diff --git a/extensions/amazon-bedrock/stream.runtime.test.ts b/extensions/amazon-bedrock/stream.runtime.test.ts
index cf6d61a4d4d3..3bfda0bc1315 100644
--- a/extensions/amazon-bedrock/stream.runtime.test.ts
+++ b/extensions/amazon-bedrock/stream.runtime.test.ts
@@ -167,7 +167,22 @@ describe("Bedrock profile endpoint resolution", () => {
 });
 
 describe("Bedrock thinking effort mapping", () => {
-  it("caps max effort at high for Claude Sonnet 4.6", () => {
+  it("forces adaptive thinking for mandatory Claude models when callers omit reasoning", () => {
+    const model = bedrockModel({
+      id: "anthropic.claude-sonnet-4-6-v1:0",
+      name: "Claude Sonnet 4.6",
+      reasoning: true,
+    });
+    const options = testing.resolveSimpleBedrockOptions(model, {});
+
+    expect(options.reasoning).toBe("high");
+    expect(testing.buildAdditionalModelRequestFields(model, options)).toEqual({
+      thinking: { type: "adaptive", display: "summarized" },
+      output_config: { effort: "high" },
+    });
+  });
+
+  it("clamps max effort for Claude models without native max support", () => {
     expect(
       testing.mapThinkingLevelToEffort(
         bedrockModel({
diff --git a/extensions/amazon-bedrock/stream.runtime.ts b/extensions/amazon-bedrock/stream.runtime.ts
index 883eabc89353..6f517bf1354a 100644
--- a/extensions/amazon-bedrock/stream.runtime.ts
+++ b/extensions/amazon-bedrock/stream.runtime.ts
@@ -53,6 +53,7 @@ import {
   type ToolResultMessage,
 } from "openclaw/plugin-sdk/llm";
 import {
+  isClaudeAdaptiveThinkingDefaultModelId,
   resolveClaudeFable5ModelIdentity,
   resolveClaudeModelIdentity,
   supportsClaudeAdaptiveThinking,
@@ -351,29 +352,38 @@ export const streamSimpleBedrock: StreamFunction<"bedrock-converse-stream", Simp
   model: Model<"bedrock-converse-stream">,
   context: Context,
   options?: SimpleStreamOptions,
-) => {
+) => streamBedrock(model, context, resolveSimpleBedrockOptions(model, options));
+
+function resolveSimpleBedrockOptions(
+  model: Model<"bedrock-converse-stream">,
+  options?: SimpleStreamOptions,
+): BedrockOptions {
   const base = buildBaseOptions(model, options, undefined);
   if (usesClaudeFable5BedrockContract(model)) {
-    return streamBedrock(model, context, {
+    return {
       ...base,
       reasoning: options?.reasoning ?? "high",
       thinkingBudgets: options?.thinkingBudgets,
-    } satisfies BedrockOptions);
+    } satisfies BedrockOptions;
   }
   if (!options?.reasoning) {
-    return streamBedrock(model, context, {
+    const reasoning =
+      isAnthropicClaudeModel(model) && requiresMandatoryAdaptiveThinking(model)
+        ? "high"
+        : undefined;
+    return {
       ...base,
-      reasoning: undefined,
-    } satisfies BedrockOptions);
+      reasoning,
+    } satisfies BedrockOptions;
   }
 
   if (isAnthropicClaudeModel(model)) {
     if (supportsAdaptiveThinking(model)) {
-      return streamBedrock(model, context, {
+      return {
         ...base,
         reasoning: options.reasoning,
         thinkingBudgets: options.thinkingBudgets,
-      } satisfies BedrockOptions);
+      } satisfies BedrockOptions;
     }
 
     // Undefined means the caller did not request an output cap; let the helper use the model cap.
@@ -385,7 +395,7 @@ export const streamSimpleBedrock: StreamFunction<"bedrock-converse-stream", Simp
       options.thinkingBudgets,
     );
 
-    return streamBedrock(model, context, {
+    return {
       ...base,
       maxTokens: adjusted.maxTokens,
       reasoning: options.reasoning,
@@ -393,15 +403,15 @@ export const streamSimpleBedrock: StreamFunction<"bedrock-converse-stream", Simp
         ...options.thinkingBudgets,
         [clampReasoning(options.reasoning)!]: adjusted.thinkingBudget,
       },
-    } satisfies BedrockOptions);
+    } satisfies BedrockOptions;
   }
 
-  return streamBedrock(model, context, {
+  return {
     ...base,
     reasoning: options.reasoning,
     thinkingBudgets: options.thinkingBudgets,
-  } satisfies BedrockOptions);
-};
+  } satisfies BedrockOptions;
+}
 
 function handleContentBlockStart(
   event: ContentBlockStartEvent,
@@ -565,6 +575,14 @@ function supportsAdaptiveThinking(model: Model<"bedrock-converse-stream">): bool
   );
 }
 
+function requiresMandatoryAdaptiveThinking(model: Model<"bedrock-converse-stream">): boolean {
+  const profileModelId = resolveClaudeProfileNameModelId(model.name);
+  return (
+    isClaudeAdaptiveThinkingDefaultModelId(resolveClaudeModelIdentity(model)) ||
+    (profileModelId ? isClaudeAdaptiveThinkingDefaultModelId(profileModelId) : false)
+  );
+}
+
 function supportsNativeXhighEffort(model: Model<"bedrock-converse-stream">): boolean {
   const profileModelId = resolveClaudeProfileNameModelId(model.name);
   return (
@@ -1071,9 +1089,11 @@ function createImageBlock(mimeType: string, data: string) {
 
 /** Test-only hooks for Bedrock runtime conversion and endpoint policy. */
 export const testing = {
+  buildAdditionalModelRequestFields,
   convertMessages,
   getConfiguredBedrockRegion,
   hasConfiguredBedrockProfile,
   mapThinkingLevelToEffort,
+  resolveSimpleBedrockOptions,
   shouldUseExplicitBedrockEndpoint,
 };
diff --git a/extensions/microsoft-foundry/index.test.ts b/extensions/microsoft-foundry/index.test.ts
index b9ad29985728..6463be8c91b7 100644
--- a/extensions/microsoft-foundry/index.test.ts
+++ b/extensions/microsoft-foundry/index.test.ts
@@ -1307,11 +1307,11 @@ describe("microsoft-foundry plugin", () => {
     const provider = result.configPatch?.models?.providers?.["microsoft-foundry"] as
       | Record<string, unknown>
       | undefined;
-    expect(provider).toMatchObject({
-      authHeader: true,
-      apiKey: null,
-      headers: null,
-    });
+    expect(provider?.authHeader).toBe(true);
+    expect(Object.hasOwn(provider ?? {}, "apiKey")).toBe(true);
+    expect(Object.hasOwn(provider ?? {}, "headers")).toBe(true);
+    expect(provider?.apiKey).toBeUndefined();
+    expect(provider?.headers).toBeUndefined();
   });
 
   it.each([
diff --git a/extensions/microsoft-foundry/shared.ts b/extensions/microsoft-foundry/shared.ts
index 92fe24bc8423..34117f424b87 100644
--- a/extensions/microsoft-foundry/shared.ts
+++ b/extensions/microsoft-foundry/shared.ts
@@ -111,8 +111,8 @@ type FoundryModelCapabilities = {
 };
 
 type FoundryProviderConfigPatch = Omit<ModelProviderConfig, "apiKey" | "headers"> & {
-  apiKey?: SecretInput | null;
-  headers?: Record<string, SecretInput> | null;
+  apiKey?: SecretInput | undefined;
+  headers?: Record<string, SecretInput> | undefined;
 };
 
 function normalizeModelInput(input?: unknown): Array<"text" | "image"> {
@@ -481,7 +481,7 @@ function buildFoundryProviderConfig(
             : {}),
         }
       : isEntraIdAuth
-        ? { authHeader: true, apiKey: null, headers: null }
+        ? { authHeader: true, apiKey: undefined, headers: undefined }
         : {}),
     models: deployments.map((deployment) => {
       const capabilities = resolveFoundryModelCapabilities(
diff --git a/src/plugins/provider-auth-choice-helpers.test.ts b/src/plugins/provider-auth-choice-helpers.test.ts
index c84846a1bfcc..aa92cec2cde6 100644
--- a/src/plugins/provider-auth-choice-helpers.test.ts
+++ b/src/plugins/provider-auth-choice-helpers.test.ts
@@ -118,6 +118,43 @@ describe("applyProviderAuthConfigPatch", () => {
     });
   });
 
+  it("deletes provider auth fields marked undefined by auth patches", () => {
+    const baseLocal = {
+      models: {
+        providers: {
+          "microsoft-foundry": {
+            baseUrl: "https://example.services.ai.azure.com/openai/v1",
+            api: "anthropic-messages",
+            authHeader: false,
+            apiKey: "FOUNDRY_API_KEY",
+            headers: { "api-key": "FOUNDRY_API_KEY" },
+            models: [],
+          },
+        },
+      },
+    } satisfies OpenClawConfig;
+    const patch = {
+      models: {
+        providers: {
+          "microsoft-foundry": {
+            authHeader: true,
+            apiKey: undefined,
+            headers: undefined,
+          },
+        },
+      },
+    };
+
+    const next = applyProviderAuthConfigPatch(baseLocal, patch);
+    const provider = next.models?.providers?.["microsoft-foundry"] as
+      | Record<string, unknown>
+      | undefined;
+
+    expect(provider).toMatchObject({ authHeader: true });
+    expect(provider).not.toHaveProperty("apiKey");
+    expect(provider).not.toHaveProperty("headers");
+  });
+
   it("normalizes retired Google Gemini model refs from provider config patches", () => {
     const patch = {
       agents: {
diff --git a/src/plugins/provider-auth-choice-helpers.ts b/src/plugins/provider-auth-choice-helpers.ts
index c2137d27e444..1bc3e631cbd5 100644
--- a/src/plugins/provider-auth-choice-helpers.ts
+++ b/src/plugins/provider-auth-choice-helpers.ts
@@ -94,6 +94,22 @@ function mergeConfigPatch<T>(base: T, patch: unknown): T {
   return next as T;
 }
 
+function deleteUndefinedPatchLeaves<T>(target: T, patch: unknown): T {
+  if (!isPlainRecord(target) || !isPlainRecord(patch)) {
+    return target;
+  }
+
+  const targetRecord = target as Record<string, unknown>;
+  for (const [key, value] of Object.entries(patch)) {
+    if (value === undefined) {
+      delete targetRecord[key];
+      continue;
+    }
+    deleteUndefinedPatchLeaves(targetRecord[key], value);
+  }
+  return target;
+}
+
 function normalizeAgentModelConfigForWrite(value: unknown): unknown {
   if (typeof value === "string") {
     return normalizeAgentModelRefForConfig(value);
@@ -259,7 +275,9 @@ export function applyProviderAuthConfigPatch(
   patch: unknown,
   options?: { replaceDefaultModels?: boolean },
 ): OpenClawConfig {
-  const merged = normalizeConfigModelRefsForWrite(mergeConfigPatch(cfg, patch));
+  const merged = normalizeConfigModelRefsForWrite(
+    deleteUndefinedPatchLeaves(mergeConfigPatch(cfg, patch), patch),
+  );
   if (!options?.replaceDefaultModels || !isPlainRecord(patch)) {
     return merged;
   }