lean_ctx_server/tools/registered/
ctx_delta.rs

1// SPDX-License-Identifier: Apache-2.0
2use rmcp::ErrorData;
3use rmcp::model::Tool;
4use serde_json::{Map, Value, json};
5
6use crate::server::tool_trait::{McpTool, ToolContext, ToolOutput, require_resolved_path};
7use lean_ctx::tool_defs::tool_def;
8
9pub struct CtxDeltaTool;
10
11impl McpTool for CtxDeltaTool {
12    fn name(&self) -> &'static str {
13        "ctx_delta"
14    }
15
16    fn tool_def(&self) -> Tool {
17        tool_def(
18            "ctx_delta",
19            "Incremental diff since last read — shows only changed lines after you edit.\n\
20             WORKFLOW: ctx_read(mode=full) -> edit -> ctx_delta (no re-read needed).\n\
21             Use INSTEAD of re-reading the whole file after modifications — it returns only changed\n\
22             lines and avoids resending unchanged content. Path must have a prior ctx_read in this session\'s cache.\n\
23             ctx_read(mode=diff) diffs this same cache, not git; for HEAD use git diff.",
24            json!({
25                "type": "object",
26                "properties": {
27                    "path": { "type": "string", "description": "File path" }
28                },
29                "required": ["path"]
30            }),
31        )
32    }
33
34    fn handle(
35        &self,
36        args: &Map<String, Value>,
37        ctx: &ToolContext,
38    ) -> Result<ToolOutput, ErrorData> {
39        let path = require_resolved_path(ctx, args, "path")?;
40
41        {
42            let cache_lock = ctx
43                .cache
44                .as_ref()
45                .ok_or_else(|| ErrorData::internal_error("cache not available", None))?;
46            let Some(mut cache) =
47                crate::server::bounded_lock::write(cache_lock, "ctx_delta cache write")
48            else {
49                lean_ctx::core::io_health::record_freeze();
50                return Err(ErrorData::internal_error(
51                    "cache busy (ctx_delta) — retry in a moment",
52                    None,
53                ));
54            };
55            let output = crate::tools::ctx_delta::handle(&mut cache, &path);
56            let original = cache.get(&path).map_or(0, |e| e.original_tokens);
57            let tokens = lean_ctx::core::tokens::count_tokens(&output);
58            drop(cache);
59
60            if let Some(session_lock) = ctx.session.as_ref() {
61                let mut session = session_lock.blocking_write();
62                session.mark_modified(&path);
63            }
64
65            let saved = original.saturating_sub(tokens);
66            Ok(ToolOutput {
67                text: output,
68                original_tokens: original,
69                saved_tokens: saved,
70                mode: Some("delta".to_string()),
71                path: Some(path),
72                changed: false,
73                shell_outcome: None,
74                content_blocks: None,
75            })
76        }
77    }
78}
lean_ctx_server/tools/registered/ctx_delta.rs

lean_ctx_server/tools/registered/
ctx_delta.rs
