diff --git a/CLAUDE.md b/CLAUDE.md
index b1ae463..eed2a46 100644
--- a/CLAUDE.md
+++ b/CLAUDE.md
@@ -4,7 +4,7 @@ This file provides guidance to Claude Code (claude.ai/code) when working with co
 
 ## Project Overview
 
-Antigravity Claude Proxy is a Node.js proxy server that exposes an Anthropic-compatible API backed by Antigravity's Cloud Code service. It enables using Claude models (`claude-sonnet-4-5-thinking`, `claude-opus-4-5-thinking`) with Claude Code CLI.
+Antigravity Claude Proxy is a Node.js proxy server that exposes an Anthropic-compatible API backed by Antigravity's Cloud Code service. It enables using Claude models (`claude-sonnet-4-5-thinking`, `claude-opus-4-5-thinking`) and Gemini models (`gemini-3-flash`, `gemini-3-pro-low`, `gemini-3-pro-high`) with Claude Code CLI.
 
 The proxy translates requests from Anthropic Messages API format → Google Generative AI format → Antigravity Cloud Code API, then converts responses back to Anthropic format with full thinking/streaming support.
 
@@ -80,11 +80,17 @@ Claude Code CLI → Express Server (server.js) → CloudCode Client → Antigrav
 
 **Constants:** All configuration values are centralized in `src/constants.js`:
 - API endpoints and headers
-- Model mappings
+- Model mappings and model family detection (`getModelFamily()`, `isThinkingModel()`)
 - OAuth configuration
 - Rate limit thresholds
 - Thinking model settings
 
+**Model Family Handling:**
+- `getModelFamily(model)` returns `'claude'` or `'gemini'` based on model name
+- Claude models use `signature` field on thinking blocks
+- Gemini models use `thoughtSignature` field on functionCall parts
+- When Claude Code strips `thoughtSignature`, the proxy uses Google's `skip_thought_signature_validator` sentinel value
+
 **Error Handling:** Use custom error classes from `src/errors.js`:
 - `RateLimitError` - 429/RESOURCE_EXHAUSTED errors
 - `AuthError` - Authentication failures
diff --git a/README.md b/README.md
index 4eefebe..b744cb0 100644
--- a/README.md
+++ b/README.md
@@ -6,7 +6,7 @@
 
 <a href="https://buymeacoffee.com/badrinarayanans" target="_blank"><img src="https://cdn.buymeacoffee.com/buttons/v2/default-yellow.png" alt="Buy Me A Coffee" height="50"></a>
 
-A proxy server that exposes an **Anthropic-compatible API** backed by **Antigravity's Cloud Code**, letting you use Claude models like sonnet and opus with **Claude Code CLI**.
+A proxy server that exposes an **Anthropic-compatible API** backed by **Antigravity's Cloud Code**, letting you use Claude and Gemini models with **Claude Code CLI**.
 
 ![Antigravity Claude Proxy Banner](images/banner.png)
 
@@ -145,7 +145,23 @@ Add this configuration:
     "ANTHROPIC_DEFAULT_OPUS_MODEL": "claude-opus-4-5-thinking",
     "ANTHROPIC_DEFAULT_SONNET_MODEL": "claude-sonnet-4-5-thinking",
     "ANTHROPIC_DEFAULT_HAIKU_MODEL": "claude-sonnet-4-5",
-    "CLAUDE_CODE_SUBAGENT_MODEL": "claude-opus-4-5-thinking"
+    "CLAUDE_CODE_SUBAGENT_MODEL": "claude-sonnet-4-5"
+  }
+}
+```
+
+Or to use Gemini models:
+
+```json
+{
+  "env": {
+    "ANTHROPIC_AUTH_TOKEN": "test",
+    "ANTHROPIC_BASE_URL": "http://localhost:8080",
+    "ANTHROPIC_MODEL": "gemini-3-pro-high",
+    "ANTHROPIC_DEFAULT_OPUS_MODEL": "gemini-3-pro-high",
+    "ANTHROPIC_DEFAULT_SONNET_MODEL": "gemini-3-flash",
+    "ANTHROPIC_DEFAULT_HAIKU_MODEL": "gemini-3-flash",
+    "CLAUDE_CODE_SUBAGENT_MODEL": "gemini-2.5-flash-lite"
   }
 }
 ```
@@ -164,6 +180,8 @@ claude
 
 ## Available Models
 
+### Claude Models
+
 | Model ID | Description |
 |----------|-------------|
 | `claude-sonnet-4-5-thinking` | Claude Sonnet 4.5 with extended thinking |
@@ -174,6 +192,16 @@ Standard Anthropic model names are automatically mapped:
 - `claude-sonnet-4-5-20250514` → `claude-sonnet-4-5-thinking`
 - `claude-opus-4-5-20250514` → `claude-opus-4-5-thinking`
 
+### Gemini Models
+
+| Model ID | Description |
+|----------|-------------|
+| `gemini-3-flash` | Gemini 3 Flash with thinking |
+| `gemini-3-pro-low` | Gemini 3 Pro Low with thinking |
+| `gemini-3-pro-high` | Gemini 3 Pro High with thinking |
+
+Gemini models include full thinking support with `thoughtSignature` handling for multi-turn conversations.
+
 ---
 
 ## Multi-Account Load Balancing
diff --git a/src/cloudcode-client.js b/src/cloudcode-client.js
index 98f5e5b..b75a2dc 100644
--- a/src/cloudcode-client.js
+++ b/src/cloudcode-client.js
@@ -15,7 +15,9 @@ import {
     ANTIGRAVITY_HEADERS,
     MAX_RETRIES,
     MAX_WAIT_BEFORE_ERROR_MS,
-    MIN_SIGNATURE_LENGTH
+    MIN_SIGNATURE_LENGTH,
+    getModelFamily,
+    isThinkingModel
 } from './constants.js';
 import {
     convertAnthropicToGoogle,
@@ -244,9 +246,10 @@ function buildHeaders(token, model, accept = 'application/json') {
         ...ANTIGRAVITY_HEADERS
     };
 
-    // Add interleaved thinking header for Claude thinking models
-    const isThinkingModel = model.toLowerCase().includes('claude') && model.toLowerCase().includes('thinking');
-    if (isThinkingModel) {
+    const modelFamily = getModelFamily(model);
+
+    // Add interleaved thinking header only for Claude thinking models
+    if (modelFamily === 'claude' && isThinkingModel(model)) {
         headers['anthropic-beta'] = 'interleaved-thinking-2025-05-14';
     }
 
@@ -272,7 +275,7 @@ function buildHeaders(token, model, accept = 'application/json') {
  */
 export async function sendMessage(anthropicRequest, accountManager) {
     const model = anthropicRequest.model;
-    const isThinkingModel = model.toLowerCase().includes('claude') && model.toLowerCase().includes('thinking');
+    const isThinking = isThinkingModel(model);
 
     // Retry loop with account failover
     // Ensure we try at least as many times as there are accounts to cycle through everyone
@@ -330,13 +333,13 @@ export async function sendMessage(anthropicRequest, accountManager) {
             let lastError = null;
             for (const endpoint of ANTIGRAVITY_ENDPOINT_FALLBACKS) {
                 try {
-                    const url = isThinkingModel
+                    const url = isThinking
                         ? `${endpoint}/v1internal:streamGenerateContent?alt=sse`
                         : `${endpoint}/v1internal:generateContent`;
 
                     const response = await fetch(url, {
                         method: 'POST',
-                        headers: buildHeaders(token, model, isThinkingModel ? 'text/event-stream' : 'application/json'),
+                        headers: buildHeaders(token, model, isThinking ? 'text/event-stream' : 'application/json'),
                         body: JSON.stringify(payload)
                     });
 
@@ -370,7 +373,7 @@ export async function sendMessage(anthropicRequest, accountManager) {
                     }
 
                     // For thinking models, parse SSE and accumulate all parts
-                    if (isThinkingModel) {
+                    if (isThinking) {
                         return await parseThinkingSSEResponse(response, anthropicRequest.model);
                     }
 
@@ -812,6 +815,10 @@ async function* streamSSEResponse(response, originalModel) {
 
                     } else if (part.functionCall) {
                         // Handle tool use
+                        // For Gemini 3+, capture thoughtSignature from the functionCall part
+                        // The signature is a sibling to functionCall, not inside it
+                        const functionCallSignature = part.thoughtSignature || '';
+
                         if (currentBlockType === 'thinking' && currentThinkingSignature) {
                             yield {
                                 type: 'content_block_delta',
@@ -829,15 +836,24 @@ async function* streamSSEResponse(response, originalModel) {
 
                         const toolId = part.functionCall.id || `toolu_${crypto.randomBytes(12).toString('hex')}`;
 
+                        // For Gemini, include the thoughtSignature in the tool_use block
+                        // so it can be sent back in subsequent requests
+                        const toolUseBlock = {
+                            type: 'tool_use',
+                            id: toolId,
+                            name: part.functionCall.name,
+                            input: {}
+                        };
+
+                        // Store the signature in the tool_use block for later retrieval
+                        if (functionCallSignature && functionCallSignature.length >= MIN_SIGNATURE_LENGTH) {
+                            toolUseBlock.thoughtSignature = functionCallSignature;
+                        }
+
                         yield {
                             type: 'content_block_start',
                             index: blockIndex,
-                            content_block: {
-                                type: 'tool_use',
-                                id: toolId,
-                                name: part.functionCall.name,
-                                input: {}
-                            }
+                            content_block: toolUseBlock
                         };
 
                         yield {
diff --git a/src/constants.js b/src/constants.js
index 1358ea3..8806531 100644
--- a/src/constants.js
+++ b/src/constants.js
@@ -84,6 +84,40 @@ export const MAX_WAIT_BEFORE_ERROR_MS = 120000; // 2 minutes - throw error if wa
 // Thinking model constants
 export const MIN_SIGNATURE_LENGTH = 50; // Minimum valid thinking signature length
 
+// Gemini-specific limits
+export const GEMINI_MAX_OUTPUT_TOKENS = 16384;
+
+/**
+ * Get the model family from model name (dynamic detection, no hardcoded list).
+ * @param {string} modelName - The model name from the request
+ * @returns {'claude' | 'gemini' | 'unknown'} The model family
+ */
+export function getModelFamily(modelName) {
+    const lower = (modelName || '').toLowerCase();
+    if (lower.includes('claude')) return 'claude';
+    if (lower.includes('gemini')) return 'gemini';
+    return 'unknown';
+}
+
+/**
+ * Check if a model supports thinking/reasoning output.
+ * @param {string} modelName - The model name from the request
+ * @returns {boolean} True if the model supports thinking blocks
+ */
+export function isThinkingModel(modelName) {
+    const lower = (modelName || '').toLowerCase();
+    // Claude thinking models have "thinking" in the name
+    if (lower.includes('claude') && lower.includes('thinking')) return true;
+    // Gemini thinking models: explicit "thinking" in name, OR gemini version 3+
+    if (lower.includes('gemini')) {
+        if (lower.includes('thinking')) return true;
+        // Check for gemini-3 or higher (e.g., gemini-3, gemini-3.5, gemini-4, etc.)
+        const versionMatch = lower.match(/gemini-(\d+)/);
+        if (versionMatch && parseInt(versionMatch[1], 10) >= 3) return true;
+    }
+    return false;
+}
+
 // Google OAuth configuration (from opencode-antigravity-auth)
 export const OAUTH_CONFIG = {
     clientId: '1071006060591-tmhssin2h21lcre235vtolojh4g403ep.apps.googleusercontent.com',
@@ -117,6 +151,9 @@ export default {
     MAX_ACCOUNTS,
     MAX_WAIT_BEFORE_ERROR_MS,
     MIN_SIGNATURE_LENGTH,
+    GEMINI_MAX_OUTPUT_TOKENS,
+    getModelFamily,
+    isThinkingModel,
     OAUTH_CONFIG,
     OAUTH_REDIRECT_URI
 };
diff --git a/src/format-converter.js b/src/format-converter.js
index 2f274ab..3551298 100644
--- a/src/format-converter.js
+++ b/src/format-converter.js
@@ -9,9 +9,20 @@
 
 import crypto from 'crypto';
 import {
-    MIN_SIGNATURE_LENGTH
+    MIN_SIGNATURE_LENGTH,
+    GEMINI_MAX_OUTPUT_TOKENS,
+    getModelFamily,
+    isThinkingModel
 } from './constants.js';
 
+/**
+ * Sentinel value to skip thought signature validation for Gemini models.
+ * Per Google documentation, this value can be used when Claude Code strips
+ * the thoughtSignature field from tool_use blocks in multi-turn requests.
+ * See: https://ai.google.dev/gemini-api/docs/thought-signatures
+ */
+const GEMINI_SKIP_SIGNATURE = 'skip_thought_signature_validator';
+
 /**
  * Check if a part is a thinking block
  * @param {Object} part - Content part to check
@@ -272,7 +283,7 @@ export function reorderAssistantContent(content) {
 /**
  * Convert Anthropic message content to Google Generative AI parts
  */
-function convertContentToParts(content, isClaudeModel = false) {
+function convertContentToParts(content, isClaudeModel = false, isGeminiModel = false) {
     if (typeof content === 'string') {
         return [{ text: content }];
     }
@@ -337,7 +348,19 @@ function convertContentToParts(content, isClaudeModel = false) {
                 functionCall.id = block.id;
             }
 
-            parts.push({ functionCall });
+            // Build the part with functionCall
+            const part = { functionCall };
+
+            // For Gemini models, include thoughtSignature at the part level
+            // This is required by Gemini 3+ for tool calls to work correctly
+            if (isGeminiModel) {
+                // Use thoughtSignature from the block if Claude Code preserved it
+                // Otherwise, use the sentinel value to skip validation (Claude Code strips non-standard fields)
+                // See: https://ai.google.dev/gemini-api/docs/thought-signatures
+                part.thoughtSignature = block.thoughtSignature || GEMINI_SKIP_SIGNATURE;
+            }
+
+            parts.push(part);
         } else if (block.type === 'tool_result') {
             // Convert tool_result to functionResponse (Google format)
             let responseContent = block.content;
@@ -400,8 +423,10 @@ function convertRole(role) {
 export function convertAnthropicToGoogle(anthropicRequest) {
     const { messages, system, max_tokens, temperature, top_p, top_k, stop_sequences, tools, tool_choice, thinking } = anthropicRequest;
     const modelName = anthropicRequest.model || '';
-    const isClaudeModel = modelName.toLowerCase().includes('claude');
-    const isClaudeThinkingModel = isClaudeModel && modelName.toLowerCase().includes('thinking');
+    const modelFamily = getModelFamily(modelName);
+    const isClaudeModel = modelFamily === 'claude';
+    const isGeminiModel = modelFamily === 'gemini';
+    const isThinking = isThinkingModel(modelName);
 
     const googleRequest = {
         contents: [],
@@ -429,7 +454,7 @@ export function convertAnthropicToGoogle(anthropicRequest) {
     }
 
     // Add interleaved thinking hint for Claude thinking models with tools
-    if (isClaudeThinkingModel && tools && tools.length > 0) {
+    if (isClaudeModel && isThinking && tools && tools.length > 0) {
         const hint = 'Interleaved thinking is enabled. You may think between tool calls and after receiving tool results before deciding the next action or final answer.';
         if (!googleRequest.systemInstruction) {
             googleRequest.systemInstruction = { parts: [{ text: hint }] };
@@ -458,7 +483,7 @@ export function convertAnthropicToGoogle(anthropicRequest) {
             msgContent = reorderAssistantContent(msgContent);
         }
 
-        const parts = convertContentToParts(msgContent, isClaudeModel);
+        const parts = convertContentToParts(msgContent, isClaudeModel, isGeminiModel);
         const content = {
             role: convertRole(msg.role),
             parts: parts
@@ -488,22 +513,34 @@ export function convertAnthropicToGoogle(anthropicRequest) {
         googleRequest.generationConfig.stopSequences = stop_sequences;
     }
 
-    // Enable thinking for Claude thinking models
-    if (isClaudeThinkingModel) {
-        const thinkingConfig = {
-            include_thoughts: true
-        };
+    // Enable thinking for thinking models (Claude and Gemini 3+)
+    if (isThinking) {
+        if (isClaudeModel) {
+            // Claude thinking config
+            const thinkingConfig = {
+                include_thoughts: true
+            };
 
-        // Only set thinking_budget if explicitly provided
-        const thinkingBudget = thinking?.budget_tokens;
-        if (thinkingBudget) {
-            thinkingConfig.thinking_budget = thinkingBudget;
-            console.log('[FormatConverter] Thinking enabled with budget:', thinkingBudget);
-        } else {
-            console.log('[FormatConverter] Thinking enabled (no budget specified)');
+            // Only set thinking_budget if explicitly provided
+            const thinkingBudget = thinking?.budget_tokens;
+            if (thinkingBudget) {
+                thinkingConfig.thinking_budget = thinkingBudget;
+                console.log('[FormatConverter] Claude thinking enabled with budget:', thinkingBudget);
+            } else {
+                console.log('[FormatConverter] Claude thinking enabled (no budget specified)');
+            }
+
+            googleRequest.generationConfig.thinkingConfig = thinkingConfig;
+        } else if (isGeminiModel) {
+            // Gemini thinking config (uses camelCase)
+            const thinkingConfig = {
+                includeThoughts: true,
+                thinkingBudget: thinking?.budget_tokens || 16000
+            };
+            console.log('[FormatConverter] Gemini thinking enabled with budget:', thinkingConfig.thinkingBudget);
+
+            googleRequest.generationConfig.thinkingConfig = thinkingConfig;
         }
-
-        googleRequest.generationConfig.thinkingConfig = thinkingConfig;
     }
 
     // Convert tools to Google format
@@ -523,10 +560,18 @@ export function convertAnthropicToGoogle(anthropicRequest) {
                 || tool.parameters
                 || { type: 'object' };
 
+            // Sanitize schema for general compatibility
+            let parameters = sanitizeSchema(schema);
+
+            // For Gemini models, apply additional cleaning for VALIDATED mode
+            if (isGeminiModel) {
+                parameters = cleanSchemaForGemini(parameters);
+            }
+
             return {
                 name: String(name).replace(/[^a-zA-Z0-9_-]/g, '_').slice(0, 64),
                 description: description,
-                parameters: sanitizeSchema(schema)
+                parameters
             };
         });
 
@@ -534,6 +579,12 @@ export function convertAnthropicToGoogle(anthropicRequest) {
         console.log('[FormatConverter] Tools:', JSON.stringify(googleRequest.tools).substring(0, 300));
     }
 
+    // Cap max tokens for Gemini models
+    if (isGeminiModel && googleRequest.generationConfig.maxOutputTokens > GEMINI_MAX_OUTPUT_TOKENS) {
+        console.log(`[FormatConverter] Capping Gemini max_tokens from ${googleRequest.generationConfig.maxOutputTokens} to ${GEMINI_MAX_OUTPUT_TOKENS}`);
+        googleRequest.generationConfig.maxOutputTokens = GEMINI_MAX_OUTPUT_TOKENS;
+    }
+
     return googleRequest;
 }
 
@@ -620,6 +671,63 @@ function sanitizeSchema(schema) {
     return sanitized;
 }
 
+/**
+ * Cleans JSON schema for Gemini API compatibility.
+ * Removes unsupported fields that cause VALIDATED mode errors.
+ *
+ * Gemini's VALIDATED mode rejects schemas with certain JSON Schema keywords
+ * that are not supported by the Gemini API.
+ *
+ * @param {Object} schema - The JSON schema to clean
+ * @returns {Object} Cleaned schema safe for Gemini API
+ */
+function cleanSchemaForGemini(schema) {
+    if (!schema || typeof schema !== 'object') return schema;
+    if (Array.isArray(schema)) return schema.map(cleanSchemaForGemini);
+
+    const result = { ...schema };
+
+    // Remove unsupported keywords that cause VALIDATED mode errors
+    const unsupported = [
+        'additionalProperties', 'default', '$schema', '$defs',
+        'definitions', '$ref', '$id', '$comment', 'title',
+        'minLength', 'maxLength', 'pattern', 'format',
+        'minItems', 'maxItems', 'examples'
+    ];
+
+    for (const key of unsupported) {
+        delete result[key];
+    }
+
+    // Check for unsupported 'format' in string types
+    if (result.type === 'string' && result.format) {
+        const allowed = ['enum', 'date-time'];
+        if (!allowed.includes(result.format)) {
+            delete result.format;
+        }
+    }
+
+    // Recursively clean nested schemas
+    for (const [key, value] of Object.entries(result)) {
+        if (typeof value === 'object' && value !== null) {
+            result[key] = cleanSchemaForGemini(value);
+        }
+    }
+
+    // Validate that required array only contains properties that exist
+    // Gemini's VALIDATED mode requires this
+    if (result.required && Array.isArray(result.required) && result.properties) {
+        const definedProps = new Set(Object.keys(result.properties));
+        result.required = result.required.filter(prop => definedProps.has(prop));
+        // If required is now empty, remove it
+        if (result.required.length === 0) {
+            delete result.required;
+        }
+    }
+
+    return result;
+}
+
 /**
  * Convert Google Generative AI response to Anthropic Messages API format
  *
@@ -661,12 +769,20 @@ export function convertGoogleToAnthropic(googleResponse, model) {
         } else if (part.functionCall) {
             // Convert functionCall to tool_use
             // Use the id from the response if available, otherwise generate one
-            anthropicContent.push({
+            const toolId = part.functionCall.id || `toolu_${crypto.randomBytes(12).toString('hex')}`;
+            const toolUseBlock = {
                 type: 'tool_use',
-                id: part.functionCall.id || `toolu_${crypto.randomBytes(12).toString('hex')}`,
+                id: toolId,
                 name: part.functionCall.name,
                 input: part.functionCall.args || {}
-            });
+            };
+
+            // For Gemini 3+, include thoughtSignature from the part level
+            if (part.thoughtSignature && part.thoughtSignature.length >= MIN_SIGNATURE_LENGTH) {
+                toolUseBlock.thoughtSignature = part.thoughtSignature;
+            }
+
+            anthropicContent.push(toolUseBlock);
             hasToolCalls = true;
         }
     }
diff --git a/tests/helpers/http-client.cjs b/tests/helpers/http-client.cjs
index e8e7fc3..bdbbc79 100644
--- a/tests/helpers/http-client.cjs
+++ b/tests/helpers/http-client.cjs
@@ -147,6 +147,12 @@ function analyzeContent(content) {
     const toolUse = content.filter(b => b.type === 'tool_use');
     const text = content.filter(b => b.type === 'text');
 
+    // Check for signatures in thinking blocks (Claude style)
+    const thinkingHasSignature = thinking.some(t => t.signature && t.signature.length >= 50);
+
+    // Check for signatures in tool_use blocks (Gemini 3+ style)
+    const toolUseHasSignature = toolUse.some(t => t.thoughtSignature && t.thoughtSignature.length >= 50);
+
     return {
         thinking,
         toolUse,
@@ -154,7 +160,10 @@ function analyzeContent(content) {
         hasThinking: thinking.length > 0,
         hasToolUse: toolUse.length > 0,
         hasText: text.length > 0,
-        thinkingHasSignature: thinking.some(t => t.signature && t.signature.length >= 50)
+        thinkingHasSignature: thinkingHasSignature,
+        toolUseHasSignature: toolUseHasSignature,
+        // Combined check: signature exists somewhere (thinking or tool_use)
+        hasSignature: thinkingHasSignature || toolUseHasSignature
     };
 }
 
diff --git a/tests/helpers/test-models.cjs b/tests/helpers/test-models.cjs
new file mode 100644
index 0000000..b6c6c26
--- /dev/null
+++ b/tests/helpers/test-models.cjs
@@ -0,0 +1,87 @@
+/**
+ * Test Models Configuration
+ *
+ * Provides model configuration for parameterized testing across
+ * multiple model families (Claude and Gemini).
+ */
+
+// Default test models for each family
+const TEST_MODELS = {
+    claude: 'claude-sonnet-4-5-thinking',
+    gemini: 'gemini-3-flash'
+};
+
+// Default thinking model for each family
+const THINKING_MODELS = {
+    claude: 'claude-sonnet-4-5-thinking',
+    gemini: 'gemini-3-flash'
+};
+
+/**
+ * Get models to test, optionally excluding certain families.
+ * @param {string[]} excludeFamilies - Array of family names to exclude (e.g., ['gemini'])
+ * @returns {Array<{family: string, model: string}>} Array of model configs to test
+ */
+function getTestModels(excludeFamilies = []) {
+    const models = [];
+    for (const [family, model] of Object.entries(TEST_MODELS)) {
+        if (!excludeFamilies.includes(family)) {
+            models.push({ family, model });
+        }
+    }
+    return models;
+}
+
+/**
+ * Get thinking models to test, optionally excluding certain families.
+ * @param {string[]} excludeFamilies - Array of family names to exclude
+ * @returns {Array<{family: string, model: string}>} Array of thinking model configs
+ */
+function getThinkingModels(excludeFamilies = []) {
+    const models = [];
+    for (const [family, model] of Object.entries(THINKING_MODELS)) {
+        if (!excludeFamilies.includes(family)) {
+            models.push({ family, model });
+        }
+    }
+    return models;
+}
+
+/**
+ * Check if a model family requires thinking features.
+ * Both Claude thinking models and Gemini 3+ support thinking.
+ * @param {string} family - Model family name
+ * @returns {boolean} True if thinking is expected
+ */
+function familySupportsThinking(family) {
+    // Both Claude thinking models and Gemini 3+ support thinking
+    return family === 'claude' || family === 'gemini';
+}
+
+/**
+ * Get model-specific configuration overrides.
+ * @param {string} family - Model family name
+ * @returns {Object} Configuration overrides for the model family
+ */
+function getModelConfig(family) {
+    if (family === 'gemini') {
+        return {
+            // Gemini has lower max output tokens
+            max_tokens: 8000,
+            thinking: { type: 'enabled', budget_tokens: 10000 }
+        };
+    }
+    return {
+        max_tokens: 16000,
+        thinking: { type: 'enabled', budget_tokens: 10000 }
+    };
+}
+
+module.exports = {
+    TEST_MODELS,
+    THINKING_MODELS,
+    getTestModels,
+    getThinkingModels,
+    familySupportsThinking,
+    getModelConfig
+};
diff --git a/tests/test-caching-streaming.cjs b/tests/test-caching-streaming.cjs
index a0ba865..834159b 100644
--- a/tests/test-caching-streaming.cjs
+++ b/tests/test-caching-streaming.cjs
@@ -5,23 +5,28 @@
  * - Session ID is stable across turns (derived from first user message)
  * - cache_read_input_tokens is returned in usage metadata
  * - Second turn in same conversation should hit cache
+ *
+ * Runs for both Claude and Gemini model families.
  */
 const { streamRequest, analyzeContent, extractUsage } = require('./helpers/http-client.cjs');
+const { getTestModels, getModelConfig } = require('./helpers/test-models.cjs');
 
 // Large system prompt to exceed 1024 token minimum for caching
 // This matches the format used in the working direct API test (~36KB)
 const LARGE_SYSTEM_PROMPT = 'You are an expert software engineer. Here is important context:\n' +
     '// Large codebase file content line\n'.repeat(1000);
 
-async function runTests() {
+async function runTestsForModel(family, model) {
     console.log('='.repeat(60));
-    console.log('PROMPT CACHING TEST (STREAMING)');
+    console.log(`PROMPT CACHING TEST [${family.toUpperCase()}]`);
+    console.log(`Model: ${model}`);
     console.log('Verifies session ID stability and cache token reporting');
     console.log('='.repeat(60));
     console.log('');
 
     let allPassed = true;
     const results = [];
+    const modelConfig = getModelConfig(family);
 
     // ===== TURN 1: Initial request =====
     console.log('TURN 1: Initial request (establishes cache)');
@@ -35,11 +40,11 @@ async function runTests() {
     ];
 
     const turn1 = await streamRequest({
-        model: 'claude-sonnet-4-5-thinking',
-        max_tokens: 16000,
+        model,
+        max_tokens: modelConfig.max_tokens,
         stream: true,
         system: LARGE_SYSTEM_PROMPT,
-        thinking: { type: 'enabled', budget_tokens: 5000 },
+        thinking: modelConfig.thinking,
         messages: turn1Messages
     });
 
@@ -89,11 +94,11 @@ async function runTests() {
     ];
 
     const turn2 = await streamRequest({
-        model: 'claude-sonnet-4-5-thinking',
-        max_tokens: 16000,
+        model,
+        max_tokens: modelConfig.max_tokens,
         stream: true,
         system: LARGE_SYSTEM_PROMPT,
-        thinking: { type: 'enabled', budget_tokens: 5000 },
+        thinking: modelConfig.thinking,
         messages: turn2Messages
     });
 
@@ -143,7 +148,7 @@ async function runTests() {
 
     // ===== Summary =====
     console.log('\n' + '='.repeat(60));
-    console.log('SUMMARY');
+    console.log(`SUMMARY [${family.toUpperCase()}]`);
     console.log('='.repeat(60));
 
     for (const result of results) {
@@ -156,7 +161,7 @@ async function runTests() {
     }
 
     console.log('\n' + '='.repeat(60));
-    console.log(`OVERALL: ${allPassed ? 'ALL TESTS PASSED' : 'SOME TESTS FAILED'}`);
+    console.log(`[${family.toUpperCase()}] ${allPassed ? 'ALL TESTS PASSED' : 'SOME TESTS FAILED'}`);
     console.log('='.repeat(60));
 
     console.log('\nNote: Cache effectiveness depends on:');
@@ -164,6 +169,25 @@ async function runTests() {
     console.log('  2. Sticky account selection (same account across turns)');
     console.log('  3. API-side cache availability (may take time to populate)');
 
+    return allPassed;
+}
+
+async function runTests() {
+    const models = getTestModels();
+    let allPassed = true;
+
+    for (const { family, model } of models) {
+        console.log('\n');
+        const passed = await runTestsForModel(family, model);
+        if (!passed) allPassed = false;
+    }
+
+    console.log('\n' + '='.repeat(60));
+    console.log('FINAL RESULT');
+    console.log('='.repeat(60));
+    console.log(`Overall: ${allPassed ? 'ALL MODEL FAMILIES PASSED' : 'SOME MODEL FAMILIES FAILED'}`);
+    console.log('='.repeat(60));
+
     process.exit(allPassed ? 0 : 1);
 }
 
diff --git a/tests/test-images.cjs b/tests/test-images.cjs
index 10740b9..0393709 100644
--- a/tests/test-images.cjs
+++ b/tests/test-images.cjs
@@ -3,34 +3,40 @@
  *
  * Tests that images can be sent to the API with thinking models.
  * Simulates Claude Code sending screenshots or images for analysis.
+ *
+ * Runs for both Claude and Gemini model families.
  */
 const fs = require('fs');
 const path = require('path');
-const { streamRequest } = require('./helpers/http-client.cjs');
+const { streamRequest, analyzeContent } = require('./helpers/http-client.cjs');
+const { getTestModels, getModelConfig, familySupportsThinking } = require('./helpers/test-models.cjs');
 
 // Load test image from disk
 const TEST_IMAGE_PATH = path.join(__dirname, 'utils', 'test_image.jpeg');
 const TEST_IMAGE_BASE64 = fs.readFileSync(TEST_IMAGE_PATH).toString('base64');
 
-async function runTests() {
+async function runTestsForModel(family, model) {
     console.log('='.repeat(60));
-    console.log('IMAGE SUPPORT TEST');
+    console.log(`IMAGE SUPPORT TEST [${family.toUpperCase()}]`);
+    console.log(`Model: ${model}`);
     console.log('Tests image processing with thinking models');
     console.log('='.repeat(60));
     console.log('');
 
     let allPassed = true;
     const results = [];
+    const modelConfig = getModelConfig(family);
+    const expectThinking = familySupportsThinking(family);
 
     // ===== TEST 1: Single image with question =====
     console.log('TEST 1: Single image with question');
     console.log('-'.repeat(40));
 
     const result1 = await streamRequest({
-        model: 'claude-sonnet-4-5-thinking',
-        max_tokens: 16000,
+        model,
+        max_tokens: modelConfig.max_tokens,
         stream: true,
-        thinking: { type: 'enabled', budget_tokens: 8000 },
+        thinking: modelConfig.thinking,
         messages: [{
             role: 'user',
             content: [
@@ -55,20 +61,22 @@ async function runTests() {
         allPassed = false;
         results.push({ name: 'Single image processing', passed: false });
     } else {
-        const thinking = result1.content.filter(b => b.type === 'thinking');
-        const text = result1.content.filter(b => b.type === 'text');
+        const content = analyzeContent(result1.content);
 
-        console.log(`  Thinking: ${thinking.length > 0 ? 'YES' : 'NO'}`);
-        console.log(`  Text response: ${text.length > 0 ? 'YES' : 'NO'}`);
+        console.log(`  Thinking: ${content.hasThinking ? 'YES' : 'NO'}`);
+        console.log(`  Text response: ${content.hasText ? 'YES' : 'NO'}`);
 
-        if (thinking.length > 0) {
-            console.log(`  Thinking: "${thinking[0].thinking?.substring(0, 60)}..."`);
+        if (content.hasThinking && content.thinking[0].thinking) {
+            console.log(`  Thinking: "${content.thinking[0].thinking.substring(0, 60)}..."`);
         }
-        if (text.length > 0) {
-            console.log(`  Response: "${text[0].text?.substring(0, 100)}..."`);
+        if (content.hasText && content.text[0].text) {
+            console.log(`  Response: "${content.text[0].text.substring(0, 100)}..."`);
         }
 
-        const passed = thinking.length > 0 && text.length > 0;
+        // For thinking models, expect thinking + text. For others, just text.
+        const passed = expectThinking
+            ? (content.hasThinking && content.hasText)
+            : content.hasText;
         results.push({ name: 'Single image processing', passed });
         if (!passed) allPassed = false;
     }
@@ -78,10 +86,10 @@ async function runTests() {
     console.log('-'.repeat(40));
 
     const result2 = await streamRequest({
-        model: 'claude-sonnet-4-5-thinking',
-        max_tokens: 16000,
+        model,
+        max_tokens: modelConfig.max_tokens,
         stream: true,
-        thinking: { type: 'enabled', budget_tokens: 8000 },
+        thinking: modelConfig.thinking,
         messages: [
             {
                 role: 'user',
@@ -119,24 +127,23 @@ async function runTests() {
         allPassed = false;
         results.push({ name: 'Image in multi-turn', passed: false });
     } else {
-        const thinking = result2.content.filter(b => b.type === 'thinking');
-        const text = result2.content.filter(b => b.type === 'text');
+        const content = analyzeContent(result2.content);
 
-        console.log(`  Thinking: ${thinking.length > 0 ? 'YES' : 'NO'}`);
-        console.log(`  Text response: ${text.length > 0 ? 'YES' : 'NO'}`);
+        console.log(`  Thinking: ${content.hasThinking ? 'YES' : 'NO'}`);
+        console.log(`  Text response: ${content.hasText ? 'YES' : 'NO'}`);
 
-        if (text.length > 0) {
-            console.log(`  Response: "${text[0].text?.substring(0, 80)}..."`);
+        if (content.hasText && content.text[0].text) {
+            console.log(`  Response: "${content.text[0].text.substring(0, 80)}..."`);
         }
 
-        const passed = text.length > 0;
+        const passed = content.hasText;
         results.push({ name: 'Image in multi-turn', passed });
         if (!passed) allPassed = false;
     }
 
     // ===== Summary =====
     console.log('\n' + '='.repeat(60));
-    console.log('SUMMARY');
+    console.log(`SUMMARY [${family.toUpperCase()}]`);
     console.log('='.repeat(60));
 
     for (const result of results) {
@@ -145,7 +152,26 @@ async function runTests() {
     }
 
     console.log('\n' + '='.repeat(60));
-    console.log(`OVERALL: ${allPassed ? 'ALL TESTS PASSED' : 'SOME TESTS FAILED'}`);
+    console.log(`[${family.toUpperCase()}] ${allPassed ? 'ALL TESTS PASSED' : 'SOME TESTS FAILED'}`);
+    console.log('='.repeat(60));
+
+    return allPassed;
+}
+
+async function runTests() {
+    const models = getTestModels();
+    let allPassed = true;
+
+    for (const { family, model } of models) {
+        console.log('\n');
+        const passed = await runTestsForModel(family, model);
+        if (!passed) allPassed = false;
+    }
+
+    console.log('\n' + '='.repeat(60));
+    console.log('FINAL RESULT');
+    console.log('='.repeat(60));
+    console.log(`Overall: ${allPassed ? 'ALL MODEL FAMILIES PASSED' : 'SOME MODEL FAMILIES FAILED'}`);
     console.log('='.repeat(60));
 
     process.exit(allPassed ? 0 : 1);
diff --git a/tests/test-interleaved-thinking.cjs b/tests/test-interleaved-thinking.cjs
index 5216c7a..620480f 100644
--- a/tests/test-interleaved-thinking.cjs
+++ b/tests/test-interleaved-thinking.cjs
@@ -8,32 +8,38 @@
  *
  * This simulates complex Claude Code scenarios where the model
  * thinks multiple times during a single turn.
+ *
+ * NOTE: This test is Claude-only. Interleaved thinking requires
+ * the anthropic-beta header which is specific to Claude thinking models.
  */
 const { streamRequest, commonTools } = require('./helpers/http-client.cjs');
+const { getThinkingModels, getModelConfig } = require('./helpers/test-models.cjs');
 
 // Multiple tools to encourage interleaved thinking
 const tools = [commonTools.readFile, commonTools.writeFile, commonTools.runTests];
 
-async function runTests() {
+async function runTestsForModel(family, model) {
     console.log('='.repeat(60));
-    console.log('INTERLEAVED THINKING TEST');
+    console.log(`INTERLEAVED THINKING TEST [${family.toUpperCase()}]`);
+    console.log(`Model: ${model}`);
     console.log('Tests complex multi-step reasoning with tools');
     console.log('='.repeat(60));
     console.log('');
 
     let allPassed = true;
     const results = [];
+    const modelConfig = getModelConfig(family);
 
     // ===== TEST 1: Complex task requiring multiple steps =====
     console.log('TEST 1: Complex task - read, modify, write, test');
     console.log('-'.repeat(40));
 
     const result = await streamRequest({
-        model: 'claude-opus-4-5-thinking',
-        max_tokens: 32000,
+        model,
+        max_tokens: modelConfig.max_tokens,
         stream: true,
         tools,
-        thinking: { type: 'enabled', budget_tokens: 16000 },
+        thinking: modelConfig.thinking,
         messages: [{
             role: 'user',
             content: `I need you to:
@@ -92,11 +98,11 @@ Please do this step by step, reading each file before modifying.`
         const toolUseBlock = result.content.find(b => b.type === 'tool_use');
 
         const result2 = await streamRequest({
-            model: 'claude-opus-4-5-thinking',
-            max_tokens: 32000,
+            model,
+            max_tokens: modelConfig.max_tokens,
             stream: true,
             tools,
-            thinking: { type: 'enabled', budget_tokens: 16000 },
+            thinking: modelConfig.thinking,
             messages: [
                 {
                     role: 'user',
@@ -147,7 +153,7 @@ Please do this step by step, reading each file before modifying.`
 
     // ===== Summary =====
     console.log('\n' + '='.repeat(60));
-    console.log('SUMMARY');
+    console.log(`SUMMARY [${family.toUpperCase()}]`);
     console.log('='.repeat(60));
 
     for (const result of results) {
@@ -156,7 +162,27 @@ Please do this step by step, reading each file before modifying.`
     }
 
     console.log('\n' + '='.repeat(60));
-    console.log(`OVERALL: ${allPassed ? 'ALL TESTS PASSED' : 'SOME TESTS FAILED'}`);
+    console.log(`[${family.toUpperCase()}] ${allPassed ? 'ALL TESTS PASSED' : 'SOME TESTS FAILED'}`);
+    console.log('='.repeat(60));
+
+    return allPassed;
+}
+
+async function runTests() {
+    // Interleaved thinking is Claude-only (requires anthropic-beta header)
+    const models = getThinkingModels(['gemini']);
+    let allPassed = true;
+
+    for (const { family, model } of models) {
+        console.log('\n');
+        const passed = await runTestsForModel(family, model);
+        if (!passed) allPassed = false;
+    }
+
+    console.log('\n' + '='.repeat(60));
+    console.log('FINAL RESULT');
+    console.log('='.repeat(60));
+    console.log(`Overall: ${allPassed ? 'ALL TESTS PASSED' : 'SOME TESTS FAILED'}`);
     console.log('='.repeat(60));
 
     process.exit(allPassed ? 0 : 1);
diff --git a/tests/test-multiturn-thinking-tools-streaming.cjs b/tests/test-multiturn-thinking-tools-streaming.cjs
index 2aa53d0..6f14dd3 100644
--- a/tests/test-multiturn-thinking-tools-streaming.cjs
+++ b/tests/test-multiturn-thinking-tools-streaming.cjs
@@ -6,14 +6,18 @@
  * - SSE events are properly formatted
  * - signature_delta events are present
  * - Thinking blocks accumulate correctly across deltas
+ *
+ * Runs for both Claude and Gemini model families.
  */
 const { streamRequest, analyzeContent, analyzeEvents, commonTools } = require('./helpers/http-client.cjs');
+const { getTestModels, getModelConfig } = require('./helpers/test-models.cjs');
 
 const tools = [commonTools.executeCommand];
 
-async function runTests() {
+async function runTestsForModel(family, model) {
     console.log('='.repeat(60));
-    console.log('MULTI-TURN TOOL CALL TEST (STREAMING)');
+    console.log(`MULTI-TURN TOOL CALL TEST [${family.toUpperCase()}]`);
+    console.log(`Model: ${model}`);
     console.log('Simulates Claude Code streaming conversation');
     console.log('='.repeat(60));
     console.log('');
@@ -21,6 +25,7 @@ async function runTests() {
     let messages = [];
     let allPassed = true;
     const results = [];
+    const modelConfig = getModelConfig(family);
 
     // ===== TURN 1: Initial request =====
     console.log('TURN 1: User asks to run a command');
@@ -32,11 +37,11 @@ async function runTests() {
     });
 
     const turn1 = await streamRequest({
-        model: 'claude-sonnet-4-5-thinking',
-        max_tokens: 16000,
+        model,
+        max_tokens: modelConfig.max_tokens,
         stream: true,
         tools,
-        thinking: { type: 'enabled', budget_tokens: 10000 },
+        thinking: modelConfig.thinking,
         messages
     });
 
@@ -50,7 +55,7 @@ async function runTests() {
 
         console.log('  Content:');
         console.log(`    Thinking: ${content.hasThinking ? 'YES' : 'NO'} (${content.thinking.length} blocks)`);
-        console.log(`    Signature: ${content.thinkingHasSignature ? 'YES' : 'NO'}`);
+        console.log(`    Signature: ${content.hasSignature ? 'YES' : 'NO'}`);
         console.log(`    Tool Use: ${content.hasToolUse ? 'YES' : 'NO'} (${content.toolUse.length} calls)`);
 
         console.log('  Events:');
@@ -67,9 +72,11 @@ async function runTests() {
             console.log(`  Tool: ${content.toolUse[0].name}(${JSON.stringify(content.toolUse[0].input)})`);
         }
 
-        const passed = content.hasThinking && content.thinkingHasSignature &&
-                       events.signatureDeltas > 0 && content.hasToolUse;
-        results.push({ name: 'Turn 1: Thinking + Signature + Tool Use + Events', passed });
+        // For Claude: signature is on thinking block and comes via signature_delta events
+        // For Gemini: signature is on tool_use block (no signature_delta events)
+        const hasSignature = content.hasSignature || events.signatureDeltas > 0;
+        const passed = content.hasThinking && hasSignature && content.hasToolUse;
+        results.push({ name: 'Turn 1: Thinking + Signature + Tool Use', passed });
         if (!passed) allPassed = false;
 
         if (content.hasToolUse) {
@@ -101,11 +108,11 @@ drwxr-xr-x   4 user  staff   128 Dec 19 10:00 tests`
         });
 
         const turn2 = await streamRequest({
-            model: 'claude-sonnet-4-5-thinking',
-            max_tokens: 16000,
+            model,
+            max_tokens: modelConfig.max_tokens,
             stream: true,
             tools,
-            thinking: { type: 'enabled', budget_tokens: 10000 },
+            thinking: modelConfig.thinking,
             messages
         });
 
@@ -119,7 +126,7 @@ drwxr-xr-x   4 user  staff   128 Dec 19 10:00 tests`
 
             console.log('  Content:');
             console.log(`    Thinking: ${content.hasThinking ? 'YES' : 'NO'} (${content.thinking.length} blocks)`);
-            console.log(`    Signature: ${content.thinkingHasSignature ? 'YES' : 'NO'}`);
+            console.log(`    Signature: ${content.hasSignature ? 'YES' : 'NO'}`);
             console.log(`    Text: ${content.hasText ? 'YES' : 'NO'}`);
 
             console.log('  Events:');
@@ -139,7 +146,7 @@ drwxr-xr-x   4 user  staff   128 Dec 19 10:00 tests`
 
     // ===== Summary =====
     console.log('\n' + '='.repeat(60));
-    console.log('SUMMARY');
+    console.log(`SUMMARY [${family.toUpperCase()}]`);
     console.log('='.repeat(60));
 
     for (const result of results) {
@@ -148,7 +155,26 @@ drwxr-xr-x   4 user  staff   128 Dec 19 10:00 tests`
     }
 
     console.log('\n' + '='.repeat(60));
-    console.log(`OVERALL: ${allPassed ? 'ALL TESTS PASSED' : 'SOME TESTS FAILED'}`);
+    console.log(`[${family.toUpperCase()}] ${allPassed ? 'ALL TESTS PASSED' : 'SOME TESTS FAILED'}`);
+    console.log('='.repeat(60));
+
+    return allPassed;
+}
+
+async function runTests() {
+    const models = getTestModels();
+    let allPassed = true;
+
+    for (const { family, model } of models) {
+        console.log('\n');
+        const passed = await runTestsForModel(family, model);
+        if (!passed) allPassed = false;
+    }
+
+    console.log('\n' + '='.repeat(60));
+    console.log('FINAL RESULT');
+    console.log('='.repeat(60));
+    console.log(`Overall: ${allPassed ? 'ALL MODEL FAMILIES PASSED' : 'SOME MODEL FAMILIES FAILED'}`);
     console.log('='.repeat(60));
 
     process.exit(allPassed ? 0 : 1);
diff --git a/tests/test-multiturn-thinking-tools.cjs b/tests/test-multiturn-thinking-tools.cjs
index e479d91..0a38adb 100644
--- a/tests/test-multiturn-thinking-tools.cjs
+++ b/tests/test-multiturn-thinking-tools.cjs
@@ -11,14 +11,18 @@
  * - Thinking blocks with signatures are preserved across turns
  * - Tool use/result flow works correctly
  * - Interleaved thinking with tools
+ *
+ * Runs for both Claude and Gemini model families.
  */
 const { makeRequest, analyzeContent, commonTools } = require('./helpers/http-client.cjs');
+const { getTestModels, getModelConfig, familySupportsThinking } = require('./helpers/test-models.cjs');
 
 const tools = [commonTools.searchFiles, commonTools.readFile];
 
-async function runTests() {
+async function runTestsForModel(family, model) {
     console.log('='.repeat(60));
-    console.log('MULTI-TURN TOOL CALL TEST (NON-STREAMING)');
+    console.log(`MULTI-TURN TOOL CALL TEST [${family.toUpperCase()}]`);
+    console.log(`Model: ${model}`);
     console.log('Simulates Claude Code conversation pattern');
     console.log('='.repeat(60));
     console.log('');
@@ -26,6 +30,8 @@ async function runTests() {
     let messages = [];
     let allPassed = true;
     const results = [];
+    const modelConfig = getModelConfig(family);
+    const expectThinking = familySupportsThinking(family);
 
     // ===== TURN 1: Initial request =====
     console.log('TURN 1: User asks to find and read a config file');
@@ -37,11 +43,11 @@ async function runTests() {
     });
 
     const turn1 = await makeRequest({
-        model: 'claude-sonnet-4-5-thinking',
-        max_tokens: 16000,
+        model,
+        max_tokens: modelConfig.max_tokens,
         stream: false,
         tools,
-        thinking: { type: 'enabled', budget_tokens: 10000 },
+        thinking: modelConfig.thinking,
         messages
     });
 
@@ -52,7 +58,7 @@ async function runTests() {
     } else {
         const analysis = analyzeContent(turn1.content || []);
         console.log(`  Thinking: ${analysis.hasThinking ? 'YES' : 'NO'} (${analysis.thinking.length} blocks)`);
-        console.log(`  Signature: ${analysis.thinkingHasSignature ? 'YES' : 'NO'}`);
+        console.log(`  Signature: ${analysis.hasSignature ? 'YES' : 'NO'}`);
         console.log(`  Tool Use: ${analysis.hasToolUse ? 'YES' : 'NO'} (${analysis.toolUse.length} calls)`);
         console.log(`  Text: ${analysis.hasText ? 'YES' : 'NO'}`);
 
@@ -63,7 +69,11 @@ async function runTests() {
             console.log(`  Tool: ${analysis.toolUse[0].name}(${JSON.stringify(analysis.toolUse[0].input)})`);
         }
 
-        const passed = analysis.hasThinking && analysis.thinkingHasSignature && analysis.hasToolUse;
+        // For thinking models, expect thinking + signature + tool use
+        // For non-thinking models, just expect tool use
+        const passed = expectThinking
+            ? (analysis.hasThinking && analysis.hasSignature && analysis.hasToolUse)
+            : analysis.hasToolUse;
         results.push({ name: 'Turn 1: Thinking + Signature + Tool Use', passed });
         if (!passed) allPassed = false;
 
@@ -91,11 +101,11 @@ async function runTests() {
         });
 
         const turn2 = await makeRequest({
-            model: 'claude-sonnet-4-5-thinking',
-            max_tokens: 16000,
+            model,
+            max_tokens: modelConfig.max_tokens,
             stream: false,
             tools,
-            thinking: { type: 'enabled', budget_tokens: 10000 },
+            thinking: modelConfig.thinking,
             messages
         });
 
@@ -106,7 +116,7 @@ async function runTests() {
         } else {
             const analysis = analyzeContent(turn2.content || []);
             console.log(`  Thinking: ${analysis.hasThinking ? 'YES' : 'NO'} (${analysis.thinking.length} blocks)`);
-            console.log(`  Signature: ${analysis.thinkingHasSignature ? 'YES' : 'NO'}`);
+            console.log(`  Signature: ${analysis.hasSignature ? 'YES' : 'NO'}`);
             console.log(`  Tool Use: ${analysis.hasToolUse ? 'YES' : 'NO'} (${analysis.toolUse.length} calls)`);
             console.log(`  Text: ${analysis.hasText ? 'YES' : 'NO'}`);
 
@@ -118,7 +128,9 @@ async function runTests() {
             }
 
             // Either tool use (to read file) or text response is acceptable
-            const passed = analysis.hasThinking && (analysis.hasToolUse || analysis.hasText);
+            const passed = expectThinking
+                ? (analysis.hasThinking && (analysis.hasToolUse || analysis.hasText))
+                : (analysis.hasToolUse || analysis.hasText);
             results.push({ name: 'Turn 2: Thinking + (Tool or Text)', passed });
             if (!passed) allPassed = false;
 
@@ -155,11 +167,11 @@ async function runTests() {
             });
 
             const turn3 = await makeRequest({
-                model: 'claude-sonnet-4-5-thinking',
-                max_tokens: 16000,
+                model,
+                max_tokens: modelConfig.max_tokens,
                 stream: false,
                 tools,
-                thinking: { type: 'enabled', budget_tokens: 10000 },
+                thinking: modelConfig.thinking,
                 messages
             });
 
@@ -168,19 +180,23 @@ async function runTests() {
                 allPassed = false;
                 results.push({ name: 'Turn 3: Final response', passed: false });
             } else {
-                const analysis = analyzeContent(turn3.content || []);
+                            const analysis = analyzeContent(turn3.content || []);
                 console.log(`  Thinking: ${analysis.hasThinking ? 'YES' : 'NO'} (${analysis.thinking.length} blocks)`);
-                console.log(`  Signature: ${analysis.thinkingHasSignature ? 'YES' : 'NO'}`);
+                console.log(`  Signature: ${analysis.hasSignature ? 'YES' : 'NO'}`);
+                console.log(`  Tool Use: ${analysis.hasToolUse ? 'YES' : 'NO'} (${analysis.toolUse.length} calls)`);
                 console.log(`  Text: ${analysis.hasText ? 'YES' : 'NO'}`);
 
                 if (analysis.hasText && analysis.text[0].text) {
                     console.log(`  Response: "${analysis.text[0].text.substring(0, 100)}..."`);
                 }
+                if (analysis.hasToolUse) {
+                    console.log(`  Tool: ${analysis.toolUse[0].name}(${JSON.stringify(analysis.toolUse[0].input)})`);
+                }
 
-                // Thinking is optional for final responses - model may skip it for simple tasks
-                const passed = analysis.hasText;
-                const thinkingNote = analysis.hasThinking ? ' (with thinking)' : ' (no thinking - normal for simple tasks)';
-                results.push({ name: 'Turn 3: Text response' + thinkingNote, passed });
+                // For final turn: expect text OR another tool call (model may need more info)
+                const passed = analysis.hasText || analysis.hasToolUse;
+                const responseType = analysis.hasText ? 'text' : (analysis.hasToolUse ? 'tool_use' : 'none');
+                results.push({ name: `Turn 3: Response (${responseType})`, passed });
                 if (!passed) allPassed = false;
             }
         }
@@ -188,7 +204,7 @@ async function runTests() {
 
     // ===== Summary =====
     console.log('\n' + '='.repeat(60));
-    console.log('SUMMARY');
+    console.log(`SUMMARY [${family.toUpperCase()}]`);
     console.log('='.repeat(60));
 
     for (const result of results) {
@@ -197,7 +213,26 @@ async function runTests() {
     }
 
     console.log('\n' + '='.repeat(60));
-    console.log(`OVERALL: ${allPassed ? 'ALL TESTS PASSED' : 'SOME TESTS FAILED'}`);
+    console.log(`[${family.toUpperCase()}] ${allPassed ? 'ALL TESTS PASSED' : 'SOME TESTS FAILED'}`);
+    console.log('='.repeat(60));
+
+    return allPassed;
+}
+
+async function runTests() {
+    const models = getTestModels();
+    let allPassed = true;
+
+    for (const { family, model } of models) {
+        console.log('\n');
+        const passed = await runTestsForModel(family, model);
+        if (!passed) allPassed = false;
+    }
+
+    console.log('\n' + '='.repeat(60));
+    console.log('FINAL RESULT');
+    console.log('='.repeat(60));
+    console.log(`Overall: ${allPassed ? 'ALL MODEL FAMILIES PASSED' : 'SOME MODEL FAMILIES FAILED'}`);
     console.log('='.repeat(60));
 
     process.exit(allPassed ? 0 : 1);
diff --git a/tests/test-thinking-signatures.cjs b/tests/test-thinking-signatures.cjs
index fb1fcb1..606f4ee 100644
--- a/tests/test-thinking-signatures.cjs
+++ b/tests/test-thinking-signatures.cjs
@@ -6,20 +6,28 @@
  *
  * Claude Code sends assistant messages with thinking blocks that include signatures.
  * These signatures must be preserved and sent back to the API.
+ *
+ * Note: Claude puts signatures on thinking blocks, Gemini 3+ puts them on tool_use blocks.
+ *
+ * Runs for both Claude and Gemini model families.
  */
-const { streamRequest, commonTools } = require('./helpers/http-client.cjs');
+const { streamRequest, analyzeContent, commonTools } = require('./helpers/http-client.cjs');
+const { getThinkingModels, getModelConfig, familySupportsThinking } = require('./helpers/test-models.cjs');
 
 const tools = [commonTools.getWeather];
 
-async function runTests() {
+async function runTestsForModel(family, model) {
     console.log('='.repeat(60));
-    console.log('THINKING SIGNATURE TEST');
+    console.log(`THINKING SIGNATURE TEST [${family.toUpperCase()}]`);
+    console.log(`Model: ${model}`);
     console.log('Simulates Claude Code multi-turn with thinking blocks');
     console.log('='.repeat(60));
     console.log('');
 
     let allPassed = true;
     const results = [];
+    const modelConfig = getModelConfig(family);
+    const expectThinking = familySupportsThinking(family);
 
     // ===== TEST 1: First turn - get thinking block with signature =====
     console.log('TEST 1: Initial request with thinking model');
@@ -30,35 +38,34 @@ async function runTests() {
     ];
 
     const turn1Result = await streamRequest({
-        model: 'claude-sonnet-4-5-thinking',
-        max_tokens: 16000,
+        model,
+        max_tokens: modelConfig.max_tokens,
         stream: true,
         tools,
-        thinking: { type: 'enabled', budget_tokens: 10000 },
+        thinking: modelConfig.thinking,
         messages: turn1Messages
     });
 
-    const turn1Thinking = turn1Result.content.filter(b => b.type === 'thinking');
-    const turn1ToolUse = turn1Result.content.filter(b => b.type === 'tool_use');
-    const turn1Text = turn1Result.content.filter(b => b.type === 'text');
+    const content = analyzeContent(turn1Result.content);
 
-    console.log(`  Thinking blocks: ${turn1Thinking.length}`);
-    console.log(`  Tool use blocks: ${turn1ToolUse.length}`);
-    console.log(`  Text blocks: ${turn1Text.length}`);
+    console.log(`  Thinking blocks: ${content.thinking.length}`);
+    console.log(`  Tool use blocks: ${content.toolUse.length}`);
+    console.log(`  Text blocks: ${content.text.length}`);
 
-    // Check thinking has signature
-    let turn1HasSignature = false;
-    if (turn1Thinking.length > 0) {
-        const sig = turn1Thinking[0].signature || '';
-        turn1HasSignature = sig.length >= 50;
-        console.log(`  Signature length: ${sig.length} chars`);
-        console.log(`  Signature present: ${turn1HasSignature ? 'YES' : 'NO'}`);
-        if (turn1Thinking[0].thinking) {
-            console.log(`  Thinking preview: "${turn1Thinking[0].thinking.substring(0, 80)}..."`);
-        }
+    // Check signatures - Claude puts them on thinking blocks, Gemini on tool_use blocks
+    console.log(`  Thinking signature: ${content.thinkingHasSignature ? 'YES' : 'NO'}`);
+    console.log(`  Tool use signature: ${content.toolUseHasSignature ? 'YES' : 'NO'}`);
+    console.log(`  Has signature (combined): ${content.hasSignature ? 'YES' : 'NO'}`);
+
+    if (content.hasThinking && content.thinking[0].thinking) {
+        console.log(`  Thinking preview: "${content.thinking[0].thinking.substring(0, 80)}..."`);
     }
 
-    const test1Pass = turn1Thinking.length > 0 && turn1HasSignature && turn1ToolUse.length > 0;
+    // For models that support thinking, expect thinking + signature (somewhere) + tool use
+    // For models that don't, just expect tool use
+    const test1Pass = expectThinking
+        ? (content.hasThinking && content.hasSignature && content.hasToolUse)
+        : (content.hasToolUse || content.hasText);
     results.push({ name: 'Turn 1: Thinking + Signature + Tool Use', passed: test1Pass });
     console.log(`  Result: ${test1Pass ? 'PASS' : 'FAIL'}`);
     if (!test1Pass) allPassed = false;
@@ -67,18 +74,22 @@ async function runTests() {
     console.log('\nTEST 2: Multi-turn with thinking signature in assistant message');
     console.log('-'.repeat(40));
 
-    if (!turn1ToolUse.length) {
+    if (!content.hasToolUse) {
         console.log('  SKIPPED - No tool use in turn 1');
         results.push({ name: 'Turn 2: Multi-turn with signature', passed: false, skipped: true });
     } else {
         // Build assistant message with thinking (including signature) - this is how Claude Code sends it
         const assistantContent = turn1Result.content;
 
-        // Verify the thinking block has signature before sending
+        // Log what we're sending back
         const thinkingInAssistant = assistantContent.find(b => b.type === 'thinking');
+        const toolUseInAssistant = assistantContent.find(b => b.type === 'tool_use');
         if (thinkingInAssistant) {
             console.log(`  Sending thinking with signature: ${(thinkingInAssistant.signature || '').length} chars`);
         }
+        if (toolUseInAssistant && toolUseInAssistant.thoughtSignature) {
+            console.log(`  Sending tool_use with thoughtSignature: ${toolUseInAssistant.thoughtSignature.length} chars`);
+        }
 
         const turn2Messages = [
             ...turn1Messages,
@@ -87,26 +98,25 @@ async function runTests() {
                 role: 'user',
                 content: [{
                     type: 'tool_result',
-                    tool_use_id: turn1ToolUse[0].id,
+                    tool_use_id: content.toolUse[0].id,
                     content: 'The weather in Paris is 18°C and sunny.'
                 }]
             }
         ];
 
         const turn2Result = await streamRequest({
-            model: 'claude-sonnet-4-5-thinking',
-            max_tokens: 16000,
+            model,
+            max_tokens: modelConfig.max_tokens,
             stream: true,
             tools,
-            thinking: { type: 'enabled', budget_tokens: 10000 },
+            thinking: modelConfig.thinking,
             messages: turn2Messages
         });
 
-        const turn2Thinking = turn2Result.content.filter(b => b.type === 'thinking');
-        const turn2Text = turn2Result.content.filter(b => b.type === 'text');
+        const turn2Content = analyzeContent(turn2Result.content);
 
-        console.log(`  Thinking blocks: ${turn2Thinking.length}`);
-        console.log(`  Text blocks: ${turn2Text.length}`);
+        console.log(`  Thinking blocks: ${turn2Content.thinking.length}`);
+        console.log(`  Text blocks: ${turn2Content.text.length}`);
 
         // Check for errors
         const hasError = turn2Result.events.some(e => e.type === 'error');
@@ -115,26 +125,22 @@ async function runTests() {
             console.log(`  ERROR: ${errorEvent?.data?.error?.message || 'Unknown error'}`);
         }
 
-        if (turn2Thinking.length > 0) {
-            const sig = turn2Thinking[0].signature || '';
-            console.log(`  New signature length: ${sig.length} chars`);
-            if (turn2Thinking[0].thinking) {
-                console.log(`  Thinking preview: "${turn2Thinking[0].thinking.substring(0, 80)}..."`);
-            }
+        if (turn2Content.hasThinking && turn2Content.thinking[0].thinking) {
+            console.log(`  Thinking preview: "${turn2Content.thinking[0].thinking.substring(0, 80)}..."`);
         }
 
-        if (turn2Text.length > 0 && turn2Text[0].text) {
-            console.log(`  Response: "${turn2Text[0].text.substring(0, 100)}..."`);
+        if (turn2Content.hasText && turn2Content.text[0].text) {
+            console.log(`  Response: "${turn2Content.text[0].text.substring(0, 100)}..."`);
         }
 
-        const test2Pass = !hasError && (turn2Thinking.length > 0 || turn2Text.length > 0);
+        const test2Pass = !hasError && (turn2Content.hasThinking || turn2Content.hasText);
         results.push({ name: 'Turn 2: Multi-turn with signature', passed: test2Pass });
         console.log(`  Result: ${test2Pass ? 'PASS' : 'FAIL'}`);
         if (!test2Pass) allPassed = false;
     }
 
     // ===== TEST 3: Verify signature_delta events in stream =====
-    console.log('\nTEST 3: Verify signature_delta events in stream');
+    console.log('\nTEST 3: Verify signature events in stream');
     console.log('-'.repeat(40));
 
     const signatureDeltas = turn1Result.events.filter(
@@ -147,14 +153,18 @@ async function runTests() {
         console.log(`  Total signature length from deltas: ${totalSigLength} chars`);
     }
 
-    const test3Pass = signatureDeltas.length > 0;
-    results.push({ name: 'signature_delta events present', passed: test3Pass });
+    // For Claude: signature_delta events should be present
+    // For Gemini: signature is attached to tool_use block directly, may not have signature_delta events
+    const test3Pass = expectThinking
+        ? (signatureDeltas.length > 0 || content.toolUseHasSignature)
+        : true;
+    results.push({ name: 'Signature present (delta or on tool_use)', passed: test3Pass });
     console.log(`  Result: ${test3Pass ? 'PASS' : 'FAIL'}`);
     if (!test3Pass) allPassed = false;
 
     // ===== Summary =====
     console.log('\n' + '='.repeat(60));
-    console.log('SUMMARY');
+    console.log(`SUMMARY [${family.toUpperCase()}]`);
     console.log('='.repeat(60));
 
     for (const result of results) {
@@ -163,7 +173,26 @@ async function runTests() {
     }
 
     console.log('\n' + '='.repeat(60));
-    console.log(`OVERALL: ${allPassed ? 'ALL TESTS PASSED' : 'SOME TESTS FAILED'}`);
+    console.log(`[${family.toUpperCase()}] ${allPassed ? 'ALL TESTS PASSED' : 'SOME TESTS FAILED'}`);
+    console.log('='.repeat(60));
+
+    return allPassed;
+}
+
+async function runTests() {
+    const models = getThinkingModels();
+    let allPassed = true;
+
+    for (const { family, model } of models) {
+        console.log('\n');
+        const passed = await runTestsForModel(family, model);
+        if (!passed) allPassed = false;
+    }
+
+    console.log('\n' + '='.repeat(60));
+    console.log('FINAL RESULT');
+    console.log('='.repeat(60));
+    console.log(`Overall: ${allPassed ? 'ALL MODEL FAMILIES PASSED' : 'SOME MODEL FAMILIES FAILED'}`);
     console.log('='.repeat(60));
 
     process.exit(allPassed ? 0 : 1);