From baa3bfa6d1ee3ab2b6d78d6e95341b4954761bb1 Mon Sep 17 00:00:00 2001
From: Christian Rocha <christian@rocha.is>
Date: Thu, 26 Mar 2026 14:34:11 -0400
Subject: [PATCH] fix(bedrock): inference profile prefix resolution
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Resolve Bedrock model IDs using AWS region-group prefixes with
AWS_DEFAULT_REGION fallback, preserve already-prefixed IDs, and default
to global for unmapped regions. Add tests to lock in mapping and
prefixing behavior.

💘 Generated with Crush

Assisted-by: GPT-5.3 Codex via Crush <crush@charm.land>
---
 providers/anthropic/anthropic_test.go | 30 ++++++++++++++++++++
 providers/anthropic/bedrock.go        | 40 +++++++++++++++++++++------
 2 files changed, 62 insertions(+), 8 deletions(-)

diff --git a/providers/anthropic/anthropic_test.go b/providers/anthropic/anthropic_test.go
index 4387a34faf7fe8900383e26859de13d306505664..5f7b1da16ac022ef949ce9fb3a5cf3c4450ec11a 100644
--- a/providers/anthropic/anthropic_test.go
+++ b/providers/anthropic/anthropic_test.go
@@ -1838,6 +1838,36 @@ func TestGenerate_BetaAPI(t *testing.T) {
 	})
 }
 
+func TestBedrockRegionPrefixing(t *testing.T) {
+	t.Run("uses us prefix when region is unset", func(t *testing.T) {
+		t.Setenv("AWS_REGION", "")
+		t.Setenv("AWS_DEFAULT_REGION", "")
+		require.Equal(t, "us.anthropic.claude-sonnet-4-5-20250929-v1:0", bedrockPrefixModelWithRegion("anthropic.claude-sonnet-4-5-20250929-v1:0"))
+	})
+
+	t.Run("uses AWS_DEFAULT_REGION when AWS_REGION is unset", func(t *testing.T) {
+		t.Setenv("AWS_REGION", "")
+		t.Setenv("AWS_DEFAULT_REGION", "eu-west-1")
+		require.Equal(t, "eu.anthropic.claude-sonnet-4-5-20250929-v1:0", bedrockPrefixModelWithRegion("anthropic.claude-sonnet-4-5-20250929-v1:0"))
+	})
+
+	t.Run("keeps already-prefixed model IDs", func(t *testing.T) {
+		t.Setenv("AWS_REGION", "us-east-1")
+		t.Setenv("AWS_DEFAULT_REGION", "")
+		require.Equal(t, "global.anthropic.claude-sonnet-4-5-20250929-v1:0", bedrockPrefixModelWithRegion("global.anthropic.claude-sonnet-4-5-20250929-v1:0"))
+	})
+
+	t.Run("maps known regions to profile prefixes", func(t *testing.T) {
+		require.Equal(t, "us", bedrockRegionPrefix("us-west-2"))
+		require.Equal(t, "us", bedrockRegionPrefix("ca-central-1"))
+		require.Equal(t, "eu", bedrockRegionPrefix("eu-central-1"))
+		require.Equal(t, "jp", bedrockRegionPrefix("ap-northeast-1"))
+		require.Equal(t, "au", bedrockRegionPrefix("ap-southeast-2"))
+		require.Equal(t, "global", bedrockRegionPrefix("ap-south-1"))
+		require.Equal(t, "global", bedrockRegionPrefix("sa-east-1"))
+	})
+}
+
 func TestStream_BetaAPI(t *testing.T) {
 	t.Parallel()
 
diff --git a/providers/anthropic/bedrock.go b/providers/anthropic/bedrock.go
index 8d9b94959210e57fde8fa594a67bfc8db8d27415..ff76fbf6bfffce061a4abd9432506a54a37de3ca 100644
--- a/providers/anthropic/bedrock.go
+++ b/providers/anthropic/bedrock.go
@@ -11,19 +11,43 @@ import (
 
 func bedrockBasicAuthConfig(apiKey string) aws.Config {
 	return aws.Config{
-		Region:                  cmp.Or(os.Getenv("AWS_REGION"), "us-east-1"),
+		Region:                  cmp.Or(awsRegion(), "us-east-1"),
 		BearerAuthTokenProvider: bearer.StaticTokenProvider{Token: bearer.Token{Value: apiKey}},
 	}
 }
 
 func bedrockPrefixModelWithRegion(modelID string) string {
-	region := os.Getenv("AWS_REGION")
-	if len(region) < 2 {
-		region = "us-east-1"
-	}
-	prefix := region[:2] + "."
-	if strings.HasPrefix(modelID, prefix) {
+	if hasBedrockInferenceProfilePrefix(modelID) {
 		return modelID
 	}
-	return prefix + modelID
+	region := cmp.Or(awsRegion(), "us-east-1")
+	return bedrockRegionPrefix(region) + "." + modelID
+}
+
+func awsRegion() string {
+	return cmp.Or(os.Getenv("AWS_REGION"), os.Getenv("AWS_DEFAULT_REGION"))
+}
+
+func bedrockRegionPrefix(region string) string {
+	switch {
+	case strings.HasPrefix(region, "us-") || region == "ca-central-1":
+		return "us"
+	case strings.HasPrefix(region, "eu-"):
+		return "eu"
+	case region == "ap-northeast-1":
+		return "jp"
+	case region == "ap-southeast-2":
+		return "au"
+	default:
+		return "global"
+	}
+}
+
+func hasBedrockInferenceProfilePrefix(modelID string) bool {
+	for _, prefix := range []string{"us.", "eu.", "jp.", "au.", "global."} {
+		if strings.HasPrefix(modelID, prefix) {
+			return true
+		}
+	}
+	return false
 }