diff --git a/server/internal/api/workflows.go b/server/internal/api/workflows.go
index fcceb7d..58981c2 100644
--- a/server/internal/api/workflows.go
+++ b/server/internal/api/workflows.go
@@ -581,7 +581,7 @@ func deleteWorkflow(c *gin.Context) {
 //	@Security		bearerAuth
 //	@Router			/workflows/{id}/run [post]
 func runWorkflow(c *gin.Context) {
-	runID, err := services.TriggerWorkflow(auth.InstanceID(c), c.Param("id"), actorFromCtx(c))
+	runID, err := services.TriggerWorkflow(auth.InstanceID(c), c.Param("id"), actorFromCtx(c), auth.ServerScope(c))
 	if err != nil {
 		if errors.Is(err, services.ErrNoTargets) {
 			c.JSON(http.StatusBadRequest, gin.H{"error": "this workflow matches no servers"})
diff --git a/server/internal/mcp/tools_work.go b/server/internal/mcp/tools_work.go
index b087dc8..64002b4 100644
--- a/server/internal/mcp/tools_work.go
+++ b/server/internal/mcp/tools_work.go
@@ -314,6 +314,20 @@ func init() {
 				return nil, fmt.Errorf("server %q is not part of run %q", serverID, runID)
 			}
 
+			// Membership in the run is not scope: a run started before this
+			// token was restricted, or by an unrestricted credential, names
+			// servers this token must not read. The stdout of an
+			// out-of-scope host is exactly the data the tag restriction
+			// exists to withhold.
+			//
+			// The refusal reuses the membership message verbatim so that
+			// "in the run but out of your scope" and "not in the run at all"
+			// are indistinguishable — otherwise the difference between the
+			// two answers enumerates hosts the token cannot see.
+			if _, err := services.GetServerScoped(c.InstanceID, serverID, c.TokenScope); err != nil {
+				return nil, fmt.Errorf("server %q is not part of run %q", serverID, runID)
+			}
+
 			limit := defaultLogLimit
 			if raw, ok := args["limit"].(float64); ok && int(raw) > 0 {
 				limit = int(raw)
diff --git a/server/internal/mcp/tools_write.go b/server/internal/mcp/tools_write.go
index 2d7be3e..6d14eee 100644
--- a/server/internal/mcp/tools_write.go
+++ b/server/internal/mcp/tools_write.go
@@ -76,6 +76,15 @@ func init() {
 			if err != nil {
 				return nil, fmt.Errorf("this workflow matches no servers")
 			}
+			// This all-or-nothing pre-check is no longer the only guard:
+			// services.TriggerWorkflow now resolves through
+			// ResolveTargetsScoped itself, so a run started with this token
+			// can never touch a server outside its scope regardless of what
+			// happens here. It is kept because its refusal is the clearer
+			// answer for a model: the service layer would silently run
+			// against the in-scope subset, while a partially out-of-scope
+			// workflow is documented here as refused outright, which is
+			// behaviour a caller relies on.
 			scopedTargets, err := services.ResolveTargetsScoped(c.InstanceID, wf.TargetServerIDs, wf.TargetTags, c.TokenScope)
 			if err != nil || len(scopedTargets) != len(allTargets) {
 				return nil, fmt.Errorf("%w: no servers visible to this token matched the request", ErrOutOfScope)
@@ -85,7 +94,7 @@ func init() {
 				return nil, err
 			}
 
-			runID, err := services.TriggerWorkflow(c.InstanceID, workflowID, c.TokenName)
+			runID, err := services.TriggerWorkflow(c.InstanceID, workflowID, c.TokenName, c.TokenScope)
 			if err != nil {
 				return nil, fmt.Errorf("could not start the run: %w", err)
 			}
diff --git a/server/internal/services/workflow_runner.go b/server/internal/services/workflow_runner.go
index ba3a16d..c1e67e7 100644
--- a/server/internal/services/workflow_runner.go
+++ b/server/internal/services/workflow_runner.go
@@ -17,12 +17,24 @@ import (
 
 const stepDispatchGrace = 15 * time.Second
 
-func TriggerWorkflow(instanceID, workflowID, actor string) (string, error) {
+// TriggerWorkflow starts a run of workflow workflowID.
+//
+// tokenScope is the acting credential's tag restriction, nil meaning
+// unrestricted. It is threaded down to ResolveTargetsScoped rather than being
+// applied by the caller, because this is the one place a run's target set is
+// decided: a handler that resolved targets itself and then called an unscoped
+// trigger would leave the dispatch reaching further than the readout.
+//
+// A run whose configured targets fall entirely outside the caller's scope
+// resolves to nothing and returns ErrNoTargets — the same answer a workflow
+// targeting no servers at all gives, so an out-of-scope host stays
+// indistinguishable from one that does not exist.
+func TriggerWorkflow(instanceID, workflowID, actor string, tokenScope map[string]string) (string, error) {
 	wf, err := GetWorkflow(instanceID, workflowID)
 	if err != nil {
 		return "", err
 	}
-	targets, err := ResolveTargets(instanceID, wf.TargetServerIDs, wf.TargetTags)
+	targets, err := ResolveTargetsScoped(instanceID, wf.TargetServerIDs, wf.TargetTags, tokenScope)
 	if err != nil {
 		return "", err
 	}
diff --git a/server/internal/workflowsched/sched.go b/server/internal/workflowsched/sched.go
index da57cfb..9a8c299 100644
--- a/server/internal/workflowsched/sched.go
+++ b/server/internal/workflowsched/sched.go
@@ -17,7 +17,7 @@ const tickInterval = 30 * time.Second
 // imported because services already imports this package for NextOccurrence,
 // and a package cannot import its own importer.
 type Deps struct {
-	TriggerWorkflow func(instanceID, workflowID, actor string) (string, error)
+	TriggerWorkflow func(instanceID, workflowID, actor string, tokenScope map[string]string) (string, error)
 	LogEvent        func(instanceID, eventType, actor, serverID, keyID, details string)
 }
 
@@ -105,7 +105,13 @@ func process(ctx context.Context, deps Deps, wf models.Workflow, now time.Time)
 	case SkipRunning:
 		recordSkip(ctx, deps, wf, string(SkipRunning), dueAt, now)
 	case Fire:
-		if _, err := deps.TriggerWorkflow(wf.InstanceID, wf.WorkflowID, "schedule"); err != nil {
+		// nil tokenScope: the scheduler acts as the system, not as any user.
+		// A schedule fires the workflow's own saved targets, and there is no
+		// acting credential whose tag restriction could narrow them — the
+		// person who armed the schedule is not present at fire time, and
+		// inheriting a restriction from whoever last saved the workflow would
+		// make a run's reach depend on an editor's credential.
+		if _, err := deps.TriggerWorkflow(wf.InstanceID, wf.WorkflowID, "schedule", nil); err != nil {
 			log.Printf("workflowsched: trigger %s: %v", wf.WorkflowID, err)
 			recordSkip(ctx, deps, wf, "error: "+err.Error(), dueAt, now)
 			return