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Bug → spec protocol. When a bug is found or a test fails, trace the cause, decide whether a new §V invariant would catch recurrence, append to §B. This is the one non-obvious thing SDD does that plan-then-execute doesn't.
Passed 16 of 19 test cases with the skill, and 3 of 19 without it.
and 17 more in the full report
14 fixed4 passed either way4 still failing0 broke
Tokens, turns and time describe resource use, not a dollar price.
One of 13 test cases the skill fixed. Same model, same prompt, with and without the skill.
We need to record a bug history entry in SPEC.md for an authentication token leak incident resolved on 2026-05-10, linking root cause 'tokens written to stdout' to invariant V12. What format should the row entry use?
| Checked | Without skill | With skill |
|---|---|---|
| The entry follows the pipe-delimited format starting with B<number>|2026-05-10|tokens written to stdout|V12. | Missed | Passed |
| The entry is added under the §B section of the specification. | Missed | Passed |
The instructions your model reads when the skill loads.
Plan-then-execute fixes the code & forgets. SDD fixes the code AND edits spec so recurrence is impossible. That edit is backprop.
/build verification./check flags VIOLATE with root cause found.Read failure output / bug report. Find exact file:line of wrong behavior. Name root cause in one caveman sentence.
Ask three questions:
Draft the spec change. Never skip §B; §V/§I/§T are case-by-case.
Template:
§B row: B<next>|<date>|<root cause>|V<N>
§V line: V<next>: <testable rule that would have caught it>
Example:
§B row: B3|2026-04-20|refund job ran twice on retry|V7
§V line: V7: ∀ refund → idempotency key check before charge reversal
test cases passed, vs 3 / 19 without
More skills from the same source and nearby in the registry, with their headline benchmark lift.