Add allowEmptySignature compat option for Anthropic-compatible providers#4971
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pandada8 wants to merge 1 commit into
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Add allowEmptySignature compat option for Anthropic-compatible providers#4971pandada8 wants to merge 1 commit into
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this should fix #4464 |
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Pull request overview
This PR adds an Anthropic-compatibility toggle to preserve thinking blocks even when thinkingSignature is empty, addressing prompt-caching/replay issues with Anthropic-compatible proxies that accept empty signatures.
Changes:
- Added
allowEmptySignaturetoAnthropicMessagesCompat(defaultfalse). - Wired the compat flag through Anthropic provider parameter building into message conversion.
- Added Vitest coverage for default behavior vs.
allowEmptySignature: truebehavior.
Reviewed changes
Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.
| File | Description |
|---|---|
| packages/ai/src/types.ts | Adds the allowEmptySignature compat option with documentation and default semantics. |
| packages/ai/src/providers/anthropic.ts | Passes the compat flag into message conversion and conditionally preserves empty-signature thinking blocks. |
| packages/ai/test/anthropic-allow-empty-thinking-signature.test.ts | Verifies default downgrade-to-text behavior and opt-in preservation behavior for empty signatures. |
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| blocks.push({ | ||
| type: "thinking", | ||
| thinking: sanitizeSurrogates(block.thinking), | ||
| signature: block.thinkingSignature ?? "", |
Some Anthropic-compatible providers return thinking blocks with empty thinkingSignature but still accept them on replay. Previously, empty signatures caused thinking blocks to be rewritten as plain text blocks, which breaks prompt caching and causes some providers to return 400. Add allowEmptySignature to AnthropicMessagesCompat (default: false). When true, empty signatures are passed through as type: "thinking" with signature: "" instead of being downgraded to text blocks.
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Some Anthropic-compatible providers return thinking blocks with empty thinkingSignature but still accept them on replay. Previously, empty signatures caused thinking blocks to be rewritten as plain text blocks, which breaks prompt caching and causes some providers to return 400.
Add allowEmptySignature to AnthropicMessagesCompat (default: false). When
true, empty signatures are passed through as type: "thinking" with
signature: "" instead of being downgraded to text blocks.