mcs: fix primary parse (#9578)

[ti-chi-bot]

This is an automated cherry-pick of #9578

What problem does this PR solve?

Issue Number: Close #9579.

What is changed and how does it work?

Check List

Tests

• Unit test

Release note

None.

[codecov]

Codecov Report

❌ Patch coverage is 83.33333% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 77.74%. Comparing base (0d0a253) to head (e520056).
⚠️ Report is 13 commits behind head on release-8.5.

Additional details and impacted files

@@             Coverage Diff              @@
##           release-8.5   #10003   +/-   ##
============================================
  Coverage        77.74%   77.74%           
============================================
  Files              467      467           
  Lines            62474    62478    +4     
============================================
+ Hits             48570    48575    +5     
- Misses           10315    10323    +8     
+ Partials          3589     3580    -9     

Flag	Coverage Δ
unittests	77.74% <83.33%> (+<0.01%)	⬆️

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[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: JmPotato, rleungx

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• OWNERS [JmPotato,rleungx]

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[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2025-12-10 03:06:22.223304287 +0000 UTC m=+1010327.037081859: ☑️ agreed by JmPotato.
• 2025-12-10 07:42:58.838712846 +0000 UTC m=+1026923.652490418: ☑️ agreed by rleungx.