systematic-debugging

1# Execute
2 
3Bug, failure, or unexpected behavior:
4 
51. **Isolate** — read error, reproduce, inspect the diff, and drill upward through diagnostic layers:
6   L1 symptom → L2 logic → L3 system → L4 architecture → L5 cross-system
7   contract → L6 platform → L7 spec gap. Layers are observation altitudes,
8   not one causal chain; the causal shape at the stop altitude is classified
9   explicitly before any root claim. Stop only when causal proof accounts
10   for the recurrence generator or reaches a T-class boundary.
112. **Identify owner** — compare working behavior, trace the bad value, locate the
12   canonical owner, and treat duplicate owners as a finding.
133. **Decide before editing** — Before fixing, run Patch-Shape Triage and Ripple Signal Triage when shared logic,
14   contracts, fallbacks, adapters, producer/consumer seams, or source-of-truth
15   boundaries are involved. Surface Change Necessity for any new source-code
16   path or non-trivial source edit. Run Minimality Check for a new branch,
17   fallback, adapter, owner, or compatibility path, and Pre-Edit Complexity
18   Check for an overloaded owner or complexity growth. After Change Necessity
19   selects `code-change` and before the first repair edit, own the TDD Route for
20   the repair slice per `test-driven-development` (`off` default; `strict` on
21   behavior/bugfix/shared/contract/persistence/permission/migration risk).
224. **Prove** — test one hypothesis with the smallest reproduction or
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