Simplify-pass follow-ups on the salvage stack (all guard tests re-run,
mutation-checked):
1. conversation_loop.py: moved `_preflight_compression_blocked = False`
from 9 per-site copies into the restart_with_rebuilt_messages handler
(its single consumer). Besides removing the 9 duplicated blocks, this
fixes a 10th pre-existing retry-loop site (content-filter stall
failover, #32421) that set the flag and broke WITHOUT clearing the
preflight block — a content-filter failover previously restarted with
preflight compression still blocked against the fallback's smaller
window, the same #84733 bug class. The outer-loop empty-response site
keeps its own clear (it never passes through the handler). New AST
guard test_restart_handler_clears_preflight_block pins the hoisted
clear (mutation-checked).
2. agent_runtime_helpers.py: extracted _raw_cache_ttl_from_config() —
prompt_caching_disabled_from_config and configured_cache_ttl were
verbatim copies of the same config read. Added VALID_CACHE_TTLS.
3. prompt_caching.py: added is_qwen_model() next to
ALIBABA_FAMILY_PROVIDERS; effective_cache_ttl and
anthropic_prompt_cache_policy now share both the family set and the
qwen predicate — neither can desync.
4. Guard-test hardening: assert every _try_activate_fallback reference
is a direct `if agent._try_activate_fallback(...):` site, so a future
`activated = ...` form can't silently escape the restart-discipline
guard.
Follow-ups on the salvaged #84782 (webtecnica):
1. conversation_loop.py: the empty-response fallback site sits directly
in the OUTER iteration loop, not the retry loop. The salvaged commit's
`break` there exited the conversation loop and ended the turn without
ever calling the just-activated fallback (caught by CI:
test_empty_response_triggers_fallback_provider). Restored `continue`
(which already re-runs the pre-API preflight at the top of the next
outer iteration) while keeping the `_preflight_compression_blocked`
reset. The other 9 sites are inside the retry loop, where `break` to
the restart_with_rebuilt_messages handler is correct.
2. test_prompt_cache_ttl_propagation.py: made the AST guard loop-aware —
retry-loop sites must break, outer-loop sites must continue (the old
assertion pinned the bug in (1)). Mutation-checked both directions.
3. test_failover_identity.py: added `model` to the SimpleNamespace agent
fixture — _redecorate_prompt_cache_for_provider now reads agent.model
for the per-destination TTL clamp (2 CI failures).
4. prompt_caching.py / agent_runtime_helpers.py: single source of truth
for the alibaba-family provider set — ALIBABA_FAMILY_PROVIDERS lives
in prompt_caching and anthropic_prompt_cache_policy imports it, so the
cache-policy opt-in and the TTL clamp can never desync.
5. auxiliary_client.py: threaded the configured tier into
_replan_synchronous_cache_sections via new configured_cache_ttl()
(no live agent on that path) — the aux half of #84733's report also
stopped regressing 1h to 5m. Guarded by
TestAuxFallbackReplanThreadsTtl (mutation-checked).
6. Dropped the redundant `or "5m"` at the two threaded call sites —
effective_cache_ttl already resolves None to "5m", and the `or`
masked the cache-disabled (None) semantics.
Teknium