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+# CORPUS-0007
+## Rival Buys The Cart Space
+### Status: Training Corpus Seed
+### Layer: Layer_1--Worked_Examples
+### Purpose: Teach that a rival can change the cost, timing, or viability of a venture before the trader acts
+### Repository Path: docs/training/corpus/Layer_1--Worked_Examples/CORPUS-0007-rival-buys-the-cart-space.md
+
+---
+
+## 0. Scenario
+
+A trader in Ostia plans to send oil to Capua.
+
+The expected margin is modest but workable.
+
+Before he reserves transport, a rival trader buys the best available cart space.
+
+The oil price in Capua may still be favorable, but the conditions of the venture have changed.
+
+The opportunity did not disappear because the market changed first.
+
+It changed because another actor acted first.
+
+---
+
+## 1. Known Initial Facts
+
+| Fact | Value |
+|---|---:|
+| Origin | Ostia |
+| Destination | Capua |
+| Good | oil |
+| Purchase price in Ostia | 10 asses |
+| Expected sale price in Capua | 20 asses |
+| Expected cart share | 4 asses |
+| Other expected costs | 3 asses |
+
+Initial expected total cost:
+
+```text
+10 + 4 + 3 = 17 asses
+```
+
+Initial expected result:
+
+```text
+20 - 17 = 3 asses profit
+```
+
+The venture appears worthwhile.
+
+---
+
+## 2. Rival Action
+
+A rival trader reserves the best cart space before the trader acts.
+
+The remaining options are worse:
+
+| Transport Option | New Cost | Effect |
+|---|---:|---|
+| later cart | 4 asses | two-day delay |
+| inferior cart | 5 asses | higher breakage risk |
+| private hire | 8 asses | immediate but expensive |
+
+The same oil no longer has the same venture conditions.
+
+---
+
+## 3. Variant A — Later Cart
+
+The trader waits two days for the later cart.
+
+Storage cost increases by 2 asses.
+
+A rival may reach Capua first.
+
+```text
+purchase price:       10 asses
+cart share:            4 asses
+other costs:           3 asses
+added storage:         2 asses
+-------------------------------
+total cost:           19 asses
+sale value:           20 asses
+result:                1 as profit
+```
+
+The venture still profits, but margin has narrowed.
+
+---
+
+## 4. Variant B — Inferior Cart
+
+The trader uses the inferior cart.
+
+Transport cost rises and one small loss occurs during movement.
+
+```text
+purchase price:       10 asses
+inferior cart:         5 asses
+other costs:           3 asses
+loss adjustment:       2 asses
+-------------------------------
+total cost:           20 asses
+sale value:           20 asses
+result:                0 profit
+```
+
+The venture breaks even.
+
+---
+
+## 5. Variant C — Private Hire
+
+The trader hires private transport immediately.
+
+```text
+purchase price:       10 asses
+private hire:          8 asses
+other costs:           3 asses
+-------------------------------
+total cost:           21 asses
+sale value:           20 asses
+result:                1 as loss
+```
+
+The fastest option produces a loss unless speed creates other strategic value.
+
+---
+
+## 6. Correct Model Behavior
+
+The model should reason:
+
+- the opportunity was not static
+- rival action changed available transport
+- changed transport altered cost, delay, and risk
+- the same purchase and sale prices can produce different outcomes
+- acting later can narrow or erase margin
+- rivalry can create loss without direct conflict
+
+---
+
+## 7. Incorrect Model Behavior
+
+The model should not:
+
+- assume cart space remains available
+- treat transport cost as fixed after the first estimate
+- ignore rival timing
+- assume the trader can always choose the best option
+- treat the expected 3-ass profit as guaranteed
+- ignore delay caused by unavailable transport
+
+---
+
+## 8. Layer-0 Concepts Used
+
+This example uses:
+
+- `CORPUS-0001-trade-requires-two-locations`
+- `CORPUS-0004-cost-includes-more-than-purchase-price`
+- `CORPUS-0005-profit-is-sale-minus-total-cost`
+- `CORPUS-0006-delay-is-economic-cost`
+- `CORPUS-0012-every-venture-risks-loss`
+- `CORPUS-0018-rivalry-changes-conditions`
+- `CORPUS-0019-success-has-no-boundary-failure-has-a-hard-stop`
+
+---
+
+## 9. Success Condition
+
+If the model sees a profitable venture and asks whether rivals can change transport, timing, or margin before the trader acts, this file is functioning correctly.