diff --git a/README.md b/README.md
index aef5a67..c75706e 100644
--- a/README.md
+++ b/README.md
@@ -61,7 +61,7 @@ The authored evaluation benchmark is located in `evaluation/questions.json`, wit
 
 - **No In-Binary Hybrid or Vector Search**: Vector embeddings and hybrid search algorithms exist only in the offline Python script `evaluation/evaluate_hybrid.py`. They are **not** integrated into the Rust product binary, library, or HTTP API.
 - **Heuristic Citation Screening, Not Answer Verification**: The CLI screens some plain `path:line` tokens against retrieved text. This is not a complete citation parser and does not prove that an answer is supported by its sources. The lexical evaluator reports retrieval Recall@5 and MRR only, not answer or citation accuracy.
-- **File Access Policy**: Initial scans and incremental updates exclude hidden path components, common build/dependency directories, `.pem`/`.key` files, and named SSH private keys. Incremental updates reject absolute/parent paths and symlink components. This name-based policy is not a secret scanner and does not defend against a hostile concurrent filesystem mutation.
+- **File Access Policy**: Initial scans and incremental updates exclude hidden path components, common build/dependency directories, `.pem`/`.key` files, and named SSH private keys. Incremental updates reject absolute/parent paths and symlink components. Sensitive-name matching is ASCII case-insensitive, so an alias like `CREDENTIALS.JSON` cannot bypass the policy on a case-insensitive filesystem. This name-based policy is not a secret scanner and does not defend against a hostile concurrent filesystem mutation.
 - **Working-Tree Prototype**: Files are read from the working tree, not an immutable Git snapshot. A `-dirty` label is diagnostic, not a reproducible snapshot identifier. Commit-consistent indexing and complete rename handling remain unfinished.
 - **No Background Watcher**: Background filesystem events are not monitored; synchronization is triggered explicitly via CLI or HTTP `/reload`.
 - **No Production Hardening**: Authentication, TLS, rate limiting, and multi-tenant isolation remain out of scope for this local development prototype.
diff --git a/src/lib.rs b/src/lib.rs
index 6d6012d..02b62e1 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -284,6 +284,7 @@ fn is_indexable(path: &Path) -> bool {
 /// Single source of truth for file names that must never be indexed.
 /// Shared by the full walk and incremental updates so a scan and a rebase agree.
 fn is_sensitive_file_name(name: &str) -> bool {
+    let name = name.to_ascii_lowercase();
     (name.starts_with('.') && name != ".github" && name != ".gitignore")
         || name.ends_with(".pem")
         || name.ends_with(".key")
@@ -463,4 +464,66 @@ mod tests {
             .unwrap();
         assert!(index.search("legacycanary", 5).is_empty());
     }
+
+    #[test]
+    fn sensitive_names_match_case_insensitively() {
+        for name in [
+            "CREDENTIALS.JSON",
+            "Service-Account.json",
+            "CLIENT.P12",
+            "CLIENT.PFX",
+            "RELEASE.KEYSTORE",
+            "ID_RSA",
+            "ID_ED25519",
+            "SERVER.PEM",
+            "SERVER.KEY",
+            ".ENV",
+            ".Env.local",
+        ] {
+            assert!(is_sensitive_file_name(name), "{name} must be sensitive");
+        }
+        for name in ["credentials.rs", "service.rs", "keep.p12.bak"] {
+            assert!(
+                !is_sensitive_file_name(name),
+                "{name} must not be sensitive"
+            );
+        }
+    }
+
+    #[test]
+    fn full_scan_and_update_agree_on_case_variant_sensitive_names() {
+        let root = fixture();
+        fs::create_dir_all(root.join("sub")).unwrap();
+        let sensitive = [
+            "CREDENTIALS.JSON",
+            "Service-Account.json",
+            "CLIENT.P12",
+            "sub/RELEASE.PFX",
+            "sub/KEYSTORE.KEYSTORE",
+            "ID_RSA",
+        ];
+        for name in sensitive {
+            fs::write(root.join(name), "casecanary").unwrap();
+        }
+
+        let mut index = Index::build(&root).unwrap();
+        assert!(index.search("casecanary", 20).is_empty());
+        for name in sensitive {
+            index.update_file(&root, Path::new(name)).unwrap();
+        }
+        assert!(index.search("casecanary", 20).is_empty());
+    }
+
+    #[test]
+    fn update_file_case_alias_cannot_bypass_sensitive_policy() {
+        let root = fixture();
+        fs::write(root.join("credentials.json"), "aliascanary").unwrap();
+        let mut index = Index::build(&root).unwrap();
+        assert!(index.search("aliascanary", 5).is_empty());
+
+        index
+            .update_file(&root, Path::new("CREDENTIALS.JSON"))
+            .unwrap();
+        assert!(index.search("aliascanary", 5).is_empty());
+    }
 }