fix(tracing): Propagate trace headers in streaming path when no current span (HTTP clients)

ericapisani · sl0thentr0py · commit aeb7bd8e625a · 2026-07-16T13:38:16.000+02:00
Previously, when span streaming was enabled and there was no active
span, httpx/httpx2/httplib skipped trace header propagation entirely
by returning early. This diverged from the legacy behavior and dropped
distributed tracing continuity for outgoing requests made outside of
a span.

Extract the shared header-propagation logic into
`propagate_trace_headers()` in tracing_utils.py and call it from the
no-current-span early-return branches so headers are still attached
from the scope's propagation context.
diff --git a/sentry_sdk/integrations/httpx.py b/sentry_sdk/integrations/httpx.py
@@ -4,18 +4,15 @@
 from sentry_sdk.consts import OP, SPANDATA
 from sentry_sdk.integrations import DidNotEnable, Integration
 from sentry_sdk.scope import should_send_default_pii
-from sentry_sdk.tracing import BAGGAGE_HEADER_NAME
 from sentry_sdk.tracing_utils import (
     add_http_request_source,
-    add_sentry_baggage_to_headers,
     has_span_streaming_enabled,
-    should_propagate_trace,
+    propagate_trace_headers,
 )
 from sentry_sdk.utils import (
     SENSITIVE_DATA_SUBSTITUTE,
     capture_internal_exceptions,
     ensure_integration_enabled,
-    logger,
     parse_url,
 )
 
@@ -84,21 +81,7 @@ def send(self: "Client", request: "Request", **kwargs: "Any") -> "Response":
                     if parsed_url.fragment:
                         attributes["url.fragment"] = parsed_url.fragment
 
-                if should_propagate_trace(client, str(request.url)):
-                    for (
-                        key,
-                        value,
-                    ) in (
-                        sentry_sdk.get_current_scope().iter_trace_propagation_headers()
-                    ):
-                        logger.debug(
-                            f"[Tracing] Adding `{key}` header {value} to outgoing request to {request.url}."
-                        )
-
-                        if key == BAGGAGE_HEADER_NAME:
-                            add_sentry_baggage_to_headers(request.headers, value)
-                        else:
-                            request.headers[key] = value
+                propagate_trace_headers(client, request)
 
                 try:
                     rv = real_send(self, request, **kwargs)
@@ -128,21 +111,7 @@ def send(self: "Client", request: "Request", **kwargs: "Any") -> "Response":
                     span.set_data(SPANDATA.HTTP_QUERY, parsed_url.query)
                     span.set_data(SPANDATA.HTTP_FRAGMENT, parsed_url.fragment)
 
-                if should_propagate_trace(client, str(request.url)):
-                    for (
-                        key,
-                        value,
-                    ) in (
-                        sentry_sdk.get_current_scope().iter_trace_propagation_headers()
-                    ):
-                        logger.debug(
-                            f"[Tracing] Adding `{key}` header {value} to outgoing request to {request.url}."
-                        )
-
-                        if key == BAGGAGE_HEADER_NAME:
-                            add_sentry_baggage_to_headers(request.headers, value)
-                        else:
-                            request.headers[key] = value
+                propagate_trace_headers(client, request)
 
                 rv = real_send(self, request, **kwargs)
 
@@ -197,21 +166,7 @@ async def send(
                     if parsed_url.fragment:
                         attributes["url.fragment"] = parsed_url.fragment
 
-                if should_propagate_trace(client, str(request.url)):
-                    for (
-                        key,
-                        value,
-                    ) in (
-                        sentry_sdk.get_current_scope().iter_trace_propagation_headers()
-                    ):
-                        logger.debug(
-                            f"[Tracing] Adding `{key}` header {value} to outgoing request to {request.url}."
-                        )
-
-                        if key == BAGGAGE_HEADER_NAME:
-                            add_sentry_baggage_to_headers(request.headers, value)
-                        else:
-                            request.headers[key] = value
+                propagate_trace_headers(client, request)
 
                 try:
                     rv = await real_send(self, request, **kwargs)
@@ -241,20 +196,7 @@ async def send(
                     span.set_data(SPANDATA.HTTP_QUERY, parsed_url.query)
                     span.set_data(SPANDATA.HTTP_FRAGMENT, parsed_url.fragment)
 
-                if should_propagate_trace(client, str(request.url)):
-                    for (
-                        key,
-                        value,
-                    ) in (
-                        sentry_sdk.get_current_scope().iter_trace_propagation_headers()
-                    ):
-                        logger.debug(
-                            f"[Tracing] Adding `{key}` header {value} to outgoing request to {request.url}."
-                        )
-                        if key == BAGGAGE_HEADER_NAME:
-                            add_sentry_baggage_to_headers(request.headers, value)
-                        else:
-                            request.headers[key] = value
+                propagate_trace_headers(client, request)
 
                 rv = await real_send(self, request, **kwargs)
 
diff --git a/sentry_sdk/integrations/httpx2.py b/sentry_sdk/integrations/httpx2.py
@@ -4,18 +4,15 @@
 from sentry_sdk.consts import OP, SPANDATA
 from sentry_sdk.integrations import DidNotEnable, Integration
 from sentry_sdk.scope import should_send_default_pii
-from sentry_sdk.tracing import BAGGAGE_HEADER_NAME
 from sentry_sdk.tracing_utils import (
     add_http_request_source,
-    add_sentry_baggage_to_headers,
     has_span_streaming_enabled,
-    should_propagate_trace,
+    propagate_trace_headers,
 )
 from sentry_sdk.utils import (
     SENSITIVE_DATA_SUBSTITUTE,
     capture_internal_exceptions,
     ensure_integration_enabled,
-    logger,
     parse_url,
 )
 
@@ -61,6 +58,8 @@ def send(self: "Client", request: "Request", **kwargs: "Any") -> "Response":
 
         if is_span_streaming_enabled:
             if sentry_sdk.traces.get_current_span() is None:
+                propagate_trace_headers(client, request)
+
                 return real_send(self, request, **kwargs)
 
             with sentry_sdk.traces.start_span(
@@ -84,21 +83,7 @@ def send(self: "Client", request: "Request", **kwargs: "Any") -> "Response":
                     if parsed_url.fragment:
                         attributes["url.fragment"] = parsed_url.fragment
 
-                if should_propagate_trace(client, str(request.url)):
-                    for (
-                        key,
-                        value,
-                    ) in (
-                        sentry_sdk.get_current_scope().iter_trace_propagation_headers()
-                    ):
-                        logger.debug(
-                            f"[Tracing] Adding `{key}` header {value} to outgoing request to {request.url}."
-                        )
-
-                        if key == BAGGAGE_HEADER_NAME:
-                            add_sentry_baggage_to_headers(request.headers, value)
-                        else:
-                            request.headers[key] = value
+                propagate_trace_headers(client, request)
 
                 try:
                     rv = real_send(self, request, **kwargs)
@@ -128,21 +113,7 @@ def send(self: "Client", request: "Request", **kwargs: "Any") -> "Response":
                     span.set_data(SPANDATA.HTTP_QUERY, parsed_url.query)
                     span.set_data(SPANDATA.HTTP_FRAGMENT, parsed_url.fragment)
 
-                if should_propagate_trace(client, str(request.url)):
-                    for (
-                        key,
-                        value,
-                    ) in (
-                        sentry_sdk.get_current_scope().iter_trace_propagation_headers()
-                    ):
-                        logger.debug(
-                            f"[Tracing] Adding `{key}` header {value} to outgoing request to {request.url}."
-                        )
-
-                        if key == BAGGAGE_HEADER_NAME:
-                            add_sentry_baggage_to_headers(request.headers, value)
-                        else:
-                            request.headers[key] = value
+                propagate_trace_headers(client, request)
 
                 rv = real_send(self, request, **kwargs)
 
@@ -174,6 +145,8 @@ async def send(
 
         if is_span_streaming_enabled:
             if sentry_sdk.traces.get_current_span() is None:
+                propagate_trace_headers(client, request)
+
                 return await real_send(self, request, **kwargs)
 
             with sentry_sdk.traces.start_span(
@@ -197,21 +170,7 @@ async def send(
                     if parsed_url.fragment:
                         attributes["url.fragment"] = parsed_url.fragment
 
-                if should_propagate_trace(client, str(request.url)):
-                    for (
-                        key,
-                        value,
-                    ) in (
-                        sentry_sdk.get_current_scope().iter_trace_propagation_headers()
-                    ):
-                        logger.debug(
-                            f"[Tracing] Adding `{key}` header {value} to outgoing request to {request.url}."
-                        )
-
-                        if key == BAGGAGE_HEADER_NAME:
-                            add_sentry_baggage_to_headers(request.headers, value)
-                        else:
-                            request.headers[key] = value
+                propagate_trace_headers(client, request)
 
                 try:
                     rv = await real_send(self, request, **kwargs)
@@ -241,20 +200,7 @@ async def send(
                     span.set_data(SPANDATA.HTTP_QUERY, parsed_url.query)
                     span.set_data(SPANDATA.HTTP_FRAGMENT, parsed_url.fragment)
 
-                if should_propagate_trace(client, str(request.url)):
-                    for (
-                        key,
-                        value,
-                    ) in (
-                        sentry_sdk.get_current_scope().iter_trace_propagation_headers()
-                    ):
-                        logger.debug(
-                            f"[Tracing] Adding `{key}` header {value} to outgoing request to {request.url}."
-                        )
-                        if key == BAGGAGE_HEADER_NAME:
-                            add_sentry_baggage_to_headers(request.headers, value)
-                        else:
-                            request.headers[key] = value
+                propagate_trace_headers(client, request)
 
                 rv = await real_send(self, request, **kwargs)
 
diff --git a/sentry_sdk/integrations/stdlib.py b/sentry_sdk/integrations/stdlib.py
@@ -112,28 +112,30 @@ def putrequest(
             parsed_url = parse_url(real_url, sanitize=False)
 
         span_streaming = has_span_streaming_enabled(client.options)
-        span: "Union[Span, StreamedSpan]"
+        span: "Union[Span, StreamedSpan, None]"
         if span_streaming:
             if sentry_sdk.traces.get_current_span() is None:
-                return real_putrequest(self, method, url, *args, **kwargs)
-
-            span = sentry_sdk.traces.start_span(
-                name="%s %s"
-                % (method, parsed_url.url if parsed_url else SENSITIVE_DATA_SUBSTITUTE),
-                attributes={
-                    "sentry.origin": "auto.http.stdlib.httplib",
-                    "sentry.op": OP.HTTP_CLIENT,
-                    SPANDATA.HTTP_REQUEST_METHOD: method,
-                },
-            )
-
-            if parsed_url is not None and should_send_default_pii():
-                span.set_attribute(SPANDATA.URL_FRAGMENT, parsed_url.fragment)
-                span.set_attribute(SPANDATA.URL_FULL, parsed_url.url)
-                span.set_attribute(SPANDATA.URL_QUERY, parsed_url.query)
+                span = None
+            else:
+                span = sentry_sdk.traces.start_span(
+                    name="%s %s"
+                    % (
+                        method,
+                        parsed_url.url if parsed_url else SENSITIVE_DATA_SUBSTITUTE,
+                    ),
+                    attributes={
+                        "sentry.origin": "auto.http.stdlib.httplib",
+                        "sentry.op": OP.HTTP_CLIENT,
+                        SPANDATA.HTTP_REQUEST_METHOD: method,
+                    },
+                )
 
-            set_on_span = span.set_attribute
+                if parsed_url is not None and should_send_default_pii():
+                    span.set_attribute(SPANDATA.URL_FRAGMENT, parsed_url.fragment)
+                    span.set_attribute(SPANDATA.URL_FULL, parsed_url.url)
+                    span.set_attribute(SPANDATA.URL_QUERY, parsed_url.query)
 
+                set_on_span = span.set_attribute
         else:
             span = sentry_sdk.start_span(
                 op=OP.HTTP_CLIENT,
@@ -151,7 +153,7 @@ def putrequest(
             set_on_span = span.set_data
 
         # for proxies, these point to the proxy host/port
-        if tunnel_host:
+        if span and tunnel_host:
             set_on_span(SPANDATA.NETWORK_PEER_ADDRESS, self.host)
             set_on_span(SPANDATA.NETWORK_PEER_PORT, self.port)
 
diff --git a/sentry_sdk/tracing_utils.py b/sentry_sdk/tracing_utils.py
@@ -973,6 +973,31 @@ def should_propagate_trace(client: "sentry_sdk.client.BaseClient", url: str) ->
     return match_regex_list(url, trace_propagation_targets, substring_matching=True)
 
 
+def propagate_trace_headers(
+    client: "sentry_sdk.client.BaseClient", request: "Any"
+) -> None:
+    """
+    Attach Sentry trace propagation headers (``sentry-trace``/``baggage``) from the
+    current scope's propagation context to an outgoing request, if the request's
+    URL matches the configured ``trace_propagation_targets``.
+
+    ``request`` is expected to expose ``url`` and a mutable ``headers`` mapping
+    (e.g. an ``httpx``/``httpx2`` ``Request``).
+    """
+    if not should_propagate_trace(client, str(request.url)):
+        return
+
+    for key, value in sentry_sdk.get_current_scope().iter_trace_propagation_headers():
+        logger.debug(
+            f"[Tracing] Adding `{key}` header {value} to outgoing request to {request.url}."
+        )
+
+        if key == BAGGAGE_HEADER_NAME:
+            add_sentry_baggage_to_headers(request.headers, value)
+        else:
+            request.headers[key] = value
+
+
 def normalize_incoming_data(incoming_data: "Dict[str, Any]") -> "Dict[str, Any]":
     """
     Normalizes incoming data so the keys are all lowercase with dashes instead of underscores and stripped from known prefixes.
diff --git a/tests/integrations/httpx2/test_httpx2.py b/tests/integrations/httpx2/test_httpx2.py
diff --git a/tests/integrations/stdlib/test_httplib.py b/tests/integrations/stdlib/test_httplib.py
