fix tests

allow openai to be used to name named compatible providers

config.coach-player.example.toml

@@ -11,12 +11,23 @@ model = "databricks-claude-sonnet-4"
 max_tokens = 4096
 temperature = 0.1
 use_oauth = true
+# cache_config = "ephemeral"  # Optional: Enable prompt caching for Claude models
+                              # Options: "ephemeral", "5minute", "1hour"
+                              # Reduces costs and latency for repeated prompts. Uses Anthropic's prompt caching with different TTLs.
+                                # The cache control will be automatically applied to:
+                                # - The system prompt at the start of each session
+                                # - Assistant responses after every 10 tool calls
+                                # - 5minute costs $3/mtok, more details below
+                                # https://docs.claude.com/en/docs/build-with-claude/prompt-caching#pricing
 
 [providers.anthropic]
 api_key = "your-anthropic-api-key"
 model = "claude-3-haiku-20240307"  # Using a faster model for player
 max_tokens = 4096
 temperature = 0.3  # Slightly higher temperature for more creative implementations
+# cache_config = "ephemeral"  # Optional: Enable prompt caching
+                              # Options: "ephemeral", "5minute", "1hour"
+                              # Reduces costs and latency for repeated prompts. Uses Anthropic's prompt caching with different TTLs.
 
 [agent]
 fallback_default_max_tokens = 8192

config.example.toml

@@ -14,6 +14,15 @@ max_tokens = 4096  # Per-request output limit (how many tokens the model can gen
                    # Note: This is different from max_context_length (total conversation history size)
 temperature = 0.1
 use_oauth = true
+# cache_config = "ephemeral"  # Optional: Enable prompt caching for Claude models on Databricks
+                              # Options: "ephemeral", "5minute", "1hour"
+                              # Reduces costs and latency for repeated prompts. Uses Anthropic's prompt caching with different TTLs.
+                                # The cache control will be automatically applied to:
+                                # - The system prompt at the start of each session
+                                # - Assistant responses after every 10 tool calls
+                                # - 5minute costs $3/mtok, more details below
+                                # https://docs.claude.com/en/docs/build-with-claude/prompt-caching#pricing
+
 
 # Multiple OpenAI-compatible providers can be configured with custom names
 # Each provider gets its own section under [providers.openai_compatible.<name>]

crates/g3-config/src/lib.rs

@@ -40,6 +40,8 @@ pub struct AnthropicConfig {
     pub model: String,
     pub max_tokens: Option<u32>,
     pub temperature: Option<f32>,
+    pub cache_config: Option<String>, // "ephemeral", "5minute", "1hour", or None to disable
+    pub enable_1m_context: Option<bool>, // Enable 1m context window (costs extra)
 }
 
 #[derive(Debug, Clone, Serialize, Deserialize)]

crates/g3-core/src/lib.rs

@@ -3,6 +3,8 @@ pub mod error_handling;
 pub mod project;
 pub mod task_result;
 pub mod ui_writer;
+
+use std::process::exit;
 pub use task_result::TaskResult;
 
 #[cfg(test)]
@@ -23,7 +25,7 @@ use anyhow::Result;
 use g3_computer_control::WebDriverController;
 use g3_config::Config;
 use g3_execution::CodeExecutor;
-use g3_providers::{CompletionRequest, Message, MessageRole, ProviderRegistry, Tool};
+use g3_providers::{CacheControl, CompletionRequest, Message, MessageRole, ProviderRegistry, Tool};
 #[allow(unused_imports)]
 use regex::Regex;
 use serde::{Deserialize, Serialize};
@@ -423,18 +425,12 @@ Format this as a detailed but concise summary that can be used to resume the con
         self.used_tokens = 0;
 
         // Add the summary as a system message
-        let summary_message = Message {
+        let summary_message = Message::new(MessageRole::System, format!("Previous conversation summary:\n\n{}", summary));
-            role: MessageRole::System,
-            content: format!("Previous conversation summary:\n\n{}", summary),
-        };
         self.add_message(summary_message);
 
         // Add the latest user message if provided
         if let Some(user_msg) = latest_user_message {
-            self.add_message(Message {
+            self.add_message(Message::new(MessageRole::User, user_msg));
-                role: MessageRole::User,
-                content: user_msg,
-            });
         }
 
         let new_chars: usize = self
@@ -756,6 +752,7 @@ pub struct Agent<W: UiWriter> {
     safaridriver_process: std::sync::Arc<tokio::sync::RwLock<Option<tokio::process::Child>>>,
     macax_controller:
         std::sync::Arc<tokio::sync::RwLock<Option<g3_computer_control::MacAxController>>>,
+    tool_call_count: usize,
 }
 
 impl<W: UiWriter> Agent<W> {
@@ -898,6 +895,8 @@ impl<W: UiWriter> Agent<W> {
                     Some(anthropic_config.model.clone()),
                     anthropic_config.max_tokens,
                     anthropic_config.temperature,
+                    anthropic_config.cache_config.clone(),
+                    anthropic_config.enable_1m_context,
                 )?;
                 providers.register(anthropic_provider);
             }
@@ -944,10 +943,7 @@ impl<W: UiWriter> Agent<W> {
 
         // If README content is provided, add it as the first system message
         if let Some(readme) = readme_content {
-            let readme_message = Message {
+            let readme_message = Message::new(MessageRole::System, readme);
-                role: MessageRole::System,
-                content: readme,
-            };
             context_window.add_message(readme_message);
         }
 
@@ -1003,9 +999,23 @@ impl<W: UiWriter> Agent<W> {
                     None
                 }))
             },
+            tool_call_count: 0,
         })
     }
 
+    /// Convert cache config string to CacheControl enum
+    fn parse_cache_control(cache_config: &str) -> Option<CacheControl> {
+        match cache_config {
+            "ephemeral" => Some(CacheControl::ephemeral()),
+            "5minute" => Some(CacheControl::five_minute()),
+            "1hour" => Some(CacheControl::one_hour()),
+            _ => {
+                warn!("Invalid cache_config value: '{}'. Valid values are: ephemeral, 5minute, 1hour", cache_config);
+                None
+            }
+        }
+    }
+
     fn get_configured_context_length(config: &Config, providers: &ProviderRegistry) -> Result<u32> {
         // First, check if there's a global max_context_length override in agent config
         if let Some(max_context_length) = config.agent.max_context_length {
@@ -1185,7 +1195,11 @@ impl<W: UiWriter> Agent<W> {
         // Only add system message if this is the first interaction (empty conversation history)
         if self.context_window.conversation_history.is_empty() {
             let provider = self.providers.get(None)?;
-            let system_prompt = if provider.has_native_tool_calling() {
+            let provider_has_native_tool_calling = provider.has_native_tool_calling();
+            let provider_name_for_system = provider.name().to_string();
+            drop(provider); // Drop provider reference to avoid borrowing issues
+            
+            let system_prompt = if provider_has_native_tool_calling {
                 // For native tool calling providers, use a more explicit system prompt
                 "You are G3, an AI programming agent of the same skill level as a seasoned engineer at a major technology company. You analyze given tasks and write code to achieve goals.
 
@@ -1493,18 +1507,26 @@ If you can complete it with 1-2 tool calls, skip TODO.
             }
 
             // Add system message to context window
-            let system_message = Message {
+            let system_message = {
-                role: MessageRole::System,
+                // Check if we should use cache control for system message
-                content: system_prompt,
+                if let Some(cache_config) = match provider_name_for_system.as_str() {
+                    "anthropic" => self.config.providers.anthropic.as_ref()
+                        .and_then(|c| c.cache_config.as_ref())
+                        .and_then(|config| Self::parse_cache_control(config)),
+                    _ => None,
+                } {
+                    let provider = self.providers.get(None)?;
+                    Message::with_cache_control_validated(MessageRole::System, system_prompt, cache_config, provider)
+                } else {
+                    Message::new(MessageRole::System, system_prompt)
+                }
             };
+
             self.context_window.add_message(system_message);
         }
 
         // Add user message to context window
-        let user_message = Message {
+        let user_message = Message::new(MessageRole::User, format!("Task: {}", description));
-            role: MessageRole::User,
-            content: format!("Task: {}", description),
-        };
         self.context_window.add_message(user_message);
 
         // Use the complete conversation history for the request
@@ -1512,6 +1534,9 @@ If you can complete it with 1-2 tool calls, skip TODO.
 
         // Check if provider supports native tool calling and add tools if so
         let provider = self.providers.get(None)?;
+        let provider_name = provider.name().to_string();
+        let has_native_tool_calling = provider.has_native_tool_calling();
+        let supports_cache_control = provider.supports_cache_control();
         let tools = if provider.has_native_tool_calling() {
             Some(Self::create_tool_definitions(
                 self.config.webdriver.enabled,
@@ -1521,9 +1546,10 @@ If you can complete it with 1-2 tool calls, skip TODO.
         } else {
             None
         };
+        drop(provider); // Drop the provider reference to avoid borrowing issues
 
         // Get max_tokens from provider configuration
-        let max_tokens = match provider.name() {
+        let max_tokens = match provider_name.as_str() {
             "databricks" => {
                 // Use the model's maximum limit for Databricks to allow large file generation
                 Some(32000)
@@ -1578,9 +1604,23 @@ If you can complete it with 1-2 tool calls, skip TODO.
         // Add assistant response to context window only if not empty
         // This prevents the "Skipping empty message" warning when only tools were executed
         if !response_content.trim().is_empty() {
-            let assistant_message = Message {
+            let assistant_message = {
-                role: MessageRole::Assistant,
+                // Check if we should use cache control (every 10 tool calls)
-                content: response_content.clone(),
+                if self.tool_call_count > 0 && self.tool_call_count % 10 == 0 {
+                    let provider = self.providers.get(None)?;
+                    if let Some(cache_config) = match provider.name() {
+                        "anthropic" => self.config.providers.anthropic.as_ref()
+                            .and_then(|c| c.cache_config.as_ref())
+                            .and_then(|config| Self::parse_cache_control(config)),
+                        _ => None,
+                    } {
+                        Message::with_cache_control_validated(MessageRole::Assistant, response_content.clone(), cache_config, provider)
+                    } else {
+                        Message::new(MessageRole::Assistant, response_content.clone())
+                    }
+                } else {
+                    Message::new(MessageRole::Assistant, response_content.clone())
+                }
             };
             self.context_window.add_message(assistant_message);
         } else {
@@ -1783,17 +1823,11 @@ If you can complete it with 1-2 tool calls, skip TODO.
             .join("\n\n");
 
         let summary_messages = vec![
-            Message {
+            Message::new(MessageRole::System, "You are a helpful assistant that creates concise summaries.".to_string()),
-                role: MessageRole::System,
+            Message::new(MessageRole::User, format!(
-                content: "You are a helpful assistant that creates concise summaries.".to_string(),
-            },
-            Message {
-                role: MessageRole::User,
-                content: format!(
                     "Based on this conversation history, {}\n\nConversation:\n{}",
                     summary_prompt, conversation_text
-                ),
+                )),
-            },
         ];
 
         let provider = self.providers.get(None)?;
@@ -2776,18 +2810,11 @@ If you can complete it with 1-2 tool calls, skip TODO.
                 .join("\n\n");
 
             let summary_messages = vec![
-                Message {
+                Message::new(MessageRole::System, "You are a helpful assistant that creates concise summaries.".to_string()),
-                    role: MessageRole::System,
+                Message::new(MessageRole::User, format!(
-                    content: "You are a helpful assistant that creates concise summaries."
-                        .to_string(),
-                },
-                Message {
-                    role: MessageRole::User,
-                    content: format!(
                         "Based on this conversation history, {}\n\nConversation:\n{}",
                         summary_prompt, conversation_text
-                    ),
+                )),
-                },
             ];
 
             let provider = self.providers.get(None)?;
@@ -3273,29 +3300,20 @@ If you can complete it with 1-2 tool calls, skip TODO.
                             // Add the tool call and result to the context window using RAW unfiltered content
                             // This ensures the log file contains the true raw content including JSON tool calls
                             let tool_message = if !raw_content_for_log.trim().is_empty() {
-                                Message {
+                                Message::new(MessageRole::Assistant, format!(
-                                    role: MessageRole::Assistant,
-                                    content: format!(
                                         "{}\n\n{{\"tool\": \"{}\", \"args\": {}}}",
                                         raw_content_for_log.trim(),
                                         tool_call.tool,
                                         tool_call.args
-                                    ),
+                                ))
-                                }
                             } else {
                                 // No text content before tool call, just include the tool call
-                                Message {
+                                Message::new(MessageRole::Assistant, format!(
-                                    role: MessageRole::Assistant,
-                                    content: format!(
                                         "{{\"tool\": \"{}\", \"args\": {}}}",
                                         tool_call.tool, tool_call.args
-                                    ),
+                                ))
-                                }
-                            };
-                            let result_message = Message {
-                                role: MessageRole::User,
-                                content: format!("Tool result: {}", tool_result),
                             };
+                            let result_message = Message::new(MessageRole::User, format!("Tool result: {}", tool_result));
 
                             self.context_window.add_message(tool_message);
                             self.context_window.add_message(result_message);
@@ -3304,7 +3322,8 @@ If you can complete it with 1-2 tool calls, skip TODO.
                             request.messages = self.context_window.conversation_history.clone();
 
                             // Ensure tools are included for native providers in subsequent iterations
-                            if provider.has_native_tool_calling() {
+                            let provider_for_tools = self.providers.get(None)?;
+                            if provider_for_tools.has_native_tool_calling() {
                                 request.tools = Some(Self::create_tool_definitions(
                                     self.config.webdriver.enabled,
                                     self.config.macax.enabled,
@@ -3635,9 +3654,23 @@ If you can complete it with 1-2 tool calls, skip TODO.
                         .replace("<</SYS>>", "");
 
                     if !raw_clean.trim().is_empty() {
-                        let assistant_message = Message {
+                        let assistant_message = {
-                            role: MessageRole::Assistant,
+                            // Check if we should use cache control (every 10 tool calls)
-                            content: raw_clean,
+                            if self.tool_call_count > 0 && self.tool_call_count % 10 == 0 {
+                                let provider = self.providers.get(None)?;
+                                if let Some(cache_config) = match provider.name() {
+                                    "anthropic" => self.config.providers.anthropic.as_ref()
+                                        .and_then(|c| c.cache_config.as_ref())
+                                        .and_then(|config| Self::parse_cache_control(config)),
+                                    _ => None,
+                                } {
+                                    Message::with_cache_control_validated(MessageRole::Assistant, raw_clean, cache_config, provider)
+                                } else {
+                                    Message::new(MessageRole::Assistant, raw_clean)
+                                }
+                            } else {
+                                Message::new(MessageRole::Assistant, raw_clean)
+                            }
                         };
                         self.context_window.add_message(assistant_message);
                     }
@@ -3679,7 +3712,10 @@ If you can complete it with 1-2 tool calls, skip TODO.
         Ok(TaskResult::new(final_response, self.context_window.clone()))
     }
 
-    pub async fn execute_tool(&self, tool_call: &ToolCall) -> Result<String> {
+    pub async fn execute_tool(&mut self, tool_call: &ToolCall) -> Result<String> {
+        // Increment tool call count
+        self.tool_call_count += 1;
+        
         debug!("=== EXECUTING TOOL ===");
         debug!("Tool name: {}", tool_call.tool);
         debug!("Tool args (raw): {:?}", tool_call.args);

crates/g3-core/src/task_result_comprehensive_tests.rs

@@ -6,14 +6,10 @@ use std::sync::Arc;
 fn test_task_result_basic_functionality() {
     // Create a context window with some messages
     let mut context = ContextWindow::new(10000);
-    context.add_message(Message {
+    context.add_message(Message::new(MessageRole::User, "Test message 1".to_string())
-        role: MessageRole::User,
+    );
-        content: "Test message 1".to_string(),
+    context.add_message(Message::new(MessageRole::Assistant, "Response 1".to_string())
-    });
+    );
-    context.add_message(Message {
-        role: MessageRole::Assistant,
-        content: "Response 1".to_string(),
-    });
     
     // Create a TaskResult
     let response = "This is the response\n\nFinal output block".to_string();
@@ -100,10 +96,7 @@ fn test_context_window_preservation() {
     
     // Add some messages
     for i in 0..5 {
-        context.add_message(Message {
+        context.add_message(Message::new(if i % 2 == 0 { MessageRole::User } else { MessageRole::Assistant }, format!("Message {}", i)));
-            role: if i % 2 == 0 { MessageRole::User } else { MessageRole::Assistant },
-            content: format!("Message {}", i),
-        });
     }
     
     // Create TaskResult

crates/g3-core/tests/test_context_thinning.rs

@@ -46,10 +46,10 @@ fn test_thin_context_basic() {
     // Add some messages to the first third
     for i in 0..9 {
         if i % 2 == 0 {
-            context.add_message(Message {
+            context.add_message(Message::new(
-                role: MessageRole::Assistant,
+                MessageRole::Assistant,
-                content: format!("Assistant message {}", i),
+                format!("Assistant message {}", i),
-            });
+            ));
         } else {
             // Add tool results with varying sizes
             let content = if i == 1 {
@@ -63,10 +63,10 @@ fn test_thin_context_basic() {
                 format!("Tool result: small result {}", i)
             };
             
-            context.add_message(Message {
+            context.add_message(Message::new(
-                role: MessageRole::User,
+                MessageRole::User,
                 content,
-            });
+            ));
         }
     }
     
@@ -98,10 +98,10 @@ fn test_thin_write_file_tool_calls() {
     let mut context = ContextWindow::new(10000);
     
     // Add some messages including a write_file tool call with large content
-    context.add_message(Message {
+    context.add_message(Message::new(
-        role: MessageRole::User,
+        MessageRole::User,
-        content: "Please create a large file".to_string(),
+        "Please create a large file".to_string(),
-    });
+    ));
     
     // Add an assistant message with a write_file tool call containing large content
     let large_content = "x".repeat(1500);
@@ -109,22 +109,22 @@ fn test_thin_write_file_tool_calls() {
         r#"{{"tool": "write_file", "args": {{"file_path": "test.txt", "content": "{}"}}}}"#,
         large_content
     );
-    context.add_message(Message {
+    context.add_message(Message::new(
-        role: MessageRole::Assistant,
+        MessageRole::Assistant,
-        content: format!("I'll create that file.\n\n{}", tool_call_json),
+        format!("I'll create that file.\n\n{}", tool_call_json),
-    });
+    ));
     
-    context.add_message(Message {
+    context.add_message(Message::new(
-        role: MessageRole::User,
+        MessageRole::User,
-        content: "Tool result: ✅ Successfully wrote 1500 lines".to_string(),
+        "Tool result: ✅ Successfully wrote 1500 lines".to_string(),
-    });
+    ));
     
     // Add more messages to ensure we have enough for "first third" logic
     for i in 0..6 {
-        context.add_message(Message {
+        context.add_message(Message::new(
-            role: MessageRole::Assistant,
+            MessageRole::Assistant,
-            content: format!("Response {}", i),
+            format!("Response {}", i),
-        });
+        ));
     }
     
     // Trigger thinning at 50%
@@ -154,10 +154,10 @@ fn test_thin_str_replace_tool_calls() {
     let mut context = ContextWindow::new(10000);
     
     // Add some messages including a str_replace tool call with large diff
-    context.add_message(Message {
+    context.add_message(Message::new(
-        role: MessageRole::User,
+        MessageRole::User,
-        content: "Please update the file".to_string(),
+        "Please update the file".to_string(),
-    });
+    ));
     
     // Add an assistant message with a str_replace tool call containing large diff
     let large_diff = format!("--- old\n{}\n+++ new\n{}", "-old line\n".repeat(100), "+new line\n".repeat(100));
@@ -165,22 +165,22 @@ fn test_thin_str_replace_tool_calls() {
         r#"{{"tool": "str_replace", "args": {{"file_path": "test.txt", "diff": "{}"}}}}"#,
         large_diff.replace('\n', "\\n")
     );
-    context.add_message(Message {
+    context.add_message(Message::new(
-        role: MessageRole::Assistant,
+        MessageRole::Assistant,
-        content: format!("I'll update that file.\n\n{}", tool_call_json),
+        format!("I'll update that file.\n\n{}", tool_call_json),
-    });
+    ));
     
-    context.add_message(Message {
+    context.add_message(Message::new(
-        role: MessageRole::User,
+        MessageRole::User,
-        content: "Tool result: ✅ applied unified diff".to_string(),
+        "Tool result: ✅ applied unified diff".to_string(),
-    });
+    ));
     
     // Add more messages to ensure we have enough for "first third" logic
     for i in 0..6 {
-        context.add_message(Message {
+        context.add_message(Message::new(
-            role: MessageRole::Assistant,
+            MessageRole::Assistant,
-            content: format!("Response {}", i),
+            format!("Response {}", i),
-        });
+        ));
     }
     
     // Trigger thinning at 50%
@@ -212,10 +212,10 @@ fn test_thin_context_no_large_results() {
     
     // Add only small messages
     for i in 0..9 {
-        context.add_message(Message {
+        context.add_message(Message::new(
-            role: MessageRole::User,
+            MessageRole::User,
-            content: format!("Tool result: small {}", i),
+            format!("Tool result: small {}", i),
-        });
+        ));
     }
     
     context.used_tokens = 5000;
@@ -244,7 +244,7 @@ fn test_thin_context_only_affects_first_third() {
             MessageRole::Assistant
         };
         
-        context.add_message(Message { role, content });
+        context.add_message(Message::new(role, content));
     }
     
     context.used_tokens = 5000;

crates/g3-core/tests/test_todo_context_thinning.rs

@@ -8,27 +8,18 @@ fn test_todo_read_results_not_thinned() {
     let mut context = ContextWindow::new(10000);
     
     // Add a todo_read tool call
-    context.add_message(Message {
+    context.add_message(Message::new(MessageRole::Assistant, r#"{"tool": "todo_read", "args": {}}"#.to_string()));
-        role: MessageRole::Assistant,
-        content: r#"{"tool": "todo_read", "args": {}}"#.to_string(),
-    });
     
     // Add a large TODO result (> 500 chars)
     let large_todo_result = format!(
         "Tool result: 📝 TODO list:\n{}",
         "- [ ] Task with long description\n".repeat(50)
     );
-    context.add_message(Message {
+    context.add_message(Message::new(MessageRole::User, large_todo_result.clone()));
-        role: MessageRole::User,
-        content: large_todo_result.clone(),
-    });
     
     // Add more messages to ensure we have enough for "first third" logic
     for i in 0..6 {
-        context.add_message(Message {
+        context.add_message(Message::new(MessageRole::Assistant, format!("Response {}", i)))
-            role: MessageRole::Assistant,
-            content: format!("Response {}", i),
-        });
     }
     
     // Trigger thinning at 50%
@@ -65,27 +56,18 @@ fn test_todo_write_results_not_thinned() {
     
     // Add a todo_write tool call
     let large_content = "- [ ] Task\n".repeat(100);
-    context.add_message(Message {
+    context.add_message(Message::new(MessageRole::Assistant, format!(r#"{{"tool": "todo_write", "args": {{"content": "{}"}}}}"#, large_content)));
-        role: MessageRole::Assistant,
-        content: format!(r#"{{"tool": "todo_write", "args": {{"content": "{}"}}}}"#, large_content),
-    });
     
     // Add a large TODO write result
     let large_todo_result = format!(
         "Tool result: ✅ TODO list updated ({} chars) and saved to todo.g3.md",
         large_content.len()
     );
-    context.add_message(Message {
+    context.add_message(Message::new(MessageRole::User, large_todo_result.clone()));
-        role: MessageRole::User,
-        content: large_todo_result.clone(),
-    });
     
     // Add more messages
     for i in 0..6 {
-        context.add_message(Message {
+        context.add_message(Message::new(MessageRole::Assistant, format!("Response {}", i)))
-            role: MessageRole::Assistant,
-            content: format!("Response {}", i),
-        });
     }
     
     // Trigger thinning at 50%
@@ -119,24 +101,15 @@ fn test_non_todo_results_still_thinned() {
     let mut context = ContextWindow::new(10000);
     
     // Add a non-TODO tool call (e.g., read_file)
-    context.add_message(Message {
+    context.add_message(Message::new(MessageRole::Assistant, r#"{"tool": "read_file", "args": {"file_path": "test.txt"}}"#.to_string()));
-        role: MessageRole::Assistant,
-        content: r#"{"tool": "read_file", "args": {"file_path": "test.txt"}}"#.to_string(),
-    });
     
     // Add a large read_file result (> 500 chars)
     let large_result = format!("Tool result: {}", "x".repeat(1500));
-    context.add_message(Message {
+    context.add_message(Message::new(MessageRole::User, large_result));
-        role: MessageRole::User,
-        content: large_result,
-    });
     
     // Add more messages
     for i in 0..6 {
-        context.add_message(Message {
+        context.add_message(Message::new(MessageRole::Assistant, format!("Response {}", i)))
-            role: MessageRole::Assistant,
-            content: format!("Response {}", i),
-        });
     }
     
     // Trigger thinning at 50%
@@ -172,27 +145,18 @@ fn test_todo_read_with_spaces_in_tool_name() {
     let mut context = ContextWindow::new(10000);
     
     // Add a todo_read tool call with spaces (JSON formatting variation)
-    context.add_message(Message {
+    context.add_message(Message::new(MessageRole::Assistant, r#"{"tool": "todo_read", "args": {}}"#.to_string()));
-        role: MessageRole::Assistant,
-        content: r#"{"tool": "todo_read", "args": {}}"#.to_string(),
-    });
     
     // Add a large TODO result
     let large_todo_result = format!(
         "Tool result: 📝 TODO list:\n{}",
         "- [ ] Task\n".repeat(50)
     );
-    context.add_message(Message {
+    context.add_message(Message::new(MessageRole::User, large_todo_result.clone()));
-        role: MessageRole::User,
-        content: large_todo_result.clone(),
-    });
     
     // Add more messages
     for i in 0..6 {
-        context.add_message(Message {
+        context.add_message(Message::new(MessageRole::Assistant, format!("Response {}", i)))
-            role: MessageRole::Assistant,
-            content: format!("Response {}", i),
-        });
     }
     
     // Trigger thinning

crates/g3-core/tests/test_todo_persistence.rs

@@ -27,7 +27,7 @@ fn get_todo_path(temp_dir: &TempDir) -> PathBuf {
 #[serial]
 async fn test_todo_write_creates_file() {
     let temp_dir = TempDir::new().unwrap();
-    let agent = create_test_agent_in_dir(&temp_dir).await;
+    let mut agent = create_test_agent_in_dir(&temp_dir).await;
     let todo_path = get_todo_path(&temp_dir);
     
     // Initially, todo.g3.md should not exist
@@ -67,7 +67,7 @@ async fn test_todo_read_from_file() {
     fs::write(&todo_path, test_content).unwrap();
     
     // Create agent (should load from file)
-    let agent = create_test_agent_in_dir(&temp_dir).await;
+    let mut agent = create_test_agent_in_dir(&temp_dir).await;
     
     // Create a tool call to read TODO
     let tool_call = g3_core::ToolCall {
@@ -88,7 +88,7 @@ async fn test_todo_read_from_file() {
 #[serial]
 async fn test_todo_read_empty_file() {
     let temp_dir = TempDir::new().unwrap();
-    let agent = create_test_agent_in_dir(&temp_dir).await;
+    let mut agent = create_test_agent_in_dir(&temp_dir).await;
     
     // Create a tool call to read TODO (file doesn't exist)
     let tool_call = g3_core::ToolCall {
@@ -111,7 +111,7 @@ async fn test_todo_persistence_across_agents() {
     
     // Agent 1: Write TODO
     {
-        let agent = create_test_agent_in_dir(&temp_dir).await;
+        let mut agent = create_test_agent_in_dir(&temp_dir).await;
         let tool_call = g3_core::ToolCall {
             tool: "todo_write".to_string(),
             args: serde_json::json!({
@@ -126,7 +126,7 @@ async fn test_todo_persistence_across_agents() {
     
     // Agent 2: Read TODO (new agent instance)
     {
-        let agent = create_test_agent_in_dir(&temp_dir).await;
+        let mut agent = create_test_agent_in_dir(&temp_dir).await;
         let tool_call = g3_core::ToolCall {
             tool: "todo_read".to_string(),
             args: serde_json::json!({}),
@@ -143,7 +143,7 @@ async fn test_todo_persistence_across_agents() {
 #[serial]
 async fn test_todo_update_preserves_file() {
     let temp_dir = TempDir::new().unwrap();
-    let agent = create_test_agent_in_dir(&temp_dir).await;
+    let mut agent = create_test_agent_in_dir(&temp_dir).await;
     let todo_path = get_todo_path(&temp_dir);
     
     // Write initial TODO
@@ -173,7 +173,7 @@ async fn test_todo_update_preserves_file() {
 #[serial]
 async fn test_todo_handles_large_content() {
     let temp_dir = TempDir::new().unwrap();
-    let agent = create_test_agent_in_dir(&temp_dir).await;
+    let mut agent = create_test_agent_in_dir(&temp_dir).await;
     let todo_path = get_todo_path(&temp_dir);
     
     // Create a large TODO (but under the 50k limit)
@@ -202,7 +202,7 @@ async fn test_todo_handles_large_content() {
 #[serial]
 async fn test_todo_respects_size_limit() {
     let temp_dir = TempDir::new().unwrap();
-    let agent = create_test_agent_in_dir(&temp_dir).await;
+    let mut agent = create_test_agent_in_dir(&temp_dir).await;
     
     // Create content that exceeds the default 50k limit
     let huge_content = "x".repeat(60_000);
@@ -232,7 +232,7 @@ async fn test_todo_agent_initialization_loads_file() {
     fs::write(&todo_path, initial_content).unwrap();
     
     // Create agent - should load the file during initialization
-    let agent = create_test_agent_in_dir(&temp_dir).await;
+    let mut agent = create_test_agent_in_dir(&temp_dir).await;
     
     // Read TODO - should return the pre-existing content
     let tool_call = g3_core::ToolCall {
@@ -248,7 +248,7 @@ async fn test_todo_agent_initialization_loads_file() {
 #[serial]
 async fn test_todo_handles_unicode_content() {
     let temp_dir = TempDir::new().unwrap();
-    let agent = create_test_agent_in_dir(&temp_dir).await;
+    let mut agent = create_test_agent_in_dir(&temp_dir).await;
     let todo_path = get_todo_path(&temp_dir);
     
     // Create TODO with unicode characters
@@ -283,7 +283,7 @@ async fn test_todo_handles_unicode_content() {
 #[serial]
 async fn test_todo_empty_content_creates_empty_file() {
     let temp_dir = TempDir::new().unwrap();
-    let agent = create_test_agent_in_dir(&temp_dir).await;
+    let mut agent = create_test_agent_in_dir(&temp_dir).await;
     let todo_path = get_todo_path(&temp_dir);
     
     // Write empty TODO
@@ -306,7 +306,7 @@ async fn test_todo_empty_content_creates_empty_file() {
 #[serial]
 async fn test_todo_whitespace_only_content() {
     let temp_dir = TempDir::new().unwrap();
-    let agent = create_test_agent_in_dir(&temp_dir).await;
+    let mut agent = create_test_agent_in_dir(&temp_dir).await;
     
     // Write whitespace-only TODO
     let tool_call = g3_core::ToolCall {

crates/g3-providers/src/anthropic.rs

@@ -21,22 +21,18 @@
 //!     // Create the provider with your API key
 //!     let provider = AnthropicProvider::new(
 //!         "your-api-key".to_string(),
-//!         Some("claude-3-5-sonnet-20241022".to_string()), // Optional: defaults to claude-3-5-sonnet-20241022
+//!         Some("claude-3-5-sonnet-20241022".to_string()),
-//!         Some(4096),  // Optional: max tokens
+//!         Some(4096),
-//!         Some(0.1),   // Optional: temperature
+//!         Some(0.1),
+//!         None, // cache_config
+//!         None, // enable_1m_context
 //!     )?;
 //!
 //!     // Create a completion request
 //!     let request = CompletionRequest {
 //!         messages: vec![
-//!             Message {
+//!             Message::new(MessageRole::System, "You are a helpful assistant.".to_string()),
-//!                 role: MessageRole::System,
+//!             Message::new(MessageRole::User, "Hello! How are you?".to_string()),
-//!                 content: "You are a helpful assistant.".to_string(),
-//!             },
-//!             Message {
-//!                 role: MessageRole::User,
-//!                 content: "Hello! How are you?".to_string(),
-//!             },
 //!         ],
 //!         max_tokens: Some(1000),
 //!         temperature: Some(0.7),
@@ -62,15 +58,16 @@
 //! async fn main() -> anyhow::Result<()> {
 //!     let provider = AnthropicProvider::new(
 //!         "your-api-key".to_string(),
-//!         None, None, None,
+//!         None,
+//!         None,
+//!         None,
+//!         None, // cache_config
+//!         None, // enable_1m_context
 //!     )?;
 //!
 //!     let request = CompletionRequest {
 //!         messages: vec![
-//!             Message {
+//!             Message::new(MessageRole::User, "Write a short story about a robot.".to_string()),
-//!                 role: MessageRole::User,
-//!                 content: "Write a short story about a robot.".to_string(),
-//!             },
 //!         ],
 //!         max_tokens: Some(1000),
 //!         temperature: Some(0.7),
@@ -123,6 +120,8 @@ pub struct AnthropicProvider {
     model: String,
     max_tokens: u32,
     temperature: f32,
+    cache_config: Option<String>,
+    enable_1m_context: bool,
 }
 
 impl AnthropicProvider {
@@ -131,6 +130,8 @@ impl AnthropicProvider {
         model: Option<String>,
         max_tokens: Option<u32>,
         temperature: Option<f32>,
+        cache_config: Option<String>,
+        enable_1m_context: Option<bool>,
     ) -> Result<Self> {
         let client = Client::builder()
             .timeout(Duration::from_secs(300))
@@ -147,6 +148,8 @@ impl AnthropicProvider {
             model,
             max_tokens: max_tokens.unwrap_or(4096),
             temperature: temperature.unwrap_or(0.1),
+            cache_config,
+            enable_1m_context: enable_1m_context.unwrap_or(false),
         })
     }
 
@@ -156,9 +159,12 @@ impl AnthropicProvider {
             .post(ANTHROPIC_API_URL)
             .header("x-api-key", &self.api_key)
             .header("anthropic-version", ANTHROPIC_VERSION)
-            // Anthropic beta 1m context window. Enable if needed. It costs extra, so check first.
-            // .header("anthropic-beta", "context-1m-2025-08-07")
             .header("content-type", "application/json");
+        
+        if self.enable_1m_context {
+            builder = builder.header("anthropic-beta", "context-1m-2025-08-07");
+        }
+        
         if streaming {
             builder = builder.header("accept", "text/event-stream");
         }
@@ -166,6 +172,11 @@ impl AnthropicProvider {
         builder
     }
 
+    fn convert_cache_control(cache_control: &crate::CacheControl) -> crate::CacheControl {
+        // Anthropic uses the same format, so just clone it
+        cache_control.clone()
+    }
+
     fn convert_tools(&self, tools: &[Tool]) -> Vec<AnthropicTool> {
         tools
             .iter()
@@ -214,6 +225,8 @@ impl AnthropicProvider {
                         role: "user".to_string(),
                         content: vec![AnthropicContent::Text {
                             text: message.content.clone(),
+                            cache_control: message.cache_control.as_ref()
+                                .map(Self::convert_cache_control),
                         }],
                     });
                 }
@@ -222,6 +235,8 @@ impl AnthropicProvider {
                         role: "assistant".to_string(),
                         content: vec![AnthropicContent::Text {
                             text: message.content.clone(),
+                            cache_control: message.cache_control.as_ref()
+                                .map(Self::convert_cache_control),
                         }],
                     });
                 }
@@ -564,7 +579,7 @@ impl LLMProvider for AnthropicProvider {
             .content
             .iter()
             .filter_map(|c| match c {
-                AnthropicContent::Text { text } => Some(text.as_str()),
+                AnthropicContent::Text { text, .. } => Some(text.as_str()),
                 _ => None,
             })
             .collect::<Vec<_>>()
@@ -658,6 +673,11 @@ impl LLMProvider for AnthropicProvider {
         // Claude models support native tool calling
         true
     }
+    
+    fn supports_cache_control(&self) -> bool {
+        // Anthropic supports cache control
+        true
+    }
 }
 
 // Anthropic API request/response structures
@@ -701,7 +721,11 @@ struct AnthropicMessage {
 #[serde(tag = "type")]
 enum AnthropicContent {
     #[serde(rename = "text")]
-    Text { text: String },
+    Text { 
+        text: String,
+        #[serde(skip_serializing_if = "Option::is_none")]
+        cache_control: Option<crate::CacheControl>,
+    },
     #[serde(rename = "tool_use")]
     ToolUse {
         id: String,
@@ -771,21 +795,14 @@ mod tests {
             None,
             None,
             None,
+            None,
+            None,
         ).unwrap();
 
         let messages = vec![
-            Message {
+            Message::new(MessageRole::System, "You are a helpful assistant.".to_string()),
-                role: MessageRole::System,
+            Message::new(MessageRole::User, "Hello!".to_string()),
-                content: "You are a helpful assistant.".to_string(),
+            Message::new(MessageRole::Assistant, "Hi there!".to_string()),
-            },
-            Message {
-                role: MessageRole::User,
-                content: "Hello!".to_string(),
-            },
-            Message {
-                role: MessageRole::Assistant,
-                content: "Hi there!".to_string(),
-            },
         ];
 
         let (system, anthropic_messages) = provider.convert_messages(&messages).unwrap();
@@ -803,14 +820,11 @@ mod tests {
             Some("claude-3-haiku-20240307".to_string()),
             Some(1000),
             Some(0.5),
+            None,
+            None,
         ).unwrap();
 
-        let messages = vec![
+        let messages = vec![Message::new(MessageRole::User, "Test message".to_string())];
-            Message {
-                role: MessageRole::User,
-                content: "Test message".to_string(),
-            },
-        ];
 
         let request_body = provider
             .create_request_body(&messages, None, false, 1000, 0.5)
@@ -831,6 +845,8 @@ mod tests {
             None,
             None,
             None,
+            None,
+            None,
         ).unwrap();
 
         let tools = vec![
@@ -859,4 +875,48 @@ mod tests {
         assert!(anthropic_tools[0].input_schema.required.is_some());
         assert_eq!(anthropic_tools[0].input_schema.required.as_ref().unwrap()[0], "location");
     }
+
+    #[test]
+    fn test_cache_control_serialization() {
+        let provider = AnthropicProvider::new(
+            "test-key".to_string(),
+            None,
+            None,
+            None,
+            None,
+            None,
+        ).unwrap();
+
+        // Test message WITHOUT cache_control
+        let messages_without = vec![Message::new(MessageRole::User, "Hello".to_string())];
+        let (_, anthropic_messages_without) = provider.convert_messages(&messages_without).unwrap();
+        let json_without = serde_json::to_string(&anthropic_messages_without).unwrap();
+        
+        println!("Anthropic JSON without cache_control: {}", json_without);
+        // Check if cache_control appears in the JSON
+        if json_without.contains("cache_control") {
+            println!("WARNING: JSON contains 'cache_control' field when not configured!");
+            assert!(!json_without.contains("\"cache_control\":null"), 
+                    "JSON should not contain 'cache_control: null'");
+        }
+
+        // Test message WITH cache_control
+        let messages_with = vec![Message::with_cache_control(
+            MessageRole::User,
+            "Hello".to_string(),
+            crate::CacheControl::ephemeral(),
+        )];
+        let (_, anthropic_messages_with) = provider.convert_messages(&messages_with).unwrap();
+        let json_with = serde_json::to_string(&anthropic_messages_with).unwrap();
+        
+        println!("Anthropic JSON with cache_control: {}", json_with);
+        assert!(json_with.contains("cache_control"), 
+                "JSON should contain 'cache_control' field when configured");
+        assert!(json_with.contains("ephemeral"), 
+                "JSON should contain 'ephemeral' type");
+        
+        // The key assertion: when cache_control is None, it should not appear in JSON
+        assert!(!json_without.contains("cache_control") || !json_without.contains("null"),
+                "JSON should not contain 'cache_control' field or null values when not configured");
+    }
 }

crates/g3-providers/src/databricks.rs

@@ -39,10 +39,7 @@
 //!     // Create a completion request
 //!     let request = CompletionRequest {
 //!         messages: vec![
-//!             Message {
+//!             Message::new(MessageRole::User, "Hello! How are you?".to_string()),
-//!                 role: MessageRole::User,
-//!                 content: "Hello! How are you?".to_string(),
-//!             },
 //!         ],
 //!         max_tokens: Some(1000),
 //!         temperature: Some(0.7),
@@ -251,9 +248,12 @@ impl DatabricksProvider {
                 MessageRole::Assistant => "assistant",
             };
 
+            // Always use simple string format (Databricks doesn't support cache_control)
+            let content = serde_json::Value::String(message.content.clone());
+
             databricks_messages.push(DatabricksMessage {
                 role: role.to_string(),
-                content: Some(message.content.clone()),
+                content: Some(content),
                 tool_calls: None, // Only used in responses, not requests
             });
         }
@@ -864,8 +864,22 @@ impl LLMProvider for DatabricksProvider {
         let content = databricks_response
             .choices
             .first()
-            .and_then(|choice| choice.message.content.as_ref())
+            .and_then(|choice| {
-            .cloned()
+                choice.message.content.as_ref().map(|c| {
+                    // Handle both string and array formats
+                    if let Some(s) = c.as_str() {
+                        s.to_string()
+                    } else if let Some(arr) = c.as_array() {
+                        // Extract text from content blocks
+                        arr.iter()
+                            .filter_map(|block| block.get("text").and_then(|t| t.as_str()))
+                            .collect::<Vec<_>>()
+                            .join("")
+                    } else {
+                        String::new()
+                    }
+                })
+            })
             .unwrap_or_default();
 
         // Check if there are tool calls in the response
@@ -1037,6 +1051,10 @@ impl LLMProvider for DatabricksProvider {
         // This includes Claude, Llama, DBRX, and most other models on the platform
         true
     }
+    
+    fn supports_cache_control(&self) -> bool {
+        false
+    }
 }
 
 // Databricks API request/response structures
@@ -1067,7 +1085,8 @@ struct DatabricksFunction {
 #[derive(Debug, Serialize, Deserialize)]
 struct DatabricksMessage {
     role: String,
-    content: Option<String>, // Make content optional since tool calls might not have content
+    #[serde(skip_serializing_if = "Option::is_none")]
+    content: Option<serde_json::Value>, // Can be string or array of content blocks
     #[serde(skip_serializing_if = "Option::is_none")]
     tool_calls: Option<Vec<DatabricksToolCall>>, // Add tool_calls field for responses
 }
@@ -1154,18 +1173,9 @@ mod tests {
         .unwrap();
 
         let messages = vec![
-            Message {
+            Message::new(MessageRole::System, "You are a helpful assistant.".to_string()),
-                role: MessageRole::System,
+            Message::new(MessageRole::User, "Hello!".to_string()),
-                content: "You are a helpful assistant.".to_string(),
+            Message::new(MessageRole::Assistant, "Hi there!".to_string()),
-            },
-            Message {
-                role: MessageRole::User,
-                content: "Hello!".to_string(),
-            },
-            Message {
-                role: MessageRole::Assistant,
-                content: "Hi there!".to_string(),
-            },
         ];
 
         let databricks_messages = provider.convert_messages(&messages).unwrap();
@@ -1187,10 +1197,7 @@ mod tests {
         )
         .unwrap();
 
-        let messages = vec![Message {
+        let messages = vec![Message::new(MessageRole::User, "Test message".to_string())];
-            role: MessageRole::User,
-            content: "Test message".to_string(),
-        }];
 
         let request_body = provider
             .create_request_body(&messages, None, false, 1000, 0.5)
@@ -1273,4 +1280,62 @@ mod tests {
         assert!(llama_provider.has_native_tool_calling());
         assert!(dbrx_provider.has_native_tool_calling());
     }
+
+    #[test]
+    fn test_cache_control_serialization() {
+        let provider = DatabricksProvider::from_token(
+            "https://test.databricks.com".to_string(),
+            "test-token".to_string(),
+            "databricks-claude-sonnet-4".to_string(),
+            None,
+            None,
+        )
+        .unwrap();
+
+        // Test message WITHOUT cache_control
+        let messages_without = vec![Message::new(MessageRole::User, "Hello".to_string())];
+        let databricks_messages_without = provider.convert_messages(&messages_without).unwrap();
+        let json_without = serde_json::to_string(&databricks_messages_without).unwrap();
+        
+        println!("JSON without cache_control: {}", json_without);
+        assert!(!json_without.contains("cache_control"), 
+                "JSON should not contain 'cache_control' field when not configured");
+
+        // Test message WITH cache_control - should still NOT include it (Databricks doesn't support it)
+        let messages_with = vec![Message::with_cache_control(
+            MessageRole::User,
+            "Hello".to_string(),
+            crate::CacheControl::ephemeral(),
+        )];
+        let databricks_messages_with = provider.convert_messages(&messages_with).unwrap();
+        let json_with = serde_json::to_string(&databricks_messages_with).unwrap();
+        
+        println!("JSON with cache_control: {}", json_with);
+        assert!(!json_with.contains("cache_control"), 
+                "JSON should NOT contain 'cache_control' field - Databricks doesn't support it");
+    }
+
+    #[test]
+    fn test_databricks_does_not_support_cache_control() {
+        let claude_provider = DatabricksProvider::from_token(
+            "https://test.databricks.com".to_string(),
+            "test-token".to_string(),
+            "databricks-claude-sonnet-4".to_string(),
+            None,
+            None,
+        )
+        .unwrap();
+
+        let llama_provider = DatabricksProvider::from_token(
+            "https://test.databricks.com".to_string(),
+            "test-token".to_string(),
+            "databricks-meta-llama-3-3-70b-instruct".to_string(),
+            None,
+            None,
+        )
+        .unwrap();
+
+        assert!(!claude_provider.supports_cache_control(), "Databricks should not support cache_control even for Claude models");
+        assert!(!llama_provider.supports_cache_control(), "Databricks should not support cache_control for Llama models");
+    }
 }

crates/g3-providers/src/lib.rs

@@ -21,6 +21,11 @@ pub trait LLMProvider: Send + Sync {
     fn has_native_tool_calling(&self) -> bool {
         false
     }
+    
+    /// Check if the provider supports cache control
+    fn supports_cache_control(&self) -> bool {
+        false
+    }
 }
 
 #[derive(Debug, Clone, Serialize, Deserialize)]
@@ -32,10 +37,40 @@ pub struct CompletionRequest {
     pub tools: Option<Vec<Tool>>,
 }
 
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct CacheControl {
+    #[serde(rename = "type")]
+    pub cache_type: CacheType,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub ttl: Option<String>,
+}
+
+#[derive(Debug, Clone, Serialize, Deserialize, PartialEq)]
+#[serde(rename_all = "lowercase")]
+pub enum CacheType {
+    Ephemeral,
+}
+
+impl CacheControl {
+    pub fn ephemeral() -> Self {
+        Self { cache_type: CacheType::Ephemeral, ttl: None }
+    }
+    
+    pub fn five_minute() -> Self {
+        Self { cache_type: CacheType::Ephemeral, ttl: Some("5m".to_string()) }
+    }
+    
+    pub fn one_hour() -> Self {
+        Self { cache_type: CacheType::Ephemeral, ttl: Some("1h".to_string()) }
+    }
+}
+
 #[derive(Debug, Clone, Serialize, Deserialize)]
 pub struct Message {
     pub role: MessageRole,
     pub content: String,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub cache_control: Option<CacheControl>,
 }
 
 #[derive(Debug, Clone, Serialize, Deserialize)]
@@ -95,6 +130,45 @@ pub use databricks::DatabricksProvider;
 pub use embedded::EmbeddedProvider;
 pub use openai::OpenAIProvider;
 
+impl Message {
+    /// Create a new message with optional cache control
+    pub fn new(role: MessageRole, content: String) -> Self {
+        Self {
+            role,
+            content,
+            cache_control: None,
+        }
+    }
+
+    /// Create a new message with cache control
+    pub fn with_cache_control(role: MessageRole, content: String, cache_control: CacheControl) -> Self {
+        Self {
+            role,
+            content,
+            cache_control: Some(cache_control),
+        }
+    }
+    
+    /// Create a message with cache control, with provider validation
+    pub fn with_cache_control_validated(
+        role: MessageRole, 
+        content: String, 
+        cache_control: CacheControl,
+        provider: &dyn LLMProvider
+    ) -> Self {
+        if !provider.supports_cache_control() {
+            tracing::warn!(
+                "Cache control requested for provider '{}' which does not support it. \
+                Cache control is only supported by Anthropic and Anthropic via Databricks.",
+                provider.name()
+            );
+            return Self::new(role, content);
+        }
+        
+        Self::with_cache_control(role, content, cache_control)
+    }
+}
+
 /// Provider registry for managing multiple LLM providers
 pub struct ProviderRegistry {
     providers: HashMap<String, Box<dyn LLMProvider>>,
@@ -144,3 +218,68 @@ impl Default for ProviderRegistry {
         Self::new()
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_message_serialization_without_cache_control() {
+        let msg = Message::new(MessageRole::User, "Hello".to_string());
+        let json = serde_json::to_string(&msg).unwrap();
+        
+        println!("Message JSON without cache_control: {}", json);
+        assert!(!json.contains("cache_control"), 
+                "JSON should not contain 'cache_control' field when not configured");
+    }
+
+    #[test]
+    fn test_message_serialization_with_cache_control() {
+        let msg = Message::with_cache_control(
+            MessageRole::User,
+            "Hello".to_string(),
+            CacheControl::ephemeral(),
+        );
+        let json = serde_json::to_string(&msg).unwrap();
+        
+        println!("Message JSON with cache_control: {}", json);
+        assert!(json.contains("cache_control"), 
+                "JSON should contain 'cache_control' field when configured");
+        assert!(json.contains("ephemeral"), 
+                "JSON should contain 'ephemeral' value");
+        assert!(json.contains("\"type\":"), 
+                "JSON should contain 'type' field in cache_control");
+        assert!(!json.contains("null"), 
+                "JSON should not contain null values");
+    }
+
+    #[test]
+    fn test_cache_control_five_minute_serialization() {
+        let msg = Message::with_cache_control(
+            MessageRole::User,
+            "Hello".to_string(),
+            CacheControl::five_minute(),
+        );
+        let json = serde_json::to_string(&msg).unwrap();
+        
+        println!("Message JSON with 5-minute cache_control: {}", json);
+        assert!(json.contains("cache_control"), "JSON should contain 'cache_control' field");
+        assert!(json.contains("ephemeral"), "JSON should contain 'ephemeral' type");
+        assert!(json.contains("\"ttl\":\"5m\""), "JSON should contain ttl field with 5m value");
+    }
+
+    #[test]
+    fn test_cache_control_one_hour_serialization() {
+        let msg = Message::with_cache_control(
+            MessageRole::User,
+            "Hello".to_string(),
+            CacheControl::one_hour(),
+        );
+        let json = serde_json::to_string(&msg).unwrap();
+        
+        println!("Message JSON with 1-hour cache_control: {}", json);
+        assert!(json.contains("cache_control"), "JSON should contain 'cache_control' field");
+        assert!(json.contains("ephemeral"), "JSON should contain 'ephemeral' type");
+        assert!(json.contains("\"ttl\":\"1h\""), "JSON should contain ttl field with 1h value");
+    }
+}

crates/g3-providers/tests/cache_control_error_regression_test.rs

@@ -0,0 +1,131 @@
+//! Regression test for cache_control serialization bug
+//!
+//! This test verifies that cache_control is NOT serialized in the wrong format.
+//! The bug was that it serialized as:
+//!   - `system.0.cache_control.ephemeral.ttl` (WRONG)
+//!
+//! It should serialize as:
+//!   - `"cache_control": {"type": "ephemeral"}` for ephemeral
+//!   - `"cache_control": {"type": "ephemeral", "ttl": "5m"}` for 5minute
+//!   - `"cache_control": {"type": "ephemeral", "ttl": "1h"}` for 1hour
+
+use g3_providers::{CacheControl, Message, MessageRole};
+
+#[test]
+fn test_no_wrong_serialization_format() {
+    // Test ephemeral
+    let msg = Message::with_cache_control(
+        MessageRole::System,
+        "Test".to_string(),
+        CacheControl::ephemeral(),
+    );
+    let json = serde_json::to_string(&msg).unwrap();
+    
+    println!("Ephemeral message JSON: {}", json);
+    
+    // Should NOT contain the wrong format
+    assert!(!json.contains("system.0.cache_control"), 
+            "JSON should not contain 'system.0.cache_control' path");
+    assert!(!json.contains("cache_control.ephemeral"), 
+            "JSON should not contain 'cache_control.ephemeral' path");
+    
+    // Should contain the correct format
+    assert!(json.contains(r#""cache_control":{"type":"ephemeral"}"#),
+            "JSON should contain correct cache_control format");
+}
+
+#[test]
+fn test_five_minute_no_wrong_format() {
+    let msg = Message::with_cache_control(
+        MessageRole::System,
+        "Test".to_string(),
+        CacheControl::five_minute(),
+    );
+    let json = serde_json::to_string(&msg).unwrap();
+    
+    println!("5-minute message JSON: {}", json);
+    
+    // Should NOT contain the wrong format
+    assert!(!json.contains("system.0.cache_control"), 
+            "JSON should not contain 'system.0.cache_control' path");
+    assert!(!json.contains("cache_control.ephemeral.ttl"), 
+            "JSON should not contain 'cache_control.ephemeral.ttl' path");
+    
+    // Should contain the correct format with ttl as a direct field
+    assert!(json.contains(r#""type":"ephemeral""#),
+            "JSON should contain type field");
+    assert!(json.contains(r#""ttl":"5m""#),
+            "JSON should contain ttl field with value 5m");
+}
+
+#[test]
+fn test_one_hour_no_wrong_format() {
+    let msg = Message::with_cache_control(
+        MessageRole::System,
+        "Test".to_string(),
+        CacheControl::one_hour(),
+    );
+    let json = serde_json::to_string(&msg).unwrap();
+    
+    println!("1-hour message JSON: {}", json);
+    
+    // Should NOT contain the wrong format
+    assert!(!json.contains("system.0.cache_control"), 
+            "JSON should not contain 'system.0.cache_control' path");
+    assert!(!json.contains("cache_control.ephemeral.ttl"), 
+            "JSON should not contain 'cache_control.ephemeral.ttl' path");
+    
+    // Should contain the correct format with ttl as a direct field
+    assert!(json.contains(r#""type":"ephemeral""#),
+            "JSON should contain type field");
+    assert!(json.contains(r#""ttl":"1h""#),
+            "JSON should contain ttl field with value 1h");
+}
+
+#[test]
+fn test_cache_control_structure_is_flat() {
+    // Verify that the cache_control object has a flat structure
+    // with 'type' and optional 'ttl' at the same level
+    
+    let cache_control = CacheControl::five_minute();
+    let json_value = serde_json::to_value(&cache_control).unwrap();
+    
+    println!("Cache control as JSON value: {}", serde_json::to_string_pretty(&json_value).unwrap());
+    
+    let obj = json_value.as_object().expect("Should be an object");
+    
+    // Should have exactly 2 keys at the top level
+    assert_eq!(obj.len(), 2, "Cache control should have exactly 2 top-level fields");
+    
+    // Both 'type' and 'ttl' should be at the same level
+    assert!(obj.contains_key("type"), "Should have 'type' field");
+    assert!(obj.contains_key("ttl"), "Should have 'ttl' field");
+    
+    // 'type' should be a string, not an object
+    assert!(obj["type"].is_string(), "'type' should be a string value");
+    
+    // 'ttl' should be a string, not nested
+    assert!(obj["ttl"].is_string(), "'ttl' should be a string value");
+}
+
+#[test]
+fn test_ephemeral_cache_control_structure() {
+    let cache_control = CacheControl::ephemeral();
+    let json_value = serde_json::to_value(&cache_control).unwrap();
+    
+    println!("Ephemeral cache control as JSON value: {}", serde_json::to_string_pretty(&json_value).unwrap());
+    
+    let obj = json_value.as_object().expect("Should be an object");
+    
+    // Should have exactly 1 key (only 'type', no 'ttl')
+    assert_eq!(obj.len(), 1, "Ephemeral cache control should have exactly 1 top-level field");
+    
+    // Should have 'type' field
+    assert!(obj.contains_key("type"), "Should have 'type' field");
+    
+    // Should NOT have 'ttl' field
+    assert!(!obj.contains_key("ttl"), "Ephemeral should not have 'ttl' field");
+    
+    // 'type' should be a string with value "ephemeral"
+    assert_eq!(obj["type"].as_str().unwrap(), "ephemeral");
+}

crates/g3-providers/tests/cache_control_integration_test.rs

@@ -0,0 +1,164 @@
+//! Integration tests for cache_control feature
+//!
+//! These tests verify that cache_control is correctly serialized in messages
+//! for both Anthropic and Databricks providers.
+
+use g3_providers::{CacheControl, Message, MessageRole};
+use serde_json::json;
+
+#[test]
+fn test_ephemeral_cache_control_serialization() {
+    let cache_control = CacheControl::ephemeral();
+    let json = serde_json::to_value(&cache_control).unwrap();
+    
+    println!("Ephemeral cache_control JSON: {}", serde_json::to_string(&json).unwrap());
+    
+    assert_eq!(json, json!({
+        "type": "ephemeral"
+    }));
+    
+    // Verify no ttl field is present
+    assert!(!json.as_object().unwrap().contains_key("ttl"));
+}
+
+#[test]
+fn test_five_minute_cache_control_serialization() {
+    let cache_control = CacheControl::five_minute();
+    let json = serde_json::to_value(&cache_control).unwrap();
+    
+    println!("5-minute cache_control JSON: {}", serde_json::to_string(&json).unwrap());
+    
+    assert_eq!(json, json!({
+        "type": "ephemeral",
+        "ttl": "5m"
+    }));
+}
+
+#[test]
+fn test_one_hour_cache_control_serialization() {
+    let cache_control = CacheControl::one_hour();
+    let json = serde_json::to_value(&cache_control).unwrap();
+    
+    println!("1-hour cache_control JSON: {}", serde_json::to_string(&json).unwrap());
+    
+    assert_eq!(json, json!({
+        "type": "ephemeral",
+        "ttl": "1h"
+    }));
+}
+
+#[test]
+fn test_message_with_ephemeral_cache_control() {
+    let msg = Message::with_cache_control(
+        MessageRole::System,
+        "System prompt".to_string(),
+        CacheControl::ephemeral(),
+    );
+    
+    let json = serde_json::to_value(&msg).unwrap();
+    println!("Message with ephemeral cache_control: {}", serde_json::to_string(&json).unwrap());
+    
+    let cache_control = json.get("cache_control").expect("cache_control field should exist");
+    assert_eq!(cache_control.get("type").unwrap(), "ephemeral");
+    assert!(!cache_control.as_object().unwrap().contains_key("ttl"));
+}
+
+#[test]
+fn test_message_with_five_minute_cache_control() {
+    let msg = Message::with_cache_control(
+        MessageRole::System,
+        "System prompt".to_string(),
+        CacheControl::five_minute(),
+    );
+    
+    let json = serde_json::to_value(&msg).unwrap();
+    println!("Message with 5-minute cache_control: {}", serde_json::to_string(&json).unwrap());
+    
+    let cache_control = json.get("cache_control").expect("cache_control field should exist");
+    assert_eq!(cache_control.get("type").unwrap(), "ephemeral");
+    assert_eq!(cache_control.get("ttl").unwrap(), "5m");
+}
+
+#[test]
+fn test_message_with_one_hour_cache_control() {
+    let msg = Message::with_cache_control(
+        MessageRole::System,
+        "System prompt".to_string(),
+        CacheControl::one_hour(),
+    );
+    
+    let json = serde_json::to_value(&msg).unwrap();
+    println!("Message with 1-hour cache_control: {}", serde_json::to_string(&json).unwrap());
+    
+    let cache_control = json.get("cache_control").expect("cache_control field should exist");
+    assert_eq!(cache_control.get("type").unwrap(), "ephemeral");
+    assert_eq!(cache_control.get("ttl").unwrap(), "1h");
+}
+
+#[test]
+fn test_message_without_cache_control() {
+    let msg = Message::new(MessageRole::User, "Hello".to_string());
+    
+    let json = serde_json::to_value(&msg).unwrap();
+    println!("Message without cache_control: {}", serde_json::to_string(&json).unwrap());
+    
+    // cache_control field should not be present when not set
+    assert!(!json.as_object().unwrap().contains_key("cache_control"));
+}
+
+#[test]
+fn test_cache_control_json_format_ephemeral() {
+    let cache_control = CacheControl::ephemeral();
+    let json_str = serde_json::to_string(&cache_control).unwrap();
+    
+    println!("Ephemeral JSON string: {}", json_str);
+    
+    // Verify exact JSON format
+    assert_eq!(json_str, r#"{"type":"ephemeral"}"#);
+}
+
+#[test]
+fn test_cache_control_json_format_five_minute() {
+    let cache_control = CacheControl::five_minute();
+    let json_str = serde_json::to_string(&cache_control).unwrap();
+    
+    println!("5-minute JSON string: {}", json_str);
+    
+    // Verify exact JSON format
+    assert_eq!(json_str, r#"{"type":"ephemeral","ttl":"5m"}"#);
+}
+
+#[test]
+fn test_cache_control_json_format_one_hour() {
+    let cache_control = CacheControl::one_hour();
+    let json_str = serde_json::to_string(&cache_control).unwrap();
+    
+    println!("1-hour JSON string: {}", json_str);
+    
+    // Verify exact JSON format
+    assert_eq!(json_str, r#"{"type":"ephemeral","ttl":"1h"}"#);
+}
+
+#[test]
+fn test_deserialization_ephemeral() {
+    let json_str = r#"{"type":"ephemeral"}"#;
+    let cache_control: CacheControl = serde_json::from_str(json_str).unwrap();
+    
+    assert_eq!(cache_control.ttl, None);
+}
+
+#[test]
+fn test_deserialization_five_minute() {
+    let json_str = r#"{"type":"ephemeral","ttl":"5m"}"#;
+    let cache_control: CacheControl = serde_json::from_str(json_str).unwrap();
+    
+    assert_eq!(cache_control.ttl, Some("5m".to_string()));
+}
+
+#[test]
+fn test_deserialization_one_hour() {
+    let json_str = r#"{"type":"ephemeral","ttl":"1h"}"#;
+    let cache_control: CacheControl = serde_json::from_str(json_str).unwrap();
+    
+    assert_eq!(cache_control.ttl, Some("1h".to_string()));
+}