Duplicate System Message Sent #1301

It seems OpenCode sends two times the system prompt at the beginning of the conversation. The second time includes the <env> information, and the first is just the provider system prompt. I have only been able to test this with Azure OpenAI models, but from the code, I would suspect to happen for everything.

This is how I found out:

1. Set up mitmproxy with uv tool install mitmproxy.
2. Start it by running mitmweb.
3. Trust the certificate
4. Run opencode like so: HTTP_PROXY=http://127.0.0.1:8080 HTTPS_PROXY=http://127.0.0.1:8080 NODE_EXTRA_CA_CERTS="$HOME/.mitmproxy/mitmproxy-ca-cert.pem" opencode

After the first message, you can see in the browser the requests intercepted by opencode. When I look at them, they look like this (trimming irrelevant stuff):

{
    "model": "gpt-4.1",
    "max_tokens": 32000,
    "temperature": 0,
    "messages": [
        {
            "role": "system",
            "content": "You are opencode..."
        },
        {
            "role": "system",
            "content": "You are opencode..."
        },
        {
            "role": "user",
            "content": "Just tell me hello"
        }
    ],
    "tools": ....
}

Checking the diffs, between these two system messages, the only difference is:

Here is some useful information about the environment you are running in:
<env>
  Working directory: /Users/bernat/.config/opencode
  Is directory a git repo: no
  Platform: darwin
  Today's date: Fri Jul 25 2025
</env>
<project>
</project>

This, as expected, is repeated for every subsequent request of the conversation

$ opencode --version
0.3.67

Suspicion

I do not know enough about the caching mechanisms, so uncertain about opening a PR. But it looks to me like this line is duplicating the functionality immediately above. After removing it, I can see how there is two system messages: the first contains whatever the system prompt is, and the second the env info. I'd assume this to be correct?

https://github.com/sst/opencode/blob/fc13d057f8eb296ec8b08cbe11b37ef65a320a39/packages/opencode/src/session/index.ts#L629