https://ta-blogs.web.app/rootcause/An engineering blog of real bugs hit while shipping small software products — the symptom, the diagnosis that actually worked, and the fix. Playwright, Firebase, Unity, zsh, Blender, and the traps that cost us days.https://ta-blogs.web.app/rootcause/shared-working-tree-parallel-agent-sessions-git-checkout/https://ta-blogs.web.app/rootcause/shared-working-tree-parallel-agent-sessions-git-checkout/Mon, 07 Sep 2026 00:00:00 GMTA branch belongs to a working tree, not to a session. When one session ran git checkout, the files changed under another session that was still editing them — and a cloud-synced .git made the evidence disagree with itself.https://ta-blogs.web.app/rootcause/firebase-auth-authorized-domains-multi-site-patch-replaces/https://ta-blogs.web.app/rootcause/firebase-auth-authorized-domains-multi-site-patch-replaces/Mon, 07 Sep 2026 00:00:00 GMTFirebase Hosting multi-site domains are not added to Auth's authorized domains automatically. You can fix it from the command line, but the PATCH replaces the whole list, and a missing header reports the wrong error.https://ta-blogs.web.app/rootcause/blender-headless-matrix-world-stale-before-view-layer-update/https://ta-blogs.web.app/rootcause/blender-headless-matrix-world-stale-before-view-layer-update/Mon, 07 Sep 2026 00:00:00 GMTAssembled models flew apart, a key's teeth became a giant cube, and a rocket drifted out of frame. Two traps in a headless Blender batch pipeline, both from reading matrix_world before the dependency graph had caught up.https://ta-blogs.web.app/rootcause/urp-always-included-shaders-590k-variant-explosion/https://ta-blogs.web.app/rootcause/urp-always-included-shaders-590k-variant-explosion/Sun, 06 Sep 2026 00:00:00 GMTAdding URP's shaders to Always Included Shaders fixed a magenta material and stopped the build from ever finishing. The project had five materials. Here is why that setting disables Unity's shader stripping, and the material-template fix that restored it.https://ta-blogs.web.app/rootcause/playwright-persistent-profile-chrome-version-downgrade/https://ta-blogs.web.app/rootcause/playwright-persistent-profile-chrome-version-downgrade/Sun, 06 Sep 2026 00:00:00 GMTA status tool opened our saved Playwright profiles with channel chrome. Every scheduled job that used those profiles then hung on launchPersistentContext. Chrome had migrated the profiles to a newer version and refuses to go back.https://ta-blogs.web.app/rootcause/firebase-functions-deploy-complete-but-shipped-stale-lib/https://ta-blogs.web.app/rootcause/firebase-functions-deploy-complete-but-shipped-stale-lib/Sun, 06 Sep 2026 00:00:00 GMTA Cloud Functions deploy reported success while uploading a stale lib directory, because the build script ended in "|| echo". Fixing that surfaced a second trap — module-scope admin.firestore() crashing at load, hidden by TypeScript's require emit order.https://ta-blogs.web.app/rootcause/ctrl-r-dead-in-pty-app-editor-vi-zsh-vi-mode/https://ta-blogs.web.app/rootcause/ctrl-r-dead-in-pty-app-editor-vi-zsh-vi-mode/Sun, 06 Sep 2026 00:00:00 GMTReverse history search was silently dead in our Electron/xterm.js terminal but worked in Terminal.app. Four layers of key-delivery tracing found nothing. The real cause was zsh switching to vi mode because of an inherited environment variable.