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Coding & Dev · Claude Code

Rewrite a finance backend from .NET to Hono with Claude Code under a parity harness

We are migrating our [OLD STACK] backend to [NEW STACK] with exact behavior preservation.
Rules:
1. Same routes, status codes, error codes and pagination fields. No “improvements”.
2. Money fields stay decimal/string, never floating point.
3. For each route: record old response + DB delta + outbound calls; port; replay until equal.
4. If old and new disagree, assume new is wrong unless I approve a numbered discrepancy report.
Start by listing every HTTP operation and a recording plan for side effects (email, payments, analytics).
Source: @ali_ilhami on x.com ·
Steps
  1. Freeze routes, status codes, error codes and money types (never JS numbers for money).
  2. Build a recorder that captures responses, DB writes and outbound calls from the old system.
  3. Port in tiers from low-risk to high-risk; gate each route on replay, not on “files exist”.
  4. Cut over with a written rollback; expect agents to cheat toward green—block hand-edited expectations.

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