Browser4 Experience

Progressive Experience Memory (PEM)

The PEM system makes Browser4 progressively smarter: each successfully completed task deposits reusable knowledge so that future tasks — identical, similar, or on similar sites — complete faster with fewer steps.

1. Core Loop

Before task ──▶ experience_query ──▶ Get stored selectors, steps, blockers
    │                                      │
    ▼                                      ▼
Execute task                        P1: Replay directly
    │                               P2: Verify then replay
    ▼                               P3: Hint mode (verify all)
After task  ──▶ experience_save ──▶ P4: Advisory only
                                      P5: Cold start (no knowledge)

Copy-Paste Template

The experience tools are MCP tools called by the agent during browser4-cli agent run. The agent should call them as part of its tool set:

# Before starting a task — the agent calls experience_query to check prior knowledge
# After completing a task — the agent calls experience_save to persist what it learned
browser4-cli agent run "Go to https://amazon.com/dp/test and extract product details"

# To inspect stored knowledge, the agent calls experience_list
browser4-cli agent run "List experience knowledge entries for amazon"

2. Decision Tree

Starting a new task?
├─ experience_query returns P1 (confidence ≥ 0.85)?
│  → Replay stored steps directly. Selectors verified by existence check only.
├─ experience_query returns P2 (confidence 0.60–0.84)?
│  → Use stored selectors as primary candidates. Verify each before use.
├─ experience_query returns P3 (confidence 0.40–0.59)?
│  → Use stored knowledge as hints. Run full discovery for any failed selector.
├─ experience_query returns P4/P5 (confidence < 0.40, or cold start)?
│  → Full discovery mode. Run htmlsnapshot inspect, discover selectors fresh.
│  → Call experience_save after success to bootstrap knowledge.
└─ Always call experience_save after task completion (success or failure).
   → Success path: stores selectors, steps, extraction patterns.
   → Failure path: records negative evidence (what broke, why).

3. Retrieval Tiers

4. Tool Reference

experience_save

Persists a task execution trace to the knowledge store.

Success path: Knowledge promoted with initial confidence 0.50. Subsequent verified successes raise confidence. Failure path: Negative evidence recorded (failure category classified from the trace). Failed selectors are not automatically turned into anti-patterns — record lessons explicitly with facts (e.g. anti_patterns) via experience_save --facts (or the facts argument), or let experience_deep_learn promote knowledge later. Response: the save result includes facts_merged, facts_status, facts_rejected, and facts_message when facts was supplied.

Recording a lesson with facts: a lesson (a selector that broke, a blocker, an anti-pattern) can be recorded immediately after the task — no need to wait for deep_learn:

# MCP tool form
experience_save(url="<target-url>", trace="<execution trace JSON>", outcome="success",
                intent="extract product details", task_type="extract_product_list",
                facts='{"interaction_hints":["open the price popover before reading"],
                        "anti_patterns":["clicking the thumbnail before the modal loads"]}')

# CLI equivalent — trace is inline JSON; --facts accepts inline JSON or @file.json
browser4-cli experience save "https://example.com/products" '<trace-json>' --facts @lessons.json

experience_query

Queries stored knowledge before starting a task.

Returns: JSON with tier, confidence, primary_selectors, extraction_query, known_blockers, warnings, steps.

experience_list

Lists stored knowledge entries (diagnostic/debug tool).

5. Critical Warnings

Warning: Phase 1 (MVP) requires the agent to explicitly call experience_save after task completion. The automatic engine hook (onTaskComplete) is Phase 2+. Forgetting to save means knowledge is lost.

Warning: experience_query before open_session is supported — it operates on the file system, not the browser. Use it to plan your task before launching Chrome.

Warning: Knowledge stored for one URL pattern (e.g., /dp/*) is not automatically available for a different pattern (e.g., /s?k=*). The query matches by URL pattern specificity.

Note: The knowledge store is file-backed YAML under knowledge/, resolved relative to the backend process working directory (there is no knowledge.dir config option to relocate it). The store is safe to version with git. Raw traces (under knowledge/traces/<domain>/) are ephemeral (30-day TTL) and not versioned; facts entries (knowledge/facts/<domain>/<intent>.yaml) are immutable once VERIFIED.

6. Knowledge Store Layout

The store is file-level YAML per (domain, intent) — no per-site blob files:

knowledge/                          ← root: relative to the backend process CWD
├── traces/<domain>/                ← TraceRecords (immutable, 30-day TTL)
├── experience/<domain>/            ← ExperienceStats (mutable; confidence source)
└── facts/<domain>/                 ← KnowledgeFacts — one <intent>.yaml per (domain, intent)
                                      (VERIFIED entries are immutable; merge is refused)

7. Reference Map

• Design document — Full architecture and implementation guide
• Proposal (v2) — 2300-line technical design
• CLAUDE.md — Project context and conventions