fix: suppress socat stdout in _cmux_send to prevent OK leak

[fvallenilla]

Summary

• Redirect socat stdout/stderr to /dev/null in _cmux_send for both zsh and bash shell integrations
• The ncat path uses --send-only and the nc path already redirects — the socat path was the only one leaking the socket response to the terminal

Root cause

The cmux socket responds with OK to every message. socat reads bidirectionally by default, so without output suppression it prints that response to stdout. On systems where ncat is absent but socat is installed (common on macOS via Homebrew), this causes a spurious OK to appear on every new tab, directory change, and shell prompt.

Fixes #1618

Test plan

• On a system with socat but no ncat, open a new terminal tab — no OK should appear
• Run cd /tmp && cd - — no OK should appear
• Verify sidebar still updates (pwd, git branch, PR badge) since the socket send itself is unaffected

Generated with Claude Code

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Summary by cubic

Stop the cmux socket OK from appearing in the terminal by redirecting socat stdout/stderr to /dev/null in _cmux_send for both bash and zsh. This aligns the socat path with ncat --send-only/nc and prevents stray OK on new tabs, cd, and prompts when ncat is missing.

^{Written for commit aae07c2. Summary will update on new commits.}

Summary by CodeRabbit

• Bug Fixes
  • Suppressed extraneous output from shell integration commands for a cleaner user experience.

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No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: 0a45b1ff-7b0f-4d69-99d9-bd44ecea36ed

📥 Commits

Reviewing files that changed from the base of the PR and between 8d8fadb and aae07c2.

📒 Files selected for processing (2)

• Resources/shell-integration/cmux-bash-integration.bash
• Resources/shell-integration/cmux-zsh-integration.zsh

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📝 Walkthrough

Walkthrough

Both bash and zsh shell integration scripts add output redirection to the socat fallback path in the _cmux_send function, suppressing stdout and stderr to prevent socket responses from leaking to the terminal.

Changes

Cohort / File(s)	Summary
Shell Integration Socket Transport Resources/shell-integration/cmux-bash-integration.bash, Resources/shell-integration/cmux-zsh-integration.zsh	Redirect stdout and stderr to /dev/null in socat command invocation to suppress socket response output that was previously leaked to the terminal.

Estimated code review effort

🎯 1 (Trivial) | ⏱️ ~2 minutes

Poem

🐰 Whispers the quiet rabbit to the socat stream:

Hush now, dear socket, your "OK" must not gleam,
Into /dev/null it flows, silent and clean,
No more stray output upon the bright screen!
✨

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title accurately describes the main change: suppressing socat stdout to prevent OK output leakage in the _cmux_send function.
Description check	✅ Passed	The description includes a comprehensive summary of changes and root cause, but the testing section lacks details on how the change was tested locally and which tests were added or verified.
Linked Issues check	✅ Passed	The code changes directly address issue #1618 by redirecting socat stdout/stderr to /dev/null in both shell integrations, matching the ncat and nc implementations.
Out of Scope Changes check	✅ Passed	All changes are scoped to the socat output suppression in _cmux_send for both bash and zsh integrations, directly addressing the linked issue with no extraneous modifications.
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%.

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✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

📝 Coding Plan

• Generate coding plan for human review comments

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No issues found across 2 files

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