* fix: prevent Anthropic chat crash on no-argument tool calls
When the model streams a tool_use block with no arguments (e.g.
get_categories), the accumulated input arrives as an empty string.
The Anthropic chat parser passed that empty string straight through as
function_args, and Assistant::FunctionToolCaller then called
JSON.parse("") — which raises "unexpected end of input", surfaces as a
Provider::Anthropic::Error, and kills the whole assistant turn.
Fix at the source by normalizing empty/nil tool input to an empty JSON
object in the parser, plus a defensive guard in FunctionToolCaller so
any provider that emits blank arguments cannot crash a turn.
Fixes#2722
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
* test: assert nil-args result as Hash to match jsonb function_result
Addresses Codex P1 / CodeRabbit review: EchoFunction returns the parsed
params Hash and ToolCall::Function stores it in a jsonb column, so the
nil-arguments test must assert the Hash directly instead of JSON.parse.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
---------
Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
