lean_ctx/proxy/
anthropic.rs

1use axum::{
2    body::Body,
3    extract::State,
4    http::{Request, StatusCode},
5    response::Response,
6};
7use serde_json::Value;
8
9use super::compress::compress_tool_result;
10use super::forward;
11use super::tool_kind::{self, should_protect, ToolResultKind};
12use super::ProxyState;
13
14pub async fn handler(
15    State(state): State<ProxyState>,
16    req: Request<Body>,
17) -> Result<Response, StatusCode> {
18    let upstream = state.anthropic_upstream.clone();
19    forward::forward_request(
20        State(state),
21        req,
22        &upstream,
23        "/v1/messages",
24        compress_request_body,
25        "Anthropic",
26        &[],
27    )
28    .await
29}
30
31fn compress_request_body(parsed: Value, original_size: usize) -> (Vec<u8>, usize, usize) {
32    let mut doc = parsed;
33    let mut modified = false;
34
35    if let Some(messages) = doc.get_mut("messages").and_then(|m| m.as_array_mut()) {
36        // Resolve tool-call id → tool name so file/source reads can be protected
37        // from lossy compression that would force the model to re-read mid-task.
38        let tool_names = tool_kind::anthropic_tool_names(messages);
39
40        // Prune at a frozen, cache-aware boundary by default: Anthropic's
41        // prompt cache matches exact prefixes, so the boundary must not move
42        // every turn (see `history_prune::prune_boundary`).
43        let mode = crate::core::config::Config::load()
44            .proxy
45            .resolved_history_mode();
46        let boundary = super::history_prune::prune_boundary(mode, messages.len());
47        modified |= super::history_prune::prune_history(messages, boundary, &tool_names);
48
49        for msg in messages.iter_mut() {
50            let role = msg.get("role").and_then(|r| r.as_str()).unwrap_or("");
51            if role != "user" {
52                continue;
53            }
54
55            if let Some(content) = msg.get_mut("content").and_then(|c| c.as_array_mut()) {
56                for block in content.iter_mut() {
57                    if block.get("type").and_then(|t| t.as_str()) != Some("tool_result") {
58                        continue;
59                    }
60
61                    let name = block
62                        .get("tool_use_id")
63                        .and_then(|v| v.as_str())
64                        .and_then(|id| tool_names.get(id))
65                        .map(String::as_str);
66                    let kind = name.map_or(ToolResultKind::Other, tool_kind::classify_tool_name);
67
68                    if let Some(inner_content) = block.get_mut("content") {
69                        modified |= compress_content_field(inner_content, name, kind);
70                    }
71                }
72            }
73        }
74    }
75
76    let out = serde_json::to_vec(&doc).unwrap_or_default();
77    let compressed_size = if modified { out.len() } else { original_size };
78    (out, original_size, compressed_size)
79}
80
81/// Compresses a tool_result `content` field unless it is a protected file/source
82/// read, which must reach the model intact (it is what gets edited).
83fn compress_content_field(
84    content: &mut Value,
85    tool_name: Option<&str>,
86    kind: ToolResultKind,
87) -> bool {
88    match content {
89        Value::String(s) => {
90            if should_protect(kind, s) {
91                return false;
92            }
93            let compressed = compress_tool_result(s, tool_name);
94            if compressed.len() < s.len() {
95                *s = compressed;
96                return true;
97            }
98            false
99        }
100        Value::Array(arr) => {
101            let mut modified = false;
102            for item in arr.iter_mut() {
103                if item.get("type").and_then(|t| t.as_str()) == Some("text") {
104                    if let Some(text) = item
105                        .get_mut("text")
106                        .and_then(|t| t.as_str().map(String::from))
107                    {
108                        if should_protect(kind, &text) {
109                            continue;
110                        }
111                        let compressed = compress_tool_result(&text, tool_name);
112                        if compressed.len() < text.len() {
113                            item["text"] = Value::String(compressed);
114                            modified = true;
115                        }
116                    }
117                }
118            }
119            modified
120        }
121        _ => false,
122    }
123}
124
125#[cfg(test)]
126mod tests {
127    use super::*;
128
129    fn source_file_body() -> Vec<u8> {
130        let code = (0..60)
131            .map(|i| format!("    let binding_{i} = compute_value_{i}(context, options);"))
132            .collect::<Vec<_>>()
133            .join("\n");
134        let body = serde_json::json!({
135            "model": "claude-opus-4-8",
136            "messages": [
137                {
138                    "role": "assistant",
139                    "content": [{"type": "tool_use", "id": "toolu_1", "name": "Read", "input": {"file_path": "src/app.rs"}}]
140                },
141                {
142                    "role": "user",
143                    "content": [{"type": "tool_result", "tool_use_id": "toolu_1", "content": code}]
144                }
145            ]
146        });
147        serde_json::to_vec(&body).unwrap()
148    }
149
150    #[test]
151    fn read_tool_result_is_never_truncated() {
152        let bytes = source_file_body();
153        let body: Value = serde_json::from_slice(&bytes).unwrap();
154        let (out, _orig, _comp) = compress_request_body(body, bytes.len());
155        let parsed: Value = serde_json::from_slice(&out).unwrap();
156        let content = parsed["messages"][1]["content"][0]["content"]
157            .as_str()
158            .unwrap();
159        assert!(
160            content.contains("binding_59"),
161            "the full source body must survive — refactors need it intact"
162        );
163        assert!(!content.contains("lines omitted"));
164    }
165
166    #[test]
167    fn bash_tool_result_still_compresses() {
168        let log = {
169            let mut s = String::from(
170                "$ git status\nOn branch main\nYour branch is up to date with 'origin/main'.\n\nChanges not staged for commit:\n  (use \"git add <file>...\" to update what will be committed)\n",
171            );
172            for i in 0..90 {
173                s.push_str(&format!("\tmodified:   src/module_{i}/file_{i}.rs\n"));
174            }
175            s.push_str("\nno changes added to commit (use \"git add\" and/or \"git commit -a\")\n");
176            s
177        };
178        let body = serde_json::json!({
179            "messages": [
180                {"role": "assistant", "content": [{"type": "tool_use", "id": "t1", "name": "Bash", "input": {}}]},
181                {"role": "user", "content": [{"type": "tool_result", "tool_use_id": "t1", "content": log}]}
182            ]
183        });
184        let bytes = serde_json::to_vec(&body).unwrap();
185        let (_out, orig, comp) = compress_request_body(body, bytes.len());
186        assert!(comp < orig, "shell output must still be compressed");
187    }
188}
lean_ctx/proxy/anthropic.rs

lean_ctx/proxy/
anthropic.rs
