diff --git a/.github/workflows/docs-style.yml b/.github/workflows/docs-style.yml
new file mode 100644
index 00000000..fc0d5bee
--- /dev/null
+++ b/.github/workflows/docs-style.yml
@@ -0,0 +1,62 @@
+name: Docs style
+
+on:
+  pull_request:
+    paths:
+      - '**/*.mdx'
+      - '.vale.ini'
+      - 'styles/**'
+      - 'scripts/lint-docs.py'
+  workflow_dispatch:
+    inputs:
+      scope:
+        description: 'Files to lint'
+        type: choice
+        default: changed
+        options: [changed, all]
+
+env:
+  VALE_VERSION: 3.9.6
+
+jobs:
+  style:
+    name: STYLE.md
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          fetch-depth: 0
+
+      # Pages written before the linter existed still contain violations, so a
+      # pull request is judged only on the files it touches. Run the workflow
+      # manually with scope=all to see the full backlog.
+      - name: Collect files to lint
+        id: files
+        run: |
+          if [ "${{ github.event_name }}" = "pull_request" ] && [ "${{ inputs.scope }}" != "all" ]; then
+            git diff --name-only --diff-filter=d \
+              "origin/${{ github.base_ref }}...HEAD" -- '*.mdx' > files.txt
+          else
+            git ls-files '*.mdx' > files.txt
+          fi
+          count=$(wc -l < files.txt | tr -d ' ')
+          echo "count=$count" >> "$GITHUB_OUTPUT"
+          echo "Linting $count file(s):"
+          cat files.txt
+
+      - name: Install Vale
+        if: steps.files.outputs.count != '0'
+        run: |
+          curl -sSL "https://github.com/errata-ai/vale/releases/download/v${VALE_VERSION}/vale_${VALE_VERSION}_Linux_64-bit.tar.gz" \
+            | tar -xz -C /usr/local/bin vale
+          vale --version
+
+      # Frontmatter, heading hierarchy, code fences, link paths, alt text.
+      - name: Structure
+        if: steps.files.outputs.count != '0'
+        run: xargs -a files.txt python3 scripts/lint-docs.py
+
+      # Voice, terminology, punctuation. Errors fail the job, warnings do not.
+      - name: Prose
+        if: always() && steps.files.outputs.count != '0'
+        run: xargs -a files.txt vale
diff --git a/.vale.ini b/.vale.ini
new file mode 100644
index 00000000..25388ceb
--- /dev/null
+++ b/.vale.ini
@@ -0,0 +1,16 @@
+StylesPath = styles
+MinAlertLevel = suggestion
+
+Vocab = Fhenix
+
+[formats]
+mdx = md
+
+# Only documentation pages are linted. STYLE.md and README.md are exempt:
+# the style guide quotes the words it bans.
+[*.mdx]
+BasedOnStyles = Fhenix
+
+# Frontmatter, JSX props, and fenced code blocks are not prose.
+TokenIgnores = (\{[^}]*\})
+BlockIgnores = (?s) *```.*?```, (?s)^---\n.*?\n---
diff --git a/scripts/lint-docs.py b/scripts/lint-docs.py
new file mode 100755
index 00000000..f2588bad
--- /dev/null
+++ b/scripts/lint-docs.py
@@ -0,0 +1,113 @@
+#!/usr/bin/env python3
+"""Structural checks for Mintlify MDX pages.
+
+Vale covers prose. This script covers the things Vale cannot see: frontmatter,
+heading hierarchy, code fences, link paths, and alt text. It is fence-aware, so
+nothing inside a code block is treated as prose or markup.
+
+Usage:
+    python3 scripts/lint-docs.py [files...]     # defaults to every .mdx in the repo
+
+Exits 1 if any error is found. See STYLE.md.
+"""
+
+import re
+import sys
+from pathlib import Path
+
+GUIDE = "STYLE.md"
+
+
+def parse(path: Path):
+    text = path.read_text(encoding="utf-8")
+    lines = text.splitlines()
+    front, body_start = {}, 0
+    if lines and lines[0].strip() == "---":
+        for i in range(1, len(lines)):
+            if lines[i].strip() == "---":
+                body_start = i + 1
+                break
+            m = re.match(r'\s*([A-Za-z0-9_-]+)\s*:\s*(.*)', lines[i])
+            if m:
+                front[m.group(1)] = m.group(2).strip().strip('"\'')
+    return lines, front, body_start
+
+
+def check(path: Path):
+    lines, front, body_start = parse(path)
+    errors = []
+
+    def err(line_no, rule, message):
+        errors.append((path, line_no, rule, message))
+
+    # Snippets are fragments included into pages, so they carry no frontmatter.
+    is_snippet = "snippets" in path.parts
+    if not is_snippet:
+        if not front.get("title"):
+            err(1, "frontmatter", "Missing frontmatter `title`.")
+        if not front.get("description"):
+            err(1, "frontmatter", "Missing frontmatter `description`. One sentence saying what the page covers.")
+
+    in_fence, fence_marker, fence_line = False, "", 0
+    last_level = 1  # the H1 Mintlify renders from the frontmatter title
+
+    for i in range(body_start, len(lines)):
+        line = lines[i]
+        n = i + 1
+        stripped = line.strip()
+
+        fence = re.match(r'^(```+|~~~+)(.*)$', stripped)
+        if fence:
+            marker, info = fence.group(1), fence.group(2).strip()
+            if not in_fence:
+                in_fence, fence_marker, fence_line = True, marker[:3], n
+                if not info:
+                    err(n, "code-lang", "Code block has no language tag. Add one, plus a filename where the reader needs to know where the code goes.")
+            elif marker.startswith(fence_marker):
+                in_fence = False
+            continue
+        if in_fence:
+            continue
+
+        heading = re.match(r'^(#{1,6})\s+(\S.*)$', line)
+        if heading:
+            level, title = len(heading.group(1)), heading.group(2)
+            if level == 1:
+                err(n, "manual-h1", "Manual H1. Mintlify renders the page H1 from the frontmatter `title`. Body headings start at `##`.")
+            elif level > last_level + 1:
+                err(n, "heading-skip", f"Heading level jumps from h{last_level} to h{level}. Do not skip levels.")
+            last_level = max(level, 2) if level > 1 else last_level
+            continue
+
+        for match in re.finditer(r'\]\((\.\.?/[^)\s]*)\)', line):
+            err(n, "link-path", f"Relative link `{match.group(1)}`. Use a root-relative path, such as `/fhe-library/core-concepts/access-control`.")
+        for match in re.finditer(r'\]\((https?://(?:cofhe-)?docs\.fhenix\.zone[^)\s]*)\)', line):
+            err(n, "link-path", f"Absolute link to our own site `{match.group(1)}`. Use a root-relative path so preview deployments resolve.")
+        if re.search(r'!\[\s*\]\(', line):
+            err(n, "alt-text", "Image has no alt text. Describe what the image shows.")
+        for match in re.finditer(r'<img\b[^>]*>', line):
+            if 'alt=' not in match.group(0):
+                err(n, "alt-text", "`<img>` has no `alt` attribute.")
+
+    if in_fence:
+        err(fence_line, "code-fence", "Code block is never closed.")
+
+    return errors
+
+
+def main(argv):
+    paths = [Path(a) for a in argv[1:]] or sorted(Path(".").rglob("*.mdx"))
+    paths = [p for p in paths if p.suffix == ".mdx" and p.exists()]
+    errors = []
+    for path in paths:
+        errors.extend(check(path))
+
+    for path, line_no, rule, message in errors:
+        print(f"{path}:{line_no}: error [{rule}] {message}")
+
+    print(f"\n{len(errors)} error(s) in {len(paths)} file(s). See {GUIDE}.", file=sys.stderr)
+    return 1 if errors else 0
+
+
+if __name__ == "__main__":
+    sys.exit(main(sys.argv))
diff --git a/styles/Fhenix/Condescending.yml b/styles/Fhenix/Condescending.yml
new file mode 100644
index 00000000..0f6fe3c2
--- /dev/null
+++ b/styles/Fhenix/Condescending.yml
@@ -0,0 +1,15 @@
+extends: existence
+message: "Avoid '%s'. If the reader is stuck, the word is an insult; if not, it is noise."
+link: https://github.com/FhenixProtocol/fhenix-developer-docs/blob/main/STYLE.md#words
+level: warning
+ignorecase: true
+tokens:
+  - 'simply'
+  - 'simple'
+  - 'just'
+  - 'easy'
+  - 'easily'
+  - 'obviously'
+  - 'of course'
+  - 'trivial(ly)?'
+  - 'straightforward'
diff --git a/styles/Fhenix/DecorativeUnicode.yml b/styles/Fhenix/DecorativeUnicode.yml
new file mode 100644
index 00000000..3f8bf4d9
--- /dev/null
+++ b/styles/Fhenix/DecorativeUnicode.yml
@@ -0,0 +1,17 @@
+extends: existence
+message: "No decorative Unicode ('%s'). Use words: 'Shipped', 'In progress', 'Planned'."
+link: https://github.com/FhenixProtocol/fhenix-developer-docs/blob/main/STYLE.md#punctuation-and-symbols
+level: error
+nonword: true
+tokens:
+  - '→'
+  - '←'
+  - '⇒'
+  - '✅'
+  - '❌'
+  - '✔'
+  - '✖'
+  - '✨'
+  - '🚀'
+  - '🎉'
+  - '🔥'
diff --git a/styles/Fhenix/EmDash.yml b/styles/Fhenix/EmDash.yml
new file mode 100644
index 00000000..edbd126c
--- /dev/null
+++ b/styles/Fhenix/EmDash.yml
@@ -0,0 +1,8 @@
+extends: existence
+message: "No em dashes. Rewrite with a comma, a period, a colon, or parentheses."
+link: https://github.com/FhenixProtocol/fhenix-developer-docs/blob/main/STYLE.md#punctuation-and-symbols
+level: error
+nonword: true
+tokens:
+  - '—'
+  - ' -- '
diff --git a/styles/Fhenix/Exclamation.yml b/styles/Fhenix/Exclamation.yml
new file mode 100644
index 00000000..44e63693
--- /dev/null
+++ b/styles/Fhenix/Exclamation.yml
@@ -0,0 +1,7 @@
+extends: existence
+message: "Exclamation mark. At most one per tab, preferably zero."
+link: https://github.com/FhenixProtocol/fhenix-developer-docs/blob/main/STYLE.md#punctuation-and-symbols
+level: warning
+nonword: true
+tokens:
+  - '\w!(\s|$)'
diff --git a/styles/Fhenix/Filler.yml b/styles/Fhenix/Filler.yml
new file mode 100644
index 00000000..4e2f676e
--- /dev/null
+++ b/styles/Fhenix/Filler.yml
@@ -0,0 +1,15 @@
+extends: existence
+message: "Filler phrase: '%s'. Cut it or say the thing directly."
+link: https://github.com/FhenixProtocol/fhenix-developer-docs/blob/main/STYLE.md#words
+level: error
+ignorecase: true
+tokens:
+  - 'in order to'
+  - 'it is important to note that'
+  - "it's important to note that"
+  - 'it is worth noting that'
+  - "it's worth noting that"
+  - 'please note that'
+  - 'needless to say'
+  - 'as you can see'
+  - 'basically'
diff --git a/styles/Fhenix/FutureTense.yml b/styles/Fhenix/FutureTense.yml
new file mode 100644
index 00000000..ad38525a
--- /dev/null
+++ b/styles/Fhenix/FutureTense.yml
@@ -0,0 +1,7 @@
+extends: existence
+message: "Present tense for how the system works: '%s'. Planned behavior belongs on the future plans page, labeled as planned."
+link: https://github.com/FhenixProtocol/fhenix-developer-docs/blob/main/STYLE.md#voice
+level: suggestion
+ignorecase: true
+tokens:
+  - 'will (be able to )?(send|return|compute|verify|decrypt|encrypt|queue|store|emit|call|allow)'
diff --git a/styles/Fhenix/Headings.yml b/styles/Fhenix/Headings.yml
new file mode 100644
index 00000000..d3222cc1
--- /dev/null
+++ b/styles/Fhenix/Headings.yml
@@ -0,0 +1,36 @@
+extends: capitalization
+message: "Headings use sentence case: '%s'."
+link: https://github.com/FhenixProtocol/fhenix-developer-docs/blob/main/STYLE.md#page-structure
+level: warning
+scope: heading
+match: $sentence
+indicators:
+  - ':'
+exceptions:
+  - CoFHE
+  - FHE
+  - FheOS
+  - Teecryptor
+  - SDK
+  - API
+  - ACL
+  - TEE
+  - ZK
+  - MPC
+  - EVM
+  - ERC
+  - ERC20
+  - FHERC20
+  - Solidity
+  - Hardhat
+  - Foundry
+  - Fhenix
+  - TaskManager
+  - CommitmentRegistry
+  - Threshold Network
+  - JavaScript
+  - TypeScript
+  - React
+  - Node
+  - GitHub
+  - I
diff --git a/styles/Fhenix/Idioms.yml b/styles/Fhenix/Idioms.yml
new file mode 100644
index 00000000..2d751b6a
--- /dev/null
+++ b/styles/Fhenix/Idioms.yml
@@ -0,0 +1,14 @@
+extends: existence
+message: "Idiom: '%s'. Say what happens instead. Idioms cost non-native readers a lookup."
+link: https://github.com/FhenixProtocol/fhenix-developer-docs/blob/main/STYLE.md#words
+level: warning
+ignorecase: true
+tokens:
+  - 'out of the box'
+  - 'under the hood'
+  - 'a piece of cake'
+  - 'in a nutshell'
+  - 'the sky is the limit'
+  - 'hit the ground running'
+  - 'low-hanging fruit'
+  - 'bread and butter'
diff --git a/styles/Fhenix/InternalNames.yml b/styles/Fhenix/InternalNames.yml
new file mode 100644
index 00000000..9705ac73
--- /dev/null
+++ b/styles/Fhenix/InternalNames.yml
@@ -0,0 +1,11 @@
+extends: existence
+message: "Possible internal name: '%s'. Internal hosts, projects, environments, and flags do not belong in public docs."
+link: https://github.com/FhenixProtocol/fhenix-developer-docs/blob/main/STYLE.md#terminology
+level: warning
+ignorecase: true
+tokens:
+  - 'rehearsal'
+  - 'staging'
+  - 'aggregator'
+  - '[a-z0-9-]+\.internal'
+  - 'gcp project'
diff --git a/styles/Fhenix/LinkText.yml b/styles/Fhenix/LinkText.yml
new file mode 100644
index 00000000..f9cbad8d
--- /dev/null
+++ b/styles/Fhenix/LinkText.yml
@@ -0,0 +1,8 @@
+extends: existence
+message: "Vague link text: '%s'. Describe the destination."
+link: https://github.com/FhenixProtocol/fhenix-developer-docs/blob/main/STYLE.md#links-images-and-components
+level: warning
+scope: raw
+ignorecase: true
+raw:
+  - '\[(click here|here|this link|this page|read more|learn more|link)\]\('
diff --git a/styles/Fhenix/Marketing.yml b/styles/Fhenix/Marketing.yml
new file mode 100644
index 00000000..c10a2364
--- /dev/null
+++ b/styles/Fhenix/Marketing.yml
@@ -0,0 +1,18 @@
+extends: existence
+message: "Marketing adjective: '%s'. Describe the actual behavior instead."
+link: https://github.com/FhenixProtocol/fhenix-developer-docs/blob/main/STYLE.md#words
+level: error
+ignorecase: true
+tokens:
+  - 'seamless(ly)?'
+  - 'blazing(ly)?'
+  - 'cutting-edge'
+  - 'state-of-the-art'
+  - 'best-in-class'
+  - 'game-chang(ing|er)'
+  - 'revolutionary'
+  - 'effortless(ly)?'
+  - 'lightning[- ]fast'
+  - 'world-class'
+  - 'robust'
+  - 'powerful'
diff --git a/styles/Fhenix/SentenceLength.yml b/styles/Fhenix/SentenceLength.yml
new file mode 100644
index 00000000..a4cf1968
--- /dev/null
+++ b/styles/Fhenix/SentenceLength.yml
@@ -0,0 +1,8 @@
+extends: occurrence
+message: "Sentence is over 30 words. Aim for under 25. Split it."
+link: https://github.com/FhenixProtocol/fhenix-developer-docs/blob/main/STYLE.md#sentences-and-paragraphs
+level: warning
+scope: sentence
+ignorecase: false
+max: 30
+token: '\b(\w+)\b'
diff --git a/styles/Fhenix/SmartQuotes.yml b/styles/Fhenix/SmartQuotes.yml
new file mode 100644
index 00000000..1fa00a49
--- /dev/null
+++ b/styles/Fhenix/SmartQuotes.yml
@@ -0,0 +1,10 @@
+extends: existence
+message: "Use straight quotes and apostrophes, not '%s'."
+link: https://github.com/FhenixProtocol/fhenix-developer-docs/blob/main/STYLE.md#punctuation-and-symbols
+level: warning
+nonword: true
+tokens:
+  - '“'
+  - '”'
+  - '‘'
+  - '’'
diff --git a/styles/Fhenix/Terms.yml b/styles/Fhenix/Terms.yml
new file mode 100644
index 00000000..9b1b3537
--- /dev/null
+++ b/styles/Fhenix/Terms.yml
@@ -0,0 +1,21 @@
+extends: substitution
+message: "Use '%s', not '%s'."
+link: https://github.com/FhenixProtocol/fhenix-developer-docs/blob/main/STYLE.md#terminology
+level: error
+ignorecase: false
+swap:
+  '\bCOFHE\b': CoFHE
+  '\bCofhe\b': CoFHE
+  '\bCoFhe\b': CoFHE
+  '\bFHEOS\b': FheOS
+  '\bFheos\b': FheOS
+  '\bTeeCryptor\b': Teecryptor
+  '\bTEECryptor\b': Teecryptor
+  '(?i)\bon-chain\b': onchain
+  '(?i)\boff-chain\b': offchain
+  '(?i)\bcipher text\b': ciphertext
+  '(?i)\bplain text\b': plaintext
+  '(?i)\btest ?net\b(?<!testnet)': testnet
+  '\bTestnet\b': testnet
+  '\bMainnet\b': mainnet
+  '\bsmart-contract\b': smart contract
diff --git a/styles/config/vocabularies/Fhenix/accept.txt b/styles/config/vocabularies/Fhenix/accept.txt
new file mode 100644
index 00000000..80ed26a5
--- /dev/null
+++ b/styles/config/vocabularies/Fhenix/accept.txt
@@ -0,0 +1,17 @@
+CoFHE
+FheOS
+Teecryptor
+FHE
+FHEnix
+Fhenix
+ciphertext
+ciphertexts
+plaintext
+plaintexts
+onchain
+offchain
+testnet
+mainnet
+Solidity
+Hardhat
+Foundry