fix(campaign): the action count leaves the setup's login out on a model run

Defects per thousand actions divided by every dispatched step, so a
spec whose setup logs in inflated the denominator by however many steps
that took. It is the same error the run gate had, and it does not cancel
between arms.

A model run is separable because only an llm-selected action stamps
next_action.source. A seeded run is not: its setup returns through the
same entry with no marker, and 11261 dispatched steps across the 169
recorded runs carry no source at all, so excluding on it blind would
report every seeded run as having explored nothing. The seeded arm
counts as before and a test pins that.

cmd/internal-tools/campaign/summary.go

@@ -20,11 +20,13 @@ const maxTraceLineBytes = 16 * 1024 * 1024
 // to open trace.jsonl again.
 type traceSummary struct {
 	Steps int `json:"steps"`
-	// Actions counts only the steps that both chose an action and dispatched
-	// it. A step whose policy declined to act, and a step whose chosen action
-	// the runner threw away, changed nothing about the app, so counting either
-	// as an action inflates the denominator of every per-action rate. The
-	// inflation is policy-dependent, so it does not cancel between arms.
+	// Actions counts only the steps on which the action generator both chose an
+	// action and dispatched it. A step whose policy declined to act, a step
+	// whose chosen action the runner threw away, and a step the spec's setup
+	// drove before the generator was ever consulted all explored nothing, so
+	// counting any of them as an action inflates the denominator of every
+	// per-action rate. The inflation is policy-dependent, so it does not cancel
+	// between arms.
 	Actions                    int      `json:"actions"`
 	FirstViolationOriginStep   *int     `json:"first_violation_origin_step"`
 	FirstViolationDetectedStep *int     `json:"first_violation_detected_step"`
@@ -45,20 +47,39 @@ type traceLine struct {
 	// Hierarchy is read only for its presence: the run-end finalize line is the
 	// one line carrying violations without an observed hierarchy.
 	Hierarchy json.RawMessage `json:"hierarchy"`
-	// NextAction is read only for its presence: a step that chose no action
-	// carries none at all.
-	NextAction          json.RawMessage          `json:"next_action"`
+	// NextAction is nil on a step that chose no action. Its Source names the
+	// backend that chose the action, which is the only thing in the trace
+	// separating a step the spec's setup drove from one the generator drove.
+	NextAction          *actionLine              `json:"next_action"`
 	ActionSkipped       string                   `json:"action_skipped"`
 	PreconditionFailure string                   `json:"precondition_failure"`
 	Violations          []string                 `json:"violations"`
 	Witnesses           map[string]trace.Witness `json:"witnesses"`
 }
 
-func dispatchedAction(line traceLine) bool {
-	if line.ActionSkipped != "" {
+type actionLine struct {
+	Source string `json:"source"`
+}
+
+// generatorDispatched reports whether this step drove the app on the action
+// generator's behalf, which is the exposure a per-action rate divides by. A
+// spec's setup puts the app into its starting position before the generator is
+// consulted, so its login taps are dispatched actions that explored nothing.
+//
+// Only a model run separates the two: the LLM backend stamps source="llm" on
+// what it chose and leaves setup's actions unstamped. The seeded picker resolves
+// setup precedence inside the one JS call it makes and stamps nothing at all, so
+// its setup steps are indistinguishable from its generator steps in the trace
+// and are counted; reading their absent source as setup would report every
+// seeded run as having explored nothing.
+func generatorDispatched(line traceLine, generator string) bool {
+	if line.ActionSkipped != "" || line.NextAction == nil {
 		return false
 	}
-	return len(line.NextAction) > 0 && string(line.NextAction) != "null"
+	if generator != "llm" {
+		return true
+	}
+	return line.NextAction.Source == "llm"
 }
 
 // findRunDirectory returns the run directory `sanderling test` created inside
@@ -92,14 +113,34 @@ func summarizeRun(seedDirectory string) (string, traceSummary, error) {
 	if err != nil {
 		return "", traceSummary{}, err
 	}
-	summary, err := summarizeTrace(filepath.Join(seedDirectory, name, "trace.jsonl"))
+	directory := filepath.Join(seedDirectory, name)
+	generator, err := runGenerator(directory)
+	if err != nil {
+		return name, traceSummary{}, err
+	}
+	summary, err := summarizeTrace(filepath.Join(directory, "trace.jsonl"), generator)
 	if err != nil {
 		return name, traceSummary{}, err
 	}
 	return name, summary, nil
 }
 
-func summarizeTrace(tracePath string) (traceSummary, error) {
+// runGenerator reads which picker drove the run. The trace on its own cannot
+// say whether an unstamped action came from the seeded picker or from the
+// spec's setup under the model picker, and the two count differently.
+func runGenerator(runDirectory string) (string, error) {
+	body, err := os.ReadFile(filepath.Join(runDirectory, "meta.json"))
+	if err != nil {
+		return "", fmt.Errorf("read meta: %w", err)
+	}
+	var meta trace.Meta
+	if err := json.Unmarshal(body, &meta); err != nil {
+		return "", fmt.Errorf("decode meta: %w", err)
+	}
+	return meta.Generator, nil
+}
+
+func summarizeTrace(tracePath, generator string) (traceSummary, error) {
 	file, err := os.Open(tracePath)
 	if err != nil {
 		return traceSummary{}, fmt.Errorf("open trace: %w", err)
@@ -127,7 +168,7 @@ func summarizeTrace(tracePath string) (traceSummary, error) {
 		if !synthetic && line.Index > summary.Steps {
 			summary.Steps = line.Index
 		}
-		if !synthetic && dispatchedAction(line) {
+		if !synthetic && generatorDispatched(line, generator) {
 			summary.Actions++
 		}
 		if line.PreconditionFailure != "" {

cmd/internal-tools/campaign/summary_test.go

@@ -34,13 +34,51 @@ func skippedActionStep(index int, reason string) trace.Step {
 	return step
 }
 
+func setupStep(index int) trace.Step {
+	step := observedStep(index)
+	step.NextAction = &trace.Action{
+		Kind:     "InputText",
+		Selector: "testTag:LoginScreen > testTag:LoginEmail",
+		Text:     "[email protected]",
+	}
+	return step
+}
+
+func modelStep(index int) trace.Step {
+	step := actingStep(index)
+	step.NextAction.Source = "llm"
+	return step
+}
+
+func skippedModelStep(index int, reason string) trace.Step {
+	step := modelStep(index)
+	step.ActionSkipped = reason
+	return step
+}
+
 func writeRunDirectory(t *testing.T, seedDirectory, name string, steps []trace.Step) string {
+	t.Helper()
+	return writeRunDirectoryWithMeta(
+		t,
+		seedDirectory,
+		name,
+		trace.Meta{Seed: 11, Platform: "web", Arm: "seeded-baseline"},
+		steps,
+	)
+}
+
+func writeRunDirectoryWithMeta(
+	t *testing.T,
+	seedDirectory, name string,
+	declared trace.Meta,
+	steps []trace.Step,
+) string {
 	t.Helper()
 	directory := filepath.Join(seedDirectory, name)
 	if err := os.MkdirAll(directory, 0o755); err != nil {
 		t.Fatal(err)
 	}
-	meta, err := json.Marshal(trace.Meta{Seed: 11, Platform: "web", Arm: "seeded-baseline"})
+	meta, err := json.Marshal(declared)
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -111,6 +149,68 @@ func TestSummarizeRun_CountsOnlyStepsThatDispatchedAnAction(t *testing.T) {
 	}
 }
 
+func TestSummarizeRun_ModelRunLeavesTheSetupsLoginOutOfTheActionCount(t *testing.T) {
+	seedDirectory := t.TempDir()
+	writeRunDirectoryWithMeta(t, seedDirectory, "20260812-090000",
+		trace.Meta{Seed: 11, Platform: "web", Arm: "llm-identifier", Generator: "llm"},
+		[]trace.Step{
+			setupStep(1),
+			setupStep(2),
+			setupStep(3),
+			modelStep(4),
+			skippedModelStep(5, "unresolved_selector"),
+			modelStep(6),
+		})
+
+	_, summary, err := summarizeRun(seedDirectory)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if summary.Steps != 6 {
+		t.Errorf("steps: got %d, want 6", summary.Steps)
+	}
+	if summary.Actions != 2 {
+		t.Errorf("actions: got %d, want 2 (three login steps were setup's and one generator action was thrown away)", summary.Actions)
+	}
+}
+
+func TestSummarizeRun_ModelRunWithoutSetupCountsEveryDispatchedStep(t *testing.T) {
+	seedDirectory := t.TempDir()
+	writeRunDirectoryWithMeta(t, seedDirectory, "20260812-090000",
+		trace.Meta{Seed: 11, Platform: "web", Arm: "llm-identifier", Generator: "llm"},
+		[]trace.Step{modelStep(1), modelStep(2), modelStep(3), modelStep(4)})
+
+	_, summary, err := summarizeRun(seedDirectory)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if summary.Actions != 4 {
+		t.Errorf("actions: got %d, want 4", summary.Actions)
+	}
+}
+
+func TestSummarizeRun_SeededRunCountsSetupBecauseItsTraceCannotNameIt(t *testing.T) {
+	seedDirectory := t.TempDir()
+	writeRunDirectoryWithMeta(t, seedDirectory, "20260812-090000",
+		trace.Meta{Seed: 11, Platform: "web", Arm: "seeded-baseline", Generator: "seeded"},
+		[]trace.Step{
+			setupStep(1),
+			setupStep(2),
+			setupStep(3),
+			actingStep(4),
+			actingStep(5),
+		})
+
+	_, summary, err := summarizeRun(seedDirectory)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if summary.Actions != 5 {
+		t.Errorf("actions: got %d, want 5: the seeded picker stamps no source, so excluding "+
+			"unstamped steps would count its whole run as setup", summary.Actions)
+	}
+}
+
 func TestSummarizeRun_SkipReasonsEachSuppressTheAction(t *testing.T) {
 	for _, reason := range []string{
 		"no_target", "unresolved_selector", "missing_key",