From c017b015f33ed28ed5d9842eea28f16f757ed6da Mon Sep 17 00:00:00 2001
From: Ivana Kellyer <ivana.kellyer@sentry.io>
Date: Wed, 13 Nov 2024 10:09:21 +0100
Subject: [PATCH 01/12] Sample on root span level

---
 MIGRATION_GUIDE.md                            |  1 +
 .../integrations/opentelemetry/sampler.py     | 21 ++++++++++++-------
 2 files changed, 15 insertions(+), 7 deletions(-)

diff --git a/MIGRATION_GUIDE.md b/MIGRATION_GUIDE.md
index 0095cafab7..052f4df0ba 100644
--- a/MIGRATION_GUIDE.md
+++ b/MIGRATION_GUIDE.md
@@ -11,6 +11,7 @@ Looking to upgrade from Sentry SDK 2.x to 3.x? Here's a comprehensive list of wh
 - The SDK now supports Python 3.7 and higher.
 - `sentry_sdk.start_span` now only takes keyword arguments.
 - `sentry_sdk.start_span` no longer takes an explicit `span` argument.
+- The `sampled` argument of `sentry_sdk.start_span` is only taken into account for root spans (previously known as transactions).
 - The `Span()` constructor does not accept a `hub` parameter anymore.
 - `Span.finish()` does not accept a `hub` parameter anymore.
 - The `Profile()` constructor does not accept a `hub` parameter anymore.
diff --git a/sentry_sdk/integrations/opentelemetry/sampler.py b/sentry_sdk/integrations/opentelemetry/sampler.py
index 79e2ec7d8f..1b097950df 100644
--- a/sentry_sdk/integrations/opentelemetry/sampler.py
+++ b/sentry_sdk/integrations/opentelemetry/sampler.py
@@ -120,20 +120,28 @@ def should_sample(
         if not has_tracing_enabled(client.options):
             return dropped_result(parent_span_context, attributes)
 
+        has_parent = parent_span_context.is_valid
+        is_root_span = not has_parent or parent_span_context.is_remote
+
         # Explicit sampled value provided at start_span
         if attributes.get(SentrySpanAttribute.CUSTOM_SAMPLED) is not None:
-            sample_rate = float(attributes[SentrySpanAttribute.CUSTOM_SAMPLED])
-            if sample_rate > 0:
-                return sampled_result(parent_span_context, attributes, sample_rate)
+            if is_root_span:
+                sample_rate = float(attributes[SentrySpanAttribute.CUSTOM_SAMPLED])
+                if sample_rate > 0:
+                    return sampled_result(parent_span_context, attributes, sample_rate)
+                else:
+                    return dropped_result(parent_span_context, attributes)
             else:
-                return dropped_result(parent_span_context, attributes)
+                logger.debug(
+                    f"[Tracing] Ignoring sampled param for non-root span {name}"
+                )
 
         sample_rate = None
 
         # Check if there is a traces_sampler
         # Traces_sampler is responsible to check parent sampled to have full transactions.
         has_traces_sampler = callable(client.options.get("traces_sampler"))
-        if has_traces_sampler:
+        if is_root_span and has_traces_sampler:
             sampling_context = {
                 "transaction_context": {
                     "name": name,
@@ -161,8 +169,7 @@ def should_sample(
             return dropped_result(parent_span_context, attributes)
 
         # Down-sample in case of back pressure monitor says so
-        # TODO: this should only be done for transactions (aka root spans)
-        if client.monitor:
+        if is_root_span and client.monitor:
             sample_rate /= 2**client.monitor.downsample_factor
 
         # Roll the dice on sample rate

From b47bc70b814f078b870ccc8c3fc4f7809e6473e7 Mon Sep 17 00:00:00 2001
From: Ivana Kellyer <ivana.kellyer@sentry.io>
Date: Wed, 13 Nov 2024 10:11:05 +0100
Subject: [PATCH 02/12] note

---
 sentry_sdk/integrations/opentelemetry/sampler.py | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/sentry_sdk/integrations/opentelemetry/sampler.py b/sentry_sdk/integrations/opentelemetry/sampler.py
index 1b097950df..74a09d5056 100644
--- a/sentry_sdk/integrations/opentelemetry/sampler.py
+++ b/sentry_sdk/integrations/opentelemetry/sampler.py
@@ -120,8 +120,8 @@ def should_sample(
         if not has_tracing_enabled(client.options):
             return dropped_result(parent_span_context, attributes)
 
-        has_parent = parent_span_context.is_valid
-        is_root_span = not has_parent or parent_span_context.is_remote
+        # parent_span_context.is_valid means this span has a parent, remote or local
+        is_root_span = not parent_span_context.is_valid or parent_span_context.is_remote
 
         # Explicit sampled value provided at start_span
         if attributes.get(SentrySpanAttribute.CUSTOM_SAMPLED) is not None:

From 1d77484ea093b080bd13a72d5f533b0d6da11ec6 Mon Sep 17 00:00:00 2001
From: Ivana Kellyer <ivana.kellyer@sentry.io>
Date: Wed, 13 Nov 2024 10:15:13 +0100
Subject: [PATCH 03/12] better wording

---
 MIGRATION_GUIDE.md | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/MIGRATION_GUIDE.md b/MIGRATION_GUIDE.md
index 052f4df0ba..3d6a7e896a 100644
--- a/MIGRATION_GUIDE.md
+++ b/MIGRATION_GUIDE.md
@@ -11,7 +11,7 @@ Looking to upgrade from Sentry SDK 2.x to 3.x? Here's a comprehensive list of wh
 - The SDK now supports Python 3.7 and higher.
 - `sentry_sdk.start_span` now only takes keyword arguments.
 - `sentry_sdk.start_span` no longer takes an explicit `span` argument.
-- The `sampled` argument of `sentry_sdk.start_span` is only taken into account for root spans (previously known as transactions).
+- `sentry_sdk.start_span` now accepts the `sampled` argument. It is however taken into account for root spans (previously known as transactions).
 - The `Span()` constructor does not accept a `hub` parameter anymore.
 - `Span.finish()` does not accept a `hub` parameter anymore.
 - The `Profile()` constructor does not accept a `hub` parameter anymore.

From cefb27ca9af9e7cefc47e5d17c8101f0936389a2 Mon Sep 17 00:00:00 2001
From: Ivana Kellyer <ivana.kellyer@sentry.io>
Date: Wed, 13 Nov 2024 10:24:25 +0100
Subject: [PATCH 04/12] reword and support parent_sampled

---
 MIGRATION_GUIDE.md                            |  2 +-
 .../integrations/opentelemetry/consts.py      |  3 +++
 .../integrations/opentelemetry/sampler.py     |  6 ++++-
 sentry_sdk/tracing.py                         |  5 +++++
 tests/tracing/test_sampling.py                | 22 +++++++++----------
 5 files changed, 24 insertions(+), 14 deletions(-)

diff --git a/MIGRATION_GUIDE.md b/MIGRATION_GUIDE.md
index 3d6a7e896a..11843083c0 100644
--- a/MIGRATION_GUIDE.md
+++ b/MIGRATION_GUIDE.md
@@ -11,7 +11,7 @@ Looking to upgrade from Sentry SDK 2.x to 3.x? Here's a comprehensive list of wh
 - The SDK now supports Python 3.7 and higher.
 - `sentry_sdk.start_span` now only takes keyword arguments.
 - `sentry_sdk.start_span` no longer takes an explicit `span` argument.
-- `sentry_sdk.start_span` now accepts the `sampled` argument. It is however taken into account for root spans (previously known as transactions).
+- `sentry_sdk.start_span` now accepts the `sampled` argument. It is however only taken into account for root spans (previously known as transactions).
 - The `Span()` constructor does not accept a `hub` parameter anymore.
 - `Span.finish()` does not accept a `hub` parameter anymore.
 - The `Profile()` constructor does not accept a `hub` parameter anymore.
diff --git a/sentry_sdk/integrations/opentelemetry/consts.py b/sentry_sdk/integrations/opentelemetry/consts.py
index 1585e8d893..8594b5c11c 100644
--- a/sentry_sdk/integrations/opentelemetry/consts.py
+++ b/sentry_sdk/integrations/opentelemetry/consts.py
@@ -31,3 +31,6 @@ class SentrySpanAttribute:
     SOURCE = "sentry.source"
     CONTEXT = "sentry.context"
     CUSTOM_SAMPLED = "sentry.custom_sampled"  # used for saving start_span(sampled=X)
+    CUSTOM_PARENT_SAMPLED = (
+        "sentry.custom_parent_sampled"  # used for saving start_span(parent_sampled=X)
+    )
diff --git a/sentry_sdk/integrations/opentelemetry/sampler.py b/sentry_sdk/integrations/opentelemetry/sampler.py
index 74a09d5056..b5dc872ff3 100644
--- a/sentry_sdk/integrations/opentelemetry/sampler.py
+++ b/sentry_sdk/integrations/opentelemetry/sampler.py
@@ -154,7 +154,11 @@ def should_sample(
 
         else:
             # Check if there is a parent with a sampling decision
-            parent_sampled = get_parent_sampled(parent_span_context, trace_id)
+            parent_sampled = attributes.get(SentrySpanAttribute.CUSTOM_PARENT_SAMPLED)
+
+            if parent_sampled is None:
+                parent_sampled = get_parent_sampled(parent_span_context, trace_id)
+
             if parent_sampled is not None:
                 sample_rate = parent_sampled
             else:
diff --git a/sentry_sdk/tracing.py b/sentry_sdk/tracing.py
index a69a6f98be..e4b4691fab 100644
--- a/sentry_sdk/tracing.py
+++ b/sentry_sdk/tracing.py
@@ -1212,6 +1212,7 @@ def __init__(
         attributes=None,  # type: OTelSpanAttributes
         only_if_parent=False,  # type: bool
         otel_span=None,  # type: Optional[OtelSpan]
+        parent_sampled=None,  # type: Optional[bool]
         **_,  # type: dict[str, object]
     ):
         # type: (...) -> None
@@ -1252,6 +1253,10 @@ def __init__(
                 attributes[SentrySpanAttribute.OP] = op
                 if sampled is not None:
                     attributes[SentrySpanAttribute.CUSTOM_SAMPLED] = sampled
+                if parent_sampled is not None:
+                    attributes[SentrySpanAttribute.CUSTOM_PARENT_SAMPLED] = (
+                        parent_sampled
+                    )
 
                 self._otel_span = tracer.start_span(
                     span_name, start_time=start_timestamp, attributes=attributes
diff --git a/tests/tracing/test_sampling.py b/tests/tracing/test_sampling.py
index 70baacc951..192cba133f 100644
--- a/tests/tracing/test_sampling.py
+++ b/tests/tracing/test_sampling.py
@@ -24,16 +24,16 @@ def test_sampling_decided_only_for_transactions(sentry_init, capture_events):
 
 
 @pytest.mark.parametrize("sampled", [True, False])
-def test_nested_transaction_sampling_override(sentry_init, sampled):
+def test_nested_span_sampling_override(sentry_init, sampled):
     sentry_init(traces_sample_rate=1.0)
 
-    with start_transaction(name="outer", sampled=sampled) as outer_transaction:
-        assert outer_transaction.sampled is sampled
-        with start_transaction(
-            name="inner", sampled=(not sampled)
-        ) as inner_transaction:
-            assert inner_transaction.sampled is not sampled
-        assert outer_transaction.sampled is sampled
+    with start_span(name="outer", sampled=sampled) as outer_span:
+        assert outer_span.sampled is sampled
+        with start_span(name="inner", sampled=(not sampled)) as inner_span:
+            # won't work because the child span inherits the sampling decision
+            # from the parent
+            assert inner_span.sampled is sampled
+        assert outer_span.sampled is sampled
 
 
 def test_no_double_sampling(sentry_init, capture_events):
@@ -177,10 +177,8 @@ def test_inherits_parent_sampling_decision_when_traces_sampler_undefined(
     mock_random_value = 0.25 if parent_sampling_decision is False else 0.75
 
     with mock.patch.object(random, "random", return_value=mock_random_value):
-        transaction = start_transaction(
-            name="dogpark", parent_sampled=parent_sampling_decision
-        )
-        assert transaction.sampled is parent_sampling_decision
+        span = start_span(name="dogpark", parent_sampled=parent_sampling_decision)
+        assert span.sampled is parent_sampling_decision
 
 
 @pytest.mark.parametrize("parent_sampling_decision", [True, False])

From 3fcbf65005ab2344928099f2644746025eba8474 Mon Sep 17 00:00:00 2001
From: Ivana Kellyer <ivana.kellyer@sentry.io>
Date: Wed, 13 Nov 2024 11:26:39 +0100
Subject: [PATCH 05/12] tests

---
 .../integrations/opentelemetry/sampler.py     | 17 ++++++---
 tests/tracing/test_sampling.py                | 38 ++++++++-----------
 2 files changed, 26 insertions(+), 29 deletions(-)

diff --git a/sentry_sdk/integrations/opentelemetry/sampler.py b/sentry_sdk/integrations/opentelemetry/sampler.py
index b5dc872ff3..aa18ba1300 100644
--- a/sentry_sdk/integrations/opentelemetry/sampler.py
+++ b/sentry_sdk/integrations/opentelemetry/sampler.py
@@ -141,24 +141,29 @@ def should_sample(
         # Check if there is a traces_sampler
         # Traces_sampler is responsible to check parent sampled to have full transactions.
         has_traces_sampler = callable(client.options.get("traces_sampler"))
+        custom_parent_sampled = attributes.get(
+            SentrySpanAttribute.CUSTOM_PARENT_SAMPLED
+        )
+        if custom_parent_sampled is not None:
+            parent_sampled = custom_parent_sampled
+        else:
+            parent_sampled = get_parent_sampled(parent_span_context, trace_id)
+        print("custom_parent_sampled", custom_parent_sampled)
+        print("get parent sampled", get_parent_sampled(parent_span_context, trace_id))
+
         if is_root_span and has_traces_sampler:
             sampling_context = {
                 "transaction_context": {
                     "name": name,
                     "op": attributes.get(SentrySpanAttribute.OP),
                 },
-                "parent_sampled": get_parent_sampled(parent_span_context, trace_id),
+                "parent_sampled": parent_sampled,
             }
             sampling_context.update(attributes)
             sample_rate = client.options["traces_sampler"](sampling_context)
 
         else:
             # Check if there is a parent with a sampling decision
-            parent_sampled = attributes.get(SentrySpanAttribute.CUSTOM_PARENT_SAMPLED)
-
-            if parent_sampled is None:
-                parent_sampled = get_parent_sampled(parent_span_context, trace_id)
-
             if parent_sampled is not None:
                 sample_rate = parent_sampled
             else:
diff --git a/tests/tracing/test_sampling.py b/tests/tracing/test_sampling.py
index 192cba133f..ce540050f7 100644
--- a/tests/tracing/test_sampling.py
+++ b/tests/tracing/test_sampling.py
@@ -6,21 +6,20 @@
 
 import sentry_sdk
 from sentry_sdk import start_span, start_transaction, capture_exception
-from sentry_sdk.tracing import Transaction
 from sentry_sdk.utils import logger
 
 
-def test_sampling_decided_only_for_transactions(sentry_init, capture_events):
+def test_sampling_decided_only_for_root_spans(sentry_init):
     sentry_init(traces_sample_rate=0.5)
 
-    with start_transaction(name="hi") as transaction:
-        assert transaction.sampled is not None
+    with start_span(name="outer1") as root_span1:
+        assert root_span1.sampled is not None
 
-        with start_span() as span:
-            assert span.sampled == transaction.sampled
+        with start_span(name="inner") as span:
+            assert span.sampled == root_span1.sampled
 
-    with start_span() as span:
-        assert span.sampled is None
+    with start_span(name="outer2") as root_span2:
+        assert root_span2.sampled is not None
 
 
 @pytest.mark.parametrize("sampled", [True, False])
@@ -185,7 +184,11 @@ def test_inherits_parent_sampling_decision_when_traces_sampler_undefined(
 def test_passes_parent_sampling_decision_in_sampling_context(
     sentry_init, parent_sampling_decision
 ):
-    sentry_init(traces_sample_rate=1.0)
+    def dummy_traces_sampler(sampling_context):
+        assert sampling_context["parent_sampled"] is parent_sampling_decision
+        return 1.0
+
+    sentry_init(traces_sample_rate=1.0, traces_sampler=dummy_traces_sampler)
 
     sentry_trace_header = (
         "12312012123120121231201212312012-1121201211212012-{sampled}".format(
@@ -193,20 +196,9 @@ def test_passes_parent_sampling_decision_in_sampling_context(
         )
     )
 
-    transaction = Transaction.continue_from_headers(
-        headers={"sentry-trace": sentry_trace_header}, name="dogpark"
-    )
-    spy = mock.Mock(wraps=transaction)
-    start_transaction(transaction=spy)
-
-    # there's only one call (so index at 0) and kwargs are always last in a call
-    # tuple (so index at -1)
-    sampling_context = spy._set_initial_sampling_decision.mock_calls[0][-1][
-        "sampling_context"
-    ]
-    assert "parent_sampled" in sampling_context
-    # because we passed in a spy, attribute access requires unwrapping
-    assert sampling_context["parent_sampled"]._mock_wraps is parent_sampling_decision
+    with sentry_sdk.continue_trace({"sentry-trace": sentry_trace_header}):
+        with sentry_sdk.start_span(name="dogpark"):
+            pass
 
 
 def test_passes_attributes_from_start_span_to_traces_sampler(

From 9600484725c330697609c5eb722f8058fe3f3cf5 Mon Sep 17 00:00:00 2001
From: Ivana Kellyer <ivana.kellyer@sentry.io>
Date: Wed, 13 Nov 2024 11:27:10 +0100
Subject: [PATCH 06/12] .

---
 sentry_sdk/integrations/opentelemetry/sampler.py | 2 --
 1 file changed, 2 deletions(-)

diff --git a/sentry_sdk/integrations/opentelemetry/sampler.py b/sentry_sdk/integrations/opentelemetry/sampler.py
index aa18ba1300..9f1a5de8c9 100644
--- a/sentry_sdk/integrations/opentelemetry/sampler.py
+++ b/sentry_sdk/integrations/opentelemetry/sampler.py
@@ -148,8 +148,6 @@ def should_sample(
             parent_sampled = custom_parent_sampled
         else:
             parent_sampled = get_parent_sampled(parent_span_context, trace_id)
-        print("custom_parent_sampled", custom_parent_sampled)
-        print("get parent sampled", get_parent_sampled(parent_span_context, trace_id))
 
         if is_root_span and has_traces_sampler:
             sampling_context = {

From 69dfe92ce655636ac0ca5ef173f06a3d32a19c45 Mon Sep 17 00:00:00 2001
From: Ivana Kellyer <ivana.kellyer@sentry.io>
Date: Wed, 13 Nov 2024 11:30:53 +0100
Subject: [PATCH 07/12] remove, this is not a change afait

---
 MIGRATION_GUIDE.md | 1 -
 1 file changed, 1 deletion(-)

diff --git a/MIGRATION_GUIDE.md b/MIGRATION_GUIDE.md
index 11843083c0..0095cafab7 100644
--- a/MIGRATION_GUIDE.md
+++ b/MIGRATION_GUIDE.md
@@ -11,7 +11,6 @@ Looking to upgrade from Sentry SDK 2.x to 3.x? Here's a comprehensive list of wh
 - The SDK now supports Python 3.7 and higher.
 - `sentry_sdk.start_span` now only takes keyword arguments.
 - `sentry_sdk.start_span` no longer takes an explicit `span` argument.
-- `sentry_sdk.start_span` now accepts the `sampled` argument. It is however only taken into account for root spans (previously known as transactions).
 - The `Span()` constructor does not accept a `hub` parameter anymore.
 - `Span.finish()` does not accept a `hub` parameter anymore.
 - The `Profile()` constructor does not accept a `hub` parameter anymore.

From 1b8521b66a6de4f26c0e3e57765864f6aed34fad Mon Sep 17 00:00:00 2001
From: Ivana Kellyer <ivana.kellyer@sentry.io>
Date: Wed, 13 Nov 2024 11:34:33 +0100
Subject: [PATCH 08/12] simplify

---
 sentry_sdk/integrations/opentelemetry/sampler.py | 8 ++------
 1 file changed, 2 insertions(+), 6 deletions(-)

diff --git a/sentry_sdk/integrations/opentelemetry/sampler.py b/sentry_sdk/integrations/opentelemetry/sampler.py
index 9f1a5de8c9..77878bb5ed 100644
--- a/sentry_sdk/integrations/opentelemetry/sampler.py
+++ b/sentry_sdk/integrations/opentelemetry/sampler.py
@@ -141,12 +141,8 @@ def should_sample(
         # Check if there is a traces_sampler
         # Traces_sampler is responsible to check parent sampled to have full transactions.
         has_traces_sampler = callable(client.options.get("traces_sampler"))
-        custom_parent_sampled = attributes.get(
-            SentrySpanAttribute.CUSTOM_PARENT_SAMPLED
-        )
-        if custom_parent_sampled is not None:
-            parent_sampled = custom_parent_sampled
-        else:
+        parent_sampled = attributes.get(SentrySpanAttribute.CUSTOM_PARENT_SAMPLED)
+        if parent_sampled is None:
             parent_sampled = get_parent_sampled(parent_span_context, trace_id)
 
         if is_root_span and has_traces_sampler:

From d9b7f7178344a45f635353e42748902591e46a26 Mon Sep 17 00:00:00 2001
From: Ivana Kellyer <ivana.kellyer@sentry.io>
Date: Wed, 13 Nov 2024 15:19:06 +0100
Subject: [PATCH 09/12] remove parent_sampled

---
 MIGRATION_GUIDE.md                            |  2 +-
 .../integrations/opentelemetry/consts.py      |  3 --
 .../integrations/opentelemetry/sampler.py     |  6 ++--
 sentry_sdk/tracing.py                         |  4 ---
 tests/tracing/test_sampling.py                | 30 -------------------
 5 files changed, 3 insertions(+), 42 deletions(-)

diff --git a/MIGRATION_GUIDE.md b/MIGRATION_GUIDE.md
index 0095cafab7..7b45b480bb 100644
--- a/MIGRATION_GUIDE.md
+++ b/MIGRATION_GUIDE.md
@@ -10,7 +10,7 @@ Looking to upgrade from Sentry SDK 2.x to 3.x? Here's a comprehensive list of wh
 
 - The SDK now supports Python 3.7 and higher.
 - `sentry_sdk.start_span` now only takes keyword arguments.
-- `sentry_sdk.start_span` no longer takes an explicit `span` argument.
+- `sentry_sdk.start_transaction`/`sentry_sdk.start_span` no longer takes the following arguments: `span`, `parent_sampled`.
 - The `Span()` constructor does not accept a `hub` parameter anymore.
 - `Span.finish()` does not accept a `hub` parameter anymore.
 - The `Profile()` constructor does not accept a `hub` parameter anymore.
diff --git a/sentry_sdk/integrations/opentelemetry/consts.py b/sentry_sdk/integrations/opentelemetry/consts.py
index 8594b5c11c..1585e8d893 100644
--- a/sentry_sdk/integrations/opentelemetry/consts.py
+++ b/sentry_sdk/integrations/opentelemetry/consts.py
@@ -31,6 +31,3 @@ class SentrySpanAttribute:
     SOURCE = "sentry.source"
     CONTEXT = "sentry.context"
     CUSTOM_SAMPLED = "sentry.custom_sampled"  # used for saving start_span(sampled=X)
-    CUSTOM_PARENT_SAMPLED = (
-        "sentry.custom_parent_sampled"  # used for saving start_span(parent_sampled=X)
-    )
diff --git a/sentry_sdk/integrations/opentelemetry/sampler.py b/sentry_sdk/integrations/opentelemetry/sampler.py
index 77878bb5ed..cb722694ac 100644
--- a/sentry_sdk/integrations/opentelemetry/sampler.py
+++ b/sentry_sdk/integrations/opentelemetry/sampler.py
@@ -141,9 +141,6 @@ def should_sample(
         # Check if there is a traces_sampler
         # Traces_sampler is responsible to check parent sampled to have full transactions.
         has_traces_sampler = callable(client.options.get("traces_sampler"))
-        parent_sampled = attributes.get(SentrySpanAttribute.CUSTOM_PARENT_SAMPLED)
-        if parent_sampled is None:
-            parent_sampled = get_parent_sampled(parent_span_context, trace_id)
 
         if is_root_span and has_traces_sampler:
             sampling_context = {
@@ -151,13 +148,14 @@ def should_sample(
                     "name": name,
                     "op": attributes.get(SentrySpanAttribute.OP),
                 },
-                "parent_sampled": parent_sampled,
+                "parent_sampled": get_parent_sampled(parent_span_context, trace_id),
             }
             sampling_context.update(attributes)
             sample_rate = client.options["traces_sampler"](sampling_context)
 
         else:
             # Check if there is a parent with a sampling decision
+            parent_sampled = get_parent_sampled(parent_span_context, trace_id)
             if parent_sampled is not None:
                 sample_rate = parent_sampled
             else:
diff --git a/sentry_sdk/tracing.py b/sentry_sdk/tracing.py
index e4b4691fab..535b936261 100644
--- a/sentry_sdk/tracing.py
+++ b/sentry_sdk/tracing.py
@@ -1253,10 +1253,6 @@ def __init__(
                 attributes[SentrySpanAttribute.OP] = op
                 if sampled is not None:
                     attributes[SentrySpanAttribute.CUSTOM_SAMPLED] = sampled
-                if parent_sampled is not None:
-                    attributes[SentrySpanAttribute.CUSTOM_PARENT_SAMPLED] = (
-                        parent_sampled
-                    )
 
                 self._otel_span = tracer.start_span(
                     span_name, start_time=start_timestamp, attributes=attributes
diff --git a/tests/tracing/test_sampling.py b/tests/tracing/test_sampling.py
index ce540050f7..bee1a6a6d4 100644
--- a/tests/tracing/test_sampling.py
+++ b/tests/tracing/test_sampling.py
@@ -137,21 +137,6 @@ def test_prefers_traces_sampler_to_traces_sample_rate(
     assert transaction.sampled is traces_sampler_return_value
 
 
-@pytest.mark.parametrize("parent_sampling_decision", [True, False])
-def test_ignores_inherited_sample_decision_when_traces_sampler_defined(
-    sentry_init, parent_sampling_decision
-):
-    # make traces_sampler pick the opposite of the inherited decision, to prove
-    # that traces_sampler takes precedence
-    traces_sampler = mock.Mock(return_value=not parent_sampling_decision)
-    sentry_init(traces_sampler=traces_sampler)
-
-    transaction = start_transaction(
-        name="dogpark", parent_sampled=parent_sampling_decision
-    )
-    assert transaction.sampled is not parent_sampling_decision
-
-
 @pytest.mark.parametrize("explicit_decision", [True, False])
 def test_traces_sampler_doesnt_overwrite_explicitly_passed_sampling_decision(
     sentry_init, explicit_decision
@@ -165,21 +150,6 @@ def test_traces_sampler_doesnt_overwrite_explicitly_passed_sampling_decision(
     assert transaction.sampled is explicit_decision
 
 
-@pytest.mark.parametrize("parent_sampling_decision", [True, False])
-def test_inherits_parent_sampling_decision_when_traces_sampler_undefined(
-    sentry_init, parent_sampling_decision
-):
-    # make sure the parent sampling decision is the opposite of what
-    # traces_sample_rate would produce, to prove the inheritance takes
-    # precedence
-    sentry_init(traces_sample_rate=0.5)
-    mock_random_value = 0.25 if parent_sampling_decision is False else 0.75
-
-    with mock.patch.object(random, "random", return_value=mock_random_value):
-        span = start_span(name="dogpark", parent_sampled=parent_sampling_decision)
-        assert span.sampled is parent_sampling_decision
-
-
 @pytest.mark.parametrize("parent_sampling_decision", [True, False])
 def test_passes_parent_sampling_decision_in_sampling_context(
     sentry_init, parent_sampling_decision

From 8ae99c087874024b755c58ac39386f09602c5b9c Mon Sep 17 00:00:00 2001
From: Ivana Kellyer <ivana.kellyer@sentry.io>
Date: Wed, 13 Nov 2024 15:31:23 +0100
Subject: [PATCH 10/12] fix tests

---
 tests/tracing/test_sampling.py | 40 ++++++++++++++++++++++++++++++++++
 1 file changed, 40 insertions(+)

diff --git a/tests/tracing/test_sampling.py b/tests/tracing/test_sampling.py
index bee1a6a6d4..2c6f2ca8fc 100644
--- a/tests/tracing/test_sampling.py
+++ b/tests/tracing/test_sampling.py
@@ -137,6 +137,28 @@ def test_prefers_traces_sampler_to_traces_sample_rate(
     assert transaction.sampled is traces_sampler_return_value
 
 
+@pytest.mark.parametrize("parent_sampling_decision", [True, False])
+def test_ignores_inherited_sample_decision_when_traces_sampler_defined(
+    sentry_init, parent_sampling_decision
+):
+    # make traces_sampler pick the opposite of the inherited decision, to prove
+    # that traces_sampler takes precedence
+    traces_sampler = mock.Mock(return_value=not parent_sampling_decision)
+    sentry_init(traces_sampler=traces_sampler)
+
+    sentry_trace_header = (
+        "12312012123120121231201212312012-1121201211212012-{sampled}".format(
+            sampled=int(parent_sampling_decision)
+        )
+    )
+
+    with sentry_sdk.continue_trace({"sentry-trace": sentry_trace_header}):
+        with sentry_sdk.start_span(name="dogpark") as span:
+            pass
+
+    assert span.sampled is not parent_sampling_decision
+
+
 @pytest.mark.parametrize("explicit_decision", [True, False])
 def test_traces_sampler_doesnt_overwrite_explicitly_passed_sampling_decision(
     sentry_init, explicit_decision
@@ -150,6 +172,24 @@ def test_traces_sampler_doesnt_overwrite_explicitly_passed_sampling_decision(
     assert transaction.sampled is explicit_decision
 
 
+@pytest.mark.parametrize("parent_sampling_decision", [True, False])
+def test_inherits_parent_sampling_decision_when_traces_sampler_undefined(
+    sentry_init, parent_sampling_decision
+):
+    # make sure the parent sampling decision is the opposite of what
+    # traces_sample_rate would produce, to prove the inheritance takes
+    # precedence
+    sentry_init(traces_sample_rate=0.5)
+    mock_random_value = 0.25 if parent_sampling_decision is False else 0.75
+
+    with mock.patch.object(random, "random", return_value=mock_random_value):
+        with start_span(name="catpark", sampled=parent_sampling_decision):
+            with start_span(name="dogpark") as span:
+                pass
+
+    assert span.sampled is parent_sampling_decision
+
+
 @pytest.mark.parametrize("parent_sampling_decision", [True, False])
 def test_passes_parent_sampling_decision_in_sampling_context(
     sentry_init, parent_sampling_decision

From a11ff463cdce702abfbdb8fc7b6969fcd9cbbf19 Mon Sep 17 00:00:00 2001
From: Ivana Kellyer <ivana.kellyer@sentry.io>
Date: Wed, 13 Nov 2024 15:32:39 +0100
Subject: [PATCH 11/12] remove all parent_sampled stuff

---
 sentry_sdk/tracing.py | 1 -
 1 file changed, 1 deletion(-)

diff --git a/sentry_sdk/tracing.py b/sentry_sdk/tracing.py
index 535b936261..a69a6f98be 100644
--- a/sentry_sdk/tracing.py
+++ b/sentry_sdk/tracing.py
@@ -1212,7 +1212,6 @@ def __init__(
         attributes=None,  # type: OTelSpanAttributes
         only_if_parent=False,  # type: bool
         otel_span=None,  # type: Optional[OtelSpan]
-        parent_sampled=None,  # type: Optional[bool]
         **_,  # type: dict[str, object]
     ):
         # type: (...) -> None

From 032a6c4fe4ede48d4d9b495001ca32df7bcc91a3 Mon Sep 17 00:00:00 2001
From: Ivana Kellyer <ivana.kellyer@sentry.io>
Date: Thu, 14 Nov 2024 11:55:27 +0100
Subject: [PATCH 12/12] fix test

---
 tests/tracing/test_sampling.py | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/tests/tracing/test_sampling.py b/tests/tracing/test_sampling.py
index 2c6f2ca8fc..8ef362a1e8 100644
--- a/tests/tracing/test_sampling.py
+++ b/tests/tracing/test_sampling.py
@@ -182,8 +182,13 @@ def test_inherits_parent_sampling_decision_when_traces_sampler_undefined(
     sentry_init(traces_sample_rate=0.5)
     mock_random_value = 0.25 if parent_sampling_decision is False else 0.75
 
+    sentry_trace_header = (
+        "12312012123120121231201212312012-1121201211212012-{sampled}".format(
+            sampled=int(parent_sampling_decision)
+        )
+    )
     with mock.patch.object(random, "random", return_value=mock_random_value):
-        with start_span(name="catpark", sampled=parent_sampling_decision):
+        with sentry_sdk.continue_trace({"sentry-trace": sentry_trace_header}):
             with start_span(name="dogpark") as span:
                 pass