claude_agent/
context.rs

1// Layer 5: THE FRONTAL LOBE — Context Engine
2// AUTO-COMPACT, CACHE PREFIX, CLAUDE.md INJECTION, MEMORY.md tube.
3
4use std::path::Path;
5use crate::types::*;
6
7const COMPACT_THRESHOLD: usize = 150_000;
8
9pub struct ContextEngine {
10    messages: Vec<Message>,
11    system_prompt: String,
12    token_estimate: usize,
13}
14
15impl Default for ContextEngine {
16    fn default() -> Self {
17        Self::new()
18    }
19}
20
21impl ContextEngine {
22    pub fn new() -> Self {
23        Self {
24            messages: Vec::new(),
25            system_prompt: String::new(),
26            token_estimate: 0,
27        }
28    }
29
30    /// Chamber: CLAUDE.md INJECTION — build system prompt
31    /// If a custom system prompt file exists at ~/.claude-agent/system.md or is passed
32    /// via --system-prompt flag, it replaces the default agent identity preamble.
33    pub async fn build_system_prompt(&mut self, cwd: &str, memory_path: &str) {
34        let home = std::env::var("HOME").unwrap_or_default();
35        let custom_system_path = format!("{home}/.claude-agent/system.md");
36
37        let base_prompt = if Path::new(&custom_system_path).exists() {
38            tokio::fs::read_to_string(&custom_system_path).await.unwrap_or_default()
39        } else {
40            "You are an AI coding agent. You help users with software engineering tasks \
41             by reading files, writing code, running commands, and searching codebases.".to_string()
42        };
43
44        let mut parts = vec![base_prompt];
45
46        // Inject CLAUDE.md files
47        for md_path in &[
48            format!("{cwd}/CLAUDE.md"),
49            format!("{}/CLAUDE.md", std::env::var("HOME").unwrap_or_default()),
50        ] {
51            if Path::new(md_path).exists() {
52                if let Ok(content) = tokio::fs::read_to_string(md_path).await {
53                    parts.push(format!("\n# Project Instructions ({md_path})\n{content}"));
54                }
55            }
56        }
57
58        // Inject persistent memory
59        if Path::new(memory_path).exists() {
60            if let Ok(memory) = tokio::fs::read_to_string(memory_path).await {
61                if !memory.trim().is_empty() {
62                    let truncated: String = memory.chars().take(4000).collect();
63                    parts.push(format!("\n# Persistent Memory\n{truncated}"));
64                }
65            }
66        }
67
68        // Environment context
69        parts.push("\n# Environment".to_string());
70        parts.push(format!("- Working directory: {cwd}"));
71        parts.push(format!("- Platform: {}", std::env::consts::OS));
72        parts.push(format!("- Arch: {}", std::env::consts::ARCH));
73        parts.push(format!("- Date: {}", chrono::Utc::now().format("%Y-%m-%d")));
74
75        self.system_prompt = parts.join("\n");
76    }
77
78    /// Chamber: AUTO-COMPACT — compress when approaching limits
79    pub fn compact(&mut self) {
80        if self.messages.len() <= 4 {
81            return;
82        }
83
84        let first = self.messages[0].clone();
85        let recent: Vec<_> = self.messages.iter().rev().take(6).cloned().collect();
86        let dropped = self.messages.len() - 7;
87
88        let marker = Message {
89            role: Role::User,
90            content: MessageContent::Text(format!(
91                "[Context compacted: {dropped} earlier messages summarized.]"
92            )),
93        };
94
95        self.messages = Vec::with_capacity(8);
96        self.messages.push(first);
97        self.messages.push(marker);
98        self.messages.extend(recent.into_iter().rev());
99        self.estimate_tokens();
100    }
101
102    pub fn add_message(&mut self, msg: Message) {
103        self.messages.push(msg);
104        self.estimate_tokens();
105
106        if self.token_estimate > COMPACT_THRESHOLD {
107            self.compact();
108        }
109    }
110
111    fn estimate_tokens(&mut self) {
112        let mut chars = self.system_prompt.len();
113        for msg in &self.messages {
114            match &msg.content {
115                MessageContent::Text(t) => chars += t.len(),
116                MessageContent::Blocks(blocks) => {
117                    for block in blocks {
118                        match block {
119                            ContentBlock::Text { text } => chars += text.len(),
120                            _ => chars += 200,
121                        }
122                    }
123                }
124            }
125        }
126        self.token_estimate = chars / 4;
127    }
128
129    pub fn override_system_prompt(&mut self, prompt: &str) {
130        self.system_prompt = prompt.to_string();
131    }
132
133    pub fn messages(&self) -> &[Message] {
134        &self.messages
135    }
136
137    pub fn system_prompt(&self) -> &str {
138        &self.system_prompt
139    }
140
141    pub fn token_estimate(&self) -> usize {
142        self.token_estimate
143    }
144
145    pub fn is_near_limit(&self) -> bool {
146        self.token_estimate > COMPACT_THRESHOLD
147    }
148}
claude_agent/context.rs

claude_agent/
context.rs
