Summary

Removes the deprecated Simulator, ABMSimulator, and DEVSimulator classes and the entire mesa.experimental.devs package, completing the deprecation cycle started in Mesa 3.5.0.

Motive

The simulator classes were deprecated in 3.5.0 (#3277) when their functionality was replaced by public methods directly on Model: run_for(), run_until(), schedule_event(), and schedule_recurring(). Per our deprecation policy, deprecated features are removed in the next major release. This PR prepares for Mesa 4.0 by removing these legacy classes.

Implementation

• Deleted mesa/experimental/devs/simulator.py and mesa/experimental/devs/__init__.py
• Removed devs from mesa.experimental.__init__ exports
• Removed the _simulator attribute and its TYPE_CHECKING import from Model
• Removed Simulator reference from the Model docstring
• Removed SimulatorController component and simulator parameter from SolaraViz
• Simplified SolaraViz to always use ModelController instead of branching on simulator presence
• Removed "simulator" from allowed parameter names in _check_model_params
• Deleted tests/experimental/test_devs.py (463 lines of simulator-specific tests)
• Removed simulator-related test from tests/test_model.py
• Removed Devs section from docs/apis/experimental.md

Note that the core event system (Event, EventList, EventGenerator, Schedule, Priority) is not affected — it was already stabilized into mesa.time in 3.5.0 and remains fully functional.

Usage Examples

Users who were still on the deprecated API should migrate as documented in the migration guide:

# Old - ABMSimulator
from mesa.experimental.devs.simulator import ABMSimulator
simulator = ABMSimulator()
simulator.setup(model)
simulator.run_for(100)

# New
model.run_for(100)

# Old - DEVSimulator
from mesa.experimental.devs.simulator import DEVSimulator
simulator = DEVSimulator()
simulator.setup(model)
simulator.schedule_event_absolute(callback, time=10.5)
simulator.run_for(50)

# New
model.schedule_event(callback, at=10.5)
model.run_for(50)

Additional Notes

• This is a breaking change intended for Mesa 4.0.
• The migration guide and deprecation warnings have been in place since 3.5.0 (one minor release cycle).
• Ref: Deprecate Simulator classes, add migration guide entry #3277, Proposal: Unified Time and Event Scheduling API #2921