diff --git a/litellm/llms/bedrock/chat/chat_completions/transformation.py b/litellm/llms/bedrock/chat/chat_completions/transformation.py
index 123e4a9e6b4..131d4afae5b 100644
--- a/litellm/llms/bedrock/chat/chat_completions/transformation.py
+++ b/litellm/llms/bedrock/chat/chat_completions/transformation.py
@@ -41,6 +41,7 @@ from litellm.llms.bedrock.common_utils import (
     bedrock_model_is_openai_gpt,
     bedrock_rejects_stop_sequences,
     bedrock_runtime_chat_completions_serves_reasoning_inline,
+    bedrock_serves_service_tier,
     split_bedrock_region_path,
 )
 from litellm.llms.openai.chat.gpt_transformation import OpenAIChatCompletionStreamingHandler
@@ -309,6 +310,13 @@ def with_max_completion_tokens(params: Mapping[str, object]) -> Mapping[str, obj
     )
 
 
+def _unsupported_service_tier(model: str, raw_params: Mapping[str, object]) -> frozenset[str]:
+    service_tier: Final = raw_params.get("service_tier")
+    if not isinstance(service_tier, str) or bedrock_serves_service_tier(model, service_tier):
+        return frozenset()
+    return frozenset(("service_tier",))
+
+
 class AmazonBedrockRuntimeChatCompletionsConfig(OpenAILikeChatConfig):
     def __init__(self, aws_signer: BaseAWSLLM | None = None) -> None:
         super().__init__()
@@ -446,11 +454,22 @@ class AmazonBedrockRuntimeChatCompletionsConfig(OpenAILikeChatConfig):
                 status_code=400,
             )
         rejected_stop: Final = frozenset(("stop",)) if bedrock_rejects_stop_sequences(model) else frozenset[str]()
+        unsupported_tier: Final = _unsupported_service_tier(model, raw_params)
+        if unsupported_tier and not (litellm.drop_params or drop_params):
+            raise litellm.utils.UnsupportedParamsError(
+                message=(
+                    f"{model} does not support service_tier={raw_params['service_tier']!r} on Bedrock. "
+                    "To drop unsupported params, set `litellm.drop_params = True`."
+                ),
+                status_code=400,
+            )
         return dict(
             without_refused_reasoning_effort(
                 model,
                 with_max_completion_tokens(
-                    _without_params(mapped, refused_while_reasoning | malformed_effort | rejected_stop)
+                    _without_params(
+                        mapped, refused_while_reasoning | malformed_effort | rejected_stop | unsupported_tier
+                    )
                 ),
             )
         )
diff --git a/litellm/llms/bedrock/chat/converse_transformation.py b/litellm/llms/bedrock/chat/converse_transformation.py
index f54c352fd6e..9e6352c3c2f 100644
--- a/litellm/llms/bedrock/chat/converse_transformation.py
+++ b/litellm/llms/bedrock/chat/converse_transformation.py
@@ -64,6 +64,7 @@ from litellm.llms.bedrock.common_utils import (
     bedrock_model_supports_regex_lookaround,
     bedrock_native_output_format,
     bedrock_native_output_is_opt_in,
+    bedrock_serves_service_tier,
     bedrock_supports_tool_search,
     deployment_model_info,
     requests_output_config_format,
@@ -1210,7 +1211,7 @@ class AmazonConverseConfig(BaseConfig):
             if param == "requestMetadata":
                 self._map_request_metadata_param(value, optional_params, drop_params)
             if param == "service_tier" and isinstance(value, str):
-                self._map_service_tier_param(value, optional_params)
+                self._map_service_tier_param(value, optional_params, model=model, drop_params=drop_params)
 
             if param == "web_search_options" and isinstance(value, dict):
                 # Note: we use `isinstance(value, dict)` instead of `value and isinstance(value, dict)`
@@ -1264,17 +1265,27 @@ class AmazonConverseConfig(BaseConfig):
         if mapped is not None:
             optional_params["context_management"] = mapped
 
-    def _map_service_tier_param(self, value: str, optional_params: dict) -> None:
+    def _map_service_tier_param(self, value: str, optional_params: dict, model: str, drop_params: bool) -> None:
         """Map OpenAI service_tier (string) to Bedrock serviceTier (object).
 
         OpenAI values: "auto", "default", "flex", "priority"
         Bedrock values: "default", "flex", "priority" (no "auto")
         """
-        bedrock_tier = value
-        if value == "auto":
-            bedrock_tier = "default"  # Bedrock doesn't support "auto"
-        if bedrock_tier in ("default", "flex", "priority"):
-            optional_params["serviceTier"] = {"type": bedrock_tier}
+        bedrock_tier: Final = "default" if value == "auto" else value
+        if bedrock_tier not in ("default", "flex", "priority"):
+            return
+        if not bedrock_serves_service_tier(model, bedrock_tier):
+            if not (litellm.drop_params or drop_params):
+                raise litellm.utils.UnsupportedParamsError(
+                    message=(
+                        f"{model} does not support service_tier={value!r} on Bedrock. "
+                        "To drop unsupported params, set `litellm.drop_params = True`."
+                    ),
+                    status_code=400,
+                )
+            verbose_logger.debug("Dropping unsupported `service_tier=%s` for Bedrock model=%s.", value, model)
+            return
+        optional_params["serviceTier"] = {"type": bedrock_tier}
 
     def _translate_response_format_param(
         self,
diff --git a/litellm/llms/bedrock/common_utils.py b/litellm/llms/bedrock/common_utils.py
index fde995c7907..2ca7bef7e0a 100644
--- a/litellm/llms/bedrock/common_utils.py
+++ b/litellm/llms/bedrock/common_utils.py
@@ -1314,6 +1314,28 @@ def _mantle_api_base_from_env() -> str | None:
     return next((base[: -len(suffix)] for suffix in _MANTLE_OPENAI_BASE_SUFFIXES if base.endswith(suffix)), base)
 
 
+def bedrock_serves_service_tier(model: str, service_tier: str) -> bool:
+    """Whether AWS sells this Bedrock model at the requested ``service_tier``.
+
+    AWS enables priority and flex per model, not per provider (Nova 2, gpt-oss and Kimi serve
+    them, every Claude and GPT 5.6 Terra answer ``The provided service tier is not supported for
+    this model``, checked live on 2026-10-27). The price map carries a ``*_cost_per_token_<tier>``
+    row for exactly the models that serve a tier, so a non-null price is the capability signal (the
+    proxy normalizes every row to the full ModelInfo shape, so key presence alone means nothing). ``default``
+    and ``auto`` are always served, and a model absent from the price map has no signal and is
+    forwarded as before.
+    """
+    from litellm.litellm_core_utils.llm_cost_calc.utils import get_service_tier_cost_key
+
+    cost_key: Final = get_service_tier_cost_key("input_cost_per_token", service_tier)
+    if cost_key == "input_cost_per_token":
+        return True
+    entries: Final = tuple(entry for entry in _bedrock_price_map_entries(model) if entry is not None)
+    if not entries:
+        return True
+    return any(entry.get(cost_key) is not None for entry in entries)
+
+
 def bedrock_reasoning_effort_disabled(model: str, effort: str) -> bool:
     from litellm.utils import is_explicitly_disabled_factory
 
diff --git a/tests/unit/llms/bedrock/chat/chat_completions/test_bedrock_chat_completions_transformation.py b/tests/unit/llms/bedrock/chat/chat_completions/test_bedrock_chat_completions_transformation.py
index 3faae2e3289..cf65facf6ee 100644
--- a/tests/unit/llms/bedrock/chat/chat_completions/test_bedrock_chat_completions_transformation.py
+++ b/tests/unit/llms/bedrock/chat/chat_completions/test_bedrock_chat_completions_transformation.py
@@ -1704,3 +1704,47 @@ def test_positional_tool_call_ids_are_minted_for_gpt_too(local_cost_map, fake_aw
     ids = [tool_call.id for tool_call in response.choices[0].message.tool_calls]
     assert len(set(ids)) == 2
     assert all(re.fullmatch(r"call_[0-9a-f]{32}", tool_call_id) for tool_call_id in ids)
+
+
+def test_native_chat_completions_drops_service_tier_the_model_does_not_sell(local_cost_map, monkeypatch):
+    """GPT 5.6 Terra on Bedrock answers priority/flex with `'priority' is not supported for
+    'service_tier' on this model`, so under drop_params the tier is dropped before the call."""
+    monkeypatch.setattr(litellm, "drop_params", False)
+    config = AmazonBedrockRuntimeChatCompletionsConfig()
+
+    result = config.map_openai_params(
+        non_default_params={"service_tier": "priority", "max_tokens": 5},
+        optional_params={},
+        model="us.openai.gpt-5.6-terra",
+        drop_params=True,
+    )
+
+    assert "service_tier" not in result
+    assert result["max_completion_tokens"] == 5
+
+
+def test_native_chat_completions_raises_on_service_tier_the_model_does_not_sell(local_cost_map, monkeypatch):
+    monkeypatch.setattr(litellm, "drop_params", False)
+    config = AmazonBedrockRuntimeChatCompletionsConfig()
+
+    with pytest.raises(litellm.utils.UnsupportedParamsError, match="service_tier='priority'"):
+        config.map_openai_params(
+            non_default_params={"service_tier": "priority"},
+            optional_params={},
+            model="us.openai.gpt-5.6-terra",
+            drop_params=False,
+        )
+
+
+def test_native_chat_completions_keeps_default_service_tier(local_cost_map, monkeypatch):
+    monkeypatch.setattr(litellm, "drop_params", False)
+    config = AmazonBedrockRuntimeChatCompletionsConfig()
+
+    result = config.map_openai_params(
+        non_default_params={"service_tier": "default"},
+        optional_params={},
+        model="us.openai.gpt-5.6-terra",
+        drop_params=False,
+    )
+
+    assert result["service_tier"] == "default"
diff --git a/tests/unit/llms/bedrock/chat/test_converse_transformation.py b/tests/unit/llms/bedrock/chat/test_converse_transformation.py
index 154797bab5a..c8cf0a0b304 100644
--- a/tests/unit/llms/bedrock/chat/test_converse_transformation.py
+++ b/tests/unit/llms/bedrock/chat/test_converse_transformation.py
@@ -10789,3 +10789,61 @@ def test_a_deployment_with_a_batch_control_plane_endpoint_keeps_it_out_of_chat_r
 
     assert response.choices[0].message.content == "ok"
     assert "aws_bedrock_control_plane_endpoint" not in route.calls[0].request.content.decode()
+
+
+def test_converse_service_tier_dropped_on_models_without_that_tier_under_drop_params():
+    """Bedrock sells priority/flex per model. Claude has neither, so with drop_params the tier must
+    be dropped instead of forwarded to AWS's `The provided service tier is not supported` 400."""
+    config = AmazonConverseConfig()
+
+    result = config.map_openai_params(
+        non_default_params={"service_tier": "priority"},
+        optional_params={},
+        model="us.anthropic.claude-sonnet-4-5-20250929-v1:0",
+        drop_params=True,
+    )
+
+    assert "serviceTier" not in result
+
+
+def test_converse_service_tier_raises_on_models_without_that_tier_without_drop_params(monkeypatch):
+    monkeypatch.setattr(litellm, "drop_params", False)
+    config = AmazonConverseConfig()
+
+    with pytest.raises(litellm.utils.UnsupportedParamsError, match="service_tier='flex'"):
+        config.map_openai_params(
+            non_default_params={"service_tier": "flex"},
+            optional_params={},
+            model="us.anthropic.claude-haiku-4-5-20251001-v1:0",
+            drop_params=False,
+        )
+
+
+@pytest.mark.parametrize("service_tier", ["priority", "flex"])
+def test_converse_service_tier_forwarded_on_models_that_sell_it(monkeypatch, service_tier):
+    monkeypatch.setattr(litellm, "drop_params", False)
+    config = AmazonConverseConfig()
+
+    result = config.map_openai_params(
+        non_default_params={"service_tier": service_tier},
+        optional_params={},
+        model="us.amazon.nova-2-lite-v1:0",
+        drop_params=False,
+    )
+
+    assert result["serviceTier"] == {"type": service_tier}
+
+
+@pytest.mark.parametrize("service_tier", ["default", "auto"])
+def test_converse_default_and_auto_service_tier_always_forwarded(monkeypatch, service_tier):
+    monkeypatch.setattr(litellm, "drop_params", False)
+    config = AmazonConverseConfig()
+
+    result = config.map_openai_params(
+        non_default_params={"service_tier": service_tier},
+        optional_params={},
+        model="us.anthropic.claude-sonnet-4-5-20250929-v1:0",
+        drop_params=False,
+    )
+
+    assert result["serviceTier"] == {"type": "default"}
diff --git a/tests/unit/llms/bedrock/test_bedrock_common_utils.py b/tests/unit/llms/bedrock/test_bedrock_common_utils.py
index dd89d9c46b6..e02ff1c8d26 100644
--- a/tests/unit/llms/bedrock/test_bedrock_common_utils.py
+++ b/tests/unit/llms/bedrock/test_bedrock_common_utils.py
@@ -1,13 +1,21 @@
 
-import asyncio, importlib, litellm, litellm.litellm_core_utils.get_model_cost_map as bedrock_govcloud_model_cost_map, pytest
+import asyncio
+import importlib
+from collections.abc import Iterator
 from typing import Final
+from unittest.mock import Mock, patch
 
+import pytest
 
-from litellm.llms.bedrock.common_utils import(
+import litellm
+import litellm.litellm_core_utils.get_model_cost_map as bedrock_govcloud_model_cost_map
+from litellm import completion
+from litellm.llms.bedrock.common_utils import (
     AmazonBedrockGlobalConfig,
     BedrockModelInfo,
     NativeOutputFallback,
     bedrock_native_output_is_opt_in,
+    bedrock_serves_service_tier,
     bedrock_strict_tools_fallback,
     deployment_model_info,
     extract_model_name_from_bedrock_arn,
@@ -18,11 +26,8 @@ from litellm.llms.bedrock.common_utils import(
     strip_bedrock_throughput_suffix,
     without_bedrock_native_output_opt_in,
 )
-from collections.abc import Iterator
-from litellm import completion
 from litellm.llms.bedrock.count_tokens.bedrock_token_counter import BedrockTokenCounter
 from tests._vcr_conftest_common import install_live_call_probe, record_vcr_outcome
-from unittest.mock import Mock, patch
 
 # --------------------------------------------------------------------------- #
 # get_bedrock_response_stream_shape lazy-load tests                           #
@@ -2036,6 +2041,7 @@ class TestBedrockGovCloudSupport:
 @pytest.mark.parametrize("missing", ["botocore", "unrelated_dependency"])
 def test_event_decoder_reports_only_missing_aws_dependency(missing):
     from unittest.mock import patch
+
     from litellm.llms.bedrock.common_utils import BedrockEventStreamDecoderBase
 
     failure = ModuleNotFoundError("missing dependency", name=missing)
@@ -2229,3 +2235,38 @@ def test_bedrock_strict_tools_fallback_retries_only_when_the_request_sent_strict
     fallback: Final = bedrock_strict_tools_fallback(model, {"tools": tools}, litellm_params)
 
     assert (fallback is not None) == sent_strict
+
+
+@pytest.mark.parametrize(
+    ("model", "service_tier", "expected"),
+    [
+        ("us.anthropic.claude-sonnet-4-5-20250929-v1:0", "priority", False),
+        ("us.anthropic.claude-sonnet-4-5-20250929-v1:0", "default", True),
+        ("us.anthropic.claude-sonnet-4-5-20250929-v1:0", "auto", True),
+        ("us.amazon.nova-2-lite-v1:0", "flex", True),
+        ("bedrock/us-west-2/moonshotai.kimi-k2.5", "flex", True),
+        ("a-model-the-price-map-has-never-heard-of", "priority", True),
+    ],
+)
+def test_bedrock_serves_service_tier_follows_price_map_tier_rows(model, service_tier, expected):
+    """A Bedrock model serves a tier exactly when its price-map row carries that tier's pricing.
+    Unknown models have no signal and keep being forwarded."""
+    assert bedrock_serves_service_tier(model, service_tier) is expected
+
+
+def test_bedrock_serves_service_tier_ignores_null_tier_prices_from_normalized_rows(monkeypatch):
+    """The proxy expands every price-map row to the full ModelInfo shape, so a Claude row carries
+    `input_cost_per_token_priority: None`. A null price is no signal that AWS sells the tier."""
+    monkeypatch.setitem(
+        litellm.model_cost,
+        "normalized.claude-row",
+        {"litellm_provider": "bedrock_converse", "input_cost_per_token": 1e-6, "input_cost_per_token_priority": None},
+    )
+    monkeypatch.setitem(
+        litellm.model_cost,
+        "normalized.nova-row",
+        {"litellm_provider": "bedrock_converse", "input_cost_per_token": 1e-6, "input_cost_per_token_priority": 2e-6},
+    )
+
+    assert bedrock_serves_service_tier("normalized.claude-row", "priority") is False
+    assert bedrock_serves_service_tier("normalized.nova-row", "priority") is True