.. _version_history_1.39.0:

1.39.0 (Pending)
=================





Minor behavior changes
----------------------

*Changes that may cause incompatibilities for some users, but should not for most*



* **golang**: Reduced the per-cgo-call mutex acquisition on the Golang HTTP filter by making the
  ``has_destroyed_`` flag a ``std::atomic<bool>``. CAPI methods whose only Envoy-side work is
  Filter-owned or runs on the worker thread (``setHeader``, ``removeHeader``, ``setTrailer``,
  ``removeTrailer``, ``addData``, ``injectData``, ``continueStatus``, ``sendLocalReply``,
  ``setBufferHelper``, ``copyBuffer``, ``drainBuffer``, ``setUpstreamOverrideHost``,
  ``clearRouteCache``, ``setDynamicMetadata``, ``setStringFilterState``) no longer take the
  mutex, eliminating an uncontended atomic compare-and-swap pair on every such call. The
  mutex is retained on the CAPI methods that inline-dereference Envoy-stream-owned objects
  from off-thread (``getHeader``, ``copyHeaders``, ``copyTrailers``, ``getIntegerValue``,
  ``setDrainConnectionUponCompletion``) where it serialises against ``onDestroy`` to prevent
  the worker thread from freeing the underlying header map or ``StreamInfo`` mid-access, and
  on the five methods that write to the per-request ``strValue`` scratch buffer
  (``getStringValue``, ``getDynamicMetadata``, ``getStringFilterState``, ``getStringProperty``,
  ``getSecret``).
* **router**: The upstream transport failure reason (e.g. TLS certificate validation errors) is no longer included
  in the HTTP response body sent to downstream clients. It remains available in access logs via
  ``%UPSTREAM_TRANSPORT_FAILURE_REASON%``. This behavioral change can be temporarily reverted by setting
  runtime guard ``envoy.reloadable_features.hide_transport_failure_reason_in_response_body`` to ``false``.
  This is being changed because in many cases the upstream failure details are inappropriate to send to
  the downstream client as it discloses too many internal details.
* **stats**: Optimized prometheus stats endpoint. Users should see a roughly 30-40% latency improvement in calls to the endpoint
  for cases where the scrape results in lots of cluster stats.
  There should be no visible changes to users, or incompatibilities.



Bug fixes
---------

*Changes expected to improve the state of the world and are unlikely to have negative effects*



* **build**: Fixed ``Illegal ambiguous match`` error when building contrib targets with ``--config=aws-lc-fips``
  on aarch64 by restricting the ``using_aws_lc`` branch of ``SELECTED_CONTRIB_EXTENSIONS`` to
  ``linux_x86_64``. Mirrors the approach taken by #32382 for ``boringssl_fips``.
* **dynamic_modules**: Fixed a bug where the HTTP filter per-route configuration and the upstream HTTP TCP bridge
  configuration did not handle the ``google.protobuf.Struct`` configuration message as the API
  definition requires. Both factories now serialize the ``Struct`` to a JSON string and pass the
  string to the dynamic module side as the configuration, matching the behavior already in place
  for every other dynamic module extension factory.
* **dynamic_modules**: Fixed a crashing bug in the HTTP filter when a stream was already above the downstream write-buffer
  high watermark at filter-chain construction time. Downstream watermark callback registration is
  now deferred until the in-module filter has been constructed.
* **load_report**: Fixed a bug in load stats reporting where reports were dropped if only custom metrics or completed
  requests were present in a reporting interval. This behavioral change can be reverted by setting
  the runtime guard ``envoy.reloadable_features.report_load_for_non_zero_stats`` to ``false``.
* **oauth2**: Fixed a crash in the OAuth2 filter where AES-CBC decryption of token cookies could spuriously
  succeed (~1/256) when the configured HMAC secret did not match the secret used to encrypt the
  cookie (for example after secret rotation, or when receiving legacy unencrypted tokens). The
  resulting binary "plaintext" was written back into the ``Cookie:`` request header and tripped a
  ``HeaderString`` validation assert. Such plaintexts are now rejected and the original cookie value
  is preserved, matching the behavior already documented for the explicit decryption-failure case.




New features
------------


* **access_log**: Added ``%UPSTREAM_SERVER_NAME%`` access log formatter returning the SNI from the established upstream
  TLS connection.
* **access_log**: Supported the singleton stats scope in the :ref:`stats access logger <envoy_v3_api_msg_extensions.access_loggers.stats.v3.Config>`.
* **attributes**: Added ``upstream.server_name`` CEL attribute returning the SNI from the established upstream
  TLS connection.
* **composite**: Added support for the
  :ref:`inline matcher <envoy_v3_api_field_extensions.filters.http.composite.v3.Composite.matcher>`
  in the composite HTTP filter. Now users could specify the matcher inline in the filter configuration
  instead of using the :ref:`ExtensionWithMatcher
  <envoy_v3_api_msg_extensions.common.matching.v3.ExtensionWithMatcher>` filter.
* **dynamic_modules**: Added ``envoy_dynamic_module_callback_is_validation_mode`` ABI callback that allows dynamic
  modules to check if the server is running in config validation mode.
* **jwt_authn**: Added :ref:`verification_status_header
  <envoy_v3_api_field_extensions.filters.http.jwt_authn.v3.ExtractOnlyWithoutValidation.verification_status_header>`
  to the ``ExtractOnlyWithoutValidation`` requirement. When a JWT is present in the request but fails
  signature verification, the named request header (default ``x-jwt-signature-verified``) is set to
  ``false`` so downstream filters (RBAC, ext_authz) can distinguish forwarded-but-unverified claims
  from validated ones. The header is not set on a successfully verified JWT or when no JWT is present.
  This behavior can be reverted by setting the runtime guard
  ``envoy.reloadable_features.jwt_authn_add_verification_status_header`` to ``false``.
* **logging**: Added ``%N`` as a custom spdlog pattern flag that emits the Envoy version string. It can be
  used in the ``--log-format`` CLI flag or the bootstrap ``application_log_config.log_format``
  to include the running version in every log line, e.g. ``--log-format "[%N][%l] %v"``.
* **mysql_proxy**: Added SSL termination support to the MySQL proxy filter with RSA-mediated ``caching_sha2_password``
  authentication. The filter can now terminate downstream TLS connections using the
  :ref:`starttls transport socket <envoy_v3_api_msg_extensions.transport_sockets.starttls.v3.StartTlsConfig>`
  and transparently mediate MySQL 8.0+ ``caching_sha2_password`` full authentication by performing
  RSA public key exchange on behalf of the client. Added a new
  :ref:`downstream_ssl <envoy_v3_api_field_extensions.filters.network.mysql_proxy.v3.MySQLProxy.downstream_ssl>`
  config option with ``DISABLE``, ``REQUIRE``, and ``ALLOW`` modes.
* **quic**: Added support for TLS session ticket resumption in QUIC using configured session ticket keys from
  :ref:`session_ticket_keys <envoy_v3_api_field_extensions.transport_sockets.tls.v3.DownstreamTlsContext.session_ticket_keys>`.
  This enables faster reconnection across server instances by allowing clients to resume TLS sessions
  without full handshakes. The feature is disabled by default and can be enabled by setting runtime guard
  ``envoy.reloadable_features.quic_session_ticket_support`` to ``true``.
* **resource_monitors**: Overload manager fixed heap resource monitor now supports :ref:`max_heap_size_bytes_runtime
  <envoy_v3_api_field_extensions.resource_monitors.fixed_heap.v3.FixedHeapConfig.max_heap_size_bytes_runtime>`
  for runtime-overridable max heap size (e.g. RTDS or ``/runtime_modify``).
* **set_metadata_filter**: Added :ref:`per-route configuration support <envoy_v3_api_msg_extensions.filters.http.set_metadata.v3.Config>`
  to the ``set_metadata`` HTTP filter.
* **stat_sinks**: Added :ref:`max_data_points_per_request
  <envoy_v3_api_field_extensions.stat_sinks.open_telemetry.v3.SinkConfig.max_data_points_per_request>`
  configuration to the OpenTelemetry stat sink to chunk metric export requests.
* **stat_sinks**: Added a new :ref:`WASM stats filter <config_stat_sinks_wasm_filter>` contrib extension
  (``envoy.stat_sinks.wasm_filter``) that acts as programmable middleware between
  the metrics snapshot and any inner stats sink. A user-supplied WASM plugin can:
  filter metrics by index, inject global tags from node metadata
  (``stats_filter_set_global_tags``), rename metrics (``stats_filter_set_name_overrides``),
  inject synthetic counters/gauges (``stats_filter_inject_metrics``), and filter
  histograms (``stats_filter_get_histograms``). This enables moving centralized
  metric processing logic (tag enrichment, name rewriting, custom metric injection)
  into the proxy itself. Configured via
  :ref:`WasmFilterStatsSinkConfig <envoy_v3_api_msg_extensions.stat_sinks.wasm_filter.v3.WasmFilterStatsSinkConfig>`.
* **tls**: Added substitution commands ``%DOWNSTREAM_TLS_GROUP%`` and ``%UPSTREAM_TLS_GROUP%``. The TLS group may be used
  to discern if a TLS connection used a post quantum safe key exchange (e.g. X25519MLKEM768).