diff --git a/docs/changes/unreleased/2047-mac-test-assumptions.md b/docs/changes/unreleased/2047-mac-test-assumptions.md
new file mode 100644
index 0000000000..5eb3b81649
--- /dev/null
+++ b/docs/changes/unreleased/2047-mac-test-assumptions.md
@@ -0,0 +1,13 @@
+---
+kind: internal
+title: The last tests that assumed Linux pass on a Mac
+pr: 2047
+surface: [build]
+invalidates: []
+---
+
+The cellstore socket fixtures assumed a short temporary folder that is not
+reached through a link; on a Mac it is long and `/tmp` is `/private/tmp`.
+The remote stamp answers assumed Linux's device and inode widths. Their
+expectations now hold on both systems; no product behaviour changed. The
+other Mac assumptions this branch first fixed reached app/v3 through #2099.
diff --git a/internal/cellstore/daemon_test.go b/internal/cellstore/daemon_test.go
index 70f43cb173..fc441a9ceb 100644
--- a/internal/cellstore/daemon_test.go
+++ b/internal/cellstore/daemon_test.go
@@ -103,6 +103,10 @@ func TestDaemonOfANonEngineIsUnavailable(t *testing.T) {
 
 // Two engine builds never share a daemon: the socket is named after the binary.
 func TestSocketIsKeyedToTheEngineBinary(t *testing.T) {
+	// Keep the home address short enough to assert its build-named basename too.
+	if runtime.GOOS != "windows" {
+		t.Setenv("TMPDIR", "/tmp")
+	}
 	base := filepath.Dir(testSocket(t))
 	t.Setenv("CODEAF_HOME", base)
 	t.Setenv("LOCALAPPDATA", base)
diff --git a/internal/cellstore/socket_regression_unix_test.go b/internal/cellstore/socket_regression_unix_test.go
index f34ab23a98..b24ee174ed 100644
--- a/internal/cellstore/socket_regression_unix_test.go
+++ b/internal/cellstore/socket_regression_unix_test.go
@@ -23,6 +23,13 @@ import (
 // The lane-local temp base models a shared /tmp without involving another user.
 func TestR9UnixShortSocketRejectsPreclaimedDirectory(t *testing.T) {
 	t.Setenv("XDG_RUNTIME_DIR", "")
+	// A short private temp base keeps this fixture in its own fallback lane on macOS.
+	base, err := os.MkdirTemp("/tmp", "r9-temp-")
+	if err != nil {
+		t.Fatal(err)
+	}
+	t.Cleanup(func() { _ = os.RemoveAll(base) })
+	t.Setenv("TMPDIR", base)
 	for _, kind := range []string{"writable-directory", "symlink"} {
 		t.Run(kind, func(t *testing.T) {
 			bin := "/engine/furrow-review-" + kind
@@ -33,7 +40,7 @@ func TestR9UnixShortSocketRejectsPreclaimedDirectory(t *testing.T) {
 			if err := os.Remove(dir); err != nil && !os.IsNotExist(err) {
 				t.Fatal(err)
 			}
-			if !strings.HasPrefix(dir, os.TempDir()+string(filepath.Separator)) || len(socket) >= maxSocketBytes {
+			if !strings.HasPrefix(dir, filepath.Clean(os.TempDir())+string(filepath.Separator)) || len(socket) >= maxSocketBytes {
 				t.Fatalf("C7: fixture did not select its lane-local short fallback: %q", socket)
 			}
 			if _, err := os.Lstat(dir); !os.IsNotExist(err) {
@@ -158,6 +165,11 @@ func TestR9UnixShortSocketOrder(t *testing.T) {
 		t.Fatal(err)
 	}
 	t.Cleanup(func() { _ = os.RemoveAll(login) })
+	// The home address uses the physical path, including macOS's /private/tmp.
+	login, err = filepath.EvalSymlinks(login)
+	if err != nil {
+		t.Fatal(err)
+	}
 	t.Setenv("CODEAF_HOME", login)
 	t.Setenv("XDG_RUNTIME_DIR", runtime)
 	bin := "/engine/furrow-review-runtime"
diff --git a/internal/remote/teams_test.go b/internal/remote/teams_test.go
index 548188aff5..7fcd25ea42 100644
--- a/internal/remote/teams_test.go
+++ b/internal/remote/teams_test.go
@@ -51,8 +51,10 @@ func TestTheTeamsDoorsCrossFromTheEnginesProfile(t *testing.T) {
 	if err != nil || !same.Same || same.Teams != nil {
 		t.Fatalf("a read at the held stamp: %+v, %v", same, err)
 	}
-	if raw, _ := json.Marshal(same); len(raw) > 64 {
-		t.Fatalf("an unchanged answer is %d bytes: %s", len(raw), raw)
+	// Device and inode widths vary by filesystem; only the stamp and flag cross.
+	stamp, _ := json.Marshal(wrote.Stamp)
+	if raw, _ := json.Marshal(same); string(raw) != `{"stamp":`+string(stamp)+`,"same":true}` {
+		t.Fatalf("an unchanged answer must carry only the held stamp and same: %s", raw)
 	}
 
 	if err := teamstore.AppendTraffic(dir, "0a0a0a0a0a0a", teamstore.Entry{Kind: teamstore.KindNote,
@@ -67,8 +69,9 @@ func TestTheTeamsDoorsCrossFromTheEnginesProfile(t *testing.T) {
 	if err != nil || len(quiet.Entries) != 0 {
 		t.Fatalf("a quiet log after the cursor: %+v, %v", quiet, err)
 	}
-	if raw, _ := json.Marshal(quiet); len(raw) > 64 {
-		t.Fatalf("a quiet Traffic answer is %d bytes: %s", len(raw), raw)
+	stamp, _ = json.Marshal(got.Stamp)
+	if raw, _ := json.Marshal(quiet); string(raw) != `{"stamp":`+string(stamp)+`}` {
+		t.Fatalf("a quiet Traffic answer must carry only the held stamp: %s", raw)
 	}
 	if _, err := loop.Client.TeamsTraffic("../escape", "", 1); err == nil {
 		t.Fatal("a team id that is a path was read")