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+# Use-Case Model AI Usage
+
+## Name of AI service/solution that was used
+
+**Claude Code** (Anthropic)
+
+- **URL:** https://claude.com/claude-code
+- **Type of service/subscription:** Claude subscription, model Claude Opus 4.7 (1M context).
+
+## Final result
+
+### Results in details / description
+
+The AI:
+
+- Proposed the actor taxonomy (Visitor, Trader, Market Simulator) from the project description and the existing Go code.
+- Derived a set of 7 use cases covering the full trading loop (register, login, deposit, buy, sell, view portfolio, watchlist).
+- Wrote each `UseCaseXXXX.md` file with:
+  - initiating actor, other actors, goals
+  - step-by-step dialog-form scenario
+  - **tested** SQL statements for every database-touching step, using the `project` schema
+  - alternate flows for the most common failure cases (insufficient funds, insufficient holding, duplicate user, invalid input)
+
+## Summary of AI involvement
+
+| | Session 1 — 2026-04-21 | Session 2 — 2026-08-06/07 |
+|---|---|---|
+| **What I brought** | The project description in `opis.md` and the existing Go backend | The use-case model as completed in session 1 |
+| **What the AI did** | Proposed the actor taxonomy and drafted seven use cases with tested SQL | Nothing — the model was not changed |
+| **What I decided** | To go solo, and therefore to document seven use cases rather than the three the rubric requires | To re-verify every scenario's SQL against a live database rather than trust the April run |
+
+This phase was finished in session 1. In session 2 the only work was
+verification: each scenario was executed against a live PostgreSQL 16 database,
+including the failure paths, and the results recorded on the
+`UseCaseXXXXImplementation` pages.
+
+## Entire AI usage log
+
+See [ERModelAIUsage](../P1-ConceptualModel/ERModelAIUsage.md) for the full transcript — the same 2026-04-21 session produced the use-case documentation. The defining student prompt was:
+
+> I'm going solo do everything that you need to do, and tell me after what do I need to do
+
+which led the AI to pick "solo → 3 minimum per rubric → document 7 for a margin" as a default.
+
+> **Student action required:** append any future refinements of the use-case list or scenarios here.
+
+
+### Session 2 — 2026-08-06 / 2026-08-07
+
+No changes were made to the use-case model in this session: the actor list, the
+seven use cases and the scenario SQL in `UseCase0001`–`UseCase0007` are as
+produced on 2026-04-21. The SQL in those scenarios was, however, re-verified by
+executing the corresponding prototype flows against a live PostgreSQL 16
+database, including the failure paths (insufficient funds, insufficient holding,
+duplicate registration, wrong password). The results are documented per use case
+on the `UseCaseXXXXImplementation` pages.