feat: agent session retry + follow-up UX

- retry/route.ts: reset failed/stopped session and re-fire agent runner
  with optional continueTask follow-up text
- build/page.tsx: Retry button and Follow up input appear on failed/stopped
  sessions so users can continue without losing context or creating a
  duplicate session; task input hint clarifies each Run = new session

Made-with: Cursor

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

@@ -278,6 +278,9 @@ function AgentMode({ projectId, appName, appPath }: { projectId: string; appName
   const [approveMsg, setApproveMsg] = useState("");
   const [showApproveInput, setShowApproveInput] = useState(false);
   const [approveResult, setApproveResult] = useState<string | null>(null);
+  const [retrying, setRetrying] = useState(false);
+  const [followUp, setFollowUp] = useState("");
+  const [showFollowUp, setShowFollowUp] = useState(false);
   const outputRef = useCallback((el: HTMLDivElement | null) => {
     if (el) el.scrollTop = el.scrollHeight;
   }, []);
@@ -346,6 +349,24 @@ function AgentMode({ projectId, appName, appPath }: { projectId: string; appName
     setActiveSession(prev => prev ? { ...prev, status: "stopped" } : null);
   };
 
+  const handleRetry = async (continueTask?: string) => {
+    if (!activeSessionId) return;
+    setRetrying(true);
+    try {
+      const r = await fetch(`/api/projects/${projectId}/agent/sessions/${activeSessionId}/retry`, {
+        method: "POST",
+        headers: { "Content-Type": "application/json" },
+        body: JSON.stringify({ continueTask: continueTask?.trim() || undefined }),
+      });
+      const d = await r.json();
+      if (d.sessionId) {
+        setActiveSession(prev => prev ? { ...prev, status: "running", output: [], error: null } : null);
+        setShowFollowUp(false);
+        setFollowUp("");
+      }
+    } finally { setRetrying(false); }
+  };
+
   const handleApprove = async () => {
     if (!activeSessionId || !approveMsg.trim()) return;
     setApproving(true);
@@ -459,6 +480,57 @@ function AgentMode({ projectId, appName, appPath }: { projectId: string; appName
               )}
             </div>
 
+            {/* Retry / follow-up panel for failed or stopped sessions */}
+            {["failed", "stopped"].includes(activeSession.status) && (
+              <div style={{ borderTop: "1px solid #e8e4dc", background: "#fff", padding: "12px 20px", flexShrink: 0 }}>
+                {showFollowUp ? (
+                  <div style={{ display: "flex", flexDirection: "column", gap: 8 }}>
+                    <div style={{ fontSize: "0.72rem", color: "#6b6560", fontFamily: "Outfit, sans-serif" }}>
+                      Add a follow-up instruction (optional) then retry:
+                    </div>
+                    <div style={{ display: "flex", gap: 8, alignItems: "flex-end" }}>
+                      <textarea
+                        autoFocus
+                        value={followUp}
+                        onChange={e => setFollowUp(e.target.value)}
+                        onKeyDown={e => { if (e.key === "Enter" && (e.metaKey || e.ctrlKey)) handleRetry(followUp); if (e.key === "Escape") setShowFollowUp(false); }}
+                        placeholder="e.g. Also update the TypeScript types, or just leave blank to retry as-is…"
+                        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={() => handleRetry(followUp)} disabled={retrying}
+                          style={{ padding: "8px 14px", background: "#1a1a1a", color: "#fff", border: "none", borderRadius: 7, fontSize: "0.75rem", fontWeight: 600, cursor: "pointer", fontFamily: "Outfit, sans-serif", whiteSpace: "nowrap" }}>
+                          {retrying ? "Retrying…" : "Retry"}
+                        </button>
+                        <button onClick={() => setShowFollowUp(false)}
+                          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 retry · Esc to cancel · Same session, fresh run
+                    </div>
+                  </div>
+                ) : (
+                  <div style={{ display: "flex", gap: 8, alignItems: "center" }}>
+                    <div style={{ fontSize: "0.75rem", color: activeSession.status === "failed" ? "#c62828" : "#a09a90", fontFamily: "Outfit, sans-serif", flex: 1 }}>
+                      {activeSession.status === "failed" ? "Session failed — retry without losing context" : "Session stopped"}
+                    </div>
+                    <button onClick={() => handleRetry()} disabled={retrying}
+                      style={{ padding: "7px 14px", background: "#fef9f0", color: "#92400e", border: "1px solid #fde68a", borderRadius: 7, fontSize: "0.75rem", fontWeight: 600, cursor: "pointer", fontFamily: "Outfit, sans-serif", whiteSpace: "nowrap" }}>
+                      {retrying ? "Retrying…" : "↺ Retry"}
+                    </button>
+                    <button onClick={() => setShowFollowUp(true)}
+                      style={{ padding: "7px 14px", background: "#f0ece4", color: "#1a1a1a", border: "1px solid #e8e4dc", borderRadius: 7, fontSize: "0.75rem", cursor: "pointer", fontFamily: "Outfit, sans-serif", whiteSpace: "nowrap" }}>
+                      Follow up…
+                    </button>
+                  </div>
+                )}
+              </div>
+            )}
+
             {/* Changed files */}
             {activeSession.changed_files.length > 0 && (
               <div style={{ borderTop: "1px solid #e8e4dc", background: "#fff", padding: "12px 20px", flexShrink: 0 }}>
@@ -576,7 +648,7 @@ function AgentMode({ projectId, appName, appPath }: { projectId: string; appName
             </button>
           </div>
           <div style={{ fontSize: "0.65rem", color: "#b5b0a6", marginTop: 5, fontFamily: "Outfit, sans-serif" }}>
-            ⌘↵ to run · Session persists if you close the browser
+            ⌘↵ to start · Each task is a new session · Use "Follow up" on a failed session to continue it
           </div>
         </div>
       </div>

app/api/projects/[projectId]/agent/sessions/[sessionId]/retry/route.ts

@@ -0,0 +1,114 @@
+/**
+ * POST /api/projects/[projectId]/agent/sessions/[sessionId]/retry
+ *
+ * Re-run a failed or stopped session, optionally with a follow-up instruction.
+ * Resets the session row to `running` and fires the agent-runner again.
+ *
+ * Body: { continueTask?: string }
+ *   continueTask — if provided, appended to the original task so the agent
+ *                  understands what was already tried
+ */
+import { NextResponse } from "next/server";
+import { getServerSession } from "next-auth";
+import { authOptions } from "@/lib/auth/authOptions";
+import { query } from "@/lib/db-postgres";
+
+const AGENT_RUNNER_URL = process.env.AGENT_RUNNER_URL ?? "http://localhost:3333";
+
+export async function POST(
+  req: Request,
+  { params }: { params: Promise<{ projectId: string; sessionId: string }> }
+) {
+  try {
+    const { projectId, sessionId } = await params;
+    const session = await getServerSession(authOptions);
+    if (!session?.user?.email) {
+      return NextResponse.json({ error: "Unauthorized" }, { status: 401 });
+    }
+
+    const body = await req.json().catch(() => ({})) as { continueTask?: string };
+
+    // Verify ownership and load the original session
+    const rows = await query<{
+      id: string;
+      project_id: string;
+      app_name: string;
+      app_path: string;
+      task: string;
+      status: string;
+    }>(
+      `SELECT s.id, s.project_id, s.app_name, s.app_path, s.task, s.status
+       FROM agent_sessions s
+       JOIN fs_projects p ON p.id::text = s.project_id::text
+       JOIN fs_users u ON u.id = p.user_id
+       WHERE s.id = $1::uuid AND s.project_id::text = $2 AND u.data->>'email' = $3
+       LIMIT 1`,
+      [sessionId, projectId, session.user.email]
+    );
+
+    if (rows.length === 0) {
+      return NextResponse.json({ error: "Session not found" }, { status: 404 });
+    }
+
+    const s = rows[0];
+
+    if (!["failed", "stopped"].includes(s.status)) {
+      return NextResponse.json(
+        { error: `Session is ${s.status} — can only retry failed or stopped sessions` },
+        { status: 409 }
+      );
+    }
+
+    // Fetch giteaRepo from the project
+    const proj = await query<{ data: Record<string, unknown> }>(
+      `SELECT data FROM fs_projects WHERE id::text = $1 LIMIT 1`,
+      [projectId]
+    );
+    const giteaRepo = proj[0]?.data?.giteaRepo as string | undefined;
+
+    // Reset the session row so the frontend shows it as running again
+    await query(
+      `UPDATE agent_sessions
+       SET status = 'running',
+           error = NULL,
+           output = '[]'::jsonb,
+           changed_files = '[]'::jsonb,
+           started_at = now(),
+           completed_at = NULL,
+           updated_at = now()
+       WHERE id = $1::uuid`,
+      [sessionId]
+    );
+
+    // Re-fire the agent runner
+    fetch(`${AGENT_RUNNER_URL}/agent/execute`, {
+      method: "POST",
+      headers: { "Content-Type": "application/json" },
+      body: JSON.stringify({
+        sessionId,
+        projectId,
+        appName: s.app_name,
+        appPath: s.app_path,
+        giteaRepo,
+        task: s.task,
+        continueTask: body.continueTask?.trim() || undefined,
+      }),
+    }).catch(err => {
+      console.warn("[retry] runner not reachable:", err.message);
+      query(
+        `UPDATE agent_sessions
+         SET status = 'failed', error = 'Agent runner not reachable', completed_at = now(), updated_at = now()
+         WHERE id = $1::uuid`,
+        [sessionId]
+      ).catch(() => {});
+    });
+
+    return NextResponse.json({ sessionId, status: "running" });
+  } catch (err) {
+    console.error("[retry POST]", err);
+    return NextResponse.json(
+      { error: "Failed to retry session", details: err instanceof Error ? err.message : String(err) },
+      { status: 500 }
+    );
+  }
+}