feat: add og images

bun.lock

···
     "": {
       "name": "traverse",
       "dependencies": {
+        "@fontsource/inter": "^5.2.8",
         "@modelcontextprotocol/sdk": "^1.26.0",
+        "@resvg/resvg-wasm": "^2.6.2",
+        "satori": "^0.19.1",
       },
       "devDependencies": {
         "@types/bun": "latest",
···
     },
   },
   "packages": {
+    "@fontsource/inter": ["@fontsource/inter@5.2.8", "", {}, "sha512-P6r5WnJoKiNVV+zvW2xM13gNdFhAEpQ9dQJHt3naLvfg+LkF2ldgSLiF4T41lf1SQCM9QmkqPTn4TH568IRagg=="],
+
     "@hono/node-server": ["@hono/node-server@1.19.9", "", { "peerDependencies": { "hono": "^4" } }, "sha512-vHL6w3ecZsky+8P5MD+eFfaGTyCeOHUIFYMGpQGbrBTSmNNoxv0if69rEZ5giu36weC5saFuznL411gRX7bJDw=="],
 
     "@modelcontextprotocol/sdk": ["@modelcontextprotocol/sdk@1.26.0", "", { "dependencies": { "@hono/node-server": "^1.19.9", "ajv": "^8.17.1", "ajv-formats": "^3.0.1", "content-type": "^1.0.5", "cors": "^2.8.5", "cross-spawn": "^7.0.5", "eventsource": "^3.0.2", "eventsource-parser": "^3.0.0", "express": "^5.2.1", "express-rate-limit": "^8.2.1", "hono": "^4.11.4", "jose": "^6.1.3", "json-schema-typed": "^8.0.2", "pkce-challenge": "^5.0.0", "raw-body": "^3.0.0", "zod": "^3.25 || ^4.0", "zod-to-json-schema": "^3.25.1" }, "peerDependencies": { "@cfworker/json-schema": "^4.1.1" }, "optionalPeers": ["@cfworker/json-schema"] }, "sha512-Y5RmPncpiDtTXDbLKswIJzTqu2hyBKxTNsgKqKclDbhIgg1wgtf1fRuvxgTnRfcnxtvvgbIEcqUOzZrJ6iSReg=="],
 
+    "@resvg/resvg-wasm": ["@resvg/resvg-wasm@2.6.2", "", {}, "sha512-FqALmHI8D4o6lk/LRWDnhw95z5eO+eAa6ORjVg09YRR7BkcM6oPHU9uyC0gtQG5vpFLvgpeU4+zEAz2H8APHNw=="],
+
+    "@shuding/opentype.js": ["@shuding/opentype.js@1.4.0-beta.0", "", { "dependencies": { "fflate": "^0.7.3", "string.prototype.codepointat": "^0.2.1" }, "bin": { "ot": "bin/ot" } }, "sha512-3NgmNyH3l/Hv6EvsWJbsvpcpUba6R8IREQ83nH83cyakCw7uM1arZKNfHwv1Wz6jgqrF/j4x5ELvR6PnK9nTcA=="],
+
     "@types/bun": ["@types/bun@1.3.8", "", { "dependencies": { "bun-types": "1.3.8" } }, "sha512-3LvWJ2q5GerAXYxO2mffLTqOzEu5qnhEAlh48Vnu8WQfnmSwbgagjGZV6BoHKJztENYEDn6QmVd949W4uESRJA=="],
 
     "@types/node": ["@types/node@25.2.2", "", { "dependencies": { "undici-types": "~7.16.0" } }, "sha512-BkmoP5/FhRYek5izySdkOneRyXYN35I860MFAGupTdebyE66uZaR+bXLHq8k4DirE5DwQi3NuhvRU1jqTVwUrQ=="],
···
 
     "ajv-formats": ["ajv-formats@3.0.1", "", { "dependencies": { "ajv": "^8.0.0" } }, "sha512-8iUql50EUR+uUcdRQ3HDqa6EVyo3docL8g5WJ3FNcWmu62IbkGUue/pEyLBW8VGKKucTPgqeks4fIU1DA4yowQ=="],
 
+    "base64-js": ["base64-js@0.0.8", "", {}, "sha512-3XSA2cR/h/73EzlXXdU6YNycmYI7+kicTxks4eJg2g39biHR84slg2+des+p7iHYhbRg/udIS4TD53WabcOUkw=="],
+
     "body-parser": ["body-parser@2.2.2", "", { "dependencies": { "bytes": "^3.1.2", "content-type": "^1.0.5", "debug": "^4.4.3", "http-errors": "^2.0.0", "iconv-lite": "^0.7.0", "on-finished": "^2.4.1", "qs": "^6.14.1", "raw-body": "^3.0.1", "type-is": "^2.0.1" } }, "sha512-oP5VkATKlNwcgvxi0vM0p/D3n2C3EReYVX+DNYs5TjZFn/oQt2j+4sVJtSMr18pdRr8wjTcBl6LoV+FUwzPmNA=="],
 
     "bun-types": ["bun-types@1.3.8", "", { "dependencies": { "@types/node": "*" } }, "sha512-fL99nxdOWvV4LqjmC+8Q9kW3M4QTtTR1eePs94v5ctGqU8OeceWrSUaRw3JYb7tU3FkMIAjkueehrHPPPGKi5Q=="],
···
 
     "call-bound": ["call-bound@1.0.4", "", { "dependencies": { "call-bind-apply-helpers": "^1.0.2", "get-intrinsic": "^1.3.0" } }, "sha512-+ys997U96po4Kx/ABpBCqhA9EuxJaQWDQg7295H4hBphv3IZg0boBKuwYpt4YXp6MZ5AmZQnU/tyMTlRpaSejg=="],
 
+    "camelize": ["camelize@1.0.1", "", {}, "sha512-dU+Tx2fsypxTgtLoE36npi3UqcjSSMNYfkqgmoEhtZrraP5VWq0K7FkWVTYa8eMPtnU/G2txVsfdCJTn9uzpuQ=="],
+
+    "color-name": ["color-name@1.1.4", "", {}, "sha512-dOy+3AuW3a2wNbZHIuMZpTcgjGuLU/uBL/ubcZF9OXbDo8ff4O8yVp5Bf0efS8uEoYo5q4Fx7dY9OgQGXgAsQA=="],
+
     "content-disposition": ["content-disposition@1.0.1", "", {}, "sha512-oIXISMynqSqm241k6kcQ5UwttDILMK4BiurCfGEREw6+X9jkkpEe5T9FZaApyLGGOnFuyMWZpdolTXMtvEJ08Q=="],
 
     "content-type": ["content-type@1.0.5", "", {}, "sha512-nTjqfcBFEipKdXCv4YDQWCfmcLZKm81ldF0pAopTvyrFGVbcR6P/VAAd5G7N+0tTr8QqiU0tFadD6FK4NtJwOA=="],
···
     "cors": ["cors@2.8.6", "", { "dependencies": { "object-assign": "^4", "vary": "^1" } }, "sha512-tJtZBBHA6vjIAaF6EnIaq6laBBP9aq/Y3ouVJjEfoHbRBcHBAHYcMh/w8LDrk2PvIMMq8gmopa5D4V8RmbrxGw=="],
 
     "cross-spawn": ["cross-spawn@7.0.6", "", { "dependencies": { "path-key": "^3.1.0", "shebang-command": "^2.0.0", "which": "^2.0.1" } }, "sha512-uV2QOWP2nWzsy2aMp8aRibhi9dlzF5Hgh5SHaB9OiTGEyDTiJJyx0uy51QXdyWbtAHNua4XJzUKca3OzKUd3vA=="],
+
+    "css-background-parser": ["css-background-parser@0.1.0", "", {}, "sha512-2EZLisiZQ+7m4wwur/qiYJRniHX4K5Tc9w93MT3AS0WS1u5kaZ4FKXlOTBhOjc+CgEgPiGY+fX1yWD8UwpEqUA=="],
+
+    "css-box-shadow": ["css-box-shadow@1.0.0-3", "", {}, "sha512-9jaqR6e7Ohds+aWwmhe6wILJ99xYQbfmK9QQB9CcMjDbTxPZjwEmUQpU91OG05Xgm8BahT5fW+svbsQGjS/zPg=="],
+
+    "css-color-keywords": ["css-color-keywords@1.0.0", "", {}, "sha512-FyyrDHZKEjXDpNJYvVsV960FiqQyXc/LlYmsxl2BcdMb2WPx0OGRVgTg55rPSyLSNMqP52R9r8geSp7apN3Ofg=="],
+
+    "css-gradient-parser": ["css-gradient-parser@0.0.17", "", {}, "sha512-w2Xy9UMMwlKtou0vlRnXvWglPAceXCTtcmVSo8ZBUvqCV5aXEFP/PC6d+I464810I9FT++UACwTD5511bmGPUg=="],
+
+    "css-to-react-native": ["css-to-react-native@3.2.0", "", { "dependencies": { "camelize": "^1.0.0", "css-color-keywords": "^1.0.0", "postcss-value-parser": "^4.0.2" } }, "sha512-e8RKaLXMOFii+02mOlqwjbD00KSEKqblnpO9e++1aXS1fPQOpS1YoqdVHBqPjHNoxeF2mimzVqawm2KCbEdtHQ=="],
 
     "debug": ["debug@4.4.3", "", { "dependencies": { "ms": "^2.1.3" } }, "sha512-RGwwWnwQvkVfavKVt22FGLw+xYSdzARwm0ru6DhTVA3umU5hZc28V3kO4stgYryrTlLpuvgI9GiijltAjNbcqA=="],
 
···
 
     "ee-first": ["ee-first@1.1.1", "", {}, "sha512-WMwm9LhRUo+WUaRN+vRuETqG89IgZphVSNkdFgeb6sS/E4OrDIN7t48CAewSHXc6C8lefD8KKfr5vY61brQlow=="],
 
+    "emoji-regex-xs": ["emoji-regex-xs@2.0.1", "", {}, "sha512-1QFuh8l7LqUcKe24LsPUNzjrzJQ7pgRwp1QMcZ5MX6mFplk2zQ08NVCM84++1cveaUUYtcCYHmeFEuNg16sU4g=="],
+
     "encodeurl": ["encodeurl@2.0.0", "", {}, "sha512-Q0n9HRi4m6JuGIV1eFlmvJB7ZEVxu93IrMyiMsGC0lrMJMWzRgx6WGquyfQgZVb31vhGgXnfmPNNXmxnOkRBrg=="],
 
     "es-define-property": ["es-define-property@1.0.1", "", {}, "sha512-e3nRfgfUZ4rNGL232gUgX06QNyyez04KdjFrF+LTRoOXmrOgFKDg4BCdsjW8EnT69eqdYGmRpJwiPVYNrCaW3g=="],
···
 
     "fast-uri": ["fast-uri@3.1.0", "", {}, "sha512-iPeeDKJSWf4IEOasVVrknXpaBV0IApz/gp7S2bb7Z4Lljbl2MGJRqInZiUrQwV16cpzw/D3S5j5Julj/gT52AA=="],
 
+    "fflate": ["fflate@0.7.4", "", {}, "sha512-5u2V/CDW15QM1XbbgS+0DfPxVB+jUKhWEKuuFuHncbk3tEEqzmoXL+2KyOFuKGqOnmdIy0/davWF1CkuwtibCw=="],
+
     "finalhandler": ["finalhandler@2.1.1", "", { "dependencies": { "debug": "^4.4.0", "encodeurl": "^2.0.0", "escape-html": "^1.0.3", "on-finished": "^2.4.1", "parseurl": "^1.3.3", "statuses": "^2.0.1" } }, "sha512-S8KoZgRZN+a5rNwqTxlZZePjT/4cnm0ROV70LedRHZ0p8u9fRID0hJUZQpkKLzro8LfmC8sx23bY6tVNxv8pQA=="],
 
     "forwarded": ["forwarded@0.2.0", "", {}, "sha512-buRG0fpBtRHSTCOASe6hD258tEubFoRLb4ZNA6NxMVHNw2gOcwHo9wyablzMzOA5z9xA9L1KNjk/Nt6MT9aYow=="],
···
     "has-symbols": ["has-symbols@1.1.0", "", {}, "sha512-1cDNdwJ2Jaohmb3sg4OmKaMBwuC48sYni5HUw2DvsC8LjGTLK9h+eb1X6RyuOHe4hT0ULCW68iomhjUoKUqlPQ=="],
 
     "hasown": ["hasown@2.0.2", "", { "dependencies": { "function-bind": "^1.1.2" } }, "sha512-0hJU9SCPvmMzIBdZFqNPXWa6dqh7WdH0cII9y+CyS8rG3nL48Bclra9HmKhVVUHyPWNH5Y7xDwAB7bfgSjkUMQ=="],
+
+    "hex-rgb": ["hex-rgb@4.3.0", "", {}, "sha512-Ox1pJVrDCyGHMG9CFg1tmrRUMRPRsAWYc/PinY0XzJU4K7y7vjNoLKIQ7BR5UJMCxNN8EM1MNDmHWA/B3aZUuw=="],
 
     "hono": ["hono@4.11.9", "", {}, "sha512-Eaw2YTGM6WOxA6CXbckaEvslr2Ne4NFsKrvc0v97JD5awbmeBLO5w9Ho9L9kmKonrwF9RJlW6BxT1PVv/agBHQ=="],
 
···
 
     "json-schema-typed": ["json-schema-typed@8.0.2", "", {}, "sha512-fQhoXdcvc3V28x7C7BMs4P5+kNlgUURe2jmUT1T//oBRMDrqy1QPelJimwZGo7Hg9VPV3EQV5Bnq4hbFy2vetA=="],
 
+    "linebreak": ["linebreak@1.1.0", "", { "dependencies": { "base64-js": "0.0.8", "unicode-trie": "^2.0.0" } }, "sha512-MHp03UImeVhB7XZtjd0E4n6+3xr5Dq/9xI/5FptGk5FrbDR3zagPa2DS6U8ks/3HjbKWG9Q1M2ufOzxV2qLYSQ=="],
+
     "math-intrinsics": ["math-intrinsics@1.1.0", "", {}, "sha512-/IXtbwEk5HTPyEwyKX6hGkYXxM9nbj64B+ilVJnC/R6B0pH5G4V3b0pVbL7DBj4tkhBAppbQUlf6F6Xl9LHu1g=="],
 
     "media-typer": ["media-typer@1.1.0", "", {}, "sha512-aisnrDP4GNe06UcKFnV5bfMNPBUw4jsLGaWwWfnH3v02GnBuXX2MCVn5RbrWo0j3pczUilYblq7fQ7Nw2t5XKw=="],
···
     "on-finished": ["on-finished@2.4.1", "", { "dependencies": { "ee-first": "1.1.1" } }, "sha512-oVlzkg3ENAhCk2zdv7IJwd/QUD4z2RxRwpkcGY8psCVcCYZNq4wYnVWALHM+brtuJjePWiYF/ClmuDr8Ch5+kg=="],
 
     "once": ["once@1.4.0", "", { "dependencies": { "wrappy": "1" } }, "sha512-lNaJgI+2Q5URQBkccEKHTQOPaXdUxnZZElQTZY0MFUAuaEqe1E+Nyvgdz/aIyNi6Z9MzO5dv1H8n58/GELp3+w=="],
+
+    "pako": ["pako@0.2.9", "", {}, "sha512-NUcwaKxUxWrZLpDG+z/xZaCgQITkA/Dv4V/T6bw7VON6l1Xz/VnrBqrYjZQ12TamKHzITTfOEIYUj48y2KXImA=="],
+
+    "parse-css-color": ["parse-css-color@0.2.1", "", { "dependencies": { "color-name": "^1.1.4", "hex-rgb": "^4.1.0" } }, "sha512-bwS/GGIFV3b6KS4uwpzCFj4w297Yl3uqnSgIPsoQkx7GMLROXfMnWvxfNkL0oh8HVhZA4hvJoEoEIqonfJ3BWg=="],
 
     "parseurl": ["parseurl@1.3.3", "", {}, "sha512-CiyeOxFT/JZyN5m0z9PfXw4SCBJ6Sygz1Dpl0wqjlhDEGGBP1GnsUVEL0p63hoG1fcj3fHynXi9NYO4nWOL+qQ=="],
 
···
 
     "pkce-challenge": ["pkce-challenge@5.0.1", "", {}, "sha512-wQ0b/W4Fr01qtpHlqSqspcj3EhBvimsdh0KlHhH8HRZnMsEa0ea2fTULOXOS9ccQr3om+GcGRk4e+isrZWV8qQ=="],
 
+    "postcss-value-parser": ["postcss-value-parser@4.2.0", "", {}, "sha512-1NNCs6uurfkVbeXG4S8JFT9t19m45ICnif8zWLd5oPSZ50QnwMfK+H3jv408d4jw/7Bttv5axS5IiHoLaVNHeQ=="],
+
     "proxy-addr": ["proxy-addr@2.0.7", "", { "dependencies": { "forwarded": "0.2.0", "ipaddr.js": "1.9.1" } }, "sha512-llQsMLSUDUPT44jdrU/O37qlnifitDP+ZwrmmZcoSKyLKvtZxpyV0n2/bD/N4tBAAZ/gJEdZU7KMraoK1+XYAg=="],
 
     "qs": ["qs@6.14.1", "", { "dependencies": { "side-channel": "^1.1.0" } }, "sha512-4EK3+xJl8Ts67nLYNwqw/dsFVnCf+qR7RgXSK9jEEm9unao3njwMDdmsdvoKBKHzxd7tCYz5e5M+SnMjdtXGQQ=="],
···
     "router": ["router@2.2.0", "", { "dependencies": { "debug": "^4.4.0", "depd": "^2.0.0", "is-promise": "^4.0.0", "parseurl": "^1.3.3", "path-to-regexp": "^8.0.0" } }, "sha512-nLTrUKm2UyiL7rlhapu/Zl45FwNgkZGaCpZbIHajDYgwlJCOzLSk+cIPAnsEqV955GjILJnKbdQC1nVPz+gAYQ=="],
 
     "safer-buffer": ["safer-buffer@2.1.2", "", {}, "sha512-YZo3K82SD7Riyi0E1EQPojLz7kpepnSQI9IyPbHHg1XXXevb5dJI7tpyN2ADxGcQbHG7vcyRHk0cbwqcQriUtg=="],
+
+    "satori": ["satori@0.19.1", "", { "dependencies": { "@shuding/opentype.js": "1.4.0-beta.0", "css-background-parser": "^0.1.0", "css-box-shadow": "1.0.0-3", "css-gradient-parser": "^0.0.17", "css-to-react-native": "^3.0.0", "emoji-regex-xs": "^2.0.1", "escape-html": "^1.0.3", "linebreak": "^1.1.0", "parse-css-color": "^0.2.1", "postcss-value-parser": "^4.2.0", "yoga-layout": "^3.2.1" } }, "sha512-/XaT/JiWLfNlgjlQdde4wXB1/6F+FEze9c3OW2QIH0ywsfOrY57YOetgESWyOFHW3JfEQ6dJAo2U9Xwb7+DDAw=="],
 
     "send": ["send@1.2.1", "", { "dependencies": { "debug": "^4.4.3", "encodeurl": "^2.0.0", "escape-html": "^1.0.3", "etag": "^1.8.1", "fresh": "^2.0.0", "http-errors": "^2.0.1", "mime-types": "^3.0.2", "ms": "^2.1.3", "on-finished": "^2.4.1", "range-parser": "^1.2.1", "statuses": "^2.0.2" } }, "sha512-1gnZf7DFcoIcajTjTwjwuDjzuz4PPcY2StKPlsGAQ1+YH20IRVrBaXSWmdjowTJ6u8Rc01PoYOGHXfP1mYcZNQ=="],
 
···
 
     "statuses": ["statuses@2.0.2", "", {}, "sha512-DvEy55V3DB7uknRo+4iOGT5fP1slR8wQohVdknigZPMpMstaKJQWhwiYBACJE3Ul2pTnATihhBYnRhZQHGBiRw=="],
 
+    "string.prototype.codepointat": ["string.prototype.codepointat@0.2.1", "", {}, "sha512-2cBVCj6I4IOvEnjgO/hWqXjqBGsY+zwPmHl12Srk9IXSZ56Jwwmy+66XO5Iut/oQVR7t5ihYdLB0GMa4alEUcg=="],
+
+    "tiny-inflate": ["tiny-inflate@1.0.3", "", {}, "sha512-pkY1fj1cKHb2seWDy0B16HeWyczlJA9/WW3u3c4z/NiWDsO3DOU5D7nhTLE9CF0yXv/QZFY7sEJmj24dK+Rrqw=="],
+
     "toidentifier": ["toidentifier@1.0.1", "", {}, "sha512-o5sSPKEkg/DIQNmH43V0/uerLrpzVedkUh8tGNvaeXpfpuwjKenlSox/2O/BTlZUtEe+JG7s5YhEz608PlAHRA=="],
 
     "type-is": ["type-is@2.0.1", "", { "dependencies": { "content-type": "^1.0.5", "media-typer": "^1.1.0", "mime-types": "^3.0.0" } }, "sha512-OZs6gsjF4vMp32qrCbiVSkrFmXtG/AZhY3t0iAMrMBiAZyV9oALtXO8hsrHbMXF9x6L3grlFuwW2oAz7cav+Gw=="],
···
 
     "undici-types": ["undici-types@7.16.0", "", {}, "sha512-Zz+aZWSj8LE6zoxD+xrjh4VfkIG8Ya6LvYkZqtUQGJPZjYl53ypCaUwWqo7eI0x66KBGeRo+mlBEkMSeSZ38Nw=="],
 
+    "unicode-trie": ["unicode-trie@2.0.0", "", { "dependencies": { "pako": "^0.2.5", "tiny-inflate": "^1.0.0" } }, "sha512-x7bc76x0bm4prf1VLg79uhAzKw8DVboClSN5VxJuQ+LKDOVEW9CdH+VY7SP+vX7xCYQqzzgQpFqz15zeLvAtZQ=="],
+
     "unpipe": ["unpipe@1.0.0", "", {}, "sha512-pjy2bYhSsufwWlKwPc+l3cN7+wuJlK6uz0YdJEOlQDbl6jo/YlPi4mb8agUkVC8BF7V8NuzeyPNqRksA3hztKQ=="],
 
     "vary": ["vary@1.1.2", "", {}, "sha512-BNGbWLfd0eUPabhkXUVm0j8uuvREyTh5ovRa/dyow/BqAbZJyC+5fU+IzQOzmAKzYqYRAISoRhdQr3eIZ/PXqg=="],
···
     "which": ["which@2.0.2", "", { "dependencies": { "isexe": "^2.0.0" }, "bin": { "node-which": "./bin/node-which" } }, "sha512-BLI3Tl1TW3Pvl70l3yq3Y64i+awpwXqsGBYWkkqMtnbXgrMD+yj7rhW0kuEDxzJaYXGjEW5ogapKNMEKNMjibA=="],
 
     "wrappy": ["wrappy@1.0.2", "", {}, "sha512-l4Sp/DRseor9wL6EvV2+TuQn63dMkPjZ/sp9XkghTEbV9KlPS1xUsZ3u7/IQO4wxtcFB4bgpQPRcR3QCvezPcQ=="],
+
+    "yoga-layout": ["yoga-layout@3.2.1", "", {}, "sha512-0LPOt3AxKqMdFBZA3HBAt/t/8vIKq7VaQYbuA8WxCgung+p9TVyKRYdpvCb80HcdTN2NkbIKbhNwKUfm3tQywQ=="],
 
     "zod": ["zod@4.3.6", "", {}, "sha512-rftlrkhHZOcjDwkGlnUtZZkvaPHCsDATp4pGpuOOMDaTdDDXF91wuVDJoWoPsKX/3YPQ5fHuF3STjcYyKr+Qhg=="],
 

package.json

···
     "typescript": "^5"
   },
   "dependencies": {
-    "@modelcontextprotocol/sdk": "^1.26.0"
+    "@fontsource/inter": "^5.2.8",
+    "@modelcontextprotocol/sdk": "^1.26.0",
+    "@resvg/resvg-wasm": "^2.6.2",
+    "satori": "^0.19.1"
   }
 }

src/index.ts

···
 import { generateViewerHTML } from "./template.ts";
 import type { WalkthroughDiagram } from "./types.ts";
 import { initDb, loadAllDiagrams, saveDiagram, deleteDiagramFromDb, generateId, getSharedUrl, saveSharedUrl } from "./storage.ts";
+import { generateOgImage } from "./og.ts";
 import { loadConfig } from "./config.ts";
 
 const PORT = parseInt(process.env.TRAVERSE_PORT || "4173", 10);
···
     port: PORT,
     async fetch(req) {
       const url = new URL(req.url);
+
+      // OG image route — must be matched before /diagram/:id
+      const ogMatch = url.pathname.match(/^\/diagram\/([\w-]+)\/og\.png$/);
+      if (ogMatch) {
+        const id = ogMatch[1]!;
+        const diagram = diagrams.get(id);
+        if (!diagram) {
+          return new Response("Not found", { status: 404 });
+        }
+        const nodeNames = Object.values(diagram.nodes).map(n => n.title);
+        const png = await generateOgImage(id, diagram.summary, nodeNames);
+        return new Response(png, {
+          headers: {
+            "Content-Type": "image/png",
+            "Cache-Control": "public, max-age=86400",
+          },
+        });
+      }
+
       const diagramMatch = url.pathname.match(/^\/diagram\/([\w-]+)$/);
 
       if (diagramMatch) {
···
           shareServerUrl: config.shareServerUrl,
           diagramId: id,
           existingShareUrl: existingShareUrl ?? undefined,
+          baseUrl: url.origin,
         }), {
           headers: { "Content-Type": "text/html; charset=utf-8" },
         });

src/og.ts

···
+import satori from "satori";
+import { initWasm, Resvg } from "@resvg/resvg-wasm";
+import { join } from "path";
+
+// Load Inter font files (woff, not woff2 — satori doesn't support woff2)
+const fontsDir = join(import.meta.dir, "../node_modules/@fontsource/inter/files");
+const [interRegular, interBold] = await Promise.all([
+  Bun.file(join(fontsDir, "inter-latin-400-normal.woff")).arrayBuffer(),
+  Bun.file(join(fontsDir, "inter-latin-700-normal.woff")).arrayBuffer(),
+]);
+
+// Initialize resvg-wasm
+const wasmPath = join(import.meta.dir, "../node_modules/@resvg/resvg-wasm/index_bg.wasm");
+await initWasm(Bun.file(wasmPath).arrayBuffer());
+
+// Cache generated images by diagram ID
+const cache = new Map<string, Buffer>();
+
+export async function generateOgImage(
+  id: string,
+  summary: string,
+  nodeNames: string[],
+): Promise<Buffer> {
+  const cached = cache.get(id);
+  if (cached) return cached;
+
+  const nodeCount = nodeNames.length;
+  const displayNodes = nodeNames.slice(0, 8);
+  const extra = nodeCount > 8 ? nodeCount - 8 : 0;
+
+  const svg = await satori(
+    {
+      type: "div",
+      props: {
+        style: {
+          width: "100%",
+          height: "100%",
+          display: "flex",
+          flexDirection: "column",
+          justifyContent: "space-between",
+          padding: "60px",
+          backgroundColor: "#0a0a0a",
+          color: "#e5e5e5",
+          fontFamily: "Inter",
+        },
+        children: [
+          // Top: Traverse label
+          {
+            type: "div",
+            props: {
+              style: {
+                display: "flex",
+                alignItems: "center",
+                gap: "10px",
+              },
+              children: [
+                {
+                  type: "div",
+                  props: {
+                    style: {
+                      fontSize: "20px",
+                      fontWeight: 700,
+                      color: "#a3a3a3",
+                      letterSpacing: "0.05em",
+                      textTransform: "uppercase" as const,
+                    },
+                    children: "Traverse",
+                  },
+                },
+              ],
+            },
+          },
+          // Middle: Summary headline
+          {
+            type: "div",
+            props: {
+              style: {
+                display: "flex",
+                flexDirection: "column",
+                gap: "24px",
+                flex: 1,
+                justifyContent: "center",
+              },
+              children: [
+                {
+                  type: "div",
+                  props: {
+                    style: {
+                      fontSize: summary.length > 60 ? "36px" : "44px",
+                      fontWeight: 700,
+                      lineHeight: 1.2,
+                      color: "#e5e5e5",
+                      overflow: "hidden",
+                      textOverflow: "ellipsis",
+                    },
+                    children: summary,
+                  },
+                },
+              ],
+            },
+          },
+          // Bottom: Node pills + count
+          {
+            type: "div",
+            props: {
+              style: {
+                display: "flex",
+                alignItems: "center",
+                justifyContent: "space-between",
+                gap: "16px",
+              },
+              children: [
+                {
+                  type: "div",
+                  props: {
+                    style: {
+                      display: "flex",
+                      flexWrap: "wrap",
+                      gap: "8px",
+                      flex: 1,
+                    },
+                    children: [
+                      ...displayNodes.map((name) => ({
+                        type: "div",
+                        props: {
+                          style: {
+                            fontSize: "14px",
+                            color: "#a3a3a3",
+                            backgroundColor: "#1c1c1e",
+                            padding: "4px 12px",
+                            borderRadius: "6px",
+                            border: "1px solid #262626",
+                          },
+                          children: name,
+                        },
+                      })),
+                      ...(extra > 0
+                        ? [
+                            {
+                              type: "div",
+                              props: {
+                                style: {
+                                  fontSize: "14px",
+                                  color: "#666",
+                                  padding: "4px 8px",
+                                },
+                                children: `+${extra} more`,
+                              },
+                            },
+                          ]
+                        : []),
+                    ],
+                  },
+                },
+                {
+                  type: "div",
+                  props: {
+                    style: {
+                      fontSize: "16px",
+                      color: "#666",
+                      flexShrink: 0,
+                    },
+                    children: `${nodeCount} node${nodeCount !== 1 ? "s" : ""}`,
+                  },
+                },
+              ],
+            },
+          },
+        ],
+      },
+    },
+    {
+      width: 1200,
+      height: 630,
+      fonts: [
+        { name: "Inter", data: interRegular, weight: 400, style: "normal" as const },
+        { name: "Inter", data: interBold, weight: 700, style: "normal" as const },
+      ],
+    },
+  );
+
+  const resvg = new Resvg(svg, {
+    fitTo: { mode: "width", value: 1200 },
+  });
+  const png = Buffer.from(resvg.render().asPng());
+
+  cache.set(id, png);
+  return png;
+}

src/template.ts

···
   shareServerUrl?: string;
   diagramId?: string;
   existingShareUrl?: string;
+  baseUrl?: string;
 }
 
 export function generateViewerHTML(diagram: WalkthroughDiagram, gitHash: string = "dev", projectRoot: string = "", options: ViewerOptions = {}): string {
   const diagramJSON = JSON.stringify(diagram).replace(/<\//g, "<\\/");
-  const { mode = "local", shareServerUrl = "", diagramId = "", existingShareUrl = "" } = options;
+  const { mode = "local", shareServerUrl = "", diagramId = "", existingShareUrl = "", baseUrl = "" } = options;
 
   return `<!DOCTYPE html>
 <html lang="en">
···
   <meta charset="UTF-8" />
   <meta name="viewport" content="width=device-width, initial-scale=1.0" />
   <title>Traverse — ${escapeHTML(diagram.summary)}</title>
-  <link rel="icon" href="/icon.svg" type="image/svg+xml" />
+  <link rel="icon" href="/icon.svg" type="image/svg+xml" />${baseUrl && diagramId ? `
+  <meta property="og:type" content="website" />
+  <meta property="og:title" content="${escapeHTML(diagram.summary)}" />
+  <meta property="og:description" content="Interactive code walkthrough with ${Object.keys(diagram.nodes).length} nodes" />
+  <meta property="og:image" content="${escapeHTML(baseUrl)}/diagram/${escapeHTML(diagramId)}/og.png" />
+  <meta name="twitter:card" content="summary_large_image" />
+  <meta name="twitter:title" content="${escapeHTML(diagram.summary)}" />
+  <meta name="twitter:image" content="${escapeHTML(baseUrl)}/diagram/${escapeHTML(diagramId)}/og.png" />` : ""}
   <link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/highlight.js@11/styles/github-dark.min.css" id="hljs-dark" disabled />
   <link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/highlight.js@11/styles/github.min.css" id="hljs-light" />
   <script src="https://cdn.jsdelivr.net/gh/highlightjs/cdn-release@11/build/highlight.min.js"></script>