diff --git a/litellm/router.py b/litellm/router.py
index f40390098a6..3bd4378c689 100644
--- a/litellm/router.py
+++ b/litellm/router.py
@@ -7946,10 +7946,27 @@ class Router:
         (those that have a static model_cost entry). Mutates
         ``model_info_dict`` in place.
         """
-        bare_model_name = litellm_params.get("model")
-        if not bare_model_name:
+        model_param = litellm_params.get("model")
+        if not model_param:
             return
-        canonical = litellm.model_cost.get(bare_model_name)
+        # litellm.model_cost keys are mostly bare (e.g. "claude-3-opus-20240229")
+        # while `litellm_params.model` carries the user-facing
+        # `<provider>/<model>` shape (e.g. "anthropic/claude-3-opus-20240229").
+        # Try the raw value first to cover entries that DO keep the slash
+        # (bedrock uses a `.` separator already, but some "provider/model"
+        # keys exist for non-OpenAI shapes); fall back to the
+        # `get_llm_provider` split, which is the same canonical normalization
+        # used by `get_model_info` and the cost calculator.
+        canonical = litellm.model_cost.get(model_param)
+        if canonical is None:
+            try:
+                bare_model_name, _, _, _ = get_llm_provider(model=model_param)
+                if bare_model_name and bare_model_name != model_param:
+                    canonical = litellm.model_cost.get(bare_model_name)
+            except Exception:
+                # Don't let an unknown-provider parsing exception break
+                # deployment creation. No canonical -> no backfill.
+                pass
         if not canonical:
             return
         for field in CustomPricingLiteLLMParams.model_fields.keys():
diff --git a/tests/test_litellm/test_router_backfill_cost_fields.py b/tests/test_litellm/test_router_backfill_cost_fields.py
index 2f7d3b2e5a0..1a72ac49338 100644
--- a/tests/test_litellm/test_router_backfill_cost_fields.py
+++ b/tests/test_litellm/test_router_backfill_cost_fields.py
@@ -206,3 +206,49 @@ def test_backfill_cost_fields_from_canonical_direct_call():
             assert (
                 model_info_dict.get(field) == canonical[field]
             ), f"{field} should have been backfilled from canonical entry"
+
+
+def test_provider_prefixed_model_resolves_to_canonical():
+    """Regression for greptile P1 on #30383: dashboard /model/new stores
+    the user-facing model as `anthropic/claude-haiku-4-5-20251001` in
+    `litellm_params.model`, but `litellm.model_cost` keys are bare
+    (no `provider/` prefix). A raw `model_cost.get(litellm_params.model)`
+    misses; backfill must fall back to `get_llm_provider` to strip the
+    prefix, otherwise the entire fix silently no-ops for the most
+    common user-facing model-name shape.
+    """
+    deployment_uuid = "backfill-prefixed-uuid"
+    litellm.model_cost.pop(deployment_uuid, None)
+
+    # Verify the premise: prefixed lookup misses, bare lookup hits
+    assert litellm.model_cost.get(f"anthropic/{KNOWN_MODEL}") is None, (
+        "test premise broken — litellm.model_cost now contains "
+        "`anthropic/...` keys; review whether backfill stripping is "
+        "still required"
+    )
+    assert (
+        litellm.model_cost.get(KNOWN_MODEL) is not None
+    ), "bundled JSON should contain bare KNOWN_MODEL"
+
+    # litellm_params.model carries the user-facing `provider/model` form
+    _build_router(deployment_uuid=deployment_uuid, model=f"anthropic/{KNOWN_MODEL}")
+
+    entry = litellm.model_cost.get(deployment_uuid, {})
+    canonical = litellm.model_cost[KNOWN_MODEL]
+    # Cache rates must have been backfilled from the bare canonical entry
+    backfilled_at_least_one = False
+    for field in (
+        "cache_creation_input_token_cost",
+        "cache_read_input_token_cost",
+    ):
+        if canonical.get(field) is not None:
+            assert entry.get(field) == canonical[field], (
+                f"{field} must be backfilled from canonical bare entry "
+                f"when litellm_params.model has a provider/ prefix; "
+                f"got entry={entry.get(field)!r}, canonical={canonical[field]!r}"
+            )
+            backfilled_at_least_one = True
+    assert backfilled_at_least_one, (
+        "test setup expected canonical to carry at least one cache rate "
+        "to backfill; bundled JSON may have changed"
+    )