diff --git a/src/resources/extensions/gsd/commands/handlers/workflow.ts b/src/resources/extensions/gsd/commands/handlers/workflow.ts
index 85f6276e2..a755bf9ab 100644
--- a/src/resources/extensions/gsd/commands/handlers/workflow.ts
+++ b/src/resources/extensions/gsd/commands/handlers/workflow.ts
@@ -38,6 +38,67 @@ const WORKFLOW_USAGE = [
   "  resume            — Resume paused custom workflow auto-mode",
 ].join("\n");
 
+function splitWorkflowRunArgs(input: string): string[] {
+  const tokens: string[] = [];
+  let current = "";
+  let quote: '"' | "'" | null = null;
+  let escapeNext = false;
+
+  for (const ch of input) {
+    if (escapeNext) {
+      current += ch;
+      escapeNext = false;
+      continue;
+    }
+
+    if (ch === "\\") {
+      escapeNext = true;
+      continue;
+    }
+
+    if (quote) {
+      if (ch === quote) {
+        quote = null;
+      } else {
+        current += ch;
+      }
+      continue;
+    }
+
+    if (ch === '"' || ch === "'") {
+      quote = ch;
+      continue;
+    }
+
+    if (/\s/.test(ch)) {
+      if (current) {
+        tokens.push(current);
+        current = "";
+      }
+      continue;
+    }
+
+    current += ch;
+  }
+
+  if (escapeNext) current += "\\";
+  if (current) tokens.push(current);
+  return tokens;
+}
+
+export function parseWorkflowRunArgs(args: string): { defName: string; overrides: Record<string, string> } {
+  const parts = splitWorkflowRunArgs(args);
+  const defName = parts[0] ?? "";
+  const overrides: Record<string, string> = {};
+  for (let i = 1; i < parts.length; i++) {
+    const eqIdx = parts[i].indexOf("=");
+    if (eqIdx > 0) {
+      overrides[parts[i].slice(0, eqIdx)] = parts[i].slice(eqIdx + 1);
+    }
+  }
+  return { defName, overrides };
+}
+
 async function handleCustomWorkflow(
   sub: string,
   ctx: ExtensionCommandContext,
@@ -62,15 +123,7 @@ async function handleCustomWorkflow(
       ctx.ui.notify("Usage: /gsd workflow run <name> [param=value ...]", "warning");
       return true;
     }
-    const parts = args.split(/\s+/);
-    const defName = parts[0];
-    const overrides: Record<string, string> = {};
-    for (let i = 1; i < parts.length; i++) {
-      const eqIdx = parts[i].indexOf("=");
-      if (eqIdx > 0) {
-        overrides[parts[i].slice(0, eqIdx)] = parts[i].slice(eqIdx + 1);
-      }
-    }
+    const { defName, overrides } = parseWorkflowRunArgs(args);
     try {
       const base = projectRoot();
       const runDir = createRun(base, defName, Object.keys(overrides).length > 0 ? overrides : undefined);
diff --git a/src/resources/extensions/gsd/tests/commands-workflow-custom.test.ts b/src/resources/extensions/gsd/tests/commands-workflow-custom.test.ts
index 537bcab4d..21b2f07fa 100644
--- a/src/resources/extensions/gsd/tests/commands-workflow-custom.test.ts
+++ b/src/resources/extensions/gsd/tests/commands-workflow-custom.test.ts
@@ -217,6 +217,20 @@ describe("workflow command handler", () => {
     );
   });
 
+  it("preserves quoted workflow run overrides (#4130)", async () => {
+    const { parseWorkflowRunArgs } = await import("../commands/handlers/workflow.ts");
+    assert.deepStrictEqual(
+      parseWorkflowRunArgs('demo-workflow target="multi word target" region=\'us east\''),
+      {
+        defName: "demo-workflow",
+        overrides: {
+          target: "multi word target",
+          region: "us east",
+        },
+      },
+    );
+  });
+
   it("'/gsd workflow run nonexistent' shows error for missing definition", async () => {
     const { handled, notifications } = await callHandler("workflow run nonexistent-def-12345");
     assert.ok(handled, "should be handled");