Reported issues for pmcp

Pod holds 6 of 6 problems reported by people outside the maintainer team. Issues filed by the project's own owners, members and collaborators are excluded entirely — a maintainer's release checklist is not a warning to a prospective user.

Back to pmcp.

Most discussed

StdioTransport: stdin EOF disables stdout, dropping responses to already-accepted requests

Summary

StdioTransport uses a single closed flag for two independent streams. Reaching EOF on stdin sets it, and send() then refuses every stdout write. A client that pipes a batch of requests and closes stdin — the normal shape of a one-shot MCP session — never receives the responses to requests the server already accepted and answered.

Where

src/shared/stdio.rs (v2.17.0):


[Read the thread](https://github.com/paiml/rust-mcp-sdk/issues/316) · 2026-07-31 · closed · outside contributor · 0 comments

### wasm support for pmcp-macros

Love that this project supports webassembly though I notice that the [`WasmMcpServer` uses `WasmTool`, `WasmResource` and `WasmPrompt`](https://github.com/paiml/rust-mcp-sdk/blob/9edc4b4974c02f00d7b7d097a03aa401271db8ae/src/server/wasm_server.rs#L328-L358) rather than [`ToolHandler`, `PromptHandler` and `ResourceHandler`](https://github.com/paiml/rust-mcp-sdk/blob/9edc4b4974c02f00d7b7d097a03aa401271db8ae/src/server/mod.rs#L221-L270). I've not spent a ton of time digging into the macro generation

[Read the thread](https://github.com/paiml/rust-mcp-sdk/issues/278) · 2026-06-11 · open · external user · 0 comments

### fix: .cargo/config.toml has local /mnt/zram/targets path — breaks CI

## Bug

All CI jobs fail with:

error: failed to create directory /mnt/zram/targets — Permission denied (os error 13)


`.cargo/config.toml` has `target-dir = "/mnt/zram/targets"` committed, which only exists on a local dev machine.

## Five-Whys

1. **Why permission denied?** `/mnt/zram/targets` doesn't exist on GitHub runners.
2. **Why is Cargo using that path?** `.cargo/config.toml` sets `target-dir`.
3. **Why is a local path in the repo?** Developer's zram ramdisk config was committed.

[Read the thread](https://github.com/paiml/rust-mcp-sdk/issues/222) · 2026-04-05 · closed · outside contributor · 1 comment

### Stdio Transport Non-Compliance with MCP Specification

The stdio transport implementation uses HTTP-style Content-Length header framing instead of the newline-delimited JSON-RPC messages required by the MCP specification. This causes incompatibility with standard MCP clients.

The specification is exacting here:

Messages are individual JSON-RPC requests, notifications, or responses. Messages are delimited by newlines, and MUST NOT contain embedded newlines.

The server MUST NOT write anything to its stdout that is not a valid MCP message. The

Read the thread · 2026-01-15 · closed · outside contributor · 1 comment

Stdio example not working

Try example from README.md in the project root. Server started but not respond.

Read the thread · 2025-11-27 · open · external user · 0 comments

Bug: ToolResult not exported from pmcp crate root

Bug Report: ToolResult not exported from pmcp crate root

Summary

The ToolResult enum is not accessible when importing from pmcp crate root, despite being referenced in working examples and documentation. This prevents proper MCP tool implementation when following the documented patterns.

Environment

pmcp version: 1.3.0 (also tested with 1.2.0)
Rust version: 1.89.0 (2025-06-23 c24e10642)
Platform: Linux 6.8.0-79-lowlatency
Cargo features: `["full", "validat

Read the thread · 2025-09-08 · closed · outside contributor · 0 comments

Most recent

The remaining reports are on the project's issue tracker.