MCP tool fails with "JSON parsing failed: Unexpected end of JSON input" — client parses incomplete SSE chunks

Description

All calls to an MCP tool I have fails with:

JSON parsing failed: Unexpected end of JSON input
Smaller tools on the same server work fine.

Root Cause
The opencode MCP HTTP/SSE client appears to call JSON.parse() on each incoming TCP chunk individually, rather than buffering the full SSE frame before parsing.

• Small responses (<1KB) arrive in a single chunk → work fine
• Larger responses (8KB+, even for minimal queries) arrive across multiple chunked transfer-encoding chunks → each chunk is parsed individually → fails

Server-Side Confirmed Healthy

• Server logs show every search_emails call completing successfully (IsError=False, 40–480ms)
  Direct HTTP replay against the server (POST /mcp) returns valid, complete JSON for all queries, including max page size (61KB)
• Works correctly in Claude Code on the same server

Expected Behavior
Buffer incoming bytes per SSE event and only parse once the full data: payload has been received (terminated by \n\n), not per-TCP-read.

Environment

• opencode Desktop version: 1.14.48
• Transport: Streamable HTTP (SSE)

Plugins

No response

OpenCode version

Version is 1.14.48

Steps to reproduce

No response

Screenshot and/or share link

No response

Operating System

Mac OS Taheo

Terminal

No response