fix(web): a maximized right panel stays maximized when you return to its thread

[jamesvillarrubia]

Problem

When you maximize the right panel to use a thread as a full-window preview, the chat column comes back after you visit Settings or open another thread. Fixes #17326.

ChatView kept the maximize flag in component state holding one thread key, so a ChatView remount, or maximizing a different thread's panel, dropped it.

Change

The flag moves into rightPanelStore as an optional maximized field on each thread's panel state, beside the open, tab, and active-tab state the store already saves per thread. ChatView reads it from the store.

• Closing the panel with its close button still clears the flag, as before.
• setMaximized goes through the store's automatic-update path, so maximizing does not count as a manual panel choice and does not block proactive diff or PR panels. The old component state did not either.
• Saved state from before this change has no maximized field and loads unchanged, so the storage version stays at 14. The migration keeps the field for any future version bump.

Scope and approval

Small, focused fix for an obvious bug: the panel drops a layout the user chose while the user does nothing to the panel. Bug report: #17326.

Discussion #16893 asks for the flag to survive an explicit close. This PR leaves close behavior alone.

#16434 and #14881 also edit toggleRightPanelMaximized. Whichever lands second needs a small rebase.

Verification

• vp test run apps/web/src/rightPanelStore.test.ts: 82 passed. Two new tests check that each thread keeps its own flag without bumping the manual-choice revision, and that migration keeps a saved maximized: true. Both failed before the change (setMaximized is not a function; migrated flag undefined).
• apps/web typecheck passes. Lint reports no warnings on the changed lines.
• Desktop dev build with sample data, before and after, for two paths: Settings and back, and another thread and back.

Before	After

Before (main):

t3code-maximize-before.mp4

After (this branch):

t3code-maximize-after.mp4

Not checked: mobile, which has no maximize control; the hosted web app, which runs the same web code.

Claude Opus 5.5 in Claude Code, run from T3 Code.

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ℹ️ Recent review info

⚙️ Run configuration

• Configuration used: Path: .coderabbit.config.ts
• Review profile: CHILL
• Plan: Advanced
• Run ID: 2d211871-1bf5-4a96-9e51-4fa9fc49afc0

📥 Commits

Reviewing files that changed from the base of the PR and between 7b57b72 and 4329f7f.

📒 Files selected for processing (3)

• apps/web/src/components/ChatView.tsx
• apps/web/src/rightPanelStore.test.ts
• apps/web/src/rightPanelStore.ts

Included review availability: This review used your included allowance. Your plan provides up to 10 included reviews per hour; 9 remain after this review.

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📝 Walkthrough

Walkthrough

Right-panel maximization is now stored in the right-panel store per thread. ChatView reads and updates the active thread’s maximization state. Closing the panel clears that state.

Changes

Per-thread right-panel maximization

Layer / File(s)	Summary
Store maximization per thread apps/web/src/rightPanelStore.ts, apps/web/src/rightPanelStore.test.ts	The store adds an optional maximized flag and a setter that updates it without changing surfaces or the user-action revision. Migration preserves the flag only when its value is exactly true. Tests cover state isolation between threads and migration.
Use thread-scoped panel state apps/web/src/components/ChatView.tsx	ChatView reads maximization from the active thread’s stored state. The maximize toggle updates that state, and closing the panel clears it.

Priority: ⬇️ Low

Estimated code review effort: 2 (Simple) | ~10 minutes

Change: Bug fix · Severity of issue fixed: Low

Suggested reviewers: juliusmarminge

Merge Risk: ⚪ Minimal · up to 4329f

Maximization is retained per thread, and the reviewed paths show no concrete remaining regression. The change is ready to merge subject to normal checks.

Security Architecture Review

Security architecture risk: 🔵 Low · up to 4329f

The change persists a layout preference without adding permissions or changing which resources a panel can access. Existing saved state remains compatible. Remaining uncertainty concerns cleanup and interrupted layout updates, rather than a demonstrated security exposure.

Retained concerns
No architecture-level concerns identified.

Security review details

Security Blast Radius

• inferred — The changed preference is retained in the browser's existing right-panel storage and addressed per environment and thread. The inspected change does not enlarge service authority or introduce a new resource-access sink.

Trust Boundaries and Controls

• inferred — A persisted maximized value influences layout rather than granting access: ChatView requires exact true and an already-open eligible panel, while the setter does not create or replace surfaces. Migration's exact-true check is layout normalization, not an authorization control.

🚥 Pre-merge checks | ✅ 4

✅ Passed checks (4 passed)

Check name	Status	Explanation
Linked Issues check	✅ Passed	For #17326, the change stores maximized in rightPanelStore per thread and makes ChatView read that value. This preserves the maximized layout across route remounts and thread changes. `setMaximi…
Out of Scope Changes check	✅ Passed	The changed files are ChatView.tsx, rightPanelStore.ts, and rightPanelStore.test.ts. The implementation, migration handling, and tests directly support #17326. No unrelated product behavior or u…
Description check	✅ Passed	The description is complete and follows the repository template. It explains the problem, the store-based fix, scope and approval rationale, focused test results, manual verification, screenshots, rec…
Title check	✅ Passed	The title clearly and concisely describes the primary fix: preserving a maximized right panel when returning to its thread.

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