fix: parse flat content arrays in Responses API input

When input is [{type: 'input_image', ...}, {type: 'input_text', text: '...'}],
the code was looking for items with role: 'user' which don't exist in flat
content arrays. Now extracts text from input_text items directly first,
falling back to role-based messages only if no flat text found.

Also adds debug header dump for MITM request forwarding.

src/api/responses.rs

@@ -80,7 +80,22 @@ fn extract_responses_input(
                     text_items
                 }
             } else {
-                // Normal input extraction (existing logic)
+                // Normal input extraction
+                // First try: flat content parts (input_text / input_image)
+                let flat_text: String = items
+                    .iter()
+                    .filter(|item| {
+                        let t = item["type"].as_str().unwrap_or("");
+                        t == "input_text" || t == "text"
+                    })
+                    .filter_map(|p| p["text"].as_str())
+                    .collect::<Vec<_>>()
+                    .join(" ");
+
+                if !flat_text.is_empty() {
+                    flat_text
+                } else {
+                    // Fallback: conversation-style with role: "user"
                     items
                         .iter()
                         .rev()
@@ -109,6 +124,7 @@ fn extract_responses_input(
                         .unwrap_or_default()
                 }
             }
+        }
         _ => String::new(),
     };
 

src/mitm/proxy.rs

@@ -633,6 +633,16 @@ async fn handle_http_over_tls(
         };
 
         // Forward the request — if write fails, reconnect and retry once
+        // DEBUG: dump headers and total size
+        if req_path.contains("streamGenerateContent") {
+            let hdr_end = find_headers_end(&request_buf).unwrap_or(request_buf.len());
+            let hdr_str = String::from_utf8_lossy(&request_buf[..hdr_end.min(request_buf.len())]);
+            info!(
+                total_buf_len = request_buf.len(),
+                body_len = request_buf.len() - hdr_end,
+                "MITM: sending request to upstream\n{hdr_str}"
+            );
+        }
         if let Err(e) = conn.write_all(&request_buf).await {
             debug!(domain, error = %e, "MITM: upstream write failed, reconnecting");
             let c = connect_upstream(domain, &upstream_config).await?;