Timeline Preload Lifetime

This manual benchmark uses the production app, restored session tabs, the real MessageTimeline preload, and the real Markdown worker. Only API data and result delivery timing are fixture-owned. It does not connect to a running OpenCode service or send prompts.

From packages/app, set absolute MARKDOWN_APP_BUILD_DIR and MARKDOWN_RESULTS_DIR artifact paths, then run:

bun run build
# Copy dist into MARKDOWN_APP_BUILD_DIR before editing production source.
bun --bun x playwright test --config e2e/performance/markdown/playwright.config.ts --repeat-each 20

Each isolated sample restores two sessions with one user message and one completed assistant text part each. The cold target has a realistic recovery review with either two TypeScript fences (typical) or 36 fences (large). The source has a short completed answer. Target data is prefetched before selection, but its Markdown is not parsed until the target is selected.

The app's service-worker generator reads dist, so use the normal build output and freeze a copy, rather than overriding Vite's build output directory.

The real worker result is held after admission. The test selects the original session again and releases the held result only after the abandoned timeline row detaches and the selected answer reports production Markdown readiness. This exercises both the timeline preload and the nested Markdown consumer, including the case where either one would otherwise keep a shared parse alive.

Destination readiness and post-disposal result settlement are separate metrics. The latter is a MessageChannel task after the result's promise microtasks drain. The DOMParser probe counts actual DOMPurify input containing the abandoned answer after disposal, in characters. CDP reports renderer task/script time and JS heap. These are not worker CPU, Electron process RAM, or ungated tab-switch measurements. In particular, this gate releases the result after destination readiness and must not be used to claim a destination-readiness gain from skipping sanitization.

MARKDOWN_ASSERT_DISPOSAL=1 enables the no-obsolete-sanitization assertion. Use MARKDOWN_RETAINED=1 only in separate post-GC runs. The repository trace collector is available through OPENCODE_PERFORMANCE_TRACE_DIR, and MARKDOWN_SCREENSHOT captures final output after timing. Run serially, preserve frozen builds, and keep all results outside Git.