feat: forward ignoreDefaultArgs to chrome-launcher

[CalebBarnes]

why

When running Stagehand locally, chrome-launcher adds its own set of default flags (e.g. --disable-extensions). There's currently no way for consumers to selectively remove these flags — localBrowserLaunchOptions.chromeFlags can only add flags, not remove chrome-launcher's built-in defaults.

This is needed when users want to run Chrome with extensions enabled, or need to remove other chrome-launcher defaults for their use case.

what changed

• Added ignoreDefaultArgs option to LaunchLocalOptions in local.ts
• Forwarded localBrowserLaunchOptions.ignoreDefaultArgs from v3.ts through to launchLocalChrome()
• When true: drops all chrome-launcher defaults (only Stagehand's own flags and user-supplied chromeFlags are used)
• When string[]: selectively removes only the listed flags from chrome-launcher defaults, keeping the rest

This mirrors the behavior of Playwright's ignoreDefaultArgs option.

test plan

• Verified locally that setting ignoreDefaultArgs: ["--disable-extensions"] successfully removes the flag from the launched Chrome instance (confirmed via chrome://version/)
• Verified that other chrome-launcher defaults are preserved when using the array form
• Verified that ignoreDefaultArgs: true drops all chrome-launcher defaults

---

Summary by cubic

Adds ignoreDefaultArgs to local Chrome launch and forwards it to chrome-launcher so users can drop all or selected default flags while keeping Stagehand and user flags.

• New Features
  • Added ignoreDefaultArgs to LaunchLocalOptions and wired it through V3 to launchLocalChrome(), mapping to chrome-launcher’s ignoreDefaultFlags.
  • true drops all chrome-launcher defaults; string[] removes only exact-matched defaults and re-adds the rest from Launcher.defaultFlags(), preserving Stagehand defaults and user chromeFlags.

^{Written for commit 1426616. Summary will update on new commits.}

[changeset-bot]

🦋 Changeset detected

Latest commit: 1426616

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 4 packages

Name	Type
@browserbasehq/stagehand	Minor
@browserbasehq/stagehand-evals	Patch
@browserbasehq/stagehand-server-v3	Patch
@browserbasehq/stagehand-server-v4	Patch

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[github-actions]

This PR is from an external contributor and must be approved by a stagehand team member with write access before CI can run.
Approving the latest commit mirrors it into an internal PR owned by the approver.
If new commits are pushed later, the internal PR stays open but is marked stale until someone approves the latest external commit and refreshes it.

[cubic-dev-ai]

No issues found across 2 files

Confidence score: 5/5

• Automated review surfaced no issues in the provided summaries.
• No files require special attention.

Architecture diagram

sequenceDiagram
    participant User as Consumer/SDK
    participant V3 as V3 Service
    participant Local as launchLocalChrome
    participant CL as chrome-launcher (Lib)
    participant OS as Chrome Process

    User->>V3: init(localBrowserLaunchOptions)
    Note right of User: Includes NEW: ignoreDefaultArgs
    
    V3->>Local: launchLocalChrome(opts)
    
    Local->>Local: Initialize chromeFlags (Stagehand defaults + User flags)

    alt ignoreDefaultArgs is boolean (true)
        Note over Local: User wants to drop ALL chrome-launcher defaults
        Local->>Local: Set ignoreDefaultFlags = true
    else ignoreDefaultArgs is string[]
        Note over Local: User wants to selectively remove defaults
        Local->>CL: CHANGED: Launcher.defaultFlags()
        CL-->>Local: Returns built-in flags (e.g. --disable-extensions)
        Local->>Local: Filter defaults based on ignoreDefaultArgs
        Local->>Local: Prepend kept defaults to chromeFlags
        Local->>Local: Set ignoreDefaultFlags = true
    end

    Local->>CL: launch({ ..., ignoreDefaultFlags, chromeFlags })
    
    CL->>OS: spawn chrome with final flag set
    OS-->>CL: Process started (PID/Port)
    
    CL-->>Local: LaunchedChrome object
    Local-->>V3: Connection details
    V3-->>User: Browser Instance Ready

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