Computer Use built-in MCP missing from /mcp in one project but present in another (same account/version/launch)

Description

The built-in computer-use MCP server (listed under "Built-in MCPs (always available)" in /mcp) appears in one project directory but is completely absent from the /mcp list in another project — on the same machine, same account, same Claude Code version, and same launch command.

In Project A it shows as computer-use · ○ disabled (togglable). In Project B the row does not appear at all, so there is no way to enable it.

Environment

• Claude Code: 2.1.177
• OS: macOS 15.7.4 (Darwin 24.6.0)
• Plan: Claude Max (20x)
• Auth: claude.ai account — no third-party provider (CLAUDE_CODE_USE_VERTEX / CLAUDE_CODE_USE_BEDROCK unset; no ANTHROPIC_* provider vars)
• Launch (identical for both projects): claude --dangerously-skip-permissions --continue, in macOS Terminal.app (real TTY)

Steps to reproduce

1. In Project A, run /mcp → scroll to "Built-in MCPs (always available)" → computer-use is listed (disabled but togglable).
2. In Project B (same user / account / machine / version), run /mcp → "Built-in MCPs (always available)" section is present, but computer-use is not in the list.

What I've tried (Project B)

• Fully quit Terminal and relaunched.
• Started a fresh session without --continue (claude --dangerously-skip-permissions).
• Re-ran /login (confirmed logged into the same Max account).
• Scrolled the entire /mcp list end to end.
• Verified no provider env vars are set in the session.
• Confirmed both projects report lastVersionBase: 2.1.177 in ~/.claude.json, and both have hasCompletedProjectOnboarding: true + hasTrustDialogAccepted: true.

computer-use still never appears in Project B.

Expected

computer-use is documented as a built-in MCP that is "always available." All eligibility requirements (≥ 2.1.85, macOS, Pro/Max plan, claude.ai auth, interactive session) are met identically in both projects, so it should appear in /mcp for Project B exactly as it does for Project A.

Actual

computer-use is missing from /mcp in Project B with no way to enable it, while present in Project A under otherwise-identical conditions. The only apparent difference is the project directory.

Notes

Happy to provide additional diagnostics (relevant ~/.claude.json project entries, claude --debug output) if useful.