diff --git a/src/harness_sdk/instrumentation/__init__.py b/src/harness_sdk/instrumentation/__init__.py
index 93af348..9f37ef6 100644
--- a/src/harness_sdk/instrumentation/__init__.py
+++ b/src/harness_sdk/instrumentation/__init__.py
@@ -21,6 +21,24 @@ class BaseInstrumentorWrapper:
     RPC_REQUEST_BODY_PREFIX = 'rpc.request.body'
     RPC_RESPONSE_BODY_PREFIX = 'rpc.response.body'
 
+    # Headers/metadata whose values are credentials or session secrets and must
+    # never be exported verbatim in telemetry. Compared case-insensitively.
+    SENSITIVE_HEADERS = frozenset({
+        'authorization',
+        'proxy-authorization',
+        'x-api-key',
+        'api-key',
+        'apikey',
+        'x-auth-token',
+        'x-amz-security-token',
+        'x-goog-api-key',
+        'cookie',
+        'set-cookie',
+        'x-harness-service-token',
+        'x-harness-token',
+    })
+    REDACTED_VALUE = '[REDACTED]'
+
     # Constructor
     def __init__(self):
         '''constructor'''
@@ -41,10 +59,19 @@ def lowercase_headers(self, headers):
         '''convert all headers to lowercase'''
         return {k.lower(): v for k, v in headers.items()}
 
+    def _redact_if_sensitive(self, header_key: str, header_value):
+        '''Return the header value, redacted if the header is credential-bearing.'''
+        if header_key.lower() in self.SENSITIVE_HEADERS:
+            return self.REDACTED_VALUE
+        return header_value
+
     def add_headers_to_span(self, prefix: str, span: Span, headers: dict):
-        '''set header attributes on the span'''
+        '''set header attributes on the span, redacting sensitive header values'''
         for header_key, header_value in headers.items():
-            span.set_attribute(f"{prefix}{header_key}", header_value)
+            span.set_attribute(
+                f"{prefix}{header_key}",
+                self._redact_if_sensitive(header_key, header_value),
+            )
 
     def eligible_based_on_content_type(self, headers: dict):
         '''find content-type in headers'''
diff --git a/test/instrumentation/base_wrapper_test.py b/test/instrumentation/base_wrapper_test.py
new file mode 100644
index 0000000..4a9431e
--- /dev/null
+++ b/test/instrumentation/base_wrapper_test.py
@@ -0,0 +1,68 @@
+"""Unit tests for BaseInstrumentorWrapper sensitive-header redaction.
+
+Covers the choke point (`add_headers_to_span`) shared by the HTTP
+(requests/httpx/aiohttp) and RPC (gRPC) handlers, so credential-bearing
+headers never reach span attributes verbatim.
+"""
+
+from harness_sdk.instrumentation import BaseInstrumentorWrapper
+
+
+class _FakeSpan:
+    """Minimal Span stand-in that records set_attribute calls."""
+
+    def __init__(self):
+        self.attributes = {}
+
+    def is_recording(self):
+        return True
+
+    def set_attribute(self, key, value):
+        self.attributes[key] = value
+
+
+def test_sensitive_headers_are_redacted(agent):  # noqa: ARG001 (agent inits Config)
+    wrapper = BaseInstrumentorWrapper()
+    span = _FakeSpan()
+
+    headers = {
+        "authorization": "Bearer sk-secret-openai-key",
+        "x-api-key": "sk-ant-secret-anthropic-key",
+        "cookie": "session=abc123",
+        "x-harness-service-token": "pat.acct.secret",
+        "content-type": "application/json",
+        "accept": "*/*",
+    }
+
+    wrapper.add_headers_to_span("http.request.header.", span, headers)
+
+    # Sensitive headers must be masked.
+    assert span.attributes["http.request.header.authorization"] == BaseInstrumentorWrapper.REDACTED_VALUE
+    assert span.attributes["http.request.header.x-api-key"] == BaseInstrumentorWrapper.REDACTED_VALUE
+    assert span.attributes["http.request.header.cookie"] == BaseInstrumentorWrapper.REDACTED_VALUE
+    assert span.attributes["http.request.header.x-harness-service-token"] == BaseInstrumentorWrapper.REDACTED_VALUE
+
+    # Benign headers must pass through untouched.
+    assert span.attributes["http.request.header.content-type"] == "application/json"
+    assert span.attributes["http.request.header.accept"] == "*/*"
+
+    # No raw secret value should survive anywhere on the span.
+    assert "sk-secret-openai-key" not in span.attributes.values()
+    assert "sk-ant-secret-anthropic-key" not in span.attributes.values()
+
+
+def test_redaction_is_case_insensitive(agent):  # noqa: ARG001
+    wrapper = BaseInstrumentorWrapper()
+    span = _FakeSpan()
+
+    wrapper.add_headers_to_span(
+        "http.request.header.", span, {"Authorization": "Bearer sk-secret"}
+    )
+
+    assert span.attributes["http.request.header.Authorization"] == BaseInstrumentorWrapper.REDACTED_VALUE
+
+
+def test_redact_helper_returns_value_for_benign_header(agent):  # noqa: ARG001
+    wrapper = BaseInstrumentorWrapper()
+    assert wrapper._redact_if_sensitive("accept", "*/*") == "*/*"
+    assert wrapper._redact_if_sensitive("authorization", "Bearer x") == BaseInstrumentorWrapper.REDACTED_VALUE