diff --git a/src/cliproxy/tool-sanitization-proxy.ts b/src/cliproxy/tool-sanitization-proxy.ts
index 2c9e31c1..2ef0a572 100644
--- a/src/cliproxy/tool-sanitization-proxy.ts
+++ b/src/cliproxy/tool-sanitization-proxy.ts
@@ -22,7 +22,9 @@ import {
   extractProviderFromPathname,
   getDeniedModelIdReasonForProvider,
   normalizeModelIdForRouting,
+  stripCodexEffortSuffix,
 } from './model-id-normalizer';
+import { getModelMaxLevel } from './model-catalog';
 import { getCcsDir } from '../utils/config-manager';
 
 export interface ToolSanitizationProxyConfig {
@@ -44,6 +46,90 @@ function isRecord(value: unknown): value is Record<string, unknown> {
   return typeof value === 'object' && value !== null && !Array.isArray(value);
 }
 
+const GEMINI_UNSUPPORTED_TOOL_FIELDS = new Set([
+  'strict',
+  'input_examples',
+  'type',
+  'cache_control',
+  'defer_loading',
+]);
+
+const CODEX_UNSUPPORTED_TOOL_FIELDS = new Set(['cache_control', 'defer_loading']);
+
+function isKnownCodexModelId(model: string | undefined): boolean {
+  const normalizedModel = model?.trim().toLowerCase();
+  if (!normalizedModel) {
+    return false;
+  }
+
+  return getModelMaxLevel('codex', stripCodexEffortSuffix(normalizedModel)) !== undefined;
+}
+
+function getUnsupportedToolFields(
+  providerFromPath: string | null,
+  model: string | undefined
+): ReadonlySet<string> | null {
+  const normalizedProvider = providerFromPath?.trim().toLowerCase() ?? null;
+  const normalizedModel = model?.trim().toLowerCase();
+
+  if (
+    normalizedProvider === 'gemini' ||
+    normalizedProvider === 'gemini-cli' ||
+    (normalizedProvider === null && normalizedModel?.startsWith('gemini-'))
+  ) {
+    return GEMINI_UNSUPPORTED_TOOL_FIELDS;
+  }
+
+  if (
+    normalizedProvider === 'codex' ||
+    (normalizedProvider === null && isKnownCodexModelId(model))
+  ) {
+    return CODEX_UNSUPPORTED_TOOL_FIELDS;
+  }
+
+  return null;
+}
+
+function stripUnsupportedToolFields(
+  tools: Tool[],
+  unsupportedFields: ReadonlySet<string>
+): {
+  tools: Tool[];
+  removedByTool: Array<{ name: string; removed: string[] }>;
+  totalRemoved: number;
+} {
+  const removedByTool: Array<{ name: string; removed: string[] }> = [];
+  let totalRemoved = 0;
+
+  const sanitizedTools = tools.map((tool) => {
+    const sanitizedTool = { ...tool };
+    const removed: string[] = [];
+
+    for (const field of unsupportedFields) {
+      if (field in sanitizedTool) {
+        delete sanitizedTool[field];
+        removed.push(field);
+      }
+    }
+
+    if (removed.length > 0) {
+      removedByTool.push({
+        name: tool.name,
+        removed,
+      });
+      totalRemoved += removed.length;
+    }
+
+    return sanitizedTool;
+  });
+
+  return {
+    tools: sanitizedTools,
+    removedByTool,
+    totalRemoved,
+  };
+}
+
 export class ToolSanitizationProxy {
   private server: http.Server | null = null;
   private port: number | null = null;
@@ -184,6 +270,7 @@ export class ToolSanitizationProxy {
     const requestPath = req.url || '/';
     const upstreamBase = new URL(this.config.upstreamBaseUrl);
     const fullUpstreamUrl = new URL(requestPath, upstreamBase);
+    const providerFromPath = extractProviderFromPathname(fullUpstreamUrl.pathname);
 
     this.log(`${method} ${requestPath} → ${fullUpstreamUrl.href}`);
 
@@ -214,7 +301,6 @@ export class ToolSanitizationProxy {
       // Normalize dotted Claude model IDs for provider-compatible routing.
       let modifiedBody = parsed;
       if (isRecord(modifiedBody) && typeof modifiedBody.model === 'string') {
-        const providerFromPath = extractProviderFromPathname(fullUpstreamUrl.pathname);
         const deniedReason = getDeniedModelIdReasonForProvider(
           modifiedBody.model,
           providerFromPath
@@ -253,8 +339,32 @@ export class ToolSanitizationProxy {
           );
         }
 
+        let rewrittenTools = schemaResult.tools as Tool[];
+        const unsupportedToolFields =
+          isRecord(modifiedBody) && typeof modifiedBody.model === 'string'
+            ? getUnsupportedToolFields(providerFromPath, modifiedBody.model)
+            : getUnsupportedToolFields(providerFromPath, undefined);
+
+        if (unsupportedToolFields) {
+          const fieldResult = stripUnsupportedToolFields(rewrittenTools, unsupportedToolFields);
+
+          if (fieldResult.totalRemoved > 0) {
+            for (const entry of fieldResult.removedByTool) {
+              this.writeLog(
+                'warn',
+                `[tool-sanitization-proxy] Tool fields stripped for "${entry.name}" (${providerFromPath ?? 'model-routed'}): ${entry.removed.join(', ')}`
+              );
+            }
+            this.log(
+              `Stripped ${fieldResult.totalRemoved} unsupported top-level tool field(s) across ${fieldResult.removedByTool.length} tool(s)`
+            );
+          }
+
+          rewrittenTools = fieldResult.tools;
+        }
+
         // Step 2: Sanitize tool names (truncate to 64 chars for Gemini)
-        const sanitizedTools = mapper.registerTools(schemaResult.tools as Tool[]);
+        const sanitizedTools = mapper.registerTools(rewrittenTools);
         modifiedBody = { ...modifiedBody, tools: sanitizedTools };
 
         // Log sanitization warnings
diff --git a/tests/unit/cliproxy/tool-sanitization-proxy-integration.test.ts b/tests/unit/cliproxy/tool-sanitization-proxy-integration.test.ts
index 7f591232..8bb9a66a 100644
--- a/tests/unit/cliproxy/tool-sanitization-proxy-integration.test.ts
+++ b/tests/unit/cliproxy/tool-sanitization-proxy-integration.test.ts
@@ -326,6 +326,220 @@ describe('ToolSanitizationProxy Integration', () => {
       }
     });
 
+    it('strips Gemini-unsupported top-level tool fields while keeping schema sanitization', async () => {
+      const proxy = new ToolSanitizationProxy({
+        upstreamBaseUrl: `http://127.0.0.1:${mockUpstreamPort}`,
+      });
+      const port = await proxy.start();
+
+      try {
+        await fetch(`http://127.0.0.1:${port}/api/provider/gemini/v1/messages`, {
+          method: 'POST',
+          headers: { 'Content-Type': 'application/json' },
+          body: JSON.stringify({
+            model: 'gemini-2.5-pro',
+            tools: [
+              {
+                name: 'tool__with__duplicate__duplicate',
+                description: 'Test description',
+                strict: true,
+                input_examples: [{ command: 'ls -la' }],
+                type: 'custom',
+                cache_control: { type: 'ephemeral' },
+                defer_loading: true,
+                input_schema: {
+                  type: 'object',
+                  properties: {
+                    command: {
+                      type: 'string',
+                      examples: ['ls -la'],
+                    },
+                  },
+                },
+              },
+            ],
+          }),
+        });
+
+        const sentTools = (lastRequest!.body as Record<string, unknown>).tools as Array<
+          Record<string, unknown>
+        >;
+        expect(sentTools[0].name).toBe('tool__with__duplicate');
+        expect(sentTools[0].description).toBe('Test description');
+        expect(sentTools[0].strict).toBeUndefined();
+        expect(sentTools[0].input_examples).toBeUndefined();
+        expect(sentTools[0].type).toBeUndefined();
+        expect(sentTools[0].cache_control).toBeUndefined();
+        expect(sentTools[0].defer_loading).toBeUndefined();
+        expect(sentTools[0].input_schema).toEqual({
+          type: 'object',
+          properties: {
+            command: {
+              type: 'string',
+            },
+          },
+        });
+      } finally {
+        proxy.stop();
+      }
+    });
+
+    it('strips Codex-unsupported top-level tool fields before forwarding', async () => {
+      const proxy = new ToolSanitizationProxy({
+        upstreamBaseUrl: `http://127.0.0.1:${mockUpstreamPort}`,
+      });
+      const port = await proxy.start();
+
+      try {
+        await fetch(`http://127.0.0.1:${port}/api/provider/codex/v1/messages`, {
+          method: 'POST',
+          headers: { 'Content-Type': 'application/json' },
+          body: JSON.stringify({
+            model: 'gpt-5.3-codex',
+            tools: [
+              {
+                name: 'codex_tool',
+                description: 'Codex test',
+                cache_control: { type: 'ephemeral' },
+                defer_loading: true,
+                input_schema: {
+                  type: 'object',
+                  properties: {
+                    prompt: {
+                      type: 'string',
+                      examples: ['fix the failing test'],
+                    },
+                  },
+                },
+              },
+            ],
+          }),
+        });
+
+        const sentTools = (lastRequest!.body as Record<string, unknown>).tools as Array<
+          Record<string, unknown>
+        >;
+        expect(sentTools[0].name).toBe('codex_tool');
+        expect(sentTools[0].description).toBe('Codex test');
+        expect(sentTools[0].cache_control).toBeUndefined();
+        expect(sentTools[0].defer_loading).toBeUndefined();
+        expect(sentTools[0].input_schema).toEqual({
+          type: 'object',
+          properties: {
+            prompt: {
+              type: 'string',
+            },
+          },
+        });
+      } finally {
+        proxy.stop();
+      }
+    });
+
+    it('strips Codex-unsupported top-level tool fields on root model-routed requests', async () => {
+      const proxy = new ToolSanitizationProxy({
+        upstreamBaseUrl: `http://127.0.0.1:${mockUpstreamPort}`,
+      });
+      const port = await proxy.start();
+
+      try {
+        await fetch(`http://127.0.0.1:${port}/v1/messages`, {
+          method: 'POST',
+          headers: { 'Content-Type': 'application/json' },
+          body: JSON.stringify({
+            model: 'gpt-5.3-codex-xhigh',
+            tools: [
+              {
+                name: 'root_codex_tool',
+                description: 'Root-routed Codex test',
+                cache_control: { type: 'ephemeral' },
+                defer_loading: true,
+                input_schema: {
+                  type: 'object',
+                  properties: {
+                    prompt: {
+                      type: 'string',
+                      examples: ['fix the failing test'],
+                    },
+                  },
+                },
+              },
+            ],
+          }),
+        });
+
+        const sentTools = (lastRequest!.body as Record<string, unknown>).tools as Array<
+          Record<string, unknown>
+        >;
+        expect(sentTools[0].name).toBe('root_codex_tool');
+        expect(sentTools[0].description).toBe('Root-routed Codex test');
+        expect(sentTools[0].cache_control).toBeUndefined();
+        expect(sentTools[0].defer_loading).toBeUndefined();
+        expect(sentTools[0].input_schema).toEqual({
+          type: 'object',
+          properties: {
+            prompt: {
+              type: 'string',
+            },
+          },
+        });
+      } finally {
+        proxy.stop();
+      }
+    });
+
+    it('preserves top-level tool fields for non-target root routes', async () => {
+      const proxy = new ToolSanitizationProxy({
+        upstreamBaseUrl: `http://127.0.0.1:${mockUpstreamPort}`,
+      });
+      const port = await proxy.start();
+
+      try {
+        await fetch(`http://127.0.0.1:${port}/v1/messages`, {
+          method: 'POST',
+          headers: { 'Content-Type': 'application/json' },
+          body: JSON.stringify({
+            model: 'claude-sonnet-4-6',
+            tools: [
+              {
+                name: 'claude_tool__duplicate__duplicate',
+                description: 'Anthropic passthrough test',
+                cache_control: { type: 'ephemeral' },
+                defer_loading: true,
+                input_schema: {
+                  type: 'object',
+                  properties: {
+                    prompt: {
+                      type: 'string',
+                      examples: ['keep these top-level fields'],
+                    },
+                  },
+                },
+              },
+            ],
+          }),
+        });
+
+        const sentTools = (lastRequest!.body as Record<string, unknown>).tools as Array<
+          Record<string, unknown>
+        >;
+        expect(sentTools[0].name).toBe('claude_tool__duplicate');
+        expect(sentTools[0].description).toBe('Anthropic passthrough test');
+        expect(sentTools[0].cache_control).toEqual({ type: 'ephemeral' });
+        expect(sentTools[0].defer_loading).toBe(true);
+        expect(sentTools[0].input_schema).toEqual({
+          type: 'object',
+          properties: {
+            prompt: {
+              type: 'string',
+            },
+          },
+        });
+      } finally {
+        proxy.stop();
+      }
+    });
+
     it('preserves other tool properties during sanitization', async () => {
       const proxy = new ToolSanitizationProxy({
         upstreamBaseUrl: `http://127.0.0.1:${mockUpstreamPort}`,
@@ -341,7 +555,10 @@ describe('ToolSanitizationProxy Integration', () => {
               {
                 name: 'foo__bar__bar',
                 description: 'Test description',
-                input_schema: { type: 'object', properties: { x: { type: 'string' } } },
+                input_schema: {
+                  type: 'object',
+                  properties: { x: { type: 'string', examples: ['demo'] } },
+                },
               },
             ],
           }),