diff --git a/.changeset/moody-nails-admire.md b/.changeset/moody-nails-admire.md
new file mode 100644
index 000000000..3660db76e
--- /dev/null
+++ b/.changeset/moody-nails-admire.md
@@ -0,0 +1,5 @@
+---
+"gitbook": patch
+---
+
+Persist content selection (tabs and other `select` blocks) in localStorage only, dropping the `?select=` query parameter from the URL. A tab click still writes the tab's hash, so a copied URL lands on that tab and reactivates it on load.
diff --git a/packages/gitbook/src/components/DocumentView/Tabs/DynamicTabs.tsx b/packages/gitbook/src/components/DocumentView/Tabs/DynamicTabs.tsx
index c02d75dc7..d33eddadf 100644
--- a/packages/gitbook/src/components/DocumentView/Tabs/DynamicTabs.tsx
+++ b/packages/gitbook/src/components/DocumentView/Tabs/DynamicTabs.tsx
@@ -41,11 +41,7 @@ export interface TabsItem {
  * click we pin the exact pane via `data-select-pinned`/`-unpinned` (a client-only override that
  * reverts to first-match on reload). The tablist highlight follows the same resolved tab.
  */
-export function DynamicTabs(props: {
-    tabs: TabsItem[];
-    setClassName: string;
-    className?: string;
-}) {
+export function DynamicTabs(props: { tabs: TabsItem[]; setClassName: string; className?: string }) {
     const { tabs, setClassName, className } = props;
     const { activate } = useSelect();
     // The tab the visitor explicitly clicked this session (not persisted — reload reverts to CSS).
@@ -74,9 +70,10 @@ export function DynamicTabs(props: {
             }
             activate(tab.slug);
             setManualId(tabId);
-            // The hash is purely positional now — `select` carries the selection — so writing it just
-            // makes a copied URL land on this tab. We deliberately bypass the navigation context: it
-            // would report a hash change and scroll the tab the visitor is already looking at.
+            // The hash is the only URL handle for a selection, so a copied URL lands on this tab and
+            // `useSelectAnchor` re-activates its slug on load. We deliberately bypass the navigation
+            // context: it would report a hash change and scroll the tab the visitor is already
+            // looking at.
             window.history.replaceState(null, '', resolveAnchorURL(`#${tab.id}`, window.location));
         },
         [tabs, activate]
diff --git a/packages/gitbook/src/components/DocumentView/Tabs/Tabs.tsx b/packages/gitbook/src/components/DocumentView/Tabs/Tabs.tsx
index 5308f586b..04a9229cf 100644
--- a/packages/gitbook/src/components/DocumentView/Tabs/Tabs.tsx
+++ b/packages/gitbook/src/components/DocumentView/Tabs/Tabs.tsx
@@ -100,8 +100,8 @@ function SelectGroupStyle({ slugs }: { slugs: string[] }) {
  *
  * Same-named tabs deliberately share a slug — selecting one syncs every tab of that name, here and
  * on other pages, which is the whole point of name-based selection. We don't disambiguate duplicates
- * with a positional suffix: that would desync the duplicate and, because the slug rides in the
- * frozen `?select=` URL, a shared link would silently retarget when tabs are renamed or reordered.
+ * with a positional suffix: that would desync the duplicate and make a stored selection retarget
+ * whenever tabs are renamed or reordered.
  */
 function withSelectSlugs<T extends { id: string; title: string }>(
     items: T[]
diff --git a/packages/gitbook/src/components/Select/SelectProvider.tsx b/packages/gitbook/src/components/Select/SelectProvider.tsx
index d614b2ab9..cddd41863 100644
--- a/packages/gitbook/src/components/Select/SelectProvider.tsx
+++ b/packages/gitbook/src/components/Select/SelectProvider.tsx
@@ -1,67 +1,28 @@
 'use client';
 
-import { SELECT_URL_PARAM, selectStore } from '@/lib/select';
-import { parseAsString, useQueryState } from 'nuqs';
+import { selectStore } from '@/lib/select';
 import type React from 'react';
-import { useEffect, useLayoutEffect, useRef } from 'react';
-import { useSelect } from './useSelect';
+import { useEffect, useLayoutEffect } from 'react';
 import { useSelectAnchor } from './useSelectAnchor';
 
 // `useLayoutEffect` runs before paint but warns during SSR (effects don't run on the server anyway),
 // so fall back to `useEffect` there.
 const useIsomorphicLayoutEffect = typeof document !== 'undefined' ? useLayoutEffect : useEffect;
 
-function parseSelectParam(value: string | null): string[] {
-    if (!value) {
-        return [];
-    }
-    return value
-        .split(',')
-        .map((slug) => slug.trim())
-        .filter(Boolean);
-}
-
 /**
- * Wires the `select` store to the `?select=` URL param and hydrates it from localStorage. Mounted
- * once at the site layout level (inside NuqsAdapter). Provides no React context — the store is a
- * module singleton — so it simply renders its children.
+ * Hydrates the `select` store from localStorage. Mounted once at the site layout level. Provides no
+ * React context — the store is a module singleton — so it simply renders its children.
  */
 export function SelectProvider(props: { children: React.ReactNode }) {
-    const [param, setParam] = useQueryState(SELECT_URL_PARAM, parseAsString);
-    const { slugs } = useSelect();
-    // The last value we wrote to the URL, so we can tell our own writes apart from external ones.
-    const mirroredRef = useRef<string | null>(null);
-
-    useSelectAnchor();
-
-    // Adopt whatever the pre-paint script already merged (URL + storage) into the in-memory store.
-    // Layout effect so the store (and the tab highlight it drives) is settled before first paint,
-    // matching the `<html data-sel-*>` the pre-paint script already applied.
+    // Adopt what the pre-paint script already applied, before paint, so the store (and the tab
+    // highlight it drives) agrees with the `<html data-sel-*>` on the page.
+    // Must stay registered before `useSelectAnchor`, whose effect can activate slugs: a write before
+    // hydration would persist over the visitor's stored list instead of merging into it.
     useIsomorphicLayoutEffect(() => {
         selectStore.init();
     }, []);
 
-    // URL → store: a shared link or client-side navigation carrying ?select= prepends its slugs, so
-    // the link wins while the visitor's other preferences survive.
-    useEffect(() => {
-        if (param === mirroredRef.current) {
-            return;
-        }
-        const fromUrl = parseSelectParam(param);
-        if (fromUrl.length > 0) {
-            selectStore.setSlugs([...fromUrl, ...selectStore.getState().slugs]);
-        }
-    }, [param]);
-
-    // store → URL: keep ?select= as a shareable mirror of the recency list (replaceState, no history spam).
-    useEffect(() => {
-        const desired = slugs.length > 0 ? slugs.join(',') : null;
-        if ((param ?? null) === desired) {
-            return;
-        }
-        mirroredRef.current = desired;
-        setParam(desired);
-    }, [slugs, param, setParam]);
+    useSelectAnchor();
 
     return props.children;
 }
diff --git a/packages/gitbook/src/components/Select/SelectStateScript.tsx b/packages/gitbook/src/components/Select/SelectStateScript.tsx
index d30b9451d..3cd454b49 100644
--- a/packages/gitbook/src/components/Select/SelectStateScript.tsx
+++ b/packages/gitbook/src/components/Select/SelectStateScript.tsx
@@ -1,4 +1,4 @@
-import { SELECT_LIST_CAP, SELECT_STORAGE_KEY, SELECT_URL_PARAM } from '@/lib/select';
+import { SELECT_LIST_CAP, SELECT_STORAGE_KEY } from '@/lib/select';
 import { applySelectStateScript } from './script';
 
 /**
@@ -6,11 +6,7 @@ import { applySelectStateScript } from './script';
  * so the right content variant renders with no flash. Mounted once in the root layout head.
  */
 export function SelectStateScript() {
-    const scriptArgs = JSON.stringify([
-        SELECT_STORAGE_KEY,
-        SELECT_URL_PARAM,
-        SELECT_LIST_CAP,
-    ]).slice(1, -1);
+    const scriptArgs = JSON.stringify([SELECT_STORAGE_KEY, SELECT_LIST_CAP]).slice(1, -1);
 
     return (
         <script
diff --git a/packages/gitbook/src/components/Select/script.ts b/packages/gitbook/src/components/Select/script.ts
index 53d8f9d44..2bec503ae 100644
--- a/packages/gitbook/src/components/Select/script.ts
+++ b/packages/gitbook/src/components/Select/script.ts
@@ -1,14 +1,14 @@
 /**
- * Read the `select` state (URL `?select=` + localStorage) and apply it to `<html>` as `data-sel-N`
- * attributes as early as possible, so the correct content variant is visible before hydration — no
- * flash, and it works on cached/static HTML.
+ * Read the `select` state from localStorage and apply it to `<html>` as `data-sel-N` attributes as
+ * early as possible, so the correct content variant is visible before hydration — no flash, and it
+ * works on cached/static HTML.
  *
  * NOTE: this runs in `<head>` before `<body>` exists, and is stringified and injected — so it must be
  * self-contained (no imports/closures) and touch only `document.documentElement`. The attribute name
- * and merge rules mirror `lib/select` (`selectRankAttribute`, the store's `normalize`); keep them in
- * sync. URL slugs are prepended so a shared link wins while the visitor's other preferences survive.
+ * and dedupe rules mirror `lib/select` (`selectRankAttribute`, the store's `normalize`); keep them in
+ * sync.
  */
-export function applySelectStateScript(storageKey: string, urlParam: string, cap: number) {
+export function applySelectStateScript(storageKey: string, cap: number) {
     try {
         const slugs: string[] = [];
         // A Set (not a plain object) so slugs like "constructor"/"toString" aren't treated as
@@ -26,22 +26,14 @@ export function applySelectStateScript(storageKey: string, urlParam: string, cap
             slugs.push(slug);
         };
 
-        const fromUrl = new URLSearchParams(window.location.search).get(urlParam);
-        if (fromUrl) {
-            const parts = fromUrl.split(',');
-            for (let i = 0; i < parts.length; i++) {
-                push(parts[i]);
-            }
-        }
-
         const storedStr = window.localStorage.getItem(storageKey);
         if (storedStr) {
             const stored = JSON.parse(storedStr);
             // Only trust a real array — corrupted storage (a string, or an object with `length`)
             // would otherwise iterate per character/index. Matches the runtime store's handling.
             if (Array.isArray(stored)) {
-                for (let j = 0; j < stored.length; j++) {
-                    push(stored[j]);
+                for (let i = 0; i < stored.length; i++) {
+                    push(stored[i]);
                 }
             }
         }
@@ -56,8 +48,6 @@ export function applySelectStateScript(storageKey: string, urlParam: string, cap
                 el.removeAttribute(attribute);
             }
         }
-
-        window.localStorage.setItem(storageKey, JSON.stringify(slugs));
     } catch {
         // localStorage blocked (private mode) or malformed state — fall through to block defaults.
     }
diff --git a/packages/gitbook/src/lib/select/constants.ts b/packages/gitbook/src/lib/select/constants.ts
index 4df966fbd..c841c5979 100644
--- a/packages/gitbook/src/lib/select/constants.ts
+++ b/packages/gitbook/src/lib/select/constants.ts
@@ -5,12 +5,6 @@
  */
 export const SELECT_STORAGE_KEY = '@gitbook/select';
 
-/**
- * Single query parameter carrying shareable selection state, e.g. `?select=python,cloud`
- * (most-recent-first). A fixed key so author-chosen names never collide with reserved params.
- */
-export const SELECT_URL_PARAM = 'select';
-
 /**
  * How many slugs are remembered, most-recent-first. This is also the depth of the CSS "rank ladder"
  * (see generateSelectCSS): since pane visibility is CSS-only, the ladder must cover every stored
diff --git a/packages/gitbook/src/lib/select/generateSelectCSS.ts b/packages/gitbook/src/lib/select/generateSelectCSS.ts
index 2854080ce..5b1e44ac2 100644
--- a/packages/gitbook/src/lib/select/generateSelectCSS.ts
+++ b/packages/gitbook/src/lib/select/generateSelectCSS.ts
@@ -108,7 +108,7 @@ export function generateSelectCSS(candidateSlugs: string[], depth = SELECT_LIST_
     // Duplicate tab names in one group would otherwise reveal two panes at once. Keep only the first:
     // hide any option pane preceded by a same-slug sibling. Emitted last and prefixed with `html` so
     // it beats the show rules above (equal specificity, later source order). The slug stays shared, so
-    // syncing and the `?select=` URL are unaffected — only the second pane's visibility changes.
+    // syncing is unaffected — only the second pane's visibility changes.
     for (const slug of slugs) {
         const value = escapeCssString(slug);
         const pane = `[${SELECT_OPTION_ATTR}="${value}"]`;
diff --git a/packages/gitbook/src/lib/select/slug.test.ts b/packages/gitbook/src/lib/select/slug.test.ts
index b76c67fb5..1736b3141 100644
--- a/packages/gitbook/src/lib/select/slug.test.ts
+++ b/packages/gitbook/src/lib/select/slug.test.ts
@@ -2,8 +2,8 @@ import { describe, expect, it } from 'bun:test';
 import { SLUG_MAX_CODE_POINTS, slugifySelectValue } from './slug';
 
 describe('slugifySelectValue', () => {
-    // This table IS the frozen public contract for `?select=` URLs — see SLUG_ALGO_VERSION.
-    // Changing any expectation here is a breaking change to already-shared links.
+    // This table IS the slug contract — see SLUG_ALGO_VERSION. Changing any expectation here orphans
+    // selections already persisted in visitors' localStorage.
     const cases: Array<[input: string, expected: string]> = [
         ['Python', 'python'],
         ['JavaScript', 'javascript'],
diff --git a/packages/gitbook/src/lib/select/slug.ts b/packages/gitbook/src/lib/select/slug.ts
index 0518b4077..b4864b76e 100644
--- a/packages/gitbook/src/lib/select/slug.ts
+++ b/packages/gitbook/src/lib/select/slug.ts
@@ -1,35 +1,35 @@
 /**
  * Version of the slugification algorithm below.
  *
- * The slugs it produces are the keys that sync content across the site AND the values that appear
- * in the public `?select=` URL parameter. Once those URLs are in the wild the algorithm is frozen:
- * changing it would silently re-resolve links people have already shared. Any future change must
- * bump this version and be gated behind it, never applied in place.
+ * The slugs it produces are the keys that sync content across the site, baked into server-rendered
+ * markup and CSS and persisted in the visitor's localStorage. Changing the algorithm in place would
+ * orphan every stored selection and desync it from the markup, so any future change must bump this
+ * version and be gated behind it.
  */
 export const SLUG_ALGO_VERSION = 1;
 
 /**
  * Maximum slug length, counted in code points (not UTF-16 units, so we never cleave a surrogate
- * pair). Guards against pathological titles — 30 CJK characters is already ~270 bytes once
- * percent-encoded into `?select=`. Part of the frozen contract (see {@link SLUG_ALGO_VERSION}).
+ * pair). Guards against pathological titles bloating the generated CSS and stored state. Part of the
+ * contract (see {@link SLUG_ALGO_VERSION}).
  */
 export const SLUG_MAX_CODE_POINTS = 64;
 
 /**
  * Turn an author-typed name (a tab title, button label, picker option…) into a `select` slug.
  *
- * DO NOT CHANGE — this is the frozen public `?select=` URL contract (see {@link SLUG_ALGO_VERSION}).
- * The output must be byte-identical on the server (baking slugs into markup/CSS) and the client
- * (parsing URLs/storage), so it relies only on locale-independent primitives: Unicode NFKC
+ * DO NOT CHANGE in place — see {@link SLUG_ALGO_VERSION}. The output must be byte-identical on the
+ * server (baking slugs into markup/CSS) and the client (reading storage), so it relies only on
+ * locale-independent primitives: Unicode NFKC
  * normalization + `String.prototype.toLowerCase` (Unicode default case folding, not locale-sensitive).
  *
  * It keeps letters, numbers and marks from every script (so `café`, `安装`, `日本語` survive) plus a
  * small safelist of symbols — `+ # . _` — that distinguish technical names that would otherwise
  * collide (`c` vs `c++` vs `c#`, `node.js`, `on_prem`). Every other run of characters collapses to a
- * single `-`, and leading/trailing `-` are trimmed. A slug can never contain the `,` that delimits
- * `?select=`, and none of these characters need escaping in a URL-encoded query param — but the
- * safelist widens the set beyond bare word characters, so consumers that interpolate a slug into
- * another syntax must still escape for it (see the CSS escaping in generateSelectCSS).
+ * single `-`, and leading/trailing `-` are trimmed. A slug can never contain a `,`, which callers rely
+ * on to join slug lists into a single key (see `useResolvedSlug`) — but the safelist widens the set
+ * beyond bare word characters, so consumers that interpolate a slug into another syntax must still
+ * escape for it (see the CSS escaping in generateSelectCSS).
  *
  * Control, format, bidi and lone-surrogate characters (`\p{C}`) are dropped outright rather than
  * turned into a `-`, and the string is re-normalized after `toLowerCase` (case mapping can leave it
diff --git a/packages/gitbook/src/lib/select/store.hydration.test.ts b/packages/gitbook/src/lib/select/store.hydration.test.ts
new file mode 100644
index 000000000..a24831e74
--- /dev/null
+++ b/packages/gitbook/src/lib/select/store.hydration.test.ts
@@ -0,0 +1,56 @@
+import { afterEach, beforeEach, describe, expect, it } from 'bun:test';
+import { SELECT_STORAGE_KEY } from './constants';
+
+// Own file, own module instance: the store hydrates once per page load, so the "mutation before
+// init()" path can only be exercised on a store nothing has touched yet.
+const storage = new Map<string, string>();
+const globals = globalThis as unknown as { localStorage?: unknown };
+const originalLocalStorage = Object.getOwnPropertyDescriptor(globalThis, 'localStorage');
+
+beforeEach(() => {
+    storage.clear();
+    globals.localStorage = {
+        getItem: (key: string) => storage.get(key) ?? null,
+        setItem: (key: string, value: string) => {
+            storage.set(key, value);
+        },
+        removeItem: (key: string) => {
+            storage.delete(key);
+        },
+    };
+});
+
+// Bun shares globals across test files, so leave `localStorage` exactly as we found it (absent) —
+// every other suite relies on the `typeof localStorage` guard in `lib/browser` short-circuiting.
+afterEach(() => {
+    if (originalLocalStorage) {
+        Object.defineProperty(globalThis, 'localStorage', originalLocalStorage);
+    } else {
+        delete globals.localStorage;
+    }
+    storage.clear();
+});
+
+describe('select store hydration', () => {
+    it('merges a mutation that lands before init() into the stored list', async () => {
+        storage.set(SELECT_STORAGE_KEY, JSON.stringify(['go', 'rust']));
+
+        // Query string busts the module cache so this store is untouched by the sibling suite; the
+        // specifier is held in a variable because TS won't resolve it as a literal.
+        const freshStore = './store?hydration';
+        const { activate, getState, init } = (await import(freshStore)) as typeof import('./store');
+
+        // A deep-linked pane activating during hydration, ahead of the provider's init effect.
+        activate('python');
+        expect(getState().slugs).toEqual(['python', 'go', 'rust']);
+        expect(JSON.parse(storage.get(SELECT_STORAGE_KEY) as string)).toEqual([
+            'python',
+            'go',
+            'rust',
+        ]);
+
+        // The later init() must not resurrect the pre-mutation list.
+        init();
+        expect(getState().slugs).toEqual(['python', 'go', 'rust']);
+    });
+});
diff --git a/packages/gitbook/src/lib/select/store.test.ts b/packages/gitbook/src/lib/select/store.test.ts
index c1b8f68c0..1bc0f28ea 100644
--- a/packages/gitbook/src/lib/select/store.test.ts
+++ b/packages/gitbook/src/lib/select/store.test.ts
@@ -60,7 +60,7 @@ describe('select store', () => {
             unsubscribe();
         });
 
-        it('does not notify when the list is unchanged (prevents URL mirror loops)', () => {
+        it('does not notify when the list is unchanged (avoids redundant re-renders)', () => {
             setSlugs(['python', 'go']);
             let calls = 0;
             const unsubscribe = subscribe(() => {
diff --git a/packages/gitbook/src/lib/select/store.ts b/packages/gitbook/src/lib/select/store.ts
index 2cfde7756..a07345e3b 100644
--- a/packages/gitbook/src/lib/select/store.ts
+++ b/packages/gitbook/src/lib/select/store.ts
@@ -50,8 +50,11 @@ function sameList(a: string[], b: string[]): boolean {
 }
 
 function commit(nextSlugs: string[]) {
+    // Latch hydration even for callers that replace the list wholesale, so a later `init()` can't
+    // overwrite this write with what was in storage beforehand.
+    hydrate();
     const slugs = normalize(nextSlugs);
-    // No-op when nothing changed — this is what keeps the store⇄URL mirror from looping.
+    // No-op when nothing changed, so we don't rewrite storage or re-render every consumer.
     if (sameList(slugs, state.slugs)) {
         return;
     }
@@ -68,6 +71,9 @@ export function activate(slug: string) {
     if (!slug) {
         return;
     }
+    // Hydrate before reading `state`, not just before writing: a mutation that lands ahead of `init()`
+    // (a deep-linked pane activating during hydration) must merge into the stored list, not replace it.
+    hydrate();
     commit([slug, ...state.slugs]);
 }
 
@@ -76,10 +82,11 @@ export function deactivate(slug: string) {
     if (!slug) {
         return;
     }
+    hydrate();
     commit(state.slugs.filter((s) => s !== slug));
 }
 
-/** Replace the whole list (used when hydrating from URL + storage). */
+/** Replace the whole list. */
 export function setSlugs(slugs: string[]) {
     commit(slugs);
 }
@@ -104,20 +111,25 @@ export function resolveActiveSlug(candidates: string[]): string | null {
 
 /**
  * Hydrate the in-memory store from localStorage (once per full page load). The pre-paint script has
- * already merged `?select=` into storage and written `<html>` before this runs, so we just adopt it;
- * we re-mirror to `<html>` too, to stay correct after a client-side navigation.
+ * already read the same storage and written `<html>` before this runs, so we just adopt it; we
+ * re-mirror to `<html>` too, to stay correct after a client-side navigation.
  */
 export function init() {
+    hydrate();
+    mirrorToHtml(state.slugs);
+    for (const listener of listeners) {
+        listener();
+    }
+}
+
+/** Read the persisted list into memory, once per page load. Silent — callers notify if they need to. */
+function hydrate() {
     if (initialized) {
         return;
     }
     initialized = true;
     const stored = getLocalStorageItem<string[]>(SELECT_STORAGE_KEY, []);
     state = { slugs: normalize(Array.isArray(stored) ? stored : []) };
-    mirrorToHtml(state.slugs);
-    for (const listener of listeners) {
-        listener();
-    }
 }
 
 /**