lean_ctx/tools/registered/
ctx_prefetch.rs

1use rmcp::ErrorData;
2use rmcp::model::Tool;
3use serde_json::{Map, Value, json};
4
5use crate::server::tool_trait::{
6    McpTool, ToolContext, ToolOutput, get_int, get_str, get_str_array,
7};
8use crate::tool_defs::tool_def;
9
10pub struct CtxPrefetchTool;
11
12impl McpTool for CtxPrefetchTool {
13    fn name(&self) -> &'static str {
14        "ctx_prefetch"
15    }
16
17    fn tool_def(&self) -> Tool {
18        tool_def(
19            "ctx_prefetch",
20            "WORKFLOW: call BEFORE context-heavy operations to minimize latency.\n\
21            ANTIPATTERN: NOT for normal reads — only for proactive cache warming.\n\
22            Prewarms cache for blast radius files via graph + task signals.\n\
23            task=description; changed_files=paths for blast radius;\n\
24            budget_tokens=soft budget (default 3000); max_files=limit (default 10).\n\
25            Saves latency (not tokens): preloads files before needed.",
26            json!({
27                "type": "object",
28                "properties": {
29                    "root": { "type": "string", "description": "Project root directory" },
30                    "task": { "type": "string", "description": "Task description for relevance scoring" },
31                    "changed_files": { "type": "array", "items": { "type": "string" }, "description": "Changed file paths for computing blast radius" },
32                    "budget_tokens": { "type": "integer", "description": "Soft token budget (default: 3000)" },
33                    "max_files": { "type": "integer", "description": "Max files to prefetch (default: 10)" }
34                }
35            }),
36        )
37    }
38
39    fn handle(
40        &self,
41        args: &Map<String, Value>,
42        ctx: &ToolContext,
43    ) -> Result<ToolOutput, ErrorData> {
44        let root = if get_str(args, "root").is_some() {
45            if let Some(p) = ctx.resolved_path("root") {
46                p.to_string()
47            } else if let Some(err) = ctx.path_error("root") {
48                return Err(ErrorData::invalid_params(format!("root: {err}"), None));
49            } else {
50                ctx.project_root.clone()
51            }
52        } else if let Some(ref session) = ctx.session {
53            let guard = tokio::task::block_in_place(|| session.blocking_read());
54            guard
55                .project_root
56                .clone()
57                .unwrap_or_else(|| ".".to_string())
58        } else {
59            ".".to_string()
60        };
61
62        let task = get_str(args, "task");
63        let changed_files = get_str_array(args, "changed_files");
64        let budget_tokens = get_int(args, "budget_tokens").map_or(3000, |n| n.max(0) as usize);
65        let max_files = get_int(args, "max_files").map(|n| n.max(1) as usize);
66
67        let resolved_changed: Option<Vec<String>> = changed_files.map(|files| {
68            files
69                .iter()
70                .map(|p| ctx.resolve_path_sync(p).unwrap_or_else(|_| p.clone()))
71                .collect()
72        });
73
74        let cache = ctx
75            .cache
76            .as_ref()
77            .ok_or_else(|| ErrorData::internal_error("cache not available", None))?;
78        let Some(mut guard) = crate::server::bounded_lock::write(cache, "ctx_prefetch") else {
79            return Ok(ToolOutput::simple(
80                "[prefetch skipped — cache busy, retry in a moment]".to_string(),
81            ));
82        };
83        let result = crate::tools::ctx_prefetch::handle(
84            &mut guard,
85            &root,
86            task.as_deref(),
87            resolved_changed.as_deref(),
88            budget_tokens,
89            max_files,
90            ctx.crp_mode,
91        );
92
93        Ok(ToolOutput {
94            text: result,
95            original_tokens: 0,
96            saved_tokens: 0,
97            mode: Some("prefetch".to_string()),
98            path: None,
99            changed: false,
100            shell_outcome: None,
101            content_blocks: None,
102        })
103    }
104}
lean_ctx/tools/registered/ctx_prefetch.rs

lean_ctx/tools/registered/
ctx_prefetch.rs
