Support immutable routes during trace simplification

[seveibar]

Summary

• add an optional otherHdRoutes input to TraceSimplificationSolver
• propagate immutable peer routes through via removal, same-net via merging, and path simplification
• include immutable routes in collision indexes without adding them to mutation queues or solver output
• resolve synthetic peer-route connectivity through rootConnectionName
• render immutable peers as subdued, dashed layer-colored traces and cover the result with an SVG snapshot

Why

A simplifier sometimes needs to avoid copper that is already routed but must not modify it. Previously the only way for a route to participate in simplification collision checks was to include it in the editable route list. Pipeline9 exposed this gap for preloaded traces, but this change is generic and has no Pipeline9 dependency.

This is the first independently mergeable prerequisite extracted from #1755.

Validation

• bun test tests/features/trace-simplification-immutable-routes.test.ts tests/bugs/simplification-trace-overlap-repro.test.ts tests/solvers/same-net-via-merger-direct-overlap-star.test.ts tests/pipeline7-trace-simplification-net-colors.test.ts
• bunx tsc --noEmit
• bun run build
• git diff --check
• SVG snapshot: trace-simplification-immutable-routes-immutable-routed-peer.snap.svg

The focused regression separately verifies path shortening, two-via layer-collapse removal, same-net via merging, immutability, output exclusion, and completed visualization.

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Project	Deployment	Actions	Updated (UTC)
capacity-node-autorouter	Ready	Preview, Comment	Jul 28, 2026 6:47pm

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[graphite-app]

This file contains 4 test(...) calls (at lines 164, 182, 287, and 329), but the rule states that a *.test.ts file may have AT MOST one test(...). After the first test, the remaining tests should be split into separate, numbered files. For example: trace-simplification-immutable-routes1.test.ts, trace-simplification-immutable-routes2.test.ts, trace-simplification-immutable-routes3.test.ts, and trace-simplification-immutable-routes4.test.ts.

Suggested change

	test("trace simplification avoids immutable routed traces without emitting or mutating them", () => {
	const immutableSnapshot = structuredClone(immutableRoute)
	const routesWithoutFixedCopper = solve()
	expect(routesWithoutFixedCopper).toHaveLength(1)
	expect(
	getMinimumRouteDistance(routesWithoutFixedCopper[0]!, immutableRoute),
	).toBe(0)
	const routesWithFixedCopper = solve([immutableRoute])
	expect(routesWithFixedCopper).toHaveLength(1)
	expect(routesWithFixedCopper[0]!.connectionName).toBe("editable")
	expect(
	getMinimumRouteDistance(routesWithFixedCopper[0]!, immutableRoute),
	).toBeGreaterThanOrEqual(0.25)
	expect(immutableRoute).toEqual(immutableSnapshot)
	})
	test("trace simplification visualizes immutable routed peers", () => {
	const solver = createTraceSimplifier([immutableRoute])
	solver.solve()
	expect(solver.failed).toBe(false)
	const simplifiedRoute = solver.simplifiedHdRoutes[0]!
	expect(editableRoute.route).toHaveLength(9)
	expect(simplifiedRoute.route).toHaveLength(5)
	const immutableGraphics = getRouteGraphics({
	route: immutableRoute,
	strokeColor: "#3f3f46",
	strokeWidth: 0.16,
	strokeDash: [0.06, 0.06],
	pointFill: "#d4d4d8",
	})
	const inputGraphics = mergeGraphics(
	getRouteGraphics({
	route: editableRoute,
	strokeColor: "#d97706",
	strokeWidth: 0.12,
	pointFill: "#ffedd5",
	}),
	immutableGraphics,
	)
	const outputGraphics = mergeGraphics(
	getRouteGraphics({
	route: editableRoute,
	strokeColor: "rgba(217, 119, 6, 0.28)",
	strokeWidth: 0.06,
	strokeDash: [0.05, 0.05],
	}),
	{
	lines: [
	{
	points: [
	{ x: -2, y: 0 },
	{ x: 2, y: 0 },
	],
	strokeColor: "#dc2626",
	strokeWidth: 0.045,
	strokeDash: [0.08, 0.08],
	},
	{
	points: [
	{ x: -0.11, y: -0.11 },
	{ x: 0.11, y: 0.11 },
	],
	strokeColor: "#dc2626",
	strokeWidth: 0.055,
	},
	{
	points: [
	{ x: -0.11, y: 0.11 },
	{ x: 0.11, y: -0.11 },
	],
	strokeColor: "#dc2626",
	strokeWidth: 0.055,
	},
	],
	},
	getRouteGraphics({
	route: simplifiedRoute,
	strokeColor: "#16803c",
	strokeWidth: 0.14,
	pointFill: "#dcfce7",
	}),
	immutableGraphics,
	)
	const renderPanel = (graphics: GraphicsObject) =>
	getSvgFromGraphicsObject(graphics, {
	backgroundColor: "white",
	svgWidth: 560,
	svgHeight: 420,
	hideInlineLabels: true,
	})
	expect(
	stackSvgsHorizontally(
	[
	addPanelHeader({
	svg: renderPanel(inputGraphics),
	title: "BEFORE • UNSIMPLIFIED EDITABLE ROUTE",
	details: [
	"9 orange points are eligible for simplification.",
	"Gray dashed copper is pre-routed and read-only.",
	],
	}),
	addPanelHeader({
	svg: renderPanel(outputGraphics),
	title: "AFTER • SIMPLIFIED AROUND FIXED COPPER",
	details: [
	"5 green points remain (4 removed); faint orange = input.",
	"Red direct shortcut was rejected; gray copper is unchanged.",
	],
	}),
	],
	{ gap: 12, normalizeSize: false },
	),
	).toMatchSvgSnapshot(import.meta.path, {
	svgName: "immutable-routed-peer",
	})
	})
	test("trace simplification avoids immutable routed traces without emitting or mutating them", () => {
	const immutableSnapshot = structuredClone(immutableRoute)
	const routesWithoutFixedCopper = solve()
	expect(routesWithoutFixedCopper).toHaveLength(1)
	expect(
	getMinimumRouteDistance(routesWithoutFixedCopper[0]!, immutableRoute),
	).toBe(0)
	const routesWithFixedCopper = solve([immutableRoute])
	expect(routesWithFixedCopper).toHaveLength(1)
	expect(routesWithFixedCopper[0]!.connectionName).toBe("editable")
	expect(
	getMinimumRouteDistance(routesWithFixedCopper[0]!, immutableRoute),
	).toBeGreaterThanOrEqual(0.25)
	expect(immutableRoute).toEqual(immutableSnapshot)
	})

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