fix(screenshot): fall back to CDP capture when captureVisibleTab fails - #83
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chrome.tabs.captureVisibleTab reads back the window surface, which fails outright on some Windows/Chrome combinations (Chromium FAILURE_REASON_READBACK_FAILED: "Failed to capture tab: image readback failed"), leaving full-tab screenshots without any working path. Capture the full tab via CDP Page.captureScreenshot (fromSurface) when the visible-tab capture rejects; the CDP path goes through the renderer BeginFrame pipeline instead of the surface readback. When both paths fail, return cdp_failed with data.reason=screenshot_capture_failed carrying both underlying messages, and render a CLI hint that points at the browser-side readback cause. Refs #71
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Motivation
Refs #71 — on some Windows + Chrome 151 setups,
bsk screenshotalways fails withFailed to capture tab: image readback failed. That error string is produced inside Chromium (FAILURE_REASON_READBACK_FAILEDinchrome/browser/extensions/api/tabs/tabs_api.cc): the browser's compositor fails to read the window surface back into a bitmap, sochrome.tabs.captureVisibleTabrejects and no image data ever reaches the extension. The full-tab screenshot path had no fallback, so a browser-side readback failure surfaced as a hard error.Changes
apps/extension/src/tools/observation.ts): full-tab capture now falls back to CDPPage.captureScreenshot(format: "png",fromSurface: true) whencaptureVisibleTabrejects. The CDP path captures through the renderer's BeginFrame pipeline instead of the window-surface readback thatcaptureVisibleTabdepends on. Overlay suppression (withOverlaysHiddenForCapture) wraps both attempts, and the CDP session is attached the same way the existing--refelement-capture path does it. When both paths fail, the error carriesdata.reason = "screenshot_capture_failed"and both underlying messages.crates/bsk-cli/src/cli/render_error.rs): newscreenshot_capture_failedreason override forcdp_failedwith a hint that points at the browser-side rendering/readback cause (reload tab / restart browser / upgrade or downgrade Chrome) instead of the generic "stuck DevTools session" copy.Page.captureScreenshotparams, (2) both paths fail →cdp_failed+screenshot_capture_failedreason + both messages, (3) primary success never touches CDP; a Rust unit test locking the new reason-override copy.Notes / honesty
The underlying readback regression is inside the browser, so this PR is a mitigation: it routes around the broken capture path rather than fixing it. The exact Chromium 151 change that breaks surface readback on the reporter's machine still needs verification on a real Windows environment.
Test plan
pnpm --filter @browser-skill/extension compilepnpm ext:test(618 passed)pnpm lintcargo fmt --all -- --check,cargo clippy --workspace --all-targets --locked -- -D warnings,cargo test --workspace --locked