RAG Formation · Reference

Context assembly and evidence budgets

A standalone cheat sheet for learning and testing RAG quality on this site.

$ reference --status
▸ course RAG Formation
▸ mode standalone reference
▸ status Complete
● learn → test → verify

Reference sheet

The guided RAG Formation course content is complete; this reference is available for self-directed practice.

One-line rule

A retrieved source is not useful evidence if truncation removes it before the model sees it.

Term	Meaning
Context assembly	Turning backend results into the text sent to the answering model — across four channels (summary/vector/fulltext/graph), each given a fair share of the budget by a max-min allocation algorithm.
Evidence budget	The maximum context allowed by characters, tokens, latency, or cost.
Source survival	Whether the evidence needed for an answer is still present after formatting and truncation. Channel order is fixed (summary→vector→fulltext→graph) — budget fairness, not relevance ranking, decides how much of each survives.
Not the same path as Lessons 5–8	`--mode retrieval` hits `/api/v1/search` (no fusion). `--mode answer` hits `/api/v1/qa` (real per-channel allocation) — this lesson uses the latter.

Need	Record	Don't claim
Baseline	Command, configuration, observed result	The baseline is a target.
Change	One hypothesis or decision	You can tell what caused the result when several things changed.
Metric	Per question: `answer.stats.context_chars_by_index`, `.context_items_included`/`.context_items_dropped`, `.context_hard_truncated`, `answer.sources` and `.source_hit.all`. For multi-hop, check `context_chars_by_index.graph` first.	One metric tells you everything about quality.
Safety	A failure and a regression case	A fluent answer proves the system is reliable.

cd demo
python3 eval.py run --mode answer --workspace meridian_demo --category multi_hop --tag lesson-09-context

Artifact: An evidence-survival map for one multi-hop answer, plus a bounded context-budget recommendation.

Continue learning: Open the matching standalone lesson · Course roadmap