PlantUML Q&A - Recent questions

How to colorize each vertical grid-line under participant on sequence diagram

Fri, 17 Jul 2026 08:55:00 +0000

I want to easily differentiate vertical grid-lines by adding a color depending on the participant. (I use hudge sequence diagram and sometimes it is difficule to remender at which participant corresponds the vertical grid-line

Thanks

ports really need a revamp

Wed, 08 Jul 2026 17:44:37 +0000

ports in the component diagram are super useful, but they really need a lot of work. Both the default engine (puma?) and smetana produce incorrect results for the ports.

//www.plantuml.com/plantuml/png/HOrT2W8n48FVSuevobvbN8CkjjEXpJw8U7UBM7m8V87yR4FUTTQ2zFtXDveuP2zawph2xYovk19VRASi2ttmRpkb9x2tcYqOiYE2VUxOh-om5RxW3KnjZEjy_W00

Unmapped portout causes image to not render

Tue, 07 Jul 2026 17:16:29 +0000

Adding in a 3rd portout to an existing component causes the diagram to not render, removing it does render.

This only happens if I have a link with a label, if the link is unrelated to the component/portout

This happens in the old and new online editor, as well as a docker container I am running.

I tried to also increase the plantuml limit size in docker with no success.

UML source

@startuml
package "A" {
component "B" {
portout p1
portout p2
' Commenting out p3 will get this to render
portout p3
}
}
'unrelated link, must be with label
C -> p4 : X
' If I uncomment this following link to the 3rd port, the image will render; BUT only if the link includes the label
' C -> p3 : Y
@enduml

Docker compose

version: '3.8'
services:
plantuml:
image: plantuml/plantuml-server:tomcat
ports:
- "8080:8080"
environment:
- PLANTUML_LIMIT_SIZE=16384
- JAVA_OPTS=-Xmx2g # Allocates up to 2GB of RAM to the Java process

Exception in docker

Exception java.lang.IllegalStateException

net.sourceforge.plantuml.dot.UnparsableGraphvizException: java.lang.IllegalStateException

at net.sourceforge.plantuml.svek.GraphvizImageBuilder.buildImage(GraphvizImageBuilder.java:294)

at net.sourceforge.plantuml.svek.CucaDiagramFileMakerSvek.getTextBlock(CucaDiagramFileMakerSvek.java:82)

at net.atmp.CucaDiagram.getTextBlock(CucaDiagram.java:480)

at net.sourceforge.plantuml.UgDiagram.getExporter(UgDiagram.java:121)

at net.sourceforge.plantuml.UgDiagram.exportDiagram(UgDiagram.java:93)

at net.sourceforge.plantuml.servlet.DiagramResponse.sendMap(DiagramResponse.java:321)

at net.sourceforge.plantuml.servlet.MapServlet.doGet(MapServlet.java:57)

at jakarta.servlet.http.HttpServlet.service(HttpServlet.java:622)

at jakarta.servlet.http.HttpServlet.service(HttpServlet.java:710)

at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:128)

at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53)

at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:107)

at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:165)

at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:77)

at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:492)

at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:113)

at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:83)

at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:782)

at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:72)

at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:341)

at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:397)

at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:63)

at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:1272)

at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1801)

at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:52)

at org.apache.tomcat.util.threads.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:946)

at org.apache.tomcat.util.threads.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:480)

at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:57)

at java.base/java.lang.Thread.run(Thread.java:840)

Caused by: java.lang.IllegalStateException

at net.sourceforge.plantuml.svek.DotStringFactory.solve(DotStringFactory.java:358)

at net.sourceforge.plantuml.svek.GraphvizImageBuilder.buildImage(GraphvizImageBuilder.java:287)

... 28 more

Error image in plantuml running in docker

Problem using an skin with !include URL

Mon, 22 Jun 2026 19:22:29 +0000

Hi:

I've prototyped a new skin for SEMAT Essence[1]. I also want it to be used from the web (as others like C4 do)[2]. I checked and it works locally through the desktop PlantUML Editor and with the plantuml docker image, which is nice. But it doesn't work neither with https://www.plantuml.com/plantuml/uml or https://editor.plantuml.com/uml/. In the last one I got an «Cannot open URL» message (check demo), which is weird for me because all the URLs (the skin uses two files) are publicly accesible.

Am I doing something wrong? Is there maybe a whitelist to be added or so? Thanks in advance.

[1] https://codeberg.org/olea/essence-plantuml-skin/

[2] https://olea.org/essence-plantuml-skin/essence-macros.puml

How to pass raw latex code to the Tikz/LaTeX export

Tue, 09 Jun 2026 11:40:47 +0000

I really like the latex:nopreamble export feature, but to fully integrate it with my documents I would like to pass raw latex code to the exported file, i.e.

@startuml
A -> B: <raw> something \gls{glossary-entry} \autocite{cool-source} </raw>
@enduml

IDEF0 support

Wed, 27 May 2026 09:18:25 +0000

It would be great if PlantUML supported IDEF0 diagrams (https://en.wikipedia.org/wiki/IDEF0).

Syntax mistake in PlantUML Language Reference - 12.1 Complex Examples

Fri, 08 May 2026 18:55:22 +0000

The diagram does not match the provided uml/yaml. As written, it does not create the child elements of partridges:

partridges:
count: 1
location: "a pear tree"
turtle-doves: two

Should be (with spaces before count and location):

partridges:
count: 1
location: "a pear tree"
turtle-doves: two

Add pictures to participants in sequence diagramm

Thu, 07 May 2026 08:41:06 +0000

Hello all!

Is it possible to add a picture to the participant of a sequence diagram?

Many thanks in advance for your help.

Best regards,
J.B.

Why can't the old syntax for Activity-Diagram shapes no longer be supported?

Thu, 30 Apr 2026 08:12:34 +0000

We use a lot of activity Diagrams in our projects and need to change them from time to time. Now the old diagrams witch the syntax

 :FooBar>  
 :FooBar< 
 :FooBar|

etc. no longer work since they have instead to be written much longer using

:FooBar; <<StereoType>>

Is it realy such a big issue for the parser that it is not possible to stay compatible to previous versions?

I know the whole new actitivy syntax is marked as beta but it is such a long time already and people are using it - regardless of it being our fault to do so it would be nice if we had some kind of solution without needing to change all existing diagram sources...

Regex Subdiagram crashes PlantUML

Mon, 27 Apr 2026 18:04:38 +0000

This regex subdiagram crashes PlantUML, I am using a bundled with Pycharm version, but planttext and plantuml's online formatters crash the same.

Diagram:

@startuml
class A {
{{regex
title someRegex
^\s*(\d{4,5}-?\d{3,4}-?\d{1,2})
}}
}
@enduml

https://www.plantuml.com/plantuml/uml/SoWkIImgAStDuKhEIImkLd1KgEQghYvAJK-ju2h9BCb9LIZEpqqD0lFZOegrD69IgarqJ6jrxO4COnqJ2CDGnwXMawksbgkMoo4rBmLa7000

How to get the calculated dates from gantt chart?

Wed, 22 Apr 2026 15:30:32 +0000

Hello,

When using the gantt chart, I set the project start date and add the tasks and its dependecies, so the plantuml engine calculates the end's date of these tasks.

How can I get or see these end's date tasks?

Thank you.

Programming PlantUML in Rust

Wed, 22 Apr 2026 14:57:06 +0000

Wouldn't it be great if you no longer needed to install Java, but simply needed a directly executable file, e.g., Windows ".exe"?

PlantUML activity grammar

Wed, 15 Apr 2026 19:14:22 +0000

I need to build ANTLR PlantUML activity diagram lexer and parser for my university project, is there any documentation with PlantUML grammar rules that I can refer to, or only this page https://plantuml.com/activity-diagram-beta?

Class diagram duplicates packaged interface when referenced from another package

Wed, 15 Apr 2026 08:17:06 +0000

@startuml
package "App" as App {
  interface Interface
}

package "Adapters" as Adapters {
  class A implements Interface
  class B
}

B --> Interface
@enduml

results in duplicate Interface and concrete Interface, but should work as expected in: https://plantuml.com/class-diagram#27fe4eb3edbaff8f

Class diagram duplicates packaged interface when referenced from another package

Wed, 15 Apr 2026 08:15:51 +0000

@startuml
package "App" as App {
  interface Interface
}

package "Adapters" as Adapters {
  class A implements Interface
  class B
}

B --> Interface
@enduml

results in duplicated Interface and concrete Interface

Mutually exclusive tasks in Gantt Chart

Fri, 03 Apr 2026 05:14:43 +0000

G'Day,

I'm struggling with what I would have thought would be a simple thing in Gantt charts.

I have two [or more] tasks that are not dependent on each other, but require the same resource, so cannot be worked at the same time, exemplified by the following code:

@startgantt

Project starts 2026-04-06
Saturday are closed
Sunday are closed

[Task A] on {Me:100%} requires 5 days
[Task B] on {Me:100%} requires 3 days
[Task C] on {Me:100%} requires 2 days
[Task D] on {Me:100%} requires 5 days

[Task B] starts at [Task A]'s end
[Task C] starts at [Task A]'s end
[Task D] starts at [Task B]'s end
[Task D] starts at [Task C]'s end

@endgantt

This project could be completed by doing:

Task A, Task B, Task C, and Task D
Task A, Task C, Task B, and Task D
Task A, interleaving Tasks B and C, and Task D

Given that the order of tasks B and C doesn't matter, I'd be happy if the Gantt chart code picked option 1 as it's a valid solution.

What happens, however, is that I apparently clone myself and work both Task B and C concurrently for two days, completing the 15 days work in 13 elapsed days.

This produces the correct result:
[Task B] starts at [Task A]'s end
[Task C] starts at [Task A]'s end
[Task C] starts at [Task B]'s end with #FFFFFF00 link
[Task D] starts at [Task B]'s end
[Task D] starts at [Task C]'s end

Interestingly, this does not produce the correct result, scheduling Tasks C and D concurrently:
[Task B] starts at [Task A]'s end
[Task C] starts at [Task A]'s end
[Task D] starts at [Task B]'s end
[Task D] starts at [Task C]'s end
[Task C] starts at [Task B]'s end with #FFFFFF00 link

One extra invisible link isn't too much of an issue, but as a work-around it doesn't scale well.

Is there any way to enforce the resource constraint without adding extra dependencies?

Thanks,

Mark.

how to drow the collaboration diagram

Tue, 31 Mar 2026 17:51:10 +0000

@startuml not recognizing digraph (DOT) content after upgrade to 1.2026.0

Wed, 25 Mar 2026 11:12:52 +0000

After upgrading to PLantuml version 1.2026.0, digraph(Graphviz,DOT) content is not being processed correctly when wrapped inside @startuml/@enduml block.
Issue can be also seen in plantuml/dot page,
Link : https://plantuml.com/dot

Adding a note to start and end state

Mon, 23 Mar 2026 12:15:25 +0000

Hi!

How do I add a note to, say, "left of [*]"? And how would I specify which one (start or end) I mean?

The main problem I'm seeing is that I can't add anything to those states, no description and no notes.

I there any solution for this?

Reporting a diagram as requested when PlantUML threw an exception

Wed, 18 Mar 2026 11:06:37 +0000

Hi

I wanted to try the Elk layout as suggested in

https://forum.plantuml.net/20132/control-package-layout-in-class-diagram?show=20390

I put in the source below, and got an error message. At the top of the exception trace, it said "You should send this diagram and this image to plantuml@gmail.com or post to https://plantuml.com/qa to solve this issue." So that is what I am trying to do... when I tried to go to https://plantuml.com/qa it took me to forum.plantuml.net.

Here is the URL:

https://www.plantuml.com/plantuml/uml/ZLPFK_is4BtxKspfmOUMpWzA0dGO1WAaS81c23rrUX3sEjPWQzsLd91s-jrhsJJ8YaZiKxBlxUxRFv9zfOrWKvT5z5t5Ob4AACIQQWDOl4MnPvkNQ8GIKHJ3FASL_03V0p6iSc5mYGolc14Z20N269QljS4VGIfjKAH0cGLaGYgAzPjKbM1HGb88hQ__Ppyqw5p-ZV3DviWaQnDL8daJ2uI3sSUFqmEuk9WIJGJ33PKLALJcyX8W-YU2BY3S2wveofXkBFRFL1OuOqfGQ-8Uyeow8gNnNgYqG8x-jVar9gJIRG6Zi82j_BTI9xJ4pqot8ilMmLGcbnp8TFHjQArt9aTMQAmdcaajYnJv2mhJ-peCFMDF6e1K1ZaJ2S93I-p2tw9EM5Q6GXIlFg_DVzMeFqJsVVV0RUjsu7TOCPM_LmM9D8WlKPbWNREYDkGwTXF9g6QJRu_aVF_mVoNon-oDecMqSx39x6EtFGlb6m_TWBQE9kQ2HLaw2LjxUB_bUoZZsT2CywV7sSDlcp9iHBHj3iGy6NXa7Ycj2mnKqGt8AyD37uKI2ySwaKhmkZlqM6tEVLixoaKU4lhphkBTjR75-pAwXcoiFdsEl9G9tf0oGgeGutg1oZZXV4imYWksYzKRifB1WHmD6BBjNB2ptMdjtGAT_MNw4j3dWPx9EVYTSCyZ5uqw2ZRLuY6Vzh88U-mJs9wMdQwRApkywSS36kihc0YD_MGUmwPq7lTLs3o7XvVzLyOly8o5H0saFhcZ_Tmexc4D6Pu813EjD2HKIhK0gWrGPbzO-YT7oVbm9J0UeCIzZGO7FXbIedlKBRkkNFxnGHJ7SUIJFCfE_2oiBaGz_rBSKKTcUqqv7as90qYZ8QJn4D9fW9JIIeLQvj4yrRlWqMvul1i-3SEElEQ9NGFitsphyS9hC0HIPKMDAi6Fp-06AZ0p5chx1QbaJ8majVN1h3SVpEwE7lwHopH5zQVjfDU7ArHfNHR_0G00

Here is the source. Names are anonymised because the diagram belongs to my employer:

@startuml
!pragma layout elk

' Show + # or whatever before an attribute, instead of an icon
'skinparam classAttributeIconSize 0

' first
package "Package 7" <<FooBar Component>>
{
  class HarpoFred
  class FredFileProcessor
  class FredResponseHandler
}

' second
package "Package 5" <<FooBar Component>>
{
  class HarpoDiscover
  class DaffyResponseHandler
}

' third
package "Package 10" <<FooBar Component>>
{
  class HarpoEthernetPacketBuilder
  class HarpoEthernetProxy
  class HarpoEthernetReponseHandler
  interface IHarpoPacketDescriptor
  interface IHarpoResponseHandler
  class FredRequestPacket
  interface IFredRequestPacket
  interface IDaffyRequestPacket
  interface IEepromUploadPacket
  interface IEventHandler
  interface IPlutoUploadPacket
}

' fourth
package "Package 9" <<FooBar Component>>
{
  class GoofyResponseHandler
  class HarpoGoofyProxy
}

' fifth
package "Package 6" <<FooBar Component>>
{
  class HarpoPlutoProgrammer
  class PlutoResponseHandler
}

' sixth
package "Package 8" <<FooBar Component>>
{
  class HarpoSNMPIOProxy
}

' seventh
package "Package 4" <<FooBar Component>>
{
  class HarpoModuleProgrammer
  class UploadResponseHandler
  class UploadManager
  class BinaryFilePreprocessor
}

' eighth
package "Package 3" <<FooBar Component>>
{
  interface ISNMPHandler
  class SNMPIOHandler
  interface ISNMPServiceContainer
  interface ISNMPAgent
  class SNMPAgent
  class SNMPServiceContainer
  class SNMPGoofyHandler
}

' ninth
package "Package 1" <<FooBar Component>>
{
  class FileUploadManager
  class IFredDescriptor
  class TFTPServiceContainer
  class TFTPServer
  class TFTPFredRequestHandler
  class TFTPShampooHandler
  interface ITFTPHandler
  class TFTPDaffyHandler
  interface ITFTPServiceContainer
  class TFTPPlutoHandler
  interface ITFTPServer
}

' tenth
package "Package 2" <<FooBar Component>>
{
  class ServiceContainerBase
  interface IServiceContainer
}

"Package 7"    --> "Package 10" : Relies on
"Package 5"    --> "Package 10" : Relies on

' "Package 10" -- No arrows coming out of this.

"Package 9"    --> "Package 10" : Relies on
"Package 6"    --> "Package 10" : Relies on

"Package 8"    --> "Package 10" : Relies on
"Package 4"    --> "Package 10" : Relies on

'"Package 3"    -up-> "Package 2"
'''
"Package 3"    --> "Package 2"

"Package 3"    --> "Package 8" : Relies on
"Package 3"    --> "Package 9" : Relies on

'"Package 1"    -right-> "Package 4"
'"Package 1"    -right-> "Package 5"
'"Package 1"    -right-> "Package 6"
'"Package 1"    -right-> "Package 7"
'"Package 1"    -down-> "Package 2"
'''
"Package 1"    --> "Package 4"
"Package 1"    --> "Package 5"
"Package 1"    --> "Package 6"
"Package 1"    --> "Package 7"
"Package 1"    --> "Package 2"

' "Package 2" -- No arrows coming out of this.

' Try to influence layout

'left to right direction
'!pragma layout smetana

'"Package 4" -[hidden]down-> "Package 5"
@enduml

Bar chart diagram can't have an entry with value 0

Mon, 16 Mar 2026 11:07:11 +0000

@startchart
title Performance
h-axis [Q1, Q2, Q3, Q4]
v-axis -1 --> 1 ticks [-1:"false", 0:"nothing", 1:"true"]
bar [1, 1, 0, 1] #3498db
@endchart

i want to make my external actor go to the right of the system boundary can u write a plant uml code in draw.io for me?

Mon, 16 Mar 2026 10:27:45 +0000

@startuml
skinparam actorStyle stickman
left to right direction

' --- Styling ---
skinparam usecase {
    BackgroundColor<<Hub>> #FFCC99
    BackgroundColor<<Technical>> #E1D5E7
    BackgroundColor<<Action>> #FFFFFF
    BackgroundColor<<External>> #F5F5F5
}

' --- Actors (Left Side) ---
actor Passenger
actor "System Administrator" as SysAdmin

' --- System Boundary ---
rectangle "LongThangNaiKorTorMor System" {

    (View Station Maps) as UC2
    (Check Train/Bus Schedule) as UC3
    (Top up Travel Card) as UC4
    (View Travel History) as UC5
    (Report Issue) as UC6
    (Generate Payment QR / NFC) as UC_Pay
    (Check Crowd Density) as UC_Crowd
    (Plan Multi-Modal Journey) as UC1

    (Deploy System Updates) as UC13
    (Generate System Reports) as UC7
    (Handle Feedbacks) as UC8
    (API Management) as UC12
    (Manage User Accounts) as UC9
    (Monitor System Health) as UC11
    (Configure GTFS Data) as UC_GTFS

    (Login to Passenger Account) as LoginP <<Hub>>
    (Verify Wallet Balance) as VerifyW <<Hub>>
    (Login to Admin Panel) as LoginS <<Hub>>

    (Update Transit Channels) as T1 <<Technical>>
    (Upload Map Media) as T2 <<Technical>>
    (Set Route Milestones) as T3 <<Technical>>
}

' --- Actors (Right Side) ---
' Defining these AFTER the rectangle forces them to the right
actor "Payment Scanner" as Scanner <<External>>
actor "Transit Operator API" as TransitAPI <<External>>

' --- Relationships (Left) ---
Passenger --> UC1
Passenger --> UC2
Passenger --> UC3
Passenger --> UC4
Passenger --> UC5
Passenger --> UC6
Passenger --> UC_Crowd
Passenger --> UC_Pay

SysAdmin --> UC7
SysAdmin --> UC8
SysAdmin --> UC9
SysAdmin --> UC_GTFS
SysAdmin --> UC11
SysAdmin --> UC12
SysAdmin --> UC13

' --- Internal Logic ---
UC_Pay ..> LoginP : <<include>>
UC_Pay ..> VerifyW : <<include>>
UC4 ..> LoginP : <<include>>
UC5 ..> LoginP : <<include>>
UC9 ..> LoginS : <<include>>
UC11 ..> LoginS : <<include>>
UC12 ..> LoginS : <<include>>

UC_GTFS <.. T1 : <<extend>>
UC_GTFS <.. T2 : <<extend>>
UC_GTFS <.. T3 : <<extend>>

' --- Relationships (Right) ---
' Using the syntax "UseCase -- Actor" pushes the actor to the right
UC_Crowd -- TransitAPI
UC1 -- TransitAPI
UC_Pay -- Scanner

@enduml

Cross functional process flow diagram

Fri, 13 Mar 2026 14:17:12 +0000

Using corporate IT we can create cross functional process flows with the Excel standard cross functional process flow template which uses a visio addin to visualise the diagram from a simple spreadsheet list. However the diagram is plain and not very easy to read or use.

Plantuml currently allows the creation of simple process flows but not true cross functional process flows (twin axis) like in excel and visio and BPMN2.0. I believe that creating this capability will grow plantumls audience to cover business analysts alongside architects like myself and will be of greatest value to businesses.

If you choose to act upon this I would be most willing to support in anyway I could

the -cypher commandline option doesn't work for new syntax

Fri, 13 Mar 2026 12:42:20 +0000

when using the cypher option on the commandline, the cypher engine doesn't detect some of the "newer" syntax, which ends up breaking the build. certain lines in component diagrams like "package my_package as mp" don't get cyphered, but their use will. also skinparam groups with the "<<myskin>>" don't get scrambled either.

ports are still pretty buggy.

Thu, 12 Mar 2026 21:10:37 +0000

ports for component diagrams have come a really long way; but for mild complexity diagrams, they are still failing to align properly.

GANTT: IllegalArgumentException because of constraints

Mon, 09 Mar 2026 12:02:58 +0000

Testet with V1.2026.3beta 4 and V1.2026.2.

I have the following Example which does not work:

@startgantt MWE
'--- Grund‑Einstellungen ----------------------------------------------------
Project starts 2026-03-23
saturday are closed
sunday are closed
2026-04-03 to 2026-04-06 is closed
2026-05-01 is closed
2026-05-15 is closed
2026-05-25 is closed
hide resources footbox
printscale daily zoom 5
title "MEW"
footer Stand: 09.03.2026
language de
today is colored in green
'-------------------------------------------------------
[First Todo] as [a1] on {Res A} starts at 2026-03-23 and requires 1 day
[Second Todo] as [a2] on {Res A} requires 1 hour and starts at [a1]'s start
[Third Todo] as [a3] on {Res A} requires 3 days and starts at [a2]'s end
@endgantt

If I change the yellow highlighted part to start, everything works fine.

commandline page not updated

Sun, 01 Mar 2026 03:06:47 +0000

Hi! https://plantuml.com/command-line still having deprecated parameters.

I have tried to use the editor to update but to no avail.

Hope someone can follow up on this.

Smetana "UNSUPPORTED" crash

Fri, 27 Feb 2026 21:35:35 +0000

I have a large, ~900 line, class diagram. It worked ok with the Smetana layout engine, then I reordered it, and Smetana immediately started crashing. The default layout engine still works. Here is the error:

java.lang.UnsupportedOperationException: 2nnkwrdxg0ma2m482dqarlbz6
at smetana.core.Macro.UNSUPPORTED(Macro.java:131)
at gen.lib.pathplan.shortest__c.Pshortestpath(shortest__c.java:223)
at gen.lib.common.routespl__c._routesplines(routespl__c.java:421)
at gen.lib.common.routespl__c.routesplines(routespl__c.java:523)
at gen.lib.dotgen.dotsplines__c.make_regular_edge(dotsplines__c.java:1819)
at gen.lib.dotgen.dotsplines__c._dot_splines(dotsplines__c.java:659)
at gen.lib.dotgen.dotsplines__c.dot_splines(dotsplines__c.java:720)
at gen.lib.dotgen.dotinit__c.dotLayout(dotinit__c.java:415)
at gen.lib.dotgen.dotinit__c.doDot(dotinit__c.java:522)
at gen.lib.dotgen.dotinit__c.dot_layout(dotinit__c.java:577)
at gen.lib.dotgen.dotinit__c$2.exe(dotinit__c.java:569)
at gen.lib.gvc.gvlayout__c.gvLayoutJobs(gvlayout__c.java:186)
at net.sourceforge.plantuml.sdot.CucaDiagramFileMakerSmetana.getTextBlock(CucaDiagramFileMakerSmetana.java:535)
at net.sourceforge.plantuml.sdot.CucaDiagramFileMakerSmetana.createFileLocked(CucaDiagramFileMakerSmetana.java:490)
at net.sourceforge.plantuml.sdot.CucaDiagramFileMakerSmetana.createFile(CucaDiagramFileMakerSmetana.java:464)
at net.atmp.CucaDiagram.exportDiagramInternal(CucaDiagram.java:529)
at net.sourceforge.plantuml.classdiagram.ClassDiagram.exportDiagramInternal(ClassDiagram.java:129)
at net.sourceforge.plantuml.UmlDiagram.exportDiagramNow(UmlDiagram.java:162)
at net.sourceforge.plantuml.AbstractPSystem.exportDiagram(AbstractPSystem.java:260)
at net.sourceforge.plantuml.PSystemUtils.exportDiagramsDefault(PSystemUtils.java:251)
at net.sourceforge.plantuml.PSystemUtils.exportDiagrams(PSystemUtils.java:140)
at net.sourceforge.plantuml.SourceFileReaderAbstract.getGeneratedImages(SourceFileReaderAbstract.java:242)
at net.sourceforge.plantuml.Run.manageFileInternal(Run.java:393)
at net.sourceforge.plantuml.Run.lambda$processInputsInParallel$12(Run.java:350)
at net.sourceforge.plantuml.Run.lambda$processInParallel$14(Run.java:366)
at java.base/java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:545)
at java.base/java.util.concurrent.FutureTask.run(FutureTask.java:328)
at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1090)
at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:614)
at java.base/java.lang.Thread.run(Thread.java:1474)

I can't share the diagram, since it is not public information. I tried to make a minimal reproducible example, but the crash does not occur if I use just the first half of the diagram or just the last.

Version:

PlantUML version 1.2026.1 (Sun Jan 18 03:44:32 PST 2026)
(BSD source distribution)
Java Runtime: OpenJDK Runtime Environment
JVM: OpenJDK 64-Bit Server VM
Default Encoding: UTF-8
Language: en
Country: CA
PLANTUML_LIMIT_SIZE: 4096
Dot version: dot - graphviz version 2.44.1 (20200629.0846)
Installation seems OK. File generation OK

NullPointerException with 1.2026.1, works with 1.2025.10

Tue, 24 Feb 2026 12:21:45 +0000

With 1.2026.1, this code leads to the exception below.

@startuml
skinparam MaxMessageSize 250
skinparam SequenceMessageAlignment direction
a -> b: lorem ipsum lorem ipsum lorem ipsum
@enduml

It used to work with 1.2025.10.
Thanks for looking into this!

An error has occured : java.lang.NullPointerException
You Shall Not Pass

PlantUML (1.2026.2beta3) has crashed.

Diagram size: 5 lines / 136 characters.

Java Runtime: OpenJDK Runtime Environment
JVM: OpenJDK 64-Bit Server VM
Default Encoding: UTF-8
Language: en
Country: US

PLANTUML_LIMIT_SIZE: 4096

You should send this diagram and this image to
plantuml@gmail.com
or
post to
https://plantuml.com/qa
to solve this issue.
You can try to turn around this issue by simplifing your diagram.

java.lang.NullPointerException
net.sourceforge.plantuml.klimt.creole.SheetBlock1.getCoef(SheetBlock1.java:184)
net.sourceforge.plantuml.klimt.creole.SheetBlock1.getCoef(SheetBlock1.java:180)
net.sourceforge.plantuml.klimt.creole.SheetBlock1.initMap(SheetBlock1.java:166)
net.sourceforge.plantuml.klimt.creole.SheetBlock1.calculateDimension(SheetBlock1.java:195)
net.sourceforge.plantuml.klimt.creole.SheetBlock2.calculateDimension(SheetBlock2.java:91)
net.sourceforge.plantuml.skin.AbstractTextualComponent.getPureTextWidth(AbstractTextualComponent.java:103)
net.sourceforge.plantuml.skin.AbstractTextualComponent.getTextWidth(AbstractTextualComponent.java:108)
net.sourceforge.plantuml.skin.rose.ComponentRoseArrow.getPreferredWidth(ComponentRoseArrow.java:348)
net.sourceforge.plantuml.sequencediagram.graphic.MessageArrow.getArrowYStartLevel(MessageArrow.java:167)
net.sourceforge.plantuml.sequencediagram.graphic.Step1Message.prepareMessage(Step1Message.java:103)
net.sourceforge.plantuml.sequencediagram.graphic.DrawableSetInitializer.prepareMessage(DrawableSetInitializer.java:543)
net.sourceforge.plantuml.sequencediagram.graphic.DrawableSetInitializer.createDrawableSet(DrawableSetInitializer.java:166)
net.sourceforge.plantuml.sequencediagram.graphic.SequenceDiagramFileMakerPuma2.<init>(SequenceDiagramFileMakerPuma2.java:107)
net.sourceforge.plantuml.sequencediagram.SequenceDiagram.getSequenceDiagramPngMaker(SequenceDiagram.java:299)
net.sourceforge.plantuml.sequencediagram.SequenceDiagram.exportDiagramInternal(SequenceDiagram.java:315)
net.sourceforge.plantuml.UmlDiagram.exportDiagramNow(UmlDiagram.java:120)
net.sourceforge.plantuml.AbstractPSystem.exportDiagram(AbstractPSystem.java:215)
net.sourceforge.plantuml.servlet.DiagramResponse.sendDiagram(DiagramResponse.java:159)
net.sourceforge.plantuml.servlet.UmlDiagramService.doGet(UmlDiagramService.java:106)
javax.servlet.http.HttpServlet.service(HttpServlet.java:529)
javax.servlet.http.HttpServlet.service(HttpServlet.java:623)
org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:197)
org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:142)
org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:51)
org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:166)
org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:142)
org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:166)
org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:88)
org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:481)
org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127)
org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:83)
org.apache.catalina.valves.StuckThreadDetectionValve.invoke(StuckThreadDetectionValve.java:185)
org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:72)
org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:344)
org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:398)
org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:63)
org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:935)
org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1831)
org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:52)
org.apache.tomcat.util.threads.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:973)
org.apache.tomcat.util.threads.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:491)
org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:63)
java.base/java.lang.Thread.run(Thread.java:829)

in class Diagram ,what does "#--"、“^--”、“x--”、“}--”、“+--” mean

Tue, 24 Feb 2026 07:48:38 +0000

How to simulate 0.5Hz clock in Timing-diagram

Sun, 15 Feb 2026 16:53:41 +0000

Hello,

how can I create cloack using floating numbers? For example a 0.5Hz clock.

clock clk with period 0.5

throws an error.

Faking a clock using a binary signal in the preprocessor is not working either as %string(...) can convert integers or strings to string form — but it cannot evaluate or stringify a non‑integer expression.
See the code below.

@startuml

binary "CLK" as CLK

!$t = 0
!$state = 0
!$max = 8

!while $t <= $max
@%string($t)
!if $state == 0
CLK is low
!$state = 1
!else
CLK is high
!$state = 0
!endif
!$t = $t + 1
!endwhile

@enduml

Mismatched and incompatible versions between online server and downloadable jar.

Thu, 12 Feb 2026 19:39:16 +0000

I noticed that the latest version of the plantuml jar I can download for local rendering is 1.2026.1, while the online server is running 1.2026.beta3.

When creating an activity diagram the non beta version wants this:
#green:Test;

The beta version wants this:
:Test;<<#lawngreen>>

Each of the server versions will not accept the alternative, beta3 produces a warning, 1.2026.1 creates an error.

I was trying to share a diagram with my team and saw unexpected output.

Could the version running on the online server be available for download to retain portability?

IllegalStateException while attempting to rename nested state

Wed, 11 Feb 2026 14:59:46 +0000

I am not certain, this is a bug, but the compiler thinks so, hence this post.

Actual behavior

With the following code:

@startuml
hide empty description 

state state1.idle as "This is the idle state"
state state1.over
state1.idle --> state1.over

@enduml

I get the correct result (the display name of the state state1.idle is changed):

However with the following code:

@startuml
hide empty description 

state state1 as "Toplevel state"
state state1.idle as "This is the idle state"
state state1.over
state1.idle --> state1.over

@enduml

I get the following exception:

Expected behavior

I would expect the result to be akin to the following:

@startuml
hide empty description 

state state1 as "Toplevel state" {
    state idle as "This is the idle state"
    state over
    idle --> over
}

@enduml

I am not entirely sure this is a bug, this may very well be misuse of the namespace syntax.

notes attached to class member useless if left to right direction

Tue, 10 Feb 2026 09:08:14 +0000

Note left or right of specific class members looks messy when using left to right direcion:

```
@startuml

left to right direction

class a {
field1
field2
field3
}

note right of a::field2
first field
end note

note left of a::field3
another field
end note

@enduml

compare to top to bottom direction:

How to change printscale quarterly so Q1 starts on a February rather than January ?

Thu, 29 Jan 2026 11:33:43 +0000

we plan to quarters but those quarters are not based on the gregorian calendar.

They are based on when our fiscal year starts.

For us, thats always February so being able to set the date that the quarter starts on would allow us to enter actual dates rather than offset them so it shows correctly in the Gantt but then doesnt match the real dates.

Alternatively being able to set Starts at as a quarter e.g. "Starts At 2026Q2 and lasts one quarter" would be useful.

Is there a syntax where either of these already work or they would be feature requests ?

Thanks in advance

Problem with !include using relative paths in v1.2026.0?

Wed, 28 Jan 2026 15:14:43 +0000

I have just upgraded from v1.2025.10 to v1.2026.0 and all the punl files I have that us !include with a relative path now fail, for example:

@startuml 
!include ../../.theme/theme.puml

Is this a known issue, or a deliberate change?

Is there an Open Feature / Issue to improve SVG Sprite handling - I've got an experiment would like to propose as a PR

Wed, 28 Jan 2026 01:04:25 +0000

I've had some time to work on another implementation of Sprite SVG Parsing.

I am wondering if there is an open feature / features on this already or if I should create one?

Have gone down the path of:
- Adding Batik library to parse SVG Sprite elements
- A new Interface ISvgParser extends Sprite
-- has method void drawU(UGraphic ug, double scale, HColor fontColor, HColor forcedColor)
- 2 SVG Sprite parsing implementations that implement the ISvgParser, SvgNanoParser (existing) and SvgDomParser (New)
- SvgDomParser uses Dom logic on SVGs vs. Text/Regex and have been able to add more SVG handling features (most common but not everything)

This discussion has some enhancments, if there is no specific Feature request yet I'll create a new one.
https://github.com/plantuml/plantuml/discussions/1066

Add task start date and finish date to GANTT label

Tue, 27 Jan 2026 02:52:12 +0000

Hello, I would like to propose a feature for the plantuml GANTT charts:

Add an option to show the calculated start and end date of every task in the task label.

This could optionally also be shown at the left ot the chart in addition to the current behaviour.

Final proposed behaviour:

There is a new section left of the main chart showing per task row: the task name, start date and end date. Optional: also the duration of a task can be shown in this left area.
Inside the main chart the task name is shown, and optionally again the start and/or end date, with start date shown left and finish date showing right of the task name label and the chart bar.

I prefer to present the date always in the format YYYY-MM-DD. This should be adjustable of course.

Rationale:

I work with multi-year project plans, and the daily print scale makes the chart very large. So I am primarily using a weekly or monthly print scale. But with this less detailed scale the information of exact start and end dates is lost and not shown in the current behaviour. To be very precise in project communication I always need exact start and end dates for every single task, shown on the same page like the chart, also in weekly or yearly print scales.

Thanks and best regards

Preferred use of qualified name (absolute vs. relative names)

Mon, 26 Jan 2026 09:37:36 +0000

Dear all, it seems that there are different ways to use qualified names (which are not well documented, unless I am mistaken). In the following simple example. I like to declare an association between the classes A and B which are in the packages p1 and p2, respectively.

PlantUML can create a duplicate of a referenced classifier, since it interprets a qualified name as a relative path unless it is prefixed with a dot or the first segment of the qualified name is already known. See below for an example. Is there a preference to use qualified names?

@startuml
' does not work: p2 is interpreted as subpackage of p1, B is duplicated
package p1 {
class A { }
A -- p2.B
}

package p2 {
class B { }
}
@enduml

@startuml
' forward declaration of p2, works
package p2 {}

package p1 {
class A { }
A -- p2.B
}

package p2 {
class B { }
}
@enduml

@startuml
' absolute qualified names using a preceding dot

package p1 {
class A { }
A -- .p2.B
}

package p2 {
class B { }
}
@enduml

@startuml
' enclosing with single root, works

package root {
package p1 {
class A { }
A -- root.p2.B
}

package p2 {
class B { }
}
}
@enduml

Line on WBS diagram isn't straight

Tue, 20 Jan 2026 10:53:39 +0000

The line between "org" and "example" isn't straight on the WBS diagram below:

@startwbs
!theme cerulean
* org
** example
***< france
**** paris
**** lyon
**** burgundy
***> belgium
**** brussels
@endwbs

Crash observed when generating a SVG image from a Seqeunce Diagram with Embedded Salt

Fri, 16 Jan 2026 14:37:08 +0000

Dear Team

Version = 1.2026.0

The following code results in a crash (when SVG image is generated). PNG image is generated correctly.

@startuml
Participant Alice
Participant Bob

Alice -> Bob : Hi

note right of Bob
  {{
   salt
  {^"My group box"
  Login | "MyName "
  Password | "**** "
  [Cancel] | [ OK ]
  }
  }}
end note
@enduml

Timing diagram constraints overlapping

Thu, 15 Jan 2026 10:11:53 +0000

Hello,

I encounter the same pb. Arrows of constraints are overlapping (not the names), and it make the diagram not clear. Is there a way to manage that correctly ?

@startuml
robust "Tracker Board" as Track
concise "Article" as ART

ART is ""
Track is Idle

@118 as :T_critical_path_begin
@133 as :T_critical_path_end

@0
ART is "B pos."
@+10
ART is ""
@2
Track is "Trigger Acq"
@3
Track is "Idle"

@53
ART is "F pos."
@+10
ART is ""
@55
Track is "Trigger Acq"
@56
Track is Idle

@65
Track is "Consolidate verdict"
'163ms - 5ms
@68
ART is "D. pos" : "Reject decision position"
@+10
ART is ""
@71
Track is "Command reject valve"

@+2
Track is Idle

@Track
@2 <-> @3 : {T_trig_pos_B}
@2 <-> @65 : {T_trig_base_to_all_res_recv}
@55 <-> @56 : {T_trig_pos_F}

highlight :T_critical_path_begin to :T_critical_path_end #LightGoldenRodYellow : Critical path

@enduml

Gantt: days off break tasks dependencies

Wed, 14 Jan 2026 13:24:51 +0000

@startgantt
hide resources names
[Task1] on {Alice} requires 5 days and starts 2026-01-15
then [Task2] on {Alice} requires 5 days
{Alice} is off on 2026-01-19
@endgantt

Task2 should start on 2026-01-21, but it starts one day earlier and it overlaps the last day of Task1.

If you remove Alice's day off, then it renders ok.

architectural and Detailed Design as per the requirements . Include any design constraints

Wed, 14 Jan 2026 07:03:07 +0000

Uneven spacing between box items

Wed, 14 Jan 2026 06:12:26 +0000

How can I keep the spacing between box elements (Proxmox VE, Keycloak OIDC, and Okta SAML as seen in the attached sandbox) the same?

//www.plantuml.com/plantuml/png/ZP5DYzim48Rl-XM3hy4bRMy1btMpBPXksT2blIloa1NMXv76o-RVLwFQSXrQs9CJpQl7pxo-YoG3JTO8EP5taprZ477GRfH1MZZxruWZlD_lXI1D1g7wXbTbl1o0F7mCFPpI_IiyjTyVeBk7py4F62eXf28Vu6V403B2b9v291fKf-1VRVhnXE55Awm4m9WGMkbHEbhdlxvKV7DyGO6kPvCPK0GUk_iZTFtf5h5DPCgW_0tbSI09TVR-y6x_Jmn7SY0ZVFgtCfe6EgT9Iq9uy1Vlk8v5lMa4Bmpr9zQ7tUu0hL8Ouv8GV5odSOuTqZ56TCGaxU2h3tO3EAIo32g2pM9RI5qVu0VsEd2EV8aMKAg0JLPjPlnve-3PstGuMNHoGUr4pmpulqg95GftoJB5XLi6arrujc4LdUEpD0RT1Gk7dyo1exUZGSBR37Dcu6x7ujFPwhz9F5psuaoAy3TkOxfDshl8gotV8GVcsTnSFbvT-VI2VIfPt2NEPCrl

EDIT: Noticed I posted a PNG instead of a link to the sandbox. Here's the code:

@startuml
autonumber
title "Keycloak to 3rd Party SAML ID Broker"
actor User as user
box "Proxmox Service"
participant "Proxmox VE" as pve
end box
box "Keycloak OIDC IdP"
participant "Keycloak OIDC" as kco
end box
box "Okta - SAML2.0 IdP"
participant "Okta SAML" as okta
end box

== Initiate Logon to Proxmox ==
user -> pve ++: Access Proxmox
pve --> user : Present Login Form
user -> pve : Select Keycloak OIDC
pve --> user : Redirect to Keycloak
user -> kco ++: Initiate OIDC Login
kco --> user : Present Login Form
user -> kco : Select Okta Auth
kco --> user : Redirect to Okta Auth
user -> okta ++:Initiate SAML login
okta -> user : Present Challenge
user -> user ++: Complete Challenge
user -> okta --: Submit Challenge
okta -> kco --: Send Assertions
kco -> pve --: Assert Login
pve -> user --: Logged In
@enduml

Can I use UML notes (comments) notation in PlantUML according to the UML standard specification?

Sat, 10 Jan 2026 10:12:57 +0000

Hello! Happy new year!

I searched the forum for questions about UML notes but none seems to be related to mine.

PlantUML provides the ability to include notes in UML diagrams. Besides floating notes, notes can also be connected to elements as balloons. However, the balloon style apparently is not compatible with the UML Specification.

I managed to achieve the expected format in Class Diagrams, but I can't use such format in other diagrams. Currently I'm trying to do so in activity diagrams - and I'm not succeeding at all. :)

Please keep in mind that I'm not talking about drawing notes with dashed borders, but about the connection between notes and the corresponding elements (which can't be set in PlantUML for activity diagrams and others, AFAIK).

I brought the content of UML Specification to clarify my request. Here's how UML Specification defines the visual notation:

A Comment is shown as a rectangle with the upper right corner bent (this is also known as a “note symbol”). The rectangle contains the body of the Comment. The connection to each annotatedElement is shown by a separate dashed line. The dashed line connecting the note symbol to the annotated element(s) may be suppressed if it is clear from the context, or not important in this diagram.
Sources:
- UML 2.4.1 Infrastructure, Section 9.5.1 - Comment, pages 37-38
- UML 2.4.1 Infrastructure, Section 7.2.4 - Notation, page 22

Is it already implement and I'm missing something? Otherwise, would it be possible to include this in PlantUML? Maybe using <style>?

I believe this applies to all UML diagrams.

Thanks in advance!

Left constraint for self-transitions is not taken into account in state diagrams

Fri, 09 Jan 2026 18:40:39 +0000

PlantUML version : v1.2025.4

@startuml
[*] --> A
A -left-> A : left expected FAIL
A -right-> A : right expected
A --> [*]
@enduml

How to increase heap size for plantuml-server running in container?

Tue, 06 Jan 2026 17:12:05 +0000

I am running plantuml-server (jetty) in a container, and I am getting OutofMemoryError: java.heap.space" for one larger diagram.

I tried increasing the heap by adding

```
environment:
- JAVA_OPTIONS=-Xmx512m

```

to my docker-compose file. But that does not seem to have any effect?

How does the new syntax of activity diagrams achieve the pointing of corresponding arrows?

Sat, 03 Jan 2026 15:51:15 +0000

The old syntax of activity diagrams achieves arrow conversion through keywords such as down, but the new syntax does not support the down keyword.

-down-> (default arrow)
-right-> or ->
-left->
-up->

As shown in the activity diagram of the new grammar below, how can the pointing of arrows be achieved：

@startuml
start
:"First Activity";
:"Second Activity;
:"Third Activity";
stop
@enduml

The Gap - a freespace bug after extentending nodes in nwdiag

Fri, 26 Dec 2025 11:32:22 +0000

There is like,a gap between dev3 and DPx. Or maybe its a variation where gap is between web3 and PPx. Anyway I believe its a bug. I know the nwdiag is an [Amazing and totally not bugged out diagramm code] yet still I want to at least know how to workaround with this.

So, that is code:

@startuml

nwdiag {

group YProd{

web1

web2

}

group YDev{

dev1

dev2

}

group YUat{

uat1

uat2

}

network Public {

color = "red"

Q -- web1

web1 -- web2

web2 -- web3

vd -- dev1

dev1 -- dev2

dev2 -- dev3

vu -- uat1

uat1 -- uat2

uat2 -- uat3

vg1

vg1 -- git1

vg2

vg2 -- git2

}

network Private {

color = "palegreen"

width = full

web3 -- PPx

uat3

dev3 -- DPx

DPx -- Ddb

PPx -- Pdb

git1

git2

}

@enduml