---
title: "GPT-5.6 Terra plays Grow a city (seed 2) | Micropolis run | Evals by Jetty"
url: https://evaljetty.com/micropolis/runs/gpt56terra-grow-s2.html
description: "GPT-5.6 Terra as mayor in Micropolis, Grow a city: 3,660 people, city score 322. 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-s2

# 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: 3,660 people, city score 322.

[Decision log](https://evaljetty.com/micropolis/runs/gpt56terra-grow-s2/decisions.jsonl)[City stats (CSV)](https://evaljetty.com/micropolis/runs/gpt56terra-grow-s2/series.csv)[Save file (.cty)](https://evaljetty.com/micropolis/runs/gpt56terra-grow-s2/city.cty)[Final map (PNG)](https://evaljetty.com/micropolis/runs/gpt56terra-grow-s2/final_map.png)[Runtime config](https://evaljetty.com/micropolis/runs/gpt56terra-grow-s2/runtime_config.json)[Validation report](https://evaljetty.com/micropolis/runs/gpt56terra-grow-s2/validation_report.json)

GOAL MISSED seed 2

GPT-5.6 Terra

openai/gpt-5.6-terra

population 3,660 (goal 10,000), city score 322

Population (start → end)0 → 3,660
Peak population20,900City score (start → end)500 → 322
Funds at the end$0Crime / pollution / traffic38 / 42 / 2
Zones R / C / I69 / 27 / 17
Power plants (coal / nuclear)3 / 0Police / fire stations1 / 0
Turns (model / failed)80 (80 / 0)
Actions applied / rejected222 / 6
Mean turn latency9.6sModel cost$1.540Wall clock13.0 min
Jetty run ID476d94f4

## 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 | $14,103 | 727 | 0 | 0 |
| 2 | Jul 1900 | 340 | $12,871 | 727 | 35 | 60 |
| 3 | Oct 1900 | 960 | $10,914 | 727 | 9 | 47 |
| 4 | Jan 1901 | 2,400 | $3,681 | 441 | 9 | 47 |
| 5 | Apr 1901 | 3,420 | $2,629 | 441 | 19 | 36 |
| 6 | Jul 1901 | 4,440 | $2,629 | 441 | 41 | 36 |
| 7 | Oct 1901 | 5,420 | $2,629 | 441 | 41 | 36 |
| 8 | Jan 1902 | 4,920 | $3,357 | 261 | 50 | 36 |
| 9 | Apr 1902 | 4,120 | $357 | 261 | 57 | 44 |
| 10 | Jul 1902 | 5,800 | $48 | 261 | 57 | 41 |
| 11 | Oct 1902 | 7,760 | $48 | 261 | 55 | 41 |
| 12 | Jan 1903 | 10,400 | $369 | 402 | 66 | 47 |
| 13 | Apr 1903 | 13,420 | $369 | 402 | 66 | 52 |
| 14 | Jul 1903 | 16,400 | $68 | 402 | 78 | 52 |
| 15 | Oct 1903 | 19,260 | $68 | 402 | 115 | 66 |
| 16 | Jan 1904 | 19,460 | $1,580 | 205 | 115 | 59 |
| 17 | Apr 1904 | 17,240 | $1,580 | 205 | 142 | 59 |
| 18 | Jul 1904 | 15,020 | $1,580 | 205 | 133 | 59 |
| 19 | Oct 1904 | 14,000 | $1,580 | 205 | 133 | 64 |
| 20 | Jan 1905 | 12,760 | $2,588 | 150 | 118 | 57 |
| 21 | Apr 1905 | 11,320 | $1,058 | 150 | 103 | 57 |
| 22 | Jul 1905 | 11,900 | $1,058 | 150 | 103 | 54 |
| 23 | Oct 1905 | 12,420 | $1,058 | 150 | 87 | 49 |
| 24 | Jan 1906 | 14,040 | $1,488 | 372 | 93 | 49 |
| 25 | Apr 1906 | 14,760 | $1,083 | 372 | 93 | 53 |
| 26 | Jul 1906 | 15,160 | $1,083 | 372 | 98 | 60 |
| 27 | Oct 1906 | 14,240 | $1,083 | 372 | 101 | 58 |
| 28 | Jan 1907 | 12,560 | $2,147 | 281 | 101 | 58 |
| 29 | Apr 1907 | 11,160 | $2,147 | 281 | 101 | 50 |
| 30 | Jul 1907 | 10,280 | $2,147 | 281 | 82 | 48 |
| 31 | Oct 1907 | 9,120 | $2,147 | 281 | 82 | 48 |
| 32 | Jan 1908 | 8,360 | $3,043 | 228 | 74 | 45 |
| 33 | Apr 1908 | 7,600 | $38 | 228 | 65 | 48 |
| 34 | Jul 1908 | 6,640 | $38 | 228 | 65 | 52 |
| 35 | Oct 1908 | 5,580 | $38 | 228 | 62 | 52 |
| 36 | Jan 1909 | 5,100 | $263 | 252 | 50 | 48 |
| 37 | Apr 1909 | 4,700 | $263 | 252 | 50 | 45 |
| 38 | Jul 1909 | 4,260 | $263 | 252 | 46 | 45 |
| 39 | Oct 1909 | 4,400 | $263 | 252 | 46 | 53 |
| 40 | Jan 1910 | 4,120 | $851 | 270 | 46 | 52 |
| 41 | Apr 1910 | 3,880 | $851 | 270 | 40 | 52 |
| 42 | Jul 1910 | 3,260 | $851 | 270 | 37 | 52 |
| 43 | Oct 1910 | 2,420 | $851 | 270 | 37 | 52 |
| 44 | Jan 1911 | 1,940 | $703 | 137 | 35 | 46 |
| 45 | Apr 1911 | 1,600 | $703 | 137 | 31 | 46 |
| 46 | Jul 1911 | 2,280 | $685 | 137 | 31 | 47 |
| 47 | Oct 1911 | 3,720 | $675 | 137 | 36 | 53 |
| 48 | Jan 1912 | 2,520 | $1,067 | 127 | 37 | 53 |
| 49 | Apr 1912 | 2,500 | $1,067 | 127 | 37 | 52 |
| 50 | Jul 1912 | 2,240 | $1,067 | 127 | 36 | 47 |
| 51 | Oct 1912 | 2,880 | $1,067 | 127 | 34 | 47 |
| 52 | Jan 1913 | 5,300 | $1,358 | 304 | 34 | 47 |
| 53 | Apr 1913 | 7,340 | $1,358 | 304 | 45 | 33 |
| 54 | Jul 1913 | 8,740 | $478 | 304 | 63 | 40 |
| 55 | Oct 1913 | 9,980 | $478 | 304 | 63 | 40 |
| 56 | Jan 1914 | 13,680 | $1,259 | 334 | 76 | 43 |
| 57 | Apr 1914 | 15,980 | $1,139 | 334 | 87 | 49 |
| 58 | Jul 1914 | 17,800 | $1,139 | 334 | 87 | 49 |
| 59 | Oct 1914 | 18,260 | $1,032 | 334 | 112 | 53 |
| 60 | Jan 1915 | 19,540 | $833 | 347 | 100 | 66 |
| 61 | Apr 1915 | 20,900 | $833 | 347 | 100 | 64 |
| 62 | Jul 1915 | 19,580 | $833 | 347 | 111 | 64 |
| 63 | Oct 1915 | 18,600 | $833 | 347 | 112 | 59 |
| 64 | Jan 1916 | 16,580 | $2,261 | 255 | 112 | 52 |
| 65 | Apr 1916 | 15,180 | $2,114 | 255 | 102 | 52 |
| 66 | Jul 1916 | 14,020 | $2,114 | 255 | 89 | 51 |
| 67 | Oct 1916 | 13,040 | $2,114 | 255 | 89 | 47 |
| 68 | Jan 1917 | 11,960 | $2,555 | 260 | 80 | 43 |
| 69 | Apr 1917 | 10,320 | $2,555 | 260 | 70 | 43 |
| 70 | Jul 1917 | 9,820 | $2,555 | 260 | 70 | 39 |
| 71 | Oct 1917 | 9,000 | $2,555 | 260 | 64 | 47 |
| 72 | Jan 1918 | 8,220 | $3,563 | 239 | 53 | 47 |
| 73 | Apr 1918 | 7,620 | $549 | 239 | 53 | 43 |
| 74 | Jul 1918 | 7,240 | $549 | 239 | 51 | 42 |
| 75 | Oct 1918 | 6,260 | $549 | 239 | 54 | 42 |
| 76 | Jan 1919 | 5,680 | $197 | 309 | 54 | 43 |
| 77 | Apr 1919 | 5,000 | $197 | 309 | 46 | 36 |
| 78 | Jul 1919 | 4,400 | $197 | 309 | 42 | 38 |
| 79 | Oct 1919 | 4,020 | $197 | 309 | 42 | 38 |
| 80 | Jan 1920 | 3,660 | $0 | 322 | 38 | 42 |

## Final map

[![Final city map: GPT-5.6 Terra on Grow a city](https://evaljetty.com/micropolis/media/gpt56terra-grow-s2-map.jpg)](https://evaljetty.com/micropolis/runs/gpt56terra-grow-s2/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 | 13.0 wall-minutes (model budget 45.0 min) |
| fail | judge | city-goal | population 3,660 (goal 10,000), city score 322 (score 3,660 / threshold 10,000) |
| pass | checklist | notes-explain-outcome | Notes section cites model thoughts from turns 1, 62 (peak), and 80 and explains the energy-supply / funding collapse that caused the decline |
| pass | checklist | player-matches-request | result.json confirms player=gpt56terra model=openai/gpt-5.6-terra task=grow seed=2 |
| pass | checklist | no-silent-outage | run.log shows 80 consecutive turns 0/80 failures no gaps |

## 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-s2.html · Evals by Jetty · Run your own evals: https://jetty.io/?utm_source=evaljetty&utm_medium=llms