A ThinkingLoop abort is the loop guard asking for a same-model resample
(it injects a thinking-loop-redirect notice that only makes sense on the
model that looped), not a provider failure. #handleRetryableError routed
it through the generic retryable-error branch, so on attempt 1 it called
noteRetryFallbackCooldown + #tryRetryModelFallback and could switch to
another family from retry.fallbackChains while parking the original
selector on a 5-minute cooldown. A healthy Grok 4.6 planning turn got
replaced by whatever the chain listed next.
Carve ThinkingLoop out of the model-fallback branch and out of the
Fireworks Fast->base degrade so the loop guard always re-samples the same
model; the retry budget still bounds a genuinely stuck stream.
Fixes#8760
roboomp
412d0e3b42