Session::write_output (and refuse_export) is the one place that checks; Save Frame As
(PNG/PSD/EXR), Export Lottie, Save a Copy (+XML), Collect Files, Export Timeline (and its
pre-rendered movies), Export Template, Save Animation Preset, Export Guides and Export
Shortcuts write through it. The control channel's render.frame/ui.screenshot, MCP
render_frame and CLI render-frame --out check first (new query file.checkOutput for the
bridged cases). Save/Save As/auto-save are untouched.
Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>