Cross-platform secret storage abstraction supporting macOS Keychain, Windows Credential Manager, Linux Secret Service (D-Bus), and an encrypted file backend with age. Implements file locking for concurrent access safety, configurable timeouts to prevent headless hangs, keyring backend auto-detection with explicit override, and secure token/secret CRUD with verified writes. The encrypted file backend uses age encryption with scrypt key derivation and stores entries with encoded keys for Windows compatibility. Demonstrates non-obvious skill in handling platform-specific keychain quirks (macOS lock detection, Linux D-Bus timeouts, Windows ERROR_LOCK_VIOLATION) and migration between backends.

Gmail watch/push notification processor that manages Pub/Sub push and pull subscriptions with history-based synchronization. Implements history ID tracking with resync on 404s, message ID deduplication across added/deleted/labelsAdded/labelsRemoved, configurable fetch delays to avoid racing message indexing, circuit-breaker-style rate limit handling with Retry-After respect, and reliable webhook delivery with exponential backoff. The processor separates notification handling (fast ACK) from payload processing (fetch + deliver), supports history type filtering, and maintains atomic state updates across concurrent watch processes via file-locked repository. Reusable pattern for any Google API push notification consumer.

Sed-style regex find/replace engine for Google Docs that operates on UTF-16 code unit indices (required by Docs API). Parses expressions with address ranges (line numbers, regex matches, nth occurrence), brace expressions for inline formatting (bold, italic, code, links, super/subscript), and table cell targeting. Plans mutations in reverse document order to preserve index validity after earlier edits. Handles complex cases: addressed vs unaddressed commands, table creation placeholders, image selectors with deterministic ordering, formatting range alignment after length-changing replacements, and orphaned comment detection. The planner/executor separation enables dry-run preview. Demonstrates deep understanding of Google Docs API mutation semantics.

Persisted, revision-locked request batch system for Google Docs. Allows composing supported mutations locally, splitting large batches to stay within API limits, and submitting atomically with revision verification. On partial failure, preserves successful splits and individual batch submissions before reporting missing response revision, preventing duplicate submissions on retry. State stored in versioned JSON with file locking for concurrent safety. Dry-run modes validate without creating state directories or lock files. Reusable pattern for any API requiring atomic multi-request transactions with recovery.

Encrypted backup system using age encryption with Git-backed sharded storage. Implements streaming shard construction for large Gmail exports (byte-splitting to stay under GitHub blob limits), checkpoint commits during long fetches for offsite progress, ordered background push queue so fetches continue during uploads, and manifest-based verification without full decryption. Supports Gmail (labels, raw messages, Markdown mirrors), Calendar, Contacts, Tasks, Drive metadata, Docs/Sheets/Slides/Forms native data, Apps Script, Chat, Classroom, Keep, Admin Directory, and Cloud Identity groups. Config-driven service selection with per-service error shards for optional services. Reusable pattern for large-scale encrypted data export with resumability.

Email open tracking with Cloudflare Worker backend and D1 database. Implements versioned encryption key rotation (1-byte version prefix in tracking ID) so new pixels use current key while old IDs decrypt through prior keys. Bot detection: Gmail Image Proxy (human), Apple Mail Privacy Protection, Outlook prefetch, rapid opens (<2s), security scanners. Deduplication: per-tracking-ID + IP + UA within 1 hour. Rate limiting: 100 opens/IP/hour. Retention: 90-day auto-purge via cron. Admin endpoint with Bearer token auth, capped at 500 rows. Worker written in TypeScript with vitest tests. Reusable pattern for privacy-respecting email analytics.

Unified Google API client factory with transport-level retry (429/5xx with exponential backoff), circuit breaker (5 failures opens, 30s reset), and support for multiple auth modes: user OAuth (keyring/ADC/direct token), service accounts (domain-wide delegation), and API keys. Creates service clients on-demand with proper scopes per service (e.g., Keep requires service account, YouTube supports API key + OAuth). Handles token refresh with rotated refresh token persistence. Read-only transport wrapper for --readonly enforcement. Centralizes error classification (accessNotConfigured -> enablement hints). Reusable pattern for any multi-service Google API consumer.

Build-time safety profile compilation that parses YAML allow/deny rules (with 'all' wildcard) and generates a Go file with FNV-64a hash switches. Runtime matcher uses constant-time hash lookups instead of string comparisons, so rule strings never appear in binary data section. Profiles: readonly (read-only), agent-safe (curated allowlist), full (no restrictions). The generator sorts and deduplicates rules, emits allowAll constant for 'all' wildcard. Tests mutate a test-only profile struct; production builds compile the generated hash switch. Fail-closed: missing profile = disabled. Reusable pattern for supply-chain safety controls.

Markdown to Google Slides parser supporting slidey-flavored deck format: per-slide YAML frontmatter (layout, content), ## Notes for speaker notes, Font Awesome icon shortcodes, mermaid diagram rendering, ::cols::/::col2::/::col3::/::right:: column layouts, ::boxes::/::arrows:: icon-row blocks. AST with blocks (paragraph, bullets, code, heading, columns, icon rows, diagram) and inlines (text, icon ref). Layout geometry calculator for column boxes. Exports: --fa-style, --mmdc path, --strict, --keep-temp-images, --no-notes. Reusable pattern for programmatic presentation generation from structured Markdown.