diff --git a/tests/test_app_js.py b/tests/test_app_js.py
index 90964f02..74df85ad 100644
--- a/tests/test_app_js.py
+++ b/tests/test_app_js.py
@@ -1350,6 +1350,10 @@ def test_redact_credentials_runtime_smoke() -> None:
         + "const apg = redactCredentials('postgresql+asyncpg://user:s3cret@db/app');\n"
         + "if (apg !== 'postgresql+asyncpg://user:[REDACTED:password]@db/app') "
         + "throw new Error('asyncpg conn redact failed: ' + apg);\n"
+        + "// RFC 3986 schemes are case-insensitive - uppercase must not bypass\n"
+        + "const up = redactCredentials('POSTGRESQL+PSYCOPG2://user:s3cret@db/app');\n"
+        + "if (up !== 'POSTGRESQL+PSYCOPG2://user:[REDACTED:password]@db/app') "
+        + "throw new Error('uppercase scheme conn redact failed: ' + up);\n"
     )
     with tempfile.NamedTemporaryFile(mode="w", suffix=".mjs", delete=False) as f:
         f.write(harness)
diff --git a/tests/test_output_guard.py b/tests/test_output_guard.py
index e7cb7935..7c6e5264 100644
--- a/tests/test_output_guard.py
+++ b/tests/test_output_guard.py
@@ -250,6 +250,18 @@ class TestCredentialLeakage:
             assert "s3cret_pass" not in r.sanitized, url
             assert ":[REDACTED:password]@" in r.sanitized, url
 
+    def test_uppercase_scheme_connection_string(self) -> None:
+        # RFC 3986 schemes are case-insensitive; an uppercase scheme must
+        # not bypass redaction.
+        for url in (
+            "POSTGRESQL+PSYCOPG2://admin:s3cret_pass@db.internal/prod",
+            "HTTPS://admin:s3cret_pass@api.internal/x",
+        ):
+            r = evaluate_output(url)
+            assert "connection_string_leak" in r.flags, url
+            assert r.sanitized is not None, url
+            assert "s3cret_pass" not in r.sanitized, url
+
     def test_bearer_scheme_case_insensitive(self) -> None:
         # RFC 7235 scheme name is case-insensitive.
         r = evaluate_output("authorization: bearer eyJhbGciOiJIUzI1NiJ9.eyJzdWIiOiIxIn0.sig12345")
diff --git a/turnstone/core/output_guard.py b/turnstone/core/output_guard.py
index 4862755f..4528b9e2 100644
--- a/turnstone/core/output_guard.py
+++ b/turnstone/core/output_guard.py
@@ -98,9 +98,12 @@ _RE_PRIVATE_KEY_BLOCK = re.compile(
 # covers SQLAlchemy dialect+driver URLs (``postgresql+psycopg2``,
 # ``postgresql+asyncpg``, ``mysql+pymysql``) and ``mongodb+srv`` —
 # enumerating drivers is a losing game, the suffix shape isn't.
+# Schemes are case-insensitive per RFC 3986, hence IGNORECASE:
+# ``POSTGRESQL://`` leaks the same password ``postgresql://`` does.
 _RE_CONNECTION_STRING = re.compile(
     r"(?:postgresql|mysql|mongodb|rediss?|amqps?|sqlite|https?)(?:\+[a-z0-9]*)?"
     r"://[^:@\s]+:[^@\s]+@",
+    re.IGNORECASE,
 )
 _RE_ENV_SECRET_LINE = re.compile(r"[A-Z][A-Z_0-9]+=\S+")
 _RE_ENV_SECRET_KEY = re.compile(
diff --git a/turnstone/shared_static/redact_credentials.js b/turnstone/shared_static/redact_credentials.js
index b4d80c5d..dffd01c8 100644
--- a/turnstone/shared_static/redact_credentials.js
+++ b/turnstone/shared_static/redact_credentials.js
@@ -37,10 +37,11 @@ const _RE_PRIVATE_KEY_BLOCK =
 // The optional +suffix covers SQLAlchemy dialect+driver URLs
 // (postgresql+psycopg2, postgresql+asyncpg, mysql+pymysql) and
 // mongodb+srv — enumerating drivers is a losing game, the suffix
-// shape isn't.
+// shape isn't.  Schemes are case-insensitive per RFC 3986 (/i):
+// POSTGRESQL:// leaks the same password postgresql:// does.
 // ---------------------------------------------------------------------------
 const _RE_CONNECTION_STRING =
-  /(?:postgresql|mysql|mongodb|rediss?|amqps?|sqlite|https?)(?:\+[a-z0-9]*)?:\/\/[^:@\s]+:[^@\s]+@/g;
+  /(?:postgresql|mysql|mongodb|rediss?|amqps?|sqlite|https?)(?:\+[a-z0-9]*)?:\/\/[^:@\s]+:[^@\s]+@/gi;
 
 const _RE_CONN_USERINFO = /:\/\/([^:@\s]+):([^@\s]+)@/;