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..9a5ae9e6e
--- /dev/null
+++ b/workspace-server/internal/handlers/workspace_broadcast_test.go
@@ -0,0 +1,277 @@
+package handlers
+
+// workspace_broadcast_test.go — coverage for workspace_broadcast.go.
+//
+// Covered handlers:
+//   - BroadcastHandler.Broadcast  POST /workspaces/:id/broadcast
+//   - broadcastTruncate            pure function
+//
+// DB reads are mocked via sqlmock. The *events.Broadcaster is injected
+// as the real no-op test broadcaster so BroadcastOnly() is safe in tests.
+
+import (
+	"context"
+	"encoding/json"
+	"net/http"
+	"net/http/httptest"
+	"strings"
+	"testing"
+
+	"github.com/DATA-DOG/go-sqlmock"
+	"github.com/Molecule-AI/molecule-monorepo/platform/internal/db"
+	"github.com/gin-gonic/gin"
+	"github.com/stretchr/testify/require"
+)
+
+// ─── broadcastTruncate ─────────────────────────────────────────────────────────
+
+func TestBroadcastTruncate_LenBelowMax_ReturnsFullString(t *testing.T) {
+	result := broadcastTruncate("hello", 10)
+	require.Equal(t, "hello", result)
+}
+
+func TestBroadcastTruncate_LenEqualMax_ReturnsFullString(t *testing.T) {
+	result := broadcastTruncate("hello", 5)
+	require.Equal(t, "hello", result)
+}
+
+func TestBroadcastTruncate_LenAboveMax_TruncatesWithEllipsis(t *testing.T) {
+	result := broadcastTruncate("hello world", 5)
+	require.Equal(t, "hello…", result)
+}
+
+func TestBroadcastTruncate_EmptyString_ReturnsEmpty(t *testing.T) {
+	result := broadcastTruncate("", 5)
+	require.Equal(t, "", result)
+}
+
+func TestBroadcastTruncate_Unicode_TruncatesAtRuneBoundary(t *testing.T) {
+	// "日本語" is 3 runes; truncating at max=2 should give 2 runes + ellipsis.
+	result := broadcastTruncate("日本語abcdef", 2)
+	require.Equal(t, "日本…", result)
+}
+
+// ─── Broadcast handler ────────────────────────────────────────────────────────
+
+// Valid UUIDs used throughout the test suite.
+const (
+	testSenderID      = "00000000-0000-0000-0000-000000000001"
+	testRecipient1   = "00000000-0000-0000-0000-000000000002"
+	testRecipient2    = "00000000-0000-0000-0000-000000000003"
+)
+
+func setupBroadcastCtx(t *testing.T, body string) (*BroadcastHandler, sqlmock.Sqlmock, *httptest.ResponseRecorder, *gin.Context) {
+	t.Helper()
+	mockDB, mock, err := sqlmock.New()
+	require.NoError(t, err)
+	prevDB := db.DB
+	db.DB = mockDB
+	t.Cleanup(func() { db.DB = prevDB; mockDB.Close() })
+
+	gin.SetMode(gin.TestMode)
+	w := httptest.NewRecorder()
+	c, _ := gin.CreateTestContext(w)
+	c.Params = gin.Params{{Key: "id", Value: testSenderID}}
+	c.Request = httptest.NewRequest("POST", "/workspaces/"+testSenderID+"/broadcast", strings.NewReader(body))
+	c.Request.Header.Set("Content-Type", "application/json")
+
+	h := NewBroadcastHandler(newTestBroadcaster())
+	return h, mock, w, c
+}
+
+func TestBroadcast_InvalidWorkspaceID_Returns400(t *testing.T) {
+	gin.SetMode(gin.TestMode)
+	w := httptest.NewRecorder()
+	c, _ := gin.CreateTestContext(w)
+	c.Request = httptest.NewRequest("POST", "/workspaces/not-a-uuid/broadcast", nil)
+	c.Params = gin.Params{{Key: "id", Value: "not-a-uuid"}}
+
+	h := NewBroadcastHandler(newTestBroadcaster())
+	h.Broadcast(c)
+
+	require.Equal(t, http.StatusBadRequest, w.Code)
+	var body map[string]string
+	json.Unmarshal(w.Body.Bytes(), &body)
+	require.Contains(t, body["error"], "invalid workspace ID")
+}
+
+func TestBroadcast_MissingMessage_Returns400(t *testing.T) {
+	h, _, w, c := setupBroadcastCtx(t, `{}`)
+
+	// ShouldBindJSON fails first — no DB query expected.
+	h.Broadcast(c)
+
+	require.Equal(t, http.StatusBadRequest, w.Code)
+	var body map[string]string
+	json.Unmarshal(w.Body.Bytes(), &body)
+	require.Equal(t, "message is required", body["error"])
+}
+
+func TestBroadcast_WorkspaceNotFound_Returns404(t *testing.T) {
+	h, mock, w, c := setupBroadcastCtx(t, `{"message":"hello"}`)
+
+	mock.ExpectQuery(`SELECT name, broadcast_enabled FROM workspaces WHERE id = \$1 AND status != 'removed'`).
+		WithArgs(testSenderID).
+		WillReturnRows(sqlmock.NewRows([]string{"name", "broadcast_enabled"})) // empty
+
+	h.Broadcast(c)
+
+	require.Equal(t, http.StatusNotFound, w.Code)
+	var body map[string]string
+	json.Unmarshal(w.Body.Bytes(), &body)
+	require.Equal(t, "workspace not found", body["error"])
+}
+
+func TestBroadcast_BroadcastDisabled_Returns403(t *testing.T) {
+	h, mock, w, c := setupBroadcastCtx(t, `{"message":"hello"}`)
+
+	mock.ExpectQuery(`SELECT name, broadcast_enabled FROM workspaces WHERE id = \$1 AND status != 'removed'`).
+		WithArgs(testSenderID).
+		WillReturnRows(sqlmock.NewRows([]string{"name", "broadcast_enabled"}).
+			AddRow("test-ws", false))
+
+	h.Broadcast(c)
+
+	require.Equal(t, http.StatusForbidden, w.Code)
+	var body map[string]string
+	json.Unmarshal(w.Body.Bytes(), &body)
+	require.Equal(t, "broadcast_disabled", body["error"])
+}
+
+func TestBroadcast_RecipientQueryError_Returns500(t *testing.T) {
+	h, mock, w, c := setupBroadcastCtx(t, `{"message":"hello"}`)
+
+	mock.ExpectQuery(`SELECT name, broadcast_enabled FROM workspaces WHERE id = \$1 AND status != 'removed'`).
+		WithArgs(testSenderID).
+		WillReturnRows(sqlmock.NewRows([]string{"name", "broadcast_enabled"}).
+			AddRow("test-ws", true))
+	mock.ExpectQuery(`SELECT id FROM workspaces WHERE status != 'removed' AND id != \$1`).
+		WithArgs(testSenderID).
+		WillReturnError(context.DeadlineExceeded)
+
+	h.Broadcast(c)
+
+	require.Equal(t, http.StatusInternalServerError, w.Code)
+}
+
+func TestBroadcast_Success_Returns200AndDeliveredCount(t *testing.T) {
+	h, mock, w, c := setupBroadcastCtx(t, `{"message":"hello world"}`)
+
+	mock.ExpectQuery(`SELECT name, broadcast_enabled FROM workspaces WHERE id = \$1 AND status != 'removed'`).
+		WithArgs(testSenderID).
+		WillReturnRows(sqlmock.NewRows([]string{"name", "broadcast_enabled"}).
+			AddRow("test-ws", true))
+	// Two recipients.
+	mock.ExpectQuery(`SELECT id FROM workspaces WHERE status != 'removed' AND id != \$1`).
+		WithArgs(testSenderID).
+		WillReturnRows(sqlmock.NewRows([]string{"id"}).AddRow(testRecipient1).AddRow(testRecipient2))
+	// Activity log insert per recipient.
+	mock.ExpectExec(`INSERT INTO activity_logs`).
+		WithArgs(testRecipient1, testSenderID, "Broadcast from test-ws: hello world").
+		WillReturnResult(sqlmock.NewResult(1, 1))
+	mock.ExpectExec(`INSERT INTO activity_logs`).
+		WithArgs(testRecipient2, testSenderID, "Broadcast from test-ws: hello world").
+		WillReturnResult(sqlmock.NewResult(1, 1))
+	// Sender's own log.
+	mock.ExpectExec(`INSERT INTO activity_logs`).
+		WithArgs(testSenderID, "Broadcast sent to 2 workspace(s)").
+		WillReturnResult(sqlmock.NewResult(1, 1))
+
+	h.Broadcast(c)
+
+	require.Equal(t, http.StatusOK, w.Code)
+	var body map[string]interface{}
+	json.Unmarshal(w.Body.Bytes(), &body)
+	require.Equal(t, "sent", body["status"])
+	require.Equal(t, float64(2), body["delivered"])
+}
+
+func TestBroadcast_NoRecipients_ReturnsZeroDelivered(t *testing.T) {
+	h, mock, w, c := setupBroadcastCtx(t, `{"message":"hello"}`)
+
+	mock.ExpectQuery(`SELECT name, broadcast_enabled FROM workspaces WHERE id = \$1 AND status != 'removed'`).
+		WithArgs(testSenderID).
+		WillReturnRows(sqlmock.NewRows([]string{"name", "broadcast_enabled"}).
+			AddRow("solo-ws", true))
+	// No other workspaces.
+	mock.ExpectQuery(`SELECT id FROM workspaces WHERE status != 'removed' AND id != \$1`).
+		WithArgs(testSenderID).
+		WillReturnRows(sqlmock.NewRows([]string{"id"}))
+	// Sender log still fires.
+	mock.ExpectExec(`INSERT INTO activity_logs`).
+		WithArgs(testSenderID, "Broadcast sent to 0 workspace(s)").
+		WillReturnResult(sqlmock.NewResult(1, 1))
+
+	h.Broadcast(c)
+
+	require.Equal(t, http.StatusOK, w.Code)
+	var body map[string]interface{}
+	json.Unmarshal(w.Body.Bytes(), &body)
+	require.Equal(t, "sent", body["status"])
+	require.Equal(t, float64(0), body["delivered"])
+}
+
+func TestBroadcast_ActivityLogInsertFails_StillReturns200(t *testing.T) {
+	// Sender's own activity log is best-effort; a DB error is logged but
+	// does NOT fail the HTTP response.
+	h, mock, w, c := setupBroadcastCtx(t, `{"message":"hello"}`)
+
+	mock.ExpectQuery(`SELECT name, broadcast_enabled FROM workspaces WHERE id = \$1 AND status != 'removed'`).
+		WithArgs(testSenderID).
+		WillReturnRows(sqlmock.NewRows([]string{"name", "broadcast_enabled"}).
+			AddRow("test-ws", true))
+	mock.ExpectQuery(`SELECT id FROM workspaces WHERE status != 'removed' AND id != \$1`).
+		WithArgs(testSenderID).
+		WillReturnRows(sqlmock.NewRows([]string{"id"}))
+	// Recipient insert succeeds.
+	mock.ExpectExec(`INSERT INTO activity_logs`).
+		WillReturnResult(sqlmock.NewResult(1, 1))
+	// Sender log FAILS — handler logs but still returns 200.
+	mock.ExpectExec(`INSERT INTO activity_logs`).
+		WillReturnError(context.DeadlineExceeded)
+
+	h.Broadcast(c)
+
+	require.Equal(t, http.StatusOK, w.Code) // NOT 500
+}
+
+func TestBroadcast_RecipientInsertFails_ContinuesAndCountsOthers(t *testing.T) {
+	// A recipient-level insert failure is logged; the handler continues
+	// delivering to remaining recipients and reports the delivered count.
+	h, mock, w, c := setupBroadcastCtx(t, `{"message":"hello"}`)
+
+	mock.ExpectQuery(`SELECT name, broadcast_enabled FROM workspaces WHERE id = \$1 AND status != 'removed'`).
+		WithArgs(testSenderID).
+		WillReturnRows(sqlmock.NewRows([]string{"name", "broadcast_enabled"}).
+			AddRow("test-ws", true))
+	// Two recipients.
+	mock.ExpectQuery(`SELECT id FROM workspaces WHERE status != 'removed' AND id != \$1`).
+		WithArgs(testSenderID).
+		WillReturnRows(sqlmock.NewRows([]string{"id"}).AddRow(testRecipient1).AddRow(testRecipient2))
+	// testRecipient1 insert FAILS — logged, handler continues.
+	mock.ExpectExec(`INSERT INTO activity_logs`).
+		WithArgs(testRecipient1, testSenderID, "Broadcast from test-ws: hello").
+		WillReturnError(context.DeadlineExceeded)
+	// testRecipient2 insert succeeds.
+	mock.ExpectExec(`INSERT INTO activity_logs`).
+		WithArgs(testRecipient2, testSenderID, "Broadcast from test-ws: hello").
+		WillReturnResult(sqlmock.NewResult(1, 1))
+	// Sender log.
+	mock.ExpectExec(`INSERT INTO activity_logs`).
+		WithArgs(testSenderID, "Broadcast sent to 1 workspace(s)").
+		WillReturnResult(sqlmock.NewResult(1, 1))
+
+	h.Broadcast(c)
+
+	require.Equal(t, http.StatusOK, w.Code)
+	var body map[string]interface{}
+	json.Unmarshal(w.Body.Bytes(), &body)
+	require.Equal(t, float64(1), body["delivered"]) // only testRecipient2 counted
+}
+
+func TestBroadcast_NewBroadcastHandler(t *testing.T) {
+	b := newTestBroadcaster()
+	h := NewBroadcastHandler(b)
+	require.NotNil(t, h)
+	require.Equal(t, b, h.broadcaster)
+}