diff --git a/lib/circuit_gas_meter.ts b/lib/circuit_gas_meter.ts
new file mode 100644
index 00000000..6fb3d122
--- /dev/null
+++ b/lib/circuit_gas_meter.ts
@@ -0,0 +1,4 @@
+export function trackScriptExecutionGas(opCount: number, gasLimit = 100000): boolean {
+  if (opCount > gasLimit) throw new Error('Gas limit exceeded');
+  return true;
+}
diff --git a/lib/gas_meter.ts b/lib/gas_meter.ts
new file mode 100644
index 00000000..4f6b25c7
--- /dev/null
+++ b/lib/gas_meter.ts
@@ -0,0 +1,4 @@
+export function calculateCircuitEvalGas(opCount: number, memoryBytes: number): number {
+  const baseGas = 100;
+  return baseGas + opCount * 2 + Math.floor(memoryBytes / 1024);
+}
diff --git a/lib/ledResistorEval.ts b/lib/ledResistorEval.ts
new file mode 100644
index 00000000..a79e9c4f
--- /dev/null
+++ b/lib/ledResistorEval.ts
@@ -0,0 +1,4 @@
+/**
+ * tscircuit - led-ballast-resistor
+ */
+export function calcLedResistor(vSupply: number, vForward: number, iAmps: number = 0.02): number { return Math.max(0, (vSupply - vForward) / iAmps); }
diff --git a/lib/macroCycleDetector.ts b/lib/macroCycleDetector.ts
new file mode 100644
index 00000000..5d382fc7
--- /dev/null
+++ b/lib/macroCycleDetector.ts
@@ -0,0 +1,31 @@
+/**
+ * tscircuit/eval - Macro Cycle Detector
+ */
+export function detectMacroCycles(graph: Record<string, string[]>): { hasCycle: boolean; cyclePath?: string[] } {
+  const visited = new Set<string>();
+  const recursionStack = new Set<string>();
+
+  function dfs(node: string, path: string[]): boolean {
+    visited.add(node);
+    recursionStack.add(node);
+
+    for (const neighbor of graph[node] || []) {
+      if (!visited.has(neighbor)) {
+        if (dfs(neighbor, [...path, neighbor])) return true;
+      } else if (recursionStack.has(neighbor)) {
+        return true;
+      }
+    }
+
+    recursionStack.delete(node);
+    return false;
+  }
+
+  for (const node of Object.keys(graph)) {
+    if (!visited.has(node)) {
+      if (dfs(node, [node])) return { hasCycle: true };
+    }
+  }
+
+  return { hasCycle: false };
+}
diff --git a/lib/rcFilterEval.ts b/lib/rcFilterEval.ts
new file mode 100644
index 00000000..a4da1112
--- /dev/null
+++ b/lib/rcFilterEval.ts
@@ -0,0 +1,4 @@
+/**
+ * tscircuit - rc-time-constant
+ */
+export function calcRcCutoff(r: number, c: number): number { return 1 / (2 * Math.PI * r * c); }
diff --git a/lib/regexExecutionGuard.ts b/lib/regexExecutionGuard.ts
new file mode 100644
index 00000000..a0c25d9c
--- /dev/null
+++ b/lib/regexExecutionGuard.ts
@@ -0,0 +1,11 @@
+/**
+ * tscircuit/eval - Safe Regex Execution Guard
+ */
+export function safeRegexTest(pattern: RegExp, input: string, timeoutMs: number = 50): boolean {
+  const start = Date.now();
+  const res = pattern.test(input);
+  if (Date.now() - start > timeoutMs) {
+    throw new Error('Regex execution exceeded execution time budget');
+  }
+  return res;
+}
diff --git a/lib/stack_guard.ts b/lib/stack_guard.ts
new file mode 100644
index 00000000..5cbab06a
--- /dev/null
+++ b/lib/stack_guard.ts
@@ -0,0 +1,5 @@
+export function checkCallStackDepth(currentDepth: number, maxDepth: number = 250): void {
+  if (currentDepth > maxDepth) {
+    throw new Error(`Maximum schematic expansion depth of ${maxDepth} exceeded`);
+  }
+}
diff --git a/lib/thermalEval.ts b/lib/thermalEval.ts
new file mode 100644
index 00000000..5fa88f16
--- /dev/null
+++ b/lib/thermalEval.ts
@@ -0,0 +1,4 @@
+/**
+ * tscircuit - thermal-dissipation-eval
+ */
+export function calcJunctionTemp(pWatts: number, rThetaJA: number, ambient: number = 25): number { return ambient + (pWatts * rThetaJA); }
diff --git a/lib/timeout_guard.ts b/lib/timeout_guard.ts
new file mode 100644
index 00000000..a5d16cd9
--- /dev/null
+++ b/lib/timeout_guard.ts
@@ -0,0 +1,7 @@
+export function enforceEvalTimeout<T>(promise: Promise<T>, timeoutMs: number = 5000): Promise<T> {
+  let timer: NodeJS.Timeout;
+  const timeoutPromise = new Promise<T>((_, reject) => {
+    timer = setTimeout(() => reject(new Error('Circuit eval timeout exceeded')), timeoutMs);
+  });
+  return Promise.race([promise, timeoutPromise]).finally(() => clearTimeout(timer));
+}
diff --git a/lib/voltageDividerEval.ts b/lib/voltageDividerEval.ts
new file mode 100644
index 00000000..f60ad6b6
--- /dev/null
+++ b/lib/voltageDividerEval.ts
@@ -0,0 +1,4 @@
+/**
+ * tscircuit - resistor-divider-calc
+ */
+export function calcDivider(vin: number, r1: number, r2: number): number { return vin * (r2 / (r1 + r2)); }
diff --git a/lib/wireGaugeEval.ts b/lib/wireGaugeEval.ts
new file mode 100644
index 00000000..1a3db60c
--- /dev/null
+++ b/lib/wireGaugeEval.ts
@@ -0,0 +1,4 @@
+/**
+ * tscircuit - wire-gauge-voltage-drop
+ */
+export function calcWireDrop(current: number, lengthM: number, ohmsPerM: number): number { return current * lengthM * ohmsPerM; }