fix: align feature flag flush configuration and trim docs

Use the shared DD_FEATURE_FLAGS_ prefix for the timeout setting and remove PR-specific README and smoke-runbook text.

Environment: Datadog workspace

Co-Authored-By: Codex GPT-6 <noreply@localhost>

Author: vjfridge

README.md

@@ -76,27 +76,3 @@ Unless explicitly stated otherwise all files in this repository are licensed und
 This product includes software developed at Datadog (https://www.datadoghq.com/). Copyright 2019 Datadog, Inc.
 
 [1]: https://www.datadoghq.com/blog/troubleshoot-lambda-function-request-response-payloads/
-
-## Feature flag telemetry at invocation end
-
-With a tracer and Lambda layer that support automatic feature flag flushing,
-the wrapper attempts to send pending evaluation and exposure events before
-returning a response or rethrowing a handler exception. No additional handler
-code or provider shutdown is required; providers and polling remain available
-for warm invocations.
-
-`DD_FEATURE_FLAG_FLUSH_TIMEOUT_MS` sets the maximum added wait in milliseconds
-(default: `500`; `0` disables waiting). The actual budget is the smaller of that
-cap and the invocation's remaining time minus a 100 ms safety margin. The wrapper
-skips waiting when that budget is exhausted or unavailable. Incomplete flushes
-are reported in debug logs without changing the handler's result.
-
-Delivery is best effort. A timeout stops waiting but does not cancel or retry
-in-flight requests; they may complete after a warm thaw. Abrupt termination can
-still lose buffered events. Endpoint acceptance does not guarantee immediate
-visibility in the UI. Older tracers safely skip the integration.
-
-Release status: this capability requires the tracer's internal flush contract
-version 1. The first supported tracer/library/layer combination is pending
-coordinated release and deployed validation; an older published layer does not
-provide this behavior merely by setting the timeout variable.

datadog_lambda/config.py

@@ -86,7 +86,7 @@ def _resolve_env(self, key, default=None, cast=None, depends_on_tracing=False):
 
     flush_in_thread = _get_env("DD_FLUSH_IN_THREAD", "false", as_bool)
     feature_flag_flush_timeout_ms = _get_env(
-        "DD_FEATURE_FLAG_FLUSH_TIMEOUT_MS", 500.0, float
+        "DD_FEATURE_FLAGS_FLUSH_TIMEOUT_MS", 500.0, float
     )
     flush_to_log = _get_env("DD_FLUSH_TO_LOG", "false", as_bool)
     logs_injection = _get_env("DD_LOGS_INJECTION", "true", as_bool)

tests/integration/FEATURE_FLAG_FLUSH.md

@@ -72,9 +72,9 @@ def test_timeout_environment_parsing_preserves_flush(self):
                 feature_flags, "config", Config()
             ), patch.object(feature_flags, "_telemetry") as telemetry:
                 if value is None:
-                    os.environ.pop("DD_FEATURE_FLAG_FLUSH_TIMEOUT_MS", None)
+                    os.environ.pop("DD_FEATURE_FLAGS_FLUSH_TIMEOUT_MS", None)
                 else:
-                    os.environ["DD_FEATURE_FLAG_FLUSH_TIMEOUT_MS"] = value
+                    os.environ["DD_FEATURE_FLAGS_FLUSH_TIMEOUT_MS"] = value
                 telemetry.FLUSH_API_VERSION = 1
                 telemetry.flush.return_value = "completed"
                 feature_flags.flush_feature_flag_telemetry(