# Bug? system.tag.readBlocking(ClientTag)

**URL:** <https://forum.inductiveautomation.com/t/bug-system-tag-readblocking-clienttag/106597>\
**Category:** Ignition\
**Tags:** vision\
**Created:** [May 22, 2025, 8:10pm UTC](https://forum.inductiveautomation.com/t/bug-system-tag-readblocking-clienttag/106597 "2025-05-22T20:10:50Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![MMaynard](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/mmaynard/32/3366_2.png) [@MMaynard](https://forum.inductiveautomation.com/u/MMaynard)\
**Post date:** [May 22, 2025, 8:10pm UTC](https://forum.inductiveautomation.com/t/bug-system-tag-readblocking-clienttag/106597/1 "2025-05-22T20:10:50Z")

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So I got notified today that something that works everywhere else is not working in the following situation.

A normal  
`system.tag.readBlocking("[default]SingleTag").value`  
returns the value.  
If you do this against a single client tag,  
`system.tag.readBlocking("[client]SingleTag").value`  
it comes back with  
`attributeError: 'java.util.ArrayList' object has no attribute 'value'`

We put the [0] in there and it reads fine, I understand the error and how to work around it, but I am not sure why it only does this when reading client tags vs tag provider tags?

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**Author:** ![Kevin.Herron](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/kevin.herron/32/7259_2.png) [@Kevin.Herron](https://forum.inductiveautomation.com/u/Kevin.Herron)\
**Post date:** [May 22, 2025, 8:27pm UTC](https://forum.inductiveautomation.com/t/bug-system-tag-readblocking-clienttag/106597/2 "2025-05-22T20:27:50Z")

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> [@MMaynard](#):
>
> A normal  
> `system.tag.readBlocking("[default]SingleTag").value`  
> returns the value.

Does it though? It doesn't for me...

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<div class="post-metadata">

**Author:** ![David\_Stone](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/david_stone/32/79749_2.png) [@David\_Stone](https://forum.inductiveautomation.com/u/David_Stone)\
**Post date:** [May 22, 2025, 8:30pm UTC](https://forum.inductiveautomation.com/t/bug-system-tag-readblocking-clienttag/106597/3 "2025-05-22T20:30:23Z")

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> [@MMaynard](#):
>
> A normal  
> `system.tag.readBlocking("[default]SingleTag").value`  
> returns the value.

This is the bug, this isn’t normal at all. According to the docs, ‘readBlocking()’ is supposed to return a List. I have always needed to use [0] for reliable results.

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<div class="post-metadata">

**Author:** ![MMaynard](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/mmaynard/32/3366_2.png) [@MMaynard](https://forum.inductiveautomation.com/u/MMaynard)\
**Post date:** [May 22, 2025, 8:43pm UTC](https://forum.inductiveautomation.com/t/bug-system-tag-readblocking-clienttag/106597/4 "2025-05-22T20:43:35Z")

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Acchuuually.. We're the bug.

`system.tag.read("[default]SingleTag").value`

works...  
It also works against a client tag...  
So half assed the trying to bring it up to the newer readBlocking...  
🤦‍♂️