The forge-made merge's branch is read from the pull request's head label, not its head ref; the indexer checks the answer's number (issue 1966)

Claude-Session: https://claude.ai/code/session_01NcbgfFSnn24M3GcqttoU7i

modules/mesh-delivery-forge-bridge/cmd/mesh-delivery-forge-bridge-tools/main_test.go

@@ -182,6 +182,8 @@ func TestTheBridgeToolsReadTheGroupsAndAskTheEndAgain(t *testing.T) {
 				api: forgeAnswers(t, "/repos/novox/a/pulls/9", false, "fix/x", h2, "", "main"), fail: "not merged"},
 			{name: "a forge pull request merged into another branch", raws: map[string][]byte{}, repository: "novox/a", merge: c2, number: 9,
 				api: forgeAnswers(t, "/repos/novox/a/pulls/9", true, "fix/x", h2, c2, "dev"), fail: "not the trunk"},
+			{name: "a forge pull request with no head branch", raws: map[string][]byte{}, repository: "novox/a", merge: c2, number: 9,
+				api: forgeAnswers(t, "/repos/novox/a/pulls/9", true, "refs/pull/9/head", h2, c2, "main"), fail: "no head branch"},
 			{name: "a forge that does not answer", raws: map[string][]byte{}, repository: "novox/a", merge: c2,
 				api: func(string) (json.RawMessage, error) { return nil, errors.New("the forge is down") }, fail: "the forge is down"},
 		} {
@@ -214,7 +216,7 @@ func TestTheBridgeToolsReadTheGroupsAndAskTheEndAgain(t *testing.T) {
 func forgeAnswers(t *testing.T, path string, merged bool, branch, head, merge, base string) bridge.API {
 	t.Helper()
 	body, _ := json.Marshal(map[string]any{"number": 9, "merged": merged, "merge_commit_sha": merge,
-		"head": map[string]any{"ref": branch, "sha": head}, "base": map[string]any{"ref": base}})
+		"head": map[string]any{"ref": "refs/pull/9/head", "label": branch, "sha": head}, "base": map[string]any{"ref": base}})
 	return func(p string) (json.RawMessage, error) {
 		if p != path {
 			return nil, errors.New("the forge has no " + p)

modules/mesh-delivery-forge-bridge/internal/bridge/forgemade.go

@@ -4,6 +4,7 @@ import (
 	"encoding/json"
 	"fmt"
 	"net/url"
+	"strings"
 )
 
 // ForgePull is a pull request as the forge itself says it: what the bridge needs of a merge made on the forge, not
@@ -33,8 +34,8 @@ func ForgeMade(api API, owner, repo string, number int, merge string) (ForgePull
 		Merged         bool   `json:"merged"`
 		MergeCommitSHA string `json:"merge_commit_sha"`
 		Head           struct {
-			Ref string `json:"ref"`
+			Label string `json:"label"`
-			SHA string `json:"sha"`
+			SHA   string `json:"sha"`
 		} `json:"head"`
 		Base struct {
 			Ref string `json:"ref"`
@@ -51,5 +52,9 @@ func ForgeMade(api API, owner, repo string, number int, merge string) (ForgePull
 	case p.Base.Ref != Trunk:
 		return ForgePull{}, fmt.Errorf("the forge says %s/%s#%d was merged into %s, not the trunk %s", owner, repo, p.Number, p.Base.Ref, Trunk)
 	}
-	return ForgePull{Number: p.Number, Branch: p.Head.Ref, Head: p.Head.SHA, Merge: p.MergeCommitSHA}, nil
+	// For a merged pull request the forge's head.ref is "refs/pull/N/head"; the branch is in head.label (same-repository pull requests).
+	if p.Head.Label == "" || strings.HasPrefix(p.Head.Label, "refs/") {
+		return ForgePull{}, fmt.Errorf("the forge gives no head branch for %s/%s#%d (label %q)", owner, repo, p.Number, p.Head.Label)
+	}
+	return ForgePull{Number: p.Number, Branch: p.Head.Label, Head: p.Head.SHA, Merge: p.MergeCommitSHA}, nil
 }

modules/mesh-delivery-indexer/internal/index/pending.go

@@ -233,7 +233,7 @@ func (ix *Indexer) load(ctx context.Context, e PendingEntry) (PendingEntry, erro
 	if err != nil {
 		return e, fmt.Errorf("the forge bridge's answer for %s is not a forge message: %w", e.Key, err)
 	}
-	if f.Kind != forgemsg.ForgeMerged || f.Repository != e.Forge.Repository || f.Merge != e.Forge.Merge {
+	if f.Kind != forgemsg.ForgeMerged || f.Repository != e.Forge.Repository || f.Merge != e.Forge.Merge || (e.Forge.Number > 0 && f.Number != e.Forge.Number) {
 		return e, fmt.Errorf("the forge bridge's answer is not the merge %s#%d at %s that %s refers to", e.Forge.Repository, e.Forge.Number, e.Forge.Merge, e.Key)
 	}
 	e.Forge, e.Light = f, false