Deep dives on designing production LLM systems.https://vidyal.ai/https://vidyal.ai/blog/rag-system-10m-documents/https://vidyal.ai/blog/rag-system-10m-documents/How to size, build and measure retrieval-augmented generation over 10M documents: ingestion, hybrid retrieval, reranking, ACLs, cost and evals.Fri, 16 Oct 2026 00:00:00 GMTRetrieval & RAGragvector-searchretrievalevalsarchitecturehttps://vidyal.ai/blog/debugging-rag-wrong-answers/https://vidyal.ai/blog/debugging-rag-wrong-answers/A stage-by-stage method for localizing RAG failures: build a replayable failure set, attribute each case to a stage, fix the biggest bucket, and gate on it.Fri, 16 Oct 2026 00:00:00 GMTRetrieval & RAGragevalsllm-as-judgeobservabilityhallucinationhttps://vidyal.ai/blog/chunking-legal-contracts/https://vidyal.ai/blog/chunking-legal-contracts/Why fixed-size chunks fail on contracts, and how to chunk by clause with context headers, defined terms, cross-references and amendment lineage.Fri, 16 Oct 2026 00:00:00 GMTRetrieval & RAGchunkingragretrievalevalshttps://vidyal.ai/blog/bm25-dense-hybrid-search/https://vidyal.ai/blog/bm25-dense-hybrid-search/How lexical, dense, learned-sparse and late-interaction retrieval fail differently, how to fuse them with RRF, and how to choose on your own traffic.Fri, 16 Oct 2026 00:00:00 GMTRetrieval & RAGretrievalvector-searchragrerankingevalshttps://vidyal.ai/blog/reranker-evaluation/https://vidyal.ai/blog/reranker-evaluation/How to add a cross-encoder reranker to a RAG pipeline, size it, and prove the gain with paired offline evals, end-to-end checks and a guarded A/B test.Fri, 16 Oct 2026 00:00:00 GMTRetrieval & RAGrerankingretrievalevalslatencycosthttps://vidyal.ai/blog/cut-llm-cost-70-percent/https://vidyal.ai/blog/cut-llm-cost-70-percent/How to stack prompt caching, model routing, batch APIs and token hygiene into a 70-80% cost cut, with an eval gate that proves quality held.Fri, 16 Oct 2026 00:00:00 GMTCost, Latency & Servingcostcachingroutingevalshttps://vidyal.ai/blog/reduce-time-to-first-token/https://vidyal.ai/blog/reduce-time-to-first-token/Decompose TTFT into network, pre-model work, queueing and prefill, then cut each stage: parallelism, prefix caching, chunked prefill and headroom.Fri, 16 Oct 2026 00:00:00 GMTCost, Latency & Servinglatencyservingcachinggpustreaminghttps://vidyal.ai/blog/semantic-cache-hit-rate-tracking/https://vidyal.ai/blog/semantic-cache-hit-rate-tracking/A layered semantic cache for LLM responses: scoped keys, tuned thresholds, borderline verification, invalidation, and false-hit-aware hit-rate metrics.Fri, 16 Oct 2026 00:00:00 GMTCost, Latency & Servingcachingvector-searchcostobservabilityhttps://vidyal.ai/blog/routing-cheap-and-strong-models/https://vidyal.ai/blog/routing-cheap-and-strong-models/Design an LLM router that sends each request to the cheapest good-enough model: rules, learned routers, cascades, threshold tuning and drift monitoring.Fri, 16 Oct 2026 00:00:00 GMTCost, Latency & Servingroutingcostevalsllm-as-judgehttps://vidyal.ai/blog/reliable-tool-using-agents/https://vidyal.ai/blog/reliable-tool-using-agents/Tool-use reliability is a systems property: tool design, a guarded control loop, permission gates, and pass^k evals on verifiable end states.Fri, 16 Oct 2026 00:00:00 GMTAgents & Tool Useagentstool-usestructured-outputevalsprompt-injectionhttps://vidyal.ai/blog/agent-loop-detection-recovery/https://vidyal.ai/blog/agent-loop-detection-recovery/Classify why an agent loops, add harness guardrails and better tool feedback, and recover with an escalation ladder you can measure.Fri, 16 Oct 2026 00:00:00 GMTAgents & Tool Useagentstool-useobservabilityevalshttps://vidyal.ai/blog/long-term-memory-assistant/https://vidyal.ai/blog/long-term-memory-assistant/A tiered memory design with explicit write, read and forgetting policies, plus the benchmarks and production signals that show it works.Fri, 16 Oct 2026 00:00:00 GMTAgents & Tool Usememoryagentsretrievalprivacyevalshttps://vidyal.ai/blog/guaranteed-valid-json-output/https://vidyal.ai/blog/guaranteed-valid-json-output/Enforce JSON Schema at decode time, design schemas that keep quality high, and add validation, repair and truncation handling on top.Fri, 16 Oct 2026 00:00:00 GMTAgents & Tool Usestructured-outputtool-useservingevalshttps://vidyal.ai/blog/detecting-reducing-hallucinations/https://vidyal.ai/blog/detecting-reducing-hallucinations/Separate hallucination types, detect them with claim-level verification and uncertainty signals, and reduce them without making the model useless.Fri, 16 Oct 2026 00:00:00 GMTEvaluation & Reliabilityhallucinationevalsragllm-as-judgehttps://vidyal.ai/blog/support-bot-eval-suite/https://vidyal.ai/blog/support-bot-eval-suite/Build support-bot evals from real failures: layered offline tests, calibrated judges, statistically sound release gates and a production flywheel.Fri, 16 Oct 2026 00:00:00 GMTEvaluation & Reliabilityevalsllm-as-judgeagentstool-useobservabilityhttps://vidyal.ai/blog/trustworthy-llm-as-a-judge/https://vidyal.ai/blog/trustworthy-llm-as-a-judge/Treat an LLM judge like a measurement instrument: calibrate it against human labels, remove its known biases, and size your eval sets for real error bars.Fri, 16 Oct 2026 00:00:00 GMTEvaluation & Reliabilityevalsllm-as-judgeobservabilityhttps://vidyal.ai/blog/prompt-injection-defense-tool-agents/https://vidyal.ai/blog/prompt-injection-defense-tool-agents/Why model-level filters can't stop prompt injection, and how control/data separation, taint tracking and sink policies make attacks harmless.Fri, 16 Oct 2026 00:00:00 GMTSecurity & Privacysecurityprompt-injectionagentstool-usearchitecturehttps://vidyal.ai/blog/pii-redaction-gateway/https://vidyal.ai/blog/pii-redaction-gateway/A layered design for detecting, pseudonymizing and re-identifying PII before it reaches a model, and how to measure the leak rate honestly.Fri, 16 Oct 2026 00:00:00 GMTSecurity & Privacyprivacysecurityarchitectureobservabilityhttps://vidyal.ai/blog/fine-tuning-vs-rag-vs-prompting/https://vidyal.ai/blog/fine-tuning-vs-rag-vs-prompting/Diagnose whether your gap is knowledge or behavior, then climb from prompting to RAG to fine-tuning only when the cheaper rung plateaus.Fri, 16 Oct 2026 00:00:00 GMTFine-tuning & Adaptationfine-tuningragevalscostarchitecturehttps://vidyal.ai/blog/lora-fine-tuning-5k-examples/https://vidyal.ai/blog/lora-fine-tuning-5k-examples/A practical LoRA recipe for an 8B model on 5K examples: data hygiene, hyperparameters, a real GPU memory budget, and eval-driven checkpoint selection.Fri, 16 Oct 2026 00:00:00 GMTFine-tuning & Adaptationfine-tuningloraevalsgpuservinghttps://vidyal.ai/blog/serving-open-llms-at-scale/https://vidyal.ai/blog/serving-open-llms-at-scale/How to size and run an open-weight LLM fleet: prefill vs decode, KV-cache math, continuous batching, FP8/FP4 quantization and goodput per dollar.Fri, 16 Oct 2026 00:00:00 GMTCost, Latency & Servingservinggpulatencycostcachinghttps://vidyal.ai/blog/sse-streaming-disconnects/https://vidyal.ai/blog/sse-streaming-disconnects/Stream tokens with server-sent events, decouple generation from the connection, resume with Last-Event-ID, and cancel cleanly so GPUs are freed.Fri, 16 Oct 2026 00:00:00 GMTProduction Engineeringstreaminglatencyarchitectureservinghttps://vidyal.ai/blog/tracing-multi-agent-workflows/https://vidyal.ai/blog/tracing-multi-agent-workflows/Model multi-agent runs as one OpenTelemetry trace: GenAI span conventions, context propagation across queues, private content storage and tail sampling.Fri, 16 Oct 2026 00:00:00 GMTProduction Engineeringobservabilityagentstool-useprivacyevalshttps://vidyal.ai/blog/prompt-rollback-production/https://vidyal.ai/blog/prompt-rollback-production/Make prompt rollback a sub-minute alias flip, catch regressions with canaries and guardrail metrics, and clean up what the bad prompt left behind.Fri, 16 Oct 2026 00:00:00 GMTProduction Engineeringdeploymentevalsobservabilityarchitecturehttps://vidyal.ai/blog/chat-service-1m-daily-users/https://vidyal.ai/blog/chat-service-1m-daily-users/Back-of-envelope sizing, architecture and overload strategy for an LLM chat product at 1M DAU, where GPUs set both the cost and the latency.Fri, 16 Oct 2026 00:00:00 GMTProduction Engineeringarchitectureservingcoststreamingcachingrouting