diff --git a/nodedb-client/Cargo.toml b/nodedb-client/Cargo.toml
index e036aca22..2d729f2cc 100644
--- a/nodedb-client/Cargo.toml
+++ b/nodedb-client/Cargo.toml
@@ -35,5 +35,15 @@ zerompk = { workspace = true, optional = true }
 tokio-rustls = { workspace = true, optional = true }
 rustls-pemfile = { workspace = true, optional = true }
 
-[dev-dependencies]
+# The optional `tokio` above is the crate's own dependency and stays as it is;
+# these are the dev-dependencies. Native needs nothing new, but the workspace
+# entry cannot be used in both: workspace features are additive, so
+# `{ workspace = true }` always carries the workspace's `features = ["full"]`,
+# and tokio refuses to build on wasm with anything beyond
+# `sync,macros,io-util,rt,time`. The wasm entry therefore names the version and
+# the features directly, which is what keeps the test targets buildable on both.
+[target.'cfg(not(target_arch = "wasm32"))'.dev-dependencies]
 tokio = { workspace = true, features = ["rt", "macros"] }
+
+[target.'cfg(target_arch = "wasm32")'.dev-dependencies]
+tokio = { version = "1", default-features = false, features = ["rt", "macros", "sync", "time"] }
diff --git a/nodedb-crdt/Cargo.toml b/nodedb-crdt/Cargo.toml
index e5e100bf7..dbd53f948 100644
--- a/nodedb-crdt/Cargo.toml
+++ b/nodedb-crdt/Cargo.toml
@@ -27,5 +27,12 @@ subtle = { workspace = true }
 getrandom = { workspace = true }
 
 [dev-dependencies]
-tokio = { workspace = true }
 serde_json = { workspace = true }
+
+# Native-only dev-dependencies. `tokio = { workspace = true }` inherits
+# `features = ["full"]`, and tokio refuses fs/io-std/net/process/
+# rt-multi-thread/signal on wasm; Cargo unifies dev-dependency features across
+# the whole `cargo test` invocation, so it breaks every wasm test target in the
+# build. No test or bench in this crate calls tokio.
+[target.'cfg(not(target_arch = "wasm32"))'.dev-dependencies]
+tokio = { workspace = true }
diff --git a/nodedb-mem/Cargo.toml b/nodedb-mem/Cargo.toml
index 4ba61e85b..0f0830f1e 100644
--- a/nodedb-mem/Cargo.toml
+++ b/nodedb-mem/Cargo.toml
@@ -23,7 +23,17 @@ tikv-jemalloc-ctl = { workspace = true }
 libc = { workspace = true }
 
 [dev-dependencies]
-tokio = { workspace = true }
-fluxbench = { workspace = true }
 tracing-subscriber = { workspace = true }
 tempfile = { workspace = true }
+
+# Native-only dev-dependencies. `tokio = { workspace = true }` inherits
+# `features = ["full"]`, `fluxbench` declares its own normal
+# `tokio = { features = ["full"] }`, and tokio refuses
+# fs/io-std/net/process/rt-multi-thread/signal on wasm; Cargo unifies
+# dev-dependency features across the whole `cargo test` invocation, so either
+# entry breaks every wasm test target in the build. Neither is reachable from a
+# wasm test here: this crate has no tokio call sites, no benches and no tokio
+# test attribute.
+[target.'cfg(not(target_arch = "wasm32"))'.dev-dependencies]
+tokio = { workspace = true }
+fluxbench = { workspace = true }
diff --git a/nodedb-mem/src/budget.rs b/nodedb-mem/src/budget.rs
index 8624a145e..9b34e485d 100644
--- a/nodedb-mem/src/budget.rs
+++ b/nodedb-mem/src/budget.rs
@@ -320,6 +320,9 @@ mod tests {
         assert_eq!(budget.allocated(), 0);
     }
 
+    // Drives the reserve path from real threads; `wasm32-wasip1` has none.
+
+    #[cfg(not(target_arch = "wasm32"))]
     #[test]
     fn concurrent_reserves() {
         use std::sync::Arc;
diff --git a/nodedb-mem/src/governor/reserve.rs b/nodedb-mem/src/governor/reserve.rs
index 1b3cd5dfb..a2566111c 100644
--- a/nodedb-mem/src/governor/reserve.rs
+++ b/nodedb-mem/src/governor/reserve.rs
@@ -167,11 +167,7 @@ impl MemoryGovernor {
 
 #[cfg(test)]
 mod tests {
-    use std::sync::Arc;
     use std::sync::atomic::Ordering;
-    use std::thread;
-
-    use nodedb_types::{DatabaseId, TenantId};
 
     use super::*;
     use crate::engine_limits::EngineLimits;
@@ -345,8 +341,16 @@ mod tests {
 
     // ── Concurrent reserves ───────────────────────────────────────────────────
 
+    // Drives the reserve path from real threads; `wasm32-wasip1` has none.
+
+    #[cfg(not(target_arch = "wasm32"))]
     #[test]
     fn concurrent_reserves_never_exceed_cap() {
+        use std::sync::Arc;
+        use std::thread;
+
+        use nodedb_types::{DatabaseId, TenantId};
+
         let limits = EngineLimits::zeroed().with(EngineId::Vector, 10_000);
         let gov = Arc::new(
             MemoryGovernor::new(GovernorConfig {