[PB Extension] Handle a missing lexicon without exposing full FW Lite

[imnasnainaec]

When a project's stored lexicon code points at a lexicon that no longer exists, "Browse lexicon" left FW Lite in its unrestricted view with the project switcher enabled, letting the user navigate out of the embedded experience.

FW Lite only learned it was embedded in Paratext inside projectContext.setup(), which runs after the project opens. A missing lexicon makes openCrdtProject/openFwDataProject throw, so setup() never ran and inParatext stayed false. The CSS-gated restrictions still applied (data-paratext is on the DOM from first render), but the switcher's disabled={projectContext.inParatext} did not — that mismatch is the bug.

• Set inParatext on the project context at construction, so the restriction holds while the project is loading and if it never loads. This also covers the case where resolveProjectType falls back to FwData for an unknown code and routes a Harmony project to the wrong view. The property is one-way: dev throws and prod logs on an attempt to turn it back off, mirroring how projectCode refuses re-assignment.
• Ignore project selection in the sidebar while in Paratext, as defense in depth, with a dev-mode warning so an unexpected reach past the disabled dropdown is visible rather than silent.
• Notify the user when a stored lexicon no longer resolves, instead of only logging before clearing it and reopening the selector.
• Validate the lexicon code in displayEntry, which bypassed the existing check and handed a dead code straight to the browse URL.
• Give the mini-lcm endpoint filter honest status codes: 404 for a missing project (FwLiteWeb mini-lcm routes return 500 instead of 404/400 for not-found and bad-request cases #2487) and 400 for its client-error paths (invalid project type, blank project code), which all defaulted to 500. The extension's validity check now treats 404 and 400 as definitive and everything else as transient. This matters because that check clears the user's stored lexicon, so it should act on a definitive answer rather than a backend fault — and a whitespace-only code reaches the blank-code branch, so 404 alone would have accepted it.

Test plan

Manual, with a Paratext project whose lexicon.lexiconCode setting names a lexicon that does not exist in FW Lite:

• "Browse lexicon" shows an error notification naming the lexicon and opens the lexicon selector; the full FW Lite view never appears.
• With a valid lexicon, browsing still opens the embedded view and the project switcher is disabled.
• Stop FW Lite mid-session, then invoke "Browse lexicon": the stored lexicon code is retained (not cleared) and the failure is logged.
• A whitespace-only lexicon.lexiconCode is rejected by the project-settings validator.

Automated: svelte-check clean, viewer unit tests pass (159), extension lint/build clean, FwLiteWeb builds. Viewer browser tests were not run locally (Playwright chromium not installed); they don't touch this code, but CI covers them.

Fixes #2440

Considered and rejected

Rendering a dedicated "lexicon not found" state in DotnetProjectView instead of the current toast-plus-ViewErrorBoundary path. It reads better, but it's a UX change beyond this bug, and the viewer's no-try/catch-around-async rule makes it more than a small diff. Worth a follow-up if the boundary message proves confusing.

🤖 Generated with Claude Code

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📥 Commits

Reviewing files that changed from the base of the PR and between 8d27bbb and 167dab0.

📒 Files selected for processing (7)

• backend/FwLite/FwLiteWeb/Routes/MiniLcmRoutes.cs
• frontend/viewer/src/DotnetProjectView.svelte
• frontend/viewer/src/project/ProjectSidebar.svelte
• frontend/viewer/src/project/project-context.svelte.ts
• platform.bible-extension/contributions/localizedStrings.json
• platform.bible-extension/src/main.ts
• platform.bible-extension/src/utils/project-manager.ts

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📝 Walkthrough

Walkthrough

The changes add explicit project route error statuses, separate Paratext mode from project setup, block project switching in Paratext, and improve recovery when a stored lexicon code is no longer valid.

Changes

Project and lexicon selection handling

Layer / File(s)	Summary
Explicit project route errors backend/FwLite/FwLiteWeb/Routes/MiniLcmRoutes.cs	Invalid project requests return HTTP 400 problem responses. Missing projects return HTTP 404 problem responses.
Paratext project context guard frontend/viewer/src/project/project-context.svelte.ts, frontend/viewer/src/DotnetProjectView.svelte, frontend/viewer/src/project/ProjectSidebar.svelte	Paratext mode is initialized separately, cannot be disabled after activation, and prevents project selection while embedded in Paratext.
Invalid lexicon recovery platform.bible-extension/src/main.ts, platform.bible-extension/src/utils/project-manager.ts, platform.bible-extension/contributions/localizedStrings.json	Lexicon validation handles only HTTP 400 and 404 as invalid selections, reports discarded codes, and opens the selector when required.

Estimated code review effort: 3 (Moderate) | ~20 minutes

Possibly related PRs

• sillsdev/languageforge-lexbox#2394: Modifies shared lexicon-selection and validation code.
• sillsdev/languageforge-lexbox#2438: Modifies lexicon project selection and localized strings.

Suggested reviewers: hahn-kev

Poem

I’m a rabbit guarding the project gate,
No Paratext switches while embedded state.
A lost lexicon gets a message bright,
Then the selector hops into sight.
Errors wear status codes neat—
Change complete, with carrot treat!

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly summarizes the main change: handling missing lexicons without exposing unrestricted FW Lite.
Description check	✅ Passed	The description directly explains the missing-lexicon bug, implementation changes, validation behavior, and test results.
Linked Issues check	✅ Passed	The changes satisfy issue #2440 by showing an error, reopening the selector, and preventing unrestricted FW Lite navigation.
Out of Scope Changes check	✅ Passed	The changes support the missing-lexicon fix and its required validation, embedding-state, navigation, notification, and HTTP status behavior.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

✨ Finishing Touches

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• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch pt/missing-lex-code

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Build	Status	Details	Updated (UTC)
default (Inspect)	✅ No changes detected	-	Aug 13, 2026, 12:33 PM
e2e (Inspect)	✅ No changes detected	-	Aug 13, 2026, 12:41 PM

[hahn-kev]

looks good to me, Looking at how project-context is created I think I want to refactor it, but that's out of scope of this PR.