Adding an effect to a clip did nothing: the sequence render is flattened into a montage (decode + composite), and MontageClip carried no effect data at all. - MontageClip gains an ordered effect stack (type id / enabled / effect input / parameter values); protocol v2 carries it as an additive wire field (older peers default to an empty stack). - renderops::video_montage fills the stack from the effect chain (the footage source node — the chain end without an effect input — is dropped; the montage decodes the footage itself). Export (oak-task) and the multicam single-track montage fill it too. - The worker applies the stack between decode and composite: built-in Opacity gets a CPU evaluator (C++ opacity.frag parity — whole vec4, alpha included, unity pass-through); everything else dispatches as an OFX plugin job through a new instance-factory slot (oak-plugin lazily creates + caches one instance per identifier per render process) with the montage's parameters injected. Disabled effects bypass (the C++ traverser pushes the effect input through). Unknown types warn once per type id and pass through — no silent no-ops. Not covered (explicitly): Transform/Crop and the other ~30 built-in effects have no CPU evaluator in oak-render (they pass through with a warning), keyframed parameter animation, audio effect chains, and the CLI's simplified montage. Acceptance: a real 50% Opacity on real media quarters the rendered pixels both in-process (renderops test) and through a real worker process over IPC + shared memory (procpool_integration test); disabling restores the plain render byte-for-byte.