Follow-up to the cherry-picked #68633 commits, closing the final open
review point (egilewski): _relocated_replay_cache_control was applied
only inside `if replayed:`. When anthropic_content_blocks contained
only a blank cache-marked text block, `replayed` came out empty, the
function fell through to the main path's placeholder, and the cache
marker was lost; signed thinking + a blank marked text block likewise
returned with no cacheable carrier for the relocated marker.
The replay branch now appends the non-whitespace "(empty)" placeholder
when no cacheable (text/tool_use) block survives the blank filter and a
blank text block was dropped (or a marker needs a carrier) — so replay
stays schema-valid on Bedrock/strict endpoints and the breakpoint
survives on the placeholder.
Also reconciles the block-level tests from #69517 with the new
drop-then-fallback contract (blank blocks are dropped at the block
level; the message-level result is still always non-blank).
Refs #69512
Co-authored-by: ygd58 <buraysandro9@gmail.com>
teknium1
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