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fix: do not override user agent when nothing is emulated (#15274) #3539

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Merged
kblok merged 1 commit into from
Aug 5, 2026
Merged

fix: do not override user agent when nothing is emulated (#15274) #3539

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33 changes: 33 additions & 0 deletions lib/PuppeteerSharp.Tests/NetworkManagerTests/NetworkManagerTests.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -810,6 +810,39 @@ public async Task ShouldHandleCachedRedirects()
Assert.That(responses.Select(response => response.Status), Is.EqualTo(new[] { HttpStatusCode.OK, HttpStatusCode.Found, HttpStatusCode.OK }));
}

[Test, PuppeteerTest("NetworkManager.test.ts", "NetworkManager", "should not override the user agent when nothing is emulated")]
public async Task ShouldNotOverrideTheUserAgentWhenNothingIsEmulated()
{
var client = Substitute.For<ICDPSession>();

using var loggerFactory = new LoggerFactory();
var manager = CreateNetworkManager(loggerFactory);

await manager.AddClientAsync(client);
await client.DidNotReceive().SendAsync("Network.setUserAgentOverride", Arg.Any<NetworkSetUserAgentOverrideRequest>(), Arg.Any<bool>(), Arg.Any<CommandOptions>());

await manager.SetUserAgentAsync("custom-user-agent", null);
await client.Received(1).SendAsync("Network.setUserAgentOverride", Arg.Any<NetworkSetUserAgentOverrideRequest>(), Arg.Any<bool>(), Arg.Any<CommandOptions>());
}

[Test, PuppeteerTest("NetworkManager.test.ts", "NetworkManager", "should reset the override when the emulated accept-language is cleared")]
public async Task ShouldResetTheOverrideWhenTheEmulatedAcceptLanguageIsCleared()
{
var client = Substitute.For<ICDPSession>();

using var loggerFactory = new LoggerFactory();
var manager = CreateNetworkManager(loggerFactory);

await manager.AddClientAsync(client);
await client.DidNotReceive().SendAsync("Network.setUserAgentOverride", Arg.Any<NetworkSetUserAgentOverrideRequest>(), Arg.Any<bool>(), Arg.Any<CommandOptions>());

await manager.SetAcceptLanguageAsync("fr-FR");
await client.Received(1).SendAsync("Network.setUserAgentOverride", Arg.Any<NetworkSetUserAgentOverrideRequest>(), Arg.Any<bool>(), Arg.Any<CommandOptions>());

await manager.SetAcceptLanguageAsync(null);
await client.Received(2).SendAsync("Network.setUserAgentOverride", Arg.Any<NetworkSetUserAgentOverrideRequest>(), Arg.Any<bool>(), Arg.Any<CommandOptions>());
}

[Test, PuppeteerTest("NetworkManager.test.ts", "NetworkManager error handling", "should not throw on target close error")]
public async Task ShouldNotThrowOnTargetCloseError()
{
Expand Down
13 changes: 13 additions & 0 deletions lib/PuppeteerSharp/Cdp/NetworkManager.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -31,6 +31,7 @@ internal class NetworkManager
private UserAgentMetadata _userAgentMetadata;
private string _platform;
private string _acceptLanguage;
private bool _userAgentOverrideApplied;

/// <summary>
/// Initializes a new instance of the <see cref="NetworkManager"/> class.
Expand Down Expand Up @@ -639,6 +640,17 @@ private void PatchRequestEventHeaders(RequestWillBeSentResponse requestWillBeSen

private async Task ApplyUserAgentAsync(ICDPSession client)
{
var nothingToEmulate = _userAgent == null &&
_userAgentMetadata == null &&
_acceptLanguage == null &&
_platform == null;

// Still need to send once to reset a previously-applied override.
if (nothingToEmulate && !_userAgentOverrideApplied)
{
return;
}

var userAgent = _userAgent ?? await _frameManager.Page.Browser.GetUserAgentAsync().ConfigureAwait(false);
if (userAgent == null)
{
Expand All @@ -656,6 +668,7 @@ await client.SendAsync(
UserAgentMetadata = _userAgentMetadata,
Platform = _platform,
}).ConfigureAwait(false);
_userAgentOverrideApplied = !nothingToEmulate;
}
catch (Exception ex) when (CanIgnoreError(ex))
{
Expand Down
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