[FEATURE]: Allow overriding WebFetch tool’s User-Agent header

[Zohair-coder]

Feature hasn't been suggested before.

• I have verified this feature I'm about to request hasn't been suggested before.

Describe the enhancement you want to request

My organization runs behind a corporate proxy. The proxy requires Kerberos/NTLM authentication for all HTTP requests that look like they come from the browser based on the User-Agent header. It seems like the WebFetch tool sets the header to something that looks like it’s coming from a browser, which means I get a 401 response from the proxy for all of my requests made by the WebFetch tool. Please allow overriding this headers.

[github-actions]

This issue might be a duplicate of existing issues or closely related to broader feature requests. Please check:

• Opencode not respecting NO_PROXY variable #8822: Corporate proxy issue with NO_PROXY environment variable not being respected
• [FEATURE]: Is it possible to specify that certain tools use a proxy, such as websearch? These tools should be allowed to use a proxy, while others should continue to use the regular network. #7209: Feature request for tool-specific proxy configuration
• [Bug] OpenCode Crashes on Launch When http_proxy Environment Variable is Set #7155: OpenCode crashes when http_proxy environment variable is set
• OpenCode 1.1.2 ignores system proxy environment variables (HTTP_PROXY/HTTPS_PROXY) #6953: OpenCode ignores system proxy environment variables (HTTP_PROXY/HTTPS_PROXY)
• [FEATURE]: Add option to disable models.dev fetch for corporate proxy environments #4959: Request to disable models.dev fetch for corporate proxy environments
• Support HTTP_PROXY & HTTPS_PROXY for millions of users who are behind fire walls in some regions and some organizations. #531: Foundational request for HTTP_PROXY & HTTPS_PROXY support

While #9013 is specifically about overriding the User-Agent header (which is unique), the underlying issue is part of a broader pattern of corporate proxy and authentication challenges. You may want to coordinate with ongoing efforts to improve proxy and network configuration handling across OpenCode.

Feel free to ignore if your specific case is distinct from these issues.

[thdxr]

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