fix(remote-config): support restored Node.js capability bits

tests/parametric/capabilities.yml

@@ -70,8 +70,10 @@ capabilities:
       - ASM_AUTO_USER_INSTRUM_MODE
 
     # SDK_CONFIGURATION supersedes the per-setting APM_TRACING capabilities in the 5.x
-    # line from 5.128.0 and in the 6.x line from 6.17.0.
-    '<5.128.0 || >=6.0.0-0 <6.17.0':
+    # line from 5.128.0 and in the 6.x line from 6.17.0. Node.js 6.19.0 restores the
+    # legacy bits as compatibility metadata while continuing to consume sdk_config. Keep the
+    # restored-bit range below 7.0.0 so this can land before the change reaches Node.js main.
+    '<5.128.0 || >=6.0.0-0 <6.17.0 || >=6.19.0 <7.0.0-0':
       - APM_TRACING_CUSTOM_TAGS
       - APM_TRACING_ENABLED
       - APM_TRACING_HTTP_HEADER_TAGS
@@ -88,11 +90,11 @@ capabilities:
     '>=5.83.0':
       - APM_TRACING_MULTICONFIG
 
-    '>=5.83.0 <5.128.0 || >=6.0.0-0 <6.17.0':
+    '>=5.83.0 <5.128.0 || >=6.0.0-0 <6.17.0 || >=6.19.0 <7.0.0-0':
       - APM_TRACING_ENABLE_CODE_ORIGIN
       - APM_TRACING_ENABLE_DYNAMIC_INSTRUMENTATION
 
-    '>=5.84.0 <5.128.0 || >=6.0.0-0 <6.17.0':
+    '>=5.84.0 <5.128.0 || >=6.0.0-0 <6.17.0 || >=6.19.0 <7.0.0-0':
       - APM_TRACING_ENABLE_LIVE_DEBUGGING
 
   python:

tests/parametric/test_dynamic_configuration.py

@@ -193,10 +193,10 @@ def uses_sdk_configuration(test_agent: TestAgentAPI) -> bool:
 def assert_rc_capability(test_agent: TestAgentAPI, capability: Capabilities, wait_loops: int = 100) -> None:
     """Assert that the tracer advertises the capability to remotely configure one setting.
 
-    A tracer that has moved to the unified SDK_CONFIGURATION contract advertises that single bit
-    for every remotely configurable setting instead of the per-setting ones, so it stands in for
-    any of them. The SDK_CONFIGURATION bit on its own does not, since libdatadog gives that bit a
-    different meaning; only a tracer that has really dropped the per-setting bits qualifies.
+    A tracer that has moved to the unified SDK_CONFIGURATION contract can use that bit for every
+    remotely configurable setting, so it stands in for any missing per-setting one. The
+    SDK_CONFIGURATION bit on its own does not, since libdatadog gives that bit a different meaning;
+    only a tracer whose capability combination identifies the unified contract qualifies.
     """
     seen_capabilities = test_agent.wait_for_rc_capabilities(wait_loops)
     if capability in seen_capabilities:
@@ -581,10 +581,10 @@ def test_tracing_client_tracing_disable_one_way(
 class Test_DynamicConfigSdkConfiguration:
     """Coverage for the generic sdk_config RC delivery path.
 
-    sdk_config carries settings as generic env-var-keyed entries, applied via the single
-    SDK_CONFIGURATION capability instead of custom per-setting parsing. These tests confirm a
-    tracer that declares SDK_CONFIGURATION consumes sdk_config with no regression in behavior
-    compared to the equivalent lib_config delivery, starting with DD_TRACE_ENABLED.
+    sdk_config carries settings as generic env-var-keyed entries, applied via the unified
+    SDK_CONFIGURATION contract instead of custom per-setting parsing. These tests confirm a tracer
+    on that contract consumes sdk_config with no regression in behavior compared to the equivalent
+    lib_config delivery, starting with DD_TRACE_ENABLED.
 
     test_sdk_config_tracing_enabled_matches_lib_config asserts real behavior (tracing actually
     stops) for DD_TRACE_ENABLED. test_sdk_config_field_is_applied then layers a shallower

tests/test_the_test/test_remote_config.py

@@ -196,9 +196,10 @@ def test_resolve_sdk_configuration_contract():
     """The SDK_CONFIGURATION bit alone does not mean the library reads sdk_config.
 
     Bit 49 is SDK_CONFIGURATION in the remote config source of truth, but libdatadog gives the
-    same bit to ASM_RAW_RESPONSE_BODY, so the per-setting capabilities have to be gone too.
+    same bit to ASM_RAW_RESPONSE_BODY. Capability interpretation therefore also needs to account
+    for the tracer implementation when legacy bits and SDK_CONFIGURATION appear together.
     """
-    # dd-trace-js with the SDK_CONFIGURATION support: the per-setting capabilities are dropped
+    # dd-trace-js 6.17.0 and 6.18.0: the per-setting capabilities are dropped
     assert rc.resolve_sdk_configuration_contract(
         {
             Capabilities.ASM_ACTIVATION,
@@ -207,21 +208,34 @@ def test_resolve_sdk_configuration_contract():
         }
     )
 
-    # dd-trace-php: bit 49 is ASM_RAW_RESPONSE_BODY there, and lib_config is still what it reads
+    core_lib_config_capabilities = {
+        Capabilities.APM_TRACING_CUSTOM_TAGS,
+        Capabilities.APM_TRACING_ENABLED,
+        Capabilities.APM_TRACING_HTTP_HEADER_TAGS,
+        Capabilities.APM_TRACING_LOGS_INJECTION,
+        Capabilities.APM_TRACING_SAMPLE_RATE,
+        Capabilities.APM_TRACING_SAMPLE_RULES,
+    }
+
+    # dd-trace-php: bit 49 is ASM_RAW_RESPONSE_BODY there, and the per-setting fingerprint confirms
+    # that lib_config is still what it reads.
+    php_lib_config_capabilities = core_lib_config_capabilities | {
+        Capabilities.APM_TRACING_MULTICONFIG,
+        Capabilities.SDK_CONFIGURATION,
+    }
+    assert rc.resolve_sdk_configuration_contract(php_lib_config_capabilities, library_name="php") is False
+
+    # dd-trace-js 6.19.0+: all nine restored per-setting bits are compatibility metadata, but
+    # sdk_config remains the only application path.
+    nodejs_sdk_config_with_legacy_capabilities = core_lib_config_capabilities | {
+        Capabilities.APM_TRACING_MULTICONFIG,
+        Capabilities.APM_TRACING_ENABLE_CODE_ORIGIN,
+        Capabilities.APM_TRACING_ENABLE_DYNAMIC_INSTRUMENTATION,
+        Capabilities.APM_TRACING_ENABLE_LIVE_DEBUGGING,
+        Capabilities.SDK_CONFIGURATION,
+    }
     assert (
-        rc.resolve_sdk_configuration_contract(
-            {
-                Capabilities.APM_TRACING_CUSTOM_TAGS,
-                Capabilities.APM_TRACING_ENABLED,
-                Capabilities.APM_TRACING_HTTP_HEADER_TAGS,
-                Capabilities.APM_TRACING_LOGS_INJECTION,
-                Capabilities.APM_TRACING_SAMPLE_RATE,
-                Capabilities.APM_TRACING_SAMPLE_RULES,
-                Capabilities.APM_TRACING_MULTICONFIG,
-                Capabilities.SDK_CONFIGURATION,
-            }
-        )
-        is False
+        rc.resolve_sdk_configuration_contract(nodejs_sdk_config_with_legacy_capabilities, library_name="nodejs") is True
     )
 
     # dd-trace-java: no SDK_CONFIGURATION at all
@@ -265,5 +279,5 @@ def test_apm_tracing_capabilities_exclude_sdk_configuration():
     `resolve_sdk_configuration_contract`.
     """
     assert Capabilities.SDK_CONFIGURATION not in rc.APM_TRACING_CAPABILITIES
-    assert rc.LEGACY_APM_TRACING_CAPABILITIES <= rc.APM_TRACING_CAPABILITIES
+    assert rc.LIB_CONFIG_CAPABILITY_FINGERPRINT <= rc.APM_TRACING_CAPABILITIES
     assert Capabilities.APM_TRACING_MULTICONFIG in rc.APM_TRACING_CAPABILITIES

utils/_remote_config.py

@@ -645,9 +645,11 @@ def to_sdk_config_payload(config: dict[str, Any]) -> dict[str, Any]:
     capability for capability in Capabilities if capability.name.startswith("APM_TRACING_")
 )
 
-# The per-setting APM_TRACING capabilities that SDK_CONFIGURATION replaces. A library on the new
-# contract advertises the single SDK_CONFIGURATION bit instead of all of these.
-LEGACY_APM_TRACING_CAPABILITIES = frozenset(
+# The per-setting capability fingerprint observed on libraries that consume `lib_config`. This is
+# deliberately not an exhaustive set of legacy APM_TRACING capabilities: optional feature bits do
+# not reliably identify the payload contract. Node.js 6.19.0+ re-advertises this fingerprint for
+# backend/frontend compatibility while continuing to consume `sdk_config`.
+LIB_CONFIG_CAPABILITY_FINGERPRINT = frozenset(
     {
         Capabilities.APM_TRACING_CUSTOM_TAGS,
         Capabilities.APM_TRACING_ENABLED,
@@ -659,7 +661,9 @@ def to_sdk_config_payload(config: dict[str, Any]) -> dict[str, Any]:
 )
 
 
-def resolve_sdk_configuration_contract(capabilities: set[Capabilities]) -> bool | None:
+def resolve_sdk_configuration_contract(
+    capabilities: set[Capabilities], *, library_name: str | None = None
+) -> bool | None:
     """Decide which APM_TRACING payload shape a set of advertised capabilities asks for.
 
     Returns True for `sdk_config`, False for `lib_config`, and None when the capabilities seen so
@@ -670,16 +674,23 @@ def resolve_sdk_configuration_contract(capabilities: set[Capabilities]) -> bool
     libdatadog hands the same bit to `ASM_RAW_RESPONSE_BODY`, so a libdatadog-based library such as
     dd-trace-php advertises it while still reading `lib_config`.
 
-    Dropping the per-setting capabilities is the whole point of the unified bit, so their absence
-    is what distinguishes the two. Absence only counts once the library has actually registered its
-    APM_TRACING remote config, though: capabilities are added as products start, and AppSec ones
-    come first, so an early poll from a libdatadog library shows bit 49 with no APM_TRACING bit yet
-    and would otherwise be mistaken for the unified contract.
+    For Node.js, SDK_CONFIGURATION is authoritative even when the legacy per-setting bits are also
+    present. Node.js 6.19.0 restored those bits for backend/frontend compatibility without restoring
+    the legacy `lib_config` application path.
+
+    For other tracers, the per-setting fingerprint distinguishes the two contracts. Its absence
+    only counts once the library has actually registered its APM_TRACING remote config, though:
+    capabilities are added as products start, and AppSec ones come first, so an early poll from a
+    libdatadog library shows bit 49 with no APM_TRACING bit yet and would otherwise be mistaken for
+    the unified contract.
     """
     if not capabilities & APM_TRACING_CAPABILITIES:
         return None
 
-    if capabilities & LEGACY_APM_TRACING_CAPABILITIES:
+    if library_name == "nodejs" and Capabilities.SDK_CONFIGURATION in capabilities:
+        return True
+
+    if capabilities & LIB_CONFIG_CAPABILITY_FINGERPRINT:
         return False
 
     return Capabilities.SDK_CONFIGURATION in capabilities
@@ -711,7 +722,7 @@ def resolve_sdk_configuration_support(get_capabilities: Callable[[], set[Capabil
         logger.error(f"Could not read the RC capabilities ({e}), assuming no SDK_CONFIGURATION support")
         return False
 
-    supported = resolve_sdk_configuration_contract(capabilities)
+    supported = resolve_sdk_configuration_contract(capabilities, library_name=context.library.name)
     if supported is None:
         logger.info("No APM_TRACING capability advertised yet, sending lib_config for now")
         return False