Stop echoing back step fields the caller never changed

internal/commands/assign.go

@@ -644,10 +644,7 @@ func doAssignStep(cmd *cobra.Command, app *appctx.App, stepIDStr, assigneeID str
 	}
 	assigneeIDs = append(assigneeIDs, assigneeIDInt)
 
-	// The API rejects step updates without a title, so carry over the
-	// current one.
 	updated, err := app.Account().CardSteps().Update(cmd.Context(), stepID, &basecamp.UpdateStepRequest{
- Title: step.Title,
  AssigneeIDs: assigneeIDs,
 	})
 	if err != nil {
@@ -749,10 +746,7 @@ func doUnassignStep(cmd *cobra.Command, app *appctx.App, stepIDStr string, assig
 
 	assigneeIDs := removeID(existingAssigneeIDs(step.Assignees), assigneeIDInt)
 
-	// The API rejects step updates without a title, so carry over the
-	// current one.
 	updated, err := app.Account().CardSteps().Update(cmd.Context(), stepID, &basecamp.UpdateStepRequest{
- Title: step.Title,
  AssigneeIDs: assigneeIDs,
 	})
 	if err != nil {

internal/commands/assign_test.go

@@ -726,7 +726,7 @@ func (m *mockStepAssignTransport) RoundTrip(req *http.Request) (*http.Response,
 	header := make(http.Header)
 	header.Set("Content-Type", "application/json")
 
-	stepJSON := `{"id": 456, "title": "Existing step", "completed": false, "assignees": [{"id": 11, "name": "Existing Person"}]}`
+	stepJSON := `{"id": 456, "title": "Existing step", "due_on": "2026-09-01", "completed": false, "assignees": [{"id": 11, "name": "Existing Person"}]}`
 
 	switch req.Method {
 	case "GET":
@@ -762,9 +762,12 @@ func (m *mockStepAssignTransport) RoundTrip(req *http.Request) (*http.Response,
 	}
 }
 
-// TestAssignStepCarriesTitle verifies that assigning a person to a step sends
-// the current title in the update, which the API requires.
-func TestAssignStepCarriesTitle(t *testing.T) {
+// TestAssignStepSendsOnlyAssignees verifies that assigning a person to a step
+// sends assignee_ids and nothing else. The server preserves attributes the
+// request omits, so echoing back the title or due date would be the CLI
+// re-asserting values the caller never changed — and reverting a concurrent
+// edit to them.
+func TestAssignStepSendsOnlyAssignees(t *testing.T) {
 	transport := &mockStepAssignTransport{}
 	app := setupCardsMockApp(t, transport)
 
@@ -774,13 +777,16 @@ func TestAssignStepCarriesTitle(t *testing.T) {
 
 	var body map[string]any
 	require.NoError(t, json.Unmarshal(transport.capturedPut, &body))
-	assert.Equal(t, "Existing step", body["title"])
+	assert.NotContains(t, body, "title")
+	assert.NotContains(t, body, "due_on")
 	assert.Equal(t, []any{float64(11), float64(99)}, body["assignee_ids"])
 }
 
-// TestUnassignStepCarriesTitle verifies that removing a person from a step
-// also sends the current title in the update.
-func TestUnassignStepCarriesTitle(t *testing.T) {
+// TestUnassignStepSendsEmptyAssigneeList verifies the same for removal, and
+// that taking off the last assignee sends an explicit empty list — omitting
+// the key would now mean "leave assignees alone", so the clear must be said
+// out loud.
+func TestUnassignStepSendsEmptyAssigneeList(t *testing.T) {
 	transport := &mockStepAssignTransport{}
 	app := setupCardsMockApp(t, transport)
 
@@ -790,6 +796,7 @@ func TestUnassignStepCarriesTitle(t *testing.T) {
 
 	var body map[string]any
 	require.NoError(t, json.Unmarshal(transport.capturedPut, &body))
-	assert.Equal(t, "Existing step", body["title"])
+	assert.NotContains(t, body, "title")
+	assert.NotContains(t, body, "due_on")
 	assert.Equal(t, []any{}, body["assignee_ids"])
 }

internal/commands/cards.go

@@ -2938,14 +2938,6 @@ You can pass either a step ID or a Basecamp URL:
  req := &basecamp.UpdateStepRequest{}
  if title != "" {
  req.Title = title
- } else {
- // The API rejects step updates without a title, so carry
- // over the current one when only other fields change.
- current, err := app.Account().CardSteps().Get(cmd.Context(), stepID)
- if err != nil {
- return convertSDKError(err)
- }
- req.Title = current.Title
  }
  if dueOn != "" {
  req.DueOn = dateparse.Parse(dueOn)

internal/commands/cards_test.go

@@ -241,40 +241,41 @@ func (t *mockStepUpdateTransport) RoundTrip(req *http.Request) (*http.Response,
 	}, nil
 }
 
-// TestCardsStepUpdateAssigneesOnlyCarriesTitle verifies that updating only
-// assignees fetches the current step and includes its title in the request —
-// the API rejects step updates without a title.
-func TestCardsStepUpdateAssigneesOnlyCarriesTitle(t *testing.T) {
+// TestCardsStepUpdateAssigneesOnlySendsNoTitle verifies that updating only
+// assignees sends assignees and nothing else. The server preserves attributes
+// the request omits, so there is no title to carry over — and getCount is what
+// proves the extra read is gone, since the body alone cannot.
+func TestCardsStepUpdateAssigneesOnlySendsNoTitle(t *testing.T) {
 	transport := &mockStepUpdateTransport{}
 	app := setupCardsMockApp(t, transport)
 
 	cmd := newCardsStepUpdateCmd()
 	err := executeCommand(cmd, app, "456", "--assignees", "789")
 	require.NoError(t, err)
 
-	assert.Equal(t, 1, transport.getCount)
+	assert.Equal(t, 0, transport.getCount, "expected no read-before-write")
 
 	var body map[string]any
 	require.NoError(t, json.Unmarshal(transport.capturedPut, &body))
-	assert.Equal(t, "Current title", body["title"])
+	assert.NotContains(t, body, "title", "must not echo back a field the caller never changed")
 	assert.Equal(t, []any{float64(789)}, body["assignee_ids"])
 }
 
-// TestCardsStepUpdateDueOnlyCarriesTitle verifies that updating only the due
-// date fetches the current step and includes its title in the request.
-func TestCardsStepUpdateDueOnlyCarriesTitle(t *testing.T) {
+// TestCardsStepUpdateDueOnlySendsNoTitle verifies the same for a due-date-only
+// update.
+func TestCardsStepUpdateDueOnlySendsNoTitle(t *testing.T) {
 	transport := &mockStepUpdateTransport{}
 	app := setupCardsMockApp(t, transport)
 
 	cmd := newCardsStepUpdateCmd()
 	err := executeCommand(cmd, app, "456", "--due", "2026-07-04")
 	require.NoError(t, err)
 
-	assert.Equal(t, 1, transport.getCount)
+	assert.Equal(t, 0, transport.getCount, "expected no read-before-write")
 
 	var body map[string]any
 	require.NoError(t, json.Unmarshal(transport.capturedPut, &body))
-	assert.Equal(t, "Current title", body["title"])
+	assert.NotContains(t, body, "title", "must not echo back a field the caller never changed")
 	assert.Equal(t, "2026-07-04", body["due_on"])
 }
 

skills/basecamp/SKILL.md

@@ -547,10 +547,10 @@ PARENT_TODO_ID=<parent_todo_id> \
 basecamp recordings list --in <project> --type Kanban::Step --all \
  --jq '.data[] | select(.parent.id==(env.PARENT_TODO_ID | tonumber)) | {id,title,status,parent:.parent.id,url}'
 
-# Assign or set a due date.
-# Include the current title and every person who should remain assigned.
+# Assign or set a due date. Send only what you're changing — omitted fields are
+# left alone. `assignee_ids` replaces the whole list, so name everyone who stays.
 basecamp api put /buckets/<project_id>/card_tables/steps/<step_id>.json \
- --data '{"title":"Current subtask title","assignee_ids":[<person_id>,<existing_person_id>],"due_on":"<YYYY-MM-DD>"}' \
+ --data '{"assignee_ids":[<person_id>,<existing_person_id>],"due_on":"<YYYY-MM-DD>"}' \
  --json
 
 # Complete or reopen a subtask
@@ -589,10 +589,20 @@ returned `not_found`:
 subtasks, add `--status trashed`; archived parents may require
 `--status archived`.
 
-When updating a todo subtask with the raw API, include the existing `title` along
-with metadata changes; omitting it may reset the step title to `Untitled`.
-`assignee_ids` sets the full assignee list for the step, so include every person
-who should remain assigned. The generic
+**Raw step updates are partial.** `PUT .../card_tables/steps/<id>.json` leaves
+every parameter you omit unchanged, so send only the fields you are changing.
+Echoing back a `title` you did not mean to change is not merely redundant — it
+reverts anyone who edited the title between your read and your write. To clear a
+value, say so explicitly: `"due_on": null` clears the due date, `"assignee_ids":
+[]` removes everyone. `assignee_ids` always replaces the whole list rather than
+adding to it, so name every person who should remain assigned.
+
+(This is bc3#12521. Before it, an omitted field *was* cleared and a title-less
+update was rejected, which is why older guidance said to resend the title. Todo
+subtasks and card steps share one endpoint and one contract — `PUT
+card_tables/steps/:id` routes to the same controller for both.)
+
+The generic
 `basecamp assign <step_id> --step ...` command is intended for card steps and
 may fail with `Bad Request` for todo-backed steps, so prefer `assignee_ids` on
 the raw step update endpoint for todo subtasks.