fix(agent): context-aware task input, auto-select active session

- Running/pending: input locked with "agent is working" message
- Done: shows "+ Follow up" and "New task" buttons instead of open input
- No session: normal new-task input (unchanged UX)
- On mount: auto-selects the most recent running/pending session,
  falls back to latest session — so navigating away and back doesn't
  lose context and doesn't require manual re-selection

Made-with: Cursor

app/[workspace]/project/[projectId]/build/page.tsx

@@ -285,15 +285,26 @@ function AgentMode({ projectId, appName, appPath }: { projectId: string; appName
     if (el) el.scrollTop = el.scrollHeight;
   }, []);
 
-  // Load session list
+  // Load session list — auto-select the most recent active or last session
   useEffect(() => {
     if (!appName) return;
     setLoadingSessions(true);
     fetch(`/api/projects/${projectId}/agent/sessions`)
       .then(r => r.json())
-      .then(d => { setSessions(d.sessions ?? []); setLoadingSessions(false); })
+      .then(d => {
+        const list: AgentSession[] = d.sessions ?? [];
+        setSessions(list);
+        setLoadingSessions(false);
+        // Auto-select: prefer running/pending, then the most recent
+        if (list.length > 0 && !activeSessionId) {
+          const live = list.find(s => s.status === "running" || s.status === "pending");
+          const pick = live ?? list[0];
+          setActiveSessionId(pick.id);
+          setActiveSession(pick);
+        }
+      })
       .catch(() => setLoadingSessions(false));
-  }, [projectId, appName]);
+  }, [projectId, appName]); // eslint-disable-line react-hooks/exhaustive-deps
 
   // Adaptive polling — 500ms while running, 5s when idle
   useEffect(() => {
@@ -619,14 +630,94 @@ function AgentMode({ projectId, appName, appPath }: { projectId: string; appName
           </div>
         )}
 
-        {/* Task input */}
+        {/* Task input — context-aware */}
+        {(() => {
+          const st = activeSession?.status;
+
+          // Agent is actively working — lock input
+          if (st === "running" || st === "pending") {
+            return (
+              <div style={{ borderTop: "1px solid #e8e4dc", background: "#fff", padding: "12px 16px", flexShrink: 0 }}>
+                <div style={{ display: "flex", alignItems: "center", gap: 10 }}>
+                  <span style={{ width: 7, height: 7, borderRadius: "50%", background: "#3d5afe", flexShrink: 0, display: "inline-block" }} />
+                  <span style={{ fontSize: "0.78rem", color: "#6b6560", fontFamily: "Outfit, sans-serif", flex: 1 }}>
+                    Agent is working — wait for it to finish, or stop it above.
+                  </span>
+                </div>
+              </div>
+            );
+          }
+
+          // Session completed successfully — offer follow-up or new task
+          if (st === "done") {
+            return (
+              <div style={{ borderTop: "1px solid #e8e4dc", background: "#fff", padding: "12px 16px", flexShrink: 0 }}>
+                {showFollowUp ? (
+                  <div style={{ display: "flex", flexDirection: "column", gap: 8 }}>
+                    <div style={{ fontSize: "0.72rem", color: "#6b6560", fontFamily: "Outfit, sans-serif" }}>
+                      Describe the next thing to build (continues from this session's context):
+                    </div>
+                    <div style={{ display: "flex", gap: 8, alignItems: "flex-end" }}>
+                      <textarea
+                        autoFocus
+                        value={task}
+                        onChange={e => setTask(e.target.value)}
+                        onKeyDown={e => {
+                          if (e.key === "Enter" && (e.metaKey || e.ctrlKey)) { handleRun(); setShowFollowUp(false); }
+                          if (e.key === "Escape") { setShowFollowUp(false); setTask(""); }
+                        }}
+                        placeholder="e.g. Now add email notifications for the same feature…"
+                        rows={2}
+                        style={{
+                          flex: 1, resize: "none", border: "1px solid #e8e4dc", borderRadius: 7,
+                          padding: "8px 11px", fontSize: "0.78rem", fontFamily: "Outfit, sans-serif",
+                          outline: "none", background: "#faf8f5",
+                        }}
+                      />
+                      <div style={{ display: "flex", flexDirection: "column", gap: 6 }}>
+                        <button onClick={() => { handleRun(); setShowFollowUp(false); }} disabled={submitting || !task.trim()}
+                          style={{ padding: "8px 14px", background: task.trim() ? "#1a1a1a" : "#e8e4dc", color: task.trim() ? "#fff" : "#a09a90", border: "none", borderRadius: 7, fontSize: "0.75rem", fontWeight: 600, cursor: task.trim() ? "pointer" : "default", fontFamily: "Outfit, sans-serif", whiteSpace: "nowrap" }}>
+                          {submitting ? "Starting…" : "Run"}
+                        </button>
+                        <button onClick={() => { setShowFollowUp(false); setTask(""); }}
+                          style={{ padding: "6px 14px", background: "transparent", color: "#a09a90", border: "1px solid #e8e4dc", borderRadius: 7, fontSize: "0.73rem", cursor: "pointer", fontFamily: "Outfit, sans-serif" }}>
+                          Cancel
+                        </button>
+                      </div>
+                    </div>
+                    <div style={{ fontSize: "0.63rem", color: "#b5b0a6", fontFamily: "Outfit, sans-serif" }}>
+                      ⌘↵ to run · Esc to cancel · Starts a new session for this task
+                    </div>
+                  </div>
+                ) : (
+                  <div style={{ display: "flex", gap: 8, alignItems: "center" }}>
+                    <span style={{ fontSize: "0.75rem", color: "#2e7d32", fontFamily: "Outfit, sans-serif", flex: 1 }}>
+                      ✓ Done — approve the changes above, or continue building.
+                    </span>
+                    <button onClick={() => setShowFollowUp(true)}
+                      style={{ padding: "7px 14px", background: "#f0ece4", color: "#1a1a1a", border: "1px solid #e8e4dc", borderRadius: 7, fontSize: "0.75rem", fontWeight: 600, cursor: "pointer", fontFamily: "Outfit, sans-serif", whiteSpace: "nowrap" }}>
+                      + Follow up
+                    </button>
+                    <button onClick={() => { setActiveSession(null); setActiveSessionId(null); setTask(""); }}
+                      style={{ padding: "7px 14px", background: "transparent", color: "#a09a90", border: "1px solid #e8e4dc", borderRadius: 7, fontSize: "0.75rem", cursor: "pointer", fontFamily: "Outfit, sans-serif", whiteSpace: "nowrap" }}>
+                      New task
+                    </button>
+                  </div>
+                )}
+              </div>
+            );
+          }
+
+          // No active session (or failed/stopped handled above) — new task input
+          if (!activeSession) {
+            return (
               <div style={{ borderTop: "1px solid #e8e4dc", background: "#fff", padding: "12px 16px", flexShrink: 0 }}>
                 <div style={{ display: "flex", gap: 8, alignItems: "flex-end" }}>
                   <textarea
                     value={task}
                     onChange={e => setTask(e.target.value)}
                     onKeyDown={e => { if (e.key === "Enter" && (e.metaKey || e.ctrlKey)) handleRun(); }}
-              placeholder={`Tell the agent what to build in ${appName || "this app"}…`}
+                    placeholder={`Describe what to build in ${appName || "this app"}…`}
                     rows={2}
                     style={{
                       flex: 1, resize: "none", border: "1px solid #e8e4dc", borderRadius: 8,
@@ -648,9 +739,14 @@ function AgentMode({ projectId, appName, appPath }: { projectId: string; appName
                   </button>
                 </div>
                 <div style={{ fontSize: "0.65rem", color: "#b5b0a6", marginTop: 5, fontFamily: "Outfit, sans-serif" }}>
-            ⌘↵ to start · Each task is a new session · Use "Follow up" on a failed session to continue it
+                  ⌘↵ to start · The agent works autonomously until done · You approve before anything is committed
                 </div>
               </div>
+            );
+          }
+
+          return null;
+        })()}
       </div>
     </div>
   );