A molecular modeling session can depend on more than the SAMSON application itself. You may also rely on Extensions for particular tools or workflows. So when an Extension does not load—or does not update—it is natural to wonder whether the Extension is broken, whether its displayed version is too old, or whether you need to reinstall it.
A useful first check is the SAMSON SDK version used to build the Extension. SAMSON uses that version, rather than the Extension’s own version number, to determine compatibility.
Two version numbers, two different jobs
Each Extension has its own major.minor.patch version. Developers can use it to communicate changes to users, but SAMSON does not enforce a policy for how that number should change. It is not the compatibility test.
The compatibility check compares the SDK version used to build the Extension with SAMSON’s internal version. The documented rule is that an SDK version is compatible when:
- The SDK and SAMSON have the same major version number.
- The SDK minor version is smaller than SAMSON’s minor version.
For example, an Extension built with SDK 1.5.2 can load in SAMSON 1.7.8: both use major version 1, and the SDK minor version, 5, is lower than SAMSON’s, 7. By contrast, an Extension built with SDK 1.8.5 does not meet the compatibility rule for SAMSON 1.7.8. It may depend on functionality that that SAMSON version does not have.
Why an Extension’s own version can mislead
Imagine two Extensions both labeled 2.0.0. That label alone does not tell you whether either one will load in your installation. If they were built using different SDK versions, their compatibility with your SAMSON version may differ. Conversely, an Extension’s version number may stay the same while the SDK version used to build a later release changes.
When troubleshooting, it helps to separate three questions:
- What version of SAMSON do I have? The public release label and internal version are different. For example, public version
2026 R1is based on internal SAMSON and SDK version11.0.0. - Which SDK version was used to build the Extension? This is the version SAMSON uses for its compatibility decision.
- Is a compatible Extension release available? If so, SAMSON can update Extensions automatically at startup when an Internet connection is available.
What happens when versions change?
If you are running SAMSON 1.7.8 and an Extension built with SDK 1.5.2, SAMSON can load it. If a newer Extension release built with SDK 1.6.4 becomes available, that release also meets the documented compatibility rule, so SAMSON can update it at startup when connected to the Internet.
A different situation arises when SAMSON moves to a new major version. If the Extension developer publishes a new build for SDK 2.0.0 but you remain on SAMSON 1.7.8, the major versions do not match. SAMSON will not update to that incompatible build; it keeps the compatible Extension version it already has.
This is why updating SAMSON regularly can matter: a newer SAMSON version may allow newer compatible Extension builds, as well as providing SAMSON updates. If an Extension is unavailable or does not update, check the SDK version and SAMSON version first, then confirm whether an Internet connection is available for automatic updates. The Extension’s own version label is useful context, but it does not answer the compatibility question by itself.
For the full versioning rules and examples, see the SAMSON versioning documentation.
Note: SAMSON and all SAMSON Extensions are free for non-commercial use. Get SAMSON.