StepFunctionsStartExecution: Cannot pass Task Token using sfn.TaskInput.fromText

[luiscarlosjayk]

Describe the bug

I'm not able to write more complex jsonata exression that allows me to pass the TaskToken merged with other values within a same object for the input of the StepFunctionsStartExecution when the jsonata static method is used.

aws-cdk/packages/aws-cdk-lib/aws-stepfunctions/lib/fields.ts

Line 521 in 0ad4f3b

public static containsTaskToken(obj?: { [key: string]: any }): boolean {

If I use

tasks.StepFunctionsStartExecution.jsonata(this, 'StartAnotherSFN', {
    stateMachine: otherSFNReference,
    associateWithParent: true,
    integrationPattern: sfn.IntegrationPattern.WAIT_FOR_TASK_TOKEN,
    taskTimeout: sfn.Timeout.duration(cdk.Duration.minutes(1)),
    input: sfn.TaskInput.fromObject({
        token: '{% $states.context.Task.Token %}',
    }),
});

it works, but if try to use instead:

input: sfn.TaskInput.fromText(`{%
        "token": $states.context.Task.Token
%}`),

it doesn't.

And I needed to use sfn.TaskInput.fromText because I needed to use $merge method from jsonata to construct a more complex object.

Regression Issue

• Select this option if this issue appears to be a regression.

Last Known Working CDK Version

No response

Expected Behavior

I expected this to work:

tasks.StepFunctionsStartExecution.jsonata(this, 'StartAnotherSFN', {
            stateMachine: otherSFNReference,
            associateWithParent: true,
            integrationPattern: sfn.IntegrationPattern.WAIT_FOR_TASK_TOKEN,
            taskTimeout: sfn.Timeout.duration(cdk.Duration.minutes(1)),
            input: sfn.TaskInput.fromText(`{%
                "token": $states.context.Task.Token
            %}`),
});

Current Behavior

I get an error:
Error: Task Token is required in input for callback. Use JsonPath.taskToken to set the token.

Reproduction Steps

Try to use the StepFunctionsStartExecution task to call another step function with waitForTaskToken integration pattern and use sfn.TaskInput.fromText instead of fromObject to pass the Task Token.

Possible Solution

Revisit the regex pattern.

Additional Information/Context

No response

CDK CLI Version

2.190.0

Framework Version

No response

Node.js Version

22.14.0

OS

MacOS

Language

TypeScript

Language Version

5.8.3

Other information

No response

[pahud]

Current vs Expected

Hi @luiscarlosjayk,

Thank you for reporting this issue and providing detailed steps to reproduce.
You are right—currently, the CDK checks for the presence of the Task Token in your input using FieldUtils.containsTaskToken, but this check may not reliably detect the token if you use more advanced jsonata expressions or string templates inside TaskInput.fromText.

Why this happens:
The constructor for StepFunctionsStartExecution throws if it can't confirm that the Task Token is present in the input, which is required for the WAIT_FOR_TASK_TOKEN pattern.
If your string template or jsonata-based input is not detected by the check, you'll see the error.

Possible workaround:
For now, use TaskInput.fromObject({ token: '{% $states.context.Task.Token %}', ... }) if you can. If you must build up more complex objects, consider doing so programmatically before passing them to fromObject. Ensure that the string {% $states.context.Task.Token %} appears unambiguously in the input object.

Framework improvement:
It would be beneficial to enhance containsTaskToken to better recognize embedded task tokens in advanced inputs.
Would you be interested in helping improve this detection logic? Contributions are welcome! You can find the relevant function here.

Thanks again for your feedback and please let us know if you have further questions.
PRs are always welcome!