diff --git a/workspace-server/internal/handlers/workspace_broadcast_test.go b/workspace-server/internal/handlers/workspace_broadcast_test.go
new file mode 100644
index 000000000..789df7cc3
--- /dev/null
+++ b/workspace-server/internal/handlers/workspace_broadcast_test.go
@@ -0,0 +1,410 @@
+package handlers
+
+import (
+	"bytes"
+	"context"
+	"database/sql"
+	"net/http"
+	"net/http/httptest"
+	"testing"
+
+	"github.com/DATA-DOG/go-sqlmock"
+	"github.com/Molecule-AI/molecule-monorepo/platform/internal/db"
+	"github.com/Molecule-AI/molecule-monorepo/platform/internal/events"
+	"github.com/Molecule-AI/molecule-monorepo/platform/internal/ws"
+	"github.com/gin-gonic/gin"
+)
+
+// setupBroadcastDB uses QueryMatcherEqual so SQL strings with quoted literals
+// (e.g. status != 'removed') are compared verbatim, not as regex.
+func setupBroadcastDB(t *testing.T) sqlmock.Sqlmock {
+	t.Helper()
+	mockDB, mock, err := sqlmock.New(sqlmock.QueryMatcherOption(sqlmock.QueryMatcherEqual))
+	if err != nil {
+		t.Fatalf("failed to create sqlmock: %v", err)
+	}
+	prevDB := db.DB
+	db.DB = mockDB
+	t.Cleanup(func() { db.DB = prevDB; mockDB.Close() })
+	return mock
+}
+
+// broadcastTestUUID is a properly formatted test UUID.
+const broadcastTestUUID = "bbbbbbbb-0001-0001-0001-000000000001"
+
+// buildBroadcastCtx creates a gin.Context wired for POST /workspaces/:id/broadcast.
+func buildBroadcastCtx(id, body string) (*gin.Context, *httptest.ResponseRecorder) {
+	w := httptest.NewRecorder()
+	c, _ := gin.CreateTestContext(w)
+	req := httptest.NewRequest(http.MethodPost, "/workspaces/"+id+"/broadcast", bytes.NewBufferString(body))
+	req.Header.Set("Content-Type", "application/json")
+	c.Request = req.WithContext(context.Background())
+	c.Params = gin.Params{{Key: "id", Value: id}}
+	return c, w
+}
+
+// ─── Pure function ─────────────────────────────────────────────────────────────
+
+func TestBroadcastTruncate(t *testing.T) {
+	tests := []struct {
+		name string
+		s    string
+		max  int
+		want string
+	}{
+		{"empty string", "", 10, ""},
+		{"under limit", "hello", 10, "hello"},
+		{"exactly at limit", "hello", 5, "hello"},
+		{"over limit", "hello world", 5, "hello…"},
+		{"unicode over limit", "こんにちは世界", 5, "こんにちは…"},
+		{"ascii over limit", "abcdefghij", 5, "abcde…"},
+	}
+	for _, tc := range tests {
+		t.Run(tc.name, func(t *testing.T) {
+			got := broadcastTruncate(tc.s, tc.max)
+			if got != tc.want {
+				t.Errorf("broadcastTruncate(%q, %d) = %q; want %q", tc.s, tc.max, got, tc.want)
+			}
+		})
+	}
+}
+
+// ─── Validation ────────────────────────────────────────────────────────────────
+
+func TestBroadcast_InvalidWorkspaceID(t *testing.T) {
+	c, w := buildBroadcastCtx("not-a-uuid", `{"message":"hello"}`)
+	handler := NewBroadcastHandler(events.NewBroadcaster(ws.NewHub(nil)))
+	handler.Broadcast(c)
+	if w.Code != http.StatusBadRequest {
+		t.Errorf("want 400, got %d: %s", w.Code, w.Body.String())
+	}
+}
+
+func TestBroadcast_MissingMessage(t *testing.T) {
+	mock := setupBroadcastDB(t)
+	c, w := buildBroadcastCtx(broadcastTestUUID, `{}`)
+
+	handler := NewBroadcastHandler(events.NewBroadcaster(ws.NewHub(nil)))
+	handler.Broadcast(c)
+
+	if w.Code != http.StatusBadRequest {
+		t.Errorf("want 400, got %d: %s", w.Code, w.Body.String())
+	}
+	if err := mock.ExpectationsWereMet(); err != nil {
+		t.Errorf("unmet mock expectations: %v", err)
+	}
+}
+
+func TestBroadcast_MalformedJSON(t *testing.T) {
+	mock := setupBroadcastDB(t)
+	c, w := buildBroadcastCtx(broadcastTestUUID, `not json`)
+
+	handler := NewBroadcastHandler(events.NewBroadcaster(ws.NewHub(nil)))
+	handler.Broadcast(c)
+
+	if w.Code != http.StatusBadRequest {
+		t.Errorf("want 400, got %d: %s", w.Code, w.Body.String())
+	}
+	if err := mock.ExpectationsWereMet(); err != nil {
+		t.Errorf("unmet mock expectations: %v", err)
+	}
+}
+
+// ─── Auth / Authz ─────────────────────────────────────────────────────────────
+
+func TestBroadcast_WorkspaceNotFound(t *testing.T) {
+	mock := setupBroadcastDB(t)
+	c, w := buildBroadcastCtx(broadcastTestUUID, `{"message":"hello"}`)
+
+	// Workspace lookup returns no rows.
+	mock.ExpectQuery("SELECT name, broadcast_enabled FROM workspaces WHERE id = $1 AND status != 'removed'").
+		WithArgs(broadcastTestUUID).
+		WillReturnError(sql.ErrNoRows)
+
+	handler := NewBroadcastHandler(events.NewBroadcaster(ws.NewHub(nil)))
+	handler.Broadcast(c)
+
+	if w.Code != http.StatusNotFound {
+		t.Errorf("want 404, got %d: %s", w.Code, w.Body.String())
+	}
+	if err := mock.ExpectationsWereMet(); err != nil {
+		t.Errorf("unmet mock expectations: %v", err)
+	}
+}
+
+func TestBroadcast_WorkspaceLookupQueryError(t *testing.T) {
+	mock := setupBroadcastDB(t)
+	c, w := buildBroadcastCtx(broadcastTestUUID, `{"message":"hello"}`)
+
+	mock.ExpectQuery("SELECT name, broadcast_enabled FROM workspaces WHERE id = $1 AND status != 'removed'").
+		WithArgs(broadcastTestUUID).
+		WillReturnError(sql.ErrConnDone)
+
+	handler := NewBroadcastHandler(events.NewBroadcaster(ws.NewHub(nil)))
+	handler.Broadcast(c)
+
+	if w.Code != http.StatusNotFound {
+		t.Errorf("want 404, got %d: %s", w.Code, w.Body.String())
+	}
+	if err := mock.ExpectationsWereMet(); err != nil {
+		t.Errorf("unmet mock expectations: %v", err)
+	}
+}
+
+func TestBroadcast_BroadcastDisabled(t *testing.T) {
+	mock := setupBroadcastDB(t)
+	c, w := buildBroadcastCtx(broadcastTestUUID, `{"message":"hello"}`)
+
+	// Workspace found but broadcast_enabled=false.
+	rows := sqlmock.NewRows([]string{"name", "broadcast_enabled"}).
+		AddRow("test-workspace", false)
+	mock.ExpectQuery("SELECT name, broadcast_enabled FROM workspaces WHERE id = $1 AND status != 'removed'").
+		WithArgs(broadcastTestUUID).
+		WillReturnRows(rows)
+
+	handler := NewBroadcastHandler(events.NewBroadcaster(ws.NewHub(nil)))
+	handler.Broadcast(c)
+
+	if w.Code != http.StatusForbidden {
+		t.Errorf("want 403, got %d: %s", w.Code, w.Body.String())
+	}
+	if err := mock.ExpectationsWereMet(); err != nil {
+		t.Errorf("unmet mock expectations: %v", err)
+	}
+}
+
+// ─── DB error paths ────────────────────────────────────────────────────────────
+
+func TestBroadcast_RecipientQueryError(t *testing.T) {
+	mock := setupBroadcastDB(t)
+	c, w := buildBroadcastCtx(broadcastTestUUID, `{"message":"hello"}`)
+
+	// Workspace lookup succeeds with broadcast_enabled=true.
+	mock.ExpectQuery("SELECT name, broadcast_enabled FROM workspaces WHERE id = $1 AND status != 'removed'").
+		WithArgs(broadcastTestUUID).
+		WillReturnRows(sqlmock.NewRows([]string{"name", "broadcast_enabled"}).AddRow("test-workspace", true))
+
+	// Recipient query fails.
+	mock.ExpectQuery("SELECT id FROM workspaces WHERE status != 'removed' AND id != $1").
+		WithArgs(broadcastTestUUID).
+		WillReturnError(sql.ErrConnDone)
+
+	handler := NewBroadcastHandler(events.NewBroadcaster(ws.NewHub(nil)))
+	handler.Broadcast(c)
+
+	if w.Code != http.StatusInternalServerError {
+		t.Errorf("want 500, got %d: %s", w.Code, w.Body.String())
+	}
+	if err := mock.ExpectationsWereMet(); err != nil {
+		t.Errorf("unmet mock expectations: %v", err)
+	}
+}
+
+func TestBroadcast_RecipientRowsError(t *testing.T) {
+	mock := setupBroadcastDB(t)
+	c, w := buildBroadcastCtx(broadcastTestUUID, `{"message":"hello"}`)
+
+	mock.ExpectQuery("SELECT name, broadcast_enabled FROM workspaces WHERE id = $1 AND status != 'removed'").
+		WithArgs(broadcastTestUUID).
+		WillReturnRows(sqlmock.NewRows([]string{"name", "broadcast_enabled"}).AddRow("test-workspace", true))
+
+	// Recipient query succeeds but rows.Err() fails.
+	badRows := sqlmock.NewRows([]string{"id"}).AddRow("ws-2").RowError(0, sql.ErrConnDone)
+	mock.ExpectQuery("SELECT id FROM workspaces WHERE status != 'removed' AND id != $1").
+		WithArgs(broadcastTestUUID).
+		WillReturnRows(badRows)
+
+	handler := NewBroadcastHandler(events.NewBroadcaster(ws.NewHub(nil)))
+	handler.Broadcast(c)
+
+	if w.Code != http.StatusInternalServerError {
+		t.Errorf("want 500, got %d: %s", w.Code, w.Body.String())
+	}
+	if err := mock.ExpectationsWereMet(); err != nil {
+		t.Errorf("unmet mock expectations: %v", err)
+	}
+}
+
+// ─── Success paths ────────────────────────────────────────────────────────────
+
+func TestBroadcast_Success_OneRecipient(t *testing.T) {
+	mock := setupBroadcastDB(t)
+	c, w := buildBroadcastCtx(broadcastTestUUID, `{"message":"hello world"}`)
+
+	// Workspace lookup.
+	mock.ExpectQuery("SELECT name, broadcast_enabled FROM workspaces WHERE id = $1 AND status != 'removed'").
+		WithArgs(broadcastTestUUID).
+		WillReturnRows(sqlmock.NewRows([]string{"name", "broadcast_enabled"}).AddRow("sender-workspace", true))
+
+	// Recipient query: one recipient.
+	recipRows := sqlmock.NewRows([]string{"id"}).AddRow("ws-recipient-1")
+	mock.ExpectQuery("SELECT id FROM workspaces WHERE status != 'removed' AND id != $1").
+		WithArgs(broadcastTestUUID).
+		WillReturnRows(recipRows)
+
+	// Activity log insert for recipient.
+	mock.ExpectExec("INSERT INTO activity_logs (workspace_id, activity_type, method, source_id, summary, status) VALUES ($1, 'broadcast_receive', 'broadcast', $2, $3, 'ok')").
+		WithArgs("ws-recipient-1", broadcastTestUUID, sqlmock.AnyArg()).
+		WillReturnResult(sqlmock.NewResult(0, 1))
+
+	// Activity log insert for sender (broadcast_sent).
+	mock.ExpectExec("INSERT INTO activity_logs (workspace_id, activity_type, method, summary, status) VALUES ($1, 'broadcast_sent', 'broadcast', $2, 'ok')").
+		WithArgs(broadcastTestUUID, sqlmock.AnyArg()).
+		WillReturnResult(sqlmock.NewResult(0, 1))
+
+	handler := NewBroadcastHandler(events.NewBroadcaster(ws.NewHub(nil)))
+	handler.Broadcast(c)
+
+	if w.Code != http.StatusOK {
+		t.Errorf("want 200, got %d: %s", w.Code, w.Body.String())
+	}
+	if err := mock.ExpectationsWereMet(); err != nil {
+		t.Errorf("unmet mock expectations: %v", err)
+	}
+}
+
+func TestBroadcast_Success_NoRecipients(t *testing.T) {
+	mock := setupBroadcastDB(t)
+	c, w := buildBroadcastCtx(broadcastTestUUID, `{"message":"hello"}`)
+
+	mock.ExpectQuery("SELECT name, broadcast_enabled FROM workspaces WHERE id = $1 AND status != 'removed'").
+		WithArgs(broadcastTestUUID).
+		WillReturnRows(sqlmock.NewRows([]string{"name", "broadcast_enabled"}).AddRow("solo-workspace", true))
+
+	// No recipients.
+	recipRows := sqlmock.NewRows([]string{"id"})
+	mock.ExpectQuery("SELECT id FROM workspaces WHERE status != 'removed' AND id != $1").
+		WithArgs(broadcastTestUUID).
+		WillReturnRows(recipRows)
+
+	// Activity log insert for sender (broadcast_sent).
+	mock.ExpectExec("INSERT INTO activity_logs (workspace_id, activity_type, method, summary, status) VALUES ($1, 'broadcast_sent', 'broadcast', $2, 'ok')").
+		WithArgs(broadcastTestUUID, sqlmock.AnyArg()).
+		WillReturnResult(sqlmock.NewResult(0, 1))
+
+	handler := NewBroadcastHandler(events.NewBroadcaster(ws.NewHub(nil)))
+	handler.Broadcast(c)
+
+	if w.Code != http.StatusOK {
+		t.Errorf("want 200, got %d: %s", w.Code, w.Body.String())
+	}
+	if err := mock.ExpectationsWereMet(); err != nil {
+		t.Errorf("unmet mock expectations: %v", err)
+	}
+}
+
+func TestBroadcast_Success_MultipleRecipients(t *testing.T) {
+	mock := setupBroadcastDB(t)
+	c, w := buildBroadcastCtx(broadcastTestUUID, `{"message":"hello"}`)
+
+	mock.ExpectQuery("SELECT name, broadcast_enabled FROM workspaces WHERE id = $1 AND status != 'removed'").
+		WithArgs(broadcastTestUUID).
+		WillReturnRows(sqlmock.NewRows([]string{"name", "broadcast_enabled"}).AddRow("broadcaster", true))
+
+	// Three recipients.
+	recipRows := sqlmock.NewRows([]string{"id"}).
+		AddRow("ws-1").AddRow("ws-2").AddRow("ws-3")
+	mock.ExpectQuery("SELECT id FROM workspaces WHERE status != 'removed' AND id != $1").
+		WithArgs(broadcastTestUUID).
+		WillReturnRows(recipRows)
+
+	// Each recipient gets a broadcast_receive log.
+	for _, rid := range []string{"ws-1", "ws-2", "ws-3"} {
+		mock.ExpectExec("INSERT INTO activity_logs (workspace_id, activity_type, method, source_id, summary, status) VALUES ($1, 'broadcast_receive', 'broadcast', $2, $3, 'ok')").
+			WithArgs(rid, broadcastTestUUID, sqlmock.AnyArg()).
+			WillReturnResult(sqlmock.NewResult(0, 1))
+	}
+
+	// Sender log.
+	mock.ExpectExec("INSERT INTO activity_logs (workspace_id, activity_type, method, summary, status) VALUES ($1, 'broadcast_sent', 'broadcast', $2, 'ok')").
+		WithArgs(broadcastTestUUID, sqlmock.AnyArg()).
+		WillReturnResult(sqlmock.NewResult(0, 1))
+
+	handler := NewBroadcastHandler(events.NewBroadcaster(ws.NewHub(nil)))
+	handler.Broadcast(c)
+
+	if w.Code != http.StatusOK {
+		t.Errorf("want 200, got %d: %s", w.Code, w.Body.String())
+	}
+	if err := mock.ExpectationsWereMet(); err != nil {
+		t.Errorf("unmet mock expectations: %v", err)
+	}
+}
+
+// ─── Recipient insert failure (logged, continues) ─────────────────────────────
+
+func TestBroadcast_RecipientInsertError_ContinuesAndSucceeds(t *testing.T) {
+	mock := setupBroadcastDB(t)
+	c, w := buildBroadcastCtx(broadcastTestUUID, `{"message":"hello"}`)
+
+	mock.ExpectQuery("SELECT name, broadcast_enabled FROM workspaces WHERE id = $1 AND status != 'removed'").
+		WithArgs(broadcastTestUUID).
+		WillReturnRows(sqlmock.NewRows([]string{"name", "broadcast_enabled"}).AddRow("broadcaster", true))
+
+	// Two recipients.
+	recipRows := sqlmock.NewRows([]string{"id"}).AddRow("ws-1").AddRow("ws-2")
+	mock.ExpectQuery("SELECT id FROM workspaces WHERE status != 'removed' AND id != $1").
+		WithArgs(broadcastTestUUID).
+		WillReturnRows(recipRows)
+
+	// First recipient insert fails (logged, continues).
+	mock.ExpectExec("INSERT INTO activity_logs (workspace_id, activity_type, method, source_id, summary, status) VALUES ($1, 'broadcast_receive', 'broadcast', $2, $3, 'ok')").
+		WithArgs("ws-1", broadcastTestUUID, sqlmock.AnyArg()).
+		WillReturnError(sql.ErrConnDone)
+
+	// Second recipient insert succeeds.
+	mock.ExpectExec("INSERT INTO activity_logs (workspace_id, activity_type, method, source_id, summary, status) VALUES ($1, 'broadcast_receive', 'broadcast', $2, $3, 'ok')").
+		WithArgs("ws-2", broadcastTestUUID, sqlmock.AnyArg()).
+		WillReturnResult(sqlmock.NewResult(0, 1))
+
+	// Sender log.
+	mock.ExpectExec("INSERT INTO activity_logs (workspace_id, activity_type, method, summary, status) VALUES ($1, 'broadcast_sent', 'broadcast', $2, 'ok')").
+		WithArgs(broadcastTestUUID, sqlmock.AnyArg()).
+		WillReturnResult(sqlmock.NewResult(0, 1))
+
+	handler := NewBroadcastHandler(events.NewBroadcaster(ws.NewHub(nil)))
+	handler.Broadcast(c)
+
+	// Handler returns 200 even though one insert failed — it logs and continues.
+	if w.Code != http.StatusOK {
+		t.Errorf("want 200 despite insert error, got %d: %s", w.Code, w.Body.String())
+	}
+	if err := mock.ExpectationsWereMet(); err != nil {
+		t.Errorf("unmet mock expectations: %v", err)
+	}
+}
+
+// ─── Sender activity log insert failure (logged, still 200) ────────────────────
+
+func TestBroadcast_SenderLogInsertError_Still200(t *testing.T) {
+	mock := setupBroadcastDB(t)
+	c, w := buildBroadcastCtx(broadcastTestUUID, `{"message":"hello"}`)
+
+	mock.ExpectQuery("SELECT name, broadcast_enabled FROM workspaces WHERE id = $1 AND status != 'removed'").
+		WithArgs(broadcastTestUUID).
+		WillReturnRows(sqlmock.NewRows([]string{"name", "broadcast_enabled"}).AddRow("broadcaster", true))
+
+	recipRows := sqlmock.NewRows([]string{"id"}).AddRow("ws-1")
+	mock.ExpectQuery("SELECT id FROM workspaces WHERE status != 'removed' AND id != $1").
+		WithArgs(broadcastTestUUID).
+		WillReturnRows(recipRows)
+
+	mock.ExpectExec("INSERT INTO activity_logs (workspace_id, activity_type, method, source_id, summary, status) VALUES ($1, 'broadcast_receive', 'broadcast', $2, $3, 'ok')").
+		WithArgs("ws-1", broadcastTestUUID, sqlmock.AnyArg()).
+		WillReturnResult(sqlmock.NewResult(0, 1))
+
+	// Sender log fails — but handler still returns 200 (logged only).
+	mock.ExpectExec("INSERT INTO activity_logs (workspace_id, activity_type, method, summary, status) VALUES ($1, 'broadcast_sent', 'broadcast', $2, 'ok')").
+		WithArgs(broadcastTestUUID, sqlmock.AnyArg()).
+		WillReturnError(sql.ErrConnDone)
+
+	handler := NewBroadcastHandler(events.NewBroadcaster(ws.NewHub(nil)))
+	handler.Broadcast(c)
+
+	if w.Code != http.StatusOK {
+		t.Errorf("want 200 despite sender log error, got %d: %s", w.Code, w.Body.String())
+	}
+	if err := mock.ExpectationsWereMet(); err != nil {
+		t.Errorf("unmet mock expectations: %v", err)
+	}
+}