---
title: "GPT-5.6 Terra plays Grow a city (seed 6) | Micropolis run | Evals by Jetty"
url: https://evaljetty.com/micropolis/runs/gpt56terra-grow-s6.html
description: "GPT-5.6 Terra as mayor in Micropolis, Grow a city: 2,920 people (bankrupt), city score 756. Timelapse, charts, every decision and the run's evaluation."
updated: 2026-09-28
publisher: Jetty (https://jetty.io)
---

02 — Run · Round 1 · Grow a city · gpt56terra-grow-s6

# GPT-5.6 Terra plays Grow a city

Empty generated map, $20,000, 20 years: reach 10,000 people without going bankrupt. Ended Jan 1920: 2,920 people (bankrupt), city score 756.

[Decision log](https://evaljetty.com/micropolis/runs/gpt56terra-grow-s6/decisions.jsonl)[City stats (CSV)](https://evaljetty.com/micropolis/runs/gpt56terra-grow-s6/series.csv)[Save file (.cty)](https://evaljetty.com/micropolis/runs/gpt56terra-grow-s6/city.cty)[Final map (PNG)](https://evaljetty.com/micropolis/runs/gpt56terra-grow-s6/final_map.png)[Runtime config](https://evaljetty.com/micropolis/runs/gpt56terra-grow-s6/runtime_config.json)[Validation report](https://evaljetty.com/micropolis/runs/gpt56terra-grow-s6/validation_report.json)

GOAL MISSED seed 6

GPT-5.6 Terra

openai/gpt-5.6-terra

population 2,920 (goal 10,000), city score 756; BANKRUPT: treasury under $500 for 8 turns in a row

Population (start → end)0 → 2,920
Peak population22,920City score (start → end)500 → 756
Funds at the end$242Crime / pollution / traffic44 / 41 / 0
Zones R / C / I51 / 15 / 51
Power plants (coal / nuclear)2 / 0Police / fire stations1 / 1
Turns (model / failed)80 (80 / 0)
Actions applied / rejected161 / 8
Mean turn latency9.2sModel cost$1.410Wall clock12.6 min
Jetty run ID4c859227

## The city over time

### Population

People, after every turn

### Funds

Treasury, after every turn

### City score

0–1000, re-evaluated each January

Table view

| Turn | Date | Population | Funds | City score | Crime | Pollution |
| --- | --- | --- | --- | --- | --- | --- |
| 0 | Jan 1900 | 0 | $20,000 | 500 | 0 | 0 |
| 1 | Apr 1900 | 0 | $15,259 | 712 | 0 | 0 |
| 2 | Jul 1900 | 660 | $10,628 | 712 | 17 | 52 |
| 3 | Oct 1900 | 1,680 | $4,949 | 712 | 13 | 48 |
| 4 | Jan 1901 | 2,720 | $1,059 | 475 | 13 | 48 |
| 5 | Apr 1901 | 5,160 | $396 | 475 | 27 | 46 |
| 6 | Jul 1901 | 6,900 | $90 | 475 | 42 | 41 |
| 7 | Oct 1901 | 9,600 | $90 | 475 | 42 | 41 |
| 8 | Jan 1902 | 12,520 | $808 | 684 | 60 | 49 |
| 9 | Apr 1902 | 15,440 | $127 | 684 | 81 | 63 |
| 10 | Jul 1902 | 18,500 | $127 | 684 | 81 | 61 |
| 11 | Oct 1902 | 20,260 | $127 | 684 | 111 | 61 |
| 12 | Jan 1903 | 21,360 | $996 | 675 | 123 | 65 |
| 13 | Apr 1903 | 22,920 | $996 | 675 | 123 | 70 |
| 14 | Jul 1903 | 21,840 | $996 | 675 | 134 | 70 |
| 15 | Oct 1903 | 19,620 | $996 | 675 | 133 | 71 |
| 16 | Jan 1904 | 17,540 | $2,130 | 437 | 133 | 65 |
| 17 | Apr 1904 | 15,420 | $2,130 | 437 | 123 | 56 |
| 18 | Jul 1904 | 13,960 | $2,130 | 437 | 105 | 56 |
| 19 | Oct 1904 | 12,480 | $2,130 | 437 | 105 | 58 |
| 20 | Jan 1905 | 11,160 | $2,987 | 310 | 91 | 59 |
| 21 | Apr 1905 | 9,920 | $2,987 | 310 | 84 | 59 |
| 22 | Jul 1905 | 9,240 | $2,987 | 310 | 84 | 49 |
| 23 | Oct 1905 | 8,500 | $2,987 | 310 | 78 | 53 |
| 24 | Jan 1906 | 7,260 | $3,189 | 296 | 66 | 53 |
| 25 | Apr 1906 | 6,360 | $187 | 296 | 66 | 48 |
| 26 | Jul 1906 | 5,340 | $177 | 296 | 57 | 45 |
| 27 | Oct 1906 | 4,700 | $166 | 296 | 47 | 39 |
| 28 | Jan 1907 | 4,480 | $502 | 283 | 47 | 39 |
| 29 | Apr 1907 | 4,420 | $502 | 283 | 43 | 41 |
| 30 | Jul 1907 | 3,600 | $482 | 283 | 41 | 43 |
| 31 | Oct 1907 | 3,340 | $482 | 283 | 41 | 43 |
| 32 | Jan 1908 | 3,360 | $683 | 318 | 37 | 38 |
| 33 | Apr 1908 | 3,040 | $683 | 318 | 38 | 42 |
| 34 | Jul 1908 | 2,740 | $683 | 318 | 38 | 44 |
| 35 | Oct 1908 | 2,180 | $683 | 318 | 35 | 44 |
| 36 | Jan 1909 | 2,160 | $809 | 329 | 29 | 46 |
| 37 | Apr 1909 | 3,780 | $809 | 329 | 29 | 41 |
| 38 | Jul 1909 | 5,140 | $509 | 329 | 28 | 41 |
| 39 | Oct 1909 | 6,200 | $509 | 329 | 37 | 43 |
| 40 | Jan 1910 | 6,560 | $997 | 650 | 37 | 47 |
| 41 | Apr 1910 | 5,780 | $697 | 650 | 49 | 47 |
| 42 | Jul 1910 | 4,820 | $697 | 650 | 54 | 47 |
| 43 | Oct 1910 | 4,360 | $697 | 650 | 54 | 45 |
| 44 | Jan 1911 | 3,720 | $1,145 | 433 | 49 | 52 |
| 45 | Apr 1911 | 3,360 | $1,145 | 433 | 43 | 52 |
| 46 | Jul 1911 | 3,260 | $1,145 | 433 | 43 | 44 |
| 47 | Oct 1911 | 2,480 | $1,145 | 433 | 44 | 42 |
| 48 | Jan 1912 | 2,440 | $1,453 | 357 | 34 | 42 |
| 49 | Apr 1912 | 1,920 | $1,453 | 357 | 34 | 43 |
| 50 | Jul 1912 | 1,860 | $1,453 | 357 | 27 | 39 |
| 51 | Oct 1912 | 1,880 | $1,453 | 357 | 25 | 39 |
| 52 | Jan 1913 | 1,260 | $1,621 | 292 | 25 | 39 |
| 53 | Apr 1913 | 2,220 | $1,621 | 292 | 23 | 48 |
| 54 | Jul 1913 | 3,100 | $28 | 292 | 26 | 48 |
| 55 | Oct 1913 | 2,600 | $28 | 292 | 26 | 48 |
| 56 | Jan 1914 | 1,780 | $280 | 425 | 34 | 48 |
| 57 | Apr 1914 | 1,320 | $280 | 425 | 34 | 45 |
| 58 | Jul 1914 | 1,300 | $280 | 425 | 34 | 45 |
| 59 | Oct 1914 | 1,020 | $198 | 425 | 29 | 42 |
| 60 | Jan 1915 | 700 | $282 | 288 | 27 | 42 |
| 61 | Apr 1915 | 1,340 | $282 | 288 | 27 | 40 |
| 62 | Jul 1915 | 1,340 | $282 | 288 | 25 | 40 |
| 63 | Oct 1915 | 1,140 | $282 | 288 | 28 | 43 |
| 64 | Jan 1916 | 1,540 | $322 | 644 | 28 | 40 |
| 65 | Apr 1916 | 1,920 | $307 | 644 | 26 | 40 |
| 66 | Jul 1916 | 1,840 | $307 | 644 | 27 | 41 |
| 67 | Oct 1916 | 1,480 | $307 | 644 | 27 | 39 |
| 68 | Jan 1917 | 1,420 | $475 | 531 | 27 | 39 |
| 69 | Apr 1917 | 1,280 | $475 | 531 | 23 | 39 |
| 70 | Jul 1917 | 1,260 | $475 | 531 | 23 | 40 |
| 71 | Oct 1917 | 1,180 | $475 | 531 | 23 | 39 |
| 72 | Jan 1918 | 1,140 | $615 | 433 | 23 | 39 |
| 73 | Apr 1918 | 920 | $615 | 433 | 23 | 40 |
| 74 | Jul 1918 | 1,280 | $615 | 433 | 23 | 46 |
| 75 | Oct 1918 | 1,320 | $615 | 433 | 23 | 46 |
| 76 | Jan 1919 | 1,700 | $615 | 716 | 23 | 43 |
| 77 | Apr 1919 | 4,020 | $91 | 716 | 25 | 42 |
| 78 | Jul 1919 | 4,180 | $91 | 716 | 40 | 47 |
| 79 | Oct 1919 | 3,320 | $91 | 716 | 40 | 47 |
| 80 | Jan 1920 | 2,920 | $242 | 756 | 44 | 41 |

## Final map

[![Final city map: GPT-5.6 Terra on Grow a city](https://evaljetty.com/micropolis/media/gpt56terra-grow-s6-map.jpg)](https://evaljetty.com/micropolis/runs/gpt56terra-grow-s6/final_map.png)

## Evaluation

failchecks **9/10** verdict: valid run (code checks and checklist) and task goal met (judge)

| Status | Kind | Check | Detail |
| --- | --- | --- | --- |
| pass | step | environment | Environment check (snapshot, engine, key) |
| pass | step | launch | Launch run-city as a detached process |
| pass | step | supervise | Supervise in the foreground until run-city exits |
| pass | step | render | Timelapse video rendered |
| pass | step | notes | Append Notes to summary.md |
| pass | code\_check | outputs-exist | all present |
| pass | code\_check | sim-reached-deadline | ended Jan 1920 after 80 turns; scenario verdict None |
| pass | code\_check | decisions-logged | 80 rows for 80 turns |
| pass | code\_check | llm-turns-valid | 0/80 model turns failed |
| pass | code\_check | video-decodes | duration 35.6s |
| pass | code\_check | limits-respected | 12.6 wall-minutes (model budget 45.0 min) |
| fail | judge | city-goal | population 2,920 (goal 10,000), city score 756; BANKRUPT: treasury under $500 for 8 turns in a row (score 0 / threshold 10,000) |
| pass | checklist | notes-explain-outcome | Notes section added citing model thoughts from turns 1, 13, and 80; explains over-investment and tax-hike spiral |
| pass | checklist | player-matches-request | result.json player.id=gpt56terra task=grow seed=6 match the requested values |
| pass | checklist | no-silent-outage | run.log shows all 80 turns logged with 0 LLM failures, no gaps or stretches of failed turns |

## Decision timeline

What the mayor thought and did each turn. Click a turn to jump the timelapse there.

---
Source: https://evaljetty.com/micropolis/runs/gpt56terra-grow-s6.html · Evals by Jetty · Run your own evals: https://jetty.io/?utm_source=evaljetty&utm_medium=llms