diff --git a/CHANGELOG.md b/CHANGELOG.md
index fcde2b446..6b3ebba1a 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -20,6 +20,7 @@
 - TUI: keep the last streamed response instead of replacing it with "(no output)". (#747 — thanks @thewilloftheshadow)
 - Slack: accept slash commands with or without leading `/` for custom command configs. (#798 — thanks @thewilloftheshadow)
 - Onboarding/Configure: refuse to proceed with invalid configs; run `clawdbot doctor` first to avoid wiping custom fields. (#764 — thanks @mukhtharcm)
+- Onboarding: quote Windows browser URLs when launching via `cmd start` to preserve OAuth query params. (#794 — thanks @roshanasingh4)
 - Anthropic: merge consecutive user turns (preserve newest metadata) before validation to avoid “Incorrect role information” errors. (#804 — thanks @ThomsenDrake)
 - Discord/Slack: centralize reply-thread planning so auto-thread replies stay in the created thread without parent reply refs.
 - Telegram: respect account-scoped bindings when webhook mode is enabled. (#821 — thanks @gumadeiras)
diff --git a/src/agents/pi-embedded-helpers.test.ts b/src/agents/pi-embedded-helpers.test.ts
index dcb19ed83..b352bc319 100644
--- a/src/agents/pi-embedded-helpers.test.ts
+++ b/src/agents/pi-embedded-helpers.test.ts
@@ -10,8 +10,8 @@ import {
   isCloudCodeAssistFormatError,
   isCompactionFailureError,
   isContextOverflowError,
-  isMessagingToolDuplicate,
   isFailoverErrorMessage,
+  isMessagingToolDuplicate,
   normalizeTextForComparison,
   sanitizeGoogleTurnOrdering,
   sanitizeSessionMessagesImages,
diff --git a/src/commands/onboard-helpers.test.ts b/src/commands/onboard-helpers.test.ts
index 5d058f51d..334c6b51e 100644
--- a/src/commands/onboard-helpers.test.ts
+++ b/src/commands/onboard-helpers.test.ts
@@ -27,9 +27,13 @@ describe("openUrl", () => {
     expect(ok).toBe(true);
 
     expect(mocks.runCommandWithTimeout).toHaveBeenCalledTimes(1);
-    const argv = mocks.runCommandWithTimeout.mock.calls[0]?.[0];
-    expect(argv?.slice(0, 4)).toEqual(["cmd", "/c", "start", ""]);
+    const [argv, options] = mocks.runCommandWithTimeout.mock.calls[0] ?? [];
+    expect(argv?.slice(0, 4)).toEqual(["cmd", "/c", "start", '""']);
     expect(argv?.at(-1)).toBe(`"${url}"`);
+    expect(options).toMatchObject({
+      timeoutMs: 5_000,
+      windowsVerbatimArguments: true,
+    });
   });
 });
 
diff --git a/src/commands/onboard-helpers.ts b/src/commands/onboard-helpers.ts
index 37f85e1f5..bd04da0aa 100644
--- a/src/commands/onboard-helpers.ts
+++ b/src/commands/onboard-helpers.ts
@@ -232,9 +232,22 @@ function resolveSshTargetHint(): string {
 export async function openUrl(url: string): Promise<boolean> {
   const resolved = await resolveBrowserOpenCommand();
   if (!resolved.argv) return false;
-  const command = [...resolved.argv, resolved.quoteUrl ? `"${url}"` : url];
+  const quoteUrl = resolved.quoteUrl === true;
+  const command = [...resolved.argv];
+  if (quoteUrl) {
+    if (command.at(-1) === "") {
+      // Preserve the empty title token for `start` when using verbatim args.
+      command[command.length - 1] = '""';
+    }
+    command.push(`"${url}"`);
+  } else {
+    command.push(url);
+  }
   try {
-    await runCommandWithTimeout(command, { timeoutMs: 5_000 });
+    await runCommandWithTimeout(command, {
+      timeoutMs: 5_000,
+      windowsVerbatimArguments: quoteUrl,
+    });
     return true;
   } catch {
     // ignore; we still print the URL for manual open
diff --git a/src/process/exec.ts b/src/process/exec.ts
index 4a0d6f831..71b828bcd 100644
--- a/src/process/exec.ts
+++ b/src/process/exec.ts
@@ -48,6 +48,7 @@ export type CommandOptions = {
   cwd?: string;
   input?: string;
   env?: NodeJS.ProcessEnv;
+  windowsVerbatimArguments?: boolean;
 };
 
 export async function runCommandWithTimeout(
@@ -59,6 +60,7 @@ export async function runCommandWithTimeout(
       ? { timeoutMs: optionsOrTimeout }
       : optionsOrTimeout;
   const { timeoutMs, cwd, input, env } = options;
+  const { windowsVerbatimArguments } = options;
   const hasInput = input !== undefined;
 
   // Spawn with inherited stdin (TTY) so tools like `pi` stay interactive when needed.
@@ -67,6 +69,7 @@ export async function runCommandWithTimeout(
       stdio: [hasInput ? "pipe" : "inherit", "pipe", "pipe"],
       cwd,
       env: env ? { ...process.env, ...env } : process.env,
+      windowsVerbatimArguments,
     });
     let stdout = "";
     let stderr = "";