Install @anthropic-ai/claude-code@2.1.306 into an isolated directory using npm install --ignore-scripts --omit=optional. Confirm its --version fails with Error: claude native binary not installed. Apply scenario-setup.patch to the runner checkout and export CLAUDE_REPRO_BIN as the absolute path to that installed wrapper. Place claude-version-stderr.e2e.ts in scripts/scenarios and run scenarios:prove with the base and head commits. The fixture enables Claude and supplies a PATH shim named claude-repro. All other providers stay disabled. No real model turn runs.