[BUG] Remote Control fails with "Session creation failed" from VS Code sidebar only (regression, extension v2.1.212)

Preflight Checklist

• [x] I have searched existing issues and this hasn't been reported yet
• [x] This is a single bug report (please file separate reports for different bugs)
• [x] I am using the latest version of Claude Code

What's Wrong?

Running /remote-control in the Claude Code VS Code sidebar fails with "Remote Control failed to connect: Session creation failed — see debug log." No debug log is ever created for the failed attempt — checked both ~/.claude/debug/ (empty) and /tmp/claude-501/<project>/<session>/scratchpad/ (empty), so the actual cause is unrecoverable from the documented logging path.

What Should Happen?

/remote-control in the VS Code sidebar should connect successfully, the same way claude remote-control does from a plain terminal in the identical project directory with the identical account. Worked in the past.

Error Messages/Logs

Remote Control failed to connect: Session creation failed — see debug log
(VS Code Output panel → "Claude Code" channel shows the same message, no additional detail.)

Steps to Reproduce

Open a project in VS Code with the Claude Code extension (v2.1.212) installed
Open the Claude Code sidebar chat panel
Type /remote-control
Observe: "Connecting to claude.ai/..." briefly, then fails with "Session creation failed — see debug log"
Compare: run claude remote-control from a terminal in the same project directory → connects successfully, session shown as connected, real bridge log written to /tmp/claude-501/.../bridge-session-<id>.log

Claude Model

Not sure / Multiple models

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

2.1.212 (Claude Code)

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

VS Code integrated terminal

Additional Information

Ruled out: CLAUDE_CODE_DISABLE_NONESSENTIAL_TRAFFIC, DISABLE_TELEMETRY, CLAUDE_CODE_USE_BEDROCK/VERTEX/FOUNDRY, and ANTHROPIC_BASE_URL are all unset. ~/.claude.json → oauthAccount has a valid accountUuid and organizationUuid. Not a proxy/gateway issue.