fix(tools): strip default from $ref nodes in tool schemas - #44676
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Fireworks-hosted Kimi rejects tool requests when nullable MCP/Pydantic
schemas collapse to {"$ref": "...", "default": null}. Strip that sibling
during global schema sanitization so gateway and CLI calls succeed again.
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🔎 Lint report:
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Applied from upstream merge d810f2b (PR NousResearch#44676, bb/fix-schema-ref-default). Fixes HTTP 400 on strict draft-07 backends (Fireworks Kimi) when MCP tool schemas leave default alongside $ref after nullable-union collapse. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
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…-ref-default fix(tools): strip default from $ref nodes in tool schemas
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Summary
JSON Schema not supported: keyword(s) ['default'] not allowed at the same level as $refon every agent turn when using strict backends (reported on Fireworks-hosted Kimi K2 with MCP tools enabled).defaultfrom any node that carries$ref, and nullableanyOfcollapse no longer copiesdefaultonto$refbranches.Root cause
MCP/Pydantic tool schemas commonly express optional fields as
anyOf: [{$ref: ...}, {type: null}]withdefault: null. Hermes already collapses those unions for backend compatibility, but the collapse was leaving{"$ref": "#/$defs/Foo", "default": null}— which Fireworks (and other draft-07-strict validators) reject outright.Test plan
scripts/run_tests.sh tests/tools/test_schema_sanitizer.py(43 passed)$ref-based schemas; confirm gateway/CLI messages succeed after upgrade