diff --git a/.changeset/mermaid-v12-redux-themes.md b/.changeset/mermaid-v12-redux-themes.md
new file mode 100644
index 000000000..5bc818c2f
--- /dev/null
+++ b/.changeset/mermaid-v12-redux-themes.md
@@ -0,0 +1,9 @@
+---
+"@alauda/doom": minor
+---
+
+Upgrade Mermaid to v12.2.0 and switch the site defaults to `redux-color` / `redux-dark-color`.
+
+Mermaid 12 makes `redux-color` and the `neo` look the default for many diagram types, and lays those types out with ELK. Doom used to force `theme: default` in light mode and `theme: dark` in dark mode, which would have kept the old palette after the upgrade. Light mode now names `redux-color`; dark mode names `redux-dark-color`, because Mermaid does not pick that palette from `dark` on its own.
+
+Diagrams that do not set `theme`, `look`, or `layout` in front matter will look different.
diff --git a/packages/doom/package.json b/packages/doom/package.json
index 9ca026fca..d3620b771 100644
--- a/packages/doom/package.json
+++ b/packages/doom/package.json
@@ -81,7 +81,7 @@
     "mdast-util-phrasing": "^4.1.0",
     "mdast-util-to-markdown": "^2.1.2",
     "mdast-util-to-string": "^4.0.0",
-    "mermaid": "^11.15.0",
+    "mermaid": "^12.2.0",
     "openai": "^6.38.0",
     "openapi-types": "^12.1.3",
     "p-ratelimit": "^1.0.1",
diff --git a/packages/doom/src/runtime/components/Mermaid.tsx b/packages/doom/src/runtime/components/Mermaid.tsx
index 2f2b13bb2..2ed584d52 100644
--- a/packages/doom/src/runtime/components/Mermaid.tsx
+++ b/packages/doom/src/runtime/components/Mermaid.tsx
@@ -18,7 +18,8 @@ export const Mermaid = ({ className, children }: MermaidProps) => {
   useEffect(() => {
     const container = containerRef.current!
 
-    mermaid.initialize({ theme: isDark ? 'dark' : 'default' })
+    // Dark has to be named; `theme: dark` would keep the old palette.
+    mermaid.initialize({ theme: isDark ? 'redux-dark-color' : 'redux-color' })
 
     const render = async () => {
       const { svg, diagramType, bindFunctions } = await mermaid.render(
diff --git a/yarn.lock b/yarn.lock
index ea11d8bd1..2d08390f0 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -68,7 +68,7 @@ __metadata:
     mdast-util-phrasing: "npm:^4.1.0"
     mdast-util-to-markdown: "npm:^2.1.2"
     mdast-util-to-string: "npm:^4.0.0"
-    mermaid: "npm:^11.15.0"
+    mermaid: "npm:^12.2.0"
     openai: "npm:^6.38.0"
     openapi-types: "npm:^12.1.3"
     p-ratelimit: "npm:^1.0.1"
@@ -696,7 +696,7 @@ __metadata:
   languageName: node
   linkType: hard
 
-"@braintree/sanitize-url@npm:^7.1.1":
+"@braintree/sanitize-url@npm:^7.1.2":
   version: 7.1.2
   resolution: "@braintree/sanitize-url@npm:7.1.2"
   checksum: 10c0/62f2aa0cf58626e3880b2dc1025c42064b4639abd157ae4e1c35f4c2f5031e9273772046a423979845069c814e27ff818e8e669280dc53585e6f033d5b7a59cb
@@ -964,10 +964,43 @@ __metadata:
   languageName: node
   linkType: hard
 
-"@chevrotain/types@npm:~11.1.1":
-  version: 11.1.2
-  resolution: "@chevrotain/types@npm:11.1.2"
-  checksum: 10c0/c0c4679a3d407df34e18d5adfa7ac599b4a2bfddbf68da6e43678b9b3e16ab911de7766b37b9fc466261c3dead3db1b620e2e344f800fa9f0f381720475eda8f
+"@chevrotain/cst-dts-gen@npm:13.2.0":
+  version: 13.2.0
+  resolution: "@chevrotain/cst-dts-gen@npm:13.2.0"
+  dependencies:
+    "@chevrotain/gast": "npm:13.2.0"
+    "@chevrotain/types": "npm:13.2.0"
+  checksum: 10c0/844c3bbed4b55e428597dca6e33d34073971c2a0d28a1e804995a89581d2de598d9823a44b6b45651aa8364fe46495fbe31074a319b99fb53123870b898c8718
+  languageName: node
+  linkType: hard
+
+"@chevrotain/gast@npm:13.2.0":
+  version: 13.2.0
+  resolution: "@chevrotain/gast@npm:13.2.0"
+  dependencies:
+    "@chevrotain/types": "npm:13.2.0"
+  checksum: 10c0/57b87780cb8941fa04781177fc73b40adc091b0daf822d45124bd1096f8b7b1c936013222e2f29cdb847bcb09e36586e8eb04710a8b8c9b65c91842e8bd5e703
+  languageName: node
+  linkType: hard
+
+"@chevrotain/regexp-to-ast@npm:13.2.0":
+  version: 13.2.0
+  resolution: "@chevrotain/regexp-to-ast@npm:13.2.0"
+  checksum: 10c0/ddba2885059d83b6cb56df12b6b30d96bcd8c90f1b43f541d8a9e9eeafcba37c7542ecf17b1a15d5a8f2ea9c969717523069bf034cf931003e91a2039c1c06e1
+  languageName: node
+  linkType: hard
+
+"@chevrotain/types@npm:13.2.0, @chevrotain/types@npm:~13.2.0":
+  version: 13.2.0
+  resolution: "@chevrotain/types@npm:13.2.0"
+  checksum: 10c0/89375750866db94ff957bc1468bad71c7522fe46f314c395d81fa748f71f80b249cb09073de4def3de81a9bc98b2c4533d634845be0400bf7710901d831ca505
+  languageName: node
+  linkType: hard
+
+"@chevrotain/utils@npm:13.2.0":
+  version: 13.2.0
+  resolution: "@chevrotain/utils@npm:13.2.0"
+  checksum: 10c0/4d87dd83f865d2a868d0eeca36f330dd397967f224505b6aaf4492703b3f385646378c4a905594a483d1b7d9651e000292253ca4e1e17c521811b23f6a06fec8
   languageName: node
   linkType: hard
 
@@ -2385,12 +2418,12 @@ __metadata:
   languageName: node
   linkType: hard
 
-"@mermaid-js/parser@npm:^1.1.1":
-  version: 1.1.1
-  resolution: "@mermaid-js/parser@npm:1.1.1"
+"@mermaid-js/parser@npm:^2.0.1":
+  version: 2.0.1
+  resolution: "@mermaid-js/parser@npm:2.0.1"
   dependencies:
-    "@chevrotain/types": "npm:~11.1.1"
-  checksum: 10c0/66414d9d66f3a86a6751427cb8890a00beaaee2b7eba34c21b34b60cdaf9237d21e9b50b9bf1f560a01a600ee332d33b949fd8f12cbda3238aba50edc0dfdf15
+    "@chevrotain/types": "npm:~13.2.0"
+  checksum: 10c0/15ef44aac5dd772d0b28b62fa97ef30440561fa9f8008267da885a73a8e2e2940af350214664f125244a1571729257c3b2e28af7c1f5e6060f4b23701a73efcc
   languageName: node
   linkType: hard
 
@@ -5350,6 +5383,19 @@ __metadata:
   languageName: node
   linkType: hard
 
+"chevrotain@npm:~13.2.0":
+  version: 13.2.0
+  resolution: "chevrotain@npm:13.2.0"
+  dependencies:
+    "@chevrotain/cst-dts-gen": "npm:13.2.0"
+    "@chevrotain/gast": "npm:13.2.0"
+    "@chevrotain/regexp-to-ast": "npm:13.2.0"
+    "@chevrotain/types": "npm:13.2.0"
+    "@chevrotain/utils": "npm:13.2.0"
+  checksum: 10c0/f7384a69c4ef7d43be6fd63a9447af5877de7b66842638d8568a85e7f404a278495d68f0fd9024f12aec886aee9b888c544734549b9c95e03f6e4c6e87fcb1cf
+  languageName: node
+  linkType: hard
+
 "chokidar@npm:^4.0.0":
   version: 4.0.3
   resolution: "chokidar@npm:4.0.3"
@@ -5515,10 +5561,10 @@ __metadata:
   languageName: node
   linkType: hard
 
-"commander@npm:^8.3.0":
-  version: 8.3.0
-  resolution: "commander@npm:8.3.0"
-  checksum: 10c0/8b043bb8322ea1c39664a1598a95e0495bfe4ca2fad0d84a92d7d1d8d213e2a155b441d2470c8e08de7c4a28cf2bc6e169211c49e1b21d9f7edc6ae4d9356060
+"commander@npm:^15.0.0":
+  version: 15.0.0
+  resolution: "commander@npm:15.0.0"
+  checksum: 10c0/539229c171914ea1ccd45ee5f10d924289a12a684ea3a7a44147abe54003c35ed6de9ae4ad198d88c29fdf403dca0428451a388234e6dc01b6faa978fb207206
   languageName: node
   linkType: hard
 
@@ -5816,10 +5862,10 @@ __metadata:
   languageName: node
   linkType: hard
 
-"cytoscape@npm:^3.33.1":
-  version: 3.33.3
-  resolution: "cytoscape@npm:3.33.3"
-  checksum: 10c0/f0d01f682d3e443cbeea9aa294ccd6934442362df3ce259e7b0fe3b9a8ce534d901840c503db8b53da814542bc1508f7f14a69e4fe725f919c25483a7200efe7
+"cytoscape@npm:^3.34.0":
+  version: 3.34.4
+  resolution: "cytoscape@npm:3.34.4"
+  checksum: 10c0/4dcd1f0a0ff61df5d3cfd4359426403e70fdc4c8d38c6c246506b3789514001c46c46cf54575455ab03736920dc09c497a40eaa20d61798f5a2bc31f7f038940
   languageName: node
   linkType: hard
 
@@ -6200,10 +6246,10 @@ __metadata:
   languageName: node
   linkType: hard
 
-"dayjs@npm:^1.11.19":
-  version: 1.11.20
-  resolution: "dayjs@npm:1.11.20"
-  checksum: 10c0/8af525e2aa100c8db9923d706c42b2b2d30579faf89456619413a5c10916efc92c2b166e193c27c02eb3174b30aa440ee1e7b72b0a2876b3da651d204db848a0
+"dayjs@npm:^1.11.21":
+  version: 1.11.23
+  resolution: "dayjs@npm:1.11.23"
+  checksum: 10c0/69ab04bf19c676e44ab50cc2fca223d265f3dafd107151ef3b0f3ad74d360c37caa602abe62f87cb25d90bd9f6bee003698af47df5b0dbf10a998b7b5f3bb3f1
   languageName: node
   linkType: hard
 
@@ -6354,15 +6400,15 @@ __metadata:
   languageName: node
   linkType: hard
 
-"dompurify@npm:^3.3.1":
-  version: 3.4.2
-  resolution: "dompurify@npm:3.4.2"
+"dompurify@npm:^3.4.12":
+  version: 3.4.17
+  resolution: "dompurify@npm:3.4.17"
   dependencies:
     "@types/trusted-types": "npm:^2.0.7"
   dependenciesMeta:
     "@types/trusted-types":
       optional: true
-  checksum: 10c0/23ab3ab079480a49e1426c4ee7279e393913fa7f2193c4142a5be54d4163dbdd969558675876c6b8bbcbf2ad5d1bc3e00bf902acf142fff12e50274a65ae95b3
+  checksum: 10c0/6a12251ef5e700fc91b6d96d33e9f8b5fd590c55276f632cf42d182c5808e9f48d5bef435ab26eac235dfcc05ed8fe95e1c8308dcc502bf1050e561f14d0361a
   languageName: node
   linkType: hard
 
@@ -6440,6 +6486,13 @@ __metadata:
   languageName: node
   linkType: hard
 
+"elkjs@npm:^0.9.3":
+  version: 0.9.3
+  resolution: "elkjs@npm:0.9.3"
+  checksum: 10c0/caf544ff4fce8442d1d3dd6dface176c9b2fe26fc1e34f56122828e6eef7d2d7fe70d3202f9f3ecf0feb6287d4c8430949f483e63e450a7454bb39ccffab3808
+  languageName: node
+  linkType: hard
+
 "emoji-regex@npm:^10.2.1":
   version: 10.6.0
   resolution: "emoji-regex@npm:10.6.0"
@@ -8403,14 +8456,14 @@ __metadata:
   languageName: node
   linkType: hard
 
-"katex@npm:^0.16.25":
-  version: 0.16.45
-  resolution: "katex@npm:0.16.45"
+"katex@npm:^0.18.0":
+  version: 0.18.10
+  resolution: "katex@npm:0.18.10"
   dependencies:
-    commander: "npm:^8.3.0"
+    commander: "npm:^15.0.0"
   bin:
     katex: cli.js
-  checksum: 10c0/f715eb9a73daff68ac14dcc8c2f47f02f5fc756a74077d22479e64e06872b2b44f0d81f1c91a98a9873722a08841388a869a0b9ddb96b224362eb8054ddf533a
+  checksum: 10c0/3864a236334e9c7aef906b2fdd70defb76edfe8362372ccd5504167e8b22bbc1a48210e5d03e30e464c0c0f669e6d467b3b8b01120598fb1968c275fa5059721
   languageName: node
   linkType: hard
 
@@ -8931,32 +8984,34 @@ __metadata:
   languageName: node
   linkType: hard
 
-"mermaid@npm:^11.15.0":
-  version: 11.15.0
-  resolution: "mermaid@npm:11.15.0"
+"mermaid@npm:^12.2.0":
+  version: 12.2.0
+  resolution: "mermaid@npm:12.2.0"
   dependencies:
-    "@braintree/sanitize-url": "npm:^7.1.1"
+    "@braintree/sanitize-url": "npm:^7.1.2"
     "@iconify/utils": "npm:^3.0.2"
-    "@mermaid-js/parser": "npm:^1.1.1"
+    "@mermaid-js/parser": "npm:^2.0.1"
     "@types/d3": "npm:^7.4.3"
     "@upsetjs/venn.js": "npm:^2.0.0"
-    cytoscape: "npm:^3.33.1"
+    chevrotain: "npm:~13.2.0"
+    cytoscape: "npm:^3.34.0"
     cytoscape-cose-bilkent: "npm:^4.1.0"
     cytoscape-fcose: "npm:^2.2.0"
     d3: "npm:^7.9.0"
     d3-sankey: "npm:^0.12.3"
     dagre-d3-es: "npm:7.0.14"
-    dayjs: "npm:^1.11.19"
-    dompurify: "npm:^3.3.1"
+    dayjs: "npm:^1.11.21"
+    dompurify: "npm:^3.4.12"
+    elkjs: "npm:^0.9.3"
     es-toolkit: "npm:^1.45.1"
-    katex: "npm:^0.16.25"
+    katex: "npm:^0.18.0"
     khroma: "npm:^2.1.0"
     marked: "npm:^16.3.0"
     roughjs: "npm:^4.6.6"
     stylis: "npm:^4.3.6"
     ts-dedent: "npm:^2.2.0"
     uuid: "npm:^11.1.0 || ^12 || ^13 || ^14.0.0"
-  checksum: 10c0/9085b47c30b66a1e94e07c93951d9e53e5c89ec8c9fff8814233bddeecf6b8eaf9036d3168e4d1360c3f5d07cd051c666da96860eb0f22f064bd749499a0c83f
+  checksum: 10c0/6b9e745667febde92ce9c01f1ee8dcd8df77b489a724a131c5340895f12d85de36fd7c52477e6cfb69aa43c2e74bd420b8adb4e9b78c430c4a7f5a5dfe8ad784
   languageName: node
   linkType: hard