diff --git a/backend/windmill-worker/nsjail/download.py.config.proto b/backend/windmill-worker/nsjail/download.py.config.proto
index 18957bb4a5..a68d96eb92 100644
--- a/backend/windmill-worker/nsjail/download.py.config.proto
+++ b/backend/windmill-worker/nsjail/download.py.config.proto
@@ -30,7 +30,8 @@ clone_newnet: false
 clone_newuser: {CLONE_NEWUSER}
 
 skip_setsid: true
-keep_caps: true
+# No capability needed: writes go to the rw-mounted dirs as the jail's own uid, like the run.* profiles.
+keep_caps: false
 keep_env: true
 mount_proc: true
 
diff --git a/backend/windmill-worker/nsjail/download.ruby.config.proto b/backend/windmill-worker/nsjail/download.ruby.config.proto
index 31eefae766..3a3a6f3b74 100644
--- a/backend/windmill-worker/nsjail/download.ruby.config.proto
+++ b/backend/windmill-worker/nsjail/download.ruby.config.proto
@@ -23,7 +23,8 @@ clone_newnet: false
 clone_newuser: {CLONE_NEWUSER}
 
 skip_setsid: true
-keep_caps: true
+# No capability needed: writes go to the rw-mounted dirs as the jail's own uid, like the run.* profiles.
+keep_caps: false
 keep_env: true
 mount_proc: true
 
diff --git a/backend/windmill-worker/nsjail/download_deps.py.sh b/backend/windmill-worker/nsjail/download_deps.py.sh
index 6b4cd8cfd8..8f0ebd1cd0 100755
--- a/backend/windmill-worker/nsjail/download_deps.py.sh
+++ b/backend/windmill-worker/nsjail/download_deps.py.sh
@@ -20,20 +20,22 @@ then
       echo "\$TRUSTED_HOST is set to $TRUSTED_HOST"
 fi
 
-CMD="/usr/local/bin/uv pip install
-\"$REQ\"
---target \"$TARGET\"
---no-cache
---no-config
---no-color
---no-deps
---link-mode=copy
-$PY_PATH
-$INDEX_URL_ARG $EXTRA_INDEX_URL_ARG $TRUSTED_HOST_ARG
---system
---reinstall
---compile-bytecode
-"
+# Build the argv directly so each value reaches uv as a single argument, quoting
+# intact (e.g. PEP 508 markers). The unquoted expansions are worker configuration
+# and split into separate arguments on purpose.
+set -- /usr/local/bin/uv pip install \
+    "$REQ" \
+    --target "$TARGET" \
+    --no-cache \
+    --no-config \
+    --no-color \
+    --no-deps \
+    --link-mode=copy \
+    $PY_PATH \
+    $INDEX_URL_ARG $EXTRA_INDEX_URL_ARG $TRUSTED_HOST_ARG \
+    --system \
+    --reinstall \
+    --compile-bytecode
 
-echo $CMD
-eval $CMD
+echo "$@"
+exec "$@"
diff --git a/backend/windmill-worker/nsjail/install.r.config.proto b/backend/windmill-worker/nsjail/install.r.config.proto
index dff9acde15..e844b2e720 100644
--- a/backend/windmill-worker/nsjail/install.r.config.proto
+++ b/backend/windmill-worker/nsjail/install.r.config.proto
@@ -16,7 +16,8 @@ clone_newnet: false
 clone_newuser: {CLONE_NEWUSER}
 
 skip_setsid: true
-keep_caps: true
+# No capability needed: writes go to the rw-mounted dirs as the jail's own uid, like the run.* profiles.
+keep_caps: false
 keep_env: true
 mount_proc: true
 
diff --git a/backend/windmill-worker/nsjail/lock.py.config.proto b/backend/windmill-worker/nsjail/lock.py.config.proto
index 14119c4089..60c5573f40 100644
--- a/backend/windmill-worker/nsjail/lock.py.config.proto
+++ b/backend/windmill-worker/nsjail/lock.py.config.proto
@@ -23,7 +23,8 @@ clone_newnet: false
 clone_newuser: {CLONE_NEWUSER}
 
 skip_setsid: true
-keep_caps: true
+# No capability needed: writes go to the rw-mounted dirs as the jail's own uid, like the run.* profiles.
+keep_caps: false
 keep_env: true
 mount_proc: true
 
diff --git a/backend/windmill-worker/nsjail/lock.ruby.config.proto b/backend/windmill-worker/nsjail/lock.ruby.config.proto
index 6f82f3b748..bcca74e77e 100644
--- a/backend/windmill-worker/nsjail/lock.ruby.config.proto
+++ b/backend/windmill-worker/nsjail/lock.ruby.config.proto
@@ -19,7 +19,8 @@ clone_newnet: false
 clone_newuser: {CLONE_NEWUSER}
 
 skip_setsid: true
-keep_caps: true
+# No capability needed: writes go to the rw-mounted dirs as the jail's own uid, like the run.* profiles.
+keep_caps: false
 keep_env: true
 mount_proc: true
 
diff --git a/backend/windmill-worker/src/nsjail_compat.rs b/backend/windmill-worker/src/nsjail_compat.rs
index 3069dcee52..e3b1f7656f 100644
--- a/backend/windmill-worker/src/nsjail_compat.rs
+++ b/backend/windmill-worker/src/nsjail_compat.rs
@@ -46,4 +46,90 @@ mod tests {
         assert_eq!(twice.matches("gvisor_compat").count(), 1);
         assert!(twice.ends_with("\nclone_newcgroup: false\ngvisor_compat: true\n"));
     }
+
+    /// Every nsjail profile drops its capabilities.
+    #[test]
+    fn every_nsjail_config_drops_capabilities() {
+        let dir = concat!(env!("CARGO_MANIFEST_DIR"), "/nsjail");
+        let mut checked = 0;
+        for entry in std::fs::read_dir(dir).expect("nsjail config dir") {
+            let path = entry.expect("dir entry").path();
+            if path.extension().and_then(|e| e.to_str()) != Some("proto") {
+                continue;
+            }
+            let content = std::fs::read_to_string(&path).expect("read config");
+            let settings = content
+                .lines()
+                .map(str::trim)
+                .filter(|l| l.starts_with("keep_caps"))
+                .collect::<Vec<_>>();
+            assert_eq!(
+                settings,
+                vec!["keep_caps: false"],
+                "{} must set keep_caps: false exactly once",
+                path.display()
+            );
+            checked += 1;
+        }
+        assert!(
+            checked >= 20,
+            "only {checked} nsjail configs found in {dir}, expected all of them"
+        );
+    }
+
+    /// `REQ` and `TARGET` reach uv as single, unaltered argv words.
+    #[cfg(unix)]
+    #[test]
+    fn download_deps_passes_the_requirement_as_a_literal_argv_word() {
+        use std::os::unix::fs::PermissionsExt;
+
+        let dir = std::env::temp_dir().join(format!("wm_download_deps_{}", std::process::id()));
+        let _ = std::fs::remove_dir_all(&dir);
+        std::fs::create_dir_all(&dir).expect("scratch dir");
+
+        // Stand-in for uv that prints each argument it receives on its own line.
+        let uv = dir.join("uv_argv_dump");
+        std::fs::write(
+            &uv,
+            "#!/bin/sh\nfor a in \"$@\"; do printf '<%s>\\n' \"$a\"; done\n",
+        )
+        .expect("write stub");
+        std::fs::set_permissions(&uv, std::fs::Permissions::from_mode(0o755)).expect("chmod stub");
+
+        let script = dir.join("download_deps.sh");
+        std::fs::write(
+            &script,
+            include_str!("../nsjail/download_deps.py.sh")
+                .replace("/usr/local/bin/uv", uv.to_str().unwrap()),
+        )
+        .expect("write script");
+
+        let marker = dir.join("marker");
+        let req = format!("x==$(touch {})", marker.display());
+        let target = dir.join("target dir with spaces");
+        let out = std::process::Command::new("/bin/sh")
+            .arg(&script)
+            .env_clear()
+            .env("PATH", "/usr/bin:/bin")
+            .env("REQ", &req)
+            .env("TARGET", &target)
+            .output()
+            .expect("run download_deps.sh");
+        let stdout = String::from_utf8_lossy(&out.stdout).into_owned();
+
+        assert!(
+            !marker.exists(),
+            "REQ was not passed through verbatim; stdout was:\n{stdout}"
+        );
+        assert!(
+            stdout.contains(&format!("<{req}>\n")),
+            "the requirement must be one literal argv word; stdout was:\n{stdout}"
+        );
+        assert!(
+            stdout.contains(&format!("<--target>\n<{}>\n", target.display())),
+            "--target must be followed by the target dir as one argv word; stdout was:\n{stdout}"
+        );
+
+        std::fs::remove_dir_all(&dir).expect("cleanup scratch dir");
+    }
 }