fix(agent-installer): pin Newtonsoft ToString overload to avoid GAC binding crash

[Richard Markiewicz (thenextman)]

Fixes a failure where installing or reconfiguring the Devolutions Agent could roll back with a MissingMethodException on machines that already have an older Newtonsoft.Json in the Global Assembly Cache (GAC).

The installer's managed (DTF) custom actions formatted agent.json via JObject.ToString(Formatting). That single-argument overload was introduced in Newtonsoft.Json 13.0.4, and the installer references 13.0.4. However, every Newtonsoft.Json 13.x release ships the same AssemblyVersion (13.0.0.0), so the CLR loads whichever 13.x copy is registered in the GAC in preference to the one bundled in the custom-action (SFXCA) payload. When an older 13.x is present in the GAC — commonly installed by Remote Desktop Manager, PowerShell 7, Dell Command, and many other products — the call fails with:

System.MissingMethodException: Method not found:
'System.String Newtonsoft.Json.Linq.JToken.ToString(Newtonsoft.Json.Formatting)'

and the whole MSI transaction rolls back during ConfigureFeatures.

The fix forces the two-argument ToString(Formatting, params JsonConverter[]) overload (by passing an empty converter array) at all three call sites. That overload exists in every 13.x release, so the custom actions now behave correctly no matter which 13.x wins assembly resolution. This required no version change and no change to what ships in the package.

Affected: Agent 2026.2.2 (first build to reference 13.0.4).

The Gateway installer (package/WindowsManaged) was checked as well. It references 13.0.3 and makes no ToString(Formatting) calls, so it is not affected today — though it shares the same structural exposure (strong-named Newtonsoft loaded by DTF custom actions, subject to GAC precedence) and should adopt the same overload discipline if it is ever bumped to 13.0.4+.

Reference: JamesNK/Newtonsoft.Json#3084

Issue: DGW-396

[github-actions]

Let maintainers know that an action is required on their side

• Add the label release-required Please cut a new release (Devolutions Gateway, Devolutions Agent, Jetsocat, PowerShell module) when you request a maintainer to cut a new release (Devolutions Gateway, Devolutions Agent, Jetsocat, PowerShell module)

• Add the label release-blocker Follow-up is required before cutting a new release if a follow-up is required before cutting a new release

• Add the label publish-required Please publish libraries (`Devolutions.Gateway.Utils`, OpenAPI clients, etc) when you request a maintainer to publish libraries (Devolutions.Gateway.Utils, OpenAPI clients, etc.)

• Add the label publish-blocker Follow-up is required before publishing libraries if a follow-up is required before publishing libraries

[Benoît Cortier (CBenoit)]

Thank you!

[Benoît Cortier (CBenoit)]

I’ll attach a ticket to the squash commit

[Benoît Cortier (CBenoit)]

Ticket: DGW-396