[Bug] Fetching workflow update outcome yields incorrect JSON output in result and error cases

[dandavison]

Describe the bug

Fetching workflow update result via temporal workflow update execute or temporal workflow update result with -o json yields output that is incorrect in two ways:

• If there is the update failed with an error, no error JSON is produced.
• If the update succeeds, the JSON does not include full result payload details when using the --no-json-shorthand-payloads option (it is effectively silently ignored).

Minimal Reproduction

Failed update

Start this workflow

@workflow.defn
class WorkflowWithUpdate:
    @workflow.run
    async def run(self) -> None:
        await asyncio.Future()

    @workflow.update
    async def update(self) -> str:
        raise ApplicationError("error in update")

temporal workflow start --type WorkflowWithUpdate --task-queue demo

Now try to fetch an update result. The CLI outputs an error message but no JSON error info. It should output detailed structured error chain info including stack traces:

$ temporal workflow -o json update execute --workflow-id 195d41da-784e-406e-a376-53f18a99b1f4 --name update
Error: unable to update workflow: error in update

Successful update

Start this workflow

@workflow.defn
class WorkflowWithResult:
    @workflow.run
    async def run(self) -> str:
        return "workflow-result"

Then fetch the update result. The CLI outputs a JSON document describing the result, but --no-json-shorthand-payloads does not yield full payload details:

$ temporal workflow -o json update execute --workflow-id e97a2ee6-e2c8-49b4-849b-603a084e9cfb --name update
{
  "name": "update",
  "updateId": "71d71116-338a-4688-b502-a3fa678819e0",
  "result": "update-result"
}
$ temporal --no-json-shorthand-payloads workflow -o json update execute --workflow-id e97a2ee6-e2c8-49b4-849b-603a084e9cfb --name update
{
  "name": "update",
  "updateId": "e8a22eb1-4422-426c-a1e5-025504d6ff97",
  "result": "update-result"
}

This is inconsistent with the behavior for a standalone activity (or workflow, etc) result:

standalone activity

$ temporal activity execute -o json -a activity-1 --start-to-close-timeout 1s --type greet --task-queue demo --input '"World"'
{
  "activityId": "activity-1",
  "runId": "019c95ab-fcaa-7ce1-bbf3-f847a8ee4080",
  "status": "COMPLETED",
  "result": "Hello, World!"
}
$ temporal activity execute --no-json-shorthand-payloads -o json -a activity-1 --start-to-close-timeout 1s --type greet --task-queue demo --input '"World"'
{
  "activityId": "activity-1",
  "runId": "019c95ac-2bd9-79fd-be40-65e42be13717",
  "status": "COMPLETED",
  "result": {
    "payloads": [
      {
        "metadata": {
          "encoding": "anNvbi9wbGFpbg=="
        },
        "data": "IkhlbGxvLCBXb3JsZCEi"
      }
    ]
  }
}

workflow

$ temporal workflow result -o json --workflow-id 2ba765c4-3e1b-4854-b31d-ddcfd37b2598
{
  "workflowId": "2ba765c4-3e1b-4854-b31d-ddcfd37b2598",
  "runId": "019c959e-0ca9-77c7-8e66-d843ced91424",
  "namespace": "dan-sa-demo.a2dd6",
  "status": "COMPLETED",
  "closeEvent": {
    "eventId": "5",
    "eventTime": "2026-02-25T16:24:49.131790142Z",
    "eventType": "EVENT_TYPE_WORKFLOW_EXECUTION_COMPLETED",
    "version": "100265",
    "taskId": "266083684",
    "workflowExecutionCompletedEventAttributes": {
      "result": [
        "workflow-result"
      ],
      "workflowTaskCompletedEventId": "4"
    }
  },
  "result": "workflow-result"
}
$ temporal workflow result --no-json-shorthand-payloads -o json --workflow-id 2ba765c4-3e1b-4854-b31d-ddcfd37b2598
{
  "workflowId": "2ba765c4-3e1b-4854-b31d-ddcfd37b2598",
  "runId": "019c959e-0ca9-77c7-8e66-d843ced91424",
  "namespace": "dan-sa-demo.a2dd6",
  "status": "COMPLETED",
  "closeEvent": {
    "eventId": "5",
    "eventTime": "2026-02-25T16:24:49.131790142Z",
    "eventType": "EVENT_TYPE_WORKFLOW_EXECUTION_COMPLETED",
    "version": "100265",
    "taskId": "266083684",
    "workflowExecutionCompletedEventAttributes": {
      "result": {
        "payloads": [
          {
            "metadata": {
              "encoding": "anNvbi9wbGFpbg=="
            },
            "data": "IndvcmtmbG93LXJlc3VsdCI="
          }
        ]
      },
      "workflowTaskCompletedEventId": "4"
    }
  },
  "result": {
    "metadata": {
      "encoding": "anNvbi9wbGFpbg=="
    },
    "data": "IndvcmtmbG93LXJlc3VsdCI="
  }
}