An extensive search for the data required to build the requested report was performed, but failed to retrieve the necessary quantitative information.

The following steps were taken:

1. Live Job Market Analysis: Queries were run against the live APIs of Poland's leading IT job boards, No Fluff Jobs and Just Join IT, for listings matching "C++" on B2B contracts. Both returned 0 results.
2. Economic Data Retrieval: A call to the Polish Central Statistical Office (GUS) database to retrieve national wage statistics also failed.
3. News and Report Search: A search of Polish news feeds for recent (2024-2025) and future-looking (2026) IT salary reports mentioning C++ did not locate any of the specific, named reports (e.g., from Hays, Michael Page, etc.) or provide concrete figures for salary ranges, specializations, or regional differences.

Conclusion:

Without foundational data from live job postings or comprehensive salary surveys, it is impossible to generate the requested detailed analysis of B2B rates, including breakdowns by seniority, specialization, and region, or to project trends for 2026. The request's level of detail requires access to specific, structured datasets that were not found with the available tools.

To proceed, it is recommended to:

• Provide a direct URL to a specific salary report if one is known.
• Widen the search terms to more general "IT software engineer" and then attempt to extrapolate, though this would be highly speculative.
• Try the query again later, as the lack of results on job boards may be a temporary anomaly.