diff --git a/packages/cli/src/shared/orchestrate.ts b/packages/cli/src/shared/orchestrate.ts
index db3fdb218..6d9436978 100644
--- a/packages/cli/src/shared/orchestrate.ts
+++ b/packages/cli/src/shared/orchestrate.ts
@@ -666,6 +666,7 @@ async function postInstall(
         // Append skill env vars to .spawnrc so MCP servers can resolve ${VAR} at runtime
         const skillEnvPairs = (process.env.SPAWN_SKILL_ENV_PAIRS ?? "").split(",").filter(Boolean);
         if (skillEnvPairs.length > 0) {
+          const validKeyRe = /^[A-Z_][A-Z0-9_]*$/;
           const envLines = skillEnvPairs
             .map((pair) => {
               const eqIdx = pair.indexOf("=");
@@ -673,15 +674,30 @@ async function postInstall(
                 return "";
               }
               const key = pair.slice(0, eqIdx);
+              if (!validKeyRe.test(key)) {
+                logWarn(`Skipping invalid skill env var key: ${key}`);
+                return "";
+              }
               const val = pair.slice(eqIdx + 1);
-              return `export ${key}='${val.replace(/'/g, "'\\''")}'`;
+              const valB64 = Buffer.from(val).toString("base64");
+              if (!/^[A-Za-z0-9+/=]+$/.test(valB64)) {
+                logWarn(`Skipping skill env var with invalid base64: ${key}`);
+                return "";
+              }
+              return `export ${key}="$(echo '${valB64}' | base64 -d)"`;
             })
             .filter(Boolean)
             .join("\n");
           if (envLines) {
-            await asyncTryCatch(() =>
-              cloud.runner.runServer(`printf '\\n# [spawn:skills]\\n${envLines}\\n' >> ~/.spawnrc`),
-            );
+            const payload = `\n# [spawn:skills]\n${envLines}\n`;
+            const payloadB64 = Buffer.from(payload).toString("base64");
+            if (!/^[A-Za-z0-9+/=]+$/.test(payloadB64)) {
+              logWarn("Unexpected characters in skill env payload base64");
+            } else {
+              await asyncTryCatch(() =>
+                cloud.runner.runServer(`printf '%s' '${payloadB64}' | base64 -d >> ~/.spawnrc`),
+              );
+            }
           }
         }
       }