diff --git a/e2e/claims.spec.ts b/e2e/claims.spec.ts
index 3bd2b77..d16ab37 100644
--- a/e2e/claims.spec.ts
+++ b/e2e/claims.spec.ts
@@ -142,6 +142,30 @@ test.describe('promise 2, the name check, re-derived independently', () => {
     })
   }
 
+  for (const address of [
+    'https://github.com/path@other.example',
+    'https://github.com/?email=user@other.example',
+    'https://github.com/#user@other.example',
+  ]) {
+    test(`URL authority controls the name verdict and ClientHello: ${address}`, async ({ page }) => {
+      await bootExplore(page)
+      // Establish a failing state first so a stale baseline cannot satisfy
+      // the assertions while the asynchronous refresh is still pending.
+      await page.locator('#address-input').fill('other.example')
+      await expect(page.locator('[data-verdict="promise-name"]')).toHaveAttribute('data-result', 'fail')
+      await page.locator('#address-input').fill(address)
+      const hostname = new URL(address).hostname
+      await expect(page.locator('[data-verdict="promise-name"]')).toHaveAttribute('data-result', 'pass')
+      await expect.poll(async () => {
+        const hex = await read(page, '#wire .bytes')
+        const bytes = hex.split(/\s+/).filter((t) => /^[0-9a-f]{2}$/.test(t)).map((t) => parseInt(t, 16))
+        const text = String.fromCharCode(...bytes)
+        return text.includes(hostname) && !text.includes('other.example')
+      }).toBe(true)
+      await expectClaim(page, 'sni-readable', { contains: hostname })
+    })
+  }
+
   test('a failing name check names the actual cause', async ({ page }) => {
     await bootExplore(page)
     await page.locator('#address-input').fill('evil.example')
diff --git a/src/pki/hostname.test.ts b/src/pki/hostname.test.ts
index 59ba2a1..b493b0a 100644
--- a/src/pki/hostname.test.ts
+++ b/src/pki/hostname.test.ts
@@ -58,6 +58,31 @@ describe('RFC 6125 name matching', () => {
 })
 
 describe('what the reader actually types', () => {
+  it.each([
+    'https://github.com/contact@docs.example',
+    'https://github.com/?email=user@docs.example',
+    'https://github.com/#user@docs.example',
+    'https://user:pw@github.com:443/path@other.example?email=a@b.example#c@d.example',
+    'https://other.example/path@github.com',
+    'https://other.example/?email=user@github.com',
+    'https://other.example/#user@github.com',
+  ])('matches the platform URL hostname for %s', (raw) => {
+    const expected = new URL(raw).hostname
+    expect(hostFromInput(raw)).toBe(expected)
+    expect(matchName(raw, [expected]).matched).toBe(true)
+    expect(matchName(raw, ['github.com']).matched).toBe(expected === 'github.com')
+  })
+
+  it.each([
+    'github.com/path@other.example',
+    'github.com/?email=user@other.example',
+    'github.com/#user@other.example',
+    'user:pw@github.com:443/path@other.example',
+  ])('bounds userinfo to the authority of a bare-host input: %s', (raw) => {
+    expect(hostFromInput(raw)).toBe(new URL(`https://${raw}`).hostname)
+    expect(matchName(raw, ['github.com']).matched).toBe(true)
+  })
+
   it('extracts the host from a pasted URL, the way a browser does', () => {
     for (const raw of [
       'https://github.com/',
diff --git a/src/pki/hostname.ts b/src/pki/hostname.ts
index 6ce3b95..c31093d 100644
--- a/src/pki/hostname.ts
+++ b/src/pki/hostname.ts
@@ -36,8 +36,10 @@ function normalise(name: string): string {
  * extracts the host and matches THAT. Worse, the whole URL went into the SNI
  * exhibit, so the page showed a first message no browser would ever send.
  *
- * So the input is parsed the way a browser parses it: scheme stripped, userinfo
- * dropped, port dropped, path and query dropped. What is left is compared.
+ * This is a bounded parser for scheme://authority URLs and bare-host inputs
+ * (optionally with userinfo, a port or a path). Strip the scheme, isolate the
+ * authority, then drop userinfo and the port. An @ in a path, query or fragment
+ * cannot change the host. This is not a general WHATWG URL implementation.
  * Anything that still is not a plain DNS name is refused by `isPlainDnsName`
  * rather than guessed at.
  */
@@ -46,11 +48,11 @@ export function hostFromInput(raw: string): string {
   if (s === '') return ''
   // Scheme, if any.
   s = s.replace(/^[a-z][a-z0-9+.-]*:\/\//i, '')
-  // Anything before an @ is userinfo, not a host.
+  // Path, query or fragment ends the authority BEFORE interpreting userinfo.
+  s = s.split(/[/?#]/)[0] ?? ''
+  // Only an @ inside the authority separates userinfo from the host.
   const at = s.lastIndexOf('@')
   if (at !== -1) s = s.slice(at + 1)
-  // Path, query or fragment ends the authority.
-  s = s.split(/[/?#]/)[0] ?? ''
   // A bracketed IPv6 literal is not a DNS name; leave it intact and let
   // isPlainDnsName refuse it rather than mangling it into something plausible.
   if (s.startsWith('[')) return normalise(s)