> ## Documentation Index > Fetch the complete documentation index at: https://vietbui.mintlify.site/llms.txt > Use this file to discover all available pages before exploring further. # Verification Pipeline > 'Exit code 0 means no errors — not it's good.' # Verification Pipeline **"Exit code 0 means no errors — not it's good."** The verification pipeline is a layered quality system for autonomous agents that catches failures invisible to the layers below. Built from production failures (30+ campaigns, 198 agents), it exists because structural correctness and functional correctness are orthogonal. ## The Four-Tier Quality Ladder | Tier | What It Checks | What It Misses | | -------------------------- | -------------------------------------------------------- | ------------------------------------------------- | | **1. Typecheck** | Syntax, types, imports | Invisible features, broken layouts, empty screens | | **2. Visual Verification** | Does it render? DOM elements by data-testid, screenshots | Interaction behavior (long-press, drag, timing) | | **3. Screenshot Gate** | Hard gate: no screenshots = no completion | Correctness of what's rendered | | **4. Design Critique** | Three-perspective evaluation: Spec / User / Art Director | Project-specific taste | Most AI coding tools stop at Tier 1. The industry is still debating whether agents should run tests at all. ## Origin: The Show Bible Failure An autonomous agent completed a multi-phase campaign, passed typecheck, exited confidently. 37 of 38 entity cards were invisible. One manually-created test entity rendered; everything the agent built was structurally correct and completely non-functional. This is the foundational failure of autonomous AI code generation. **The gap between "compiles" and "works" is where real users live.** ## Tier 2: Visual Verification Implementation Playwright navigates real routes in a real browser: * Counts DOM elements by `data-testid` * Captures screenshots as artifacts * Configured per route (13 routes in the reference implementation) If a view that should have 38 entity cards has zero, this tier catches it. ## Tier 3: Screenshot Gate Hard enforcement, not a suggestion. If an agent modified `.tsx` files during a campaign, it **cannot complete** without screenshot artifacts. No screenshots = no completion signal. This converts visual verification from optional to mandatory for UI-touching work. ## Tier 4: Design Critique Three evaluator perspectives: * **Spec Auditor** — does the output match requirements? * **User Advocate** — would a human enjoy this? * **Art Director** — does it match the project's visual identity? Maximum two refinement rounds before escalating to human review. The cap prevents infinite loops on subjective quality. **Limitation**: Tier 4 requires project-specific taste definition. "Does this feel inhabited?" only works if you've defined what "inhabited" means for your project. Non-transferable. ## Interaction Testing Gap (known ceiling) Bugs that pass all four tiers are still possible: * Long-press behavior * Spawn mechanics * FPS degradation over time These require manual interaction. Automated interaction testing is the identified next frontier. ## Protocol Rules From Failures **"Layer, don't replace"**: add new components beside working ones, verify visually, then remove the old version. Origin: 841 lines of working components replaced with 144 lines of broken output by agents that never rendered their work. **"Design target, not delta"**: define the end state before starting; converge toward a reference, not away from a baseline. Origin: agent in infinite improvement loop because "done" wasn't defined. **Plan validation gate**: check the agent's decomposed plan against the original request before execution begins. Origin: agent truncated its own scope in self-authored plan, declared done after 2 of 6 waves. **Merge-before-cleanup**: worktree branches must be merged before cleanup runs. Origin: three agents' completed work vanished silently when branches were cleaned without merging. **Claim-before-resume ordering invariant**: prevents two agent instances from picking up the same active campaign (TOCTOU race condition). Origin: two Archon instances editing the same files simultaneously. ## Anti-Pattern Accumulation When AI agents generate code one file at a time, anti-patterns that are individually reasonable accumulate silently across the codebase. A cross-file DOM audit found 193 `repeat:Infinity` animations and 362 `backdrop-blur` instances — no single file was the bottleneck, but collectively devastating to performance. Background cleanup agents running on a daily cadence prevent this debt from compounding. See [Agent Harness](/concepts/agent-harness) (Entropy / garbage collection principle). ## Relationship to Harness Engineering The verification pipeline is an instantiation of the harness principle "Application legibility" — wire the app's own observability into the agent runtime so it can self-validate without human QA involvement. It extends [Ralph Loop](/concepts/ralph-loop) with completion conditions tied to verification passing rather than code existing. ## Production Results (reference implementation) The four-tier pipeline was built and validated across: 198 agents spawned, 32 fleet sessions, 30 campaigns completed, 296 features delivered, 90.6% session completion rate, 3.1% merge conflict rate, 0 circuit breaker activations. **Discovery relay**: findings from Wave N are compressed and injected into Wave N+1's context — prevents agents from reinventing each other's decisions across parallel waves. **Scope overlap circuit breaker**: 1 file-scope conflict = pause wave; 2 conflicts = stop session entirely. ## Related Pages * [Agent Harness](/concepts/agent-harness) — harness design principles including application legibility and entropy/GC * [Ralph Loop](/concepts/ralph-loop) — completion conditions; verification as the exit signal * [Agentic Sandbox Controls](/concepts/agentic-sandbox-controls) — sandbox security; visual verification runs in a real browser (security boundary) * [CI/CD Testing](/concepts/cicd-testing) — broader CI/CD testing strategy; verification-pipeline is one quality gate within it * [Unit Testing](/concepts/unit-testing) — unit testing as the foundation layer beneath agent-specific verification * [LLM Eval Pipeline](/concepts/llm-eval-pipeline) — the broader eval system this pipeline feeds into; CI gates, golden datasets, production monitoring