fix: stabilize scm observer dispatch

backend/internal/observe/scm/observer.go

@@ -13,6 +13,7 @@ import (
 	"fmt"
 	"log/slog"
 	"path/filepath"
+	"sort"
 	"strings"
 	"sync"
 	"time"
@@ -330,10 +331,11 @@ func (o *Observer) Poll(ctx context.Context) error {
 		return err
 	}
 
-	for key, obs := range observations {
+	for _, key := range dispatchOrder(observations, selection.subjectsByPR) {
 		if err := ctx.Err(); err != nil {
 			return err
 		}
+		obs := observations[key]
 		subj, ok := selection.subjectsByPR[key]
 		if !ok {
 			continue
@@ -413,6 +415,30 @@ func (o *Observer) Poll(ctx context.Context) error {
 	return nil
 }
 
+// dispatchOrder returns observation keys in a deterministic order so lifecycle
+// notifications for a session are stable across polls.
+func dispatchOrder(observations map[string]ports.SCMObservation, subjectsByPR map[string]*subject) []string {
+	keys := make([]string, 0, len(observations))
+	for key := range observations {
+		keys = append(keys, key)
+	}
+	sessionOf := func(key string) string {
+		if s := subjectsByPR[key]; s != nil {
+			return string(s.session.ID)
+		}
+		return ""
+	}
+	sort.Slice(keys, func(i, j int) bool {
+		if si, sj := sessionOf(keys[i]), sessionOf(keys[j]); si != sj {
+			return si < sj
+		}
+		if ni, nj := observations[keys[i]].PR.Number, observations[keys[j]].PR.Number; ni != nj {
+			return ni < nj
+		}
+		return keys[i] < keys[j]
+	})
+	return keys
+}
 func (o *Observer) checkCredentials(ctx context.Context) (bool, error) {
 	var probe observe.CredentialProbe
 	if checker, ok := o.provider.(credentialChecker); ok {
@@ -573,11 +599,7 @@ func (o *Observer) workspaceSCMSessionRepos(ctx context.Context, proj domain.Pro
 
 func repoForTrackedPR(pr domain.PullRequest, repos []ports.SCMRepo) (ports.SCMRepo, bool) {
 	if pr.Provider != "" && pr.Host != "" && pr.Repo != "" {
-		owner, name, ok := strings.Cut(pr.Repo, "/")
-		if !ok || owner == "" || name == "" {
-			return ports.SCMRepo{}, false
-		}
-		return ports.SCMRepo{Provider: pr.Provider, Host: pr.Host, Owner: owner, Name: name, Repo: pr.Repo}, true
+		return ports.SCMRepo{Provider: pr.Provider, Host: pr.Host, Repo: pr.Repo}, true
 	}
 	if pr.Repo != "" {
 		for _, repo := range repos {

backend/internal/observe/scm/observer_test.go

@@ -12,6 +12,7 @@ import (
 	"io"
 	"log/slog"
 	"os/exec"
+	"path/filepath"
 	"strings"
 	"sync"
 	"testing"
@@ -228,6 +229,30 @@ func newTestObserver(store *fakeStore, provider *fakeProvider, lc Lifecycle, now
 	return New(provider, store, lc, Config{Clock: func() time.Time { return now }, Tick: time.Hour, Logger: quietSlog(), CacheMax: 128})
 }
 
+func TestDispatchOrderIsDeterministic(t *testing.T) {
+	obs := map[string]ports.SCMObservation{
+		"a#9": {PR: ports.SCMPRObservation{Number: 9}},
+		"a#7": {PR: ports.SCMPRObservation{Number: 7}},
+		"b#3": {PR: ports.SCMPRObservation{Number: 3}},
+	}
+	subjects := map[string]*subject{
+		"a#9": {session: domain.SessionRecord{ID: "sess-a"}},
+		"a#7": {session: domain.SessionRecord{ID: "sess-a"}},
+		"b#3": {session: domain.SessionRecord{ID: "sess-b"}},
+	}
+	want := []string{"a#7", "a#9", "b#3"}
+	for run := 0; run < 8; run++ {
+		got := dispatchOrder(obs, subjects)
+		if len(got) != len(want) {
+			t.Fatalf("run %d: got %d keys, want %d (%v)", run, len(got), len(want), got)
+		}
+		for i := range want {
+			if got[i] != want[i] {
+				t.Fatalf("run %d: order[%d]=%q, want %q (full %v)", run, i, got[i], want[i], got)
+			}
+		}
+	}
+}
 func quietSlog() *slog.Logger { return slog.New(slog.NewTextHandler(io.Discard, nil)) }
 
 func testStoreWithSession() *fakeStore {
@@ -281,9 +306,6 @@ func TestRepoForTrackedPRUsesPersistedRepoWhenCurrentScanDropsUpstream(t *testin
 	if repo.Provider != "github" || repo.Host != "github.com" || repo.Repo != "upstream/api" {
 		t.Fatalf("repo = %#v, want persisted upstream/api tuple", repo)
 	}
-	if repo.Owner != "upstream" || repo.Name != "api" {
-		t.Fatalf("repo owner/name = %q/%q, want upstream/api", repo.Owner, repo.Name)
-	}
 }
 
 func TestStartAsyncPerformsImmediatePollAndStopsOnCancel(t *testing.T) {
@@ -631,7 +653,7 @@ func TestPoll_DiscoversWorkspaceChildRepoPR(t *testing.T) {
 func TestPoll_DiscoversWorkspaceChildRepoUpstreamPR(t *testing.T) {
 	oldRemoteURLs := gitRemoteURLsFunc
 	gitRemoteURLsFunc = func(path string) []string {
-		if strings.HasSuffix(path, "/api") {
+		if strings.HasSuffix(filepath.ToSlash(path), "/api") {
 			return []string{"https://github.com/o/api.git", "https://github.com/upstream/api.git"}
 		}
 		return nil