Patch release. Hardens the shell-exec surface to clear AgentScore advisory AGENTSCORE-2026-0016 (90→80, LOW→MODERATE).

Why this exists

AgentScore flagged v4.2.0 for command_injection: shell execution with template literal input. Two surfaces matched:

| File | Line | Variable | Source |
|---|---|---|---|
| scripts/token-cli.js | 146-147 | KEYCHAIN_SERVICE | Hardcoded "slack-mcp-server" (lib/token-store.js:18) |
| lib/handlers.js | 58 | tempPath | Internal cache/token path + PID |

Both are static-analysis false positives — every variable inside the template literals is a hardcoded internal constant. No untrusted input flows in. AgentScore is pattern-matching execSync(template-literal) without taint analysis.

We're shipping the fix anyway because eliminating the pattern entirely is cheap (~14 lines) and forward-proof: any future refactor that accidentally introduces user-controlled input into these paths can't regress into a real injection.

What changed

• lib/handlers.js — atomicWriteSync() POSIX permission tightening drops the subprocess entirely. execSync(\chmod 600 "${tempPath}"`)→chmodSync(tempPath, 0o600). Pure-node fs API, no shell context, no template literal. child_process` import removed from the file.

• scripts/token-cli.js — clearTokens() keychain delete now uses argv-array spawnSync. execSync(\security delete-generic-password -s "${KEYCHAIN_SERVICE}" -a "token"`)→spawnSync("security", ["delete-generic-password", "-s", KEYCHAIN_SERVICE, "-a", "token"])`. Argv form bypasses shell parsing entirely.

Verification

After install:

```bash
npm view @jtalk22/[email protected] version

4.2.2

```

Code-level:

• 0 execSync calls in any file shipped to npm (per package.json files field)
• 0 template literals as command argument to spawn/spawnSync
• AgentScore re-scan should return score to ≥90 (LOW)

No functional changes

The 21-tool surface is identical. Token clear behavior, atomic write behavior, file permissions — all preserved. The only change is how the subprocess work happens.

Links

• v4.2.0 release — feature release (workflow primitives + paid stubs + 6 templates)
• v4.2.1 release — honesty patch (npm description + Honest tradeoff rewrite)
• npm: https://www.npmjs.com/package/@jtalk22/slack-mcp