fix(cliproxy): strip Gemini-unsupported schema fields including "examples"

Replace permissive JSON Schema Draft-07 whitelist with strict
Gemini-compatible field set (22 fields). The "examples" field
in Claude Code tool schemas caused 400 errors from Gemini API.

Also strips other unsupported fields: $ref, $defs, oneOf, allOf,
additionalProperties, const, if/then/else, etc.

Safe change — sanitizer only runs for CLIProxy profiles (Gemini,
Codex, Antigravity), never for direct Anthropic API requests.

Closes #155

src/cliproxy/schema-sanitizer.ts

@@ -1,78 +1,60 @@
 /**
  * Schema Sanitizer
  *
- * Sanitizes MCP tool input_schema to remove non-standard JSON Schema properties
- * that Gemini/Vertex APIs reject.
+ * Sanitizes tool input_schema to only include fields supported by Google's
+ * Gemini/Vertex AI function_declarations Schema object.
  *
- * MCP servers (especially design tools) include UI-specific metadata in schemas:
- * - cornerRadius, fillColor, fontFamily, fontSize, fontWeight, gap, padding, etc.
+ * This sanitizer runs exclusively in the CLIProxy execution path (Gemini, Codex,
+ * Antigravity, etc.), never for direct Anthropic API requests.
  *
- * These are valid as MCP hints but invalid for strict JSON Schema validation.
+ * Gemini supports a subset of OpenAPI 3.0 schema — fields outside this subset
+ * (like "examples", "$ref", "oneOf", etc.) cause 400 errors.
+ *
+ * Reference: https://ai.google.dev/api/rest/v1beta/cachedContents#Schema
  */
 
-/** Valid JSON Schema Draft-07 keywords (used by Anthropic/Gemini APIs) */
-const VALID_JSON_SCHEMA_KEYWORDS = new Set([
+/**
+ * Fields supported by Gemini's function_declarations Schema object.
+ * Source: https://ai.google.dev/api/rest/v1beta/cachedContents#Schema
+ */
+const GEMINI_SUPPORTED_SCHEMA_FIELDS = new Set([
   // Core
   'type',
+  'format',
+  'title',
+  'description',
+  'nullable',
+  'example',
+  'default',
+
+  // Enum
+  'enum',
+
+  // Object
   'properties',
   'required',
+  'minProperties',
+  'maxProperties',
+
+  // Array
   'items',
-  'enum',
-  'const',
-  'default',
+  'minItems',
+  'maxItems',
 
   // String validation
   'minLength',
   'maxLength',
   'pattern',
-  'format',
 
   // Number validation
   'minimum',
   'maximum',
-  'exclusiveMinimum',
-  'exclusiveMaximum',
-  'multipleOf',
 
-  // Array validation
-  'minItems',
-  'maxItems',
-  'uniqueItems',
-  'contains',
-  'additionalItems',
-
-  // Object validation
-  'additionalProperties',
-  'patternProperties',
-  'minProperties',
-  'maxProperties',
-  'propertyNames',
-  'dependencies',
-
-  // Composition
-  'oneOf',
+  // Composition (only anyOf supported, NOT oneOf/allOf/not)
   'anyOf',
-  'allOf',
-  'not',
-  'if',
-  'then',
-  'else',
 
-  // Metadata (allowed by most APIs)
-  'title',
-  'description',
-  '$id',
-  '$schema',
-  '$ref',
-  '$defs',
-  'definitions',
-  '$comment',
-  'examples',
-  'readOnly',
-  'writeOnly',
-  'deprecated',
-  'contentMediaType',
-  'contentEncoding',
+  // Gemini-specific (non-standard OpenAPI)
+  'propertyOrdering',
 ]);
 
 /** Maximum recursion depth to prevent stack overflow */
@@ -88,15 +70,15 @@ export interface SchemaSanitizationResult {
 }
 
 /**
- * Check if a key is a valid JSON Schema keyword.
+ * Check if a key is supported by Gemini's Schema object.
  */
 function isValidSchemaKey(key: string): boolean {
-  return VALID_JSON_SCHEMA_KEYWORDS.has(key);
+  return GEMINI_SUPPORTED_SCHEMA_FIELDS.has(key);
 }
 
 /**
  * Recursively sanitize a JSON Schema object.
- * Removes non-standard properties while preserving valid schema structure.
+ * Removes fields unsupported by Gemini while preserving valid schema structure.
  *
  * @param schema The schema object to sanitize
  * @param path Current path for logging (e.g., "properties.foo.items")
@@ -167,115 +149,27 @@ function sanitizeSchemaRecursive(
       continue;
     }
 
-    if (key === 'additionalProperties' && typeof value === 'object') {
-      // Can be boolean or schema object
-      result[key] = sanitizeSchemaRecursive(value, keyPath, removedPaths, visited, depth + 1);
-      continue;
-    }
-
-    if (key === 'additionalItems' && typeof value === 'object' && value !== null) {
-      // Can be boolean or schema object (tuple validation)
-      result[key] = sanitizeSchemaRecursive(value, keyPath, removedPaths, visited, depth + 1);
-      continue;
-    }
-
-    // Composition keywords contain schema arrays
-    if (['oneOf', 'anyOf', 'allOf'].includes(key) && Array.isArray(value)) {
+    // anyOf is the only composition keyword Gemini supports
+    if (key === 'anyOf' && Array.isArray(value)) {
       result[key] = value.map((item, index) =>
         sanitizeSchemaRecursive(item, `${keyPath}[${index}]`, removedPaths, visited, depth + 1)
       );
       continue;
     }
 
-    if (key === 'not' && typeof value === 'object') {
-      result[key] = sanitizeSchemaRecursive(value, keyPath, removedPaths, visited, depth + 1);
-      continue;
-    }
-
-    if (key === 'propertyNames' && typeof value === 'object') {
-      result[key] = sanitizeSchemaRecursive(value, keyPath, removedPaths, visited, depth + 1);
-      continue;
-    }
-
-    // Conditional keywords
-    if (['if', 'then', 'else'].includes(key) && typeof value === 'object') {
-      result[key] = sanitizeSchemaRecursive(value, keyPath, removedPaths, visited, depth + 1);
-      continue;
-    }
-
-    if (key === 'contains' && typeof value === 'object') {
-      result[key] = sanitizeSchemaRecursive(value, keyPath, removedPaths, visited, depth + 1);
-      continue;
-    }
-
-    if (key === '$defs' || key === 'definitions') {
-      // Definition containers
-      if (typeof value === 'object' && value !== null) {
-        const sanitizedDefs: Record<string, unknown> = {};
-        for (const [defName, defSchema] of Object.entries(value as Record<string, unknown>)) {
-          sanitizedDefs[defName] = sanitizeSchemaRecursive(
-            defSchema,
-            `${keyPath}.${defName}`,
-            removedPaths,
-            visited,
-            depth + 1
-          );
-        }
-        result[key] = sanitizedDefs;
-        continue;
-      }
-    }
-
-    if (key === 'patternProperties') {
-      // Pattern property containers - preserve pattern keys and sanitize schema values
-      if (typeof value === 'object' && value !== null) {
-        const sanitizedPatterns: Record<string, unknown> = {};
-        for (const [pattern, patternSchema] of Object.entries(value as Record<string, unknown>)) {
-          sanitizedPatterns[pattern] = sanitizeSchemaRecursive(
-            patternSchema,
-            `${keyPath}.${pattern}`,
-            removedPaths,
-            visited,
-            depth + 1
-          );
-        }
-        result[key] = sanitizedPatterns;
-        continue;
-      }
-    }
-
-    if (key === 'dependencies') {
-      if (typeof value === 'object' && value !== null) {
-        const sanitizedDeps: Record<string, unknown> = {};
-        for (const [depName, depValue] of Object.entries(value as Record<string, unknown>)) {
-          // Schema dependencies need recursion, property dependencies (arrays) pass through
-          if (typeof depValue === 'object' && depValue !== null && !Array.isArray(depValue)) {
-            sanitizedDeps[depName] = sanitizeSchemaRecursive(
-              depValue,
-              `${keyPath}.${depName}`,
-              removedPaths,
-              visited,
-              depth + 1
-            );
-          } else {
-            sanitizedDeps[depName] = depValue;
-          }
-        }
-        result[key] = sanitizedDeps;
-        continue;
-      }
-    }
-
-    // Check if this is a valid JSON Schema keyword
+    // Check if this is a Gemini-supported field
     if (isValidSchemaKey(key)) {
-      // Recurse for nested objects that might contain schemas
-      if (typeof value === 'object' && value !== null && !Array.isArray(value)) {
+      // "example" and "default" hold arbitrary values, not nested schemas — pass through as-is
+      if (key === 'example' || key === 'default') {
+        result[key] = value;
+      } else if (typeof value === 'object' && value !== null && !Array.isArray(value)) {
+        // Recurse for nested objects that might contain schemas
         result[key] = sanitizeSchemaRecursive(value, keyPath, removedPaths, visited, depth + 1);
       } else {
         result[key] = value;
       }
     } else {
-      // Non-standard property - remove it
+      // Unsupported field — remove it
       removedPaths.push(keyPath);
     }
   }
@@ -284,7 +178,7 @@ function sanitizeSchemaRecursive(
 }
 
 /**
- * Sanitize an input_schema object, removing non-standard JSON Schema properties.
+ * Sanitize an input_schema object, removing fields unsupported by Gemini.
  *
  * @param inputSchema The tool's input_schema object
  * @returns Sanitization result with cleaned schema and metadata

tests/unit/cliproxy/schema-sanitizer.test.ts

@@ -1,14 +1,15 @@
 /**
  * Schema Sanitizer Unit Tests
  *
- * Tests for MCP tool input_schema sanitization.
+ * Tests for Gemini-compatible tool input_schema sanitization.
+ * Verifies that only Gemini-supported fields are preserved.
  */
 
 import { describe, expect, test } from 'bun:test';
 import { sanitizeInputSchema, sanitizeToolSchemas } from '../../../dist/cliproxy/schema-sanitizer.js';
 
 describe('sanitizeInputSchema', () => {
-  test('preserves valid JSON Schema properties', () => {
+  test('preserves Gemini-supported properties', () => {
     const schema = {
       type: 'object',
       properties: {
@@ -110,10 +111,10 @@ describe('sanitizeInputSchema', () => {
     });
   });
 
-  test('handles oneOf/anyOf/allOf with nested schemas', () => {
+  test('preserves anyOf and sanitizes nested schemas', () => {
     const schema = {
       type: 'object',
-      oneOf: [
+      anyOf: [
         { type: 'string', customProp: 'remove' },
         { type: 'number', anotherCustom: 123 },
       ],
@@ -124,10 +125,25 @@ describe('sanitizeInputSchema', () => {
     expect(result.removedCount).toBe(2);
     expect(result.schema).toEqual({
       type: 'object',
-      oneOf: [{ type: 'string' }, { type: 'number' }],
+      anyOf: [{ type: 'string' }, { type: 'number' }],
     });
   });
 
+  test('removes oneOf and allOf (not supported by Gemini)', () => {
+    const schema = {
+      type: 'object',
+      oneOf: [{ type: 'string' }, { type: 'number' }],
+      allOf: [{ required: ['name'] }],
+    };
+
+    const result = sanitizeInputSchema(schema);
+
+    expect(result.removedCount).toBe(2);
+    expect(result.removedPaths).toContain('oneOf');
+    expect(result.removedPaths).toContain('allOf');
+    expect(result.schema).toEqual({ type: 'object' });
+  });
+
   test('handles deeply nested structures', () => {
     const schema = {
       type: 'object',
@@ -153,51 +169,52 @@ describe('sanitizeInputSchema', () => {
     expect(result.removedPaths).toContain('properties.level1.properties.level2.uiHint');
   });
 
-  test('preserves $defs and definitions', () => {
+  test('strips "examples" field (issue #155)', () => {
     const schema = {
       type: 'object',
-      $defs: {
-        address: {
-          type: 'object',
-          customUI: 'remove',
-          properties: {
-            street: { type: 'string' },
-          },
-        },
-      },
       properties: {
-        home: { $ref: '#/$defs/address' },
+        command: {
+          type: 'string',
+          description: 'The command to execute',
+          examples: ['ls -la', 'git status'],
+        },
+        timeout: {
+          type: 'number',
+          description: 'Timeout in ms',
+          examples: [5000, 10000],
+        },
       },
     };
 
     const result = sanitizeInputSchema(schema);
 
-    expect(result.removedCount).toBe(1);
-    expect(result.removedPaths).toContain('$defs.address.customUI');
+    expect(result.removedCount).toBe(2);
+    expect(result.removedPaths).toContain('properties.command.examples');
+    expect(result.removedPaths).toContain('properties.timeout.examples');
     expect(result.schema).toEqual({
       type: 'object',
-      $defs: {
-        address: {
-          type: 'object',
-          properties: {
-            street: { type: 'string' },
-          },
-        },
-      },
       properties: {
-        home: { $ref: '#/$defs/address' },
+        command: { type: 'string', description: 'The command to execute' },
+        timeout: { type: 'number', description: 'Timeout in ms' },
       },
     });
   });
 
-  test('handles empty schema', () => {
-    const result = sanitizeInputSchema({});
+  test('keeps "example" (singular) but strips "examples" (plural)', () => {
+    const schema = {
+      type: 'string',
+      example: 'hello',
+      examples: ['hello', 'world'],
+    };
 
-    expect(result.removedCount).toBe(0);
-    expect(result.schema).toEqual({});
+    const result = sanitizeInputSchema(schema);
+
+    expect(result.removedCount).toBe(1);
+    expect(result.removedPaths).toContain('examples');
+    expect(result.schema).toEqual({ type: 'string', example: 'hello' });
   });
 
-  test('preserves all standard metadata keywords', () => {
+  test('strips Gemini-unsupported JSON Schema metadata fields', () => {
     const schema = {
       $id: 'https://example.com/schema',
       $schema: 'https://json-schema.org/draft-07/schema#',
@@ -212,95 +229,121 @@ describe('sanitizeInputSchema', () => {
 
     const result = sanitizeInputSchema(schema);
 
-    expect(result.removedCount).toBe(0);
-    expect(result.schema).toEqual(schema);
+    // $id, $schema, examples, deprecated, readOnly, $comment = 6 removed
+    expect(result.removedCount).toBe(6);
+    expect(result.removedPaths).toContain('$id');
+    expect(result.removedPaths).toContain('$schema');
+    expect(result.removedPaths).toContain('examples');
+    expect(result.removedPaths).toContain('deprecated');
+    expect(result.removedPaths).toContain('readOnly');
+    expect(result.removedPaths).toContain('$comment');
+    expect(result.schema).toEqual({
+      title: 'Test Schema',
+      description: 'A test schema',
+      type: 'string',
+    });
   });
 
-  test('preserves additionalItems keyword', () => {
-    const schema = {
-      type: 'array',
-      items: [{ type: 'string' }],
-      additionalItems: { type: 'boolean' },
-    };
-    const result = sanitizeInputSchema(schema);
-    expect(result.removedCount).toBe(0);
-    expect(result.schema.additionalItems).toEqual({ type: 'boolean' });
-  });
-
-  test('sanitizes nested schemas in additionalItems', () => {
-    const schema = {
-      type: 'array',
-      items: [{ type: 'string' }],
-      additionalItems: { type: 'boolean', customProp: 'remove' },
-    };
-    const result = sanitizeInputSchema(schema);
-    expect(result.removedCount).toBe(1);
-    expect(result.removedPaths).toContain('additionalItems.customProp');
-    expect(result.schema.additionalItems).toEqual({ type: 'boolean' });
-  });
-
-  test('preserves if/then/else and sanitizes nested schemas', () => {
-    const schema = {
-      if: { properties: { type: { const: 'foo' } }, uiHint: 'remove' },
-      then: { required: ['foo'], badProp: 123 },
-      else: { required: ['bar'] },
-    };
-    const result = sanitizeInputSchema(schema);
-    expect(result.removedCount).toBe(2);
-    expect(result.schema.if).toEqual({ properties: { type: { const: 'foo' } } });
-    expect(result.schema.then).toEqual({ required: ['foo'] });
-  });
-
-  test('preserves patternProperties keyword and sanitizes nested schemas', () => {
+  test('strips $defs, $ref, definitions (not supported by Gemini)', () => {
     const schema = {
       type: 'object',
-      patternProperties: { '^S_': { type: 'string', customProp: 'remove' } },
-    };
-    const result = sanitizeInputSchema(schema);
-    expect(result.removedCount).toBe(1);
-    expect(result.removedPaths).toContain('patternProperties.^S_.customProp');
-    expect(result.schema.patternProperties).toEqual({ '^S_': { type: 'string' } });
-  });
-
-  test('preserves contains keyword and sanitizes nested schema', () => {
-    const schema = {
-      type: 'array',
-      contains: { type: 'number', minimum: 5, customProp: 'remove' },
-    };
-    const result = sanitizeInputSchema(schema);
-    expect(result.removedCount).toBe(1);
-    expect(result.removedPaths).toContain('contains.customProp');
-    expect(result.schema.contains).toEqual({ type: 'number', minimum: 5 });
-  });
-
-  test('preserves propertyNames keyword and sanitizes nested schema', () => {
-    const schema = {
-      type: 'object',
-      propertyNames: { type: 'string', pattern: '^[a-z]+$', customProp: 'remove' },
-    };
-    const result = sanitizeInputSchema(schema);
-    expect(result.removedCount).toBe(1);
-    expect(result.removedPaths).toContain('propertyNames.customProp');
-    expect(result.schema.propertyNames).toEqual({ type: 'string', pattern: '^[a-z]+$' });
-  });
-
-  test('handles dependencies with both property and schema dependencies', () => {
-    const schema = {
-      type: 'object',
-      dependencies: {
-        bar: ['foo'], // property dependency (array) - pass through
-        baz: { properties: { qux: { type: 'string' } }, customProp: 'remove' }, // schema dependency
+      $defs: {
+        address: {
+          type: 'object',
+          properties: { street: { type: 'string' } },
+        },
+      },
+      properties: {
+        home: { $ref: '#/$defs/address' },
       },
     };
+
     const result = sanitizeInputSchema(schema);
-    expect(result.removedCount).toBe(1);
-    expect(result.removedPaths).toContain('dependencies.baz.customProp');
-    expect(result.schema.dependencies).toEqual({
-      bar: ['foo'],
-      baz: { properties: { qux: { type: 'string' } } },
+
+    expect(result.removedCount).toBe(2);
+    expect(result.removedPaths).toContain('$defs');
+    expect(result.removedPaths).toContain('properties.home.$ref');
+    expect(result.schema).toEqual({
+      type: 'object',
+      properties: {
+        home: {},
+      },
     });
   });
 
+  test('strips additionalProperties (not supported by Gemini)', () => {
+    const schema = {
+      type: 'object',
+      properties: { name: { type: 'string' } },
+      additionalProperties: false,
+    };
+
+    const result = sanitizeInputSchema(schema);
+
+    expect(result.removedCount).toBe(1);
+    expect(result.removedPaths).toContain('additionalProperties');
+  });
+
+  test('strips const, not, if/then/else (not supported by Gemini)', () => {
+    const schema = {
+      type: 'object',
+      const: 'fixed',
+      not: { type: 'number' },
+      if: { properties: { type: { const: 'foo' } } },
+      then: { required: ['foo'] },
+      else: { required: ['bar'] },
+    };
+
+    const result = sanitizeInputSchema(schema);
+
+    expect(result.removedCount).toBe(5);
+    expect(result.removedPaths).toContain('const');
+    expect(result.removedPaths).toContain('not');
+    expect(result.removedPaths).toContain('if');
+    expect(result.removedPaths).toContain('then');
+    expect(result.removedPaths).toContain('else');
+    expect(result.schema).toEqual({ type: 'object' });
+  });
+
+  test('preserves all Gemini-supported fields', () => {
+    const schema = {
+      type: 'object',
+      format: 'date',
+      title: 'Test',
+      description: 'A test',
+      nullable: true,
+      example: { name: 'test' },
+      default: {},
+      enum: ['a', 'b'],
+      properties: { name: { type: 'string' } },
+      required: ['name'],
+      minProperties: 1,
+      maxProperties: 10,
+      items: { type: 'string' },
+      minItems: 0,
+      maxItems: 100,
+      minLength: 1,
+      maxLength: 255,
+      pattern: '^[a-z]+$',
+      minimum: 0,
+      maximum: 100,
+      anyOf: [{ type: 'string' }],
+      propertyOrdering: ['name'],
+    };
+
+    const result = sanitizeInputSchema(schema);
+
+    expect(result.removedCount).toBe(0);
+    expect(result.removedPaths).toEqual([]);
+  });
+
+  test('handles empty schema', () => {
+    const result = sanitizeInputSchema({});
+
+    expect(result.removedCount).toBe(0);
+    expect(result.schema).toEqual({});
+  });
+
   test('handles null input gracefully', () => {
     const result = sanitizeInputSchema(null as any);
     expect(result.schema).toBeNull();
@@ -361,6 +404,70 @@ describe('sanitizeToolSchemas', () => {
     });
   });
 
+  test('strips examples from Claude Code tool schemas (issue #155)', () => {
+    const tools = [
+      {
+        name: 'Bash',
+        input_schema: {
+          type: 'object',
+          properties: {
+            command: {
+              type: 'string',
+              description: 'The command to execute',
+              examples: ['ls -la', 'git status', 'npm install'],
+            },
+            timeout: {
+              type: 'number',
+              description: 'Timeout in ms',
+              examples: [5000, 30000],
+            },
+          },
+          required: ['command'],
+        },
+      },
+      {
+        name: 'Read',
+        input_schema: {
+          type: 'object',
+          properties: {
+            file_path: {
+              type: 'string',
+              description: 'File path to read',
+              examples: ['/src/index.ts', '/package.json'],
+            },
+          },
+          required: ['file_path'],
+        },
+      },
+    ];
+
+    const result = sanitizeToolSchemas(tools);
+
+    expect(result.totalRemoved).toBe(3);
+    expect(result.removedByTool).toHaveLength(2);
+
+    // Verify examples stripped from Bash tool
+    const bashTool = result.tools.find((t) => t.name === 'Bash');
+    expect(bashTool?.input_schema).toEqual({
+      type: 'object',
+      properties: {
+        command: { type: 'string', description: 'The command to execute' },
+        timeout: { type: 'number', description: 'Timeout in ms' },
+      },
+      required: ['command'],
+    });
+
+    // Verify examples stripped from Read tool
+    const readTool = result.tools.find((t) => t.name === 'Read');
+    expect(readTool?.input_schema).toEqual({
+      type: 'object',
+      properties: {
+        file_path: { type: 'string', description: 'File path to read' },
+      },
+      required: ['file_path'],
+    });
+  });
+
   test('handles tools without input_schema', () => {
     const tools = [
       { name: 'simple_tool', description: 'No schema' },