Custom tool block syntax (new triple-caret syntax implementation) (#41)

Also includes better session activity tracking / visualization, and saving draft messages per session.

Author: stippi

README.md

@@ -105,7 +105,7 @@ Available options:
 - `-p, --provider <PROVIDER>`: LLM provider to use [ai-core, anthropic, open-ai, ollama, vertex, open-router] (default: anthropic)
 - `-m, --model <MODEL>`: Model name to use (provider-specific defaults: anthropic="claude-sonnet-4-20250514", open-ai="gpt-4o", vertex="gemini-2.5-pro-preview-06-05", open-router="anthropic/claude-3-7-sonnet", ollama=required)
 - `--base-url <BASE_URL>`: API base URL for the LLM provider to use
-- `--tools-type <TOOLS_TYPE>`: Type of tool declaration [native, xml] (default: xml) - `native` = tools via API, `xml` = custom system message
+- `--tool-syntax <TOOL_SYNTAX>`: Tool invocation syntax [native, xml, caret] (default: xml) - `native` = tools via API, `xml` = custom system message with XML tags, `caret` = custom system message with triple-caret blocks
 - `--num-ctx <NUM_CTX>`: Context window size in tokens (default: 8192, only relevant for Ollama)
 - `--record <RECORD>`: Record API responses to a file (only supported for Anthropic provider currently)
 - `--playback <PLAYBACK>`: Play back a recorded session from a file
@@ -162,6 +162,9 @@ Available options:
 This section is not really a roadmap, as the items are in no particular order.
 Below are some topics that are likely the next focus.
 
+- **Block Replacing in Changed Files**: When streaming a tool use block, we already know the LLM attempts to use `replace_in_file` and we know in which file quite early.
+  If we also know this file has changed since the LLM last read it, we can block the attempt with an appropriate error message.
+- **Compact Tool Use Failures**: When the LLM produces an invalid tool call, or a mismatching search block, we should be able to strip the failed attempt from the message history, saving tokens.
 - **Improve UI**: There are various ways in which the UI can be improved.
 - **Add Memory Tools**: Add tools that facilitate building up a knowledge base useful work working in a given project.
 - **Security**: Ideally, the execution for all tools would run in some sort of sandbox that restricts access to the files in the project tracked by git.

crates/code_assistant/resources/system_message_tools.md

@@ -20,27 +20,7 @@ TOOL USE
 
 You have access to a set of tools. You can use one tool per message, and will receive the result of that tool use in the user's response. You use tools step-by-step to accomplish a given task, with each tool use informed by the result of the previous tool use.
 
-# Tool Use Formatting
-
-Tool use is formatted using XML-style tags. The tool name is prefixed by 'tool:' and enclosed in opening and closing tags, and each parameter is similarly prefixed with 'param:' and enclosed within its own set of tags. Here's the structure:
-
-<tool:tool_name>
-<param:parameter1_name>value1</param:parameter1_name>
-<param:parameter2_name>
-value can stretch
-multiple lines
-</param:parameter2_name>
-...
-</tool:tool_name>
-
-For example:
-
-<tool:read_files>
-<param:project>frontend</param:project>
-<param:path>src/main.js</param:path>
-</tool:read_files>
-
-Always adhere to this format for the tool use to ensure proper parsing and execution.
+{{syntax}}
 
 # Tools
 

crates/code_assistant/src/agent/mod.rs

@@ -3,10 +3,9 @@ mod tests;
 
 pub mod persistence;
 pub mod runner;
-mod tool_description_generator;
 mod types;
 
-pub use crate::types::ToolMode;
+pub use crate::types::ToolSyntax;
 pub use persistence::FileStatePersistence;
 pub use runner::Agent;
 pub use types::ToolExecution;

crates/code_assistant/src/agent/persistence.rs

@@ -6,7 +6,7 @@ use std::sync::{Arc, Mutex};
 use crate::agent::types::ToolExecution;
 use crate::persistence::{ChatSession, SerializedToolExecution};
 use crate::session::SessionManager;
-use crate::types::{ToolMode, WorkingMemory};
+use crate::types::{ToolSyntax, WorkingMemory};
 
 use std::time::SystemTime;
 use tracing::{debug, info};
@@ -117,16 +117,16 @@ const STATE_FILE: &str = ".code-assistant.state.json";
 #[derive(Clone)]
 pub struct FileStatePersistence {
     state_file_path: PathBuf,
-    tool_mode: ToolMode,
+    tool_syntax: ToolSyntax,
 }
 
 impl FileStatePersistence {
-    pub fn new(working_dir: &Path, tool_mode: ToolMode) -> Self {
+    pub fn new(working_dir: &Path, tool_syntax: ToolSyntax) -> Self {
         let state_file_path = working_dir.join(STATE_FILE);
         info!("Using state file: {}", state_file_path.display());
         Self {
             state_file_path,
-            tool_mode,
+            tool_syntax,
         }
     }
 
@@ -189,7 +189,7 @@ impl AgentStatePersistence for FileStatePersistence {
             working_memory,
             init_path,
             initial_project,
-            tool_mode: self.tool_mode,
+            tool_syntax: self.tool_syntax,
             next_request_id,
         };