diff --git a/src/resolver/package_json.rs b/src/resolver/package_json.rs
index 1aa43e1a9881..86d9827ef30c 100644
--- a/src/resolver/package_json.rs
+++ b/src/resolver/package_json.rs
@@ -227,8 +227,8 @@ pub enum SideEffects {
     Unspecified,
     /// "sideEffects": false
     False,
-    /// "sideEffects": ["file.js", "other.js"]
-    Map(SideEffectsMap),
+    /// "sideEffects": ["file.js", "./other.js"]
+    Map(ExactEntries),
     /// "sideEffects": ["side_effects/*.js"]
     Glob(GlobList),
     /// "sideEffects": ["file.js", "side_effects/*.js"] - mixed patterns
@@ -237,52 +237,128 @@ pub enum SideEffects {
 
 type SideEffectsMap = bun_collections::HashMap<StringHashMapUnownedKey, ()>;
 
-type GlobList = Vec<glob::Prepared<Box<[u8]>>>;
+type GlobList = Box<[glob::Prepared<Box<[u8]>>]>;
+
+/// The entries that have no glob syntax, as one set of keys: a resolved file costs one lookup, however long the list is.
+#[derive(Default)]
+pub struct ExactEntries {
+    keys: SideEffectsMap,
+    /// An entry with a path separator is keyed by its path, joined onto the package directory.
+    has_paths: bool,
+    /// An entry without one is keyed as written. It is a file name, and lists that file in every directory.
+    has_names: bool,
+}
 
 pub struct MixedPatterns {
-    pub(crate) exact: SideEffectsMap,
+    pub(crate) exact: ExactEntries,
     pub(crate) globs: GlobList,
 }
 
+impl ExactEntries {
+    #[inline(always)]
+    fn contains(&self, path: &[u8]) -> bool {
+        (self.has_paths && self.has_key(path)) || (self.has_names && self.has_name_of(path))
+    }
+
+    #[inline(always)]
+    fn has_key(&self, key: &[u8]) -> bool {
+        self.keys.contains_key(&StringHashMapUnownedKey::init(key))
+    }
+
+    fn has_name_of(&self, path: &[u8]) -> bool {
+        self.has_key(bun_paths::basename(path))
+    }
+}
+
+fn is_glob(entry: &[u8]) -> bool {
+    strings::contains_any(entry, b"*?[{") || glob::has_extglob_prefix(entry)
+}
+
+#[inline(always)]
+fn any_glob_matches(globs: &[glob::Prepared<Box<[u8]>>], path: &[u8]) -> bool {
+    if globs.is_empty() {
+        return false;
+    }
+    // Normalize path for cross-platform glob matching
+    let Ok(normalized_path) = PackageJSON::normalize_path_for_glob(path) else {
+        return true;
+    };
+    for pattern in globs {
+        if pattern.r#match(&normalized_path).matches() {
+            return true;
+        }
+    }
+    false
+}
+
 impl SideEffects {
     pub(crate) fn has_side_effects(&self, path: &[u8]) -> bool {
         match self {
             SideEffects::Unspecified => true,
             SideEffects::False => false,
-            SideEffects::Map(map) => map.contains_key(&StringHashMapUnownedKey::init(path)),
-            SideEffects::Glob(glob_list) => {
-                // Normalize path for cross-platform glob matching
-                let Ok(normalized_path) = PackageJSON::normalize_path_for_glob(path) else {
-                    return true;
-                };
-
-                for pattern in glob_list.iter() {
-                    if pattern.r#match(&normalized_path).matches() {
-                        return true;
-                    }
-                }
-                false
-            }
+            SideEffects::Map(exact) => exact.contains(path),
+            SideEffects::Glob(globs) => any_glob_matches(globs, path),
             SideEffects::Mixed(mixed) => {
-                // First check exact matches
-                if mixed
-                    .exact
-                    .contains_key(&StringHashMapUnownedKey::init(path))
-                {
-                    return true;
-                }
-                // Then check glob patterns with normalized path
-                let Ok(normalized_path) = PackageJSON::normalize_path_for_glob(path) else {
-                    return true;
-                };
+                mixed.exact.contains(path) || any_glob_matches(&mixed.globs, path)
+            }
+        }
+    }
 
-                for pattern in mixed.globs.iter() {
-                    if pattern.r#match(&normalized_path).matches() {
-                        return true;
-                    }
-                }
-                false
+    /// An entry without a path separator lists a file in every directory, as in webpack and esbuild. Any other is a path from `package_dir`.
+    fn from_array(
+        items: &[js_ast::E::JsonValue],
+        package_dir: &[u8],
+        r_fs: &fs::FileSystem,
+    ) -> SideEffects {
+        let entries = || items.iter().filter_map(|item| item.as_str());
+        let has_globs = entries().any(is_glob);
+        let has_exact = entries().any(|entry| !is_glob(entry));
+        // Only a list without a glob stores its `.css` entries. dce/PackageJsonSideEffectsCSSEntries pins what that changes.
+        let stored =
+            || entries().filter(|entry| !(has_globs && bun_paths::extension(entry) == b".css"));
+        let glob_count = stored().filter(|entry| is_glob(entry)).count();
+
+        let mut exact = ExactEntries {
+            keys: SideEffectsMap::with_capacity(stored().count() - glob_count),
+            ..Default::default()
+        };
+        let mut globs = Vec::with_capacity(glob_count);
+        let mut spill: Vec<u8> = Vec::new();
+
+        for entry in stored() {
+            let has_separator = strings::contains_any(entry, b"/\\");
+            if !is_glob(entry) {
+                let key = if has_separator {
+                    r_fs.join(&mut spill, &[package_dir, entry])
+                } else {
+                    entry
+                };
+                exact.has_paths |= has_separator;
+                exact.has_names |= !has_separator;
+                let _ = exact.keys.insert(StringHashMapUnownedKey::init(key), ());
+                continue;
             }
+            let pattern = if has_separator {
+                let mut joined = r_fs.join(&mut spill, &[package_dir, entry]).to_vec();
+                // Normalize pattern to use forward slashes for cross-platform compatibility
+                bun_paths::slashes_to_posix_in_place(&mut joined[..]);
+                joined
+            } else {
+                // No directory in the pattern, so the name of a directory is never glob syntax.
+                [&b"**/"[..], entry].concat()
+            };
+            globs.push(glob::Prepared::new(pattern.into_boxed_slice()));
+        }
+
+        match (has_globs, has_exact) {
+            // If the array is empty, treat it as false (no side effects)
+            (false, false) => SideEffects::False,
+            (false, true) => SideEffects::Map(exact),
+            (true, false) => SideEffects::Glob(globs.into_boxed_slice()),
+            (true, true) => SideEffects::Mixed(MixedPatterns {
+                exact,
+                globs: globs.into_boxed_slice(),
+            }),
         }
     }
 }
@@ -704,110 +780,11 @@ impl PackageJSON {
                     package_json.side_effects = SideEffects::False;
                 }
             } else if let js_ast::ExprData::EArrayJSON(e_array) = &side_effects_field.data {
-                // Handle arrays, including empty arrays
-                let items = e_array.get().items();
-                let mut map = SideEffectsMap::default();
-                let mut glob_list = GlobList::default();
-                let mut has_globs = false;
-                let mut has_exact = false;
-
-                // First pass: check if we have glob patterns and exact patterns
-                for item in items {
-                    if let Some(name) = item.as_str() {
-                        if strings::contains_char(name, b'*')
-                            || strings::contains_char(name, b'?')
-                            || strings::contains_char(name, b'[')
-                            || strings::contains_char(name, b'{')
-                            || glob::has_extglob_prefix(name)
-                        {
-                            has_globs = true;
-                        } else {
-                            has_exact = true;
-                        }
-                    }
-                }
-
-                let mut spill: Vec<u8> = Vec::new();
-
-                // If the array is empty, treat it as false (no side effects)
-                if !has_globs && !has_exact {
-                    package_json.side_effects = SideEffects::False;
-                } else if has_globs && has_exact {
-                    // Mixed patterns - use both exact and glob matching
-                    map.reserve(items.len());
-                    glob_list.reserve(items.len());
-
-                    for item in items {
-                        if let Some(name) = item.as_str() {
-                            // Skip CSS files as they're not relevant for tree-shaking
-                            if bun_paths::extension(name) == b".css" {
-                                continue;
-                            }
-
-                            // Store the pattern relative to the package directory
-                            let joined: [&[u8]; 2] =
-                                [json_source.path.name().dir_with_trailing_slash(), name];
-
-                            let pattern = r_fs.join(&mut spill, &joined);
-
-                            if strings::contains_char(name, b'*')
-                                || strings::contains_char(name, b'?')
-                                || strings::contains_char(name, b'[')
-                                || strings::contains_char(name, b'{')
-                                || glob::has_extglob_prefix(name)
-                            {
-                                // Normalize pattern to use forward slashes for cross-platform compatibility
-                                let normalized_pattern = Self::normalize_path_for_glob(pattern)
-                                    .unwrap_or_else(|_| pattern.to_vec());
-                                glob_list.push(glob::Prepared::new(
-                                    normalized_pattern.into_boxed_slice(),
-                                ));
-                            } else {
-                                let _ = map.insert(StringHashMapUnownedKey::init(pattern), ());
-                            }
-                        }
-                    }
-                    package_json.side_effects = SideEffects::Mixed(MixedPatterns {
-                        exact: map,
-                        globs: glob_list,
-                    });
-                } else if has_globs {
-                    // Only glob patterns
-                    glob_list.reserve(items.len());
-                    for item in items {
-                        if let Some(name) = item.as_str() {
-                            // Skip CSS files as they're not relevant for tree-shaking
-                            if bun_paths::extension(name) == b".css" {
-                                continue;
-                            }
-
-                            // Store the pattern relative to the package directory
-                            let joined: [&[u8]; 2] =
-                                [json_source.path.name().dir_with_trailing_slash(), name];
-
-                            let pattern = r_fs.join(&mut spill, &joined);
-                            // Normalize pattern to use forward slashes for cross-platform compatibility
-                            let normalized_pattern = Self::normalize_path_for_glob(pattern)
-                                .unwrap_or_else(|_| pattern.to_vec());
-                            glob_list
-                                .push(glob::Prepared::new(normalized_pattern.into_boxed_slice()));
-                        }
-                    }
-                    package_json.side_effects = SideEffects::Glob(glob_list);
-                } else {
-                    // Only exact matches
-                    map.reserve(items.len());
-                    for item in items {
-                        if let Some(name) = item.as_str() {
-                            let joined: [&[u8]; 2] =
-                                [json_source.path.name().dir_with_trailing_slash(), name];
-
-                            let pattern = r_fs.join(&mut spill, &joined);
-                            let _ = map.insert(StringHashMapUnownedKey::init(pattern), ());
-                        }
-                    }
-                    package_json.side_effects = SideEffects::Map(map);
-                }
+                package_json.side_effects = SideEffects::from_array(
+                    e_array.get().items(),
+                    json_source.path.name().dir_with_trailing_slash(),
+                    r_fs,
+                );
             }
         }
 
diff --git a/test/bundler/bundler_barrel.test.ts b/test/bundler/bundler_barrel.test.ts
index 5cb287c7b1b2..08dba30c2888 100644
--- a/test/bundler/bundler_barrel.test.ts
+++ b/test/bundler/bundler_barrel.test.ts
@@ -150,6 +150,41 @@ describe("bundler", () => {
     },
   });
 
+  // An entry without "/" lists the file in every directory of the package.
+  for (const [id, entry] of [
+    ["FileName", "effect.js"],
+    ["GlobWithoutSlash", "effect.*"],
+  ]) {
+    itBundled(`barrel/SideEffectsArray${id}KeepsListedReExport`, {
+      files: {
+        "/entry.js": /* js */ `
+          import { plain } from 'effectful';
+          console.log(plain('x'));
+        `,
+        "/node_modules/effectful/package.json": JSON.stringify({
+          name: "effectful",
+          main: "./src/index.js",
+          sideEffects: [entry],
+        }),
+        "/node_modules/effectful/src/index.js": /* js */ `
+          export { plain } from './plain.js';
+          export { TABLE } from './effect.js';
+        `,
+        "/node_modules/effectful/src/plain.js": /* js */ `
+          export const plain = s => s + "!";
+        `,
+        "/node_modules/effectful/src/effect.js": /* js */ `
+          export const TABLE = {};
+          TABLE.marker = "THE_SIDE_EFFECT_RAN";
+        `,
+      },
+      outdir: "/out",
+      onAfterBundle(api) {
+        api.expectFile("/out/entry.js").toContain("THE_SIDE_EFFECT_RAN");
+      },
+    });
+  }
+
   // A module the array does not list is still tree-shaken away.
   itBundled("barrel/SideEffectsArrayDropsUnlistedReExport", {
     files: {
diff --git a/test/bundler/esbuild/dce.test.ts b/test/bundler/esbuild/dce.test.ts
index f3f159d484c3..37ecbb603910 100644
--- a/test/bundler/esbuild/dce.test.ts
+++ b/test/bundler/esbuild/dce.test.ts
@@ -1,4 +1,5 @@
 import { describe, expect } from "bun:test";
+import { isWindows } from "harness";
 import { dedent, itBundled } from "../expectBundled";
 
 // Tests ported from:
@@ -801,6 +802,463 @@ describe("bundler", () => {
       stdout: "main effect - should be preserved\ndone",
     },
   });
+  // An entry without "/" lists a file in every directory of the package, as in webpack and esbuild.
+  for (const backend of ["cli", "api"] as const) {
+    itBundled(`dce/PackageJsonSideEffectsNoSlashAnyDirectory-${backend}`, {
+      backend,
+      files: {
+        "/Users/user/project/src/entry.js": /* js */ `
+          import "demo-pkg/root.side.js";
+          import "demo-pkg/deep/nested.side.js";
+          import "demo-pkg/.hidden/x.side.js";
+          import "demo-pkg/deep/.dot.side.js";
+          import "demo-pkg/polyfill.js";
+          import "demo-pkg/comp/polyfill.js";
+          import "demo-pkg/deep/unlisted.js";
+          console.log("done");
+        `,
+        "/Users/user/project/node_modules/demo-pkg/root.side.js": `console.log("root glob")`,
+        "/Users/user/project/node_modules/demo-pkg/deep/nested.side.js": `console.log("nested glob")`,
+        "/Users/user/project/node_modules/demo-pkg/.hidden/x.side.js": `console.log("dot directory")`,
+        "/Users/user/project/node_modules/demo-pkg/deep/.dot.side.js": `console.log("dotfile")`,
+        "/Users/user/project/node_modules/demo-pkg/polyfill.js": `console.log("root name")`,
+        "/Users/user/project/node_modules/demo-pkg/comp/polyfill.js": `console.log("nested name")`,
+        "/Users/user/project/node_modules/demo-pkg/deep/unlisted.js": `console.log("TEST FAILED")`,
+        "/Users/user/project/node_modules/demo-pkg/package.json": /* json */ `
+          {
+            "sideEffects": ["*.side.js", "polyfill.js"]
+          }
+        `,
+      },
+      dce: true,
+      run: {
+        stdout: "root glob\nnested glob\ndot directory\ndotfile\nroot name\nnested name\ndone",
+      },
+    });
+  }
+  itBundled("dce/PackageJsonSideEffectsGlobNoSlashMatchesNested", {
+    files: {
+      "/Users/user/project/src/entry.js": /* js */ `
+        import "demo-pkg/root.side.js";
+        import "demo-pkg/deep/nested.side.js";
+        import "demo-pkg/deep/also/here.side.js";
+        import "demo-pkg/deep/unrelated.js";
+        console.log("done");
+      `,
+      "/Users/user/project/node_modules/demo-pkg/root.side.js": `console.log("root kept")`,
+      "/Users/user/project/node_modules/demo-pkg/deep/nested.side.js": `console.log("nested kept")`,
+      "/Users/user/project/node_modules/demo-pkg/deep/also/here.side.js": `console.log("deeper kept")`,
+      "/Users/user/project/node_modules/demo-pkg/deep/unrelated.js": `console.log("TEST FAILED")`,
+      "/Users/user/project/node_modules/demo-pkg/package.json": /* json */ `
+        {
+          "sideEffects": ["*.side.js"]
+        }
+      `,
+    },
+    dce: true,
+    run: {
+      stdout: "root kept\nnested kept\ndeeper kept\ndone",
+    },
+  });
+  itBundled("dce/PackageJsonSideEffectsBareNameMatchesNested", {
+    files: {
+      "/Users/user/project/src/entry.js": /* js */ `
+        import "demo-pkg/polyfill.js";
+        import "demo-pkg/comp/polyfill.js";
+        import "demo-pkg/comp/other.js";
+        console.log("done");
+      `,
+      "/Users/user/project/node_modules/demo-pkg/polyfill.js": `console.log("root poly kept")`,
+      "/Users/user/project/node_modules/demo-pkg/comp/polyfill.js": `console.log("nested poly kept")`,
+      "/Users/user/project/node_modules/demo-pkg/comp/other.js": `console.log("TEST FAILED")`,
+      "/Users/user/project/node_modules/demo-pkg/package.json": /* json */ `
+        {
+          "sideEffects": ["polyfill.js"]
+        }
+      `,
+    },
+    dce: true,
+    run: {
+      stdout: "root poly kept\nnested poly kept\ndone",
+    },
+  });
+  itBundled("dce/PackageJsonSideEffectsMixedNoSlashAndPath", {
+    files: {
+      "/Users/user/project/src/entry.js": /* js */ `
+        import "demo-pkg/lib/effect.side.js";
+        import "demo-pkg/lib/specific.js";
+        import "demo-pkg/comp/polyfill.js";
+        import "demo-pkg/lib/drop.js";
+        console.log("done");
+      `,
+      "/Users/user/project/node_modules/demo-pkg/lib/effect.side.js": `console.log("glob kept")`,
+      "/Users/user/project/node_modules/demo-pkg/lib/specific.js": `console.log("exact kept")`,
+      "/Users/user/project/node_modules/demo-pkg/comp/polyfill.js": `console.log("bare kept")`,
+      "/Users/user/project/node_modules/demo-pkg/lib/drop.js": `console.log("TEST FAILED")`,
+      "/Users/user/project/node_modules/demo-pkg/package.json": /* json */ `
+        {
+          "sideEffects": ["*.side.js", "./lib/specific.js", "polyfill.js"]
+        }
+      `,
+    },
+    dce: true,
+    run: {
+      stdout: "glob kept\nexact kept\nbare kept\ndone",
+    },
+  });
+  itBundled("dce/PackageJsonSideEffectsStarListsEveryFile", {
+    files: {
+      "/Users/user/project/src/entry.js": /* js */ `
+        import "demo-pkg/a.js";
+        import "demo-pkg/deep/b.js";
+        import "demo-pkg/deep/.hidden/c.js";
+        console.log("done");
+      `,
+      "/Users/user/project/node_modules/demo-pkg/a.js": `console.log("a")`,
+      "/Users/user/project/node_modules/demo-pkg/deep/b.js": `console.log("b")`,
+      "/Users/user/project/node_modules/demo-pkg/deep/.hidden/c.js": `console.log("c")`,
+      "/Users/user/project/node_modules/demo-pkg/package.json": /* json */ `
+        {
+          "sideEffects": ["*"]
+        }
+      `,
+    },
+    run: {
+      stdout: "a\nb\nc\ndone",
+    },
+  });
+  itBundled("dce/PackageJsonSideEffectsBareCSSAndJS", {
+    files: {
+      "/Users/user/project/src/entry.js": /* js */ `
+        import "demo-pkg/style.css";
+        import "demo-pkg/setup.js";
+        import "demo-pkg/lib/setup.js";
+        import "demo-pkg/lib/other.js";
+        console.log("done");
+      `,
+      "/Users/user/project/node_modules/demo-pkg/style.css": `body { color: red; }`,
+      "/Users/user/project/node_modules/demo-pkg/setup.js": `console.log("root setup kept")`,
+      "/Users/user/project/node_modules/demo-pkg/lib/setup.js": `console.log("nested setup kept")`,
+      "/Users/user/project/node_modules/demo-pkg/lib/other.js": `console.log("TEST FAILED")`,
+      "/Users/user/project/node_modules/demo-pkg/package.json": /* json */ `
+        {
+          "sideEffects": ["style.css", "setup.js"]
+        }
+      `,
+    },
+    outdir: "/out",
+    dce: true,
+    dceKeepMarkerCount: false,
+    run: {
+      stdout: "root setup kept\nnested setup kept\ndone",
+    },
+    onAfterBundle(api) {
+      api.expectFile("/out/entry.css").toContain("color: red");
+    },
+  });
+  // The list of a package that has a name, reached through the index of the package.
+  itBundled("dce/PackageJsonSideEffectsNoSlashInNamedPackage", {
+    files: {
+      "/Users/user/project/src/entry.js": /* js */ `
+        import { v } from "@scope/ui";
+        console.log(v);
+      `,
+      "/Users/user/project/node_modules/@scope/ui/index.js": /* js */ `
+        import "./root.side.js";
+        import "./sub/deep.side.js";
+        import "./comp/polyfill.js";
+        import "./sub/unlisted.js";
+        export const v = "done";
+      `,
+      "/Users/user/project/node_modules/@scope/ui/root.side.js": `console.log("root glob")`,
+      "/Users/user/project/node_modules/@scope/ui/sub/deep.side.js": `console.log("nested glob")`,
+      "/Users/user/project/node_modules/@scope/ui/comp/polyfill.js": `console.log("nested name")`,
+      "/Users/user/project/node_modules/@scope/ui/sub/unlisted.js": `console.log("TEST FAILED")`,
+      "/Users/user/project/node_modules/@scope/ui/package.json": /* json */ `
+        {
+          "name": "@scope/ui",
+          "version": "1.0.0",
+          "main": "index.js",
+          "sideEffects": ["*.side.js", "polyfill.js"]
+        }
+      `,
+    },
+    dce: true,
+    run: {
+      stdout: "root glob\nnested glob\nnested name\ndone",
+    },
+  });
+  // The list of the project itself, for files that the project imports by relative path.
+  itBundled("dce/PackageJsonSideEffectsNoSlashInProjectPackage", {
+    files: {
+      "/Users/user/project/src/entry.js": /* js */ `
+        import "./deep/nested.side.js";
+        import "./deep/polyfill.js";
+        import "./deep/unlisted.js";
+        console.log("done");
+      `,
+      "/Users/user/project/src/deep/nested.side.js": `console.log("nested glob")`,
+      "/Users/user/project/src/deep/polyfill.js": `console.log("nested name")`,
+      "/Users/user/project/src/deep/unlisted.js": `console.log("TEST FAILED")`,
+      "/Users/user/project/package.json": /* json */ `
+        {
+          "name": "app",
+          "sideEffects": ["*.side.js", "polyfill.js"]
+        }
+      `,
+    },
+    dce: true,
+    run: {
+      stdout: "nested glob\nnested name\ndone",
+    },
+  });
+  // An entry without "/" has no directory, so it also lists a file that "main" reaches outside the package.
+  itBundled("dce/PackageJsonSideEffectsNoSlashOutsidePackage", {
+    files: {
+      "/Users/user/project/src/entry.js": /* js */ `
+        import "by-name";
+        import "by-glob";
+        console.log("done");
+      `,
+      "/Users/user/project/node_modules/shared/x.js": `console.log("name outside")`,
+      "/Users/user/project/node_modules/shared/y.js": `console.log("glob outside")`,
+      "/Users/user/project/node_modules/by-name/package.json": /* json */ `
+        {
+          "name": "by-name",
+          "main": "../shared/x.js",
+          "sideEffects": ["x.js"]
+        }
+      `,
+      "/Users/user/project/node_modules/by-glob/package.json": /* json */ `
+        {
+          "name": "by-glob",
+          "main": "../shared/y.js",
+          "sideEffects": ["y.*"]
+        }
+      `,
+    },
+    run: {
+      stdout: "name outside\nglob outside\ndone",
+    },
+  });
+  // A file that the list names keeps its side effects when an onLoad plugin turns it into JavaScript.
+  itBundled("dce/PackageJsonSideEffectsListedFileLoadedByPlugin", {
+    files: {
+      "/Users/user/project/src/entry.js": /* js */ `
+        import "demo-pkg/root.scss";
+        import "demo-pkg/scss/theme.scss";
+        import "demo-pkg/scss/unlisted.less";
+        console.log("done");
+      `,
+      "/Users/user/project/node_modules/demo-pkg/root.scss": `.root { color: red }`,
+      "/Users/user/project/node_modules/demo-pkg/scss/theme.scss": `.theme { color: blue }`,
+      "/Users/user/project/node_modules/demo-pkg/scss/unlisted.less": `TEST FAILED`,
+      "/Users/user/project/node_modules/demo-pkg/package.json": /* json */ `
+        {
+          "sideEffects": ["./lib/common.js", "*.css", "*.scss"]
+        }
+      `,
+    },
+    plugins(builder) {
+      builder.onLoad({ filter: /\.(scss|less)$/ }, async args => ({
+        contents: `console.log(${JSON.stringify((await Bun.file(args.path).text()).trim())})`,
+        loader: "js",
+      }));
+    },
+    run: {
+      stdout: ".root { color: red }\n.theme { color: blue }\ndone",
+    },
+  });
+  // Today a list with a glob is asked a second time through the nearest package.json that has a name, and that
+  // answer wins. A list of file names has no glob, so its own answer stands. This fails if a file name is a glob.
+  itBundled("dce/PackageJsonSideEffectsFileNameInPackageWithoutName", {
+    files: {
+      "/Users/user/project/src/entry.js": /* js */ `
+        import "no-name/polyfill.js";
+        import "no-name/sub/polyfill.js";
+        import "no-name/sub/unlisted.js";
+        console.log("done");
+      `,
+      "/Users/user/project/package.json": /* json */ `
+        {
+          "name": "app",
+          "sideEffects": false
+        }
+      `,
+      "/Users/user/project/node_modules/no-name/polyfill.js": `console.log("root name")`,
+      "/Users/user/project/node_modules/no-name/sub/polyfill.js": `console.log("nested name")`,
+      "/Users/user/project/node_modules/no-name/sub/unlisted.js": `console.log("TEST FAILED")`,
+      "/Users/user/project/node_modules/no-name/package.json": /* json */ `
+        {
+          "sideEffects": ["polyfill.js"]
+        }
+      `,
+    },
+    dce: true,
+    run: {
+      stdout: "root name\nnested name\ndone",
+    },
+  });
+  // "[slug]" in the path of the package is not a character class for an entry without "/".
+  itBundled("dce/PackageJsonSideEffectsNoSlashUnderBracketDirectory", {
+    files: {
+      "/Users/user/project/[slug]/src/entry.js": /* js */ `
+        import "demo-pkg/root.side.js";
+        import "demo-pkg/deep/nested.side.js";
+        import "demo-pkg/polyfill.js";
+        import "demo-pkg/deep/polyfill.js";
+        import "demo-pkg/deep/unlisted.js";
+        console.log("done");
+      `,
+      "/Users/user/project/[slug]/node_modules/demo-pkg/root.side.js": `console.log("root glob")`,
+      "/Users/user/project/[slug]/node_modules/demo-pkg/deep/nested.side.js": `console.log("nested glob")`,
+      "/Users/user/project/[slug]/node_modules/demo-pkg/polyfill.js": `console.log("root name")`,
+      "/Users/user/project/[slug]/node_modules/demo-pkg/deep/polyfill.js": `console.log("nested name")`,
+      "/Users/user/project/[slug]/node_modules/demo-pkg/deep/unlisted.js": `console.log("TEST FAILED")`,
+      "/Users/user/project/[slug]/node_modules/demo-pkg/package.json": /* json */ `
+        {
+          "sideEffects": ["*.side.js", "polyfill.js"]
+        }
+      `,
+    },
+    dce: true,
+    run: {
+      stdout: "root glob\nnested glob\nroot name\nnested name\ndone",
+    },
+  });
+  // An entry with "/" is a path from the directory of the package.json.
+  itBundled("dce/PackageJsonSideEffectsEntryWithSlashIsAPath", {
+    files: {
+      "/Users/user/project/src/entry.js": /* js */ `
+        import "demo-pkg/polyfill.js";
+        import "demo-pkg/lib/polyfill.js";
+        import "demo-pkg/root.side.js";
+        import "demo-pkg/lib/nested.side.js";
+        import "demo-pkg/comp/setup.js";
+        import "demo-pkg/lib/comp/setup.js";
+        console.log("done");
+      `,
+      "/Users/user/project/node_modules/demo-pkg/polyfill.js": `console.log("root name")`,
+      "/Users/user/project/node_modules/demo-pkg/lib/polyfill.js": `console.log("TEST FAILED")`,
+      "/Users/user/project/node_modules/demo-pkg/root.side.js": `console.log("root glob")`,
+      "/Users/user/project/node_modules/demo-pkg/lib/nested.side.js": `console.log("TEST FAILED")`,
+      "/Users/user/project/node_modules/demo-pkg/comp/setup.js": `console.log("comp path")`,
+      "/Users/user/project/node_modules/demo-pkg/lib/comp/setup.js": `console.log("TEST FAILED")`,
+      "/Users/user/project/node_modules/demo-pkg/package.json": /* json */ `
+        {
+          "sideEffects": ["./polyfill.js", "./*.side.js", "comp/setup.js"]
+        }
+      `,
+    },
+    dce: true,
+    run: {
+      stdout: "root name\nroot glob\ncomp path\ndone",
+    },
+  });
+  // An entry with "\\" is a path, as one with "/" is. With glob syntax its "\\" becomes "/" on every platform.
+  // Without glob syntax it is joined as written: a directory separator on Windows, a part of the name elsewhere.
+  itBundled("dce/PackageJsonSideEffectsEntryWithBackslashIsAPath", {
+    files: {
+      "/Users/user/project/src/entry.js": /* js */ `
+        import "demo-pkg/sub/effect.js";
+        import "demo-pkg/globbed/x.js";
+        import "demo-pkg/deep/globbed/x.js";
+        console.log("done");
+      `,
+      "/Users/user/project/node_modules/demo-pkg/sub/effect.js": `console.log("sub effect")`,
+      "/Users/user/project/node_modules/demo-pkg/globbed/x.js": `console.log("globbed x")`,
+      "/Users/user/project/node_modules/demo-pkg/deep/globbed/x.js": `console.log("TEST FAILED")`,
+      "/Users/user/project/node_modules/demo-pkg/package.json": /* json */ `
+        {
+          "sideEffects": ["sub\\\\effect.js", "globbed\\\\*.js"]
+        }
+      `,
+    },
+    dce: true,
+    run: {
+      stdout: isWindows ? "sub effect\nglobbed x\ndone" : "globbed x\ndone",
+    },
+  });
+  itBundled("dce/PackageJsonSideEffectsExactListInPackageWithoutName", {
+    files: {
+      "/Users/user/project/src/entry.js": /* js */ `
+        import "no-name/listed.js";
+        import "no-name/unlisted.js";
+        console.log("done");
+      `,
+      "/Users/user/project/package.json": /* json */ `
+        {
+          "name": "app",
+          "sideEffects": false
+        }
+      `,
+      "/Users/user/project/node_modules/no-name/listed.js": `console.log("listed")`,
+      "/Users/user/project/node_modules/no-name/unlisted.js": `console.log("TEST FAILED")`,
+      "/Users/user/project/node_modules/no-name/package.json": /* json */ `
+        {
+          "sideEffects": ["./listed.js"]
+        }
+      `,
+    },
+    dce: true,
+    run: {
+      stdout: "listed\ndone",
+    },
+  });
+  // A list that has a glob does not store its ".css" entries, and a list without a glob stores them. This pins
+  // that difference as it is. The CSS is in the bundle either way. A lazily loaded importer keeps an empty
+  // initializer for a CSS file with side effects.
+  itBundled("dce/PackageJsonSideEffectsCSSEntries", {
+    files: {
+      "/Users/user/project/src/entry.js": /* js */ `
+        console.log(require("with-glob").name, require("with-both").name, require("with-path").name);
+      `,
+      "/Users/user/project/node_modules/with-glob/index.js": /* js */ `
+        import "./sub/globbed.css";
+        export const name = "glob";
+      `,
+      "/Users/user/project/node_modules/with-glob/sub/globbed.css": `.globbed { color: red; }`,
+      "/Users/user/project/node_modules/with-glob/package.json": /* json */ `
+        {
+          "sideEffects": ["*.css"]
+        }
+      `,
+      "/Users/user/project/node_modules/with-both/index.js": /* js */ `
+        import "./sub/mixed.css";
+        export const name = "both";
+      `,
+      "/Users/user/project/node_modules/with-both/sub/mixed.css": `.mixed { color: green; }`,
+      "/Users/user/project/node_modules/with-both/package.json": /* json */ `
+        {
+          "sideEffects": ["./sub/mixed.css", "./*.side.js"]
+        }
+      `,
+      "/Users/user/project/node_modules/with-path/index.js": /* js */ `
+        import "./sub/exact.css";
+        export const name = "path";
+      `,
+      "/Users/user/project/node_modules/with-path/sub/exact.css": `.exact { color: blue; }`,
+      "/Users/user/project/node_modules/with-path/package.json": /* json */ `
+        {
+          "sideEffects": ["./sub/exact.css"]
+        }
+      `,
+    },
+    outdir: "/out",
+    run: {
+      stdout: "glob both path",
+    },
+    onAfterBundle(api) {
+      const js = api.readFile("/out/entry.js");
+      expect(js).not.toContain("init_globbed");
+      expect(js).not.toContain("init_mixed");
+      expect(js).toContain("init_exact");
+      const css = api.readFile("/out/entry.css");
+      expect(css).toContain(".globbed");
+      expect(css).toContain(".mixed");
+      expect(css).toContain(".exact");
+    },
+  });
   itBundled("dce/PackageJsonSideEffectsGlobInvalidPattern", {
     files: {
       "/Users/user/project/src/entry.js": /* js */ `
diff --git a/test/bundler/esbuild/extra.test.ts b/test/bundler/esbuild/extra.test.ts
index 7cd5621a0b63..6db05156de97 100644
--- a/test/bundler/esbuild/extra.test.ts
+++ b/test/bundler/esbuild/extra.test.ts
@@ -1314,7 +1314,6 @@ describe("bundler", () => {
       "foo/dir/x.js": `global.dce6 = 123`,
       "foo/package.json": `{ "main": "dir/x", "sideEffects": ["x.*"] }`,
     },
-    skipIfWeDidNotImplementWildcardSideEffects: true,
     run: true,
   });
   itBundled(`extra/TreeShaking9`, {
@@ -1323,7 +1322,6 @@ describe("bundler", () => {
       "foo/dir/x.js": `global.dce6 = 123`,
       "foo/package.json": `{ "main": "dir/x", "sideEffects": ["**/x.*"] }`,
     },
-    skipIfWeDidNotImplementWildcardSideEffects: true,
     run: true,
   });
   itBundled(`extra/TreeShaking10`, {
diff --git a/test/bundler/expectBundled.ts b/test/bundler/expectBundled.ts
index ad5ccafccb1e..0b9d1e4cd863 100644
--- a/test/bundler/expectBundled.ts
+++ b/test/bundler/expectBundled.ts
@@ -344,9 +344,6 @@ export interface BundlerTestInput {
   /** Run after bundle happens but before runtime. */
   onAfterBundle?(api: BundlerTestBundleAPI): Promise<void> | void;
 
-  /* TODO: remove this from the tests after this is implemented */
-  skipIfWeDidNotImplementWildcardSideEffects?: boolean;
-
   snapshotSourceMap?: Record<string, SourceMapTests>;
 
   expectExactFilesize?: Record<string, number>;
@@ -575,7 +572,6 @@ function expectBundled(
     mangleProps,
     mangleQuoted,
     nodePaths,
-    skipIfWeDidNotImplementWildcardSideEffects,
     stdin,
     targetFromAPI,
     mode,
@@ -634,7 +630,6 @@ function expectBundled(
     mangleProps,
     mangleQuoted,
     nodePaths,
-    skipIfWeDidNotImplementWildcardSideEffects,
     stdin,
     targetFromAPI,
   })) {