Remote MCP servers require header #17713

When using remote MCP servers (e.g., Z.AI's web_search_prime), OpenCode doesn't send the required Accept header, causing requests to fail.

Error Messages

Before fix:

"message":"Accept header must include both application/json and text/event-stream"

After adding Accept header manually to config:

"message":"Session ID missing in request header"

This indicates the Accept header fix partially worked, but there's an additional issue with session management.

Affected Services

• web_search_prime from Z.AI (https://api.z.ai/api/mcp/web_search_prime/mcp)
• zread from Z.AI (https://api.z.ai/api/mcp/zread/mcp)

Expected Behavior

OpenCode should send proper headers when making requests to remote MCP servers:

1. Accept: application/json, text/event-stream for SSE streaming support
2. Proper session management headers if required by the remote server

Workaround

Adding Accept header to the remote MCP config in opencode.json partially resolves the issue, but session management still fails.

Steps to Reproduce

1. Configure a remote MCP server in opencode.json
2. Try to use any tool from that server
3. Observe empty results or error messages

Config Example

```json
"web_search_prime": {
"type": "remote",
"url": "https://api.z.ai/api/mcp/web_search_prime/mcp",
"headers": {
"Authorization": "Bearer <API_KEY>",
"Accept": "application/json, text/event-stream"
}
}
```

Environment

• OpenCode version: 1.2.27
• macOS arm64 (Apple Silicon)