diff --git a/CHANGELOG.md b/CHANGELOG.md
index 518a5ee..dc0e671 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -5,6 +5,32 @@ All notable changes to this project are documented here.
 Format based on [Keep a Changelog](https://keepachangelog.com/en/1.1.0/).
 This project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## Unreleased
+
+### Added
+- Usable brand assets: `assets/usable-icon.svg` (composer icon) and `assets/usable-logo.png`
+  (600×600 logo), taken from the Usable brand kit.
+- Codex interface metadata under the `extensions["com.openai"]` namespace in `plugin.json`:
+  display name, short and long descriptions, developer name, category, website, privacy and
+  terms URLs, brand colour `#347cbf`, icon and logo paths, and a default prompt.
+- Validation of client-extension file references: paths must be plugin-relative, must stay
+  inside the plugin root, and must exist. Three new self-tests cover a missing asset, a path
+  escaping the root, and a namespace without a reverse domain.
+
+### Changed
+- `assets/` is now included in the release archive allowlist.
+- `homepage` and author URL now use the canonical `https://www.usable.dev`, which is where
+  the apex domain redirects.
+
+### Notes
+- Codex surfaced the plugin with a generic icon and "Website: Unavailable" because it reads
+  presentation metadata from an `interface` object, not from the Agent Plugins `homepage`
+  field. **Whether Codex reads that object from the inline `com.openai` extension has not been
+  verified visually** — the CLI exposes no way to inspect resolved interface metadata. If the
+  icon and website still do not render, the fallback is a `.codex-plugin/plugin.json` overlay,
+  which must be added carefully because a malformed overlay could disturb skill discovery that
+  currently works.
+
 ## 0.1.0 — 2026-08-07
 
 First prerelease. No client has completed all five acceptance steps, so no client is listed
diff --git a/assets/usable-icon.svg b/assets/usable-icon.svg
new file mode 100644
index 0000000..034e35c
--- /dev/null
+++ b/assets/usable-icon.svg
@@ -0,0 +1 @@
+<svg id="eovtPqbMRQL1" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" viewBox="0 0 600 600" shape-rendering="geometricPrecision" text-rendering="geometricPrecision" project-id="ebd8607c8db943838c4b888f52a231f3" export-id="f8a8bc640e7b4691ad0ee39c01c6fee0" cached="false"><g transform="matrix(.95 0 0 0.95 14.999983 24.236537)"><path d="M62.69957,440.29028c0-23.81311,7.89513-45.78225,21.21062-63.4327-.11008-2.30378-.16563-4.61894-.16563-6.94465c0-97.09471,96.82086-175.80552,216.25544-175.80552s216.25544,78.71081,216.25544,175.80552c0,2.32571-.05555,4.64087-.16563,6.94465c13.3155,17.65045,21.21062,39.61959,21.21062,63.4327c0,36.66029-18.71193,68.95025-47.10612,87.84038C453.58571,556.57834,382.14098,575.89262,300,575.89262s-153.58571-19.31428-190.19431-47.76196c-28.3942-18.89013-47.10612-51.18009-47.10612-87.84038Z" fill="#f4f3f3" stroke-width="20"/><path d="M230.471671,440.512555c0,0,12.92452,25.898716,69.528311,25.898716s69.528312-25.898716,69.528312-25.898716" transform="translate(.000001 20.835594)" fill="none" stroke="#1c2f40" stroke-width="20" stroke-linecap="round" stroke-linejoin="round"/><ellipse rx="33.011804" ry="42.45283" transform="translate(409.589983 371.91582)" fill="#1c2f40" stroke-width="0"/><ellipse rx="11.135856" ry="14.320596" transform="translate(401.206686 352.302714)" fill="#f4f3f3" stroke-width="0"/><ellipse rx="33.011804" ry="42.45283" transform="matrix(-1 0 0 1 190.409983 371.91582)" fill="#1c2f40" stroke-width="0"/><ellipse rx="11.135856" ry="14.320596" transform="matrix(-1 0 0 1 198.79335 352.302714)" fill="#f4f3f3" stroke-width="0"/><g transform="matrix(.996195-.087156 0.087156 0.996195-17.563735 23.662101)"><path d="M46.967163,-9.782072c0,43.297565-6.74235,81.953045-17.300908,107.340745-.093172,1.122544-4.26088,16.609842-30.53494,16.500041s-26.716246-12.464125-27.215225-12.857818C-39.546539,75.955318,-46.967163,35.64116,-46.967163,-9.782072c0-76.463807,21.027915-138.449969,46.967163-138.449969s46.967163,61.986162,46.967163,138.449969Z" transform="matrix(.865577 0.500775-.500775 0.865577 479.759578 166.79753)" fill="#347cbf" stroke-width="20"/><path d="M525.31191,181.85039c-10.21046,17.64852-21.1996,33.65726-32.25184,47.39956-14.2538-2.02797-28.91911-6.99001-42.86119-15.03947-12.58617-7.26663-23.28802-16.30173-31.78586-26.32593c6.47364-16.86039,15.07214-34.89175,25.59148-53.07415c14.59016-25.21871,30.77028-47.0892,46.4525-63.78304c11.60357,2.55438,23.33301,7.04107,34.5909,13.54082c12.68752,7.32514,23.46026,16.44736,31.99072,26.56829-6.68899,21.58739-17.43511,46.01127-31.72671,70.71393v-.00001Z" fill="#fcaf2a" stroke-width="20"/></g><g transform="matrix(-.996195-.087156-.087156 0.996195 617.563769 23.662096)"><path d="M46.967163,-9.782072c0,43.297565-6.74235,81.953045-17.300908,107.340745-.093172,1.122544-4.26088,16.609842-30.53494,16.500041s-26.716246-12.464125-27.215225-12.857818C-39.546539,75.955318,-46.967163,35.64116,-46.967163,-9.782072c0-76.463807,21.027915-138.449969,46.967163-138.449969s46.967163,61.986162,46.967163,138.449969Z" transform="matrix(.865577 0.500775-.500775 0.865577 479.759578 166.79753)" fill="#347cbf" stroke-width="20"/><path d="M525.31191,181.85039c-10.21046,17.64852-21.1996,33.65726-32.25184,47.39956-14.2538-2.02797-28.91911-6.99001-42.86119-15.03947-12.58617-7.26663-23.28802-16.30173-31.78586-26.32593c6.47364-16.86039,15.07214-34.89175,25.59148-53.07415c14.59016-25.21871,30.77028-47.0892,46.4525-63.78304c11.60357,2.55438,23.33301,7.04107,34.5909,13.54082c12.68752,7.32514,23.46026,16.44736,31.99072,26.56829-6.68899,21.58739-17.43511,46.01127-31.72671,70.71393v-.00001Z" fill="#fcaf2a" stroke-width="20"/></g></g></svg>
diff --git a/assets/usable-logo.png b/assets/usable-logo.png
new file mode 100644
index 0000000..629384c
Binary files /dev/null and b/assets/usable-logo.png differ
diff --git a/docs/permissions-and-data-flow.md b/docs/permissions-and-data-flow.md
index 9e5e34e..160d536 100644
--- a/docs/permissions-and-data-flow.md
+++ b/docs/permissions-and-data-flow.md
@@ -10,9 +10,13 @@ Intended for security reviewers deciding whether to allow this plugin in an orga
 | Runtime dependencies | None. |
 | Instruction text | `skills/**/*.md` — plain Markdown, fully auditable. |
 | Network configuration | One remote MCP server declaration in `mcp.json`. |
+| Static images | `assets/usable-icon.svg` and `assets/usable-logo.png` — branding only, no scripts. |
 | Credentials | None. |
 | Local filesystem access | None requested by the plugin itself. |
 
+The SVG contains only path geometry. It declares no `<script>`, no external references, and
+no event handlers, so it cannot execute anything when a client renders it.
+
 The repository contains Node scripts under `scripts/` for validation and release builds.
 These run in CI and for local development only, and are excluded from the release archive.
 
diff --git a/plugin.json b/plugin.json
index 60e065b..1e4832a 100644
--- a/plugin.json
+++ b/plugin.json
@@ -8,7 +8,7 @@
     "email": "support@usable.dev",
     "url": "https://usable.dev"
   },
-  "homepage": "https://usable.dev",
+  "homepage": "https://www.usable.dev",
   "repository": "https://github.com/flowcore-io/usable-agent-plugin",
   "license": "MIT",
   "keywords": [
@@ -19,5 +19,27 @@
     "agent-skills",
     "retrieval",
     "verification"
-  ]
+  ],
+  "extensions": {
+    "com.openai": {
+      "interface": {
+        "displayName": "Usable",
+        "shortDescription": "Search your team's knowledge before you build.",
+        "longDescription": "Grounds the agent in decisions your team already made. It searches Usable before proposing an approach, retrieves complete sources rather than snippets, separates evidence from assumptions, and verifies before claiming success. Verified outcomes can be captured back so the next person does not rediscover them.",
+        "developerName": "Flowcore",
+        "category": "Productivity",
+        "websiteURL": "https://www.usable.dev",
+        "privacyPolicyURL": "https://www.usable.dev/privacy",
+        "termsOfServiceURL": "https://www.usable.dev/terms",
+        "brandColor": "#347cbf",
+        "composerIcon": "./assets/usable-icon.svg",
+        "logo": "./assets/usable-logo.png",
+        "defaultPrompt": [
+          "Search Usable for prior decisions about this task before proposing an approach"
+        ],
+        "capabilities": [],
+        "screenshots": []
+      }
+    }
+  }
 }
diff --git a/scripts/build-release.mjs b/scripts/build-release.mjs
index 70031fb..6365311 100644
--- a/scripts/build-release.mjs
+++ b/scripts/build-release.mjs
@@ -27,6 +27,7 @@ const ALLOWLIST = [
   "plugin.json",
   "mcp.json",
   "skills/",
+  "assets/",
   "docs/",
   "README.md",
   "LICENSE",
diff --git a/scripts/validate-package.mjs b/scripts/validate-package.mjs
index 1598f88..e143dbb 100644
--- a/scripts/validate-package.mjs
+++ b/scripts/validate-package.mjs
@@ -40,6 +40,25 @@ const pass = (msg) => passes.push(msg);
 const read = (p) => readFileSync(join(ROOT, p), "utf8");
 const readJson = (p) => JSON.parse(read(p));
 
+/**
+ * Collects every string in a nested structure that looks like a plugin-relative
+ * path, so extension-declared assets can be checked for existence.
+ */
+function collectPluginRelativePaths(node, acc = []) {
+  if (typeof node === "string") {
+    if (node.startsWith("./") || /^\.\.?\//.test(node)) acc.push(node);
+    return acc;
+  }
+  if (Array.isArray(node)) {
+    for (const item of node) collectPluginRelativePaths(item, acc);
+    return acc;
+  }
+  if (node && typeof node === "object") {
+    for (const value of Object.values(node)) collectPluginRelativePaths(value, acc);
+  }
+  return acc;
+}
+
 /** Recursively walk the repo, skipping VCS and ignored build dirs. */
 function walk(dir, acc = []) {
   const SKIP = new Set([".git", "node_modules", "dist"]);
@@ -102,6 +121,24 @@ function validateManifest() {
         fail(CHECK, `extension key "${key}" must use a reverse-domain namespace`);
       }
     }
+
+    // Client extensions may reference packaged files (icons, logos). A broken
+    // reference ships a plugin that renders without branding, which is exactly
+    // the sort of defect that is invisible until a user sees it.
+    for (const [ns, value] of Object.entries(m.extensions)) {
+      for (const path of collectPluginRelativePaths(value)) {
+        if (!path.startsWith("./")) {
+          fail(CHECK, `extension "${ns}" path ${JSON.stringify(path)} must be plugin-relative and begin with "./"`);
+          continue;
+        }
+        const resolved = resolve(ROOT, path);
+        if (!resolved.startsWith(ROOT + sep)) {
+          fail(CHECK, `extension "${ns}" path ${JSON.stringify(path)} escapes the plugin root`);
+        } else if (!existsSync(resolved)) {
+          fail(CHECK, `extension "${ns}" references missing file ${path}`);
+        }
+      }
+    }
   }
 
   if (errors.every((e) => !e.startsWith(CHECK))) pass(`${CHECK} conforms to Agent Plugins 1.0.0`);
diff --git a/tests/smoke/validator.test.mjs b/tests/smoke/validator.test.mjs
index 0e4a8f9..e334f32 100644
--- a/tests/smoke/validator.test.mjs
+++ b/tests/smoke/validator.test.mjs
@@ -36,7 +36,7 @@ function runValidator(dir) {
 function inSandbox(mutate) {
   const dir = mkdtempSync(join(tmpdir(), "uap-test-"));
   try {
-    for (const entry of ["plugin.json", "mcp.json", "skills", "docs", "scripts", "LICENSE"]) {
+    for (const entry of ["plugin.json", "mcp.json", "skills", "assets", "docs", "scripts", "LICENSE"]) {
       cpSync(join(ROOT, entry), join(dir, entry), { recursive: true });
     }
     mutate(dir);
@@ -179,6 +179,35 @@ const cases = [
     expect: (r) => r.code === 1 && /LICENSE/.test(r.output),
     describe: "should require a license file",
   },
+  {
+    name: "rejects a missing extension asset",
+    mutate: (dir) => {
+      rmSync(join(dir, "assets", "usable-icon.svg"));
+    },
+    expect: (r) => r.code === 1 && /references missing file/.test(r.output),
+    describe: "should catch an icon path that does not resolve",
+  },
+  {
+    name: "rejects an extension path escaping the plugin root",
+    mutate: (dir) => {
+      const m = JSON.parse(readFileSync(join(dir, "plugin.json"), "utf8"));
+      m.extensions["com.openai"].interface.logo = "../../../etc/passwd";
+      writeFileSync(join(dir, "plugin.json"), JSON.stringify(m, null, 2));
+    },
+    expect: (r) => r.code === 1 && /(escapes the plugin root|must be plugin-relative)/.test(r.output),
+    describe: "should enforce containment on extension-declared paths",
+  },
+  {
+    name: "rejects an extension namespace without a reverse domain",
+    mutate: (dir) => {
+      const m = JSON.parse(readFileSync(join(dir, "plugin.json"), "utf8"));
+      m.extensions.codex = m.extensions["com.openai"];
+      delete m.extensions["com.openai"];
+      writeFileSync(join(dir, "plugin.json"), JSON.stringify(m, null, 2));
+    },
+    expect: (r) => r.code === 1 && /reverse-domain namespace/.test(r.output),
+    describe: "should require reverse-domain extension keys",
+  },
   {
     name: "rejects an undocumented MCP url",
     mutate: (dir) => {