diff --git a/cmd/ooniprobe/internal/nettests/nettests.go b/cmd/ooniprobe/internal/nettests/nettests.go
index 711c544..2a0a275 100644
--- a/cmd/ooniprobe/internal/nettests/nettests.go
+++ b/cmd/ooniprobe/internal/nettests/nettests.go
@@ -1,6 +1,7 @@
 package nettests
 
 import (
+	"context"
 	"database/sql"
 	"fmt"
 	"time"
@@ -122,7 +123,7 @@ func (c *Controller) SetNettestIndex(i, n int) {
 //
 // This function will continue to run in most cases but will
 // immediately halt if something's wrong with the file system.
-func (c *Controller) Run(builder *engine.ExperimentBuilder, inputs []string) error {
+func (c *Controller) Run(builder engine.ExperimentBuilder, inputs []string) error {
 	// This will configure the controller as handler for the callbacks
 	// called by ooni/probe-engine/experiment.Experiment.
 	builder.SetCallbacks(model.ExperimentCallbacks(c))
@@ -143,7 +144,7 @@ func (c *Controller) Run(builder *engine.ExperimentBuilder, inputs []string) err
 	log.Debug(color.RedString("status.started"))
 
 	if c.Probe.Config().Sharing.UploadResults {
-		if err := exp.OpenReport(); err != nil {
+		if err := exp.OpenReportContext(context.Background()); err != nil {
 			log.Debugf(
 				"%s: %s", color.RedString("failure.report_create"), err.Error(),
 			)
@@ -197,7 +198,7 @@ func (c *Controller) Run(builder *engine.ExperimentBuilder, inputs []string) err
 		if input != "" {
 			c.OnProgress(0, fmt.Sprintf("processing input: %s", input))
 		}
-		measurement, err := exp.Measure(input)
+		measurement, err := exp.MeasureWithContext(context.Background(), input)
 		if err != nil {
 			log.WithError(err).Debug(color.RedString("failure.measurement"))
 			if err := c.msmts[idx64].Failed(c.Probe.DB(), err.Error()); err != nil {
@@ -218,7 +219,7 @@ func (c *Controller) Run(builder *engine.ExperimentBuilder, inputs []string) err
 			// Implementation note: SubmitMeasurement will fail here if we did fail
 			// to open the report but we still want to continue. There will be a
 			// bit of a spew in the logs, perhaps, but stopping seems less efficient.
-			if err := exp.SubmitAndUpdateMeasurement(measurement); err != nil {
+			if err := exp.SubmitAndUpdateMeasurementContext(context.Background(), measurement); err != nil {
 				log.Debug(color.RedString("failure.measurement_submission"))
 				if err := c.msmts[idx64].UploadFailed(c.Probe.DB(), err.Error()); err != nil {
 					return errors.Wrap(err, "failed to mark upload as failed")
diff --git a/internal/engine/allexperiments.go b/internal/engine/allexperiments.go
index f702118..d3471d7 100644
--- a/internal/engine/allexperiments.go
+++ b/internal/engine/allexperiments.go
@@ -1,5 +1,9 @@
 package engine
 
+//
+// List of all implemented experiments
+//
+
 import (
 	"time"
 
@@ -32,11 +36,11 @@ import (
 	"github.com/ooni/probe-cli/v3/internal/engine/experiment/whatsapp"
 )
 
-var experimentsByName = map[string]func(*Session) *ExperimentBuilder{
-	"dash": func(session *Session) *ExperimentBuilder {
-		return &ExperimentBuilder{
-			build: func(config interface{}) *Experiment {
-				return NewExperiment(session, dash.NewExperimentMeasurer(
+var experimentsByName = map[string]func(*Session) *experimentBuilder{
+	"dash": func(session *Session) *experimentBuilder {
+		return &experimentBuilder{
+			build: func(config interface{}) *experiment {
+				return newExperiment(session, dash.NewExperimentMeasurer(
 					*config.(*dash.Config),
 				))
 			},
@@ -46,10 +50,10 @@ var experimentsByName = map[string]func(*Session) *ExperimentBuilder{
 		}
 	},
 
-	"dnscheck": func(session *Session) *ExperimentBuilder {
-		return &ExperimentBuilder{
-			build: func(config interface{}) *Experiment {
-				return NewExperiment(session, dnscheck.NewExperimentMeasurer(
+	"dnscheck": func(session *Session) *experimentBuilder {
+		return &experimentBuilder{
+			build: func(config interface{}) *experiment {
+				return newExperiment(session, dnscheck.NewExperimentMeasurer(
 					*config.(*dnscheck.Config),
 				))
 			},
@@ -58,10 +62,10 @@ var experimentsByName = map[string]func(*Session) *ExperimentBuilder{
 		}
 	},
 
-	"dnsping": func(session *Session) *ExperimentBuilder {
-		return &ExperimentBuilder{
-			build: func(config interface{}) *Experiment {
-				return NewExperiment(session, dnsping.NewExperimentMeasurer(
+	"dnsping": func(session *Session) *experimentBuilder {
+		return &experimentBuilder{
+			build: func(config interface{}) *experiment {
+				return newExperiment(session, dnsping.NewExperimentMeasurer(
 					*config.(*dnsping.Config),
 				))
 			},
@@ -70,10 +74,10 @@ var experimentsByName = map[string]func(*Session) *ExperimentBuilder{
 		}
 	},
 
-	"example": func(session *Session) *ExperimentBuilder {
-		return &ExperimentBuilder{
-			build: func(config interface{}) *Experiment {
-				return NewExperiment(session, example.NewExperimentMeasurer(
+	"example": func(session *Session) *experimentBuilder {
+		return &experimentBuilder{
+			build: func(config interface{}) *experiment {
+				return newExperiment(session, example.NewExperimentMeasurer(
 					*config.(*example.Config), "example",
 				))
 			},
@@ -86,10 +90,10 @@ var experimentsByName = map[string]func(*Session) *ExperimentBuilder{
 		}
 	},
 
-	"facebook_messenger": func(session *Session) *ExperimentBuilder {
-		return &ExperimentBuilder{
-			build: func(config interface{}) *Experiment {
-				return NewExperiment(session, fbmessenger.NewExperimentMeasurer(
+	"facebook_messenger": func(session *Session) *experimentBuilder {
+		return &experimentBuilder{
+			build: func(config interface{}) *experiment {
+				return newExperiment(session, fbmessenger.NewExperimentMeasurer(
 					*config.(*fbmessenger.Config),
 				))
 			},
@@ -98,10 +102,10 @@ var experimentsByName = map[string]func(*Session) *ExperimentBuilder{
 		}
 	},
 
-	"http_header_field_manipulation": func(session *Session) *ExperimentBuilder {
-		return &ExperimentBuilder{
-			build: func(config interface{}) *Experiment {
-				return NewExperiment(session, hhfm.NewExperimentMeasurer(
+	"http_header_field_manipulation": func(session *Session) *experimentBuilder {
+		return &experimentBuilder{
+			build: func(config interface{}) *experiment {
+				return newExperiment(session, hhfm.NewExperimentMeasurer(
 					*config.(*hhfm.Config),
 				))
 			},
@@ -110,10 +114,10 @@ var experimentsByName = map[string]func(*Session) *ExperimentBuilder{
 		}
 	},
 
-	"http_host_header": func(session *Session) *ExperimentBuilder {
-		return &ExperimentBuilder{
-			build: func(config interface{}) *Experiment {
-				return NewExperiment(session, httphostheader.NewExperimentMeasurer(
+	"http_host_header": func(session *Session) *experimentBuilder {
+		return &experimentBuilder{
+			build: func(config interface{}) *experiment {
+				return newExperiment(session, httphostheader.NewExperimentMeasurer(
 					*config.(*httphostheader.Config),
 				))
 			},
@@ -122,10 +126,10 @@ var experimentsByName = map[string]func(*Session) *ExperimentBuilder{
 		}
 	},
 
-	"http_invalid_request_line": func(session *Session) *ExperimentBuilder {
-		return &ExperimentBuilder{
-			build: func(config interface{}) *Experiment {
-				return NewExperiment(session, hirl.NewExperimentMeasurer(
+	"http_invalid_request_line": func(session *Session) *experimentBuilder {
+		return &experimentBuilder{
+			build: func(config interface{}) *experiment {
+				return newExperiment(session, hirl.NewExperimentMeasurer(
 					*config.(*hirl.Config),
 				))
 			},
@@ -134,10 +138,10 @@ var experimentsByName = map[string]func(*Session) *ExperimentBuilder{
 		}
 	},
 
-	"ndt": func(session *Session) *ExperimentBuilder {
-		return &ExperimentBuilder{
-			build: func(config interface{}) *Experiment {
-				return NewExperiment(session, ndt7.NewExperimentMeasurer(
+	"ndt": func(session *Session) *experimentBuilder {
+		return &experimentBuilder{
+			build: func(config interface{}) *experiment {
+				return newExperiment(session, ndt7.NewExperimentMeasurer(
 					*config.(*ndt7.Config),
 				))
 			},
@@ -147,10 +151,10 @@ var experimentsByName = map[string]func(*Session) *ExperimentBuilder{
 		}
 	},
 
-	"psiphon": func(session *Session) *ExperimentBuilder {
-		return &ExperimentBuilder{
-			build: func(config interface{}) *Experiment {
-				return NewExperiment(session, psiphon.NewExperimentMeasurer(
+	"psiphon": func(session *Session) *experimentBuilder {
+		return &experimentBuilder{
+			build: func(config interface{}) *experiment {
+				return newExperiment(session, psiphon.NewExperimentMeasurer(
 					*config.(*psiphon.Config),
 				))
 			},
@@ -159,10 +163,10 @@ var experimentsByName = map[string]func(*Session) *ExperimentBuilder{
 		}
 	},
 
-	"quicping": func(session *Session) *ExperimentBuilder {
-		return &ExperimentBuilder{
-			build: func(config interface{}) *Experiment {
-				return NewExperiment(session, quicping.NewExperimentMeasurer(
+	"quicping": func(session *Session) *experimentBuilder {
+		return &experimentBuilder{
+			build: func(config interface{}) *experiment {
+				return newExperiment(session, quicping.NewExperimentMeasurer(
 					*config.(*quicping.Config),
 				))
 			},
@@ -171,10 +175,10 @@ var experimentsByName = map[string]func(*Session) *ExperimentBuilder{
 		}
 	},
 
-	"riseupvpn": func(session *Session) *ExperimentBuilder {
-		return &ExperimentBuilder{
-			build: func(config interface{}) *Experiment {
-				return NewExperiment(session, riseupvpn.NewExperimentMeasurer(
+	"riseupvpn": func(session *Session) *experimentBuilder {
+		return &experimentBuilder{
+			build: func(config interface{}) *experiment {
+				return newExperiment(session, riseupvpn.NewExperimentMeasurer(
 					*config.(*riseupvpn.Config),
 				))
 			},
@@ -183,10 +187,10 @@ var experimentsByName = map[string]func(*Session) *ExperimentBuilder{
 		}
 	},
 
-	"run": func(session *Session) *ExperimentBuilder {
-		return &ExperimentBuilder{
-			build: func(config interface{}) *Experiment {
-				return NewExperiment(session, run.NewExperimentMeasurer(
+	"run": func(session *Session) *experimentBuilder {
+		return &experimentBuilder{
+			build: func(config interface{}) *experiment {
+				return newExperiment(session, run.NewExperimentMeasurer(
 					*config.(*run.Config),
 				))
 			},
@@ -195,10 +199,10 @@ var experimentsByName = map[string]func(*Session) *ExperimentBuilder{
 		}
 	},
 
-	"simplequicping": func(session *Session) *ExperimentBuilder {
-		return &ExperimentBuilder{
-			build: func(config interface{}) *Experiment {
-				return NewExperiment(session, simplequicping.NewExperimentMeasurer(
+	"simplequicping": func(session *Session) *experimentBuilder {
+		return &experimentBuilder{
+			build: func(config interface{}) *experiment {
+				return newExperiment(session, simplequicping.NewExperimentMeasurer(
 					*config.(*simplequicping.Config),
 				))
 			},
@@ -207,10 +211,10 @@ var experimentsByName = map[string]func(*Session) *ExperimentBuilder{
 		}
 	},
 
-	"signal": func(session *Session) *ExperimentBuilder {
-		return &ExperimentBuilder{
-			build: func(config interface{}) *Experiment {
-				return NewExperiment(session, signal.NewExperimentMeasurer(
+	"signal": func(session *Session) *experimentBuilder {
+		return &experimentBuilder{
+			build: func(config interface{}) *experiment {
+				return newExperiment(session, signal.NewExperimentMeasurer(
 					*config.(*signal.Config),
 				))
 			},
@@ -219,10 +223,10 @@ var experimentsByName = map[string]func(*Session) *ExperimentBuilder{
 		}
 	},
 
-	"sni_blocking": func(session *Session) *ExperimentBuilder {
-		return &ExperimentBuilder{
-			build: func(config interface{}) *Experiment {
-				return NewExperiment(session, sniblocking.NewExperimentMeasurer(
+	"sni_blocking": func(session *Session) *experimentBuilder {
+		return &experimentBuilder{
+			build: func(config interface{}) *experiment {
+				return newExperiment(session, sniblocking.NewExperimentMeasurer(
 					*config.(*sniblocking.Config),
 				))
 			},
@@ -231,10 +235,10 @@ var experimentsByName = map[string]func(*Session) *ExperimentBuilder{
 		}
 	},
 
-	"stunreachability": func(session *Session) *ExperimentBuilder {
-		return &ExperimentBuilder{
-			build: func(config interface{}) *Experiment {
-				return NewExperiment(session, stunreachability.NewExperimentMeasurer(
+	"stunreachability": func(session *Session) *experimentBuilder {
+		return &experimentBuilder{
+			build: func(config interface{}) *experiment {
+				return newExperiment(session, stunreachability.NewExperimentMeasurer(
 					*config.(*stunreachability.Config),
 				))
 			},
@@ -243,10 +247,10 @@ var experimentsByName = map[string]func(*Session) *ExperimentBuilder{
 		}
 	},
 
-	"tcpping": func(session *Session) *ExperimentBuilder {
-		return &ExperimentBuilder{
-			build: func(config interface{}) *Experiment {
-				return NewExperiment(session, tcpping.NewExperimentMeasurer(
+	"tcpping": func(session *Session) *experimentBuilder {
+		return &experimentBuilder{
+			build: func(config interface{}) *experiment {
+				return newExperiment(session, tcpping.NewExperimentMeasurer(
 					*config.(*tcpping.Config),
 				))
 			},
@@ -255,10 +259,10 @@ var experimentsByName = map[string]func(*Session) *ExperimentBuilder{
 		}
 	},
 
-	"tlsping": func(session *Session) *ExperimentBuilder {
-		return &ExperimentBuilder{
-			build: func(config interface{}) *Experiment {
-				return NewExperiment(session, tlsping.NewExperimentMeasurer(
+	"tlsping": func(session *Session) *experimentBuilder {
+		return &experimentBuilder{
+			build: func(config interface{}) *experiment {
+				return newExperiment(session, tlsping.NewExperimentMeasurer(
 					*config.(*tlsping.Config),
 				))
 			},
@@ -267,10 +271,10 @@ var experimentsByName = map[string]func(*Session) *ExperimentBuilder{
 		}
 	},
 
-	"telegram": func(session *Session) *ExperimentBuilder {
-		return &ExperimentBuilder{
-			build: func(config interface{}) *Experiment {
-				return NewExperiment(session, telegram.NewExperimentMeasurer(
+	"telegram": func(session *Session) *experimentBuilder {
+		return &experimentBuilder{
+			build: func(config interface{}) *experiment {
+				return newExperiment(session, telegram.NewExperimentMeasurer(
 					*config.(*telegram.Config),
 				))
 			},
@@ -279,10 +283,10 @@ var experimentsByName = map[string]func(*Session) *ExperimentBuilder{
 		}
 	},
 
-	"tlstool": func(session *Session) *ExperimentBuilder {
-		return &ExperimentBuilder{
-			build: func(config interface{}) *Experiment {
-				return NewExperiment(session, tlstool.NewExperimentMeasurer(
+	"tlstool": func(session *Session) *experimentBuilder {
+		return &experimentBuilder{
+			build: func(config interface{}) *experiment {
+				return newExperiment(session, tlstool.NewExperimentMeasurer(
 					*config.(*tlstool.Config),
 				))
 			},
@@ -291,10 +295,10 @@ var experimentsByName = map[string]func(*Session) *ExperimentBuilder{
 		}
 	},
 
-	"tor": func(session *Session) *ExperimentBuilder {
-		return &ExperimentBuilder{
-			build: func(config interface{}) *Experiment {
-				return NewExperiment(session, tor.NewExperimentMeasurer(
+	"tor": func(session *Session) *experimentBuilder {
+		return &experimentBuilder{
+			build: func(config interface{}) *experiment {
+				return newExperiment(session, tor.NewExperimentMeasurer(
 					*config.(*tor.Config),
 				))
 			},
@@ -303,10 +307,10 @@ var experimentsByName = map[string]func(*Session) *ExperimentBuilder{
 		}
 	},
 
-	"torsf": func(session *Session) *ExperimentBuilder {
-		return &ExperimentBuilder{
-			build: func(config interface{}) *Experiment {
-				return NewExperiment(session, torsf.NewExperimentMeasurer(
+	"torsf": func(session *Session) *experimentBuilder {
+		return &experimentBuilder{
+			build: func(config interface{}) *experiment {
+				return newExperiment(session, torsf.NewExperimentMeasurer(
 					*config.(*torsf.Config),
 				))
 			},
@@ -315,10 +319,10 @@ var experimentsByName = map[string]func(*Session) *ExperimentBuilder{
 		}
 	},
 
-	"urlgetter": func(session *Session) *ExperimentBuilder {
-		return &ExperimentBuilder{
-			build: func(config interface{}) *Experiment {
-				return NewExperiment(session, urlgetter.NewExperimentMeasurer(
+	"urlgetter": func(session *Session) *experimentBuilder {
+		return &experimentBuilder{
+			build: func(config interface{}) *experiment {
+				return newExperiment(session, urlgetter.NewExperimentMeasurer(
 					*config.(*urlgetter.Config),
 				))
 			},
@@ -327,10 +331,10 @@ var experimentsByName = map[string]func(*Session) *ExperimentBuilder{
 		}
 	},
 
-	"vanilla_tor": func(session *Session) *ExperimentBuilder {
-		return &ExperimentBuilder{
-			build: func(config interface{}) *Experiment {
-				return NewExperiment(session, vanillator.NewExperimentMeasurer(
+	"vanilla_tor": func(session *Session) *experimentBuilder {
+		return &experimentBuilder{
+			build: func(config interface{}) *experiment {
+				return newExperiment(session, vanillator.NewExperimentMeasurer(
 					*config.(*vanillator.Config),
 				))
 			},
@@ -339,10 +343,10 @@ var experimentsByName = map[string]func(*Session) *ExperimentBuilder{
 		}
 	},
 
-	"web_connectivity": func(session *Session) *ExperimentBuilder {
-		return &ExperimentBuilder{
-			build: func(config interface{}) *Experiment {
-				return NewExperiment(session, webconnectivity.NewExperimentMeasurer(
+	"web_connectivity": func(session *Session) *experimentBuilder {
+		return &experimentBuilder{
+			build: func(config interface{}) *experiment {
+				return newExperiment(session, webconnectivity.NewExperimentMeasurer(
 					*config.(*webconnectivity.Config),
 				))
 			},
@@ -351,10 +355,10 @@ var experimentsByName = map[string]func(*Session) *ExperimentBuilder{
 		}
 	},
 
-	"whatsapp": func(session *Session) *ExperimentBuilder {
-		return &ExperimentBuilder{
-			build: func(config interface{}) *Experiment {
-				return NewExperiment(session, whatsapp.NewExperimentMeasurer(
+	"whatsapp": func(session *Session) *experimentBuilder {
+		return &experimentBuilder{
+			build: func(config interface{}) *experiment {
+				return newExperiment(session, whatsapp.NewExperimentMeasurer(
 					*config.(*whatsapp.Config),
 				))
 			},
diff --git a/internal/engine/experiment.go b/internal/engine/experiment.go
index e271075..be5a21a 100644
--- a/internal/engine/experiment.go
+++ b/internal/engine/experiment.go
@@ -1,5 +1,9 @@
 package engine
 
+//
+// Experiment definition and implementation.
+//
+
 import (
 	"context"
 	"encoding/json"
@@ -23,7 +27,77 @@ func formatTimeNowUTC() string {
 }
 
 // Experiment is an experiment instance.
-type Experiment struct {
+type Experiment interface {
+	// KibiBytesReceived accounts for the KibiBytes received by the experiment.
+	KibiBytesReceived() float64
+
+	// KibiBytesSent is like KibiBytesReceived but for the bytes sent.
+	KibiBytesSent() float64
+
+	// Name returns the experiment name.
+	Name() string
+
+	// GetSummaryKeys returns a data structure containing a
+	// summary of the test keys for ooniprobe.
+	GetSummaryKeys(m *model.Measurement) (any, error)
+
+	// ReportID returns the open report's ID, if we have opened a report
+	// successfully before, or an empty string, otherwise.
+	//
+	// Deprecated: new code should use a Submitter.
+	ReportID() string
+
+	// MeasureAsync runs an async measurement. This operation could post
+	// one or more measurements onto the returned channel. We'll close the
+	// channel when we've emitted all the measurements.
+	//
+	// Arguments:
+	//
+	// - ctx is the context for deadline/cancellation/timeout;
+	//
+	// - input is the input (typically a URL but it could also be
+	// just an endpoint or an empty string for input-less experiments
+	// such as, e.g., ndt7 and dash).
+	//
+	// Return value:
+	//
+	// - on success, channel where to post measurements (the channel
+	// will be closed when done) and nil error;
+	//
+	// - on failure, nil channel and non-nil error.
+	MeasureAsync(ctx context.Context, input string) (<-chan *model.Measurement, error)
+
+	// MeasureWithContext performs a synchronous measurement.
+	//
+	// Return value: strictly either a non-nil measurement and
+	// a nil error or a nil measurement and a non-nil error.
+	//
+	// CAVEAT: while this API is perfectly fine for experiments that
+	// return a single measurement, it will only return the first measurement
+	// when used with an asynchronous experiment.
+	MeasureWithContext(ctx context.Context, input string) (measurement *model.Measurement, err error)
+
+	// SaveMeasurement saves a measurement on the specified file path.
+	//
+	// Deprecated: new code should use a Saver.
+	SaveMeasurement(measurement *model.Measurement, filePath string) error
+
+	// SubmitAndUpdateMeasurementContext submits a measurement and updates the
+	// fields whose value has changed as part of the submission.
+	//
+	// Deprecated: new code should use a Submitter.
+	SubmitAndUpdateMeasurementContext(
+		ctx context.Context, measurement *model.Measurement) error
+
+	// OpenReportContext will open a report using the given context
+	// to possibly limit the lifetime of this operation.
+	//
+	// Deprecated: new code should use a Submitter.
+	OpenReportContext(ctx context.Context) error
+}
+
+// experiment implements Experiment.
+type experiment struct {
 	byteCounter   *bytecounter.Counter
 	callbacks     model.ExperimentCallbacks
 	measurer      model.ExperimentMeasurer
@@ -34,11 +108,9 @@ type Experiment struct {
 	testVersion   string
 }
 
-// NewExperiment creates a new experiment given a measurer. The preferred
-// way to create an experiment is the ExperimentBuilder. Though this function
-// allows the programmer to create a custom, external experiment.
-func NewExperiment(sess *Session, measurer model.ExperimentMeasurer) *Experiment {
-	return &Experiment{
+// newExperiment creates a new experiment given a measurer.
+func newExperiment(sess *Session, measurer model.ExperimentMeasurer) *experiment {
+	return &experiment{
 		byteCounter:   bytecounter.New(),
 		callbacks:     model.NewPrinterCallbacks(sess.Logger()),
 		measurer:      measurer,
@@ -49,64 +121,37 @@ func NewExperiment(sess *Session, measurer model.ExperimentMeasurer) *Experiment
 	}
 }
 
-// KibiBytesReceived accounts for the KibiBytes received by the HTTP clients
-// managed by this session so far, including experiments.
-func (e *Experiment) KibiBytesReceived() float64 {
+// KibiBytesReceived implements Experiment.KibiBytesReceived.
+func (e *experiment) KibiBytesReceived() float64 {
 	return e.byteCounter.KibiBytesReceived()
 }
 
-// KibiBytesSent is like KibiBytesReceived but for the bytes sent.
-func (e *Experiment) KibiBytesSent() float64 {
+// KibiBytesSent implements Experiment.KibiBytesSent.
+func (e *experiment) KibiBytesSent() float64 {
 	return e.byteCounter.KibiBytesSent()
 }
 
-// Name returns the experiment name.
-func (e *Experiment) Name() string {
+// Name implements Experiment.Name.
+func (e *experiment) Name() string {
 	return e.testName
 }
 
-// GetSummaryKeys returns a data structure containing a
-// summary of the test keys for probe-cli.
-func (e *Experiment) GetSummaryKeys(m *model.Measurement) (interface{}, error) {
+// GetSummaryKeys implements Experiment.GetSummaryKeys.
+func (e *experiment) GetSummaryKeys(m *model.Measurement) (interface{}, error) {
 	return e.measurer.GetSummaryKeys(m)
 }
 
-// OpenReport is an idempotent method to open a report. We assume that
-// you have configured the available probe services, either manually or
-// through using the session's MaybeLookupBackends method.
-func (e *Experiment) OpenReport() (err error) {
-	return e.OpenReportContext(context.Background())
-}
-
-// ReportID returns the open reportID, if we have opened a report
-// successfully before, or an empty string, otherwise.
-func (e *Experiment) ReportID() string {
+// ReportID implements Experiment.ReportID.
+func (e *experiment) ReportID() string {
 	if e.report == nil {
 		return ""
 	}
 	return e.report.ReportID()
 }
 
-// Measure performs a measurement with input. We assume that you have
-// configured the available test helpers, either manually or by calling
-// the session's MaybeLookupBackends() method.
-//
-// Return value: strictly either a non-nil measurement and
-// a nil error or a nil measurement and a non-nil error.
-//
-// CAVEAT: while this API is perfectly fine for experiments that
-// return a single measurement, it will only return the first measurement
-// when used with an asynchronous experiment. We plan on eventually
-// migrating all experiments to run in asynchronous fashion.
-//
-// Deprecated: use MeasureWithContext instead, please.
-func (e *Experiment) Measure(input string) (*model.Measurement, error) {
-	return e.MeasureWithContext(context.Background(), input)
-}
-
 // experimentAsyncWrapper makes a sync experiment behave like it was async
 type experimentAsyncWrapper struct {
-	*Experiment
+	*experiment
 }
 
 var _ model.ExperimentMeasurerAsync = &experimentAsyncWrapper{}
@@ -116,9 +161,9 @@ func (eaw *experimentAsyncWrapper) RunAsync(
 	ctx context.Context, sess model.ExperimentSession, input string,
 	callbacks model.ExperimentCallbacks) (<-chan *model.ExperimentAsyncTestKeys, error) {
 	out := make(chan *model.ExperimentAsyncTestKeys)
-	measurement := eaw.Experiment.newMeasurement(input)
+	measurement := eaw.experiment.newMeasurement(input)
 	start := time.Now()
-	err := eaw.Experiment.measurer.Run(ctx, eaw.session, measurement, eaw.callbacks)
+	err := eaw.experiment.measurer.Run(ctx, eaw.session, measurement, eaw.callbacks)
 	stop := time.Now()
 	if err != nil {
 		return nil, err
@@ -136,25 +181,8 @@ func (eaw *experimentAsyncWrapper) RunAsync(
 	return out, nil
 }
 
-// MeasureAsync runs an async measurement. This operation could post
-// one or more measurements onto the returned channel. We'll close the
-// channel when we've emitted all the measurements.
-//
-// Arguments:
-//
-// - ctx is the context for deadline/cancellation/timeout;
-//
-// - input is the input (typically a URL but it could also be
-// just an endpoint or an empty string for input-less experiments
-// such as, e.g., ndt7 and dash).
-//
-// Return value:
-//
-// - on success, channel where to post measurements (the channel
-// will be closed when done) and nil error;
-//
-// - on failure, nil channel and non-nil error.
-func (e *Experiment) MeasureAsync(
+// MeasureAsync implements Experiment.MeasureAsync.
+func (e *experiment) MeasureAsync(
 	ctx context.Context, input string) (<-chan *model.Measurement, error) {
 	err := e.session.MaybeLookupLocationContext(ctx) // this already tracks session bytes
 	if err != nil {
@@ -195,16 +223,8 @@ func (e *Experiment) MeasureAsync(
 	return out, nil
 }
 
-// MeasureWithContext is like Measure but with context.
-//
-// Return value: strictly either a non-nil measurement and
-// a nil error or a nil measurement and a non-nil error.
-//
-// CAVEAT: while this API is perfectly fine for experiments that
-// return a single measurement, it will only return the first measurement
-// when used with an asynchronous experiment. We plan on eventually
-// migrating all experiments to run in asynchronous fashion.
-func (e *Experiment) MeasureWithContext(
+// MeasureWithContext implements Experiment.MeasureWithContext.
+func (e *experiment) MeasureWithContext(
 	ctx context.Context, input string,
 ) (measurement *model.Measurement, err error) {
 	out, err := e.MeasureAsync(ctx, input)
@@ -222,8 +242,8 @@ func (e *Experiment) MeasureWithContext(
 	return
 }
 
-// SaveMeasurement saves a measurement on the specified file path.
-func (e *Experiment) SaveMeasurement(measurement *model.Measurement, filePath string) error {
+// SaveMeasurement implements Experiment.SaveMeasurement.
+func (e *experiment) SaveMeasurement(measurement *model.Measurement, filePath string) error {
 	return e.saveMeasurement(
 		measurement, filePath, json.Marshal, os.OpenFile,
 		func(fp *os.File, b []byte) (int, error) {
@@ -232,15 +252,8 @@ func (e *Experiment) SaveMeasurement(measurement *model.Measurement, filePath st
 	)
 }
 
-// SubmitAndUpdateMeasurement submits a measurement and updates the
-// fields whose value has changed as part of the submission.
-func (e *Experiment) SubmitAndUpdateMeasurement(measurement *model.Measurement) error {
-	return e.SubmitAndUpdateMeasurementContext(context.Background(), measurement)
-}
-
-// SubmitAndUpdateMeasurementContext submits a measurement and updates the
-// fields whose value has changed as part of the submission.
-func (e *Experiment) SubmitAndUpdateMeasurementContext(
+// SubmitAndUpdateMeasurementContext implements Experiment.SubmitAndUpdateMeasurementContext.
+func (e *experiment) SubmitAndUpdateMeasurementContext(
 	ctx context.Context, measurement *model.Measurement) error {
 	if e.report == nil {
 		return errors.New("report is not open")
@@ -249,7 +262,7 @@ func (e *Experiment) SubmitAndUpdateMeasurementContext(
 }
 
 // newMeasurement creates a new measurement for this experiment with the given input.
-func (e *Experiment) newMeasurement(input string) *model.Measurement {
+func (e *experiment) newMeasurement(input string) *model.Measurement {
 	utctimenow := time.Now().UTC()
 	m := &model.Measurement{
 		DataFormatVersion:         probeservices.DefaultDataFormatVersion,
@@ -277,9 +290,8 @@ func (e *Experiment) newMeasurement(input string) *model.Measurement {
 	return m
 }
 
-// OpenReportContext will open a report using the given context
-// to possibly limit the lifetime of this operation.
-func (e *Experiment) OpenReportContext(ctx context.Context) error {
+// OpenReportContext implements Experiment.OpenReportContext.
+func (e *experiment) OpenReportContext(ctx context.Context) error {
 	if e.report != nil {
 		return nil // already open
 	}
@@ -305,7 +317,7 @@ func (e *Experiment) OpenReportContext(ctx context.Context) error {
 	return nil
 }
 
-func (e *Experiment) newReportTemplate() probeservices.ReportTemplate {
+func (e *experiment) newReportTemplate() probeservices.ReportTemplate {
 	return probeservices.ReportTemplate{
 		DataFormatVersion: probeservices.DefaultDataFormatVersion,
 		Format:            probeservices.DefaultFormat,
@@ -319,7 +331,7 @@ func (e *Experiment) newReportTemplate() probeservices.ReportTemplate {
 	}
 }
 
-func (e *Experiment) saveMeasurement(
+func (e *experiment) saveMeasurement(
 	measurement *model.Measurement, filePath string,
 	marshal func(v interface{}) ([]byte, error),
 	openFile func(name string, flag int, perm os.FileMode) (*os.File, error),
diff --git a/internal/engine/experiment_integration_test.go b/internal/engine/experiment_integration_test.go
index 2114d6d..dd91b7f 100644
--- a/internal/engine/experiment_integration_test.go
+++ b/internal/engine/experiment_integration_test.go
@@ -162,7 +162,7 @@ func TestSetCallbacks(t *testing.T) {
 	}
 	register := &registerCallbacksCalled{}
 	builder.SetCallbacks(register)
-	if _, err := builder.NewExperiment().Measure(""); err != nil {
+	if _, err := builder.NewExperiment().MeasureWithContext(context.Background(), ""); err != nil {
 		t.Fatal(err)
 	}
 	if register.onProgressCalled == false {
@@ -206,7 +206,7 @@ func TestMeasurementFailure(t *testing.T) {
 	if err := builder.SetOptionAny("ReturnError", true); err != nil {
 		t.Fatal(err)
 	}
-	measurement, err := builder.NewExperiment().Measure("")
+	measurement, err := builder.NewExperiment().MeasureWithContext(context.Background(), "")
 	if err == nil {
 		t.Fatal("expected an error here")
 	}
@@ -288,7 +288,7 @@ func TestUseOptions(t *testing.T) {
 	if err := builder.SetOptionAny("Message", "antani"); err != nil {
 		t.Fatal("cannot set Message field")
 	}
-	config := builder.config.(*example.Config)
+	config := builder.(*experimentBuilder).config.(*example.Config)
 	if config.ReturnError != true {
 		t.Fatal("config.ReturnError was not changed")
 	}
@@ -313,15 +313,16 @@ func TestRunHHFM(t *testing.T) {
 	runexperimentflow(t, builder.NewExperiment(), "")
 }
 
-func runexperimentflow(t *testing.T, experiment *Experiment, input string) {
-	err := experiment.OpenReport()
+func runexperimentflow(t *testing.T, experiment Experiment, input string) {
+	ctx := context.Background()
+	err := experiment.OpenReportContext(ctx)
 	if err != nil {
 		t.Fatal(err)
 	}
 	if experiment.ReportID() == "" {
 		t.Fatal("reportID should not be empty here")
 	}
-	measurement, err := experiment.Measure(input)
+	measurement, err := experiment.MeasureWithContext(ctx, input)
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -335,7 +336,7 @@ func runexperimentflow(t *testing.T, experiment *Experiment, input string) {
 	if data == nil {
 		t.Fatal("data is nil")
 	}
-	err = experiment.SubmitAndUpdateMeasurement(measurement)
+	err = experiment.SubmitAndUpdateMeasurementContext(ctx, measurement)
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -364,14 +365,14 @@ func TestSaveMeasurementErrors(t *testing.T) {
 	if err != nil {
 		t.Fatal(err)
 	}
-	exp := builder.NewExperiment()
+	exp := builder.NewExperiment().(*experiment)
 	dirname, err := ioutil.TempDir("", "ooniprobe-engine-save-measurement")
 	if err != nil {
 		t.Fatal(err)
 	}
 	filename := filepath.Join(dirname, "report.jsonl")
 	m := new(model.Measurement)
-	err = exp.SaveMeasurementEx(
+	err = exp.saveMeasurement(
 		m, filename, func(v interface{}) ([]byte, error) {
 			return nil, errors.New("mocked error")
 		}, os.OpenFile, func(fp *os.File, b []byte) (int, error) {
@@ -381,7 +382,7 @@ func TestSaveMeasurementErrors(t *testing.T) {
 	if err == nil {
 		t.Fatal("expected an error here")
 	}
-	err = exp.SaveMeasurementEx(
+	err = exp.saveMeasurement(
 		m, filename, json.Marshal,
 		func(name string, flag int, perm os.FileMode) (*os.File, error) {
 			return nil, errors.New("mocked error")
@@ -392,7 +393,7 @@ func TestSaveMeasurementErrors(t *testing.T) {
 	if err == nil {
 		t.Fatal("expected an error here")
 	}
-	err = exp.SaveMeasurementEx(
+	err = exp.saveMeasurement(
 		m, filename, json.Marshal, os.OpenFile,
 		func(fp *os.File, b []byte) (int, error) {
 			return 0, errors.New("mocked error")
@@ -417,10 +418,11 @@ func TestOpenReportIdempotent(t *testing.T) {
 	if exp.ReportID() != "" {
 		t.Fatal("unexpected initial report ID")
 	}
-	if err := exp.SubmitAndUpdateMeasurement(&model.Measurement{}); err == nil {
+	ctx := context.Background()
+	if err := exp.SubmitAndUpdateMeasurementContext(ctx, &model.Measurement{}); err == nil {
 		t.Fatal("we should not be able to submit before OpenReport")
 	}
-	err = exp.OpenReport()
+	err = exp.OpenReportContext(ctx)
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -428,7 +430,7 @@ func TestOpenReportIdempotent(t *testing.T) {
 	if rid == "" {
 		t.Fatal("invalid report ID")
 	}
-	err = exp.OpenReport()
+	err = exp.OpenReportContext(ctx)
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -453,12 +455,12 @@ func TestOpenReportFailure(t *testing.T) {
 	if err != nil {
 		t.Fatal(err)
 	}
-	exp := builder.NewExperiment()
+	exp := builder.NewExperiment().(*experiment)
 	exp.session.selectedProbeService = &model.OOAPIService{
 		Address: server.URL,
 		Type:    "https",
 	}
-	err = exp.OpenReport()
+	err = exp.OpenReportContext(context.Background())
 	if !strings.HasPrefix(err.Error(), "httpx: request failed") {
 		t.Fatal("not the error we expected")
 	}
@@ -474,12 +476,12 @@ func TestOpenReportNewClientFailure(t *testing.T) {
 	if err != nil {
 		t.Fatal(err)
 	}
-	exp := builder.NewExperiment()
+	exp := builder.NewExperiment().(*experiment)
 	exp.session.selectedProbeService = &model.OOAPIService{
 		Address: "antani:///",
 		Type:    "antani",
 	}
-	err = exp.OpenReport()
+	err = exp.OpenReportContext(context.Background())
 	if err.Error() != "probe services: unsupported endpoint type" {
 		t.Fatal(err)
 	}
@@ -497,7 +499,7 @@ func TestSubmitAndUpdateMeasurementWithClosedReport(t *testing.T) {
 	}
 	exp := builder.NewExperiment()
 	m := new(model.Measurement)
-	err = exp.SubmitAndUpdateMeasurement(m)
+	err = exp.SubmitAndUpdateMeasurementContext(context.Background(), m)
 	if err == nil {
 		t.Fatal("expected an error here")
 	}
@@ -509,7 +511,7 @@ func TestMeasureLookupLocationFailure(t *testing.T) {
 	}
 	sess := newSessionForTestingNoLookups(t)
 	defer sess.Close()
-	exp := NewExperiment(sess, new(antaniMeasurer))
+	exp := newExperiment(sess, new(antaniMeasurer))
 	ctx, cancel := context.WithCancel(context.Background())
 	cancel() // so we fail immediately
 	if _, err := exp.MeasureWithContext(ctx, "xx"); err == nil {
@@ -529,8 +531,8 @@ func TestOpenReportNonHTTPS(t *testing.T) {
 			Type:    "mascetti",
 		},
 	}
-	exp := NewExperiment(sess, new(antaniMeasurer))
-	if err := exp.OpenReport(); err == nil {
+	exp := newExperiment(sess, new(antaniMeasurer))
+	if err := exp.OpenReportContext(context.Background()); err == nil {
 		t.Fatal("expected an error here")
 	}
 }
diff --git a/internal/engine/experiment_internal_test.go b/internal/engine/experiment_internal_test.go
deleted file mode 100644
index 6adc11c..0000000
--- a/internal/engine/experiment_internal_test.go
+++ /dev/null
@@ -1,16 +0,0 @@
-package engine
-
-import (
-	"os"
-
-	"github.com/ooni/probe-cli/v3/internal/model"
-)
-
-func (e *Experiment) SaveMeasurementEx(
-	measurement *model.Measurement, filePath string,
-	marshal func(v interface{}) ([]byte, error),
-	openFile func(name string, flag int, perm os.FileMode) (*os.File, error),
-	write func(fp *os.File, b []byte) (n int, err error),
-) error {
-	return e.saveMeasurement(measurement, filePath, marshal, openFile, write)
-}
diff --git a/internal/engine/experiment_test.go b/internal/engine/experiment_test.go
index fe126d7..7860d57 100644
--- a/internal/engine/experiment_test.go
+++ b/internal/engine/experiment_test.go
@@ -14,7 +14,7 @@ func TestExperimentHonoursSharingDefaults(t *testing.T) {
 		if err != nil {
 			t.Fatal(err)
 		}
-		exp := builder.NewExperiment()
+		exp := builder.NewExperiment().(*experiment)
 		return exp.newMeasurement("")
 	}
 	type spec struct {
diff --git a/internal/engine/experimentbuilder.go b/internal/engine/experimentbuilder.go
index 2b5f651..64dc7c4 100644
--- a/internal/engine/experimentbuilder.go
+++ b/internal/engine/experimentbuilder.go
@@ -1,5 +1,9 @@
 package engine
 
+//
+// ExperimentBuilder definition and implementation
+//
+
 import (
 	"errors"
 	"fmt"
@@ -42,23 +46,60 @@ const (
 	InputOrStaticDefault = InputPolicy("or_static_default")
 )
 
-// ExperimentBuilder is an experiment builder.
-type ExperimentBuilder struct {
-	build         func(interface{}) *Experiment
-	callbacks     model.ExperimentCallbacks
-	config        interface{}
-	inputPolicy   InputPolicy
+// ExperimentBuilder builds an experiment.
+type ExperimentBuilder interface {
+	// Interruptible tells you whether this is an interruptible experiment. This kind
+	// of experiments (e.g. ndt7) may be interrupted mid way.
+	Interruptible() bool
+
+	// InputPolicy returns the experiment input policy.
+	InputPolicy() InputPolicy
+
+	// Options returns information about the experiment's options.
+	Options() (map[string]OptionInfo, error)
+
+	// SetOptionAny sets an option whose value is an any value. We will use reasonable
+	// heuristics to convert the any value to the proper type of the field whose name is
+	// contained by the key variable. If we cannot convert the provided any value to
+	// the proper type, then this function returns an error.
+	SetOptionAny(key string, value any) error
+
+	// SetOptionsAny sets options from a map[string]any. See the documentation of
+	// the SetOptionAny method for more information.
+	SetOptionsAny(options map[string]any) error
+
+	// SetCallbacks sets the experiment's interactive callbacks.
+	SetCallbacks(callbacks model.ExperimentCallbacks)
+
+	// NewExperiment creates the experiment instance.
+	NewExperiment() Experiment
+}
+
+// experimentBuilder implements ExperimentBuilder.
+type experimentBuilder struct {
+	// build is the constructor that build an experiment with the given config.
+	build func(config interface{}) *experiment
+
+	// callbacks contains callbacks for the new experiment.
+	callbacks model.ExperimentCallbacks
+
+	// config contains the experiment's config.
+	config interface{}
+
+	// inputPolicy contains the experiment's InputPolicy.
+	inputPolicy InputPolicy
+
+	// interruptible indicates whether the experiment is interruptible.
 	interruptible bool
 }
 
-// Interruptible tells you whether this is an interruptible experiment. This kind
-// of experiments (e.g. ndt7) may be interrupted mid way.
-func (b *ExperimentBuilder) Interruptible() bool {
+// Interruptible implements ExperimentBuilder.Interruptible.
+func (b *experimentBuilder) Interruptible() bool {
 	return b.interruptible
 }
 
-// InputPolicy returns the experiment input policy
-func (b *ExperimentBuilder) InputPolicy() InputPolicy {
+// InputPolicy implements ExperimentBuilder.InputPolicy.
+func (b *experimentBuilder) InputPolicy() InputPolicy {
 	return b.inputPolicy
 }
 
@@ -96,8 +137,8 @@ var (
 	ErrUnsupportedOptionType = errors.New("unsupported option type")
 )
 
-// Options returns info about all options
-func (b *ExperimentBuilder) Options() (map[string]OptionInfo, error) {
+// Options implements ExperimentBuilder.Options.
+func (b *experimentBuilder) Options() (map[string]OptionInfo, error) {
 	result := make(map[string]OptionInfo)
 	ptrinfo := reflect.ValueOf(b.config)
 	if ptrinfo.Kind() != reflect.Ptr {
@@ -118,7 +159,7 @@ func (b *ExperimentBuilder) Options() (map[string]OptionInfo, error) {
 }
 
 // setOptionBool sets a bool option.
-func (b *ExperimentBuilder) setOptionBool(field reflect.Value, value any) error {
+func (b *experimentBuilder) setOptionBool(field reflect.Value, value any) error {
 	switch v := value.(type) {
 	case bool:
 		field.SetBool(v)
@@ -135,7 +176,7 @@ func (b *ExperimentBuilder) setOptionBool(field reflect.Value, value any) error
 }
 
 // setOptionInt sets an int option
-func (b *ExperimentBuilder) setOptionInt(field reflect.Value, value any) error {
+func (b *experimentBuilder) setOptionInt(field reflect.Value, value any) error {
 	switch v := value.(type) {
 	case int64:
 		field.SetInt(v)
@@ -165,7 +206,7 @@ func (b *ExperimentBuilder) setOptionInt(field reflect.Value, value any) error {
 }
 
 // setOptionString sets a string option
-func (b *ExperimentBuilder) setOptionString(field reflect.Value, value any) error {
+func (b *experimentBuilder) setOptionString(field reflect.Value, value any) error {
 	switch v := value.(type) {
 	case string:
 		field.SetString(v)
@@ -175,11 +216,8 @@ func (b *ExperimentBuilder) setOptionString(field reflect.Value, value any) erro
 	}
 }
 
-// SetOptionAny sets an option whose value is an any value. We will use reasonable
-// heuristics to convert the any value to the proper type of the field whose name is
-// contained by the key variable. If we cannot convert the provided any value to
-// the proper type, then this function returns an error.
-func (b *ExperimentBuilder) SetOptionAny(key string, value any) error {
+// SetOptionAny implements ExperimentBuilder.SetOptionAny.
+func (b *experimentBuilder) SetOptionAny(key string, value any) error {
 	field, err := b.fieldbyname(b.config, key)
 	if err != nil {
 		return err
@@ -196,9 +234,8 @@ func (b *ExperimentBuilder) SetOptionAny(key string, value any) error {
 	}
 }
 
-// SetOptionsAny sets options from a map[string]any. See the documentation of
-// the SetOptionAny function for more information.
-func (b *ExperimentBuilder) SetOptionsAny(options map[string]any) error {
+// SetOptionsAny implements ExperimentBuilder.SetOptionsAny.
+func (b *experimentBuilder) SetOptionsAny(options map[string]any) error {
 	for key, value := range options {
 		if err := b.SetOptionAny(key, value); err != nil {
 			return err
@@ -207,12 +244,13 @@ func (b *ExperimentBuilder) SetOptionsAny(options map[string]any) error {
 	return nil
 }
 
-// SetCallbacks sets the interactive callbacks
-func (b *ExperimentBuilder) SetCallbacks(callbacks model.ExperimentCallbacks) {
+// SetCallbacks implements ExperimentBuilder.SetCallbacks.
+func (b *experimentBuilder) SetCallbacks(callbacks model.ExperimentCallbacks) {
 	b.callbacks = callbacks
 }
 
-func (b *ExperimentBuilder) fieldbyname(v interface{}, key string) (reflect.Value, error) {
+// fieldbyname return v's field whose name is equal to the given key.
+func (b *experimentBuilder) fieldbyname(v interface{}, key string) (reflect.Value, error) {
 	// See https://stackoverflow.com/a/6396678/4354461
 	ptrinfo := reflect.ValueOf(v)
 	if ptrinfo.Kind() != reflect.Ptr {
@@ -230,7 +268,7 @@ func (b *ExperimentBuilder) fieldbyname(v interface{}, key string) (reflect.Valu
 }
 
 // NewExperiment creates the experiment
-func (b *ExperimentBuilder) NewExperiment() *Experiment {
+func (b *experimentBuilder) NewExperiment() Experiment {
 	experiment := b.build(b.config)
 	experiment.callbacks = b.callbacks
 	return experiment
@@ -255,7 +293,8 @@ func canonicalizeExperimentName(name string) string {
 	return name
 }
 
-func newExperimentBuilder(session *Session, name string) (*ExperimentBuilder, error) {
+// newExperimentBuilder creates a new experimentBuilder instance.
+func newExperimentBuilder(session *Session, name string) (*experimentBuilder, error) {
 	factory := experimentsByName[canonicalizeExperimentName(name)]
 	if factory == nil {
 		return nil, fmt.Errorf("no such experiment: %s", name)
diff --git a/internal/engine/experimentbuilder_test.go b/internal/engine/experimentbuilder_test.go
index 39a439e..9197032 100644
--- a/internal/engine/experimentbuilder_test.go
+++ b/internal/engine/experimentbuilder_test.go
@@ -16,7 +16,7 @@ type fakeExperimentConfig struct {
 
 func TestExperimentBuilderOptions(t *testing.T) {
 	t.Run("when config is not a pointer", func(t *testing.T) {
-		b := &ExperimentBuilder{
+		b := &experimentBuilder{
 			config: 17,
 		}
 		options, err := b.Options()
@@ -30,7 +30,7 @@ func TestExperimentBuilderOptions(t *testing.T) {
 
 	t.Run("when config is not a struct", func(t *testing.T) {
 		number := 17
-		b := &ExperimentBuilder{
+		b := &experimentBuilder{
 			config: &number,
 		}
 		options, err := b.Options()
@@ -44,7 +44,7 @@ func TestExperimentBuilderOptions(t *testing.T) {
 
 	t.Run("when config is a pointer to struct", func(t *testing.T) {
 		config := &fakeExperimentConfig{}
-		b := &ExperimentBuilder{
+		b := &experimentBuilder{
 			config: config,
 		}
 		options, err := b.Options()
@@ -291,7 +291,7 @@ func TestExperimentBuilderSetOptionAny(t *testing.T) {
 	for _, input := range inputs {
 		t.Run(input.TestCaseName, func(t *testing.T) {
 			ec := input.InitialConfig
-			b := &ExperimentBuilder{config: ec}
+			b := &experimentBuilder{config: ec}
 			err := b.SetOptionAny(input.FieldName, input.FieldValue)
 			if !errors.Is(err, input.ExpectErr) {
 				t.Fatal(err)
@@ -304,7 +304,7 @@ func TestExperimentBuilderSetOptionAny(t *testing.T) {
 }
 
 func TestExperimentBuilderSetOptionsAny(t *testing.T) {
-	b := &ExperimentBuilder{config: &fakeExperimentConfig{}}
+	b := &experimentBuilder{config: &fakeExperimentConfig{}}
 
 	t.Run("we correctly handle an empty map", func(t *testing.T) {
 		if err := b.SetOptionsAny(nil); err != nil {
@@ -314,7 +314,7 @@ func TestExperimentBuilderSetOptionsAny(t *testing.T) {
 
 	t.Run("we correctly handle a map containing options", func(t *testing.T) {
 		f := &fakeExperimentConfig{}
-		privateb := &ExperimentBuilder{config: f}
+		privateb := &experimentBuilder{config: f}
 		opts := map[string]any{
 			"String": "yoloyolo",
 			"Value":  "174",
diff --git a/internal/engine/session.go b/internal/engine/session.go
index ee7aa70..5bdc969 100644
--- a/internal/engine/session.go
+++ b/internal/engine/session.go
@@ -390,7 +390,7 @@ var ErrAlreadyUsingProxy = errors.New(
 // NewExperimentBuilder returns a new experiment builder
 // for the experiment with the given name, or an error if
 // there's no such experiment with the given name
-func (s *Session) NewExperimentBuilder(name string) (*ExperimentBuilder, error) {
+func (s *Session) NewExperimentBuilder(name string) (ExperimentBuilder, error) {
 	return newExperimentBuilder(s, name)
 }
 
diff --git a/pkg/oonimkall/experiment.go b/pkg/oonimkall/experiment.go
index 117a3d0..4f7077c 100644
--- a/pkg/oonimkall/experiment.go
+++ b/pkg/oonimkall/experiment.go
@@ -67,7 +67,7 @@ type experimentBuilder interface {
 
 // experimentBuilderWrapper wraps *ExperimentBuilder
 type experimentBuilderWrapper struct {
-	eb *engine.ExperimentBuilder
+	eb engine.ExperimentBuilder
 }
 
 // newExperiment implements experimentBuilder.newExperiment
diff --git a/pkg/oonimkall/tasksession.go b/pkg/oonimkall/tasksession.go
index 1a785d9..86d2e08 100644
--- a/pkg/oonimkall/tasksession.go
+++ b/pkg/oonimkall/tasksession.go
@@ -59,7 +59,7 @@ func (sess *taskSessionEngine) NewExperimentBuilderByName(
 // taskExperimentBuilderEngine wraps ./internal/engine's
 // ExperimentBuilder type.
 type taskExperimentBuilderEngine struct {
-	*engine.ExperimentBuilder
+	engine.ExperimentBuilder
 }
 
 var _ taskExperimentBuilder = &taskExperimentBuilderEngine{}
@@ -72,7 +72,7 @@ func (b *taskExperimentBuilderEngine) NewExperimentInstance() taskExperiment {
 
 // taskExperimentEngine wraps ./internal/engine's Experiment.
 type taskExperimentEngine struct {
-	*engine.Experiment
+	engine.Experiment
 }
 
 var _ taskExperiment = &taskExperimentEngine{}