M2: controller async coach with generation guard and ephemeral state

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

internal/session/session_test.go

@@ -1,10 +1,13 @@
 package session
 
 import (
+	"context"
+	"errors"
 	"path/filepath"
 	"testing"
 	"time"
 
+	"antidrift/internal/ai"
 	"antidrift/internal/domain"
 	"antidrift/internal/evidence"
 	"antidrift/internal/store"
@@ -235,3 +238,117 @@ func TestEndWritesAuditSummary(t *testing.T) {
 		t.Fatalf("chain should verify: %v", err)
 	}
 }
+
+type fakeCoach struct {
+	prop ai.Proposal
+	err  error
+	gate chan struct{} // if non-nil, Coach blocks until it receives
+}
+
+func (f *fakeCoach) Coach(ctx context.Context, intent string) (ai.Proposal, error) {
+	if f.gate != nil {
+		<-f.gate
+	}
+	return f.prop, f.err
+}
+
+// waitCoachStatus polls until the coach view reaches want, or fails after 2s.
+func waitCoachStatus(t *testing.T, c *Controller, want string) State {
+	t.Helper()
+	deadline := time.Now().Add(2 * time.Second)
+	for time.Now().Before(deadline) {
+		st := c.State()
+		if st.Coach != nil && st.Coach.Status == want {
+			return st
+		}
+		time.Sleep(5 * time.Millisecond)
+	}
+	t.Fatalf("coach status never reached %q (last: %+v)", want, c.State().Coach)
+	return State{}
+}
+
+func TestRequestCoachReady(t *testing.T) {
+	c, _ := newTestController(t)
+	_ = c.EnterPlanning()
+	c.SetCoach(&fakeCoach{prop: ai.Proposal{NextAction: "Do X", SuccessCondition: "X done", TimeboxSecs: 1500}})
+	if err := c.RequestCoach("do x"); err != nil {
+		t.Fatalf("request coach: %v", err)
+	}
+	st := waitCoachStatus(t, c, "ready")
+	if st.Coach.Proposal == nil || st.Coach.Proposal.NextAction != "Do X" || st.Coach.Proposal.TimeboxSecs != 1500 {
+		t.Fatalf("ready proposal wrong: %+v", st.Coach)
+	}
+}
+
+func TestRequestCoachError(t *testing.T) {
+	c, _ := newTestController(t)
+	_ = c.EnterPlanning()
+	c.SetCoach(&fakeCoach{err: errors.New("backend down")})
+	if err := c.RequestCoach("x"); err != nil {
+		t.Fatalf("request: %v", err)
+	}
+	st := waitCoachStatus(t, c, "error")
+	if st.Coach.Error == "" {
+		t.Fatal("error status should carry a message")
+	}
+}
+
+func TestRequestCoachUnavailable(t *testing.T) {
+	c, _ := newTestController(t)
+	_ = c.EnterPlanning()
+	if err := c.RequestCoach("x"); err != nil {
+		t.Fatalf("nil coach must degrade, not error: %v", err)
+	}
+	st := c.State()
+	if st.Coach == nil || st.Coach.Status != "error" {
+		t.Fatalf("want error status for nil coach, got %+v", st.Coach)
+	}
+}
+
+func TestRequestCoachWrongState(t *testing.T) {
+	c, _ := newTestController(t)
+	c.SetCoach(&fakeCoach{prop: ai.Proposal{NextAction: "x", SuccessCondition: "y", TimeboxSecs: 60}})
+	if err := c.RequestCoach("x"); err == nil {
+		t.Fatal("coaching from Locked should error")
+	}
+	if c.State().Coach != nil {
+		t.Fatal("no coach view outside planning")
+	}
+}
+
+func TestRequestCoachStaleResultDiscarded(t *testing.T) {
+	c, _ := newTestController(t)
+	_ = c.EnterPlanning()
+
+	slow := &fakeCoach{prop: ai.Proposal{NextAction: "OLD", SuccessCondition: "old", TimeboxSecs: 60}, gate: make(chan struct{})}
+	c.SetCoach(slow)
+	_ = c.RequestCoach("first") // gen1 pending, goroutine blocks on gate
+
+	fast := &fakeCoach{prop: ai.Proposal{NextAction: "NEW", SuccessCondition: "new", TimeboxSecs: 120}}
+	c.SetCoach(fast)
+	_ = c.RequestCoach("second") // gen2 -> ready NEW
+	st := waitCoachStatus(t, c, "ready")
+	if st.Coach.Proposal.NextAction != "NEW" {
+		t.Fatalf("expected NEW, got %+v", st.Coach.Proposal)
+	}
+
+	close(slow.gate) // release gen1; it must be discarded
+	time.Sleep(50 * time.Millisecond)
+	if got := c.State().Coach.Proposal.NextAction; got != "NEW" {
+		t.Fatalf("stale gen1 overwrote state: %q", got)
+	}
+}
+
+func TestLeavingPlanningClearsCoach(t *testing.T) {
+	c, _ := newTestController(t)
+	_ = c.EnterPlanning()
+	c.SetCoach(&fakeCoach{prop: ai.Proposal{NextAction: "x", SuccessCondition: "y", TimeboxSecs: 60}})
+	_ = c.RequestCoach("x")
+	waitCoachStatus(t, c, "ready")
+	if err := c.StartManualCommitment("a", "b", 25*time.Minute); err != nil {
+		t.Fatalf("start: %v", err)
+	}
+	if c.State().Coach != nil {
+		t.Fatal("coach view must be gone once Active")
+	}
+}