fix(cef): pace per-host browser creates + retry targetId resolve (shared-host burst-render)#5
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…red-host burst) A burst of opCreateBrowser on one shared cef_host handed its single CEF UI thread a pile of blocking CreateBrowserSync calls that serialized + contended the one shared GPU/Viz accelerated-surface handshake — later browsers got no surface and never painted (blank tile), and their targetId resolve wedged behind the create backlog. Two Swift-side fixes (CefProfileHost): - Per-host create pacing: createSendQueue + pumpCreateQueue send opCreateBrowser one at a time, spaced 0.18s, instead of all at once — each browser's create + surface handshake completes before the next contends the GPU process. Verified live: a 7-cefWebview burst on one shared host now renders all 7 (was 1/7). - resolveTargetId retry: the fire-once 5s probe missed pages that committed late under burst (empty `webview snapshot`). Re-probe every 0.5s up to ~4.5s while still pending — a sibling of the 33858fb fix in the same targetId path. Render is fixed; concurrent multi-tile agent-DRIVING still has a residual relay issue (2nd+ tile's CDP page target not found) tracked separately. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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Problem
When many browsers are created in a burst on one shared
cef_host(multiple views on one named profile — the P2 multiplex), most render blank. Reproduced live in Campus: a 7-cefWebview burst on one shared host rendered only 1 of 7; agent-driving the rest returned empty.Root cause
Each
opCreateBrowserruns a blockingCreateBrowserSyncon cef_host's single CEF UI thread. A burst hands the UI thread a pile of synchronous creates that serialize and contend the one shared GPU/Viz accelerated-surface handshake — later browsers get no surface and never paint (blank), and their dependent ops (resize-to-heal, targetId resolve) wedge behind the create backlog. 2-per-host always worked; 7-at-once is where it falls over. (The create/present path is unchanged since P2-step1, so this is a pre-existing multi-browser limit, not a step2 regression.)Fix (Swift-side,
CefProfileHost)createSendQueue+pumpCreateQueuesendopCreateBrowserone at a time, spaced 0.18s, so each browser's create + surface handshake completes before the next contends the shared GPU process.resolveTargetIdretry — the fire-once 5s probe missed pages that committed late under burst (emptywebview snapshot); re-probe every 0.5s up to ~4.5s while still pending. Sibling of the 33858fb fix in the same targetId path.Verification
Live, firebase-dev Campus build: a 7-cefWebview burst on one shared host now renders all 7 (was 1/7).
Known follow-up (not in this PR)
Concurrent multi-tile agent-driving still has a residual: only one tile per shared host resolves a drivable CDP page target ("No page found" for the 2nd+). Rendering is fixed; the relay-multiplex page-target exposure is tracked separately.
🤖 Generated with Claude Code