Spec #137: per-Series poll failure state, completion hint, and outbound owner notification (#174)

Implements spec #137 (spec 4 of 4 from wayfinder map #114).

Closes #137.

Tickets: #164, #165, #166, #167, #168, #169, #170, #171, #172, #173 — all closed, landed on this branch.

## Summary
- #164/#168: sixth outcome word `not_found`; per-Site completed marker predicate.
- #165/#169: `poll_failures` row is the failure state; the pass remembers a Site-reported completion.
- #166/#171: two new admin filters (`failing`, `unverified`); outbound owner notification + stall condition.
- #167/#170: a failure names itself on the Series page; the completion hint reaches the owner and decides nothing.
- #172: the other three fault conditions (no-browser-route, sidecar-down, adapter-broken) feeding the notifier.
- #173: the landing verdict line shares the same `latest.FaultsFrom` judgement the notifier uses, so the page and the push cannot disagree.

`cd backend && go test ./...` green on the merged branch (8 packages).

Reviewed-on: #174
Co-authored-by: Sulthan Zaki <sultankiki05@gmail.com>
Co-committed-by: Sulthan Zaki <sultankiki05@gmail.com>

backend/internal/latest/faults.go

@@ -0,0 +1,210 @@
+package latest
+
+import (
+	"context"
+	"fmt"
+	"time"
+
+	"bookmarkmanager/backend/internal/store"
+)
+
+// ConditionStall is the owner-notice machine word for a Lane that owed Polls,
+// made none, and has nothing to say for it. The word is the message's footer
+// and its suppression key; it is wire-stable. #172 declares the other three
+// words (no-browser-route, sidecar-down, adapter-broken); this ticket
+// declares only the stall.
+const ConditionStall = "stall"
+// ConditionNoBrowserRoute is the owner-notice machine word for a Site whose
+// challenge refuses for longer than the owner window with no browser route
+// to clear it — the 403-with-interstitial the reader maps to
+// errChallengeHeld (read.go), which plain TLS cannot clear. The word is the
+// message's footer and its suppression key; it is wire-stable.
+const ConditionNoBrowserRoute = "no-browser-route"
+
+// ConditionSidecarDown is the owner-notice machine word for a browser
+// sidecar no Lane has reached for longer than the owner window: every
+// browser-backed Lane's latest pass is a sidecar skip. The word is the
+// message's footer and its suppression key; it is wire-stable, and its
+// suppression row holds the empty Site (AC4).
+const ConditionSidecarDown = "sidecar-down"
+
+// ConditionAdapterBroken is the owner-notice machine word for a Site whose
+// adapter stopped finding chapters: more than half of its Series hold an
+// old no-chapter failure row. The word is the message's footer and its
+// suppression key; it is wire-stable.
+const ConditionAdapterBroken = "adapter-broken"
+
+// OwnerWindow is the class-level staleness boundary every owner-notice
+// condition measures against — the same twelve hours the Lanes page's
+// "not checked in 12h" filter uses (internal/web/admin.go). Declared here
+// once so #172's three conditions and the admin filters share one figure.
+const OwnerWindow = 12 * time.Hour
+
+// Fault is one condition the owner is told about, judged from durable rows
+// alone. Site is "" for a fault that is not one Site's.
+type Fault struct {
+	Condition string // one of the Condition* words
+	Site      string
+	Since     int64 // unix ms the episode began; the message's age
+}
+
+// FaultInput is everything the judgement reads. A struct so #172's three
+// conditions can add inputs without changing either caller.
+type FaultInput struct {
+	Passes []store.LanePass
+	// RefusingSince is, per Site, the unix ms when that Site's current
+	// unbroken run of refusing passes began, or absent when its latest pass
+	// did not refuse. Its zero value is an empty map, which contributes no
+	// fault.
+	RefusingSince map[string]int64
+
+	// SidecarOK is, per browser-backed Site, the unix ms of that Site's most
+	// recent pass that actually reached the sidecar. Zero when the pass log
+	// holds none — an asleep Lane never reached it and never counts as
+	// evidence either way. Its zero value is an empty map.
+	SidecarOK map[string]int64
+
+	// NoChapterShare is, per Site, the share of that Site's Series holding a
+	// no-chapter failure row older than the owner window. Its zero value is
+	// an empty map, which contributes no fault.
+	NoChapterShare map[string]float64
+}
+
+// FaultsFrom judges the owner-notice conditions from durable rows alone, so
+// the poller and the landing page cannot disagree about what a fault is.
+//
+// A Lane stalls when its latest pass shows due > 0, none checked, no skip
+// value and no refusal — exactly the row the mid-loop browser loss writes
+// (see the comment at the outcomeUnreachable return in runLanePass), so a
+// Lane that owed Polls, made none, and has nothing to say for it is a fault.
+// The three #172 conditions share the same OwnerWindow boundary and the same
+// fail-open shape: an input's absence contributes no fault, never a false
+// one.
+//
+//   - no-browser-route: a Site whose refusing run began before the window
+//     and that has no browser route to clear the challenge (AC2). Both
+//     refusal shapes count — the gate's skip='refusing' rows and the loop's
+//     refused>0 rows (the twice-refused break writes skip="") — so the run
+//     stays unbroken across them, and one healthy pass ends it.
+//   - sidecar-down: every browser-backed Site's latest pass is a sidecar
+//     skip — SkipSidecarDown or SkipNoFetcher, the two early returns that
+//     record a skip value — and each Site's most recent sidecar-reaching
+//     pass is older than the window (AC4). The skip clause is what keeps
+//     SkipAsleep out: a Lane under both wake thresholds is the commonest
+//     healthy state, never reached the sidecar, and would otherwise age into
+//     a false alarm. Emitted once, with Site "" (AC4's one row per episode).
+//   - adapter-broken: more than half of one Site's Series hold a no-chapter
+//     failure row older than the window (AC6). Strictly above half: the
+//     filter is the tool, and one Site change makes hundreds of rows, so a
+//     single failing Series never fires (AC7). The episode's age is the
+//     window — the old rows prove the episode is at least that old.
+func FaultsFrom(in FaultInput, now time.Time) []Fault {
+	var faults []Fault
+	for _, p := range in.Passes {
+		if p.Due > 0 && p.Checked == 0 && p.Skip == "" && p.Refused == 0 {
+			faults = append(faults, Fault{Condition: ConditionStall, Site: p.Site, Since: p.RanAt})
+		}
+	}
+	cutoff := now.Add(-OwnerWindow).UnixMilli()
+	for site, since := range in.RefusingSince {
+		if since < cutoff && !isBrowserSite(site) {
+			faults = append(faults, Fault{Condition: ConditionNoBrowserRoute, Site: site, Since: since})
+		}
+	}
+	if since, down := sidecarDownSince(in.Passes, in.SidecarOK, cutoff); down {
+		faults = append(faults, Fault{Condition: ConditionSidecarDown, Site: "", Since: since})
+	}
+	for site, share := range in.NoChapterShare {
+		if share > 0.5 {
+			faults = append(faults, Fault{Condition: ConditionAdapterBroken, Site: site, Since: now.Add(-OwnerWindow).UnixMilli()})
+		}
+	}
+	return faults
+}
+
+// sidecarDownSince reports whether no browser Lane has reached the sidecar
+// for longer than the owner window and, when it has, the last moment any
+// Lane reached it. The skip clause — every browser-backed Site's latest pass
+// must be SkipSidecarDown or SkipNoFetcher — keeps SkipAsleep out (see
+// FaultsFrom). A Site with no pass row at all is not judged down either: a
+// fresh database is not a dead sidecar.
+func sidecarDownSince(passes []store.LanePass, ok map[string]int64, cutoff int64) (since int64, down bool) {
+	latest := make(map[string]store.LanePass, len(passes))
+	for _, p := range passes {
+		latest[p.Site] = p
+	}
+	for _, site := range browserBackedSites() {
+		p, found := latest[site]
+		if !found || (p.Skip != SkipSidecarDown && p.Skip != SkipNoFetcher) {
+			return 0, false
+		}
+		reached := ok[site]
+		if reached > 0 && reached >= cutoff {
+			return 0, false
+		}
+		if reached > since {
+			since = reached
+		}
+	}
+	// No Lane's retained pass log shows a sidecar reach: the honest age is
+	// the window itself — "at least twelve hours" — not the epoch, which
+	// humanAge would render as tens of thousands of days.
+	if since == 0 {
+		since = cutoff
+	}
+	return since, true
+}
+
+// Notifier delivers one owner notice. The poller neither retries nor queues:
+// an error is logged and the suppression row left unwritten, so the next pass
+// tries again while the condition holds.
+type Notifier interface {
+	Notify(ctx context.Context, f Fault, sentence, href string) error
+}
+
+// ownerNoticeConditions is every condition this package judges, for the
+// clear loop in recordPass: a condition absent from a pass's fault list
+// forgets its episode, so the next occurrence sends again. #172 extends the
+// list when it adds its conditions.
+var ownerNoticeConditions = []string{ConditionStall, ConditionNoBrowserRoute, ConditionSidecarDown, ConditionAdapterBroken}
+
+// noticeFor renders one fault's message: the description sentence — condition,
+// age, repair — and the deep link the embed's title points at. Each condition
+// provides its own wording; the stall is the only one today (issue #171).
+func noticeFor(f Fault, row store.LanePass, now time.Time) (sentence, href string) {
+	switch f.Condition {
+	case ConditionStall:
+		return fmt.Sprintf(
+			"%s owed %d Polls and made none — %s; check the Lane's browser sidecar and the Site's challenge state",
+			f.Site, row.Due, humanAge(now.Sub(time.UnixMilli(f.Since)))), "/admin/lanes"
+	case ConditionNoBrowserRoute:
+		return fmt.Sprintf(
+			"%s has refused for %s with no browser route — the challenge does not clear on plain TLS; redeploy or add a browser route",
+			f.Site, humanAge(now.Sub(time.UnixMilli(f.Since)))), "/admin/lanes"
+	case ConditionSidecarDown:
+		return fmt.Sprintf(
+			"no browser Lane has reached the sidecar for %s — the browser sidecar is down; start or repair the browser machine",
+			humanAge(now.Sub(time.UnixMilli(f.Since)))), "/admin/lanes"
+	case ConditionAdapterBroken:
+		return fmt.Sprintf(
+			"more than half of %s's Series have failed no-chapter reads for at least %s — the Site's layout changed and the adapter is broken",
+			f.Site, humanAge(now.Sub(time.UnixMilli(f.Since)))), "/admin/lanes"
+	}
+	return "", ""
+}
+
+// humanAge renders a duration the way an owner reads it in a message: minutes
+// under an hour, then hours, then days; a stall that was just born reads
+// "just now".
+func humanAge(d time.Duration) string {
+	switch {
+	case d < time.Minute:
+		return "just now"
+	case d < time.Hour:
+		return fmt.Sprintf("%dm", int(d.Minutes()))
+	case d < 24*time.Hour:
+		return fmt.Sprintf("%dh", int(d.Hours()))
+	default:
+		return fmt.Sprintf("%dd", int(d.Hours()/24))
+	}
+}

backend/internal/latest/poller.go

@@ -46,7 +46,10 @@ type Poller struct {
 	// CoverBytesFetch is optional; it handles plain-TLS sources through the
 	// same failure-isolated prefetch path.
 	CoverBytesFetch CoverBytesFetcher
-	Now             func() time.Time // injected so tests can freeze it
+	// Notify delivers owner notices. Nil disables the whole path (issue #171):
+	// the poller is not the place a missing webhook becomes an error.
+	Notify Notifier
+	Now    func() time.Time // injected so tests can freeze it
 	// eligibleCount reports how many of a Site's Series are eligible for
 	// polling, defaulting to Store.EligibleSeriesCount. Injected so tests can
 	// fail the count alone: the eligible query shares the due query's tables,
@@ -273,7 +276,9 @@ const (
 // (issue #141). The classification the read already makes is counted, never a
 // second taxonomy: refused is the Site holding a challenge, unreachable the
 // browser interrupting, noChapter a 200 with real HTML but no chapter links,
-// unfetchable the host pin or a missing fetcher, and errors everything else.
+// unfetchable the host pin or a missing fetcher, notFound a 4xx other than
+// the 403 refusal — the Site answered with a client status — and errors
+// everything else.
 type readOutcome int
 
 const (
@@ -283,14 +288,33 @@ const (
 	outcomeNoChapter
 	outcomeUnfetchable
 	outcomeError
+	outcomeNotFound
 )
+// word returns the wire spelling this outcome stores in poll_failures — the
+// same strings the pass log's columns use (C1, issue #164). Success, refusal
+// and browser loss return "" so recordFailure's "no statement" case is one
+// return: a challenge or a lost sidecar is no evidence about any particular
+// Series (ADR-0016).
+func (o readOutcome) word() string {
+	switch o {
+	case outcomeNotFound:
+		return "not_found"
+	case outcomeNoChapter:
+		return "no_chapter"
+	case outcomeUnfetchable:
+		return "unfetchable"
+	case outcomeError:
+		return "errors"
+	}
+	return ""
+}
 
-// outcomeCounts are the five named outcome counts of one pass. A success
-// count is derived, never stored: checked minus the four, with unreachable
-// excluded because the sidecar-loss path returns before the checked counter
-// increments (issue #141).
+// outcomeCounts are the six named outcome counts of one pass. A success
+// count is derived, never stored: checked minus the five named failures,
+// with unreachable excluded because the sidecar-loss path returns before the
+// checked counter increments (issue #141).
 type outcomeCounts struct {
-	refused, unreachable, noChapter, unfetchable, errors int
+	refused, unreachable, noChapter, unfetchable, errors, notFound int
 }
 
 func (c *outcomeCounts) add(o readOutcome) {
@@ -303,6 +327,8 @@ func (c *outcomeCounts) add(o readOutcome) {
 		c.noChapter++
 	case outcomeUnfetchable:
 		c.unfetchable++
+	case outcomeNotFound:
+		c.notFound++
 	case outcomeError:
 		c.errors++
 	}
@@ -334,7 +360,7 @@ func (p *Poller) runLanePass(ctx context.Context, name string, paced bool) time.
 	// carries the previous pass's forward inside recordPass.
 	fig := passFigures{}
 	rec := passRecord{site: name, ranAt: now.UnixMilli()}
-	defer func() { p.recordPass(rec, fig) }()
+	defer func() { p.recordPass(ctx, rec, fig) }()
 
 	// One Lane row read at the top of a pass, serving two gates (issue #139).
 	// Both stamps outlive our process, so the gates read the durable row
@@ -451,6 +477,7 @@ func (p *Poller) runLanePass(ctx context.Context, name string, paced bool) time.
 			}
 		}
 		outcome := p.checkOne(ctx, sr)
+		p.recordFailure(sr, outcome)
 		if outcome == outcomeUnreachable {
 			// The mid-loop browser loss writes an empty skip on purpose: the
 			// pass returns before the checked counter increments, so its row
@@ -503,8 +530,9 @@ type passFigures struct {
 // pass's due, gap, clamped and checked forward rather than stating zeroes it
 // did not measure; the skip column says why it declined, so the zeroes that
 // remain (due-query, no-fetcher) read as explanations rather than
-// measurements.
-func (p *Poller) recordPass(rec passRecord, fig passFigures) {
+// measurements. Once the row is durable, the owner-notice judgement runs
+// beside it (issue #171).
+func (p *Poller) recordPass(ctx context.Context, rec passRecord, fig passFigures) {
 	row := store.LanePass{
 		Site:        rec.site,
 		RanAt:       rec.ranAt,
@@ -517,6 +545,7 @@ func (p *Poller) recordPass(rec passRecord, fig passFigures) {
 		Unreachable: rec.counts.unreachable,
 		NoChapter:   rec.counts.noChapter,
 		Unfetchable: rec.counts.unfetchable,
+		NotFound:    rec.counts.notFound,
 		Errors:      rec.counts.errors,
 	}
 	if row.GapMS == 0 {
@@ -532,7 +561,111 @@ func (p *Poller) recordPass(rec passRecord, fig passFigures) {
 	}
 	if err := p.Store.RecordLanePass(row, rec.ranAt-lanePassRetention.Milliseconds()); err != nil {
 		log.Printf("latest poll %s: record lane pass: %v", rec.site, err)
+		return
 	}
+	p.ownerNotices(ctx, row)
+}
+
+// ownerNotices judges the owner-notice conditions for the pass just recorded
+// and fires (issue #171). It sits in recordPass because that deferred call is
+// the one place every return path passes through: three of the four
+// conditions occur on early returns and the success path can never see them.
+// The judgement reads the whole pass log plus three derived reads — the
+// other Lanes' latest passes, each Site's refusing-run start, its last
+// sidecar-reaching pass, and its no-chapter share — so one pass judges every
+// condition (issue #172). Per fault: NoticeSent → send → MarkNoticeSent, so
+// a fault lasting a month sends one message, not one per pass; a condition
+// absent from this pass's fault list forgets its episode, so the next
+// occurrence sends again. Everything here is best-effort: a failed send, a
+// failed store read and a failed notice write are all logged and never
+// change the pass's outcome counts or its return value. The clear runs even
+// when Notify is nil, so a deployment that turns the webhook off does not
+// leave stale rows that suppress the first real notice after it is turned
+// back on.
+func (p *Poller) ownerNotices(ctx context.Context, row store.LanePass) {
+	now := p.Now()
+	in := FaultInput{Passes: []store.LanePass{row}}
+	// Each read fails independently: a failure logs and contributes no fault,
+	// never a false one.
+	if passes, err := p.Store.LatestLanePasses(); err != nil {
+		log.Printf("latest poll %s: latest lane passes: %v", row.Site, err)
+	} else {
+		in.Passes = passes
+	}
+	if since, err := p.Store.RefusingSince(now.UnixMilli()); err != nil {
+		log.Printf("latest poll %s: refusing since: %v", row.Site, err)
+	} else {
+		in.RefusingSince = since
+	}
+	if ok, err := p.Store.SidecarOK(browserBackedSites()); err != nil {
+		log.Printf("latest poll %s: sidecar ok: %v", row.Site, err)
+	} else {
+		in.SidecarOK = ok
+	}
+	if share, err := p.Store.NoChapterShare(now.Add(-OwnerWindow).UnixMilli()); err != nil {
+		log.Printf("latest poll %s: no-chapter share: %v", row.Site, err)
+	} else {
+		in.NoChapterShare = share
+	}
+	faults := FaultsFrom(in, now)
+	bySite := make(map[string]store.LanePass, len(in.Passes))
+	for _, pass := range in.Passes {
+		bySite[pass.Site] = pass
+	}
+	for _, f := range faults {
+		if p.Notify == nil {
+			continue
+		}
+		sent, err := p.Store.NoticeSent(f.Condition, f.Site)
+		if err != nil {
+			log.Printf("latest poll %s: notice sent: %v", row.Site, err)
+			continue
+		}
+		if sent {
+			continue
+		}
+		// The fault's own Site's pass renders its sentence — a stall judged
+		// from another Lane's pass must not quote this pass's figures.
+		pass, ok := bySite[f.Site]
+		if !ok {
+			pass = row
+		}
+		sentence, href := noticeFor(f, pass, now)
+		if err := p.Notify.Notify(ctx, f, sentence, href); err != nil {
+			// The stamp stays unset: no queue, no backoff — the condition is
+			// durable, so the next pass tries again while it holds.
+			log.Printf("latest poll %s: owner notice %s: %v", row.Site, f.Condition, err)
+			continue
+		}
+		if err := p.Store.MarkNoticeSent(f.Condition, f.Site, now.UnixMilli()); err != nil {
+			log.Printf("latest poll %s: mark notice sent: %v", row.Site, err)
+		}
+	}
+	for _, cond := range ownerNoticeConditions {
+		if !hasFault(faults, cond, row.Site) {
+			if err := p.Store.ClearNotice(cond, row.Site); err != nil {
+				log.Printf("latest poll %s: clear owner notice: %v", row.Site, err)
+			}
+		}
+	}
+	// sidecar-down suppresses under the empty Site — one row across all
+	// browser Lanes (AC4) — so clear that row when it is absent from this
+	// pass's fault list, and a lifted sidecar fires again when it returns.
+	if !hasFault(faults, ConditionSidecarDown, "") {
+		if err := p.Store.ClearNotice(ConditionSidecarDown, ""); err != nil {
+			log.Printf("latest poll %s: clear owner notice: %v", row.Site, err)
+		}
+	}
+}
+
+// hasFault reports whether faults hold the given condition for the site.
+func hasFault(faults []Fault, condition, site string) bool {
+	for _, f := range faults {
+		if f.Condition == condition && f.Site == site {
+			return true
+		}
+	}
+	return false
 }
 
 // countEligible routes the eligible count through the test seam when one is
@@ -607,13 +740,35 @@ func maxSeriesWait(due []store.Series, now time.Time, rest time.Duration) time.D
 	}
 	return oldest
 }
+// recordFailure keeps one Series' failure row in step with its read
+// (ADR-0016): a failure word is upserted, a successful read deletes the row,
+// and refused or unreachable issue no statement at all. Called for every
+// outcome from the pass loop, so the four failure words and the success path
+// share one write point, and a forced Poll that reads the page clears through
+// the ordinary success path — no branch of its own. Log a store failure and
+// carry on: this is best-effort, and no single bad Series may stall a Lane.
+func (p *Poller) recordFailure(sr store.Series, outcome readOutcome) {
+	if outcome == outcomeSuccess {
+		if err := p.Store.ClearSeriesFailure(sr.Site, sr.SeriesID); err != nil {
+			log.Printf("latest poll %q: clear failure: %v", sr.Key(), err)
+		}
+		return
+	}
+	word := outcome.word()
+	if word == "" {
+		return
+	}
+	if err := p.Store.RecordSeriesFailure(sr.Site, sr.SeriesID, word, p.Now().UnixMilli()); err != nil {
+		log.Printf("latest poll %q: record failure: %v", sr.Key(), err)
+	}
+}
 
 // checkOne re-checks one series. Every failure path here is "log and move on":
 // the poller is a best-effort enhancement, and no single bad series may stall a
 // Lane or take down the process. The returned outcome classifies the read for
 // the pass row (issue #141), so the Lane can count a refusal, a lost browser,
-// a chapter-less page, an unfetchable address or a transport error without
-// re-deriving the taxonomy.
+// a chapter-less page, an unfetchable address, a missing page or a transport
+// error without re-deriving the taxonomy.
 func (p *Poller) checkOne(ctx context.Context, sr store.Series) (outcome readOutcome) {
 	defer func() {
 		if r := recover(); r != nil {
@@ -657,6 +812,9 @@ func (p *Poller) checkOne(ctx context.Context, sr store.Series) (outcome readOut
 		if errors.Is(err, errBrowserInterrupted) {
 			return outcomeUnreachable
 		}
+		if errors.Is(err, errNotFound) {
+			return outcomeNotFound
+		}
 		return outcomeError
 	}
 	// A legacy cover source is healed independently of the page read.
@@ -669,6 +827,25 @@ func (p *Poller) checkOne(ctx context.Context, sr store.Series) (outcome readOut
 	} else {
 		p.fillBlankCover(ctx, sr, facts.Cover)
 	}
+
+	// Learned from the successful read: the write sits after the error switch
+	// (a refused, unreachable or errored read reaches nothing) and before the
+	// returns below — a completed page whose chapter number did not change
+	// still has to write. The transition is zero-versus-nonzero, not the
+	// stamp's value: a Series still completed keeps its original stamp, so the
+	// age #170 prints is "since the Site first said so"; one that stopped
+	// being completed is zeroed.
+	stamp := int64(0)
+	if facts.SiteCompleted {
+		stamp = p.Now().UnixMilli()
+	}
+	if (sr.SiteCompletedAt == 0) != (stamp == 0) {
+		if err := p.Store.SetSiteCompletedAt(sr.Site, sr.SeriesID, stamp); err != nil {
+			// Best-effort, like every poller write: never change the outcome
+			// word the pass counts.
+			log.Printf("latest poll %q: set site completed: %v", sr.Key(), err)
+		}
+	}
 	if !facts.HasLatest {
 		// Most likely a challenge page or a layout change. Either way the row is
 		// already stamped, so this waits out a rest instead of hot-looping.

backend/internal/latest/read.go

@@ -6,15 +6,19 @@ import (
 	"fmt"
 )
 
-// seriesRead carries the two facts the poll and the acquirer both extract
-// from a series page. Persistence, stamps and scheduling stay with the
-// callers, so the policies that keep the two flows distinct (stamp order,
-// rests) are not swallowed by the module.
+// seriesRead carries the facts the poll and the acquirer both extract from a
+// series page. Persistence, stamps and scheduling stay with the callers, so
+// the policies that keep the two flows distinct (stamp order, rests) are not
+// swallowed by the module.
 type seriesRead struct {
 	Latest    latestChapter
 	HasLatest bool
 	Cover     string
 	HasCover  bool
+	// SiteCompleted is whether the Site's own completed value was on the page.
+	// A challenge body and a redesign both read false — an absent hint, never
+	// a claim (issue #168).
+	SiteCompleted bool
 	// BodyLen is the fetched body's length, surfaced because the no-chapter
 	// log uses it to tell a markup change from a body the size cap cut short.
 	BodyLen int
@@ -25,15 +29,18 @@ type seriesRead struct {
 // errChallengeHeld (browser.go) is the outcome of a Site that answered with
 // its interstitial — status 403 (cf-mitigated) or a challenge page body — and
 // is how a Lane tells a refusal from an ordinary failure (issue #100).
+// errNotFound marks any other 4xx: the page is gone — a fact the owner can act
+// on — as distinct from a Site or database that is merely unwell (issue #164).
 var (
 	errNotFetchable = errors.New("series url not fetchable")
 	errNoFetcher    = errors.New("no fetcher for site")
+	errNotFound     = errors.New("series page not found")
 )
 
 // readSeriesPage performs the series-page read the poll and the acquirer have
 // in common: gate the address, choose the route, fetch the page, extract the
-// Latest Chapter and the Cover address. It persists nothing and stamps
-// nothing.
+// Latest Chapter, the Cover address and the Site's completed value. It
+// persists nothing and stamps nothing.
 //
 // series_url arrives in a client-supplied PUT body (PUT /bookmarks/{key}
 // accepts any string), so the gate is not an optimisation against burning a
@@ -59,6 +66,9 @@ func readSeriesPage(ctx context.Context, site, seriesURL string, browser, tls Fe
 		return seriesRead{}, fmt.Errorf("%w: fetch %s: status %d", errChallengeHeld, seriesURL, status)
 	}
 	if status != 200 {
+		if status >= 400 && status < 500 {
+			return seriesRead{}, fmt.Errorf("%w: fetch %s: status %d", errNotFound, seriesURL, status)
+		}
 		return seriesRead{}, fmt.Errorf("fetch %s: status %d", seriesURL, status)
 	}
 	if isInterstitial(body) {
@@ -69,5 +79,12 @@ func readSeriesPage(ctx context.Context, site, seriesURL string, browser, tls Fe
 	}
 	latest, hasLatest := latestChapterFrom(site, seriesURL, body)
 	cover, hasCover := coverFrom(site, seriesURL, body)
-	return seriesRead{Latest: latest, HasLatest: hasLatest, Cover: cover, HasCover: hasCover, BodyLen: len(body)}, nil
+	return seriesRead{
+		Latest:        latest,
+		HasLatest:     hasLatest,
+		Cover:         cover,
+		HasCover:      hasCover,
+		SiteCompleted: siteCompletedFrom(site, seriesURL, body),
+		BodyLen:       len(body),
+	}, nil
 }

backend/internal/latest/sites.go

@@ -22,10 +22,10 @@ type latestChapter struct {
 
 // site answers the fixed questions every series-page read asks of its Site
 // (ADR-0009): the host its addresses must carry, how to find the Latest
-// Chapter and the Cover address in a body, and — for a Site behind a
-// JavaScript challenge — how to read its payload from a cleared tab. One
-// entry describes everything about one Site, and nowhere else gets to compare
-// the site string.
+// Chapter and the Cover address in a body, whether the Site calls the work
+// completed, and — for a Site behind a JavaScript challenge — how to read its
+// payload from a cleared tab. One entry describes everything about one Site,
+// and nowhere else gets to compare the site string.
 type site struct {
 	// Host is the exact hostname a series_url for this Site must carry.
 	Host string
@@ -33,6 +33,10 @@ type site struct {
 	LatestChapter func(seriesURL, body string) (latestChapter, bool)
 	// Cover finds the Cover address in a fetched body.
 	Cover func(seriesURL, body string) (string, bool)
+	// Completed reports whether this body carries the Site's own completed
+	// value. False for a body that carries any other value, and false for a
+	// failed extraction — never an error and never a third state.
+	Completed func(seriesURL, body string) bool
 	// Rest is how long a Series of this Site rests between Polls.
 	Rest time.Duration
 	// Gap is the Lane's strictest pace: at least one second must pass between
@@ -299,34 +303,42 @@ func kaganeCoverURL(body string) string {
 	return ""
 }
 
-func comixCoverURL(seriesURL, body string) string {
+// comixDetailQuery returns the ["manga","detail","<id>"] query entry of
+// comix's initial-data JSON, or nil. The cover and completed reads share the
+// scoped lookup so a "recommended" strip entry can never contribute either
+// answer.
+func comixDetailQuery(seriesURL, body string) json.RawMessage {
 	id, ok := comixSeriesID(seriesURL)
 	if !ok {
-		return ""
+		return nil
 	}
 	data := comixInitialDataRe.FindStringSubmatch(body)
 	if data == nil {
-		return ""
+		return nil
 	}
 	var state struct {
 		Queries map[string]json.RawMessage `json:"queries"`
 	}
 	if err := json.Unmarshal([]byte(data[1]), &state); err != nil {
+		return nil
+	}
+	return state.Queries[`["manga","detail","`+id+`"]`]
+}
+
+func comixCoverURL(seriesURL, body string) string {
+	detail := comixDetailQuery(seriesURL, body)
+	if len(detail) == 0 {
 		return ""
 	}
-	raw := state.Queries[`["manga","detail","`+id+`"]`]
-	if len(raw) == 0 {
-		return ""
-	}
-	var detail struct {
+	var entry struct {
 		Poster struct {
 			Medium string `json:"medium"`
 		} `json:"poster"`
 	}
-	if err := json.Unmarshal(raw, &detail); err != nil {
+	if err := json.Unmarshal(detail, &entry); err != nil {
 		return ""
 	}
-	return publishedCoverURL(detail.Poster.Medium)
+	return publishedCoverURL(entry.Poster.Medium)
 }
 
 // ogImageCover reads the og:image metadata shared by asura, demonic and
@@ -360,6 +372,87 @@ func coverFrom(site, seriesURL, body string) (string, bool) {
 	return "", false
 }
 
+// asuraStatusRe matches the status value inside the escaped astro-island
+// props blob, in both the &quot; form the served document carries and the "
+// form a decoded copy would. "completed" is the only true value: "dropped"
+// is scanlation editorial (the work itself continues elsewhere) and hiatus is
+// its own value.
+var asuraStatusRe = regexp.MustCompile(`(?:&quot;|")status(?:&quot;|"):\[0,(?:&quot;|")completed(?:&quot;|")\]`)
+
+func asuraCompleted(_, body string) bool {
+	return asuraStatusRe.MatchString(body)
+}
+
+// demonicStatusRe matches the info block's status pair: a Status label <li>
+// immediately followed by the value <li>. The site's whole status vocabulary
+// is {Ongoing, Completed} (its advanced-search status filter), so the literal
+// Completed value is the entire signal.
+var demonicStatusRe = regexp.MustCompile(`<li[^>]*>\s*Status\s*</li>\s*<li[^>]*>\s*Completed\s*</li>`)
+
+func demonicCompleted(_, body string) bool {
+	return demonicStatusRe.MatchString(body)
+}
+
+// comixCompleted reads "status" from the scoped detail entry only;
+// "finished" is the completed value, and on_hiatus and discontinued are
+// distinct values.
+func comixCompleted(seriesURL, body string) bool {
+	detail := comixDetailQuery(seriesURL, body)
+	if len(detail) == 0 {
+		return false
+	}
+	var entry struct {
+		Status string `json:"status"`
+	}
+	if err := json.Unmarshal(detail, &entry); err != nil {
+		return false
+	}
+	return entry.Status == "finished"
+}
+
+// kaganeCompleted reads publication_status only: upload_status is the
+// release's state, and the two provably diverge ('Cause Calypso Can,
+// 2026-08-19: publication Ongoing, upload Hiatus), so a Completed upload
+// must never read as a Completed work.
+func kaganeCompleted(_, body string) bool {
+	var series struct {
+		PublicationStatus string `json:"publication_status"`
+	}
+	if err := json.Unmarshal([]byte(body), &series); err != nil {
+		return false
+	}
+	return series.PublicationStatus == "Completed"
+}
+
+// novelfullStatusRe matches the info panel's status link. The page's whole
+// status vocabulary is {Ongoing, Completed} (the "OnGoing" spelling aliases
+// "Ongoing" on the taxonomy), so the Completed href is the signal.
+var novelfullStatusRe = regexp.MustCompile(`href="/status/Completed"`)
+
+func novelfullCompleted(_, body string) bool {
+	return novelfullStatusRe.MatchString(body)
+}
+
+// lnwCompleted matches creativeWorkStatus in the head's JSON-LD block. The
+// whole body is scanned and the comment marker is not required, unlike
+// lnwLatestChapter: the status block sits ahead of the visitor-writable
+// thread, and hiatus maps to a distinct PotentialActionStatus value.
+var lnwStatusRe = regexp.MustCompile(`"creativeWorkStatus"\s*:\s*"https://schema\.org/CompletedActionStatus"`)
+
+func lnwCompleted(_, body string) bool {
+	return lnwStatusRe.MatchString(body)
+}
+
+// siteCompletedFrom reports whether the Site calls this work completed, via
+// the Site's registry entry. False for an unknown site, a challenge body and
+// a redesign alike: an absent hint, never a claim.
+func siteCompletedFrom(site, seriesURL, body string) bool {
+	if fn := sites[site].Completed; fn != nil {
+		return fn(seriesURL, body)
+	}
+	return false
+}
+
 // metaContent returns the content of the first <meta> whose attrName is
 // attrValue. It keeps scanning after an empty match so a later published cover
 // is not hidden by an empty tag.
@@ -449,6 +542,7 @@ var sites = map[string]site{
 		Host:          "asurascans.com",
 		LatestChapter: asuraLatestChapter,
 		Cover:         ogImageCover,
+		Completed:     asuraCompleted,
 		Rest:          defaultRest,
 		Gap:           defaultGap,
 	},
@@ -456,6 +550,7 @@ var sites = map[string]site{
 		Host:          "demonicscans.org",
 		LatestChapter: demonicLatestChapter,
 		Cover:         ogImageCover,
+		Completed:     demonicCompleted,
 		Rest:          defaultRest,
 		Gap:           defaultGap,
 	},
@@ -463,6 +558,7 @@ var sites = map[string]site{
 		Host:          "comix.to",
 		LatestChapter: comixLatestChapter,
 		Cover:         comixCoverEntry,
+		Completed:     comixCompleted,
 		Rest:          defaultRest,
 		Gap:           defaultGap,
 		Browser: &browserRead{
@@ -479,6 +575,7 @@ var sites = map[string]site{
 		Host:          "kagane.to",
 		LatestChapter: kaganeLatestChapter,
 		Cover:         kaganeCoverEntry,
+		Completed:     kaganeCompleted,
 		Rest:          defaultRest,
 		Gap:           defaultGap,
 		Browser: &browserRead{
@@ -493,6 +590,7 @@ var sites = map[string]site{
 		Host:          "novelfull.com",
 		LatestChapter: novelfullLatestChapter,
 		Cover:         novelfullCoverEntry,
+		Completed:     novelfullCompleted,
 		Rest:          defaultRest,
 		Gap:           defaultGap,
 		Browser: &browserRead{
@@ -507,6 +605,7 @@ var sites = map[string]site{
 		Host:          "lightnovelworld.net",
 		LatestChapter: lnwLatestChapter,
 		Cover:         ogImageCover,
+		Completed:     lnwCompleted,
 		Rest:          defaultRest,
 		Gap:           defaultGap,
 	},
@@ -524,6 +623,12 @@ func SiteNames() []string {
 	return names
 }
 
+// BrowserBackedSites is derived from the registry: the Sites whose pages are
+// read through the browser sidecar. Sorted so callers that range it (the
+// browser fetcher's dispatch) see a stable order instead of map-iteration
+// noise. Exported so the web layer shares the same set the poller does.
+func BrowserBackedSites() []string { return browserBackedSites() }
+
 // browserBackedSites is derived from the registry: the Sites whose pages are
 // read through the browser sidecar. Sorted so callers that range it (the
 // browser fetcher's dispatch) see a stable order instead of map-iteration

backend/internal/latest/sites_test.go

@@ -188,6 +188,104 @@ const lnwSeriesFixture = `
 </div>
 `
 
+// Completed-marker fixtures, trimmed from the live pages fetched 2026-08-22
+// for the verification step below. Selector-removed rows delete the marker
+// from the consts and must answer false.
+
+// Trimmed from https://asurascans.com/comics/solo-leveling (301 to
+// /comics/solo-leveling-b60d532c) fetched 2026-08-22 by a curl probe from
+// this machine. The astro-island props are HTML-escaped in the served
+// document, so the quotes arrive as &quot;.
+const asuraCompletedFixture = `
+&quot;bookmarkCount&quot;:[0,39128],&quot;status&quot;:[0,&quot;completed&quot;],&quot;type&quot;:[0,&quot;manhwa&quot;]
+`
+
+// Trimmed from https://asurascans.com/comics/chronicles-of-the-demon-faction-f886a8af
+// fetched 2026-08-22 by a curl probe.
+const asuraOngoingFixture = `
+&quot;bookmarkCount&quot;:[0,54027],&quot;status&quot;:[0,&quot;ongoing&quot;],&quot;type&quot;:[0,&quot;manhwa&quot;]
+`
+
+// Trimmed from https://demonicscans.org/manga/Solo-Leveling fetched
+// 2026-08-22 by a curl probe. The info block is sloppy: bare <li>s inside a
+// <div>, label and value as a sibling pair.
+const demonicCompletedFixture = `
+<div class="flex flex-row">
+    <li style="width:150px;color:#b2b2b2;">Status</li>
+    <li>Completed</li>
+</div>
+`
+
+// Trimmed from https://demonicscans.org/manga/Catastrophic-Necromancer
+// fetched 2026-08-22 by a curl probe. Same block, ongoing value.
+const demonicOngoingFixture = `
+<div class="flex flex-row">
+    <li style="width:150px;color:#b2b2b2;">Status</li>
+    <li>Ongoing</li>
+</div>
+`
+
+// Trimmed from https://comix.to/title/q77m-countach fetched 2026-08-22 by a
+// cleared Chrome tab (the CDP sidecar: the Series URL is fetched in-tab, the
+// same server-rendered payload the poll reads). The served page escapes the
+// query map keys as \u0022; the fixture carries the decoded form, which
+// parses to the same key. The recommended strip on this very page carries a
+// finished entry; only the ["manga","detail","q77m"] entry counts.
+const comixCompletedFixture = `<script type="application/json" id="initial-data">{"queries":{"[\"manga\",\"recommended\",\"q77m\",1]":{"items":[{"hid":"pz65","title":"Wangan Midnight: C1 Runner","status":"finished"}]},"[\"manga\",\"detail\",\"q77m\"]":{"id":13211,"hid":"q77m","title":"Countach","status":"finished","originalLanguage":"ja"}}}</script>`
+
+// Trimmed from https://comix.to/title/n8we-dungeons-and-crayons fetched
+// 2026-08-22 the same way (keys in their decoded form, as above). The
+// recommended strip includes a finished entry; the target detail is
+// releasing, and only the detail read counts.
+const comixOngoingFixture = `<script type="application/json" id="initial-data">{"queries":{"[\"manga\",\"recommended\",\"n8we\",1]":{"items":[{"hid":"g2rk","title":"On the Way to Meet Mom","status":"finished"}]},"[\"manga\",\"detail\",\"n8we\"]":{"id":1429,"hid":"n8we","title":"Dungeons and Crayons","status":"releasing","originalLanguage":"ko"}}}</script>`
+
+// Trimmed from GET https://kagane.to/api/v2/series/019f84bc-9ba0-7ed9-86f5-8b905ec7c28b
+// fetched 2026-08-22 in a cleared Chrome tab (plain TLS serves the Cloudflare
+// challenge).
+const kaganeOngoingFixture = `{"series_id":"019f84bc-9ba0-7ed9-86f5-8b905ec7c28b","title":"Infinite Decryption: The Strongest Level 0","publication_status":"Ongoing","upload_status":"Ongoing"}`
+
+// Trimmed from GET https://kagane.to/api/v2/series/019c29c3-5abd-70e6-9efc-1f1f22d839f6
+// fetched 2026-08-22 the same way.
+const kaganeCompletedFixture = `{"series_id":"019c29c3-5abd-70e6-9efc-1f1f22d839f6","title":"Real Account 1-17","publication_status":"Completed","upload_status":"Completed"}`
+
+// Composed, not a single live trim: upload Completed alongside a
+// non-Completed publication status is the research note's inferred inverse
+// case and did not turn up in the ~1900-series live scan of 2026-08-22 (both
+// field vocabularies are live-verified; the note's live divergence is 'Cause
+// Calypso Can, publication Ongoing + upload Hiatus). The predicate must read
+// publication_status only.
+const kaganeDivergentFixture = `{"series_id":"019f84bc-9ba0-7ed9-86f5-8b905ec7c28b","title":"Infinite Decryption: The Strongest Level 0","publication_status":"Ongoing","upload_status":"Completed"}`
+
+// Trimmed from https://novelfull.com/reverend-insanity.html fetched
+// 2026-08-22 in a cleared Chrome tab after the plain-TLS probe was served the
+// challenge (time-varying; plain curl answered 403 the same day).
+const novelfullCompletedFixture = `<div><h3>Status:</h3><a href="/status/Completed">Completed</a></div>`
+
+// Trimmed from https://novelfull.com/a-cunning-pervert-in-the-cultivation-world.html
+// fetched 2026-08-22 the same way.
+const novelfullOngoingFixture = `<div><h3>Status:</h3><a href="/status/Ongoing">Ongoing</a></div>`
+
+// Trimmed from the JSON-LD block in the head of
+// https://lightnovelworld.net/novel/a-will-eternal/ fetched 2026-08-22. The
+// block sits ahead of the wpdiscuz thread, so the predicate reads the whole
+// body and needs no comment marker, unlike lnwLatestChapter.
+const lnwCompletedFixture = `<script type="application/ld+json">{
+    "@context": "https://schema.org",
+    "@type": "Book",
+    "name": "A Will Eternal",
+    "creativeWorkStatus": "https://schema.org/CompletedActionStatus"
+}</script>`
+
+// Trimmed from
+// https://lightnovelworld.net/novel/all-jobs-and-classes-i-just-wanted-one-skill-not-them-all/
+// fetched 2026-08-22. Same block, ongoing value.
+const lnwOngoingFixture = `<script type="application/ld+json">{
+    "@context": "https://schema.org",
+    "@type": "Book",
+    "name": "All Jobs and Classes I Just Wanted One Skill Not Them All",
+    "creativeWorkStatus": "https://schema.org/ActiveActionStatus"
+}</script>`
+
 // Trimmed from https://asurascans.com/comics/chronicles-of-the-demon-faction-f886a8af
 // (redirected to ...-00dcbf97) on 2026-08-10.
 const asuraCoverFixture = `<meta property="og:image" content="https://cdn.asurascans.com/asura-images/covers/chronicles-of-the-demon-faction.d4dcb8.webp">`
@@ -473,3 +571,178 @@ func TestLatestChapterFrom(t *testing.T) {
 		})
 	}
 }
+
+func TestSiteCompletedFrom(t *testing.T) {
+	const asuraURL = "https://asurascans.com/comics/solo-leveling-b60d532c"
+	const demonicURL = "https://demonicscans.org/manga/Solo-Leveling"
+	const comixURL = "https://comix.to/title/q77m-countach"
+	const kaganeURL = "https://kagane.to/series/019f84bc-9ba0-7ed9-86f5-8b905ec7c28b"
+	const novelfullURL = "https://novelfull.com/reverend-insanity.html"
+	const lnwURL = "https://lightnovelworld.net/novel/a-will-eternal/"
+
+	tests := []struct {
+		name      string
+		site      string
+		seriesURL string
+		body      string
+		want      bool
+	}{
+		{
+			name: "asura completed via escaped props status",
+			site: "asura", seriesURL: asuraURL, body: asuraCompletedFixture,
+			want: true,
+		},
+		{
+			name:      "asura ongoing value is not completed",
+			site:      "asura",
+			seriesURL: "https://asurascans.com/comics/chronicles-of-the-demon-faction-f886a8af",
+			body:      asuraOngoingFixture,
+			want:      false,
+		},
+		{
+			name: "asura with the status key removed",
+			site: "asura", seriesURL: asuraURL,
+			body: strings.ReplaceAll(asuraCompletedFixture, `&quot;status&quot;:[0,&quot;completed&quot;]`, ""),
+			want: false,
+		},
+		{
+			name: "asura challenge page",
+			site: "asura", seriesURL: asuraURL, body: challengeFixture,
+			want: false,
+		},
+		{
+			name: "demonic completed info-block pair",
+			site: "demonic", seriesURL: demonicURL, body: demonicCompletedFixture,
+			want: true,
+		},
+		{
+			name:      "demonic ongoing value is not completed",
+			site:      "demonic",
+			seriesURL: "https://demonicscans.org/manga/Catastrophic-Necromancer",
+			body:      demonicOngoingFixture,
+			want:      false,
+		},
+		{
+			name: "demonic with the value li removed",
+			site: "demonic", seriesURL: demonicURL,
+			body: strings.ReplaceAll(demonicCompletedFixture, "<li>Completed</li>", ""),
+			want: false,
+		},
+		{
+			name:      "comix recommended finished does not count",
+			site:      "comix",
+			seriesURL: "https://comix.to/title/n8we-dungeons-and-crayons",
+			body:      comixOngoingFixture,
+			want:      false,
+		},
+		{
+			name:      "comix detail finished wins over a finished recommended strip",
+			site:      "comix",
+			seriesURL: comixURL,
+			body:      comixCompletedFixture,
+			want:      true,
+		},
+		{
+			name: "comix with the detail status removed",
+			site: "comix", seriesURL: comixURL,
+			body: strings.ReplaceAll(comixCompletedFixture, `"status":"finished",`, ""),
+			want: false,
+		},
+		{
+			name: "comix challenge page",
+			site: "comix", seriesURL: comixURL, body: challengeFixture,
+			want: false,
+		},
+		{
+			name:      "kagane publication Completed",
+			site:      "kagane",
+			seriesURL: "https://kagane.to/series/019c29c3-5abd-70e6-9efc-1f1f22d839f6",
+			body:      kaganeCompletedFixture,
+			want:      true,
+		},
+		{
+			name: "kagane upload Completed does not count",
+			site: "kagane", seriesURL: kaganeURL, body: kaganeDivergentFixture,
+			want: false,
+		},
+		{
+			name: "kagane ongoing values are not completed",
+			site: "kagane", seriesURL: kaganeURL, body: kaganeOngoingFixture,
+			want: false,
+		},
+		{
+			name: "kagane with publication_status removed",
+			site: "kagane", seriesURL: kaganeURL,
+			body: strings.ReplaceAll(kaganeCompletedFixture, `"publication_status":"Completed",`, ""),
+			want: false,
+		},
+		{
+			name: "kagane challenge page",
+			site: "kagane", seriesURL: kaganeURL, body: challengeFixture,
+			want: false,
+		},
+		{
+			name:      "novelfull status link Completed",
+			site:      "novelfull",
+			seriesURL: novelfullURL,
+			body:      novelfullCompletedFixture,
+			want:      true,
+		},
+		{
+			name:      "novelfull ongoing link is not completed",
+			site:      "novelfull",
+			seriesURL: "https://novelfull.com/a-cunning-pervert-in-the-cultivation-world.html",
+			body:      novelfullOngoingFixture,
+			want:      false,
+		},
+		{
+			name: "novelfull with the status link removed",
+			site: "novelfull", seriesURL: novelfullURL,
+			body: strings.ReplaceAll(novelfullCompletedFixture, `<a href="/status/Completed">Completed</a>`, ""),
+			want: false,
+		},
+		{
+			name: "novelfull challenge page",
+			site: "novelfull", seriesURL: novelfullURL, body: challengeFixture,
+			want: false,
+		},
+		{
+			name:      "lightnovelworld JSON-LD CompletedActionStatus",
+			site:      "lightnovelworld",
+			seriesURL: lnwURL,
+			body:      lnwCompletedFixture,
+			want:      true,
+		},
+		{
+			name:      "lightnovelworld ActiveActionStatus is not completed",
+			site:      "lightnovelworld",
+			seriesURL: "https://lightnovelworld.net/novel/all-jobs-and-classes-i-just-wanted-one-skill-not-them-all/",
+			body:      lnwOngoingFixture,
+			want:      false,
+		},
+		{
+			name: "lightnovelworld with creativeWorkStatus removed",
+			site: "lightnovelworld", seriesURL: lnwURL,
+			body: strings.ReplaceAll(lnwCompletedFixture, `"creativeWorkStatus": "https://schema.org/CompletedActionStatus"`, ""),
+			want: false,
+		},
+		{
+			name: "lightnovelworld challenge page",
+			site: "lightnovelworld", seriesURL: lnwURL, body: challengeFixture,
+			want: false,
+		},
+		{
+			name: "unknown site",
+			site: "mangadex", seriesURL: "https://mangadex.org/title/x", body: asuraCompletedFixture,
+			want: false,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if got := siteCompletedFrom(tt.site, tt.seriesURL, tt.body); got != tt.want {
+				t.Errorf("siteCompletedFrom(%q, %q, body) = %v, want %v", tt.site, tt.seriesURL, got, tt.want)
+			}
+		})
+	}
+}