[rudycelekli]

Bug

Stdio upstreams are launched as $SHELL -l -c "<joined command>" (shellwrap.WrapWithUserShell). Each argument goes through Shellescape, but the POSIX branch only quotes when the argument contains one of " \t\n\r\"'\\$;&|<>(){}[]?*~", and #is not in that set. A word that begins with#starts a comment insh/bash/zsh -c`, so the shell silently drops that argument and everything after it.

Trigger

{"name": "slack", "command": "npx", "args": ["-y", "slack-mcp", "#general", "--port", "3000"]}

The shell runs npx -y slack-mcp. #general --port 3000 never reaches the child.

Fix

Add # to the POSIX special-character set, so such arguments are single-quoted like every other metacharacter. The POSIX escaper copy in internal/oauth/spawnargv_round2_test.go is updated to match, since TestPosixShellescape_MatchesProduction pins the two together.

Test

TestShellescape_HashSurvivesShell checks that #general is quoted, then runs sh -c "printf '%s\n' <escaped args>" and asserts that all four arguments (#general --port 3000 a#b) come back unchanged.

Commands run

• CGO_ENABLED=0 go test -count=1 ./internal/shellwrap: ok
• CGO_ENABLED=0 go test -count=1 ./internal/oauth: ok
• CGO_ENABLED=0 go test -count=1 -run 'Shell|Wrap|Escape|Docker' ./internal/upstream/core: ok
• With the fix reverted (git stash of shellwrap.go), -run HashSurvives fails: it expected '#general' but got #general, and the shell output came back as [""].
• gofmt -l on the edited files: no output

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[Dumbris]

Verified: the PR test fails on main for the reason described and passes on this branch merged with main; race tests for the touched packages and CI lint (bare and server tags) are clean. Also built and tested together with the rest of this batch, independently reviewed, and cross-reviewed with a second model.

[Dumbris]

Merged. Thank you, @rudycelekli! An argument starting with # is no longer swallowed as a comment by the login shell.