Unsupported image rejections from text-only compatible providers should not
poison the session, and low-trust multimodal usage spikes should not make
context indicators report a full window.
Constraint: Third-party Anthropic-compatible providers may report encoded media bytes as usage tokens.
Rejected: Trust all provider usage uniformly | third-party media responses can pin context to 100% incorrectly.
Confidence: high
Scope-risk: moderate
Directive: Do not remove the media-aware fallback without checking text-only provider recovery and desktop context indicators.
Tested: bun run check:server
Tested: focused media/context regression suite
