Improve MCP SSE error diagnostics

crates/tui/src/mcp.rs

@@ -1145,8 +1145,15 @@ impl McpTransport for SseTransport {
         .body(msg)
         .send()
         .await?;
-        if !response.status().is_success() {
-            anyhow::bail!("Failed to send message via SSE POST: {}", response.status());
+        let status = response.status();
+        if !status.is_success() {
+            let body_excerpt = bounded_body_excerpt(response, ERROR_BODY_PREVIEW_BYTES).await;
+            anyhow::bail!(
+                "MCP SSE POST rejected (transport=sse endpoint={} status={}): {}",
+                mask_url_secrets(endpoint),
+                status,
+                body_excerpt
+            );
         }
         Ok(())
     }
@@ -3450,6 +3457,49 @@ mod tests {
         );
     }
 
+    #[tokio::test]
+    async fn mcp_pool_call_tool_preserves_tool_names_with_dashes() {
+        let sent = Arc::new(Mutex::new(Vec::new()));
+        let transport = ScriptedValueTransport {
+            sent: Arc::clone(&sent),
+            responses: VecDeque::from([json_frame(serde_json::json!({
+                "jsonrpc": "2.0",
+                "id": 1,
+                "result": {"ok": true}
+            }))]),
+        };
+        let mut conn = test_connection(Box::new(transport));
+        conn.name = "dephy".to_string();
+        conn.tools = vec![McpTool {
+            name: "company--search".to_string(),
+            description: None,
+            input_schema: serde_json::json!({}),
+        }];
+
+        let mut pool = McpPool::new(McpConfig {
+            timeouts: McpTimeouts::default(),
+            servers: HashMap::new(),
+        });
+        pool.connections.insert("dephy".to_string(), conn);
+
+        let result = pool
+            .call_tool(
+                "mcp_dephy_company--search",
+                serde_json::json!({"query": "dephy"}),
+            )
+            .await
+            .unwrap();
+
+        assert_eq!(result, serde_json::json!({"ok": true}));
+        let sent = sent.lock().unwrap();
+        assert_eq!(sent[0]["method"], "tools/call");
+        assert_eq!(sent[0]["params"]["name"], "company--search");
+        assert_eq!(
+            sent[0]["params"]["arguments"],
+            serde_json::json!({"query": "dephy"})
+        );
+    }
+
     /// #1244: when an MCP stdio server fails to spawn, the underlying OS
     /// error (e.g. ENOENT for a missing binary) must reach the user via the
     /// snapshot.error string. Regression test for `err.to_string()` dropping
@@ -4143,6 +4193,90 @@ mod tests {
         server.abort();
     }
 
+    #[tokio::test]
+    async fn sse_post_error_includes_response_body_excerpt() {
+        use tokio::io::{AsyncReadExt, AsyncWriteExt};
+        use tokio::net::TcpListener;
+
+        let listener = TcpListener::bind("127.0.0.1:0").await.unwrap();
+        let addr = listener.local_addr().unwrap();
+        let cancel_token = tokio_util::sync::CancellationToken::new();
+        let server_cancel = cancel_token.clone();
+
+        let server = tokio::spawn(async move {
+            loop {
+                let Ok((mut socket, _)) = listener.accept().await else {
+                    break;
+                };
+                let server_cancel = server_cancel.clone();
+                tokio::spawn(async move {
+                    let mut request = Vec::new();
+                    let mut buf = [0; 1024];
+                    loop {
+                        let n = socket.read(&mut buf).await.unwrap();
+                        if n == 0 {
+                            return;
+                        }
+                        request.extend_from_slice(&buf[..n]);
+                        if request.windows(4).any(|window| window == b"\r\n\r\n") {
+                            break;
+                        }
+                    }
+                    let request = String::from_utf8_lossy(&request);
+                    if request.starts_with("GET /sse ") {
+                        socket
+                            .write_all(
+                                b"HTTP/1.1 200 OK\r\nContent-Type: text/event-stream\r\n\r\n",
+                            )
+                            .await
+                            .unwrap();
+                        socket
+                            .write_all(b"event: endpoint\ndata: /messages\n\n")
+                            .await
+                            .unwrap();
+                        server_cancel.cancelled().await;
+                    } else if request.starts_with("POST /messages ") {
+                        socket
+                            .write_all(
+                                b"HTTP/1.1 400 Bad Request\r\nContent-Type: application/json\r\nContent-Length: 25\r\n\r\n{\"error\":\"missing query\"}",
+                            )
+                            .await
+                            .unwrap();
+                    }
+                });
+            }
+        });
+
+        let client = reqwest::Client::new();
+        let url = format!("http://{addr}/sse");
+        let mut transport = SseTransport::connect(
+            client,
+            url,
+            HashMap::new(),
+            cancel_token.clone(),
+            Duration::from_secs(2),
+        )
+        .await
+        .unwrap();
+
+        let err = transport
+            .send(json_frame(serde_json::json!({
+                "jsonrpc": "2.0",
+                "id": 1,
+                "method": "initialize"
+            })))
+            .await
+            .expect_err("POST rejection should be returned");
+        let err = format!("{err:#}");
+        assert!(
+            err.contains("400 Bad Request") && err.contains("missing query"),
+            "SSE POST error should include status and body, got: {err}"
+        );
+
+        cancel_token.cancel();
+        server.abort();
+    }
+
     #[test]
     fn session_id_starts_none() {
         let transport = StreamableHttpTransport::new(