diff --git a/crates/gpu/src/lib.rs b/crates/gpu/src/lib.rs
index 8879ab86..4d3f6c77 100644
--- a/crates/gpu/src/lib.rs
+++ b/crates/gpu/src/lib.rs
@@ -287,6 +287,17 @@ impl Gpu {
         }
     }
 
+    /// Why a frame was not rendered (best effort: device health, else size / support).
+    fn decline_reason(&self) -> String {
+        match self.ctx.check_health() {
+            Err(e) => format!("device failure / out of memory: {e}"),
+            Ok(()) => format!(
+                "the GPU compositor did not handle the frame (unsupported content, a frame over the {} px texture limit, or an allocation failed)",
+                self.ctx.max_dim
+            ),
+        }
+    }
+
     /// Wait for submitted GPU work with the readback deadline (benchmarks).
     pub fn wait(&self) {
         let _ = self.ctx.poll_readbacks(wgpu::PollType::Wait { submission_index: None, timeout: Some(crate::readback::TIMEOUT) });
@@ -299,7 +310,13 @@ impl Accelerator for Gpu {
     }
 
     fn comp_frame(&self, r: &Renderer, comp: ItemId, t: Tick) -> Option<Image> {
-        self.render(r, comp, t)
+        let img = self.render(r, comp, t);
+        if img.is_none() {
+            // The caller renders the frame on the CPU; say so and why, or an export that falls
+            // back frame after frame (a nested comp the GPU declines) is only mysteriously slow.
+            log::warn!(target: "effectcraft_gpu", "GPU declined the frame at {:.3} s, the CPU renders it: {}", t.seconds(), self.decline_reason());
+        }
+        img
     }
 
     fn supports_effect(&self, id: &str) -> bool {
diff --git a/crates/gpu/src/tests.rs b/crates/gpu/src/tests.rs
index 39be29a9..0234f793 100644
--- a/crates/gpu/src/tests.rs
+++ b/crates/gpu/src/tests.rs
@@ -745,3 +745,43 @@ fn within_memory_returns_the_work_when_there_is_room() {
     let img = g.within_memory(|| g.ctx.image(64, 32)).expect("room for a 64×32 texture");
     assert_eq!((img.width, img.height), (64, 32));
 }
+
+/// Precomp layers (not collapsed) render their nested comp resident on the GPU
+/// (`walk::draw_precomp`): match the CPU (nested blend modes, effects inside and outside,
+/// transforms, opacity, a blend mode on the precomp layer, half resolution,
+/// two instances at different times of the same nested comp).
+#[test]
+fn nested_precomps_render_resident() {
+    for depth in [BitDepth::Bpc8, BitDepth::Bpc32] {
+        let mut s = Scene::new(depth);
+        let inner = Comp::new(60, 40, FrameRate::FPS_30, Tick::from_seconds_f64(2.0));
+        let inner_id = s.p.add_item("Inner", Label::Sandstone, None, ItemKind::Comp(inner.clone().into()));
+        {
+            let mut ins = Scene { p: std::mem::take(&mut s.p), cid: inner_id, comp: inner };
+            let mut a = ins.footage(50, 30);
+            ins.effect(&mut a, "ec.blur.gaussian", &[("blurriness", n(3.0))]);
+            ins.push(a);
+            let mut b = ins.solid([0.2, 0.7, 0.4], 30, 20);
+            b.blend_mode = BlendMode::Difference;
+            set(&mut b, "transform/rotation", Value::Scalar(15.0));
+            ins.push(b);
+            s.p = ins.p;
+        }
+        let bg = s.footage(97, 61);
+        s.push(bg);
+        let mut pre = build::layer(&mut s.p, &s.comp, "Inner", LayerSource::Comp { item: inner_id }, (60, 40), None);
+        set(&mut pre, "transform/rotation", Value::Scalar(25.0));
+        set(&mut pre, "transform/opacity", Value::Scalar(80.0));
+        s.effect(&mut pre, "ec.color.levels", &[("gamma", n(1.3))]);
+        pre.blend_mode = BlendMode::Screen;
+        s.push(pre);
+        // A second instance, later in the nested comp's time.
+        let mut pre2 = build::layer(&mut s.p, &s.comp, "Inner 2", LayerSource::Comp { item: inner_id }, (60, 40), None);
+        set(&mut pre2, "transform/position", v3(70.0, 40.0));
+        pre2.start_time = Tick::from_seconds_f64(-0.5);
+        s.push(pre2);
+        check(&format!("nested precomps {depth:?}"), compare_at(&s, opts(), Tick::from_seconds_f64(0.2)), 0.0);
+        let half = RenderOpts { scale: 0.5, ..opts() };
+        check(&format!("nested precomps half {depth:?}"), compare_at(&s, half, Tick::from_seconds_f64(0.2)), 0.0);
+    }
+}
diff --git a/crates/gpu/src/walk.rs b/crates/gpu/src/walk.rs
index b5bd166c..e2b2910f 100644
--- a/crates/gpu/src/walk.rs
+++ b/crates/gpu/src/walk.rs
@@ -214,6 +214,9 @@ fn draw_layer(e: &mut Enc, r: &Renderer, ctx: &EvalCtx, layer: &Layer, canvas: &
     if opacity <= 0.0 {
         return Some(());
     }
+    if let Some(done) = draw_precomp(e, r, ctx, layer, canvas, opacity) {
+        return done;
+    }
     let Some(st) = r.styled_layer(ctx, layer) else { return Some(()) };
     if st.plain {
         return composite_layer(e, r, ctx, layer, &st.body, canvas, opacity);
@@ -243,6 +246,50 @@ fn draw_layer(e: &mut Enc, r: &Renderer, ctx: &EvalCtx, layer: &Layer, canvas: &
     Some(())
 }
 
+/// A 2D precomp layer, its nested comp rendered resident on the GPU (`walk::render` one level
+/// down) instead of by the CPU compositor and uploaded every frame (`Renderer::layer_source`
+/// renders nested comps on the CPU: depth > 0). Then the layer's effects (resident), its
+/// placement, track matte / Preserve Transparency and blend, as for any layer. `None`: not this
+/// kind of layer, or the nested comp needs the CPU path (masks, layer styles, proxies,
+/// overrides, frame blending, nested motion-blur sampling; see `Renderer::precomp_source`);
+/// `Some(None)`: the GPU failed.
+fn draw_precomp(e: &mut Enc, r: &Renderer, ctx: &EvalCtx, layer: &Layer, canvas: &mut GpuImage, opacity: f32) -> Option<Option<()>> {
+    if layer.masks().is_some_and(|m| !m.children.is_empty()) || styles::active(ctx, layer) {
+        return None;
+    }
+    let (sub, item, lt, bs) = r.precomp_source(ctx, layer)?;
+    let Some(mut src) = render(e, &sub, item, lt) else { return Some(None) };
+    let pipe = r.pipe();
+    // `masked_source` quantises a non-solid source to the project's depth.
+    if let Some(l) = pipe.levels {
+        src = ops::quantize(e, &src, l);
+    }
+    let (mut img, offset, scale) = if layer.switches.effects && layer.effects().is_some_and(|f| !f.children.is_empty()) {
+        // Effects run in effect space (0.7.0): from the layer bounds' corner.
+        let o = ctx.effect_bounds(layer).1;
+        let mut fx = crate::effects::GpuFx::new(e, src, [o[0] * bs, o[1] * bs], bs, pipe.levels);
+        r.run_layer_effects_on(ctx, layer, &mut fx);
+        let Some((img, off, sc)) = fx.finish() else { return Some(None) };
+        (img, [off[0] - o[0] * sc, off[1] - o[1] * sc], sc)
+    } else {
+        (src, [0.0; 2], bs)
+    };
+    if img.width == 0 || img.height == 0 {
+        return Some(Some(()));
+    }
+    if let Some(c) = pipe.to_blend() {
+        img = ops::convert(e, &img, &c);
+    }
+    let shape = Buf { img: Image { width: img.width, height: img.height, data: Vec::new() }, offset, scale };
+    if r.track_matte(ctx, layer).is_some() || layer.preserve_transparency {
+        let Some(iso) = place_src(e, r, ctx, layer, &shape, img, &e.zeros(canvas.width, canvas.height), BlendMode::Normal, 1.0, None) else {
+            return Some(None);
+        };
+        return Some(composite_iso(e, r, ctx, layer, iso, canvas, opacity));
+    }
+    Some(place_src(e, r, ctx, layer, &shape, img, canvas, layer.blend_mode, opacity, pipe.levels).map(|c| *canvas = c))
+}
+
 /// Adjustment layer (`Renderer::draw_adjustment`): the effect stack runs on the comp below,
 /// resident on the GPU (non-GPU effects read back, run on the CPU and upload), and the result
 /// replaces the canvas inside the layer's footprint × opacity. `None` = draw it on the CPU.
@@ -342,6 +389,23 @@ fn place(
         return Some(target.clone());
     }
     let src = e.g.upload_buf(buf)?;
+    place_src(e, r, ctx, layer, buf, src, target, mode, opacity, levels)
+}
+
+/// [`place`] of a GPU image `src` shaped like `buf`.
+#[allow(clippy::too_many_arguments)]
+fn place_src(
+    e: &mut Enc,
+    r: &Renderer,
+    ctx: &EvalCtx,
+    layer: &Layer,
+    buf: &Buf,
+    src: GpuImage,
+    target: &GpuImage,
+    mode: BlendMode,
+    opacity: f32,
+    levels: Option<f32>,
+) -> Option<GpuImage> {
     let pl = r.placement(ctx, layer, buf);
     if let [m] = pl.matrices.as_slice() {
         return Some(ops::warp_q(e, target, &src, m, pl.sampling, mode, opacity, pl.seed, None, levels));
diff --git a/crates/render/src/lib.rs b/crates/render/src/lib.rs
index 79dcc21b..f4a5a98a 100644
--- a/crates/render/src/lib.rs
+++ b/crates/render/src/lib.rs
@@ -623,6 +623,30 @@ impl<'a> Renderer<'a> {
         }
     }
 
+    /// A precomp layer's nested comp for an accelerator to render resident (no CPU render and
+    /// upload of the nested frame): the renderer one level down, the comp, its time and the
+    /// buffer scale, exactly as [`Self::layer_source`]'s comp branch would render it. `None`
+    /// when that branch does more (composition proxy, Essential Properties overrides, frame
+    /// blending, recursion) or draws nothing (outside the nested comp's span): use the CPU path.
+    pub fn precomp_source(&self, ctx: &EvalCtx, layer: &Layer) -> Option<(Renderer<'a>, ItemId, Tick, f64)> {
+        let LayerSource::Comp { item } = layer.source else { return None };
+        if layer.switches.adjustment || self.project.comp_contains(item, ctx.comp_id) {
+            return None;
+        }
+        let nc = self.project.comp(item)?;
+        let lt = ctx.nested_time(layer);
+        if self.content_times(ctx, layer).is_some() {
+            return None;
+        }
+        if !nc.covers(lt) || self.proxy_for(item).is_some() || !essential_overrides(ctx, layer).is_empty() || frame_blend_mode(ctx, layer) != FrameBlend::Off {
+            return None;
+        }
+        let s = self.opts.scale;
+        let bs = if s < 1.0 && nc.preserve_resolution { 1.0 } else { s };
+        let base = self.nested_through(layer);
+        Some((Renderer { opts: RenderOpts { scale: bs, ..base.opts }, ..base }, item, lt, bs))
+    }
+
     /// The nested comp of a precomp layer whose transformations collapse into this comp: the
     /// Collapse Transformations switch is on and the layer has no masks, effects or layer
     /// styles (those force a flattened render of the precomp, as in After Effects).
@@ -1988,6 +2012,15 @@ impl<'a> Renderer<'a> {
         self.run_effect_stack(ctx, layer, adjustment, usize::MAX, None, [0.0; 2], target);
     }
 
+    /// [`Renderer::run_effects_on`] for a (non-adjustment) layer's own pixels: `target` holds
+    /// them in effect space (as [`Renderer::layer_input`] hands them out) and the result stays
+    /// there. Returns the effect-space origin in layer coordinates (rebase by its negation).
+    pub fn run_layer_effects_on(&self, ctx: &EvalCtx, layer: &Layer, target: &mut dyn FxTarget) -> [f64; 2] {
+        let origin = ctx.effect_bounds(layer).1;
+        self.run_effect_stack(ctx, layer, false, usize::MAX, None, origin, target);
+        origin
+    }
+
     /// An adjustment layer's footprint (its source with masks applied, layer space): where
     /// its effects show. `None` = the layer changes nothing.
     pub fn adjustment_footprint(&self, ctx: &EvalCtx, layer: &Layer) -> Option<Arc<Buf>> {