpu": [
+        "x64"
+      ],
+      "dev": true,
+      "license": "Apache-2.0",
+      "optional": true,
+      "os": [
+        "netbsd"
+      ],
+      "engines": {
+        "node": ">=16.20.0"
+      }
+    },
+    "node_modules/@typescript/typescript-openbsd-arm64": {
+      "version": "7.0.2",
+      "resolved": "https://registry.npmjs.org/@typescript/typescript-openbsd-arm64/-/typescript-openbsd-arm64-7.0.2.tgz",
+      "integrity": "sha512-APT8+ClYnuYm1u9+kgGXoMj2VzWzcymwh2gNSQVySHfkRDGOTVkoWLjCmOQSaO+PoqQ57B0flRp9SA+7GnnkzQ==",
+      "cpu": [
+        "arm64"
+      ],
+      "dev": true,
+      "license": "Apache-2.0",
+      "optional": true,
+      "os": [
+        "openbsd"
+      ],
+      "engines": {
+        "node": ">=16.20.0"
+      }
+    },
+    "node_modules/@typescript/typescript-openbsd-x64": {
+      "version": "7.0.2",
+      "resolved": "https://registry.npmjs.org/@typescript/typescript-openbsd-x64/-/typescript-openbsd-x64-7.0.2.tgz",
+      "integrity": "sha512-yX7s+Q0Dln0Dt9tEzZsAjXXR/+ytBM7AlglaqyeMPxQszJ1JhlJdZ6jLA+IzldHtflX81em7lDao1xXu+aRRkg==",
+      "cpu": [
+        "x64"
+      ],
+      "dev": true,
+      "license": "Apache-2.0",
+      "optional": true,
+      "os": [
+        "openbsd"
+      ],
+      "engines": {
+        "node": ">=16.20.0"
+      }
+    },
+    "node_modules/@typescript/typescript-sunos-x64": {
+      "version": "7.0.2",
+      "resolved": "https://registry.npmjs.org/@typescript/typescript-sunos-x64/-/typescript-sunos-x64-7.0.2.tgz",
+      "integrity": "sha512-dLJDGaLZ1D4HPQn62u1n8mBDkJREwMsAkCdkwd4Ieqw+x3TUyTsqY0YiBCtE6H6OzzgGk3iuZ3vFWRS+E8/d1g==",
+      "cpu": [
+        "x64"
+      ],
+      "dev": true,
+      "license": "Apache-2.0",
+      "optional": true,
+      "os": [
+        "sunos"
+      ],
+      "engines": {
+        "node": ">=16.20.0"
+      }
+    },
+    "node_modules/@typescript/typescript-win32-arm64": {
+      "version": "7.0.2",
+      "resolved": "https://registry.npmjs.org/@typescript/typescript-win32-arm64/-/typescript-win32-arm64-7.0.2.tgz",
+      "integrity": "sha512-Gyl1Vy6OsWesLzmq+EP0Fb7b4Nid5232AvcA2SFcdYreldpNtYFFofPjnt62y9hQy7VTaZp65ICJjuAQRaVcIQ==",
+      "cpu": [
+        "arm64"
+      ],
+      "dev": true,
+      "license": "Apache-2.0",
+      "optional": true,
+      "os": [
+        "win32"
+      ],
+      "engines": {
+        "node": ">=16.20.0"
+      }
+    },
+    "node_modules/@typescript/typescript-win32-x64": {
+      "version": "7.0.2",
+      "resolved": "https://registry.npmjs.org/@typescript/typescript-win32-x64/-/typescript-win32-x64-7.0.2.tgz",
+      "integrity": "sha512-0BQ3HkAHHlKLSp1qRvf3SUhGpGsDuhB/jgFw75guyqbxJqEaS0Cw/VFO8i2nHglJUzQCRtMMR/IBAKE3ETMC4g==",
+      "cpu": [
+        "x64"
+      ],
+      "dev": true,
+      "license": "Apache-2.0",
+      "optional": true,
+      "os": [
+        "win32"
+      ],
+      "engines": {
+        "node": ">=16.20.0"
+      }
+    },
     "node_modules/@vitest/expect": {
       "version": "3.2.6",
       "resolved": "https://registry.npmjs.org/@vitest/expect/-/expect-3.2.6.tgz",
@@ -5308,6 +5649,41 @@
         "url": "https://github.com/sponsors/ljharb"
       }
     },
+    "node_modules/typescript": {
+      "version": "7.0.2",
+      "resolved": "https://registry.npmjs.org/typescript/-/typescript-7.0.2.tgz",
+      "integrity": "sha512-8FYau96o3NKOhbjKi/qNvG/W5jhzxkbdm5sj9AbZ/5T5sWqn3hJgLfGx27sRKZWTvyzCP8dLRBTf5tBTSRVUNA==",
+      "dev": true,
+      "license": "Apache-2.0",
+      "bin": {
+        "tsc": "bin/tsc"
+      },
+      "engines": {
+        "node": ">=16.20.0"
+      },
+      "optionalDependencies": {
+        "@typescript/typescript-aix-ppc64": "7.0.2",
+        "@typescript/typescript-darwin-arm64": "7.0.2",
+        "@typescript/typescript-darwin-x64": "7.0.2",
+        "@typescript/typescript-freebsd-arm64": "7.0.2",
+        "@typescript/typescript-freebsd-x64": "7.0.2",
+        "@typescript/typescript-linux-arm": "7.0.2",
+        "@typescript/typescript-linux-arm64": "7.0.2",
+        "@typescript/typescript-linux-loong64": "7.0.2",
+        "@typescript/typescript-linux-mips64el": "7.0.2",
+        "@typescript/typescript-linux-ppc64": "7.0.2",
+        "@typescript/typescript-linux-riscv64": "7.0.2",
+        "@typescript/typescript-linux-s390x": "7.0.2",
+        "@typescript/typescript-linux-x64": "7.0.2",
+        "@typescript/typescript-netbsd-arm64": "7.0.2",
+        "@typescript/typescript-netbsd-x64": "7.0.2",
+        "@typescript/typescript-openbsd-arm64": "7.0.2",
+        "@typescript/typescript-openbsd-x64": "7.0.2",
+        "@typescript/typescript-sunos-x64": "7.0.2",
+        "@typescript/typescript-win32-arm64": "7.0.2",
+        "@typescript/typescript-win32-x64": "7.0.2"
+      }
+    },
     "node_modules/unbox-primitive": {
       "version": "1.1.0",
       "resolved": "https://registry.npmjs.org/unbox-primitive/-/unbox-primitive-1.1.0.tgz",
diff --git a/engine/web/package.json b/engine/web/package.json
index 0f9f498..8a5b834 100644
--- a/engine/web/package.json
+++ b/engine/web/package.json
@@ -8,6 +8,7 @@
   "scripts": {
     "build": "node build.mjs",
     "lint": "eslint .",
+    "typecheck": "tsc --noEmit",
     "test": "vitest run"
   },
   "devDependencies": {
@@ -21,6 +22,7 @@
     "globals": "17.7.0",
     "jsdom": "^25.0.1",
     "preact": "10.29.7",
+    "typescript": "7.0.2",
     "vitest": "^3.2.6",
     "vitest-axe": "0.1.0"
   }
diff --git a/engine/web/src/admission/signing.jsx b/engine/web/src/admission/signing.jsx
index fd8c0b6..4e8b47f 100644
--- a/engine/web/src/admission/signing.jsx
+++ b/engine/web/src/admission/signing.jsx
@@ -115,7 +115,7 @@ function useRowDisclosure(domId, label) {
     <button
       class="expander"
       type="button"
-      aria-expanded={String(open)}
+      aria-expanded={open}
       aria-controls={detailId}
       aria-label={label}
       onClick={() => setOpen((v) => !v)}
@@ -271,13 +271,13 @@ function baselineWord(established) {
  * @param {string} props.headClass  the CSS prefix (`signing-regression` | `signing-exception`).
  * @param {string} props.rowClass  the summary `<tr>` class (loud attention vs calm).
  * @param {Record<string,string>} props.dataAttr  the single `data-*` attribute (fixed token).
- * @param {string} [props.role]  `"alert"` for the loud banners, omitted for the calm exception.
+ * @param {"alert"} [props.role]  `"alert"` for the loud banners, omitted for the calm exception.
  * @param {string} props.glyph  the leading glyph.
  * @param {any} props.head  the headline word content (inside `{headClass}-word`).
  * @param {boolean} props.established  drives the sibling baseline-strength phrase.
  * @param {string} props.image  the untrusted image ref (rendered as JSX text).
  * @param {string} props.label  the expander's aria-label.
- * @param {(open: boolean) => any} props.detail  renders the detail body when open.
+ * @param {() => any} props.detail  renders the detail body when open.
  */
 function BannerRow({
   domId,
@@ -304,7 +304,7 @@ function BannerRow({
         {...dataAttr}
       >
         <td class="cell cell-expand">{expander}</td>
-        <td class="cell cell-regression" colspan="6">
+        <td class="cell cell-regression" colspan={6}>
           <span class={`${headClass}-head`}>
             <span class="glyph" aria-hidden="true">
               {glyph}
@@ -319,7 +319,7 @@ function BannerRow({
         </td>
       </tr>
       <tr class="row-detail" id={detailId} data-detail-for={domId}>
-        <td class="detail-host" colspan="7">
+        <td class="detail-host" colspan={7}>
           {open ? detail() : null}
         </td>
       </tr>
diff --git a/engine/web/src/findings/evidence.jsx b/engine/web/src/findings/evidence.jsx
index 0542b7e..4e9ca34 100644
--- a/engine/web/src/findings/evidence.jsx
+++ b/engine/web/src/findings/evidence.jsx
@@ -82,7 +82,7 @@ function CveRow({ c }) {
       </tr>
       {c.title ? (
         <tr class="ev-subrow">
-          <td colspan="7">
+          <td colspan={7}>
             <span class="muted">{c.title}</span>
           </td>
         </tr>
diff --git a/engine/web/src/findings/row.jsx b/engine/web/src/findings/row.jsx
index 49cb48b..efa0743 100644
--- a/engine/web/src/findings/row.jsx
+++ b/engine/web/src/findings/row.jsx
@@ -35,7 +35,7 @@ export function FindingRow({ f }) {
           <button
             class="expander"
             type="button"
-            aria-expanded={String(expanded)}
+            aria-expanded={expanded}
             aria-controls={detailId}
             aria-label="expand finding detail"
           >
@@ -64,7 +64,7 @@ export function FindingRow({ f }) {
         </td>
       </tr>
       <tr class="row-detail" id={detailId} data-detail-for={f.id}>
-        <td class="detail-host" colspan="7">
+        <td class="detail-host" colspan={7}>
           {expanded ? <DetailPanel f={f} /> : null}
         </td>
       </tr>
diff --git a/engine/web/jsconfig.json b/engine/web/tsconfig.json
similarity index 63%
rename from engine/web/jsconfig.json
rename to engine/web/tsconfig.json
index 702126b..0aa9824 100644
--- a/engine/web/jsconfig.json
+++ b/engine/web/tsconfig.json
@@ -1,14 +1,17 @@
 {
   "compilerOptions": {
+    "allowJs": true,
+    "checkJs": true,
     "jsx": "react-jsx",
     "jsxImportSource": "preact",
     "module": "esnext",
     "moduleResolution": "bundler",
     "target": "es2020",
     "lib": ["es2020", "dom", "dom.iterable"],
-    "checkJs": false,
     "noEmit": true,
-    "strict": false
+    "strict": false,
+    "noUnusedLocals": true,
+    "skipLibCheck": true
   },
-  "include": ["src", "test", "build.mjs", "vitest.config.js"]
+  "include": ["src"]
 }