fix: The createObjectIfPossible method is unreliable on some LLMs
#1386
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…method is unreliable on some LLMs When createObjectIfPossible receives a malformed MaybeReturn response from an LLM where the success field is present but contains partial/invalid data (e.g., missing required fields or null values for non-nullable fields), the deserialization fails with MissingKotlinParameterException. This test reproduces the issue to verify that the fix properly handles these edge cases by returning a failure Result instead of throwing an exception.
When createObjectIfPossible receives a malformed MaybeReturn response from an LLM where the success field is present but contains invalid data (e.g., missing required fields, null values for non-nullable fields), the system now treats this as a failure case rather than throwing a deserialization exception. The fix implements a custom Jackson deserializer (MaybeReturnDeserializer) that: - Catches MissingKotlinParameterException and other deserialization errors during success field parsing - Converts these errors into a failure MaybeReturn with a descriptive message - Returns a proper Result.failure instead of propagating the exception This makes the system more robust when dealing with LLMs that don't follow the "never return partial structures" instruction in the maybe prompt template.
igordayen
reviewed
Feb 6, 2026
| val node = parser.codec.readTree<com.fasterxml.jackson.databind.JsonNode>(parser) | ||
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| val failureNode = node.get("failure") | ||
| if (failureNode != null && !failureNode.isNull) { |
Contributor
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maybe consider more kotlin idiomati such as failureNode?.isNull
| else -> | ||
| "Invalid success object: ${e.message}" | ||
| } | ||
| MaybeReturn(success = null, failure = errorMessage) |
| } | ||
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| // Neither success nor failure provided | ||
| return MaybeReturn(success = null, failure = "Neither success nor failure field provided") |
Contributor
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unit test for this scenarion would be good to have
igordayen
reviewed
Feb 6, 2026
| * ``` | ||
| * when they don't have enough information to populate all required fields. | ||
| */ | ||
| internal class MaybeReturnDeserializer<T>( |
Contributor
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ChatClientLlmOperations is getting larger. candidate perhaps to consider extension functions file (lower camel case) and if access to private members is allowed from extension file
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Summary
Automated fix for #637
Changes
embabel-agent-api/src/main/kotlin/com/embabel/agent/spi/support/springai/ChatClientLlmOperations.ktembabel-agent-api/src/test/kotlin/com/embabel/agent/spi/support/ChatClientLlmOperationsTest.ktDescription
Fixed MaybeReturn deserialization issue by implementing a custom Jackson deserializer that catches exceptions when parsing the success field and treats them as failures instead of throwing exceptions. All 2417 tests pass.
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