fix(cli): write Hermes light skin over stdin on macOS

[laitingsheng]

Summary

On macOS, nemohermes connect failed to write the managed Hermes light terminal skin: the skin helper passed a multi-line shell script as a sh -c argument, and OpenShell's macOS exec rejects command arguments containing a newline or carriage return. The write and remove helpers now stream the script over stdin via sh -s, so the skin is written as intended on macOS while Linux behaviour stays unchanged.

Related Issue

Fixes #6834

Changes

• writeHermesLightSkinFile and removeHermesLightSkinFile now invoke openshell sandbox exec ... -- sh -s with the script supplied on stdin (input) and stdin piped, instead of sh -c "<multi-line script>". This mirrors the existing stdin pattern already used in tunnel/sandbox-gateway-stop.ts.
• Updated the connect-hermes-light-theme test harness helpers and mock arms to read the script from the exec stdin rather than the -c argv slot.
• Added a regression test asserting the forwarded argv is exactly sh -s, no argv element carries a newline or carriage return, and the multi-line script travels over stdin.

Type of Change

• Code change (feature, bug fix, or refactor)
• Code change with doc updates
• Doc only (prose changes, no code sample modifications)
• Doc only (includes code sample changes)

Quality Gates

• Tests added or updated for changed behavior
• Existing tests cover changed behavior — justification:
• Tests not applicable — justification:
• Docs updated for user-facing behavior changes
• Docs not applicable — justification: internal exec-transport fix; no user-facing behaviour, CLI surface, flags, or output change (the skin is written as originally intended).
• Sensitive paths changed (security, policy, credentials, preflight, onboarding, inference, runner, sandbox, or messaging)
• Sensitive-path review completed or maintainer-approved waiver recorded — reviewer/approval link/justification: transport-only change (exec argv -c → stdin sh -s); the executed script is byte-identical and still runs as the sandbox user, with no change to privileges, credentials, or network surface. Requesting maintainer sensitive-path review.
• Non-success, skipped, or missing CI check accepted by maintainer — check name, approval link, and follow-up issue:

Verification

• PR description includes the DCO sign-off declaration and every commit appears as Verified in GitHub
• Normal pre-commit, commit-msg, and pre-push hooks passed, or npm run check:diff passed when hooks were skipped or unavailable
• Targeted behavior tests pass for the current change set, or tests are marked not applicable above — command/result: npx vitest run src/lib/actions/sandbox/connect-hermes-light-theme.test.ts → 11/11 passed
• Applicable broad gate passed — npm test for broad runtime/test-harness changes; npm run check for repo-wide validation/coverage changes — command/result:
• Quality Gates section completed with required justifications or waivers
• No secrets, API keys, or credentials committed
• npm run docs builds without warnings (doc changes only)
• Doc pages follow the style guide (doc changes only)
• New doc pages include SPDX header and frontmatter (new pages only)

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Signed-off-by: Tinson Lai tinsonl@nvidia.com

Summary by CodeRabbit

• Bug Fixes
  • Improved the reliability and security of Hermes light-skin setup and cleanup operations.
  • Prevented multi-line shell scripts and sensitive values from appearing in command arguments or logs.
  • Strengthened failure handling when applying or removing the light skin, while preserving existing cleanup behavior.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

Plan: Enterprise

Run ID: 123e14dc-1841-4c19-8be9-d94ad48bf555

📥 Commits

Reviewing files that changed from the base of the PR and between 2adc848 and b83c3c4.

📒 Files selected for processing (2)

• src/lib/actions/sandbox/connect-hermes-light-skin.ts
• src/lib/actions/sandbox/connect-hermes-light-theme.test.ts

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📝 Walkthrough

Walkthrough

Hermes light-skin write and removal scripts now run through openshell stdin using sh -s. Tests inspect structured call options and verify multiline scripts are excluded from argv.

Changes

Hermes light-skin execution

Layer / File(s)	Summary
Route skin scripts through stdin src/lib/actions/sandbox/connect-hermes-light-skin.ts	Write and removal operations pass scripts through input with piped stdin while preserving existing error handling.
Validate structured openshell calls src/lib/actions/sandbox/connect-hermes-light-theme.test.ts	Tests extract scripts from call options, update cleanup mocks, and verify multiline scripts are sent through stdin rather than argv.

Estimated code review effort: 2 (Simple) | ~10 minutes

Suggested reviewers: cjagwani

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly matches the main change: writing the Hermes light skin over stdin on macOS.
Linked Issues check	✅ Passed	The PR addresses the macOS multiline-script rejection by switching to stdin and updates tests to verify the new shell input path.
Out of Scope Changes check	✅ Passed	The changes stay focused on the macOS Hermes light-skin write/remove flow and related test updates.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch fix/hermes-light-skin-macos-exec

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_{Comment @coderabbitai help to get the list of available commands.}

[github-code-quality]

Code Coverage Overview

Languages: TypeScript

TypeScript / code-coverage/plugin

The overall coverage remains at 96%, unchanged from the main branch.

TypeScript / code-coverage/cli

The overall coverage in the fix/hermes-light-ski... branch remains at 79%, unchanged from the main branch.

Show a code coverage summary of the most impacted files.

File	main 20130dd	fix/hermes-light-ski... 261e7fa	+/-
src/lib/actions...e-validation.ts	81%	83%	+2%
src/lib/adapters/http/probe.ts	94%	97%	+3%
src/lib/adapter.../docker/pull.ts	83%	86%	+3%
src/lib/onboard...eway-process.ts	90%	93%	+3%
src/lib/sandbox...rce-identity.ts	89%	94%	+5%
src/lib/onboard...shboard-port.ts	89%	94%	+5%
src/lib/messagi...l-validation.ts	70%	77%	+7%
src/lib/policy/tiers.ts	80%	94%	+14%
src/lib/onboard...licy-presets.ts	81%	100%	+19%
src/lib/hermes-dashboard.ts	63%	95%	+32%

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_{Updated July 14, 2026 17:42 UTC
Code Coverage is in Public Preview. Learn more and provide us with your feedback.}

[github-actions]

PR Review Advisor — Informational

Advisor assessment: Informational / medium confidence
Next action: No advisor follow-up needed.
Findings: 0 blockers · 0 warnings · 0 suggestions
Status: No actionable findings remain in the canonical review ledger.

Model lanes

• GPT-5.6 Terra (primary): Completed · medium confidence · 0 blockers · 0 warnings · 0 suggestions
• Nemotron 3 Ultra (second opinion): Failed

Nemotron output stays in workflow artifacts and does not change the assessment above.

E2E guidance

Advisory only. E2E / PR Gate selects and runs jobs independently.

Recommended E2E: onboard-repair, onboard-resume

1 optional E2E recommendation

• hermes-e2e

Workflow run details

This automated review informs maintainers. Warnings and suggestions do not require a response. A maintainer decides whether to merge.