Distill Test Set

Turn a large, noisy dataset into a small, high-signal Coval test set. Big datasets are the wrong input for simulation: running thousands of sims is slow, expensive, and likely to overwhelm the agent under test, and most rows are duplicates, paraphrases, or boilerplate. The goal is a representative 10–50 case suite that covers the agent's real scenarios once each, weighted toward known failures.

Drive everything through the coval CLI and the bundled scripts/distill.py. Follow the phases in order. Present a summary and get confirmation before creating anything.

If $ARGUMENTS is a Coval test set id (8 chars) or a file path, use it as the source in Phase 1.

Why this skill instead of a plain import? Coval has two loaders, and neither dedupes: the CSV/XLSX importer and coval test-cases create --stdin load every row 1:1 (great once you've chosen your rows), while "Create test set → attach a file" runs an LLM that synthesizes only ~10–15 scenarios (a generation cap, not a representative sample). This skill does the dedup + representative selection itself, then loads the result with the uncapped path.

Phase 0: Preflight + Inventory

Step 1: Check authentication

coval whoami

If not authenticated: coval login (get a key at https://app.coval.dev/settings → Organization → Manage → API Keys). No account? https://coval.dev.

Before you start: this skill needs only the coval CLI and python3 (used by the bundled script and a couple of small JSON reads) — no jq or other tools. If coval is a shell alias on your machine, run the commands with coval-cli instead (which coval to check).

Step 2: Inventory existing test sets (so we don't clobber one)

coval test-sets list --format json

Note the ids/sizes. If the user wants to distill an existing Coval test set, confirm its id here.

Phase 1: Locate + Profile the Source Dataset

Determine where the large dataset lives. Two common cases:

1. An existing, oversized Coval test set — use --source coval:<TEST_SET_ID> (the script pulls every case via the API, paginated). Confirm the id and its size:

   coval test-sets get <TEST_SET_ID> --format json | python3 -c "import json,sys;d=json.load(sys.stdin);print(d.get('display_name'), d.get('test_case_count') or '(size shown in app)')"

2. A local file — CSV, JSON, or NDJSON of past conversations / SME-reviewed rows / logs.

Then identify the field mapping by inspecting a few rows:

• the user utterance / scenario field (--input-field, default input_str)
• the expected answer / behavior field (--expected-field, default expected_behaviors)
• a label to stratify by — the intent or route or category (--label-field)
• a pass/fail field if the data is review-graded (--pass-fail-field; values starting with Pass/Fail)

If the source is a Coval test set whose metadata is packed into a pipe-delimited description (e.g. journey=… | sub_topic=… | next_agent_status=… | sme_result=…), add --parse-coval-description so those become usable labels.

Load references/distillation-method.md if you need help choosing the field mapping or understanding what the script does.

Phase 2: Distill

Run the distiller. It (1) drops rows with no checkable answer, (2) removes exact + paraphrase duplicates, (3) caps boilerplate-convergence clusters (many different asks that all hit one generic fallback/greeting) to a small quota, and (4) selects a stratified, failure-weighted subset across your labels and languages.

python3 scripts/distill.py \
  --source <coval:TEST_SET_ID | path> \
  --parse-coval-description \          # only if labels are in a pipe-delimited description
  --label-field <intent/route field> \
  --pass-fail-field <pass/fail field> \
  --target-size 30 \                   # start small: 10–50
  --min-minority-ratio 0.3 \           # keep ~1/3 of a minority language (e.g. non-English); 0 to disable
  --out distilled.ndjson

The script prints a report to stderr — show it to the user:

dropped_low_info / boilerplate_groups / scenario_rows_after_dedup /
selected / selected_fail / selected_cjk / selected_by_label

• No third-party packages are needed; paraphrase clustering uses a character n-gram heuristic by default.
• For higher-quality clustering on multilingual data, set OPENAI_API_KEY and add --embeddings on (it falls back to the heuristic automatically if anything fails).
• Tuning knobs: --target-size, --fail-weight (default 0.45), --boilerplate-quota (default 4), --jaccard-threshold / --embed-threshold. See references/distillation-method.md.

Phase 3: Review + Adjust

Show the user a sample of the distilled set and the label/pass-fail/language breakdown:

python3 -c "import json;[print('IN :',json.loads(l)['input_str'][:70],'| EXP:',json.loads(l)['expected_output_str'][:60]) for l in open('distilled.ndjson')]"
wc -l distilled.ndjson

Ask: "Does this coverage look right? (yes / re-run with different size or weighting / edit the file)"

• Too many fallback/greeting rows → lower --boilerplate-quota.
• Want more failure coverage → raise --fail-weight or --target-size.
• Want to hand-curate → edit distilled.ndjson directly (one JSON object per line: {"input_str", "expected_output_str", "description"}). Keep every line valid JSON — the bulk loader stops at the first malformed line, so a stray typo can silently drop the rest.
• Sanity-check coherence → confirm each expected_output_str actually answers its input_str. The distiller preserves whatever input/answer pairing your source had, so any misalignment already in the source data carries through (garbage in, garbage out).

Start small. A 20–30 case suite you can run and trust beats a 2,000 case suite you can't. Get the agent passing these, then add a new test set for the next workflow.

Phase 4: Create the Test Set + Bulk-Load (uncapped)

Create a SCENARIO test set and load the distilled cases with --stdin — the uncapped path that loads exactly the rows you chose (no 10-case generation limit):

TS=$(coval test-sets create --name "<Agent> — Representative Suite" --type SCENARIO \
  --description "Distilled from <source>: deduped, failure-weighted representative scenarios" \
  --format json | python3 -c "import json,sys;print(json.load(sys.stdin)['id'])")

cat distilled.ndjson | coval test-cases create --test-set-id "$TS" --stdin

--stdin reads one JSON object per line (input_str required; expected_output_str, description optional) and POSTs one test case per line with no row cap. This is the fix for "the importer only kept ~10 cases".

Note: SCENARIO is the right type for persona-driven eval and is also the CLI default. If an older CLI build rejects --type, just omit it (you still get SCENARIO).

Phase 5: Verify + Next Steps

coval test-cases list --test-set-id "$TS" --page-size 100 --format json | python3 -c "import json,sys;print(len(json.load(sys.stdin)))"

Confirm the count matches the distilled file, then show the app link: https://app.coval.dev/test-sets/<TS>

What's next?

  Create personas to drive these scenarios:   /design-persona  or  /personas-from-artifacts
  Add expected behaviors / refine cases:       /build-test-suite
  Configure evaluation metrics:                /configure-metrics
  Launch an evaluation on the small set first: /quick-eval

  Iterate: once the agent passes this suite, distill a NEW test set for the next workflow
  rather than growing this one — narrow, branch-covering suites beat one giant set.