From 0cbaeadc665dee6aaf9508a93a4b6d6f751663db Mon Sep 17 00:00:00 2001
From: Garry Tan <garrytan@gmail.com>
Date: Sun, 16 Aug 2026 09:43:46 -0700
Subject: [PATCH] feat(browse): allow Emulation.setEmulatedMedia on the CDP
 allowlist (re-derived from #2419)
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Adds Emulation.setEmulatedMedia to the deny-default CDP allowlist:
tab-scoped, trusted output (returns an empty result — no page content).
Unlocks media type/feature overrides (prefers-color-scheme,
prefers-reduced-motion, prefers-contrast, forced-colors) via `$B cdp`, so
dark-mode and a11y CSS branches are testable without a headed toggle. Like
setUserAgentOverride, the override persists on the tab until cleared with
an empty features array — noted in the entry's justification.

Registry test pins the entry (allowed + tab scope + trusted output); the
PR's VERSION/CHANGELOG stamping is stripped per wave convention (versioning
happens at /ship).

Tests: cdp-allowlist 7 pass, 0 fail.

Re-derived from PR #2419 by @meshailabs.

Co-authored-by: meshailabs <devsupport@meshai.dev>
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
---
 browse/src/cdp-allowlist.ts       |  7 +++++++
 browse/test/cdp-allowlist.test.ts | 12 ++++++++++++
 2 files changed, 19 insertions(+)

diff --git a/browse/src/cdp-allowlist.ts b/browse/src/cdp-allowlist.ts
index b9c3a9538..9e1f9f655 100644
--- a/browse/src/cdp-allowlist.ts
+++ b/browse/src/cdp-allowlist.ts
@@ -155,6 +155,13 @@ export const CDP_ALLOWLIST: ReadonlyArray<CdpAllowEntry> = Object.freeze([
     output: 'trusted',
     justification: 'UA override on the active tab. NOTE: changes affect future requests; fine for tests.',
   },
+  {
+    domain: 'Emulation',
+    method: 'setEmulatedMedia',
+    scope: 'tab',
+    output: 'trusted',
+    justification: 'Media type/feature override (prefers-color-scheme, prefers-reduced-motion, prefers-contrast, forced-colors) so a11y and dark-mode CSS branches are testable. Returns an empty result; no page content. NOTE: like setUserAgentOverride the override persists on the tab until cleared with an empty features array.',
+  },
   // ─── Page capture (output, not navigation) ─────────────────
   {
     domain: 'Page',
diff --git a/browse/test/cdp-allowlist.test.ts b/browse/test/cdp-allowlist.test.ts
index 8c80b2cdd..73d339f23 100644
--- a/browse/test/cdp-allowlist.test.ts
+++ b/browse/test/cdp-allowlist.test.ts
@@ -70,6 +70,18 @@ describe('CDP allowlist (T2: deny-default)', () => {
     expect(isCdpMethodAllowed('Page.captureScreenshot')).toBe(true);
   });
 
+  it('Emulation.setEmulatedMedia is allowed, tab-scoped, trusted (#2419)', () => {
+    // Media type/feature override (prefers-color-scheme, prefers-reduced-motion,
+    // prefers-contrast, forced-colors) so a11y and dark-mode CSS branches are
+    // testable via $B cdp. Returns an empty result — no page content, so
+    // trusted output is correct.
+    expect(isCdpMethodAllowed('Emulation.setEmulatedMedia')).toBe(true);
+    const e = lookupCdpMethod('Emulation.setEmulatedMedia');
+    expect(e).not.toBeNull();
+    expect(e!.scope).toBe('tab');
+    expect(e!.output).toBe('trusted');
+  });
+
   it('untrusted-output methods cover the read-everything-attacker-controlled cases', () => {
     // Anything that reads attacker-controlled strings (DOM/AX/CSS selectors)
     // should be tagged untrusted so the envelope wraps the result.