diff --git a/go.mod b/go.mod
index 31dbc86..1cc5f01 100644
--- a/go.mod
+++ b/go.mod
@@ -13,7 +13,7 @@ require (
 	github.com/modelcontextprotocol/go-sdk v1.6.1
 	github.com/teamwork/desksdkgo v1.0.1
 	github.com/teamwork/spacessdkgo v0.0.0-20260518181558-a6af69d00abb
-	github.com/teamwork/twapi-go-sdk v1.20.3
+	github.com/teamwork/twapi-go-sdk v1.20.4
 )
 
 require (
diff --git a/go.sum b/go.sum
index 75f14ae..b39afeb 100644
--- a/go.sum
+++ b/go.sum
@@ -184,8 +184,8 @@ github.com/teamwork/desksdkgo v1.0.1 h1:Mi5D1pnGfL5JwD7s7g7OyHml7Y9jsak5MNJaotJt
 github.com/teamwork/desksdkgo v1.0.1/go.mod h1:Mgvw83q8iqHr7Sm9xV1iI/T89o3ObaPU3ChMJheRzwA=
 github.com/teamwork/spacessdkgo v0.0.0-20260518181558-a6af69d00abb h1:bQluDjySZeC5etnWgjk4WFRy0PvzGDw8XEBd4JJYWCQ=
 github.com/teamwork/spacessdkgo v0.0.0-20260518181558-a6af69d00abb/go.mod h1:jfE0RLsZuk/3Glzs5bJ95pNb92emV7uXZYgoGSLQ76I=
-github.com/teamwork/twapi-go-sdk v1.20.3 h1:W4V2adgnrdCqdAupUgm1ElurmFpaND8fOUI/SuH2gBU=
-github.com/teamwork/twapi-go-sdk v1.20.3/go.mod h1:uj6BNtyyKtggfeY3whzn8bLWuhP1twhghjWD6z3h3F4=
+github.com/teamwork/twapi-go-sdk v1.20.4 h1:W5ycV6GDDc/SlNkMopIrX1/QeReV6PeqFUBuLqsDuDk=
+github.com/teamwork/twapi-go-sdk v1.20.4/go.mod h1:uj6BNtyyKtggfeY3whzn8bLWuhP1twhghjWD6z3h3F4=
 github.com/tinylib/msgp v1.6.3 h1:bCSxiTz386UTgyT1i0MSCvdbWjVW+8sG3PjkGsZQt4s=
 github.com/tinylib/msgp v1.6.3/go.mod h1:RSp0LW9oSxFut3KzESt5Voq4GVWyS+PSulT77roAqEA=
 github.com/tklauser/go-sysconf v0.3.16 h1:frioLaCQSsF5Cy1jgRBrzr6t502KIIwQ0MArYICU0nA=
diff --git a/internal/twprojects/tasks.go b/internal/twprojects/tasks.go
index 60ae922..dc04661 100644
--- a/internal/twprojects/tasks.go
+++ b/internal/twprojects/tasks.go
@@ -755,6 +755,15 @@ func TaskList(engine *twapi.Engine) toolsets.ToolWrapper {
 							{Type: "null"},
 						},
 					},
+					"show_completed": {
+						Description: "If true, include completed tasks and tasks belonging to completed tasklists; " +
+							"both excluded by default.",
+						AnyOf: []*jsonschema.Schema{
+							{Type: "boolean"},
+							{Type: "null"},
+						},
+						Default: []byte(`false`),
+					},
 					"only_unassigned": {
 						Description: "If true, only return tasks that have no assignee.",
 						AnyOf: []*jsonschema.Schema{
@@ -786,6 +795,7 @@ func TaskList(engine *twapi.Engine) toolsets.ToolWrapper {
 				return helpers.NewToolResultTextError("failed to decode request: %s", err.Error()), nil
 			}
 			verbose := true
+			var showCompleted *bool
 			err := helpers.ParamGroup(arguments,
 				helpers.OptionalNumericParam(&taskListRequest.Path.TasklistID, "tasklist_id"),
 				helpers.OptionalNumericParam(&taskListRequest.Path.ProjectID, "project_id"),
@@ -804,6 +814,7 @@ func TaskList(engine *twapi.Engine) toolsets.ToolWrapper {
 				helpers.OptionalTimePointerParam(&taskListRequest.Filters.CompletedBefore, "completed_before"),
 				helpers.OptionalDatePointerParam(&taskListRequest.Filters.DueAfter, "due_after"),
 				helpers.OptionalDatePointerParam(&taskListRequest.Filters.DueBefore, "due_before"),
+				helpers.OptionalPointerParam(&showCompleted, "show_completed"),
 				helpers.OptionalPointerParam(&taskListRequest.Filters.OnlyUnassigned, "only_unassigned"),
 				helpers.OptionalPointerParam(&taskListRequest.Filters.OnlyUnplanned, "only_unplanned"),
 				helpers.OptionalParam(&verbose, "verbose"),
@@ -811,6 +822,13 @@ func TaskList(engine *twapi.Engine) toolsets.ToolWrapper {
 			if err != nil {
 				return helpers.NewToolResultTextError("invalid parameters: %s", err.Error()), nil
 			}
+			if showCompleted != nil {
+				// A single flag drives both SDK filters: completed tasks are hidden by
+				// default, and so are tasks living inside a completed tasklist. Callers
+				// asking to see completed work expect both.
+				taskListRequest.Filters.IncludeCompletedTasks = showCompleted
+				taskListRequest.Filters.IncludeTasksFromCompletedTasklists = showCompleted
+			}
 			if verbose {
 				// Include custom fields and values in task list response for richer
 				// context, as they are commonly used in Teamwork projects and provide
diff --git a/internal/twprojects/tasks_test.go b/internal/twprojects/tasks_test.go
index a35f857..ad80aad 100644
--- a/internal/twprojects/tasks_test.go
+++ b/internal/twprojects/tasks_test.go
@@ -189,6 +189,7 @@ func TestTaskList(t *testing.T) {
 		"completed_before":    "2023-10-31T23:59:59Z",
 		"due_after":           "2023-10-01",
 		"due_before":          "2023-10-31",
+		"show_completed":      true,
 		"only_unassigned":     true,
 		"only_unplanned":      true,
 		"page":                float64(1),
@@ -213,6 +214,7 @@ func TestTaskListByTasklist(t *testing.T) {
 		"completed_before":    "2023-10-31T23:59:59Z",
 		"due_after":           "2023-10-01",
 		"due_before":          "2023-10-31",
+		"show_completed":      true,
 		"only_unassigned":     true,
 		"only_unplanned":      true,
 		"page":                float64(1),
@@ -237,6 +239,7 @@ func TestTaskListByProject(t *testing.T) {
 		"completed_before":    "2023-10-31T23:59:59Z",
 		"due_after":           "2023-10-01",
 		"due_before":          "2023-10-31",
+		"show_completed":      true,
 		"only_unassigned":     true,
 		"only_unplanned":      true,
 		"page":                float64(1),