diff --git a/packages/ai-provider-bridge/src/providers/__tests__/bedrock-provider.test.ts b/packages/ai-provider-bridge/src/providers/__tests__/bedrock-provider.test.ts
new file mode 100644
index 0000000..01df5e0
--- /dev/null
+++ b/packages/ai-provider-bridge/src/providers/__tests__/bedrock-provider.test.ts
@@ -0,0 +1,30 @@
+/*---------------------------------------------------------------------------------------------
+ *  Copyright (C) 2026 Posit Software, PBC. All rights reserved.
+ *--------------------------------------------------------------------------------------------*/
+
+import { describe, expect, it } from "vitest";
+
+import { getInferenceProfilePrefix } from "../bedrock-provider";
+
+describe("getInferenceProfilePrefix", () => {
+	it("uses the us-gov partition for AWS GovCloud regions", () => {
+		// Regression: GovCloud regions also start with "us-", so they must be
+		// matched before the general us- case or they'd get the commercial "us."
+		// prefix, whose inference profiles don't exist in GovCloud.
+		expect(getInferenceProfilePrefix("us-gov-west-1")).toBe("us-gov");
+		expect(getInferenceProfilePrefix("us-gov-east-1")).toBe("us-gov");
+	});
+
+	it("maps commercial regions to their partition prefixes", () => {
+		expect(getInferenceProfilePrefix("us-east-1")).toBe("us");
+		expect(getInferenceProfilePrefix("us-west-2")).toBe("us");
+		expect(getInferenceProfilePrefix("eu-west-1")).toBe("eu");
+		expect(getInferenceProfilePrefix("eu-central-1")).toBe("eu");
+		expect(getInferenceProfilePrefix("ap-northeast-1")).toBe("apac");
+		expect(getInferenceProfilePrefix("ap-southeast-1")).toBe("apac");
+	});
+
+	it("defaults unknown regions to us", () => {
+		expect(getInferenceProfilePrefix("ca-central-1")).toBe("us");
+	});
+});
diff --git a/packages/ai-provider-bridge/src/providers/bedrock-provider.ts b/packages/ai-provider-bridge/src/providers/bedrock-provider.ts
index 9aaf9b0..6b14918 100644
--- a/packages/ai-provider-bridge/src/providers/bedrock-provider.ts
+++ b/packages/ai-provider-bridge/src/providers/bedrock-provider.ts
@@ -58,11 +58,19 @@ const MODEL_CACHE_TTL = 60 * 60 * 1000;
  * Claude 4.x and newer models require inference profiles, not direct model IDs.
  *
  * AWS cross-region inference profiles use these prefixes:
+ * - us-gov.* for AWS GovCloud regions (us-gov-west-1, us-gov-east-1)
  * - us.* for US regions (us-east-1, us-west-2, etc.)
  * - eu.* for EU regions (eu-west-1, eu-central-1, etc.)
  * - apac.* for Asia-Pacific regions (ap-northeast-1, ap-southeast-1, etc.)
+ *
+ * GovCloud must be checked before the general `us-` case: `us-gov-west-1`
+ * also starts with `us-`, but its profiles live under the `us-gov` partition
+ * and the commercial `us.` profiles don't exist there.
  */
-function getInferenceProfilePrefix(region: string): string {
+export function getInferenceProfilePrefix(region: string): string {
+	if (region.startsWith("us-gov-")) {
+		return "us-gov";
+	}
 	if (region.startsWith("us-")) {
 		return "us";
 	}