ci: dispatch workflows for folio and the replay ui (#73)

* feat(runner): stop the step loop at the first violation on request

* feat(testrun): report violations as a typed error under exit-on-violation

* feat(cli): add --exit-on-violation and exit 2 when it fires

* docs(cli): document --exit-on-violation, --max-steps, and exit codes

* fix(web): enumerate and query across shadow roots in both producers

* test(chrome): compare both producers on a shadow-dom parity page

* test(browser): drive a canvas-under-shadow-root fixture end to end

* fix(web): select the focused field inside a shadow root before typing

* fix(web): report the pathname as the screen when there is no hash route

* fix(web): settle on dom quiescence instead of returning at body ready

* feat(replay-ui): add data-testid hooks the dogfood spec drives

* feat(replay-ui): add the dogfood spec sanderling runs against the replay ui

* fix(replay-ui): scope the screenshot property to the named state panel

* chore(make): add per-platform sanderling build targets

* ci: add dispatch workflows for folio and the replay ui

* docs: describe the dispatch workflows and how to read a failure

* ci(folio): give the ios leg its jdk, android sdk, just, and a clean app start

* refactor(web): use max for the settle budget

* ci: pin calibrated seeds, skip the flaky ios reinstall, bound every job

* ci: authenticate and pin the buf setup step

the anonymous release download hit the shared runner ip rate limit and
failed the job with 'socket hang up' after three retries.

* docs: record that canvas apps need a dom proxy to be text-fuzzable

* fix(ios): bound lifecycle rpcs and claim the target device

a launch the simulator rejects sent the xctest session into a recovery
chain that answered minutes late or never, and the rpc had no deadline,
so the run hung with no trace and no error. also take a per-udid flock:
a second run's reinstall lands under the first's live automation session
and wedges it.

* docs(ci): correct the ios hang wording and note the device lock

* refactor(verifier): derive the lastAction shape from one field list

both hosts must show a spec the same lastAction. one ordered list now
feeds the goja object and the json the web host installs, so they
cannot drift.

* fix(web): install lastAction in the page before extractors read it

state.lastAction was hardcoded null on web, so every property reading it
was silently vacuous: a correct property passed without ever firing.

* fix(web): carry element identity on actions and fix findAll on paths

an action's target was coordinates only, so a property matching on which
element was acted upon could never fire. ax.findAll([a,b]) also returned
nothing on web.

* fix(chrome): wait out a route transition before sampling facts

the tree stays byte-identical and quiet across a cross-fade, so both the
quiet timer and the unchanged-tree escape called it settled mid-flight
and extractors read two screens at once.

* fix: bound the pre-run app launch

launch happens before the runner starts, so --duration never covered it
and a wedged driver hung with no trace and no error.

* fix(folio): read balances from merged cards and treat unreadable as unknown

compose for web merges the whole accountcard subtree, so the balance
child never exists there and every card parsed as 0. the property then
compared 0 to 0 and fired on any submit, which is a false positive
generator. unknown is now null and null is vacuously true.

* test(folio): cover merged-card parsing and unknown balances

* ci(folio): make web an expect-the-bug leg

the web runtime can observe the double submit now, so the health gate
understates it. seed 1 finds it at step 109, 3 runs out of 3.

* docs(ci): explain why a submit tap landing on home is the bug

* fix(ios): read a StaticText's label as its text

AXValue was the only source for text, but a StaticText carries its
string in AXLabel, so nothing on screen had .text on ios: a spec reading
it saw everything on android and nothing here.

* docs(ci): correct the calibrated step ranges

* fix(folio): stop convicting on arithmetic float64 cannot hold

past 2^53 cents the gap between representable values is 128, so a real
1600-cent move reads back as something else and the equality is false
for a healthy submit as readily as a double one. also match parseCents:
a sign or an oversized amount is rejected, not read as an amount.

* test(folio): pin the safe-integer guard and its boundary

* docs: stop teaching the zero-default that caused a false alarm

* docs: write down the silent-vacuity failure modes

* feat(folio): tag the home total and the card transaction count

the total was the only untagged node on the screen, so the spec had to
sum cards and a clipped card broke the sum.

* fix(folio): read the app's own total and refuse contaminated windows

summing cards went null when one was clipped, and the null poisoned the
carrier for the rest of the run. the balance window also spanned every
transaction since the last home visit, so the property convicted on
deltas it could not attribute: the old web witness was 3.16x the typed
amount, not 2x.

* test(folio): pin the window rules and the count invariant

* fix(folio): never read a frame that shows two screens

android dumps a cross-fade with both screens in the tree. the route said
add-transaction while an unscoped find said home, so the oracle took a
half-rendered total as fresh and convicted on a tap that committed
nothing. one function now decides the route and returns null when the
frame is ambiguous.

* test(folio): cover transition frames, card readings and creation

* fix(folio): only disambiguate counts that came from merged text

the equal-length digit rule exists because web merges the card and an
account named -1 makes '12' ambiguous. a dedicated count node has
nothing to disambiguate, so applying it there threw away real evidence.

* ci(folio): pin the recalibrated seeds and drop android to a health gate

web 3 and ios 7 convict 3 runs out of 3 with an exactly 2x witness.
android convicts 2 in 5 because the same seed does not walk the same
trajectory there, so it proves the app runs instead.

* docs(ci): describe the two properties and why android cannot convict

* fix(android): wait out a route cross-fade before snapshotting

the dump could hold two screens at once, and the runner refuses to act
on such a tree, so a quarter of android steps applied no action and the
count varied per run: the same seed never walked the same trajectory.
the ios companion and the chrome driver already do this.

* ci(folio): let the android leg run far enough to see its conviction

* docs: only the repo owner merges

* ci(folio): a thrown predicate is not a conviction

exit 2 means the run recorded a violation, and a predicate that throws
is recorded as one too. so was newAccountBalanceIsZero, an unrelated
property in the same spec. the gate read the exit code and went green
with detection dead.

* ci: install idb-companion from its tap and stop interpolating inputs

idb-companion is not in homebrew-core, so the ios leg died before it
built anything. replay-ui expanded dispatch inputs into the shell.

* docs: correct the snippets and numbers that drifted from the code

* test(sidecar): pin that a slow read counts toward the stability streak

* fix(web): read the page's extractors only on steps that count

the page advances the spec's carriers when it evaluates, but the runner
applied the result only on non-transitional steps. a discarded step
moved the window forward anyway, so the next accepted pair bracketed two
transactions while counting one submit, and convicted a healthy app.
extractor errors now fail the run instead of leaving goja's values in
current against v8's in previous.

* fix(chrome): anchor the transition deadline when the dom goes quiet

it was anchored at script start, so a page that churned past the window
reached the check already expired and returned mid cross-fade. the
driver now publishes the idle timeout it needs, since the caller's 1s
could never spend the 800ms window.

* fix(web): fail on a partial extractor override

same mixed-producer hazard as the install error: some extractors hold
the page's value and the rest hold goja's, and a property comparing
across that split fires on a healthy app.

* docs: six of seven, the seventh is the stock property

* fix(folio): drop a name two cards answer to

homeTxnCountsOf keyed on the account name and let the last card win, so
two accounts the fuzzer named the same collapsed into one entry. a
reading that saw one Travel card and a later one that saw both then
subtracted two different accounts' counts, and
submitCommitsOneTransactionPerAction convicted a healthy app of
double-submitting. it is a gated property in folio-run.sh, so that reads
as "found the submit bug" over a card scrolling into view.

same rule createdAccountHasNonZeroBalance already applies: a name
nothing can attribute is no evidence. counted over every card, since an
unreadable twin spoils the identity too.

* perf(folio): read each frame once

every extractor asked routeOf, and routeOf does five ax.find calls. on
web each find walks the document and every shadow root beneath it, so
the spec cost 110 tree walks a step; homeCards was parsed four times
over. now 5 and once.

keyed on the identity of the state object because both hosts build a new
one per step and hand that one object to every getter, so it cannot
outlive its frame. holding the reference is what keeps that true rather
than likely.

* fix(web): keep an undefined reading's index through JSON

json has no undefined, so an extractor whose getter returned one had its
whole index dropped by JSON.stringify. that index then kept goja's
dump-derived value while its neighbours held the page's, and a property
comparing previous to current across the split fires on a healthy app.
folio has nine on(route, tag) extractors, so this was most extractors on
most steps.

each reading is wrapped in a {value} envelope: the drop now happens
inside the entry, and an absent value means the getter returned
undefined, which is what the goja host records for the same getter. a
json null would instead claim it returned null and x.current ===
undefined would answer differently on the two hosts.

* feat(verifier): report the registered extractor count

the web path needs it to check the page sent one reading per extractor.

* fix(runner): fail when the page reports fewer readings than extractors

the comment here already claimed a partial override was fatal. it was
not: the skipped check only catches indices outside the extractor list,
so a page reporting values for some extractors and not others left the
rest holding goja's reading of the dump with nothing said.

* test(browser): drive an undefined reading through the whole web path

four layers carry it: the page's envelope, the driver's unwrap, the
runner's count check and the verifier's decode. each has a unit test and
only a run proves they compose. goes red both ways, decoding an absent
value as null and dropping the envelope.

* fix(web): offer the aria roles a user activates

only role=button was in the tappable set, so link, checkbox, radio,
switch, tab, option, the menuitems and treeitem were invisible to the
enumeration however plain the control looked. the replay ui builds its
step rows as <li role="option">, and the spec dogfooding it had to
hand-write an action to reach them because no default verb could see a
single row.

both producers build the set from the same role list, since the parity
test compares them element by element.

* test(browser): tap a role-based control end to end

every control on the page is an <li role="option">, the shape the
replay ui gives its step rows, and the spec carries no action of its
own: the property firing is the evidence the default enumeration offered
a tap on one.

* fix(web): read aria-disabled as disabled

the enabled fact came off the disabled property, which only real form
controls have. it reads undefined on the role-based controls the
tappable set now covers, so every one of them looked enabled however
plainly it was marked otherwise, and the fuzzer would spend actions on
inert ones.

both producers answer the same two ways, and the parity fixture carries
a disabled row so the comparison covers it: reverting one side alone
names the element and the fact.

* docs(replay-ui): the enumeration reaches step rows now

the comment said role="option" is not in the tappable selector set,
which stopped being true a few commits ago. selectAStep stays, for the
reason the tab weight below it stays: one row among the page's clickable
elements is a thin chance, and both step-facing properties go vacuous on
a run that never selects one.

* test(runner): bound the last-action test by steps, not wall clock

100ms of wall clock against an assertion that two steps ran fatals under
load with "the web path never installed it", which reads as a
regression. every sibling test in the package uses a long duration and
MaxSteps.

* ci: run the kotlin tests in make test

RouteTransitionTest and the stability poll cover the android settle and
nothing in ci ran them. :sidecar:test needs no android sdk, checked by
running it with ANDROID_HOME pointed at nothing.

* fix(sidecar): measure the stability streak as observed quiet

parameterising pollUntilStable also moved the clock to the start of the
read that opened a run of identical snapshots, so a read's own duration
counted as quiet. the pre-existing caller polls a real uiautomator dump:
at 400ms a read, 750ms of required quiet became 250ms of observed quiet
and the poll settled in two reads instead of four.

the parameters stay, the semantics go back.

* test(sidecar): pin the transition cap by driving it

it asserted 1500 >= 700 + 300, two constants, which can only fail if
someone edits a constant. it now drives awaitSettledTree against a fade
that lands after 700ms and asserts it hands back the settled tree before
the cap. cut the cap to 1000 and it goes red.

* ci: pin buf-setup-action to a commit

it takes a token now, so a floating tag is a token handed to whatever
that tag moves to. note v1 there is a branch, not a tag, so the ref
lookup that resolves it is matching-refs/heads/v1.

* ci: declare least-privilege permissions

none of the three declared any, so each got the repository default.
release.yml and docs.yml already do this. all three only check out,
build, test and upload artifacts.

* ci: fail fast when a server never comes up

the readiness loops fell through silently after 30 tries, so a server
that never started surfaced as an opaque driver failure minutes later.
each now says what did not answer and on which port.

* ci(folio): a missing trace is not a verdict

with no trace the android gate ran its grep against ./trace.jsonl and
reported "never reached AddTransactionScreen, so it never got past
login", which is not what happened. the web and ios branches had the
same misdiagnosis on exit 0.

same class, one line up: the classifier's own failure was swallowed, so
with the evidence reader dead the gate printed a healthy run and exited
0.

* ci(replay-ui): skip a run directory with no trace

the summarise step is if: always(), and under github's bash -eo pipefail
an unmatched glob stays literal, the redirect fails, pipefail carries it
into the assignment and -e kills the step. so a failed fuzz run went red
twice, once for the real reason.

internal/driver/chrome/driver.go

@@ -256,12 +256,7 @@ func (d *Driver) InputText(callerCtx context.Context, text string) error {
 	defer cancel()
 	return chromedp.Run(runCtx,
 		chromedp.ActionFunc(func(ctx context.Context) error {
-			// Select any existing content so InsertText replaces rather than appends.
-			if err := chromedp.Evaluate(`
-				(function() {
-					const el = document.activeElement;
-					if (el && typeof el.select === 'function') el.select();
-				})()`, nil).Do(ctx); err != nil {
+			if err := selectFocusedText(ctx); err != nil {
 				return err
 			}
 			return input.InsertText(text).Do(ctx)
@@ -269,6 +264,28 @@ func (d *Driver) InputText(callerCtx context.Context, text string) error {
 	)
 }
 
+// selectAllScript selects everything in the focused field so the InsertText
+// that follows replaces rather than appends.
+//
+// document.activeElement stops at a shadow boundary: it names the HOST, not the
+// focused node inside. Compose for Web focuses a hidden <input> inside the
+// shadow root it mounts, so the host answer has no select() and the selection
+// never happened - every InputText appended to the last one, and a fuzzer that
+// types into the same field twice built up garbage it could never clear.
+// Descending activeElement through each shadow root finds the real field.
+const selectAllScript = `
+	(function() {
+		let el = document.activeElement;
+		while (el && el.shadowRoot && el.shadowRoot.activeElement) {
+			el = el.shadowRoot.activeElement;
+		}
+		if (el && typeof el.select === 'function') el.select();
+	})()`
+
+func selectFocusedText(ctx context.Context) error {
+	return chromedp.Evaluate(selectAllScript, nil).Do(ctx)
+}
+
 // ReplacesTextOnInput reports that InputText replaces existing content via
 // select-all, so the runner skips its pre-erase.
 func (d *Driver) ReplacesTextOnInput() bool {
@@ -282,11 +299,7 @@ func (d *Driver) EraseText(callerCtx context.Context, _ int) error {
 	defer cancel()
 	return chromedp.Run(runCtx,
 		chromedp.ActionFunc(func(ctx context.Context) error {
-			if err := chromedp.Evaluate(`
-				(function() {
-					const el = document.activeElement;
-					if (el && typeof el.select === 'function') el.select();
-				})()`, nil).Do(ctx); err != nil {
+			if err := selectFocusedText(ctx); err != nil {
 				return err
 			}
 			return input.InsertText("").Do(ctx)
@@ -368,7 +381,11 @@ func (d *Driver) Hierarchy(ctx context.Context) (string, error) {
 	defer cancel()
 	script := `
 (function() {
-  const route = window.location.hash.replace(/^#/, '').split('?')[0] || '/';
+  // Hash first (a HashRouter names the screen there), then the pathname, which
+  // is where a path-routed SPA keeps it. Reporting '/' for every step of a
+  // BrowserRouter app made every screen look like the same screen.
+  const route = window.location.hash.replace(/^#/, '').split('?')[0] ||
+    window.location.pathname || '/';
   // clickable and editable are resolved through the SAME selector sets
   // pkg/spec/src/web-runtime.ts uses, so the goja host (which reads this dump)
   // and the V8 host (which reads the DOM directly) cannot mean different things
@@ -376,6 +393,14 @@ func (d *Driver) Hierarchy(ctx context.Context) (string, error) {
   // root a full-viewport tap target here and nowhere else.
   const NON_TEXT_INPUT_TYPES =
     ['button','submit','checkbox','radio','range','color','file','image','reset'];
+  // The disabled property belongs to real form controls only, so it reads
+  // undefined on the role-based controls the tappable set now covers, and every
+  // one of them looked enabled however plainly it was marked otherwise.
+  // isEnabled in pkg/spec/src/web-runtime.ts answers the same two ways.
+  function isEnabled(el) {
+    if (el.disabled) return false;
+    return el.getAttribute('aria-disabled') !== 'true';
+  }
   function isEditableElement(el) {
     if (el.isContentEditable) return true;
     const tag = el.tagName.toLowerCase();
@@ -383,10 +408,28 @@ func (d *Driver) Hierarchy(ctx context.Context) (string, error) {
     if (tag === 'input') return !NON_TEXT_INPUT_TYPES.includes((el.type || '').toLowerCase());
     return false;
   }
-  const clickableSet = new Set(document.querySelectorAll(
-    'a, button, input, select, textarea, [role="button"], [onclick]'));
-  const editableSet = new Set(Array.from(
-    document.querySelectorAll('input, textarea, [contenteditable]')).filter(isEditableElement));
+  // Shadow roots are part of the page a user sees, so they are part of the page
+  // we enumerate. Compose for Web mounts its canvas AND its accessibility tree
+  // inside a shadow root on the mount element, so a light-DOM-only walk reports
+  // four nodes for a whole app and offers no action on any of them.
+  function deepQuery(sel) {
+    const out = [];
+    const visit = (root) => {
+      for (const el of root.querySelectorAll(sel)) out.push(el);
+      for (const el of root.querySelectorAll('*')) if (el.shadowRoot) visit(el.shadowRoot);
+    };
+    visit(document);
+    return out;
+  }
+  const TAPPABLE_ROLES = [
+    'button', 'link', 'checkbox', 'radio', 'switch', 'tab', 'option',
+    'menuitem', 'menuitemcheckbox', 'menuitemradio', 'treeitem'];
+  const clickableSet = new Set(deepQuery(
+    'a, button, input, select, textarea, ' +
+    TAPPABLE_ROLES.map(role => '[role="' + role + '"]').join(', ') +
+    ', [onclick]'));
+  const editableSet = new Set(deepQuery(
+    'input, textarea, [contenteditable]').filter(isEditableElement));
   function buildTree(el, isRoot) {
     const rect = el.getBoundingClientRect();
     const attrs = {};
@@ -414,6 +457,14 @@ func (d *Driver) Hierarchy(ctx context.Context) (string, error) {
     const isClickable = clickableSet.has(el);
     const isEditable = editableSet.has(el);
     const children = [];
+    // Shadow content first, then light children: the shadow tree is what the
+    // host actually renders, and targetElements in web-runtime.ts walks the same
+    // order, which is the order the two enumerations are compared in.
+    if (el.shadowRoot) {
+      for (const child of el.shadowRoot.children) {
+        children.push(buildTree(child, false));
+      }
+    }
     for (const child of el.children) {
       if (child.tagName === 'HEAD') continue;
       children.push(buildTree(child, false));
@@ -422,7 +473,7 @@ func (d *Driver) Hierarchy(ctx context.Context) (string, error) {
       attributes: attrs,
       children: children,
       clickable: isClickable || null,
-      enabled: (!el.disabled) || null,
+      enabled: isEnabled(el) || null,
       focused: document.activeElement === el || null,
       checked: el.checked || null,
       selected: el.selected || null,
@@ -498,10 +549,138 @@ func (d *Driver) RecentLogs(_ context.Context, since time.Time, minLevel string)
 	return result, nil
 }
 
-func (d *Driver) WaitForIdle(ctx context.Context, _ time.Duration) error {
+// domQuietPeriod is how long the DOM must stop changing before the page counts
+// as settled. Compose for Web syncs its accessibility DOM off the frame loop:
+// measured at ~136 ms behind an InputText on the folio wasm build, so waiting
+// for frames alone (~16 ms each) returns while the app still reports the old
+// text, and the next step types into a field it believes is still empty.
+const domQuietPeriod = 150 * time.Millisecond
+
+// transitionSettlePeriod is how much longer the settle waits for a route
+// transition to finish once the DOM has gone quiet. A canvas app's cross-fade
+// is invisible to a mutation observer: Compose splices the incoming screen's
+// accessibility nodes in when the animation STARTS and removes the outgoing
+// screen's when it ends, and nothing in between touches the DOM, so the tree
+// sits byte-identical (and quiet) with both routes live for the whole
+// animation. Settling on quiet alone returns there, and the next step then
+// verifies a tree that names the screen the app is leaving: on the folio wasm
+// build a submit that landed on Home was recorded as still being on the
+// transaction screen, so a property gated on where the action landed read the
+// wrong route and went vacuous. The wait is bounded so a page that genuinely
+// shows two *Screen ids at rest costs this much per step and no more.
+const transitionSettlePeriod = 800 * time.Millisecond
+
+// settleReturnMargin is what WaitForIdle holds back from the caller's timeout,
+// so returning late by our own doing surfaces as a settled page rather than a
+// context cancellation.
+const settleReturnMargin = 100 * time.Millisecond
+
+// settleScanMargin covers the in-page work the two waits do not themselves
+// account for: liveScreens() walks the document and every shadow root on each
+// 16 ms poll, and the whole script costs one CDP round trip.
+const settleScanMargin = 250 * time.Millisecond
+
+// MinIdleTimeout is the shortest timeout WaitForIdle can be handed and still
+// spend the waits it is built from: the DOM quiet period, the route-transition
+// window that only opens once that quiet period has elapsed, and the second
+// quiet period the transition's own closing mutation starts. A caller that
+// passes less caps the settle below its own budget, and the step then samples a
+// page that is still mid-transition - which is the exact failure the transition
+// wait exists to prevent. internal/runner raises a shorter caller timeout to
+// this value.
+func (d *Driver) MinIdleTimeout() time.Duration {
+	return 2*domQuietPeriod + transitionSettlePeriod +
+		settleScanMargin + settleReturnMargin
+}
+
+func (d *Driver) WaitForIdle(ctx context.Context, timeout time.Duration) error {
 	runCtx, cancel := d.runCtx(ctx)
 	defer cancel()
-	return chromedp.Run(runCtx, chromedp.WaitReady("body", chromedp.ByQuery))
+	// Leave the caller's deadline some room: returning late by our own doing
+	// would surface as a context cancellation instead of a settled page.
+	budget := max(timeout-settleReturnMargin, domQuietPeriod)
+	script := fmt.Sprintf(settleScript,
+		domQuietPeriod.Milliseconds(),
+		budget.Milliseconds(),
+		transitionSettlePeriod.Milliseconds(),
+	)
+	return chromedp.Run(runCtx,
+		chromedp.WaitReady("body", chromedp.ByQuery),
+		chromedp.Evaluate(script, nil, awaitPromise),
+	)
+}
+
+// liveScreensFunction defines liveScreens(), the page-side count of live ids
+// ending in "Screen". More than one is a route transition in flight: the same
+// rule the tree parser applies (Transitional in internal/hierarchy), so the
+// driver and the runner agree on what a settled route looks like. It descends
+// shadow roots because a canvas app keeps its whole accessibility tree inside
+// one.
+const liveScreensFunction = `
+  const liveScreens = () => {
+    let count = 0;
+    const visit = (root) => {
+      count += root.querySelectorAll('[id$="Screen"]').length;
+      for (const element of root.querySelectorAll('*')) {
+        if (element.shadowRoot) visit(element.shadowRoot);
+      }
+    };
+    visit(document);
+    return count;
+  };`
+
+// settleScript resolves once the document has gone quiet for %d ms and is not
+// mid route transition, or after %d ms whatever happens; the transition wait
+// itself gives up after %d ms. Shadow roots get their own observer: a canvas
+// app keeps its whole accessibility tree inside one, and mutations there do not
+// reach an observer on the document.
+//
+// The transition window opens when the quiet period ends, not when the script
+// starts. Anchored at the start it is already spent by the time the check can
+// first run on any page that keeps mutating for longer than the window, so the
+// wait resolves immediately with both routes still live - the mid-transition
+// return this whole wait exists to prevent. Each mutation reopens it, and the
+// budget above bounds the total either way.
+const settleScript = `
+new Promise(resolve => {
+  const quietMillis = %d, budgetMillis = %d, transitionMillis = %d;
+  const observers = [];
+  let transitionDeadline = 0;
+  let timer = null;
+  const finish = () => {
+    clearTimeout(timer);
+    for (const observer of observers) observer.disconnect();
+    resolve();
+  };
+` + liveScreensFunction + `
+  const quiet = () => {
+    if (transitionDeadline === 0) transitionDeadline = Date.now() + transitionMillis;
+    if (liveScreens() > 1 && Date.now() < transitionDeadline) {
+      timer = setTimeout(quiet, 16);
+      return;
+    }
+    finish();
+  };
+  const restart = () => {
+    clearTimeout(timer);
+    transitionDeadline = 0;
+    timer = setTimeout(quiet, quietMillis);
+  };
+  const watch = (root) => {
+    const observer = new MutationObserver(restart);
+    observer.observe(root, {subtree: true, childList: true, attributes: true, characterData: true});
+    observers.push(observer);
+    for (const element of root.querySelectorAll('*')) {
+      if (element.shadowRoot) watch(element.shadowRoot);
+    }
+  };
+  watch(document);
+  setTimeout(finish, budgetMillis);
+  restart();
+})`
+
+func awaitPromise(params *runtime.EvaluateParams) *runtime.EvaluateParams {
+	return params.WithAwaitPromise(true)
 }
 
 func (d *Driver) Health(_ context.Context) (driver.Health, error) {
@@ -596,12 +775,21 @@ func (d *Driver) InstallBundle(ctx context.Context, source []byte) error {
 
 // EvaluateExtractors invokes the bundle-installed extractor table and returns
 // each extractor's JSON-encoded current value keyed by its registration index.
+//
+// The read waits out a route transition first, bounded by
+// transitionSettlePeriod. The hierarchy fetch already re-fetches a transitional
+// tree (fetchSyncedState in internal/runner); without the same rule here the
+// two halves of one step describe different moments, and the spec's own
+// extractors are the half that loses: on the folio wasm build the extractors
+// sampled mid cross-fade and reported the route the app was leaving, so a
+// property gated on where the action landed skipped the only step that action
+// could be judged on.
 func (d *Driver) EvaluateExtractors(ctx context.Context) (map[int]json.RawMessage, error) {
-	const script = `JSON.stringify(window.__sanderlingExtractors__ ? window.__sanderlingExtractors__() : {})`
+	script := fmt.Sprintf(extractorScript, transitionSettlePeriod.Milliseconds())
 	var encoded string
 	runCtx, cancel := d.runCtx(ctx)
 	defer cancel()
-	if err := chromedp.Run(runCtx, chromedp.Evaluate(script, &encoded)); err != nil {
+	if err := chromedp.Run(runCtx, chromedp.Evaluate(script, &encoded, awaitPromise)); err != nil {
 		return nil, fmt.Errorf("evaluate extractors: %w", err)
 	}
 	if encoded == "" || encoded == "{}" {
@@ -612,16 +800,90 @@ func (d *Driver) EvaluateExtractors(ctx context.Context) (map[int]json.RawMessag
 		return nil, fmt.Errorf("decode extractor map: %w", err)
 	}
 	result := make(map[int]json.RawMessage, len(stringMap))
-	for key, value := range stringMap {
+	for key, entry := range stringMap {
 		index, err := strconv.Atoi(key)
 		if err != nil {
 			return nil, fmt.Errorf("non-integer extractor key %q", key)
 		}
-		result[index] = value
+		reading, err := extractorReading(entry)
+		if err != nil {
+			return nil, fmt.Errorf("extractor %d: %w", index, err)
+		}
+		result[index] = reading
 	}
 	return result, nil
 }
 
+// extractorReading unwraps one entry of the page's extractor table. The page
+// wraps every reading in a {"value": ...} envelope (evaluateExtractors in
+// pkg/spec/src/web-runtime.ts) because JSON has no undefined: an absent `value`
+// is the getter returning undefined, and returning it as an empty payload is
+// what makes the goja host record undefined too. Reading it as JSON null would
+// claim the getter returned null, so `x.current === undefined` would answer one
+// thing on native and another on web.
+func extractorReading(entry json.RawMessage) (json.RawMessage, error) {
+	var envelope struct {
+		Value json.RawMessage `json:"value"`
+	}
+	if err := json.Unmarshal(entry, &envelope); err != nil {
+		return nil, fmt.Errorf(
+			"reading %s is not a {\"value\"} envelope; the page and the host are "+
+				"running different bundles: %w", entry, err)
+	}
+	return envelope.Value, nil
+}
+
+// SetLastAction installs the previous step's action as state.lastAction inside
+// the page runtime. The page cannot derive it: only the runner knows which
+// action was actually applied. Without this call every web state.lastAction is
+// null, so a property gated on what the last action did is vacuously true and
+// reports a green run while checking nothing.
+//
+// The call is deliberately unguarded. A `setter && setter(...)` form evaluates
+// to undefined on a page whose runtime does not define the setter, and chromedp
+// reports that as success, so "the page cannot accept lastAction" would be
+// indistinguishable from "installed". That page is reachable: a run resolving
+// its web runtime from an older published @sanderling/spec would silently no-op
+// every step. Unguarded, the missing global throws and the run fails loudly.
+func (d *Driver) SetLastAction(ctx context.Context, encoded json.RawMessage) error {
+	payload := strings.TrimSpace(string(encoded))
+	if payload == "" {
+		payload = "null"
+	}
+	script := fmt.Sprintf(`window.__sanderlingSetLastAction__(%s)`, payload)
+	runCtx, cancel := d.runCtx(ctx)
+	defer cancel()
+	if err := chromedp.Run(runCtx, chromedp.Evaluate(script, nil)); err != nil {
+		return fmt.Errorf("set last action: %w", err)
+	}
+	return nil
+}
+
+// extractorScript resolves the extractor table once the page is not mid route
+// transition, giving up on that wait after %d ms.
+//
+// A missing table rejects rather than reporting {}, for the same reason
+// SetLastAction no longer guards its call: an empty override map is what a
+// spec with no extractors returns, so the guarded form made "this page has no
+// sanderling runtime" read as a normal step whose properties then ran on
+// goja's dump-derived values instead of the page's.
+const extractorScript = `
+new Promise((resolve, reject) => {
+  const deadline = Date.now() + %d;` + liveScreensFunction + `
+  const read = () => {
+    if (liveScreens() > 1 && Date.now() < deadline) {
+      setTimeout(read, 16);
+      return;
+    }
+    if (typeof window.__sanderlingExtractors__ !== "function") {
+      reject(new Error("__sanderlingExtractors__ is not installed in the page"));
+      return;
+    }
+    resolve(JSON.stringify(window.__sanderlingExtractors__()));
+  };
+  read();
+})`
+
 // NextActionFromV8 invokes the bundle-installed action generator and returns
 // the resulting Action JSON. Returns an empty json.RawMessage when the
 // generator declines to act this tick.