v2.19: ensure every tool def has a 'parameters' field (Lena follow-up). Cross-session lookup now prefers variants WITH parameters; final pass adds empty `{type:object, properties:{}}` for tools that genuinely have no args (e.g., 'finish') where no sibling captured a real schema. ~1.99M tool defs upgraded. Regression suite now checks this.
v2.17: normalize '[]' output.messages → null on 45 spans. v2.14's empty-text-part drop left some output.messages as the JSON string '[]' when all messages were dropped; v1 + the rest of v2 use null for 'no output' (consumers' `out[0]` access crashes on []). Regression suite now checks for this so it can't recur.
v2.15: cross-session tool-definitions recovery. Pre-pass builds (benchmark, harness, tool_name) → real-definition lookup over the corpus; sessions that had stub-only or no defs now inherit real schemas from sibling sessions in the same (bench, harness) combination. 100% of called-tool names in previously-stub sessions matched a real def in source. 1,245 stub sessions upgraded to real definitions (with parameter schemas). Lena 0 errors, regression bit-for-bit clean, smolagents untouched (synthesis path doesn't trigger for it).
v2.14: tool-message shape normalization + tool-defs propagation/synthesis + empty-part drop. (1) Convert {role:tool, parts:[{type:text}]} → tool_call_response: real id from preceding assistant.tool_call when available, positional fallback `call_<msg>_<part>` otherwise (drops to 0 orphan ids / 2.47M tcr parts). (2) Propagate gen_ai.tool.definitions across sibling chat spans (+94k); synthesize from real called-tool names for sessions where defs never existed. (3) Drop empty-content text parts. Lena 0/241k, tracelab 1,378 (all Issue #13 stragglers, same as v2.13), Yoav 0 model mismatches. Bit-for-bit regression-clean.
v2.13: backfill gen_ai.provider.name from canonical model (+58k spans) per OTel semconv requirement. Keeps v2.12 typing + canonical models + recomputed top-level. Verified bit-for-bit against v3-struct-recovered (span/row/id/token sums identical, only delta is the intended provider backfill).
