From ff9f2566a7a6d6cb68b79366d8aa970bc368ddc8 Mon Sep 17 00:00:00 2001
From: Aldous <aldous@ndstudio.gov>
Date: Wed, 2 Sep 2026 11:37:30 -0400
Subject: [PATCH] fix(anthropic): don't double-prefix Bedrock cross-region
 inference profile model IDs

---
 providers/anthropic/bedrock.go      | 30 +++++++++++---
 providers/anthropic/bedrock_test.go | 62 +++++++++++++++++++++++++++++
 2 files changed, 87 insertions(+), 5 deletions(-)
 create mode 100644 providers/anthropic/bedrock_test.go

diff --git a/providers/anthropic/bedrock.go b/providers/anthropic/bedrock.go
index f036dde1e..b49499ced 100644
--- a/providers/anthropic/bedrock.go
+++ b/providers/anthropic/bedrock.go
@@ -22,14 +22,34 @@ func bedrockBasicAuthConfig(apiKey, region string) aws.Config {
 	}
 }
 
+// bedrockInferenceProfilePrefixes are the cross-region inference
+// profile prefixes Bedrock model IDs may already carry. IDs starting
+// with one of these are fully qualified and must not be prefixed
+// again with the caller's region.
+var bedrockInferenceProfilePrefixes = []string{
+	"global.",
+	"us-gov.",
+	"us.",
+	"eu.",
+	"apac.",
+	"ap.",
+	"jp.",
+	"au.",
+	"ca.",
+	"sa.",
+	"il.",
+	"mx.",
+}
+
 func bedrockPrefixModelWithRegion(modelID, region string) string {
+	for _, prefix := range bedrockInferenceProfilePrefixes {
+		if strings.HasPrefix(modelID, prefix) {
+			return modelID
+		}
+	}
 	region = resolveBedrockRegion(region)
 	if len(region) < 2 {
 		return modelID
 	}
-	prefix := region[:2] + "."
-	if strings.HasPrefix(modelID, prefix) {
-		return modelID
-	}
-	return prefix + modelID
+	return region[:2] + "." + modelID
 }
diff --git a/providers/anthropic/bedrock_test.go b/providers/anthropic/bedrock_test.go
new file mode 100644
index 000000000..4fe7d189a
--- /dev/null
+++ b/providers/anthropic/bedrock_test.go
@@ -0,0 +1,62 @@
+package anthropic
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestBedrockPrefixModelWithRegion(t *testing.T) {
+	t.Parallel()
+
+	tests := []struct {
+		name    string
+		modelID string
+		region  string
+		want    string
+	}{
+		{
+			name:    "bare model id gets region prefix",
+			modelID: "anthropic.claude-fable-5-1",
+			region:  "us-east-1",
+			want:    "us.anthropic.claude-fable-5-1",
+		},
+		{
+			name:    "matching geo prefix is preserved",
+			modelID: "us.anthropic.claude-fable-5-1",
+			region:  "us-east-1",
+			want:    "us.anthropic.claude-fable-5-1",
+		},
+		{
+			name:    "global inference profile is preserved",
+			modelID: "global.anthropic.claude-fable-5-1",
+			region:  "us-east-1",
+			want:    "global.anthropic.claude-fable-5-1",
+		},
+		{
+			name:    "global inference profile is preserved outside us",
+			modelID: "global.anthropic.claude-fable-5-1",
+			region:  "eu-west-1",
+			want:    "global.anthropic.claude-fable-5-1",
+		},
+		{
+			name:    "apac profile is not double prefixed",
+			modelID: "apac.anthropic.claude-fable-5-1",
+			region:  "ap-southeast-2",
+			want:    "apac.anthropic.claude-fable-5-1",
+		},
+		{
+			name:    "cross geo profile is preserved",
+			modelID: "eu.anthropic.claude-fable-5-1",
+			region:  "us-east-1",
+			want:    "eu.anthropic.claude-fable-5-1",
+		},
+	}
+
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			t.Parallel()
+			require.Equal(t, test.want, bedrockPrefixModelWithRegion(test.modelID, test.region))
+		})
+	}
+}