The single global epsilon coin flip caused 90% of actions to use greedy
argmax across ALL 3 branches simultaneously, collapsing to 1 composite
action. Only 6/45 factored actions were used (13.3% diversity).
Fix: Each branch (exposure, order, urgency) now flips its own epsilon
coin independently:
- P(all greedy) = (1-ε)³ ≈ 72.9% at ε=0.10
- P(at least one random) ≈ 27.1% vs previous 10%
- Expected unique actions per epoch: significantly higher
Applied to both select_action() and select_action_with_confidence().
The forward pass is skipped when all 3 branches happen to be random
(0.1% chance), preserving the optimization.
1331 tests pass (416 ml-dqn + 915 ml), 0 failures.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
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