diff --git a/DEPLOY_CLOUDFLARE.md b/DEPLOY_CLOUDFLARE.md
index 16df5ac..7d211c5 100644
--- a/DEPLOY_CLOUDFLARE.md
+++ b/DEPLOY_CLOUDFLARE.md
@@ -16,7 +16,7 @@ the following build configuration.
 | Build command | `bash scripts/build.sh` |
 | Build output directory | `book` |
 | Root directory | `/` |
-| Environment variable | `MDBOOK_VERSION=v0.4.40` |
+| Environment variable | `MDBOOK_VERSION=v0.5.3` |
 
 The build command downloads a pinned mdBook release into
 `.mdbook-bin/` if the binary is not already on PATH, syncs the
diff --git a/README.md b/README.md
index b7956d2..5b323a6 100644
--- a/README.md
+++ b/README.md
@@ -1,6 +1,10 @@
 # Vyrox Security
 
-# Your AI Security Copilot
+> AI security copilot for teams without a dedicated SOC. Ingests EDR alerts,
+> triages them through a deterministic heuristics engine and an LLM fallback,
+> and routes the verdicts that matter to a human approver in Discord. Every
+> containment action runs through a small Rust proxy that the customer can
+> read and audit.
 
 [![License: MIT (proxy)](https://img.shields.io/badge/proxy-MIT-green?style=flat-square)](https://github.com/vyrox-security/vyrox-proxy/blob/main/LICENSE)
 [![Status](https://img.shields.io/badge/status-alpha-orange?style=flat-square)](#status)
diff --git a/book.toml b/book.toml
index ae822b1..919f97a 100644
--- a/book.toml
+++ b/book.toml
@@ -34,7 +34,16 @@ preferred-dark-theme = "navy"
 # copy-paste. Leaving curly-quotes on for prose readability.
 smart-punctuation = false
 
-additional-css = ["theme/css/variables.css", "theme/css/typography.css"]
+# Critical: do NOT name override files after mdBook's own bundled
+# theme files (variables.css, general.css, chrome.css, print.css).
+# mdBook treats any file in `theme/css/` whose name matches a
+# bundled file as a full replacement, which wipes out the standard
+# variables like `--page-padding` and `--sidebar-resize-indicator-width`.
+# That broke the chapter-nav arrow positioning and the sidebar width
+# in the first deploy. We use `brand.css` for the palette overrides
+# instead, and add it as additional-css so it cascades on top of the
+# defaults.
+additional-css = ["theme/css/brand.css", "theme/css/typography.css"]
 additional-js = []
 
 # Edit-this-page link on every chapter. Points at the top-level file
diff --git a/scripts/build.sh b/scripts/build.sh
index 61fd10b..d59a2d6 100755
--- a/scripts/build.sh
+++ b/scripts/build.sh
@@ -59,7 +59,12 @@ done
 # Cloudflare Pages does not ship mdbook. We fetch the pinned release
 # tarball if the binary is not on PATH. Pinning the version means a
 # release-channel change on the upstream cannot break this build.
-MDBOOK_VERSION="${MDBOOK_VERSION:-v0.4.40}"
+# v0.5.3 is the release we test against locally. The CSS overrides
+# in `theme/css/` target selectors that exist in mdBook 0.5.x
+# (`#mdbook-sidebar`, `#mdbook-sidebar-toggle-anchor`, etc). v0.4.x
+# uses different chrome IDs and our overrides do not apply there,
+# which broke the sidebar layout on the first Cloudflare deploy.
+MDBOOK_VERSION="${MDBOOK_VERSION:-v0.5.3}"
 LOCAL_MDBOOK_BIN="$REPO_ROOT/.mdbook-bin/mdbook"
 
 mdbook_cmd() {
diff --git a/theme/css/variables.css b/theme/css/brand.css
similarity index 100%
rename from theme/css/variables.css
rename to theme/css/brand.css