[DEBUG] MCP server "plugin:<RedactedPlugin>:data-concierge": Connection error: SSE stream disconnected: Error: ZstdDecompressionError fetching "https://ddr-<RedactedPlugin>mcp.dev.sp.<RedactedDomain>.com/mcp"

★ Insight ───────────────────────────────────── The <RedactedPlugin> MCP server uses Server-Sent Events (SSE) for its transport. The SSE HTTP response from ddr-<RedactedPlugin>mcp.dev.sp.<RedactedDomain>.com is served with Content-Encoding: zstd. Node.js's fetch API (bundled in the claude binary) decompresses it transparently — but when the long-lived SSE connection drops mid-stream, it's holding a partial Zstd frame that can't be completed, hence ZstdDecompressionError. This is a server-side issue: the <RedactedPlugin> MCP server should either use plain/gzip encoding for SSE, or the client should handle partial-frame disconnects gracefully. ─────────────────────────────────────────────────

The culprit is the <RedactedPlugin> MCP server at ddr-<RedactedPlugin>mcp.dev.sp.<RedactedDomain>.com. Its SSE stream uses Zstd compression, and when the connection drops (which SSE connections do periodically), the partial compressed frame triggers the error.

This is not something you can fix locally — it's a server-side or Claude Code client-side issue. Options:

1. Short term: Disable the <RedactedPlugin> MCP server to stop the errors:

In /mcp, disable plugin:<RedactedPlugin>:data-concierge

1. Report it: File at https://github.com/anthropics/claude-code/issues — Claude Code's SSE client should catch ZstdDecompressionError on disconnect and treat it as a clean reconnect rather than a visible error.

TL;DR

Disable the problematic MCP server or report the issue to improve Claude Code's SSE client to handle ZstdDecompressionError on disconnect.

Guidance

• Identify and disable the MCP server causing the issue, specifically the one using Zstd compression, by disabling plugin:<RedactedPlugin>:data-concierge in /mcp.
• Report the issue to the Claude Code developers to request an improvement in handling ZstdDecompressionError on disconnect, allowing for a clean reconnect instead of displaying an error.
• Verify the issue by creating an MCP server or plugin with Zstd compression and disconnecting it while Claude is reading from it to see if the error persists.
• Consider using plain or gzip encoding for SSE streams as an alternative to Zstd compression to avoid this issue.

Notes

The provided solution is a temporary workaround, and a long-term fix would require changes to the Claude Code client or the MCP server to handle partial-frame disconnects more robustly.

Recommendation

Apply workaround: Disable the problematic MCP server until a fix is available, as this is a server-side or client-side issue that cannot be resolved locally.