diff --git a/Cargo.lock b/Cargo.lock
index c228da3e01..d67969e7de 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -11805,6 +11805,7 @@ dependencies = [
  "parking_lot",
  "pathdiff",
  "petgraph 0.6.5",
+ "rayon",
  "reqwest 0.12.24",
  "rustls",
  "rustls-native-certs",
diff --git a/crates/pm/src/cmd/view.rs b/crates/pm/src/cmd/view.rs
index d8355e9922..d5632a69af 100644
--- a/crates/pm/src/cmd/view.rs
+++ b/crates/pm/src/cmd/view.rs
@@ -27,10 +27,9 @@ pub async fn view(package_spec: &str) -> Result<()> {
     tracing::debug!("Fetched package info: {full_manifest:?}");
 
     // Resolve version and get full VersionManifest (with all display fields)
-    let version_list: Vec<String> = full_manifest.versions.clone();
     let resolved_version = utoo_ruborist::resolver::version::resolve_target_version(
         &full_manifest.dist_tags,
-        &version_list,
+        &full_manifest.versions,
         version_spec,
     )
     .map_err(|e| {
diff --git a/crates/ruborist/Cargo.toml b/crates/ruborist/Cargo.toml
index ffdbcfae77..58f2b26372 100644
--- a/crates/ruborist/Cargo.toml
+++ b/crates/ruborist/Cargo.toml
@@ -54,7 +54,11 @@ reqwest = { version = "0.12", default-features = false, features = ["rustls-tls-
 
 # Native-only dependencies (not compiled for WASM)
 [target.'cfg(not(target_arch = "wasm32"))'.dependencies]
-libc = "0.2"
+libc  = "0.2"
+# Dedicated CPU thread pool for simd_json manifest parsing — keeps the
+# tokio runtime free of CPU-bound work so in-flight network IO is not
+# blocked by sibling parses. WASM falls back to inline parse.
+rayon = "1.10"
 
 # Browser handles TLS via the fetch API, so reqwest needs no rustls
 # feature on this target.
diff --git a/crates/ruborist/src/model/manifest.rs b/crates/ruborist/src/model/manifest.rs
index dea63dc7bc..c3a10fb53d 100644
--- a/crates/ruborist/src/model/manifest.rs
+++ b/crates/ruborist/src/model/manifest.rs
@@ -111,6 +111,33 @@ impl FullManifest {
     }
 }
 
+/// Re-parse the raw manifest bytes on rayon's CPU thread pool to extract
+/// a single version. Each resolved package triggers one full re-parse via
+/// `simd_json::to_borrowed_value`, which on hot paths (300+ resolves per
+/// install) accumulates into the dominant CPU bucket.
+///
+/// Returns `Arc<CoreVersionManifest>` so callers (e.g. UnifiedRegistry's
+/// version-manifest cache) can store and clone the result without
+/// deep-copying the underlying `HashMap`s. Wasm32 falls back to inline
+/// parse — no rayon, no thread pool.
+pub async fn extract_core_version_off_runtime(
+    full: std::sync::Arc<FullManifest>,
+    version: String,
+) -> Option<std::sync::Arc<CoreVersionManifest>> {
+    #[cfg(not(target_arch = "wasm32"))]
+    {
+        let (tx, rx) = tokio::sync::oneshot::channel();
+        rayon::spawn(move || {
+            let _ = tx.send(full.get_core_version(&version).map(std::sync::Arc::new));
+        });
+        rx.await.ok().flatten()
+    }
+    #[cfg(target_arch = "wasm32")]
+    {
+        full.get_core_version(&version).map(std::sync::Arc::new)
+    }
+}
+
 /// Deserialize a versions map by extracting only the keys, skipping all values.
 ///
 /// Uses `IgnoredAny` to skip over version manifest JSON objects without allocating,
diff --git a/crates/ruborist/src/resolver/preload.rs b/crates/ruborist/src/resolver/preload.rs
index 9fb5aff67b..b667d6e3d3 100644
--- a/crates/ruborist/src/resolver/preload.rs
+++ b/crates/ruborist/src/resolver/preload.rs
@@ -15,7 +15,7 @@ use crate::traits::progress::{BuildEvent, EventReceiver};
 use crate::traits::registry::RegistryClient;
 
 /// Default concurrency limit for manifest fetching
-pub const DEFAULT_CONCURRENCY: usize = 64;
+pub const DEFAULT_CONCURRENCY: usize = 256;
 
 /// A dependency spec: (name, version_spec)
 pub type Dep = (String, String);
diff --git a/crates/ruborist/src/resolver/registry.rs b/crates/ruborist/src/resolver/registry.rs
index 6edeb9069c..91e2e47310 100644
--- a/crates/ruborist/src/resolver/registry.rs
+++ b/crates/ruborist/src/resolver/registry.rs
@@ -137,14 +137,12 @@ pub fn resolve_from_manifest<E: std::error::Error + 'static>(
     manifest: &FullManifest,
     spec: &str,
 ) -> Result<ResolvedPackage, ResolveError<E>> {
-    let version_list: Vec<String> = manifest.versions.clone();
-
-    if version_list.is_empty() {
+    if manifest.versions.is_empty() {
         return Err(ResolveError::NoVersions(manifest.name.clone()));
     }
 
     // Resolve version using shared logic
-    let resolved_version = resolve_target_version(&manifest.dist_tags, &version_list, spec)
+    let resolved_version = resolve_target_version(&manifest.dist_tags, &manifest.versions, spec)
         .map_err(|e| ResolveError::Version(format!("{}@{}: {}", manifest.name, spec, e)))?;
 
     // Get manifest for resolved version (lazy: parse from Value on demand)
diff --git a/crates/ruborist/src/service/manifest.rs b/crates/ruborist/src/service/manifest.rs
index b9dbff7c8d..695cab58fd 100644
--- a/crates/ruborist/src/service/manifest.rs
+++ b/crates/ruborist/src/service/manifest.rs
@@ -13,6 +13,35 @@ use super::fetch::{
 use super::http::get_client;
 use crate::model::manifest::{CoreVersionManifest, FullManifest};
 
+/// Parse JSON bytes on rayon's CPU thread pool (native) or inline
+/// (wasm32). Keeps the tokio runtime free of `simd_json` CPU work so
+/// other in-flight manifest fetches can keep driving network IO while
+/// this one is parsing. Rayon's global pool work-steals across
+/// `num_cpus` threads, so concurrent manifest parses parallelise.
+async fn parse_json_off_runtime<T>(bytes: Vec<u8>) -> Result<T, anyhow::Error>
+where
+    T: serde::de::DeserializeOwned + Send + 'static,
+{
+    #[cfg(not(target_arch = "wasm32"))]
+    {
+        let (tx, rx) = tokio::sync::oneshot::channel();
+        rayon::spawn(move || {
+            let mut buf = bytes;
+            let result = simd_json::serde::from_slice::<T>(&mut buf)
+                .map_err(|e| anyhow!("JSON parse error: {e}"));
+            // Receiver dropped means the awaiting future was cancelled.
+            let _ = tx.send(result);
+        });
+        rx.await
+            .map_err(|e| anyhow!("rayon parse channel closed: {e}"))?
+    }
+    #[cfg(target_arch = "wasm32")]
+    {
+        let mut buf = bytes;
+        simd_json::serde::from_slice::<T>(&mut buf).map_err(|e| anyhow!("JSON parse error: {e}"))
+    }
+}
+
 /// Result of a full manifest fetch with ETag support.
 /// Transient return value, immediately destructured — Box not needed.
 #[allow(clippy::large_enum_variant)]
@@ -91,11 +120,13 @@ pub async fn fetch_full_manifest(opts: FetchManifestOptions<'_>) -> Result<Fetch
                         .await
                         .map_err(|e| FetchError::Permanent(anyhow!("Response read error: {e}")))?
                         .to_vec();
-                    // Save raw bytes before simd_json mutates the parse buffer.
-                    let mut parse_buf = raw_bytes.clone();
-                    let mut manifest: FullManifest =
-                        simd_json::serde::from_slice(&mut parse_buf)
-                            .map_err(|e| FetchError::Permanent(anyhow!("JSON parse error: {e}")))?;
+                    // simd_json mutates the parse buffer; clone so the raw
+                    // bytes survive for `manifest.raw`. Parse runs off-runtime
+                    // on rayon (native) so it cannot block sibling fetches.
+                    let parse_buf = raw_bytes.clone();
+                    let mut manifest: FullManifest = parse_json_off_runtime(parse_buf)
+                        .await
+                        .map_err(FetchError::Permanent)?;
                     manifest.raw = std::sync::Arc::from(raw_bytes);
 
                     Ok(FetchManifestResult::Ok(manifest, new_etag))
@@ -182,13 +213,14 @@ pub async fn fetch_version_manifest(
                     .map_err(classify_reqwest_error)?;
 
                 if response.status().is_success() {
-                    let mut bytes = response
+                    let bytes = response
                         .bytes()
                         .await
                         .map_err(|e| FetchError::Permanent(anyhow!("Response read error: {e}")))?
                         .to_vec();
-                    simd_json::serde::from_slice(&mut bytes)
-                        .map_err(|e| FetchError::Permanent(anyhow!("JSON parse error: {e}")))
+                    parse_json_off_runtime::<CoreVersionManifest>(bytes)
+                        .await
+                        .map_err(FetchError::Permanent)
                 } else {
                     Err(classify_status(response.status(), &url))
                 }
diff --git a/crates/ruborist/src/service/registry.rs b/crates/ruborist/src/service/registry.rs
index 0022a72e5e..7eed5ccaf0 100644
--- a/crates/ruborist/src/service/registry.rs
+++ b/crates/ruborist/src/service/registry.rs
@@ -244,11 +244,19 @@ impl UnifiedRegistry {
                 .await
                 .map_err(RegistryError)?
                 {
-                    manifest::FetchManifestResult::Ok(manifest, new_etag) => {
+                    manifest::FetchManifestResult::Ok(mut manifest, new_etag) => {
+                        // Move version_list / dist_tags out of `manifest`
+                        // into `VersionsInfo` instead of cloning. The cached
+                        // `Arc<FullManifest>` keeps `raw` + scalar metadata;
+                        // the canonical version_list / dist_tags now live in
+                        // the `versions_info` cache slot only. Readers that
+                        // need them go through `cache.get_versions(name)`.
+                        let version_list = std::mem::take(&mut manifest.versions);
+                        let dist_tags = std::mem::take(&mut manifest.dist_tags);
                         let versions_info = Arc::new(VersionsInfo {
                             versions: Versions {
-                                version_list: manifest.versions.clone(),
-                                dist_tags: manifest.dist_tags.clone(),
+                                version_list,
+                                dist_tags,
                             },
                             etag: new_etag,
                             last_updated: current_timestamp_secs(),
@@ -269,7 +277,7 @@ impl UnifiedRegistry {
                             self.cache.set_versions(name.to_string(), versions_info);
                         } else {
                             // Persistent store corrupted/missing, fetch fresh (without etag).
-                            let (manifest, new_etag) = manifest::fetch_full_manifest_fresh(
+                            let (mut manifest, new_etag) = manifest::fetch_full_manifest_fresh(
                                 &self.registry_url,
                                 name,
                                 manifest::MetadataFormat::Abbreviated,
@@ -277,10 +285,12 @@ impl UnifiedRegistry {
                             .await
                             .map_err(RegistryError)?;
 
+                            let version_list = std::mem::take(&mut manifest.versions);
+                            let dist_tags = std::mem::take(&mut manifest.dist_tags);
                             let versions_info = Arc::new(VersionsInfo {
                                 versions: Versions {
-                                    version_list: manifest.versions.clone(),
-                                    dist_tags: manifest.dist_tags.clone(),
+                                    version_list,
+                                    dist_tags,
                                 },
                                 etag: new_etag,
                                 last_updated: current_timestamp_secs(),
@@ -362,9 +372,8 @@ impl UnifiedRegistry {
                         // version from the full manifest. `resolve_full_manifest`
                         // is itself inflight-gated, so concurrent specs for the
                         // same name share one full-manifest fetch.
-                        let (resolved_version, manifest) =
+                        let (resolved_version, arc) =
                             self.resolve_via_full_manifest(name, spec).await?;
-                        let arc = Arc::new(manifest);
                         self.cache.set_version_manifest(
                             name.to_string(),
                             spec.to_string(),
@@ -426,16 +435,39 @@ impl UnifiedRegistry {
         &self,
         name: &str,
         spec: &str,
-    ) -> Result<(String, CoreVersionManifest), RegistryError> {
+    ) -> Result<(String, Arc<CoreVersionManifest>), RegistryError> {
         match self.resolve_full_manifest(name).await? {
             FullManifestResult::Full(full) => {
-                if full.versions.is_empty() {
+                // Canonical `version_list` / `dist_tags` live in the
+                // `versions_info` cache slot; the parallel slot is filled by
+                // the same code path that filled `full_manifests`. We don't
+                // duplicate them on the cached `Arc<FullManifest>`.
+                let versions_info = self.cache.get_versions(name).ok_or_else(|| {
+                    RegistryError(anyhow!("Versions cache not found for {}", name))
+                })?;
+                if versions_info.versions.version_list.is_empty() {
                     return Err(RegistryError(anyhow!("No versions available for {}", name)));
                 }
-                let resolved_version =
-                    resolve_target_version(&full.dist_tags, &full.versions, spec)
-                        .map_err(|e| RegistryError(anyhow!("{}@{}: {}", name, spec, e)))?;
-                let core = full.get_core_version(&resolved_version).ok_or_else(|| {
+                let resolved_version = resolve_target_version(
+                    &versions_info.versions.dist_tags,
+                    &versions_info.versions.version_list,
+                    spec,
+                )
+                .map_err(|e| RegistryError(anyhow!("{}@{}: {}", name, spec, e)))?;
+                // Short-circuit: a sibling spec may have already resolved to
+                // this same version and warmed the cache. Skip the rayon
+                // reparse (the dominant cost on the resolve hot path) and
+                // share the existing `Arc<CoreVersionManifest>` instead of
+                // deep-cloning its HashMaps.
+                if let Some(cached) = self.cache.get_version_manifest(name, &resolved_version) {
+                    return Ok((resolved_version, cached));
+                }
+                let core = crate::model::manifest::extract_core_version_off_runtime(
+                    Arc::clone(&full),
+                    resolved_version.clone(),
+                )
+                .await
+                .ok_or_else(|| {
                     RegistryError(anyhow!(
                         "Version {} not found in manifest for {}",
                         resolved_version,
@@ -469,7 +501,7 @@ impl UnifiedRegistry {
                     })
                     .await
                     .map_err(RegistryError)?;
-                Ok((resolved_version, manifest))
+                Ok((resolved_version, Arc::new(manifest)))
             }
         }
     }
diff --git a/crates/ruborist/src/traits/registry.rs b/crates/ruborist/src/traits/registry.rs
index df8adac00f..c6ad7d532a 100644
--- a/crates/ruborist/src/traits/registry.rs
+++ b/crates/ruborist/src/traits/registry.rs
@@ -157,11 +157,11 @@ pub trait RegistryClient {
     ) -> impl Future<Output = Result<Arc<CoreVersionManifest>, Self::Error>> {
         async move {
             let manifest = self.fetch_full_manifest(name).await?;
-            let version_list: Vec<String> = manifest.versions.clone();
 
             // Resolve version using shared logic
-            let resolved_version = resolve_target_version(&manifest.dist_tags, &version_list, spec)
-                .map_err(|e| RegistryError(anyhow::anyhow!("{}@{}: {}", name, spec, e)))?;
+            let resolved_version =
+                resolve_target_version(&manifest.dist_tags, &manifest.versions, spec)
+                    .map_err(|e| RegistryError(anyhow::anyhow!("{}@{}: {}", name, spec, e)))?;
 
             manifest
                 .get_core_version(&resolved_version)
@@ -227,9 +227,8 @@ pub trait RegistryClient {
                     fetch_spec
                 );
                 let full_manifest = self.fetch_full_manifest(&fetch_name).await?;
-                let version_list: Vec<String> = full_manifest.versions.clone();
 
-                if version_list.is_empty() {
+                if full_manifest.versions.is_empty() {
                     return Err(RegistryError(anyhow::anyhow!(
                         "No versions available for {}",
                         fetch_name
@@ -237,9 +236,12 @@ pub trait RegistryClient {
                     .into());
                 }
 
-                let resolved_version =
-                    resolve_target_version(&full_manifest.dist_tags, &version_list, &fetch_spec)
-                        .map_err(|e| RegistryError(anyhow::anyhow!("{}@{}: {}", name, spec, e)))?;
+                let resolved_version = resolve_target_version(
+                    &full_manifest.dist_tags,
+                    &full_manifest.versions,
+                    &fetch_spec,
+                )
+                .map_err(|e| RegistryError(anyhow::anyhow!("{}@{}: {}", name, spec, e)))?;
 
                 let version_manifest = full_manifest
                     .get_core_version(&resolved_version)