diff --git a/language_service/src/completion.rs b/language_service/src/completion.rs
index 4836e16c28..10e63377b2 100644
--- a/language_service/src/completion.rs
+++ b/language_service/src/completion.rs
@@ -9,7 +9,7 @@ use crate::display::CodeDisplay;
 use crate::protocol::{CompletionItem, CompletionItemKind, CompletionList};
 use crate::qsc_utils::{protocol_span, span_contains};
 use qsc::ast::visit::{self, Visitor};
-use qsc::hir::{ItemKind, Package, PackageId};
+use qsc::hir::{ItemKind, Package, PackageId, Visibility};
 use qsc::resolve::{Local, LocalKind};
 use rustc_hash::FxHashSet;
 use std::rc::Rc;
@@ -385,11 +385,33 @@ impl CompletionListBuilder {
             .package;
         let display = CodeDisplay { compilation };
 
+        let is_user_package = compilation.user_package_id == package_id;
+
         package.items.values().filter_map(move |i| {
             // We only want items whose parents are namespaces
             if let Some(item_id) = i.parent {
                 if let Some(parent) = package.items.get(item_id) {
                     if let ItemKind::Namespace(namespace, _) = &parent.kind {
+                        if namespace.name.starts_with("Microsoft.Quantum.Unstable") {
+                            return None;
+                        }
+                        // If the item's visibility is internal, the item may be ignored
+                        if matches!(i.visibility, Visibility::Internal) {
+                            if !is_user_package {
+                                return None; // ignore item if not in the user's package
+                            }
+                            // ignore item if the user is not in the item's namespace
+                            match &current_namespace_name {
+                                Some(curr_ns) => {
+                                    if *curr_ns != namespace.name {
+                                        return None;
+                                    }
+                                }
+                                None => {
+                                    return None;
+                                }
+                            }
+                        }
                         return match &i.kind {
                             ItemKind::Callable(callable_decl) => {
                                 let name = callable_decl.name.name.as_ref();
@@ -498,10 +520,14 @@ impl CompletionListBuilder {
 
     fn get_namespaces(package: &'_ Package) -> impl Iterator<Item = CompletionItem> + '_ {
         package.items.values().filter_map(|i| match &i.kind {
-            ItemKind::Namespace(namespace, _) => Some(CompletionItem::new(
-                namespace.name.to_string(),
-                CompletionItemKind::Module,
-            )),
+            ItemKind::Namespace(namespace, _)
+                if !namespace.name.starts_with("Microsoft.Quantum.Unstable") =>
+            {
+                Some(CompletionItem::new(
+                    namespace.name.to_string(),
+                    CompletionItemKind::Module,
+                ))
+            }
             _ => None,
         })
     }
diff --git a/language_service/src/completion/tests.rs b/language_service/src/completion/tests.rs
index 1f4747f873..40ff4df7eb 100644
--- a/language_service/src/completion/tests.rs
+++ b/language_service/src/completion/tests.rs
@@ -94,6 +94,147 @@ fn assert_no_duplicates(mut actual_completions: CompletionList) {
     assert!(dups.is_empty(), "duplicate completions found: {dups:#?}");
 }
 
+#[test]
+fn ignore_unstable_namespace() {
+    check(
+        r#"
+        namespace Test {
+            open ↘
+        }"#,
+        &["FakeStdLib", "Microsoft.Quantum.Unstable"],
+        &expect![[r#"
+            [
+                Some(
+                    CompletionItem {
+                        label: "FakeStdLib",
+                        kind: Module,
+                        sort_text: Some(
+                            "1101FakeStdLib",
+                        ),
+                        detail: None,
+                        additional_text_edits: None,
+                    },
+                ),
+                None,
+            ]
+        "#]],
+    );
+}
+
+#[test]
+fn ignore_unstable_callable() {
+    check(
+        r#"
+        namespace Test {
+            open Microsoft.Quantum.Unstable;
+            operation Foo() : Unit {
+                ↘
+            }
+        }"#,
+        &["Fake", "UnstableFake"],
+        &expect![[r#"
+            [
+                Some(
+                    CompletionItem {
+                        label: "Fake",
+                        kind: Function,
+                        sort_text: Some(
+                            "0700Fake",
+                        ),
+                        detail: Some(
+                            "operation Fake() : Unit",
+                        ),
+                        additional_text_edits: Some(
+                            [
+                                (
+                                    Span {
+                                        start: 38,
+                                        end: 38,
+                                    },
+                                    "open FakeStdLib;\n            ",
+                                ),
+                            ],
+                        ),
+                    },
+                ),
+                None,
+            ]
+        "#]],
+    );
+}
+
+#[test]
+fn ignore_internal_callable() {
+    check(
+        r#"
+        namespace Test {
+            internal operation Foo() : Unit {}
+            operation Bar() : Unit {
+                ↘
+            }
+        }
+
+        namespace Test {
+            internal operation Baz() : Unit {}
+        }"#,
+        &["Fake", "Foo", "Baz", "Hidden"],
+        &expect![[r#"
+            [
+                Some(
+                    CompletionItem {
+                        label: "Fake",
+                        kind: Function,
+                        sort_text: Some(
+                            "0700Fake",
+                        ),
+                        detail: Some(
+                            "operation Fake() : Unit",
+                        ),
+                        additional_text_edits: Some(
+                            [
+                                (
+                                    Span {
+                                        start: 38,
+                                        end: 38,
+                                    },
+                                    "open FakeStdLib;\n            ",
+                                ),
+                            ],
+                        ),
+                    },
+                ),
+                Some(
+                    CompletionItem {
+                        label: "Foo",
+                        kind: Function,
+                        sort_text: Some(
+                            "0600Foo",
+                        ),
+                        detail: Some(
+                            "operation Foo() : Unit",
+                        ),
+                        additional_text_edits: None,
+                    },
+                ),
+                Some(
+                    CompletionItem {
+                        label: "Baz",
+                        kind: Function,
+                        sort_text: Some(
+                            "0600Baz",
+                        ),
+                        detail: Some(
+                            "operation Baz() : Unit",
+                        ),
+                        additional_text_edits: None,
+                    },
+                ),
+                None,
+            ]
+        "#]],
+    );
+}
+
 #[test]
 fn in_block_contains_std_functions_from_open_namespace() {
     check(
diff --git a/language_service/src/test_utils.rs b/language_service/src/test_utils.rs
index 055577d4ae..0dcd437e7d 100644
--- a/language_service/src/test_utils.rs
+++ b/language_service/src/test_utils.rs
@@ -134,6 +134,11 @@ fn compile_fake_stdlib() -> (PackageStore, PackageId) {
                     Fake();
                 }
                 operation FakeWithTypeParam<'A>(a : 'A) : 'A { a }
+                internal operation Hidden() : Unit {}
+            }
+
+            namespace Microsoft.Quantum.Unstable {
+                operation UnstableFake() : Unit {}
             }"#
             .into(),
         )],