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mcp: on macOS and Linux the server warns that every tool will fail, though the tools work #1357
Description
Activity
Still reproduces on
apps/integration-0.1.9(2026-10-08), and two external evaluations reported it independently on 0.1.8.Reproduction (macOS): start
axiomcode mcp, sendinitialize: the server answers, and stderr saysaxiomcode mcp: AXIOMCODE_BASH is set to bash, which does not exist. The server starts, but every tool will say it cannot run the CLI.Cause, confirmed:
bin/axiomcode.jsexportsAXIOMCODE_BASH=bash(the bare namefindBash()returns on POSIX);mcp/launch.jscallsfindBash()again, which checks the override withfs.existsSync, a file-path test, so a program name always "does not exist".Fix: a bare name is resolved on PATH; a path is checked as written; either one missing remains an error (exit 127). Regression test in
tests/mcp.pyfails on the current code with the reported message and passes with the fix. PR to follow.
On macOS and Linux,
axiomcode mcpalways prints this warning to stderr:The warning is false:
tools/callreturns correct answers. An MCP client that shows server stderr tells the user the tools are broken when they work.Cause. On a non-Windows platform
findBash()returns the bare namebash, andbin/axiomcode.jsexports it asAXIOMCODE_BASH=bash.axiomcode mcpthen goes throughmcp/launch.js, which callsfindBash()again. It sees the override and checksfs.existsSync("bash"), which is resolved against the working directory, so the check fails.server.pystill inheritsAXIOMCODE_BASH=bashand runs normally.Fix. Test for existence only when the override is a path, or have
bin/axiomcode.jsexportAXIOMCODE_BASHonly when it holds an absolute path.Found by an end-to-end run of 0.1.1 on macOS and Linux. Windows is not affected, because there the value is an absolute path.