fix: X post tips button — displaced share button, crash-hidden button, and slot flicker

[swkatmask]

Summary

Three fixes for the X (Twitter) post tips button, each verified live on x.com with a dev build:

mf-6844 — hidden tips slot displaced the share button

injectTipsButtonOnPost set flex: 1 on the share wrapper (leftover from the Mirror.xyz integration). Today's X sizes that wrapper to content, flush right; flex: 1 1 0% made it an extra growing item, left-aligning the share icon and leaving dead space at the action bar's right end on every post, even when the tips button was hidden. Fix: stop touching the wrapper's flex (measured on the live stock DOM: dead space 79px→0 with the button hidden; tips flush-right + share immediately before it when visible).

mf-6845 — degraded userinfo payloads crashed identity resolution

FireflyTwitter.getUserInfo trusted the proxied GraphQL shape. The backend degrades two ways: {code: 0, data: {}} (live fetch failed, nothing cached — protected accounts) crashed at res.data.data.user; __typename: 'User' without legacy (suspended/rate-limited lookups) passed validation and crashed every caller reading user.legacy.* — the reported identity.ts:119 Cannot read properties of undefined (reading 'screen_name'). Both crash paths feed the react-query entry powering PostTipsSlot, hiding that author's tips button. Fix: validate the chain and require legacy, returning null otherwise (AvailableTwitterUser keeps the guaranteed shape; wire types now model the degraded shapes).

mf-6846 — the tips button flickered (show → hide → show …)

Two stacked bugs in the injection:

• Self-unmatching selector. div:has([aria-haspopup="menu"]):last-child — the injected span is appended right after the match, so the match stopped being :last-child, the watcher dropped/destroyed it, it matched again, re-injected… infinite add/remove at MutationObserver cadence (measured: visible → removed → empty cycle every ~150ms). :last-child only existed to disambiguate from the retweet button.
• Full tree rebuild on every mutation. The callback hand-rolled a fresh DOMProxy + React tree on every onNodeMutation/onTargetChanged, tearing the rendered button down while the fresh tree re-resolved identity/accounts, sometimes leaving the live slot empty with the tree orphaned off-DOM.

Fix: match the share wrapper stably (the only action-bar menu button without a data-testid), use the watcher-provided DOMProxy (auto re-anchored on node replacement, auto-destroyed on removal), and mount the React tree once — remount only when the post's author changes.

Verification

• mf-6844: live DOM measurement on stock x.com (no extension) vs injected — share flush-right restored.
• mf-6845: backend probed for suspended (UserUnavailable), protected ({}) and healthy handles — all resolve to a complete user or null; callers degrade gracefully.
• mf-6846: 30s of rAF-frequency width sampling on a thread page shows a single stable state — tips button on posts by an author with MaskX-verified addresses stays visible (20px), authors without verified tip accounts stay hidden, zero transitions.

Refs: MF-6844, MF-6845, MF-6846

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1 Skipped Deployment

Project	Deployment	Actions	Updated
book	Skipped		Oct 12, 2026 11:32pm UTC