feat: auto-LSP integration with didOpen/didChange and diagnostic enrichment

Wire LSP into the Read/Edit/Write tool flow so the agent automatically
gets diagnostics after file operations:

- lsp_transport: Add LspServerMessage enum, read_message() for handling
  both responses and server-initiated notifications, notification queue
  with drain_notifications(), send_request now handles interleaved
  publishDiagnostics without breaking

- lsp_process: Add did_open(), did_change(), drain_diagnostics(),
  open file tracking (HashSet) and version counters for didChange,
  language_id_for_path() and severity_name() helpers

- lsp_client: Add notify_file_open(), notify_file_change(),
  fetch_diagnostics_for_file() with best-effort graceful fallback,
  registry-level open file tracking, diagnostic caching

- tools: Enrich run_read_file with didOpen + diagnostics, run_write_file
  and run_edit_file with didChange + diagnostics, format_diagnostic_appendix()
  for readable diagnostic output appended to tool results

All enrichment is non-blocking: if no LSP server is available, tools work
exactly as before. No errors propagate from the LSP layer.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

rust/crates/runtime/src/lsp_client.rs

@@ -1,7 +1,7 @@
 #![allow(clippy::should_implement_trait, clippy::must_use_candidate)]
 //! LSP (Language Server Protocol) client registry for tool dispatch.
 
-use std::collections::HashMap;
+use std::collections::{HashMap, HashSet};
 use std::path::Path;
 use std::sync::{Arc, Mutex};
 
@@ -156,6 +156,7 @@ pub struct LspRegistry {
 #[derive(Debug, Default)]
 struct RegistryInner {
     servers: HashMap<String, LspServerEntry>,
+    open_files: HashSet<String>,
 }
 
 impl LspRegistry {
@@ -420,6 +421,139 @@ impl LspRegistry {
         Ok(())
     }
 
+    /// Notify the LSP server that a file was opened and collect any diagnostics.
+    /// Best-effort: returns empty vec if no server is available.
+    pub fn notify_file_open(&self, path: &str, content: &str) -> Vec<LspDiagnostic> {
+        let Some(language) = Self::language_for_path(path) else {
+            return Vec::new();
+        };
+
+        // Check if already open
+        {
+            let inner = self.inner.lock().expect("lsp registry lock poisoned");
+            if inner.open_files.contains(path) {
+                return Vec::new();
+            }
+        }
+
+        // Lazy-start the server
+        if self.start_server(&language).is_err() {
+            return Vec::new();
+        }
+
+        // Get the process handle and send didOpen
+        let process_arc = {
+            let inner = self.inner.lock().expect("lsp registry lock poisoned");
+            match inner.servers.get(&language).and_then(|e| e.process.clone()) {
+                Some(p) => p,
+                None => return Vec::new(),
+            }
+        };
+
+        let mut diagnostics = Vec::new();
+        if let Ok(mut process) = process_arc.lock() {
+            let rt = tokio::runtime::Builder::new_current_thread()
+                .enable_all()
+                .build();
+            if let Ok(rt) = rt {
+                let _ = rt.block_on(process.did_open(path, content));
+                diagnostics = process.drain_diagnostics();
+            }
+        }
+
+        // Cache diagnostics in registry state
+        if !diagnostics.is_empty() {
+            let diag_path = path.to_owned();
+            let diags = diagnostics.clone();
+            let mut inner = self.inner.lock().expect("lsp registry lock poisoned");
+            if let Some(entry) = inner.servers.get_mut(&language) {
+                // Replace diagnostics for this file (publishDiagnostics is full replacement)
+                entry.state.diagnostics.retain(|d| d.path != diag_path);
+                entry.state.diagnostics.extend(diags);
+            }
+        }
+
+        // Mark file as open
+        {
+            let mut inner = self.inner.lock().expect("lsp registry lock poisoned");
+            inner.open_files.insert(path.to_owned());
+        }
+
+        diagnostics
+    }
+
+    /// Notify the LSP server that a file changed and collect any diagnostics.
+    /// Best-effort: returns empty vec if no server is available.
+    pub fn notify_file_change(&self, path: &str, content: &str) -> Vec<LspDiagnostic> {
+        let Some(language) = Self::language_for_path(path) else {
+            return Vec::new();
+        };
+
+        // Get the process handle
+        let process_arc = {
+            let inner = self.inner.lock().expect("lsp registry lock poisoned");
+            match inner.servers.get(&language).and_then(|e| e.process.clone()) {
+                Some(p) => p,
+                None => return Vec::new(),
+            }
+        };
+
+        let mut diagnostics = Vec::new();
+        if let Ok(mut process) = process_arc.lock() {
+            let rt = tokio::runtime::Builder::new_current_thread()
+                .enable_all()
+                .build();
+            if let Ok(rt) = rt {
+                let _ = rt.block_on(process.did_change(path, content));
+                diagnostics = process.drain_diagnostics();
+            }
+        }
+
+        // Replace cached diagnostics for this file
+        if !diagnostics.is_empty() {
+            let diag_path = path.to_owned();
+            let diags = diagnostics.clone();
+            let mut inner = self.inner.lock().expect("lsp registry lock poisoned");
+            if let Some(entry) = inner.servers.get_mut(&language) {
+                entry.state.diagnostics.retain(|d| d.path != diag_path);
+                entry.state.diagnostics.extend(diags);
+            }
+        }
+
+        diagnostics
+    }
+
+    /// Fetch diagnostics for a file by draining pending server notifications
+    /// and returning cached diagnostics.
+    pub fn fetch_diagnostics_for_file(&self, path: &str) -> Vec<LspDiagnostic> {
+        let Some(language) = Self::language_for_path(path) else {
+            return Vec::new();
+        };
+
+        // Drain pending notifications from the transport
+        let process_arc = {
+            let inner = self.inner.lock().expect("lsp registry lock poisoned");
+            inner.servers.get(&language).and_then(|e| e.process.clone())
+        };
+
+        if let Some(process_arc) = process_arc {
+            if let Ok(mut process) = process_arc.lock() {
+                let new_diags = process.drain_diagnostics();
+                if !new_diags.is_empty() {
+                    let diag_path = path.to_owned();
+                    let mut inner =
+                        self.inner.lock().expect("lsp registry lock poisoned");
+                    if let Some(entry) = inner.servers.get_mut(&language) {
+                        entry.state.diagnostics.retain(|d| d.path != diag_path);
+                        entry.state.diagnostics.extend(new_diags);
+                    }
+                }
+            }
+        }
+
+        self.get_diagnostics(path)
+    }
+
     /// Dispatch an LSP action and return a structured result.
     #[allow(clippy::too_many_lines)]
     pub fn dispatch(

rust/crates/runtime/src/lsp_discovery.rs

@@ -109,7 +109,7 @@ pub fn command_exists_on_path(command: &str) -> bool {
     Command::new(command)
         .arg("--version")
         .output()
-        .map_or(false, |_| true)
+        .is_ok()
 }
 
 /// Discover LSP servers that are actually installed on the current system.

rust/crates/runtime/src/lsp_process.rs

@@ -1,11 +1,12 @@
 //! LSP process manager: spawns language servers and drives the LSP lifecycle.
 
+use std::collections::{HashMap, HashSet};
 use std::path::Path;
 
 use serde_json::Value as JsonValue;
 
 use crate::lsp_client::{
-    LspCompletionItem, LspHoverResult, LspLocation, LspServerStatus, LspSymbol,
+    LspCompletionItem, LspDiagnostic, LspHoverResult, LspLocation, LspServerStatus, LspSymbol,
 };
 use crate::lsp_transport::{LspTransport, LspTransportError};
 
@@ -16,6 +17,8 @@ pub struct LspProcess {
     root_uri: String,
     capabilities: Option<JsonValue>,
     status: LspServerStatus,
+    open_files: HashSet<String>,
+    version_counter: HashMap<String, u32>,
 }
 
 #[allow(clippy::cast_possible_truncation)]
@@ -38,6 +41,8 @@ impl LspProcess {
             root_uri: root_uri.clone(),
             capabilities: None,
             status: LspServerStatus::Starting,
+            open_files: HashSet::new(),
+            version_counter: HashMap::new(),
         };
 
         process.initialize(&canonical).await?;
@@ -279,6 +284,103 @@ impl LspProcess {
         }
     }
 
+    /// Notify the server that a file was opened. Sends `textDocument/didOpen`.
+    /// No-op if the file is already tracked as open.
+    pub async fn did_open(&mut self, path: &str, content: &str) -> Result<(), LspProcessError> {
+        if self.open_files.contains(path) {
+            return Ok(());
+        }
+
+        let uri = path_to_uri(path);
+        let language_id = language_id_for_path(path);
+        let params = serde_json::json!({
+            "textDocument": {
+                "uri": uri,
+                "languageId": language_id,
+                "version": 0,
+                "text": content
+            }
+        });
+
+        self.transport
+            .send_notification("textDocument/didOpen", Some(params))
+            .await
+            .map_err(LspProcessError::Transport)?;
+
+        self.open_files.insert(path.to_owned());
+        self.version_counter.insert(path.to_owned(), 0);
+        Ok(())
+    }
+
+    /// Notify the server that a file's content changed. Sends `textDocument/didChange`.
+    pub async fn did_change(&mut self, path: &str, content: &str) -> Result<(), LspProcessError> {
+        let version = self.version_counter.get(path).map_or(1, |v| v + 1);
+
+        let uri = path_to_uri(path);
+        let params = serde_json::json!({
+            "textDocument": { "uri": uri, "version": version },
+            "contentChanges": [{ "text": content }]
+        });
+
+        self.transport
+            .send_notification("textDocument/didChange", Some(params))
+            .await
+            .map_err(LspProcessError::Transport)?;
+
+        self.version_counter.insert(path.to_owned(), version);
+        Ok(())
+    }
+
+    /// Drain queued server notifications and extract `publishDiagnostics`.
+    #[allow(clippy::redundant_closure_for_method_calls)]
+    pub fn drain_diagnostics(&mut self) -> Vec<LspDiagnostic> {
+        let notifications = self.transport.drain_notifications();
+        let mut diagnostics = Vec::new();
+        for n in &notifications {
+            if n.method == "textDocument/publishDiagnostics" {
+                if let Some(params) = &n.params {
+                    if let Some(uri) = params.get("uri").and_then(|v| v.as_str()) {
+                        let path = uri_to_path(uri);
+                        if let Some(diags) = params.get("diagnostics").and_then(|v| v.as_array())
+                        {
+                            for d in diags {
+                                diagnostics.push(LspDiagnostic {
+                                    path: path.clone(),
+                                    line: d
+                                        .get("range")
+                                        .and_then(|r| r.get("start"))
+                                        .and_then(|s| s.get("line"))
+                                        .and_then(|v| v.as_u64())
+                                        .map_or(0, |v| v as u32),
+                                    character: d
+                                        .get("range")
+                                        .and_then(|r| r.get("start"))
+                                        .and_then(|s| s.get("character"))
+                                        .and_then(|v| v.as_u64())
+                                        .map_or(0, |v| v as u32),
+                                    severity: d
+                                        .get("severity")
+                                        .and_then(|v| v.as_u64())
+                                        .map_or_else(|| "error".to_owned(), severity_name),
+                                    message: d
+                                        .get("message")
+                                        .and_then(|v| v.as_str())
+                                        .unwrap_or("")
+                                        .to_owned(),
+                                    source: d
+                                        .get("source")
+                                        .and_then(|v| v.as_str())
+                                        .map(str::to_owned),
+                                });
+                            }
+                        }
+                    }
+                }
+            }
+        }
+        diagnostics
+    }
+
     #[must_use]
     pub fn status(&self) -> LspServerStatus {
         self.status
@@ -360,6 +462,39 @@ fn uri_to_path(uri: &str) -> String {
     uri.strip_prefix("file://").unwrap_or(uri).to_owned()
 }
 
+fn language_id_for_path(path: &str) -> String {
+    let ext = std::path::Path::new(path)
+        .extension()
+        .and_then(|e| e.to_str())
+        .unwrap_or("");
+    match ext {
+        "rs" => "rust",
+        "ts" => "typescript",
+        "tsx" => "typescriptreact",
+        "js" => "javascript",
+        "jsx" => "javascriptreact",
+        "py" => "python",
+        "go" => "go",
+        "java" => "java",
+        "c" | "h" => "c",
+        "cpp" | "hpp" | "cc" => "cpp",
+        "rb" => "ruby",
+        "lua" => "lua",
+        _ => ext,
+    }
+    .to_owned()
+}
+
+fn severity_name(code: u64) -> String {
+    match code {
+        1 => "error".to_owned(),
+        2 => "warning".to_owned(),
+        3 => "info".to_owned(),
+        4 => "hint".to_owned(),
+        _ => format!("unknown({code})"),
+    }
+}
+
 fn parse_hover(value: &JsonValue) -> Option<LspHoverResult> {
     let contents = value.get("contents")?;
 

rust/crates/runtime/src/lsp_transport.rs

@@ -89,6 +89,14 @@ impl LspResponse {
     }
 }
 
+/// A message received from an LSP server — either a response to a request
+/// or a server-initiated notification (e.g. `textDocument/publishDiagnostics`).
+#[derive(Debug, Clone)]
+pub enum LspServerMessage {
+    Response(LspResponse),
+    Notification(LspNotification),
+}
+
 #[derive(Debug)]
 pub enum LspTransportError {
     Io(io::Error),
@@ -138,6 +146,7 @@ pub struct LspTransport {
     stdout: BufReader<ChildStdout>,
     next_id: u64,
     request_timeout: Duration,
+    pending_notifications: Vec<LspNotification>,
 }
 
 impl LspTransport {
@@ -172,6 +181,7 @@ impl LspTransport {
             stdout: BufReader::new(stdout),
             next_id: 1,
             request_timeout,
+            pending_notifications: Vec::new(),
         })
     }
 
@@ -193,6 +203,7 @@ impl LspTransport {
             stdout: BufReader::new(stdout),
             next_id: 1,
             request_timeout,
+            pending_notifications: Vec::new(),
         }
     }
 
@@ -235,12 +246,27 @@ impl LspTransport {
 
         let method_owned = method.to_string();
         let timeout_duration = self.request_timeout;
-        let response = timeout(timeout_duration, self.read_response())
-            .await
-            .map_err(|_| LspTransportError::Timeout {
-                method: method_owned,
-                timeout: timeout_duration,
-            })??;
+        let response = match timeout(timeout_duration, async {
+            loop {
+                match self.read_message().await {
+                    Ok(LspServerMessage::Response(r)) => break Ok(r),
+                    Ok(LspServerMessage::Notification(n)) => {
+                        self.pending_notifications.push(n);
+                    }
+                    Err(e) => break Err(e),
+                }
+            }
+        })
+        .await
+        {
+            Ok(inner) => inner,
+            Err(_) => {
+                return Err(LspTransportError::Timeout {
+                    method: method_owned,
+                    timeout: timeout_duration,
+                })
+            }
+        }?;
 
         if response.jsonrpc != "2.0" {
             return Err(LspTransportError::InvalidResponse {
@@ -266,8 +292,57 @@ impl LspTransport {
         Ok(response)
     }
 
+    /// Read a single message from the server, returning either a response or
+    /// a server-initiated notification (e.g. `publishDiagnostics`).
+    pub async fn read_message(&mut self) -> Result<LspServerMessage, LspTransportError> {
+        let payload = self.read_frame().await?;
+        let value: JsonValue = serde_json::from_slice(&payload).map_err(|error| {
+            LspTransportError::InvalidResponse {
+                method: "unknown".to_string(),
+                details: error.to_string(),
+            }
+        })?;
+
+        // Responses have an "id" field; notifications have "method" but no "id"
+        if value.get("id").is_some() {
+            let response: LspResponse = serde_json::from_value(value).map_err(|error| {
+                LspTransportError::InvalidResponse {
+                    method: "unknown".to_string(),
+                    details: format!("failed to parse response: {error}"),
+                }
+            })?;
+            Ok(LspServerMessage::Response(response))
+        } else if value.get("method").is_some() {
+            let notification: LspNotification = serde_json::from_value(value).map_err(|error| {
+                LspTransportError::InvalidResponse {
+                    method: "unknown".to_string(),
+                    details: format!("failed to parse notification: {error}"),
+                }
+            })?;
+            Ok(LspServerMessage::Notification(notification))
+        } else {
+            Err(LspTransportError::InvalidResponse {
+                method: "unknown".to_string(),
+                details: "message has neither 'id' nor 'method'".to_string(),
+            })
+        }
+    }
+
+    /// Read a response from the server. Interleaved notifications are queued.
     pub async fn read_response(&mut self) -> Result<LspResponse, LspTransportError> {
-        self.read_jsonrpc_message().await
+        loop {
+            match self.read_message().await? {
+                LspServerMessage::Response(r) => return Ok(r),
+                LspServerMessage::Notification(n) => {
+                    self.pending_notifications.push(n);
+                }
+            }
+        }
+    }
+
+    /// Drain and return all queued server-initiated notifications.
+    pub fn drain_notifications(&mut self) -> Vec<LspNotification> {
+        std::mem::take(&mut self.pending_notifications)
     }
 
     pub async fn shutdown(&mut self) -> Result<(), LspTransportError> {
@@ -344,16 +419,6 @@ impl LspTransport {
 
         Ok(payload)
     }
-
-    async fn read_jsonrpc_message<T: serde::de::DeserializeOwned>(
-        &mut self,
-    ) -> Result<T, LspTransportError> {
-        let payload = self.read_frame().await?;
-        serde_json::from_slice(&payload).map_err(|error| LspTransportError::InvalidResponse {
-            method: "unknown".to_string(),
-            details: error.to_string(),
-        })
-    }
 }
 
 #[cfg(test)]