fix(rlm): fall back to no sub-agents when the interpreter rejects the facade shim with SyntaxError

[isaacbmiller]

📝 Changes Description

Since #10478, RLM runs the sandbox dspy facade shim (_facade_shim.py) through every interpreter before the first iteration. Restricted interpreters, such as one built on RestrictedPython, reject the shim's _dspy_* names at compile time and raise SyntaxError. _setup_facade only caught CodeExecutionError around FacadeInvocation.install, so every RLM call on these interpreters crashed. 3.4.0 works with them.

This PR:

• catches SyntaxError in _setup_facade and handles it like CodeExecutionError: it removes the facade tools, logs the existing RLM sub-agents are unavailable on <Interpreter> warning, and runs the call without sub-agents.
• adds a regression test (TestRLMSubAgents::test_interpreter_that_rejects_the_shim_as_syntax_error_runs_without_sub_agents). It fails on main with SyntaxError: "_dspy_sys" is an invalid variable name… and passes with the fix.

A SyntaxError from the model's own code still goes through the REPL loop's existing handling.

Verification:

• pytest tests/predict/test_rlm.py tests/primitives/ tests/flex/: 390 passed, 161 skipped.
• A RestrictedPython-backed CodeInterpreter crashed before the fix. After it, RLM completes both with DummyLM and with a live gpt-4o.

✅ Contributor Checklist

• Pre-Commit checks are passing (locally and remotely)
• Title of your PR / MR corresponds to the required format
• Commit message follows required format {label}(dspy): {message}

⚠️ Warnings

Targeted for 3.4.1. Sibling 3.4.1 fixes R3 (Flex in-process interpreters) and R7 (facade opt-out) also touch rlm.py and the facade. This diff only changes the except clause in _setup_facade.

[greptile-apps]

Confidence Score: 5/5

[Medium impact] The changes are safe to merge, with no outstanding issues requiring attention.

Summary

RLM now continues without sub-agents when an interpreter rejects the facade shim with SyntaxError.

• RLM calls continue when an interpreter rejects the facade shim.

_{Reviews (2) · Last reviewed commit: "fix(rlm): fall back to no sub-agents whe..." · Reviewed by Greptile}