writeJSON's last-resort branch (json.Marshal failing, a programmer
error: unsupported type or cyclic data) previously fell back to
http.Error, which answers text/plain and was the one corner where the
API broke its own {"error": ...} contract. It now writes a
hand-written constant JSON literal: still strictly simpler than the
encoder that just failed (the reason writeError, which is built ON
writeJSON, cannot be used there: it would be circular), but contract
consistent. Tested by forcing the branch with a channel payload,
which json.Marshal cannot encode.
One panel's whole world in one call: effective config in, echoed
config + cascade result + undirected edge list out. Edges are
[from, to] pairs with from < to in deterministic node order;
Graph.Edges() walks the adjacency once, GraphEdges(config) rebuilds
the seeded world (~25us) so Result stays lean and /api/comparison
stays untouched. This closes the topology gap the design brief
flagged; the frontend's seeded d3-force layout consumes these pairs.
Go bits: [][2]int is a slice of fixed-size arrays; [2]int is a value
type, comparable, and JSON-marshals to [a, b], exactly the wire
shape the spec asks for.
tygo regen includes a fix: engine.Strategy now maps to the generated
Strategy type instead of decaying to 'any' in ScenarioRequest.
Verified live through the dev stack: 7/120 reached, 351 edges.
internal/api stays a translation layer: decode (with
DisallowUnknownFields so typos 400 instead of silently defaulting),
run the engine, encode; all validation stays in the engine. Routes use
Go 1.22 mux patterns ('POST /api/comparison'), so wrong methods get
405 from the stdlib for free. httptest runs handlers fully in memory;
the API test re-pins the 99/70/7 golden values end to end.
ComparisonResponse is added to tygo.yaml with a type mapping so the
generated web/src/types/api.ts reuses the engine's TS types.
cmd/spreadlab now serves on -addr (default localhost:8080); -table
keeps the CLI comparison as a sanity check.
