diff --git a/internal/drops/progress.go b/internal/drops/progress.go
index aa00784..b1647e6 100644
--- a/internal/drops/progress.go
+++ b/internal/drops/progress.go
@@ -100,12 +100,13 @@ func (s *Service) PollProgressOnce() {
 		return
 	}
 
-	s.ApplyProgressUpdate(twitch.DropProgressData{
-		CampaignID:             pickedCampID,
-		DropID:                 session.DropID,
-		CurrentMinutesWatched:  session.CurrentMinutesWatched,
-		RequiredMinutesWatched: session.RequiredMinutesWatched,
-	})
+	owned := s.campaignOwnsDrop(pickedCampID, session.DropID)
+	progress, done := progressFromSession(pickedCampID, session, owned)
+	s.ApplyProgressUpdate(progress)
+	if !owned && s.writeLogFile != nil {
+		s.writeLogFile(fmt.Sprintf("[Drops/Poll] session drop %s is not part of campaign %s — minutes applied, completion check skipped",
+			session.DropID, pickedCampID))
+	}
 
 	// When poll says the current drop is at 100%, do TWO things:
 	// 1. Try MarkCompletedIfFinishedExternally — fetches inventory + only
@@ -116,7 +117,7 @@ func (s *Service) PollProgressOnce() {
 	//    un-completed.
 	// 2. Trigger processDrops so the selector re-evaluates (next drop
 	//    in queue gets picked if this one is done, etc).
-	if session.RequiredMinutesWatched > 0 && session.CurrentMinutesWatched >= session.RequiredMinutesWatched {
+	if done {
 		if s.writeLogFile != nil {
 			s.writeLogFile(fmt.Sprintf("[Drops/Poll] drop complete on campaign %s (%d/%d)",
 				pickedCampID, session.CurrentMinutesWatched, session.RequiredMinutesWatched))
@@ -316,3 +317,31 @@ func (s *Service) LookupCampaignByDropID(dropID string) string {
 	}
 	return ""
 }
+
+func (s *Service) campaignOwnsDrop(campaignID, dropID string) bool {
+	s.mu.RLock()
+	defer s.mu.RUnlock()
+	for _, d := range s.campaignCache[campaignID].Drops {
+		if d.ID == dropID {
+			return true
+		}
+	}
+	return false
+}
+
+// Twitch's session can name a drop from a sibling campaign of the same game.
+// Its minutes still track the watched channel, but its drop ID and required
+// minutes belong to the other campaign and must not drive completion.
+func progressFromSession(pickedCampID string, session *twitch.CurrentDropSession, ownedByPick bool) (twitch.DropProgressData, bool) {
+	p := twitch.DropProgressData{
+		CampaignID:            pickedCampID,
+		CurrentMinutesWatched: session.CurrentMinutesWatched,
+	}
+	if !ownedByPick {
+		return p, false
+	}
+	p.DropID = session.DropID
+	p.RequiredMinutesWatched = session.RequiredMinutesWatched
+	done := session.RequiredMinutesWatched > 0 && session.CurrentMinutesWatched >= session.RequiredMinutesWatched
+	return p, done
+}
diff --git a/internal/drops/progress_session_test.go b/internal/drops/progress_session_test.go
new file mode 100644
index 0000000..e530568
--- /dev/null
+++ b/internal/drops/progress_session_test.go
@@ -0,0 +1,87 @@
+package drops
+
+import (
+	"testing"
+
+	"github.com/miwi/twitchpoint/internal/config"
+	"github.com/miwi/twitchpoint/internal/twitch"
+)
+
+// The session named WARDOGS Beta & Launch's claimed 30-min drop while the
+// pick was farming Early Access 0.1, whose drops need 660+ minutes.
+func TestProgressFromSession_SiblingCampaignDropNeverCompletes(t *testing.T) {
+	session := &twitch.CurrentDropSession{DropID: "wardog", CurrentMinutesWatched: 648, RequiredMinutesWatched: 30}
+
+	p, done := progressFromSession("early-access", session, false)
+
+	if done {
+		t.Fatal("a sibling campaign's finished drop marked the picked campaign's drop done")
+	}
+	if p.CampaignID != "early-access" || p.CurrentMinutesWatched != 648 {
+		t.Fatalf("minutes must still be applied to the pick, got %+v", p)
+	}
+	if p.DropID != "" || p.RequiredMinutesWatched != 0 {
+		t.Fatalf("sibling drop ID/required leaked into the pick's progress: %+v", p)
+	}
+}
+
+func TestProgressFromSession_OwnedDrop(t *testing.T) {
+	cases := []struct {
+		current, required int
+		wantDone          bool
+	}{
+		{647, 660, false},
+		{660, 660, true},
+		{700, 660, true},
+		{10, 0, false},
+	}
+	for _, c := range cases {
+		session := &twitch.CurrentDropSession{DropID: "silver-2", CurrentMinutesWatched: c.current, RequiredMinutesWatched: c.required}
+		p, done := progressFromSession("early-access", session, true)
+		if done != c.wantDone {
+			t.Fatalf("%d/%d: done=%v, want %v", c.current, c.required, done, c.wantDone)
+		}
+		if p.DropID != "silver-2" || p.RequiredMinutesWatched != c.required {
+			t.Fatalf("%d/%d: owned drop not passed through: %+v", c.current, c.required, p)
+		}
+	}
+}
+
+func TestCampaignOwnsDrop(t *testing.T) {
+	s := &Service{campaignCache: map[string]twitch.DropCampaign{
+		"early-access": {ID: "early-access", Drops: []twitch.TimeBasedDrop{{ID: "silver-2"}, {ID: "gold-4"}}},
+		"beta-launch":  {ID: "beta-launch", Drops: []twitch.TimeBasedDrop{{ID: "wardog"}}},
+	}}
+
+	if !s.campaignOwnsDrop("early-access", "gold-4") {
+		t.Fatal("own drop not recognised")
+	}
+	if s.campaignOwnsDrop("early-access", "wardog") {
+		t.Fatal("sibling campaign's drop attributed to the pick")
+	}
+	if s.campaignOwnsDrop("uncached", "silver-2") {
+		t.Fatal("uncached campaign must not claim ownership")
+	}
+}
+
+func TestApplyProgressUpdate_SiblingSessionKeepsRowRequired(t *testing.T) {
+	s := &Service{
+		cfg:          &config.Config{},
+		log:          func(string, ...interface{}) {},
+		writeLogFile: func(string) {},
+		campaignCache: map[string]twitch.DropCampaign{
+			"early-access": {ID: "early-access", Drops: []twitch.TimeBasedDrop{{ID: "silver-2", RequiredMinutesWatched: 660}}},
+		},
+		activeDrops: []ActiveDrop{{CampaignID: "early-access", DropName: "Silver Drop 2", Progress: 640, Required: 660}},
+	}
+	session := &twitch.CurrentDropSession{DropID: "wardog", CurrentMinutesWatched: 648, RequiredMinutesWatched: 30}
+
+	p, _ := progressFromSession("early-access", session, s.campaignOwnsDrop("early-access", "wardog"))
+	s.ApplyProgressUpdate(p)
+
+	row := s.activeDrops[0]
+	assertConsistent(t, row)
+	if row.Required != 660 || row.Progress != 648 || row.DropName != "Silver Drop 2" {
+		t.Fatalf("row corrupted by sibling session: %+v", row)
+	}
+}
diff --git a/internal/twitch/drops.go b/internal/twitch/drops.go
index ba01cb7..855b50a 100644
--- a/internal/twitch/drops.go
+++ b/internal/twitch/drops.go
@@ -211,7 +211,12 @@ func (g *GQLClient) GetDropsInventory() ([]DropCampaign, error) {
 	}
 
 	// Fetch inventory for progress data + gameEventDrops
-	inventoryCampaigns, claimedBenefits, _ := g.getDropsFromInventory()
+	inventoryCampaigns, claimedBenefits, err := g.getDropsFromInventory()
+	if err != nil {
+		// Without the inventory every campaign reads as not-in-progress,
+		// which the completion checks take as finished.
+		return nil, err
+	}
 
 	// One-shot diag: dump every inventory campaign so we can spot
 	// "should-be-active campaign missing or mislabeled" cases.
@@ -549,37 +554,26 @@ func (g *GQLClient) getDropsFromInventory() ([]DropCampaign, map[string]time.Tim
 	if err != nil {
 		return nil, nil, fmt.Errorf("get drops inventory: %w", err)
 	}
+	return parseInventoryResponse(resp.Data)
+}
 
-	currentUser, ok := resp.Data["currentUser"]
-	if !ok || currentUser == nil {
-		return nil, nil, nil
-	}
-	userMap, ok := currentUser.(map[string]interface{})
+func parseInventoryResponse(data map[string]interface{}) ([]DropCampaign, map[string]time.Time, error) {
+	userMap, ok := data["currentUser"].(map[string]interface{})
 	if !ok {
-		return nil, nil, nil
+		return nil, nil, fmt.Errorf("get drops inventory: response has no currentUser")
 	}
-
-	inventory, ok := userMap["inventory"]
-	if !ok || inventory == nil {
-		return nil, nil, nil
-	}
-	invMap, ok := inventory.(map[string]interface{})
+	invMap, ok := userMap["inventory"].(map[string]interface{})
 	if !ok {
-		return nil, nil, nil
+		return nil, nil, fmt.Errorf("get drops inventory: response has no inventory")
 	}
 
 	// Parse gameEventDrops — permanent history of all claimed benefit IDs
 	claimedBenefits := parseGameEventDrops(invMap)
 
-	campaignsRaw, ok := invMap["dropCampaignsInProgress"]
-	if !ok || campaignsRaw == nil {
-		return nil, claimedBenefits, nil
-	}
-	campaignList, ok := campaignsRaw.([]interface{})
+	campaignList, ok := invMap["dropCampaignsInProgress"].([]interface{})
 	if !ok {
 		return nil, claimedBenefits, nil
 	}
-
 	return parseCampaignList(campaignList), claimedBenefits, nil
 }
 
diff --git a/internal/twitch/inventory_parse_test.go b/internal/twitch/inventory_parse_test.go
new file mode 100644
index 0000000..04e0326
--- /dev/null
+++ b/internal/twitch/inventory_parse_test.go
@@ -0,0 +1,32 @@
+package twitch
+
+import "testing"
+
+func TestParseInventoryResponse_MissingDataIsAnError(t *testing.T) {
+	cases := map[string]map[string]interface{}{
+		"no currentUser":   {},
+		"null currentUser": {"currentUser": nil},
+		"no inventory":     {"currentUser": map[string]interface{}{}},
+		"null inventory":   {"currentUser": map[string]interface{}{"inventory": nil}},
+	}
+	for name, data := range cases {
+		if _, _, err := parseInventoryResponse(data); err == nil {
+			t.Fatalf("%s: parsed as an empty inventory instead of failing", name)
+		}
+	}
+}
+
+func TestParseInventoryResponse_NothingInProgress(t *testing.T) {
+	data := map[string]interface{}{"currentUser": map[string]interface{}{
+		"inventory": map[string]interface{}{"dropCampaignsInProgress": nil, "gameEventDrops": []interface{}{}},
+	}}
+
+	campaigns, _, err := parseInventoryResponse(data)
+
+	if err != nil {
+		t.Fatalf("a valid inventory with nothing in progress failed: %v", err)
+	}
+	if len(campaigns) != 0 {
+		t.Fatalf("expected no campaigns, got %d", len(campaigns))
+	}
+}