bi-05 step 02 — Break it, then measure it

Goal

Demonstrate why each property of the real binding layer is load-bearing.

Tasks

1. Break wrapper identity — create a new wrapper per access. Show two failures: expandos vanishing and === returning false. Say which is worse and why.
2. Remove world separation — show an "extension" expando becoming visible to "page" code. Write two sentences on what an attacker does with that.
3. Measure the crossing. 1e6 iterations: property access through your wrapper vs a plain JS property. Attribute the gap to the four costs (crossing, conversion, checks, side effects).
4. Measure conversion specifically. Compare a numeric attribute with a long string attribute. Strings should dominate — explain why.

Done when

• Both identity failures reproduced
• Isolation failure reproduced with an attack sentence
• Measurement table with the gap attributed to named costs