Todo 52.4 Benchmark Visible TTFT and Call Counts Plan

Status: in_progress

Goal

Prevent benchmark runs from passing with hidden extra model cost or an artificially early visible-response timestamp.

Scope

Record call-level and run-level visible TTFT only for a message_delta containing non-whitespace content.
Add expected ChatAgent call count and expected fallback count to each benchmark case expectation.
Compare both persisted ledger counts and timing-wrapper counts against the case expectation.
Keep the six current cases at zero fallback; web search expects two ChatAgent calls and all other cases expect one.

Files

Modify: src/agent_lab/application/benchmark.py
Modify: tests/test_benchmark_config.py
Modify: tests/test_benchmark_runner.py

Verification

uv run pytest tests/test_benchmark_runner.py tests/test_benchmark_config.py -q
uv run pytest
git diff --check