diff --git a/packages/game-simulation/src/multirun.ts b/packages/game-simulation/src/multirun.ts
index cfcc05c..524ceaa 100644
--- a/packages/game-simulation/src/multirun.ts
+++ b/packages/game-simulation/src/multirun.ts
@@ -1,4 +1,4 @@
-import { exec } from 'node:child_process';
+import { spawn } from 'node:child_process';
 import { writeFileSync } from 'node:fs';
 import { resolve as pathResolve, dirname } from 'node:path';
 import { fileURLToPath } from 'node:url';
@@ -74,20 +74,30 @@ interface WorkerResult {
 function spawnWorker(runId: number, seed: number): Promise<WorkerResult> {
   return new Promise((resolve, reject) => {
     const workerPath = new URL('./worker.ts', import.meta.url).pathname.replace(/^\/([A-Z]:)/, '$1');
-    const cmd = `npx tsx "${workerPath}" --strategy ${strategyName} --ticks ${totalTicks} --seed ${seed} --run-id ${runId}`;
-    exec(cmd, { maxBuffer: 200 * 1024 * 1024 }, (error, stdout, stderr) => {
-      if (stderr) process.stderr.write(stderr);
-      if (error) {
-        reject(new Error(`Run #${runId} (seed ${seed}) failed: ${error.message}`));
+    const tsxBin = pathResolve(__dirname, '..', 'node_modules', '.bin', 'tsx');
+    const child = spawn(tsxBin, [workerPath, '--strategy', strategyName, '--ticks', String(totalTicks), '--seed', String(seed), '--run-id', String(runId)], {
+      stdio: ['ignore', 'pipe', 'pipe'],
+    });
+
+    let stdout = '';
+    child.stdout.on('data', (chunk: Buffer) => { stdout += chunk; });
+    child.stderr.on('data', (chunk: Buffer) => { process.stderr.write(chunk); });
+
+    child.on('close', (code) => {
+      if (code !== 0) {
+        reject(new Error(`Run #${runId} (seed ${seed}) exited with code ${code}`));
         return;
       }
       try {
-        const result = JSON.parse(stdout) as WorkerResult;
-        resolve(result);
+        resolve(JSON.parse(stdout) as WorkerResult);
       } catch (e) {
         reject(new Error(`Run #${runId} (seed ${seed}) produced invalid JSON: ${(e as Error).message}`));
       }
     });
+
+    child.on('error', (err) => {
+      reject(new Error(`Run #${runId} (seed ${seed}) failed to spawn: ${err.message}`));
+    });
   });
 }
 
diff --git a/packages/game-simulation/src/runner.ts b/packages/game-simulation/src/runner.ts
index 881b3ab..471b5b9 100644
--- a/packages/game-simulation/src/runner.ts
+++ b/packages/game-simulation/src/runner.ts
@@ -14,6 +14,7 @@ export interface SimulationConfig {
   seed?: number;
   verbose?: boolean;
   silent?: boolean;
+  onProgress?: (tick: number, totalTicks: number, era: string) => void;
 }
 
 export interface EraTransition {
@@ -139,8 +140,11 @@ export function runSimulation(config: SimulationConfig): SimulationResult {
       allMetrics.push(collectMetrics(state));
     }
 
-    if (!config.silent && tick % progressInterval === 0) {
-      printProgress(tick, config.totalTicks, state, startTime);
+    if (tick % progressInterval === 0) {
+      if (!config.silent) {
+        printProgress(tick, config.totalTicks, state, startTime);
+      }
+      config.onProgress?.(tick, config.totalTicks, state.meta.currentEra);
     }
   }
 
diff --git a/packages/game-simulation/src/worker.ts b/packages/game-simulation/src/worker.ts
index 481627c..f4f9d22 100644
--- a/packages/game-simulation/src/worker.ts
+++ b/packages/game-simulation/src/worker.ts
@@ -23,7 +23,18 @@ const strategy = strategyName === 'random' ? new RandomStrategy()
 
 process.stderr.write(`[Run #${runId}] Starting (seed ${seed}, ${totalTicks} ticks, ${strategyName})...\n`);
 
-const result = runSimulation({ totalTicks, decisionInterval, strategy, seed, verbose: false, silent: true });
+const result = runSimulation({
+  totalTicks,
+  decisionInterval,
+  strategy,
+  seed,
+  verbose: false,
+  silent: true,
+  onProgress: (tick, total, era) => {
+    const pct = ((tick / total) * 100).toFixed(0);
+    process.stderr.write(`[Run #${runId}] ${pct}% (tick ${tick.toLocaleString()}/${total.toLocaleString()}) — ${era}\n`);
+  },
+});
 const report = generateJsonReport(result, { totalTicks, decisionInterval, strategy, seed });
 
 const output = {