Fix browser WebView refresh on workspace hide

[austinywang]

Summary

• make Browser Memory Saver opt-in so normal workspace hide/show keeps the live WKWebView and DOM state
• add a regression test for hiding past the discard delay without replacing the WKWebView
• keep explicit memory-saver discard coverage by enabling the policy inside those tests

Fixes #4387

Verification

• Not run locally per task instruction; CI will run the checks.

---

Note

Medium Risk
Changes the default browser tab lifecycle behavior by disabling hidden WebView discarding unless explicitly enabled, which could affect memory usage and tab restore behavior. Risk is mitigated by updated and new unit tests around discard/restore and workspace hide/show identity preservation.

Overview
Makes Browser Memory Saver opt-in by changing BrowserHiddenWebViewDiscardPolicy.defaultEnabled and the settings schema browser.discardHiddenWebViews default from true to false, so normal workspace hide/show keeps the same live WKWebView and DOM state.

Updates BrowserPanelWebViewLifecycleTests to manage discard-related UserDefaults per-test, skip appropriately when environment overrides make behavior unobservable, add a regression test asserting WebView identity is preserved when hidden past the discard delay with the policy disabled, and explicitly enable the policy in discard/restore tests to keep coverage.

^{Reviewed by Cursor Bugbot for commit 233dbe4. Bugbot is set up for automated code reviews on this repo. Configure here.}

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Summary by cubic

Make Browser Memory Saver opt-in so hidden tabs no longer auto-discard. Keeps the live WKWebView and DOM when a workspace is hidden and re-shown, fixing the refresh regression (addresses #4387).

• Bug Fixes
  • Default BrowserHiddenWebViewDiscardPolicy to disabled; update discardHiddenWebViews default in web/data/cmux.schema.json to false.
  • Preserve WKWebView identity across workspace hide/show to avoid reloads.
  • Add regression tests for the default-preserve behavior and for explicit memory-saver discard paths (with environment override handling).

^{Written for commit 233dbe4. Summary will update on new commits. Review in cubic}

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Project	Deployment	Actions	Updated (UTC)
cmux	Ready	Preview, Comment	May 19, 2026 9:57pm
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ℹ️ Review info

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Configuration used: Path: .coderabbit.yaml

Review profile: ASSERTIVE

Plan: Pro

Run ID: 96dadcf1-c233-4d24-a582-69dee52e1036

📥 Commits

Reviewing files that changed from the base of the PR and between 4d04459 and 233dbe4.

📒 Files selected for processing (3)

• Sources/Panels/BrowserHiddenWebViewDiscardPolicy.swift
• cmuxTests/GhosttyConfigTests.swift
• web/data/cmux.schema.json

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch issue-4387-browser-refresh-regression

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[greptile-apps]

Greptile Summary

This PR makes Browser Memory Saver (WebView discard on workspace hide) opt-in by changing defaultEnabled from true to false in both the Swift policy enum and the JSON schema, fixing a regression where normal workspace hide/show was discarding and recreating the live WKWebView.

• BrowserHiddenWebViewDiscardPolicy.defaultEnabled is flipped to false and cmux.schema.json is updated to match, so hidden-webview discard is now off unless the user explicitly enables it.
• A new regression test (testDefaultWorkspaceVisibilityHidePreservesWebViewIdentityPastDiscardDelay) verifies that hiding a workspace past the discard delay with the default policy preserves the original WKWebView identity and DOM state.
• Existing discard tests are wrapped with withHiddenWebViewDiscardDefaults(enabled: true) and appropriate skip guards so they continue to exercise the explicit opt-in path without being broken by the default change.

Confidence Score: 5/5

Safe to merge — the change is a one-line default flip in the policy enum, mirrored in the schema, with a targeted regression test and well-guarded updates to existing discard tests.

The default flip from opt-out to opt-in is minimal and correct. The new regression test directly exercises the fix path, and the skip guards and withHiddenWebViewDiscardDefaults wrapper keep existing coverage accurate. No production logic paths are altered beyond the default value.

No files require special attention.

Important Files Changed

Filename	Overview
Sources/Panels/BrowserHiddenWebViewDiscardPolicy.swift	Single-line change: flips defaultEnabled from true to false, making Browser Memory Saver opt-in instead of opt-out. Change is correct and consistent with the schema update.
cmuxTests/GhosttyConfigTests.swift	Adds a new regression test verifying that workspace hide/show preserves WKWebView identity when the policy is disabled (the new default); wraps existing discard tests with withHiddenWebViewDiscardDefaults(enabled: true) and skip guards to keep them green after the default flip. RunLoop-spin wait helper is test-only scaffolding refactored from existing inline code.
web/data/cmux.schema.json	Mirrors the Swift default change: discardHiddenWebViews default flipped from true to false. Schema description is developer-facing documentation; no i18n impact.

Flowchart

%%{init: {'theme': 'neutral'}}%%
flowchart TD
    A[Workspace hides BrowserPanel] --> B{BrowserHiddenWebViewDiscardPolicy.isEnabled?}
    B -- "env var = '1'/'true'/..." --> C[Policy ENABLED]
    B -- "env var = '0'/'false'/..." --> D[Policy DISABLED]
    B -- "no env var" --> E{UserDefaults key set?}
    E -- "yes" --> F{UserDefaults value}
    F -- "true" --> C
    F -- "false" --> D
    E -- "no (key absent)" --> G["defaultEnabled = false (changed in this PR)"]
    G --> D
    C --> H{hiddenDelay elapsed?}
    H -- "yes" --> I[discardHiddenWebViewForMemory → replaces WKWebView]
    H -- "no" --> J[Keep live WKWebView in liveHidden state]
    D --> J
    J --> K[Workspace shown → same WKWebView rebinds, no reload]
    I --> L[Workspace shown → new WKWebView restores from history]

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[cubic-dev-ai]

No issues found across 3 files

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