A node's answer holds as today what it holds today, so a seed that reproduces today is the same (issue 1126)

go/compose/frombus/answer.go

@@ -99,6 +99,7 @@ func Answer(ctx context.Context, r Reader, mesh Mesh, s Scope, fps map[string]st
 		for _, m := range sortedKeys(failed) {
 			a.Refusals = append(a.Refusals, delivery.ModuleRefused{Module: m, Why: failed[m]})
 		}
+		heldAsToday(&a, s.HeldToday)
 		a.Verdict = delivery.VerdictOf(a)
 		return a
 	}
@@ -203,10 +204,31 @@ func Answer(ctx context.Context, r Reader, mesh Mesh, s Scope, fps map[string]st
 		a.Refusals = append(a.Refusals, delivery.ModuleRefused{Module: m, Why: failed[m]})
 	}
 	sort.Slice(a.Refusals, func(i, j int) bool { return a.Refusals[i].Module < a.Refusals[j].Module })
+	heldAsToday(&a, s.HeldToday)
 	a.Verdict = delivery.VerdictOf(a)
 	return a
 }
 
+// heldAsToday moves each refusal of a module the node holds today (Scope.HeldToday) into Held: the candidate holds it as
+// the node does, which is no change (issue 1126: a seed reproduces today, and today holds it too).
+func heldAsToday(a *delivery.CandidateAnswer, today []string) {
+	if len(today) == 0 {
+		return
+	}
+	kept := a.Refusals[:0]
+	for _, r := range a.Refusals {
+		if slices.Contains(today, r.Module) {
+			a.Held = append(a.Held, r)
+		} else {
+			kept = append(kept, r)
+		}
+	}
+	a.Refusals = kept
+	if len(a.Refusals) == 0 {
+		a.Refusals = nil
+	}
+}
+
 // maxCulprits bounds the modules one refusal is tried on, each a whole composition.
 const maxCulprits = 8
 

go/compose/frombus/answer_rows_test.go

@@ -91,6 +91,13 @@ func answerNamesEveryRefusalAndLeavesAnOldBuildToTheNode(t *testing.T) {
 	if lemursOK := slices.ContainsFunc(a.Added, func(m delivery.ModuleAdded) bool { return m.Module == "lemurs" }); !lemursOK {
 		t.Errorf("lemurs, which composes, is not answered beside the refusals: %+v", a)
 	}
+	// Issue 1126: a module the node holds today that the candidate holds too is held as today, no refusal: with every
+	// refused module held today the verdict is no refusal, and each is named under Held.
+	today := Answer(ctx, b, Mesh{}, Scope{Node: "n1", Placements: given(b), HeldToday: []string{"api", "spiegel", "web"}},
+		map[string]string{"lemurs": fp("e"), "web": fp("1"), "api": fp("2"), "spiegel": fp("3")}, nil, "p-h1", 3)
+	if today.Verdict == delivery.CandidateRefused || len(today.Refusals) != 0 || len(today.Held) != 3 || today.Held[0].Why == "" {
+		t.Errorf("held as today: %+v", today)
+	}
 
 	// The fold: spiegel runs inside the node's own composition at a build of the old form. Its resources are carried as
 	// they run, each after the one it runs after: the node's own is the one it runs, and the node composes itself.

go/compose/frombus/frombus.go

@@ -124,6 +124,10 @@ type Scope struct {
 	Placements map[string]*delivery.Placement
 	InOwn      []string
 	Running    []delivery.Composed
+	// HeldToday is, in an answer, the modules the node holds today ("node" for its own composition): their have's phase
+	// is held, or they are held inside its own composition. A candidate that holds one too holds it as today, which is
+	// said under CandidateAnswer.Held and is no refusal (issue 1126).
+	HeldToday []string
 	// SameValue, in an answer, says whether two sealed values open to the same value (the node opens them with its own
 	// key), so a differing resource shows a value sealed again as such (delivery.CompareComposedWith). Nil shows them
 	// as differing.

go/delivery/placement_candidate.go

@@ -3,6 +3,7 @@ package delivery
 import (
 	"encoding/json"
 	"fmt"
+	"slices"
 	"strings"
 )
 
@@ -121,6 +122,9 @@ type CandidateAnswer struct {
 	Added    []ModuleAdded   `json:"added,omitempty"`
 	Removed  []string        `json:"removed,omitempty"`
 	Refusals []ModuleRefused `json:"refusals,omitempty"`
+	// Held is each module the candidate cannot compose that the node holds today too, with why: held as today, which
+	// changes nothing and counts for no verdict (issue 1126: a seed reproduces today).
+	Held []ModuleRefused `json:"held,omitempty"`
 	// Refused is why the node could not compose with the candidate at all; Refusals is then empty.
 	Refused string `json:"refused,omitempty"`
 	// Returns is, for a proposal that takes the node's placement key away, what the node does then: it returns to the
@@ -233,7 +237,7 @@ func (a CandidateAnswer) check() error {
 			return fmt.Errorf("delivery: a module the candidate adds is not named")
 		}
 	}
-	for _, d := range a.Refusals {
+	for _, d := range append(slices.Clone(a.Refusals), a.Held...) {
 		if d.Module == "" || d.Why == "" {
 			return fmt.Errorf("delivery: a candidate refusal names no module or no why")
 		}