diff --git a/Cargo.lock b/Cargo.lock
index 51c1c58..15ac94f 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -93,9 +93,9 @@ checksum = "252afb9ae5eaa683babdc6a068b3f5726eb19e05070c731f9b2a23a7c3e8ed34"
 
 [[package]]
 name = "fearless_simd"
-version = "0.7.0"
+version = "1.0.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "f4beca3cb2444e3304ac30843cc091f44ed58932353cd492ce740067bfce6b12"
+checksum = "f3772b63c40606beea8fe1f7b06a60de27ceb9bfc2d9dad3427368ca41dc7e62"
 
 [[package]]
 name = "image"
diff --git a/Cargo.toml b/Cargo.toml
index a40c2f9..98fbd06 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -25,7 +25,7 @@ categories = ["multimedia::images", "compression"]
 [workspace.dependencies]
 j2k-core = "=0.10.0"
 j2k-metal-support = "=0.10.0"
-fearless_simd = "=0.7.0"
+fearless_simd = "=1.0.0"
 cudarc = { version = "=0.19.9", default-features = false, features = [
     "std",
     "driver",
diff --git a/THIRD_PARTY_NOTICES.md b/THIRD_PARTY_NOTICES.md
index 1919d08..ecdb1e4 100644
--- a/THIRD_PARTY_NOTICES.md
+++ b/THIRD_PARTY_NOTICES.md
@@ -6,7 +6,7 @@ transcribed from ITU-T T.832. No T.835/JXRLib source code is included.
 JPEG XR tables added from the ITU-T T.835 / Microsoft JPEG XR reference source
 must retain the applicable BSD-3-Clause copyright and disclaimer here.
 
-`fearless_simd` 0.7.0 is used through its safe capability-token API and is
+`fearless_simd` 1.0.0 is used through its safe capability-token API and is
 available under MIT or Apache-2.0 licensing.
 
 `cudarc` 0.19.9 provides dynamically loaded CUDA Driver API and NVRTC bindings
diff --git a/crates/jxr-core/tests/contracts.rs b/crates/jxr-core/tests/contracts.rs
index c4ceff3..4c26e05 100644
--- a/crates/jxr-core/tests/contracts.rs
+++ b/crates/jxr-core/tests/contracts.rs
@@ -115,8 +115,7 @@ fn surface_layout_rejects_overlapping_planar_destinations() {
 }
 
 #[test]
-fn core_uses_shared_backend_and_rect_contracts() {
-    assert_eq!(BackendKind::Cpu, BackendKind::Cpu);
+fn shared_rect_accepts_contained_region() {
     assert!(
         Rect {
             x: 1,
diff --git a/crates/jxr-native/src/output_format/simd_pack.rs b/crates/jxr-native/src/output_format/simd_pack.rs
index e384461..591ab77 100644
--- a/crates/jxr-native/src/output_format/simd_pack.rs
+++ b/crates/jxr-native/src/output_format/simd_pack.rs
@@ -1,6 +1,6 @@
 //! Capability-token dispatch for common unsigned planar packing.
 
-use fearless_simd::{Level, Simd};
+use fearless_simd::{Bytes, Level, Simd, SimdBase, SimdNarrow};
 
 use super::OutputFormatError;
 
@@ -90,28 +90,94 @@ fn pack_accelerated(
 ) -> bool {
     #[cfg(any(target_arch = "x86", target_arch = "x86_64"))]
     if let Some(avx2) = level.as_avx2() {
-        pack_vectorized(avx2, input, stride, start, dimensions, scaled, output);
-        return true;
+        return pack_vectorized(avx2, input, stride, start, dimensions, scaled, output);
     }
     #[cfg(target_arch = "aarch64")]
     if let Some(neon) = level.as_neon() {
-        pack_vectorized(neon, input, stride, start, dimensions, scaled, output);
-        return true;
+        return pack_vectorized(neon, input, stride, start, dimensions, scaled, output);
     }
     false
 }
 
 #[inline]
 fn pack_vectorized<S: Simd>(
-    _simd: S,
+    simd: S,
     input: &[i32],
     stride: usize,
     start: [usize; 2],
     dimensions: [usize; 2],
     scaled: bool,
     output: &mut [u8],
-) {
-    pack_rows(input, stride, start, dimensions, scaled, output);
+) -> bool {
+    let lanes = S::i32s::LEN;
+    let packed_lanes = S::u8s::LEN;
+    let [width, height] = dimensions;
+    if width < packed_lanes {
+        return false;
+    }
+
+    simd.vectorize(|| {
+        let bias = if scaled { 1_024 } else { 128 };
+        let rounding = if scaled { 3 } else { 0 };
+        let addition = bias + rounding;
+        let shift = if scaled { 3 } else { 0 };
+        let zero = S::i32s::splat(simd, 0);
+        let max = S::i32s::splat(simd, 255);
+        let vector_width = width / packed_lanes * packed_lanes;
+        for y in 0..height {
+            let source_start = (start[1] + y) * stride + start[0];
+            let source = &input[source_start..source_start + width];
+            let destination = &mut output[y * width..(y + 1) * width];
+            for (source, destination) in source[..vector_width]
+                .chunks_exact(packed_lanes)
+                .zip(destination[..vector_width].chunks_exact_mut(packed_lanes))
+            {
+                let first = pack_lanes(simd, &source[..lanes], addition, shift, zero, max);
+                let second =
+                    pack_lanes(simd, &source[lanes..2 * lanes], addition, shift, zero, max);
+                let third = pack_lanes(
+                    simd,
+                    &source[2 * lanes..3 * lanes],
+                    addition,
+                    shift,
+                    zero,
+                    max,
+                );
+                let fourth = pack_lanes(simd, &source[3 * lanes..], addition, shift, zero, max);
+                first
+                    .saturating_narrow(second)
+                    .saturating_narrow(third.saturating_narrow(fourth))
+                    .store_slice(destination);
+            }
+            for (destination, &sample) in destination[vector_width..]
+                .iter_mut()
+                .zip(&source[vector_width..])
+            {
+                *destination = u8::try_from(((sample + bias + rounding) >> shift).clamp(0, 255))
+                    .expect("sample is clipped to u8");
+            }
+        }
+    });
+    true
+}
+
+#[expect(
+    clippy::inline_always,
+    reason = "SIMD helper must inline into the target-feature vectorize context"
+)]
+#[inline(always)]
+fn pack_lanes<S: Simd>(
+    simd: S,
+    source: &[i32],
+    addition: i32,
+    shift: u32,
+    zero: S::i32s,
+    max: S::i32s,
+) -> S::u32s {
+    ((S::i32s::from_slice(simd, source) + addition) >> shift)
+        .max(zero)
+        .min(max)
+        .bitcast()
 }
 
 #[inline]
@@ -183,4 +249,44 @@ mod tests {
             assert_eq!(output, expected);
         }
     }
+
+    #[test]
+    fn packing_matches_scalar_at_row_tails_and_clamp_boundaries() {
+        let width = 37;
+        let height = 3;
+        let stride = 41;
+        let input: Vec<i32> = (0..stride * (height + 1))
+            .map(|index| match index % 5 {
+                0 => -2_000,
+                1 => -128,
+                2 => 0,
+                3 => 1_024,
+                _ => i32::MAX - 1_027,
+            })
+            .collect();
+        for scaled in [false, true] {
+            let mut output = Vec::new();
+            append_u8(
+                Level::new(),
+                &input,
+                stride,
+                [2, 1],
+                [width, height],
+                scaled,
+                &mut output,
+            )
+            .unwrap();
+            let bias = if scaled { 1_024 } else { 128 };
+            let rounding = if scaled { 3 } else { 0 };
+            let shift = if scaled { 3 } else { 0 };
+            let expected: Vec<_> = (1..=height)
+                .flat_map(|y| &input[y * stride + 2..y * stride + 2 + width])
+                .map(|&sample| {
+                    u8::try_from(((sample + bias + rounding) >> shift).clamp(0, 255))
+                        .expect("sample is clipped to u8")
+                })
+                .collect();
+            assert_eq!(output, expected);
+        }
+    }
 }
diff --git a/crates/jxr-native/src/reconstruct/simd_dequant.rs b/crates/jxr-native/src/reconstruct/simd_dequant.rs
index 0335e0c..dfc995d 100644
--- a/crates/jxr-native/src/reconstruct/simd_dequant.rs
+++ b/crates/jxr-native/src/reconstruct/simd_dequant.rs
@@ -1,6 +1,6 @@
 //! Checked capability-token SIMD for contiguous coefficient scaling.
 
-use fearless_simd::Simd;
+use fearless_simd::{Simd, SimdBase};
 use jxr_math::quantization::Quantizer;
 
 use crate::CpuCapabilities;
@@ -49,8 +49,24 @@ pub(super) fn scale_coefficients(
 }
 
 #[inline]
-fn scale_vectorized<S: Simd>(_simd: S, input: &[i32], output: &mut [i32], step: u32) {
-    scale_validated(input, output, step);
+fn scale_vectorized<S: Simd>(simd: S, input: &[i32], output: &mut [i32], step: u32) {
+    let multiplier = i32::from_ne_bytes(step.to_ne_bytes());
+    simd.vectorize(|| {
+        let lanes = S::i32s::LEN;
+        let vector_multiplier = S::i32s::splat(simd, multiplier);
+        let mut input_chunks = input.chunks_exact(lanes);
+        let mut output_chunks = output.chunks_exact_mut(lanes);
+        for (source, destination) in input_chunks.by_ref().zip(output_chunks.by_ref()) {
+            (S::i32s::from_slice(simd, source) * vector_multiplier).store_slice(destination);
+        }
+        for (&source, destination) in input_chunks
+            .remainder()
+            .iter()
+            .zip(output_chunks.into_remainder())
+        {
+            *destination = source.wrapping_mul(multiplier);
+        }
+    });
 }
 
 #[inline]
@@ -99,4 +115,17 @@ mod tests {
             .is_err()
         );
     }
+
+    #[test]
+    fn coefficient_scaling_preserves_negative_values_and_tail() {
+        let input: Vec<_> = (-34..35).collect();
+        let quantizer = Quantizer::new(113).unwrap();
+        let mut output = vec![0; input.len()];
+        scale_coefficients(CpuCapabilities::detect(), quantizer, &input, &mut output).unwrap();
+        let expected: Vec<_> = input
+            .iter()
+            .map(|&value| quantizer.dequantize(value).unwrap())
+            .collect();
+        assert_eq!(output, expected);
+    }
 }
diff --git a/crates/jxr/fuzz/Cargo.lock b/crates/jxr/fuzz/Cargo.lock
index 9be014c..faf8f55 100644
--- a/crates/jxr/fuzz/Cargo.lock
+++ b/crates/jxr/fuzz/Cargo.lock
@@ -68,9 +68,9 @@ checksum = "252afb9ae5eaa683babdc6a068b3f5726eb19e05070c731f9b2a23a7c3e8ed34"
 
 [[package]]
 name = "fearless_simd"
-version = "0.7.0"
+version = "1.0.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "f4beca3cb2444e3304ac30843cc091f44ed58932353cd492ce740067bfce6b12"
+checksum = "f3772b63c40606beea8fe1f7b06a60de27ceb9bfc2d9dad3427368ca41dc7e62"
 
 [[package]]
 name = "find-msvc-tools"