Summary

After bun install -g gbrain (or when gbrain is later updated), the symlink at ~/.bun/bin/gbrain points to cli.ts which lacks the executable bit. Direct execution fails with Permission denied, breaking any MCP client that invokes the symlink path directly.

Environment

• OS: Linux 6.17.13 (Debian-based, Proxmox LXC)
• bun: 1.3.12
• gbrain: 0.9.3
• MCP client: Hermes Agent (hermes_cli.main gateway)

Reproduction

$ ls -la ~/.bun/bin/gbrain
lrwxrwxrwx ... /home/eric/.bun/bin/gbrain -> ../install/global/node_modules/gbrain/src/cli.ts

$ ls -la ~/.bun/install/global/node_modules/gbrain/src/cli.ts
-rw-rw-r-- ... src/cli.ts

$ /home/eric/.bun/bin/gbrain --help
bash: /home/eric/.bun/bin/gbrain: Permission denied

cli.ts has the correct shebang (#!/usr/bin/env bun), but mode 664 lacks the x bit.

Impact

MCP clients configured per the README (command: gbrain, args: ["serve"]) fail to start the stdio server. Observed in Hermes Agent logs:

WARNING tools.mcp_tool: Failed to connect to MCP server 'gbrain' 
(command=/home/eric/.bun/bin/gbrain): [Errno 13] Permission denied

Notable behavior

The permissions get reset on every gbrain update. My logs show gbrain MCP worked for several hours on 2026-04-13, then broke the moment cli.ts was last written (during an update at 18:41), after which every subsequent restart failed. So this is not purely a first-install issue — it recurs.

Workaround

Invoking via bun run explicitly works:

bun run ~/.bun/install/global/node_modules/gbrain/src/cli.ts serve

A wrapper script that execs via bun is a functional workaround but defeats the point of the global bin entry.

Possible fixes

1. Packaging: add a postinstall in package.json that runs chmod +x src/cli.ts after install
2. bun-side: if bun link is responsible, its linking logic should preserve or set +x on shebang-bearing bin targets. (Worth confirming whether this is bun's behavior or the package's responsibility.)
3. Fallback: ship a small shell wrapper as the bin target and invoke bun run cli.ts from there

Happy to contribute a PR if you have a preferred direction.