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>
An assistant message with an empty or whitespace-only text content block —
produced by context compression or certain tool-call flows — is rejected by
the Anthropic Messages API with HTTP 400 "text content blocks must contain
non-whitespace text". Because the blank block is stored in session history and
replayed verbatim every turn, the session is permanently wedged behind the same
400.
The Bedrock adapter already guards this via _safe_text() (#9486); the native
Anthropic path never got the same treatment. _sanitize_replay_block() rebuilt
text blocks with the raw stored text, and the _convert_assistant_message()
guard only caught a fully empty block list, not a list still containing a
whitespace-only text block.
Add a _safe_text() helper mirroring the Bedrock one and apply it at both points:
the ordered-blocks replay path and a final in-place walk of the converted
content list. Both are self-healing — sessions that stored blank blocks recover
on the next API call. Only text blocks are coerced; thinking/tool_use/image
blocks are untouched.
Fixes#69512
Teknium
Prathamesh Chaudhari