Close the parity gaps deferred from the original Bedrock pass.
Schema additions on the Converse target:
- BedrockImageBlock for { image: { format, source: { bytes } } }.
Supported formats per Converse docs: png, jpeg, gif, webp.
- BedrockDocumentBlock for { document: { format, name, source: { bytes } } }.
Supported formats: pdf, csv, doc, docx, xls, xlsx, html, txt, md.
- BedrockCachePointBlock for the positional { cachePoint: { type } }
marker. Currently emits the only Bedrock cache type, 'default'. A
TODO marks where to map ttlSeconds → ttl ('5m' | '1h') once we have
a recorded cassette to validate the wire shape.
Lowering:
- TextPart and SystemPart cache hints emit a positional cachePoint
marker right after their text block. Both 'ephemeral' and
'persistent' CacheHint types map onto Bedrock's 'default' since
Bedrock does not distinguish — this matches the convention the
Anthropic adapter uses (cache?.type === 'ephemeral' check).
- MediaPart routes by mediaType: 'image/*' → image block, everything
else → document block. MIME type → format mapping is via
IMAGE_FORMATS / DOCUMENT_FORMATS records typed with 'as const
satisfies' so the keys stay narrow at compile time.
- A small textWithCache helper collapses the 'push text, push
cachePoint if cache is set' pattern that would otherwise repeat at
three callsites (system, user-text, assistant-text).
- Bytes are encoded via ProviderShared.mediaBytes — the shared
helper Kit landed in c3346f7dc.
Bug fix: lowerSystem was dead code in the previous draft. The
prepare() function still inlined the pre-cache .map(...) that
discarded system cache hints. prepare() now calls lowerSystem so
the cachePoint markers actually flow through.
Tests (7 new fixtures, all green):
- Cache hint on system / user-text / assistant-text emits cachePoint
after text in each context.
- No cache hint → no cachePoint emitted (regression guard).
- Image lowering covers png / jpeg / jpg-alias / webp.
- Uint8Array image bytes are base64-encoded ([1,2,3,4,5] → AQIDBAU=).
- Document lowering with filename round-trip and missing-filename
fallback to 'document.<format>'.
- Unsupported image MIME (image/svg+xml) is rejected with a clear
error message.
- Unsupported document MIME (application/x-tar) is rejected with a
clear error message.
Recorded cassettes for cache hints, images, and documents are still
TODO — the wire shapes are exercised deterministically here and will
be validated against a live model in a follow-up cassette pass.
Verified: bun typecheck clean, 113 pass / 0 fail / 0 skip (was 106;
+7 from the new fixture tests).
Kit Langton
096c305a55