diff --git a/src/scene/pipeline/gpu_budget.rs b/src/scene/pipeline/gpu_budget.rs
index 5338a2310..052f1fdb9 100644
--- a/src/scene/pipeline/gpu_budget.rs
+++ b/src/scene/pipeline/gpu_budget.rs
@@ -8,19 +8,50 @@ fn device_ceiling(device: &wgpu::Device) -> usize {
     (usize::try_from(device.limits().max_buffer_size).unwrap_or(usize::MAX) / 10) * 9
 }
 
-/// Optional per-buffer cap in MiB, useful for testing smaller chunks.
-fn cap_bytes() -> usize {
-    static CAP: std::sync::OnceLock<usize> = std::sync::OnceLock::new();
+/// The wire arena keeps one persistent instance buffer for the whole resident
+/// set and patches it in place. Capping that at the per-chunk budget pushes any
+/// drawing past ~524 k instances onto the batched fallback, which re-uploads
+/// everything on every edit — 200 ms a click on a drawing with 821 k. A single
+/// long-lived buffer can afford more than a transient chunk, and 128 MiB is
+/// still four times smaller than the 505 MiB allocation that crashed a 2 GB
+/// card in the first place.
+const ARENA_CAP_BYTES: usize = 128 * 1024 * 1024;
+
+/// `OCS_GPU_CHUNK_MIB`, when set. Overrides both caps so a test can force
+/// small buffers.
+fn env_cap_bytes() -> Option<usize> {
+    static CAP: std::sync::OnceLock<Option<usize>> = std::sync::OnceLock::new();
     *CAP.get_or_init(|| {
         std::env::var("OCS_GPU_CHUNK_MIB")
             .ok()
             .and_then(|value| value.trim().parse::<usize>().ok())
             .filter(|mib| *mib > 0)
             .and_then(|mib| mib.checked_mul(1024 * 1024))
-            .unwrap_or(HARD_CAP_BYTES)
     })
 }
 
+/// Optional per-buffer cap in MiB, useful for testing smaller chunks.
+fn cap_bytes() -> usize {
+    env_cap_bytes().unwrap_or(HARD_CAP_BYTES)
+}
+
+/// Largest byte size the wire arena's persistent buffers may take.
+pub fn arena_budget(device: &wgpu::Device) -> usize {
+    device_ceiling(device).min(env_cap_bytes().unwrap_or(ARENA_CAP_BYTES))
+}
+
+/// How many `T` fit in one arena buffer. Never returns 0.
+pub fn max_arena_elements<T>(device: &wgpu::Device) -> usize {
+    (arena_budget(device) / std::mem::size_of::<T>().max(1)).max(1)
+}
+
+/// Arena storage buffers must also fit in one binding.
+pub fn max_arena_storage_elements<T>(device: &wgpu::Device) -> usize {
+    (arena_budget(device).min(device.limits().max_storage_buffer_binding_size as usize)
+        / std::mem::size_of::<T>().max(1))
+    .max(1)
+}
+
 /// Largest byte size a single buffer built by this renderer may take.
 pub fn buffer_budget(device: &wgpu::Device) -> usize {
     device_ceiling(device).min(cap_bytes())
diff --git a/src/scene/pipeline/wire_arena.rs b/src/scene/pipeline/wire_arena.rs
index cf9707c58..9b10f76f7 100644
--- a/src/scene/pipeline/wire_arena.rs
+++ b/src/scene/pipeline/wire_arena.rs
@@ -313,8 +313,10 @@ impl WireArena {
         const_bgl: &wgpu::BindGroupLayout,
         mesh_edge: bool,
     ) -> Option<Self> {
-        let instance_limit = super::gpu_budget::max_elements::<WireInstance>(device) as u64;
-        let constant_limit = super::gpu_budget::max_storage_elements::<WireConst>(device) as u64;
+        let instance_limit =
+            super::gpu_budget::max_arena_elements::<WireInstance>(device) as u64;
+        let constant_limit =
+            super::gpu_budget::max_arena_storage_elements::<WireConst>(device) as u64;
         let ranges = handle_ranges(wires)?;
         let perf = crate::perf::enabled();
         let total_started = iced::time::Instant::now();
@@ -971,7 +973,8 @@ impl PackedWireArena {
         depth_map: &FxHashMap<u64, [f32; 2]>,
         mesh_edge: bool,
     ) -> Option<Self> {
-        let packed_limit = super::gpu_budget::max_elements::<PackedWireInstance>(device) as u64;
+        let packed_limit =
+            super::gpu_budget::max_arena_elements::<PackedWireInstance>(device) as u64;
         let ranges = handle_ranges(wires)?;
         let max_instances: usize = wires
             .iter()