diff --git a/docs/api.md b/docs/api.md
index 19f1942..2c1f934 100644
--- a/docs/api.md
+++ b/docs/api.md
@@ -11,21 +11,21 @@ Query contexts default to the factory document when omitted. `closest()`, `first
 
 | Method | Result |
 | --- | --- |
-| [`byClass(cls, context)`](../src/nwsapi.mts#L3855) | Returns elements with the class name. |
-| [`byId(id, context)`](../src/nwsapi.mts#L3853) | Returns elements with the ID. Duplicate IDs are allowed by default. |
-| [`byTag(tag, context)`](../src/nwsapi.mts#L3854) | Returns elements with the tag name. Use `*` for all elements. |
-| [`closest(selectors, element, callback)`](../src/nwsapi.mts#L3861) | Returns the nearest match, starting with the element, or `null`. |
-| [`compile(selector, mode, callback, relative)`](../src/nwsapi.mts#L3863) | Compiles a selector into a resolver function. This is an advanced API. |
-| [`configure(option, clear)`](../src/nwsapi.mts#L3864) | Reads or changes options. Pass `true` as the second argument to clear compiled selectors. |
-| [`emit(message, proto)`](../src/nwsapi.mts#L3866) | Reports an error using the configured error policy. |
-| [`first(selectors, context, callback)`](../src/nwsapi.mts#L3857) | Returns the first matching descendant, or `null`. |
-| [`install(all)`](../src/nwsapi.mts#L3872) | Replaces native selector methods. Pass `true` to also replace collection methods. |
-| [`match(selectors, element, callback)`](../src/nwsapi.mts#L3858) | Returns whether the element matches. |
-| [`registerCombinator(combinator, resolver)`](../src/nwsapi.mts#L3879) | Adds a relationship between elements using trusted resolver code. |
-| [`registerOperator(operator, resolver)`](../src/nwsapi.mts#L3904) | Adds an attribute operator using a resolver with `p1`, `p2`, and `p3` fields. |
-| [`registerSelector(name, rexp, func)`](../src/nwsapi.mts#L3926) | Adds a selector pattern and a compiler callback that returns `source` and `status`. |
-| [`select(selectors, context, callback)`](../src/nwsapi.mts#L3859) | Returns an array of matching descendants, or an empty array. |
-| [`uninstall()`](../src/nwsapi.mts#L3873) | Restores the native methods saved by `install()`. |
+| [`byClass(cls, context)`](../src/nwsapi.mts#L3859) | Returns elements with the class name. |
+| [`byId(id, context)`](../src/nwsapi.mts#L3857) | Returns elements with the ID. Duplicate IDs are allowed by default. |
+| [`byTag(tag, context)`](../src/nwsapi.mts#L3858) | Returns elements with the tag name. Use `*` for all elements. |
+| [`closest(selectors, element, callback)`](../src/nwsapi.mts#L3865) | Returns the nearest match, starting with the element, or `null`. |
+| [`compile(selector, mode, callback, relative)`](../src/nwsapi.mts#L3867) | Compiles a selector into a resolver function. This is an advanced API. |
+| [`configure(option, clear)`](../src/nwsapi.mts#L3868) | Reads or changes options. Pass `true` as the second argument to clear compiled selectors. |
+| [`emit(message, proto)`](../src/nwsapi.mts#L3870) | Reports an error using the configured error policy. |
+| [`first(selectors, context, callback)`](../src/nwsapi.mts#L3861) | Returns the first matching descendant, or `null`. |
+| [`install(all)`](../src/nwsapi.mts#L3876) | Replaces native selector methods. Pass `true` to also replace collection methods. |
+| [`match(selectors, element, callback)`](../src/nwsapi.mts#L3862) | Returns whether the element matches. |
+| [`registerCombinator(combinator, resolver)`](../src/nwsapi.mts#L3883) | Adds a relationship between elements using trusted resolver code. |
+| [`registerOperator(operator, resolver)`](../src/nwsapi.mts#L3908) | Adds an attribute operator using a resolver with `p1`, `p2`, and `p3` fields. |
+| [`registerSelector(name, rexp, func)`](../src/nwsapi.mts#L3930) | Adds a selector pattern and a compiler callback that returns `source` and `status`. |
+| [`select(selectors, context, callback)`](../src/nwsapi.mts#L3863) | Returns an array of matching descendants, or an empty array. |
+| [`uninstall()`](../src/nwsapi.mts#L3877) | Restores the native methods saved by `install()`. |
 
 <details>
 <summary>Configuration</summary>
@@ -60,22 +60,22 @@ These exports support extensions and debugging. Prefer query methods and `config
 
 | Member | Purpose |
 | --- | --- |
-| [`CFG`](../src/nwsapi.mts#L3841) | Contains the compiler syntax settings. |
-| [`Config`](../src/nwsapi.mts#L3867) | Contains the active options. Use `configure()` to change them. |
-| [`M_BODY`](../src/nwsapi.mts#L3844) | Contains the matching resolver body template. |
-| [`M_TEST`](../src/nwsapi.mts#L3848) | Contains the matching resolver test template. |
-| [`matchLambdas`](../src/nwsapi.mts#L3833) | Caches compiled matching functions, not DOM results. |
-| [`matchResolvers`](../src/nwsapi.mts#L3836) | Caches matching plans, not DOM results. |
-| [`N_BODY`](../src/nwsapi.mts#L3845) | Exposes the matching resolver body template. |
-| [`N_TEST`](../src/nwsapi.mts#L3849) | Contains the alternate resolver test template. |
-| [`Operators`](../src/nwsapi.mts#L3875) | Contains registered attribute operators. |
-| [`S_BODY`](../src/nwsapi.mts#L3843) | Contains the selection resolver body template. |
-| [`S_TEST`](../src/nwsapi.mts#L3847) | Contains the selection resolver test template. |
-| [`selectLambdas`](../src/nwsapi.mts#L3834) | Caches compiled selection functions, not DOM results. |
-| [`Selectors`](../src/nwsapi.mts#L3876) | Contains registered selector extensions. |
-| [`selectResolvers`](../src/nwsapi.mts#L3837) | Caches selection plans, not DOM results. |
-| [`Snapshot`](../src/nwsapi.mts#L3868) | Contains the document state and helpers used by compiled selectors. |
-| [`Version`](../src/nwsapi.mts#L3870) | Contains the engine version string. |
+| [`CFG`](../src/nwsapi.mts#L3845) | Contains the compiler syntax settings. |
+| [`Config`](../src/nwsapi.mts#L3871) | Contains the active options. Use `configure()` to change them. |
+| [`M_BODY`](../src/nwsapi.mts#L3848) | Contains the matching resolver body template. |
+| [`M_TEST`](../src/nwsapi.mts#L3852) | Contains the matching resolver test template. |
+| [`matchLambdas`](../src/nwsapi.mts#L3837) | Caches compiled matching functions, not DOM results. |
+| [`matchResolvers`](../src/nwsapi.mts#L3840) | Caches matching plans, not DOM results. |
+| [`N_BODY`](../src/nwsapi.mts#L3849) | Exposes the matching resolver body template. |
+| [`N_TEST`](../src/nwsapi.mts#L3853) | Contains the alternate resolver test template. |
+| [`Operators`](../src/nwsapi.mts#L3879) | Contains registered attribute operators. |
+| [`S_BODY`](../src/nwsapi.mts#L3847) | Contains the selection resolver body template. |
+| [`S_TEST`](../src/nwsapi.mts#L3851) | Contains the selection resolver test template. |
+| [`selectLambdas`](../src/nwsapi.mts#L3838) | Caches compiled selection functions, not DOM results. |
+| [`Selectors`](../src/nwsapi.mts#L3880) | Contains registered selector extensions. |
+| [`selectResolvers`](../src/nwsapi.mts#L3841) | Caches selection plans, not DOM results. |
+| [`Snapshot`](../src/nwsapi.mts#L3872) | Contains the document state and helpers used by compiled selectors. |
+| [`Version`](../src/nwsapi.mts#L3874) | Contains the engine version string. |
 
 </details>
 
diff --git a/src/nwsapi.mts b/src/nwsapi.mts
index 709a826..39dba9e 100644
--- a/src/nwsapi.mts
+++ b/src/nwsapi.mts
@@ -3378,6 +3378,10 @@
       }
     },
     // equivalent of w3c 'querySelector' method
+    // Reuse the stop callback when first() has no user callback.
+    firstMatch = function firstMatch() {
+      return false
+    },
     first = function _querySelector(selectors, context, callback) {
       var element, match
 
@@ -3408,13 +3412,11 @@
           selectors,
           context,
           typeof callback == 'function'
-            ? function firstMatch(element) {
+            ? function firstMatchCallback(element) {
                 callback(element)
                 return false
               }
-            : function firstMatch() {
-                return false
-              },
+            : firstMatch,
         )[0] || null
       )
     },
@@ -3430,52 +3432,52 @@
 
       if (selectors) {
         if ((resolver = selectResolvers.get(selectors))) {
-          if (resolver.context === context && resolver.callback === callback) {
-            var i,
-              l,
-              list,
-              f = resolver.factory,
-              n = resolver.nodeset
-            if (n.length > 1) {
-              for (i = 0, l = n.length; l > i; ++i) {
-                list = fetch[n[i][0]](n[i].slice(1), context)
-                if (f[i] !== null) {
-                  f[i](list, callback, context, nodes)
-                } else {
-                  nodes = nodes.concat(list)
-                }
-              }
-              if (l > 1 && nodes.length > 1) {
-                nodes.sort(documentOrder)
-                hasDupes && (nodes = unique(nodes))
-              }
-            } else {
-              list = fetch[n[0][0]](n[0].slice(1), context)
-              if (f[0]) {
-                nodes = f[0](list, callback, context, nodes)
+          var i,
+            l,
+            list,
+            f = resolver.factory,
+            n = resolver.nodeset
+          if (n.length > 1) {
+            for (i = 0, l = n.length; l > i; ++i) {
+              list = fetch[n[i][0]](n[i].slice(1), context)
+              if (f[i] !== null) {
+                f[i](list, callback, context, nodes)
               } else {
-                nodes = list
+                nodes = nodes.concat(list)
               }
             }
-            if (typeof callback == 'function') {
-              nodes = concatCall(nodes, callback)
+            if (l > 1 && nodes.length > 1) {
+              nodes.sort(documentOrder)
+              hasDupes && (nodes = unique(nodes))
             }
-            return !Config.NODE_LIST
-              ? nodes
-              : isInstanceOf(nodes)
-                ? nodes
-                : toNodeList(nodes)
+          } else if (n.length) {
+            list = fetch[n[0][0]](n[0].slice(1), context)
+            nodes = f[0] ? f[0](list, callback, context, nodes) : list
+          }
+          if (typeof callback == 'function') {
+            nodes = concatCall(nodes, callback)
           }
+          return !Config.NODE_LIST
+            ? nodes
+            : isInstanceOf(nodes)
+              ? nodes
+              : toNodeList(nodes)
         }
       }
 
-      // save/reuse factory and closure collection
-      selectResolvers.set(
-        selectors,
-        collect(parse(selectors, true), context, callback),
-      )
+      resolver = collect(parse(selectors, true), context, callback)
+      nodes = resolver.results
 
-      nodes = selectResolvers.get(selectors).results
+      // Cache the query plan, never the answer. 'results' is a live list of
+      // matched elements and 'htmlset' closes over the context, so caching
+      // the whole collection kept a removed subtree alive for as long as its
+      // selector stayed in the cache. What is kept here is context-free,
+      // which also lets a plan be reused across contexts instead of only for
+      // the one it was built against.
+      selectResolvers.set(selectors, {
+        factory: resolver.factory,
+        nodeset: resolver.nodeset,
+      })
 
       if (typeof callback == 'function') {
         nodes = concatCall(nodes, callback)
@@ -3524,6 +3526,8 @@
           }
         }
 
+        // unescape before recording the token: 'nodeset' is what a later
+        // run rebuilds its candidate list from, so the two must agree
         token[2] = unescapeIdentifier(token[2])
         nodeset[i] = token[1] + token[2]
         // An escaped space cannot be part of a class token.
diff --git a/test/repo/e2e/upstream/fixtures/plan-cache.html b/test/repo/e2e/upstream/fixtures/plan-cache.html
new file mode 100644
index 0000000..0ef3ec8
--- /dev/null
+++ b/test/repo/e2e/upstream/fixtures/plan-cache.html
@@ -0,0 +1,40 @@
+<!doctype html>
+<meta charset="utf-8">
+<title>Context-free query plans</title>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<body><main><p class="a.b"></p><p></p></main>
+<script>
+test(() => {
+  const engine = NW.Dom;
+  const main = document.querySelector('main');
+  const other = document.createDocumentFragment();
+  other.append(main.cloneNode(true));
+  for (const selector of ['p', 'p.a\\.b', '.a\\.b', 'p, main', '.missing\\ class']) {
+    const expected = Array.from(main.querySelectorAll(selector));
+    const seen = [];
+    assert_array_equals(engine.select(selector, main, element => { seen.push(element); }), expected);
+    assert_array_equals(seen, expected);
+    const plan = engine.selectResolvers.get(selector);
+    assert_array_equals(Object.keys(plan).sort(), ['factory', 'nodeset']);
+    for (const context of [other, main, other]) {
+      assert_array_equals(engine.select(selector, context), Array.from(context.querySelectorAll(selector)));
+      assert_equals(engine.first(selector, context), context.querySelector(selector));
+      assert_equals(engine.selectResolvers.get(selector), plan);
+    }
+  }
+  main.firstElementChild.remove();
+  assert_array_equals(engine.select('p.a\\.b', main), []);
+  assert_equals(engine.first('p.a\\.b', main), null);
+  assert_equals(engine.select('p.a\\.b', other).length, 1);
+}, 'Cached plans exclude DOM and callback references, survive context changes, and see mutations');
+test(t => {
+  const engine = NW.Dom;
+  engine.configure({ VERBOSITY: false, LOGERRORS: false }, true);
+  t.add_cleanup(() => { engine.configure({ VERBOSITY: true, LOGERRORS: true }, true); });
+  for (let repeat = 0; repeat < 2; repeat++) {
+    assert_array_equals(engine.select('div[class="x\n"]', document), []);
+    assert_equals(engine.first('div[class="x\n"]', document), null);
+  }
+}, 'Quiet parse failures remain empty when their zero-candidate plan is reused');
+</script>
diff --git a/test/repo/e2e/upstream/manifest.mts b/test/repo/e2e/upstream/manifest.mts
index d768611..9947e52 100644
--- a/test/repo/e2e/upstream/manifest.mts
+++ b/test/repo/e2e/upstream/manifest.mts
@@ -36,6 +36,11 @@ export const manifest: Array<{
   install?: boolean
   legacyMap?: boolean
 }> = [
+  {
+    path: '/_repo/test/repo/e2e/upstream/fixtures/plan-cache.html',
+    note: 'local WPT regression: context-free plans, escaped tokens, callbacks, and DOM mutation',
+    install: false,
+  },
   {
     path: '/_repo/test/repo/e2e/upstream/fixtures/wrapper-arguments.html',
     note: 'local WPT regression: installed wrapper arities and callbacks',
diff --git a/test/repo/unit/plan-cache.test.mts b/test/repo/unit/plan-cache.test.mts
new file mode 100644
index 0000000..fc64961
--- /dev/null
+++ b/test/repo/unit/plan-cache.test.mts
@@ -0,0 +1,34 @@
+import { JSDOM } from 'jsdom'
+import { expect, test } from 'vitest'
+import factory from '../../../src/nwsapi.js'
+
+test('cached plans retain no query results, context, or callback', t => {
+  const { window } = new JSDOM('<main><p class="a.b"></p><p></p></main>', {
+    url: 'https://example.test/',
+  })
+  t.onTestFinished(() => window.close())
+  const engine = factory(window)
+  const doc = window.document
+  const main = doc.querySelector('main')!
+  const selector = 'p.a\\.b'
+  const seen: Element[] = []
+  expect(
+    engine.select(selector, main, element => {
+      seen.push(element)
+    }),
+  ).toEqual([main.firstElementChild])
+  const cache = Reflect.get(engine, 'selectResolvers')
+  const plan = cache.get(selector)
+  expect(Object.keys(plan).toSorted()).toEqual(['factory', 'nodeset'])
+  expect(seen).toEqual([main.firstElementChild])
+  const other = doc.createDocumentFragment()
+  other.append(main.cloneNode(true))
+  expect(engine.select(selector, other)).toEqual([other.firstChild!.firstChild])
+  expect(cache.get(selector)).toBe(plan)
+  main.firstElementChild!.remove()
+  expect(engine.select(selector, main)).toEqual([])
+  expect(engine.first(selector, main)).toBeNull()
+  expect(cache.get(selector)).toBe(plan)
+  expect(engine.select(selector, other)).toEqual([other.firstChild!.firstChild])
+  expect(cache.get(selector)).toBe(plan)
+})