Verify jlens-qwen36 changes

Launch the server

JLENS_PATH=data/lens/qwen36_27b_neuronpedia_n1000.npz \
  uv run python -m uvicorn jlens_qwen.serve:app --host 127.0.0.1 --port 8765

Poll GET /api/lens until it answers and confirm "n_prompts": 1000 before interpreting any result (project rule; startup takes ~30–60 s).

Drive the UI headlessly

The repo has no Node dependency tree. The Playwright MCP server needs Google Chrome, which is not installed — use a Node driver with a cached Chromium instead, following scripts/e2e_intervention_playwright.cjs:

# Find a usable playwright install (npx cache works):
for d in ~/.npm/_npx/*/node_modules; do [ -d "$d/playwright" ] && echo "$d"; done
# Pick one whose chromium exists:
NODE_PATH=<dir> node -e "console.log(require('playwright').chromium.executablePath())"

NODE_PATH=<dir> node your-driver.cjs   # chromium.launch({ headless: true })

Driver facts that hold for web/index.html (single classic script):

• Top-level bindings (state, _wish, $, addIntervention, rerunWithInterventions, setActiveVariant, …) are reachable from page.evaluate even when declared with let/const.
• Send a chat turn: click #chat-editor, type, press Enter; then poll !state.streaming && state.messages.at(-1).tokens.length > 0. One short turn takes ~60–90 s (27B model + per-token lens readouts).
• Backward-search (wish) flow: click a reply token (#chat-log .tok, e.g. hasText 'Paris'), fill #wish-input, press Enter. Search requests go to /api/intervention_search_adaptive; candidate replays advance roughly one per second.
• A real intervened A/B rerun: addIntervention({... mode: 'swap', token: ' Paris', target: ' Beijing', alpha: 1, layers: [52], scope: { type: 'at', pos: firstGeneratedPos() - 1 } ...}) then rerunWithInterventions(). The server resolves token text to ids.

Flows worth driving

• Clean baseline chat → wish search starts (progress track, stats, pause button, recipes pill "N tested · search running").
• Dirty baseline (applied or enabled interventions) → wish refusal modal, no search state, no /api/intervention_search_adaptive POST.
• A/B compare: variant toggle labels (Baseline/Run A + config label), switching variants with setActiveVariant(false|true).

Gotchas

• Check the uvicorn log for exactly the requests you expect; refusals and client-side guards send nothing.
• state.appliedInterventions is frozen per run; only a fresh clean run, clearState(), or switching to a clean variant empties it.