Run detail · gridlock-v1
Haiku 4.5 made 16 changes across two phases — 6 ramp upgrades that barely moved the needle, then 7 bulldozes of bottleneck ramps that severed critical city connections — collapsing population from 28,643 to 12,278 (−57%); the health multiplier hit 0.0 and zeroed the entire composite score to 0.00.
What the agent did
Haiku opened with an overview and a global segment query establishing baseline: flow 65% (flow_mean 64.6), 5,329 m of congested road, 36 jammed junctions, population 28,643 — already lower than the other runs' baselines, with 109 abandoned buildings and happiness at 81. Every saturated segment was at density 1.0.
The diagnosis correctly identified the central interchange (around x ≈ −300, z ≈ −800) as the primary bottleneck, where northbound and southbound highway traffic merged through a spaghetti of 3-lane ramps feeding into 6-lane mainlines. Several zoomed map renders and a route trace confirmed the congestion was concentrated there and in the southern residential district (z ≈ −1,820 to −1,950). Attempts to validate elevated bypass roads at x = 50 and x = 300 both failed with OBJECT_COLLISION on dozens of buildings, so Haiku shifted to upgrading existing segments instead.
Haiku targeted the 3-lane HighwayRamp and HighwayRampElevated segments it had identified as the narrowest links: segments 2314, 3797, 4565, 6451, 13439, and 14620. All six were upgraded to the same road class (HighwayRamp / HighwayRampElevated), costing $32,592. The game accepted the changes but the upgrades did not actually increase lane count — the ramp prefabs are capped at 3 lanes regardless of the upgrade call.
After three 2,340-tick steps the picture was mixed: congested junctions oscillated 39 → 35 → 37, congested metres barely changed (5,187 → 5,202 → 5,267 — still below the 5,329 baseline), but population was climbing (28,643 → 28,838 → 29,114 → 29,484) and abandoned buildings were falling (109 → 87 → 71 → 50). The city appeared to be recovering on its own, but Haiku interpreted the persistent junction count as evidence the bottleneck was not fixed.
Haiku decided the 3-lane ramps it had not upgraded were the unresolved choke points and bulldozed five of them (segments 4334, 5763, 7863, 14877, 16454) in a single batch. The logic was that removing saturated segments would force traffic onto alternative routes and clear the junctions. Junctions immediately fell from 37 to 33, then after one 2,340-tick step fell further to 25, with congested metres dropping to 4,905 m. Haiku read this as validation.
The problem was that segment 7863 (a HighwayRampElevated connecting nodes 197 and 23239 in the southern residential district) had 4 buildings directly fronting it, and the other removed ramps were load-bearing connectors in the western interchange cluster. After a second step, happiness collapsed from 82 to 67 and then to 41 — a signal the instructions explicitly mark as a death spiral, not a settling transient.
Haiku recognised the happiness crash and immediately tried to rebuild the five removed segments. Three of the five rebuild attempts failed with OBJECT_COLLISION: buildings had either shifted or were newly counted as collisions now that the elevated ramps were gone. Only two of the smaller ground-level HighwayRamp stubs (segments 14877 and 16454 replacements) could be rebuilt, at a combined cost of $4,783.
After one more step, happiness was still 67 and population had fallen to 28,822. Haiku then tried to rebuild the critical southern ramp (the 7863 replacement) but buildings 26240 and 47742 were in the way. It bulldozed those two buildings and successfully rebuilt the ramp — but this was too little, too late: the network remained fractured in the western interchange cluster where segments 4334 and 5763 had been removed and could not be replaced.
The next 2,340-tick step produced the decisive collapse: happiness fell to 33, population crashed from 28,822 to 16,891, and abandoned buildings spiked from 20 to 1,238. The severed western ramps had cut off access to services across a large residential zone; once households started abandoning, the revenue and demand spiral accelerated faster than any single road change could reverse. Attempts to rebuild the two remaining severed ramps in the western interchange also hit OBJECT_COLLISION on buildings that had respawned or shifted.
Haiku stepped one final time, hoping for stabilisation: population fell further to 10,631 with 1,238 abandoned buildings and happiness at 33. Recognising the city was in terminal decline and that the remaining time (~9,900 ticks) was insufficient for recovery, Haiku submitted immediately.
After submission the harness settled the run over its standard window. Final readings: flow_mean 53.5 (baseline 64.6, flow_gain −11), congested metres 9,264 (baseline 5,329, +74%), congested junctions 20 (down from 36 — but only because the city had lost so many residents that fewer vehicles were on the road). Population settled at 12,278, down 57% from the 28,643 baseline.
The health multiplier formula requires population to be at least 95% of baseline for a full score and hits 0.0 at 75% or below. At 43% of baseline, the health factor was 0.0, which multiplied the entire composite score to zero regardless of what the traffic terms said. Composite: 0.00. This is the benchmark's central failure mode in its most extreme form — not a traffic failure but a city-destruction failure.