ECS Exec - reference task by task arn rather than ID

[ecandostuff]

Describe the bug

In the ecs exec docs, it shows I can reference a task either by ID or by task arn. At the bottom of the docs, it then goes on to provide a sample command which references the task by it's full arn.

However, when I try to reference a task by arn (which I need to do based on how resources are formatted in my organization's IAM policies), I get the following error:
An error occurred (InvalidParameterException) when calling the ExecuteCommand operation: task length should be one of [32,36]

The command works fine with the task ID, but then it references the task in the format arn:aws:ecs:{region}:{acc-number}:task/{id} rather than including the cluster name in the middle like we would expect and shows in the arn in the console. This leads to the resulting resource name not aligning with the expectation for resource naming in my org's IAM policies.

Regardless of the issue in the paragraph above, the docs reflect that you can reference task by either arn or ID. If you aren't going to support arn as a way to reference a task, remove it from the docs.

Regression Issue

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

Expected Behavior

I can run the aws ecs execute-command function with a task arn rather than task id

Current Behavior

I get an error An error occurred (InvalidParameterException) when calling the ExecuteCommand operation: task length should be one of [32,36] when I try to run the aws ecs execute-command function with a task arn rather than task id

Reproduction Steps

Run this command from the ecs exec docs:

aws ecs execute-command
--cluster MyCluster
--task arn:aws:ecs:us-east-1:123456789012:task/MyCluster/d789e94343414c25b9f6bd59eEXAMPLE
--container MyContainer
--interactive
--command "/bin/sh"

Possible Solution

remove whatever length validation has been put in place on the task attribute for the ecs execute-command function

Additional Information/Context

No response

CLI version used

2.33.15

Environment details (OS name and version, etc.)

MacOS

[adev-code]

Hello @ecandostuff, thanks for reaching out. I created a task and I have tried to replicate the commands above and I was able to open an interactive shell session. I did not get the error/issue. The commands I have tried are:

$ aws ecs execute-command \
    --cluster MyCluster \
    --task arn:aws:ecs:us-east-1:[REDACTED]:task/MyCluster/4[REDACTED]a \
    --container MyContainer \
    --interactive \
    --command "/bin/sh" \
    --debug

$ aws ecs execute-command \
    --cluster MyCluster \
    --task 4[REDACTED]a \
    --container MyContainer \
    --interactive \
    --command "/bin/sh" \
    --region us-east-1 \
    --debug

OUTPUT:
2026-02-06 09:27:52,592 - MainThread - urllib3.connectionpool - DEBUG - https://ecs.us-east-1.amazonaws.com:443 "POST / HTTP/1.1" 200 2170
2026-02-06 09:27:52,597 - MainThread - botocore.hooks - DEBUG - Event after-call.ecs.DescribeTasks: calling handler <bound method RetryQuotaChecker.release_retry_quota of <botocore.retries.standard.RetryQuotaChecker object at 0x10a567620>>
Starting session with SessionId: ecs-execute-command-[REDACTED]
/ # exit

Exiting session with sessionId: ecs-execute-command-[REDACTED].

I have tried to replicate the error by making my ID longer by just adding random characters that makes the ID invalid, and the service gave an error (not the AWS CLI). The service gave 400:

2026-02-06 09:31:42,171 - MainThread - urllib3.connectionpool - DEBUG - https://ecs.us-east-1.amazonaws.com:443 "POST / HTTP/1.1" 400 87
2026-02-06 09:31:42,172 - MainThread - botocore.parsers - DEBUG - Response body:
b'{"__type":"InvalidParameterException","message":"task length should be one of [32,36]"}'

An error occurred (InvalidParameterException) when calling the ExecuteCommand operation: task length should be one of [32,36]

Could you please provide the full --debug logs and redacting any security or sensitive information? Also, please ensure to have the correct ID and length given by the service.

[github-actions]

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