Writing: Screen Memory reads only the focused window

[r3dbars]

What

Screen Memory now reads only the window you're typing in. Owner decision, before release. Setup already says "Reads the window you're replying in, on this Mac." The code didn't do that: with no conversation in the focused window it read the whole display, so text from other visible windows and apps could get in, including apps outside the Writing app scope.

How

• New pure policy FocusedWindowCapturePolicy (Sources/TranscriptedWriting/Core/ScreenMemory/). At capture time it picks the typing target's window, or refuses. It captures only when all of these hold:
  • the window is on screen, layer 0, and owned by the target's process and bundle
  • the app isn't excluded (password managers always are) and is in the Writing app scope
  • it's the frontmost app, and that app's frontmost normal window
  • Accessibility names that same app as having keyboard focus. Unknown focus refuses (fail closed), so a non-activating launcher like Spotlight or Alfred can't read the window behind it.
• ScreenCaptureService: full-display capture, CaptureKindPolicy and the second window-snapshot slot are gone. It's the AX read or SCContentFilter(desktopIndependentWindow:) of the chosen window, and nothing else. It re-checks the app scope itself instead of trusting the app bridge alone. It also drops held text as soon as the user moves to another window or leaves the field.
• AXWindowTextReader reads only the app's focused window, and only when its frame matches the chosen one. It no longer walks the app's other windows and has no unmatched fallback.
• KeyboardFocusProbe (new, pids only). It reads NSWorkspace.frontmostApplication plus the system-wide AX focused application. It never sets a messaging timeout on the system-wide element, because that changes the timeout for every AX element in the process.
• Logs: each refusal logs its own fixed reason (not-frontmost-app, keyboard-focus-unknown, not-focused-window, …). Those reasons, plus no-target-window and target-changed, are now in DiagnosticsMetadataRedactor's allowlist. No bundle IDs, titles, text or paths get logged.
• Unchanged: master toggle, pause, Screen Recording permission, lock screen, secure input, cadence, and the trigger policy's "any visible excluded window blocks" rule. I kept that last one as the conservative choice.
• Sources/Writing/WritingController.swift isn't touched (another PR owns the poll wiring there). Setup copy still matches, and no visuals changed.

What's lost

• referenceSnippets from other windows. By design, that was exactly the full-display read.
• Screen Memory now needs Accessibility. Without it, keyboard focus is unknown and nothing is captured (keyboard-focus-unknown in the log). Transcripted already holds Accessibility for paste-back, so shipped installs should be fine. A dev build whose TCC grant broke on re-signing will just go quiet.

Tests

• New FocusedWindowCapturePolicyTests, one row per case: focused window in scope, other apps visible (incl. in front of the typing app), keyboard focus elsewhere, keyboard focus unknown, back window of the same app, off-screen sibling, focused window excluded, password manager with an empty list, out of scope, no identifiable window (no target, missing id/pid, gone, unknown frontmost, unranked, no bundle), owner mismatch, overlay layer.
• ScreenCaptureServiceTests: held text follows the typing window. Refusal → outcome mapping, plus every refusal reason is distinct, never contains the bundle ID, and survives the redactor literally.
• DiagnosticsMetadataRedactorTests updated in lockstep.
• Mutation probe on the new policy: 16/18 killed at first. I added a row for the real survivor (?? true). The other one (< → <=) is equivalent, since two windows can't share a z-rank.
• swift test --filter TranscriptedWritingTests on the final head (covers ScreenMemory and DiagnosticsMetadataRedactor): 925 tests in 111 suites, green.
• bash check.sh passed on d78ee347, the head before the review fixes: build.sh, run-tests, test-shape, concurrency census, build-deps, integration smoke, full swift test, source pins and doc paths. It wasn't rerun on the final head (release timing). The review-fix commit only touches ScreenMemory, the redactor allowlist, tests, comments and docs, so CI covers the rest.

Not proven here (manual): live capture on a real display. That covers Slack/Messages in front with another app visible, a launcher panel over an in-scope app, and AX revoked. Synthetic tests can't cover ScreenCaptureKit or real focus.

Review

Independent review by a separate reviewer thread came back REQUEST CHANGES (small):

1. Nil keyboard focus was permissive. Fixed: it now refuses.
2. Refusals logged as a redacted length. Fixed: distinct reasons, now allowlisted.
3. Nits: stale full-display wording, ledger drift. Fixed.

All addressed in the second commit.

🤖 Generated with Claude Code

[r3dbars]

Independent review: writing-reviewer agent reviewed the full diff (REQUEST CHANGES: fail closed on unknown keyboard focus; allowlisted per-refusal log reasons). Both addressed in the final commit; coordinator re-checked the summary. APPROVE on green CI. Owner decision honored: Screen Memory reads only the focused window.