Composer History Hydration

Manual benchmark for an empty destination composer. Runs the production ComposerEditor, createComposerEditor, createComposerHistory, persistence codec, and browser IndexedDB draft store. It does not run the surrounding app shell or native desktop IPC.

Workload: 100 normal prompts with realistic review instructions/code and 100 shell commands. Separate cases have no images, 50 unique screenshots, or 50 references to 5 screenshots. The fixture generates valid 1440 x 900 PNG code screenshots before timing and reports their exact byte sizes. Each isolated browser context measures a cold URL-cache mount followed by a warm remount. The database was just seeded; this does not simulate a cold disk cache.

historyReadyMs measures the mount action until both production history stores are populated. This is history availability, not time to first editable input (input can be usable before history finishes). The benchmark then verifies ArrowUp recall and a decoded screenshot in the real editor. recallObservedMs includes Playwright action/assertion overhead and is reported separately. mountRecallObservedMs includes the mount, readiness checks, keyboard action, and correct text/image completion; it also includes Playwright overhead. IndexedDB reads and blob sizes are mechanism metrics, not desktop IPC bytes or process memory. No timing threshold is enforced.

From packages/app, set OPENCODE_HISTORY_BUILD and OPENCODE_HISTORY_OUTPUT to artifact directories outside Git, then run:

bun x vite build --config e2e/performance/composer-history/vite.config.ts
bun x playwright test --config e2e/performance/composer-history/playwright.config.ts --repeat-each=20

The preview server owns port 4783 and is stopped by Playwright. Preserve each build and its revision/hash for comparisons. BENCHMARK JSON lines contain all raw samples. Optional Chrome traces use the existing OPENCODE_PERFORMANCE_TRACE_DIR setting; keep trace runs separate from clean timing. Screenshots are captured after timing on the first repeat only.