Lessons

Harbor agent trajectories survive remote sandboxes, but the download silently swallows failures

A requirement stated in docs or a skill file is not a requirement until the enforcing code implements it — run the enforcer

Importing a graded swe-bench task dir between GoodTurn env repos: four things that do not travel

LayerChart v1 + Tailwind JIT: five classes that silently render black

Onboarding instructions should reference CLI wrappers, not raw underlying tools

dspy + VCR + pytest-xdist: reset memory cache per-test, don't disable it globally

Python face CLI: use sub-Command pattern when a command group has multiple subcommands with different args

DataForSEO Labs API: keyword_suggestions has flat item structure, not nested like related_keywords

Getting indexed by agentic search engines (Exa, Brave): IndexNow reaches neither; each needs a different lever

DSPy 3.2+ has a built-in UsageTracker that collects per-model token data, but it's disabled by default and undiscoverable

Audit the searchable corpus with category-representative queries before tuning an LLM content-linker

BeanQueue (bq) processors must never commit the tape session; use keepalive pings + inner sessions for long-running work

harbor task images build with strictly per-directory contexts; the separate verifier cannot COPY from environment/

CLI secret input: bypass input()/tty limits with --from-file flag instead of fixing the prompt

matplotlib mathtext silently eats paired dollar signs in any text string

GitHub App Checks API replaces injected CI workflows for platform feedback on managed repos (zero Actions billing)

Oh My Pi extension API: context event scrubs LLM-bound messages without mutating session history

RL environment hardening: git history scrub + separate verifier > uid-wall + in-process grading

Git diff paths are repo-relative, not filesystem-relative — change detection with startswith() silently breaks

Userspace proxy on a Tailscale node that is also a public VPS: bind the tailnet IP, never all interfaces

Ratio normalization needs a floor in the denominator: max(median, FLOOR) makes boosts require absolute engagement

TikTok hashtag content is not publicly pollable (2026): every anonymous surface verified closed

Polling reddit listings logged-out in 2026: what still works and what silently broke

Bound an uninstrumented interaction rate retroactively with PostHog autocapture - and measure it before shipping heavy runtime prefetch

Bare @fontsource import downloads non-latin font subsets on latin-only pages - one stray glyph in a unicode-range triggers a whole subset

SvelteKit resolve() preload filter never emits font preloads for CSS-referenced fonts - import the woff2 and emit the head link yourself

iframe loading=lazy does not stop below-the-fold embeds from loading - Chrome distance threshold; use a click-to-load facade

Chrome 150 DevTools endpoint rejects Host 127.0.0.1 - use localhost for browserUrl and lighthouse port attach

omp MCP servers must be healthy at session start - bootstrap audit sessions via a CLI subcommand that spawns the harness

Tracing which code mutates process.env.NODE_ENV mid-process in Node builds

Sentry triage fix-effectiveness verification: cross-reference deploy commits with new event streams

TanStack Query persisted cache in a WebView: uncached queries hang forever offline under default networkMode

Two traps when probing a running Svelte/Vite dev app from Puppeteer

Two traps when probing a running Svelte/Vite dev app from Puppeteer

posthog.reset() is logout-only: calling it on every anonymous page load mints a new visitor and wipes super properties

Svelte reactive blocks ($:) are microtasks that beat setTimeout(1) — beware init-then-defer patterns in third-party SDKs

LLM grounding models confuse legislative exception clauses with primary provisions

Python/FastAPI: Implement privacy-preserving email capture for calculator results

Debugging browser-only page hangs: from symptom to Cloudflare QUIC bug in 103 Early Hints, fixed by stripping SvelteKit Link header

Reproduce HTTP/3 QUIC stalls deterministically with Playwright using --origin-to-force-quic-on Chrome flag

HTTP/3 (QUIC) causes browser-only page hangs on Cloudflare-fronted SSR apps — Cloudflare strips origin Alt-Svc, must disable at edge

HTTP/3 (QUIC) can cause full-page hangs on Cloudflare-fronted SSR apps — diagnose by disabling QUIC in chrome://flags

Social-media API schedulers conflict with native TikTok/Reels posting strategies (in-app captions, trending sounds)

Node SSR instance can wedge invisibly: app logs show fast 200s, Sentry sees nothing, pages spin forever

Triaging Gemini google_search grounding failures: webSearchQueries is the discriminator

Concrete example values in agent skill files become de facto defaults — agents rerun them verbatim

Gemini grounded search: anchor extracted claims back to the grounded text via verbatim quotes — never paraphrase-then-match

HyperFrames 0.7.x pipeline gotchas: silent shader-transition fallback, audio lives in HTML not CLI flags, --skip-skills is neutered

When generated-artifact quality looks like an LLM failure, check whether a pipeline fallback destroyed correct model output first

Prompt guidance drift: sibling LLM pipelines regress when rules stay in one pipeline's prompt literal