flowable/flowable-engine · error · FlowableObjectNotFoundException

Could not find a task instance with id '" + taskId + "'.

Error message

Could not find a task instance with id '" + taskId + "'.

What it means

The history task lookup via historyService.createHistoricTaskInstanceQuery().taskId(taskId).singleResult() returned null, so Flowable throws FlowableObjectNotFoundException typed to HistoricTaskInstance. It means no historic task with that id exists in the history tables.

Source

Thrown at modules/flowable-rest/src/main/java/org/flowable/rest/service/api/history/HistoricTaskInstanceBaseResource.java:335

     */
    protected HistoricTaskInstance getHistoricTaskInstanceFromRequest(String taskId) {
        HistoricTaskInstance taskInstance = getHistoricTaskInstanceFromRequestWithoutAccessCheck(taskId);

        if (restApiInterceptor != null) {
            restApiInterceptor.accessHistoryTaskInfoById(taskInstance);
        }

        return taskInstance;
    }

    /**
     * Returns the {@link HistoricTaskInstance} that is requested without calling the access interceptor
     * Throws the right exceptions when bad request was made or instance was not found.
     */
    protected HistoricTaskInstance getHistoricTaskInstanceFromRequestWithoutAccessCheck(String taskId) {
        HistoricTaskInstance taskInstance = historyService.createHistoricTaskInstanceQuery().taskId(taskId).singleResult();
        if (taskInstance == null) {
            throw new FlowableObjectNotFoundException("Could not find a task instance with id '" + taskId + "'.", HistoricTaskInstance.class);
        }
        
        return taskInstance;
    }

    protected void addTaskVariables(HistoricTaskInstanceQuery taskInstanceQuery, List<QueryVariable> variables) {
        for (QueryVariable variable : variables) {
            if (variable.getVariableOperation() == null) {
                throw new FlowableIllegalArgumentException("Variable operation is missing for variable: " + variable.getName());
            }
            if (variable.getVariableOperation() != QueryVariableOperation.EXISTS && variable.getVariableOperation() != QueryVariableOperation.NOT_EXISTS) {
                if (variable.getValue() == null) {
                    throw new FlowableIllegalArgumentException("Variable value is missing for variable: " + variable.getName());
                }
            }

            boolean nameLess = variable.getName() == null;

View on GitHub (pinned to d6d39ce1c6)

Solutions

1. Confirm the task id via runtime TaskService query if the task is still active
2. Query ACT_HI_TASKINST (or the history task query) to verify the id exists in history
3. If the task must be historic, ensure history level records tasks ('audit' or higher)
4. Check tenant/datasource configuration to ensure you query the engine that owns the task

Example fix

// before
HistoricTaskInstance t = historyService.createHistoricTaskInstanceQuery().taskId(taskId).singleResult();
historicTaskApi.get(taskId); // throws
// after
HistoricTaskInstance t = historyService.createHistoricTaskInstanceQuery().taskId(taskId).singleResult();
if (t == null) {
    Task active = taskService.createTaskQuery().taskId(taskId).singleResult();
    if (active != null) { /* task still running: use runtime endpoints */ }
}

HistoricTaskInstance t = historyService.createHistoricTaskInstanceQuery().taskId(taskId).singleResult();
if (t == null) { /* task not in history; check runtime taskService */ }

try { HistoricTaskInstance t = api.getHistoricTask(taskId); }
catch (FlowableObjectNotFoundException e) { /* fall back to runtime task query */ }

When it happens

Trigger: Any history task endpoint (getHistoricTaskInstanceFromRequestWithoutAccessCheck) with a taskId that does not exist, was never completed/persisted to history, or belongs to a different engine.

Common situations: Task is still active (not yet in history); using the runtime task id against history after the task was deleted without history; pointing at the wrong database/tenant; id truncation in client code.

Understand the failure class

Background: 'Could not be found', 'does not exist', 'not found in database': the resource-not-found family when an ID, slug, key, or URI lookup comes back empty — this error's family across 20 libraries.

Related errors

• Could not find a case instance with id '${caseInstanceId}'.
• Historic task instance '' variable value for couldn't be fo
• Historic variable instance '' couldn't be found.
• No historic task instance found with id:
• Could not find a process instance with id '" + processInstan

AI-assisted analysis of flowable/flowable-engine@d6d39ce1c6 (2026-09-11). Data as JSON: /api/errors/d67eea2e53ccc768. Report an issue: GitHub.