Steps to reproduce:

Open the attached project
Select QA > Run F-114 (it registers a Smart Strings template "loop" whose content is "{:t:loop}", then calls Smart.Format("{:t:loop}"))
Observe the Editor

Actual results: The nested-template control prints "[inner]!", then the Editor process terminates at the self-referencing Format call. No exception reaches the caller (a try/catch around Format does not run)

Expected results: The recursion is detected and reported as a FormattingException that names the template, and the Editor keeps running

Reproducible with versions: 6000.7.0b2, 6000.7.0b6, 7000.0.0a12

Can't test with versions: 6000.0.84f1, 6000.3.24f1, 6000.6.7f1 (the Smart Strings module ships from 6000.7)

Tested on (OS): macOS 27.0.1 (Apple M1 Max)

Notes:

Two templates that reference each other ("a" uses {:t:b}, "b" uses {:t:a}) crash the same way
Also kills a built macOS Player (exit 139), not only the Editor
On 6000.7.0b6 the process exits with nothing logged; on 7000.0 the log ends with "Stack overflow."

First lines of Stack Trace:

Stack overflow.
   at Unity.SmartStrings.Pooling.SmartPools.FormattingInfoPool+<>c.<.cctor>b__3_0()
   at Unity.SmartStrings.Core.Formatting.FormattingInfo.FormatAsChild(Unity.SmartStrings.Core.Parsing.Format, System.Object)
   at Unity.SmartStrings.Extensions.TemplateFormatter.TryEvaluateFormat(Unity.SmartStrings.Core.Extensions.IFormattingInfo)
   at Unity.SmartStrings.SmartFormatter.EvaluateFormatters(Unity.SmartStrings.Core.Formatting.FormattingInfo)
   at Unity.SmartStrings.SmartFormatter.Format(Unity.SmartStrings.Core.Formatting.FormattingInfo)