ssms.rl presets are not resolvable through model_config / hssm_support — HSSM's RV path warns and degrades

[AlexanderFengler]

Summary

ssm-simulators 0.13 ships the choice-only RL presets in ssms/rl/preset.py (2AB_RW_InvTempSoftmax, 3AB_RW_InvTempSoftmax, …), resolvable via ssms.rl.resolve_model. But they are not registered in ssms.config.model_config, which is the only registry ssms.hssm_support consults. Downstream (HSSM) the config layer bridges fine, but the RV/simulator path degrades.

Companion to lnccbrown/HSSM#1052 (this issue covers the ssm-simulators half).

State (0.13.1)

preset	ssms.rl.resolve_model	in model_config
2AB_RW_InvTempSoftmax	✅	❌
2AB_RW_DualAlpha_InvTempSoftmax	❌ KeyError	❌
3AB_RW_InvTempSoftmax	✅	❌
4AB_RW_InvTempSoftmax	❌ KeyError	❌

The decision-process kernels ARE registered, under different names: inv_temp_softmax_2/3/4.

Behavior today

ssms.hssm_support.get_simulator_fun_internal (hssm_support.py:333-346) handles any name missing from model_config by warning and building a fallback simulator anyway:

You supplied a model '2AB_RW_InvTempSoftmax', which is currently not supported in
the ssm_simulators package. An error will be thrown when sampling from the random
variable or when using any posterior or prior predictive sampling methods.

…with choices silently defaulting to [0, 1, 2] (wrong for a 2AB model). The promised error then surfaces much later and far away (in HSSM: at posterior-predictive time, or as an opaque numba serialization crash — see HSSM#1052 for that half).

Proposed fixes

1. Registry bridging (the feature): make the ssms.rl presets reachable through the hssm_support path — either register them in model_config, or have get_simulator_fun_internal consult ssms.rl.resolve_model before falling back.
2. Fail loudly (the robustness): when a name is in neither registry, get_simulator_fun_internal should raise at build time instead of warn-and-degrade — the current fallback also fabricates a wrong default choices=[0,1,2].

Impact

Four HSSM smoke tests (tests/rl/test_choice_only_rl.py::TestChoiceOnlyRealSSMSSmoke) are skip-guarded on model_name in model_config pending this wiring. Discovered while bumping HSSM's pin to ssm-simulators 0.13.1 (HSSM#967).

🤖 Generated with Claude Code

[linear-code]

HSSM-673