Summary

Normalize stringified tool call arguments before request serialization so resumed conversations can be sent back to providers without invalid tool-call payloads.

Context

Some providers can return assistant tool calls whose arguments are emitted as stringified JSON instead of structured objects. That becomes a problem when the conversation is resumed and replayed, because downstream request builders expect structured tool arguments and can otherwise send invalid payloads back upstream.

Changes

• parse stringified JSON tool arguments during ToolCallArguments deserialization
• add ToolCallArguments::normalize() to repair persisted Unparsed tool arguments and wrap unrecoverable values in a fallback object
• introduce NormalizeToolCallArguments and run it in the orchestrator before provider-specific request conversion
• export the new transformer from the domain transformer module
• add regression coverage for both synthetic stringified tool calls and the real kimi-k2p5-turbo-error-dump.json resume scenario

Key Implementation Details

The fix is split into two layers:

1. Deserialize-time repair converts valid stringified JSON into Parsed values immediately.
2. Pre-request normalization handles older persisted conversations that still contain Unparsed arguments. If repair fails, the raw content is preserved in a fallback object so request builders always receive structured JSON.

This keeps the fix provider-agnostic while ensuring the outbound request pipeline works for resumed conversations.

Use Cases

• resume a conversation dump created from a provider that emitted tool arguments as strings
• replay assistant patch/read tool calls without sending string payloads back upstream
• protect future providers that may return the same malformed or stringified tool-call shape

Testing

cargo test -p forge_domain --test test_kimi_dump_normalization --test test_stringified_tool_calls
cargo check -p forge_domain -p forge_app -p forge_repo -p forge_main