feat: fetch real GitHub social preview at build time

- build-index.ts scrapes og:image from each repo's GitHub page
- Stores as social_preview in index.json
- Custom social previews (repository-images.githubusercontent.com) preserved
- Falls back to auto-generated opengraph.githubassets.com if no custom set

Author: shreyas-lyzr

index.json

@@ -24,6 +24,7 @@
       ],
       "icon": null,
       "banner": null,
+      "social_preview": "https://opengraph.githubassets.com/fb12cdd7813bedc8e01dac838036f1878b14aeaccb5b00430bc015bc56bbc69e/shreyas-lyzr/agent-designer",
       "readme": "https://raw.githubusercontent.com/open-gitagent/registry/main/agents/shreyas-lyzr__agent-designer/README.md",
       "added_at": "2026-03-01"
     },
@@ -50,6 +51,7 @@
       ],
       "icon": null,
       "banner": null,
+      "social_preview": "https://repository-images.githubusercontent.com/1164987139/49ba99c6-5916-4bdd-8d28-dde492f22827",
       "readme": "https://raw.githubusercontent.com/open-gitagent/registry/main/agents/shreyas-lyzr__architect/README.md",
       "added_at": "2026-03-01"
     },
@@ -78,10 +80,11 @@
       ],
       "icon": null,
       "banner": null,
+      "social_preview": "https://opengraph.githubassets.com/f7d8761974c8926820b7d30a10eaa92595870d0c2c848b89cec7e0ca57b5f355/shreyas-lyzr/quant-sim",
       "readme": "https://raw.githubusercontent.com/open-gitagent/registry/main/agents/shreyas-lyzr__quant-sim/README.md",
       "added_at": "2026-03-01"
     }
   ],
   "total": 3,
-  "generated_at": "2026-03-01T14:22:43.997Z"
+  "generated_at": "2026-03-01T16:19:41.736Z"
 }

scripts/build-index.ts

@@ -38,6 +38,7 @@ interface AgentMetadata {
 interface IndexEntry extends Omit<AgentMetadata, "icon" | "banner"> {
   icon: string | null;
   banner: string | null;
+  social_preview: string | null;
   readme: string;
   added_at: string;
 }
@@ -63,6 +64,22 @@ function getFirstCommitDate(folderPath: string): string {
   return new Date().toISOString().split("T")[0];
 }
 
+function fetchSocialPreview(repoUrl: string): string | null {
+  try {
+    const html = execSync(`curl -sL "${repoUrl}"`, {
+      encoding: "utf-8",
+      timeout: 15_000,
+    });
+    const match = html.match(/property="og:image"\s+content="([^"]+)"/);
+    if (match?.[1] && !match[1].includes("avatars.githubusercontent.com")) {
+      return match[1];
+    }
+  } catch {
+    // fallback
+  }
+  return null;
+}
+
 function buildIndex(): Index {
   const agents: IndexEntry[] = [];
 
@@ -97,6 +114,9 @@ function buildIndex(): Index {
     const hasBanner = metadata.banner === true && existsSync(join(folderPath, "banner.png"));
     const addedAt = getFirstCommitDate(folderPath);
 
+    console.log(`  Fetching social preview for ${metadata.repository}...`);
+    const socialPreview = fetchSocialPreview(metadata.repository);
+
     const entry: IndexEntry = {
       name: metadata.name,
       author: metadata.author,
@@ -110,6 +130,7 @@ function buildIndex(): Index {
       adapters: metadata.adapters,
       icon: hasIcon ? `${RAW_BASE}/agents/${folder}/icon.png` : null,
       banner: hasBanner ? `${RAW_BASE}/agents/${folder}/banner.png` : null,
+      social_preview: socialPreview,
       readme: `${RAW_BASE}/agents/${folder}/README.md`,
       added_at: addedAt,
     };

site/public/index.json

@@ -24,6 +24,7 @@
       ],
       "icon": null,
       "banner": null,
+      "social_preview": "https://opengraph.githubassets.com/fb12cdd7813bedc8e01dac838036f1878b14aeaccb5b00430bc015bc56bbc69e/shreyas-lyzr/agent-designer",
       "readme": "https://raw.githubusercontent.com/open-gitagent/registry/main/agents/shreyas-lyzr__agent-designer/README.md",
       "added_at": "2026-03-01"
     },
@@ -50,6 +51,7 @@
       ],
       "icon": null,
       "banner": null,
+      "social_preview": "https://repository-images.githubusercontent.com/1164987139/49ba99c6-5916-4bdd-8d28-dde492f22827",
       "readme": "https://raw.githubusercontent.com/open-gitagent/registry/main/agents/shreyas-lyzr__architect/README.md",
       "added_at": "2026-03-01"
     },
@@ -78,10 +80,11 @@
       ],
       "icon": null,
       "banner": null,
+      "social_preview": "https://opengraph.githubassets.com/f7d8761974c8926820b7d30a10eaa92595870d0c2c848b89cec7e0ca57b5f355/shreyas-lyzr/quant-sim",
       "readme": "https://raw.githubusercontent.com/open-gitagent/registry/main/agents/shreyas-lyzr__quant-sim/README.md",
       "added_at": "2026-03-01"
     }
   ],
   "total": 3,
-  "generated_at": "2026-03-01T14:11:09.313Z"
+  "generated_at": "2026-03-01T16:19:41.736Z"
 }