# L1 AI Decision-Tree Builder — Phase 2A Design

**Status:** Draft for review
**Date:** 2026-05-29
**Author:** previous session (brainstorming)
**Predecessor:** [`2026-05-28-l1-workspace-design.md`](2026-05-28-l1-workspace-design.md) (full L1 vision), [`2026-05-28-l1-workspace-phase-1-acceptance.md`](2026-05-28-l1-workspace-phase-1-acceptance.md) (what shipped in Phase 1)

---

## 1. Goal

When an L1 tech describes a problem and there is **no matching authored flow or AI draft**, the platform builds a yes/no decision tree **in real time from the model's general L1 knowledge** and walks the tech through it node by node. Scoped to L1-appropriate troubleshooting: simple yes/no questions and reversible step-by-step instructions. Successful trees are captured as outcome-validated drafts for engineer review, compounding the account's knowledge base from real resolutions.

This **overrides** the original spec's "no empty-KB build" rule (§8.1 of the predecessor), which aborted to a degradation screen when no KB existed. Instead of aborting, we build from generic knowledge under a layered safety model.

KB grounding (RAG over ingested documents) is **explicitly deferred to Phase 2B** — Phase 2A builds from generic knowledge only, plus matching against already-authored flows.

## 2. Scope

**In scope (Phase 2A):**
- `match_or_build` orchestrator inserted at L1 intake (match-first, build-on-miss).
- `ai_tree_builder` service: node-by-node ("streaming") tree generation, constrained + escalate-early.
- Admin-configurable L1 category allowlist (Account Owner/Admin control panel).
- Standing AI-disclaimer banner on AI-built walks.
- Flywheel capture: resolved AI trees become outcome-validated `FlowProposal`s.
- Minimum escalation handoff: engineer bell-badge notification + an engineer-visible "escalated from L1" surface.

**Deferred:**
- KB document ingestion + connectors (IT Glue, Hudu, SharePoint/OneDrive) — Phase 2B.
- RAG grounding of the builder on ingested KB — Phase 2B.
- PSA ticket reassign on escalation, escalation-package generation, AI chat handoff — later phase.
- `BuildAbortedNoKB` screen from the original spec — **dropped** (superseded by build-from-generic).

## 3. Architecture (Approach C)

Dedicated builder for the constrained node generation; reuse existing rails for matching and capture.

**New services:**
| File | Responsibility |
|---|---|
| `backend/app/services/match_or_build.py` | Orchestrator. `match_or_build(account_id, problem_text, ticket_ref, *, force_build=False) -> MatchOrBuildResult`. Classify → category gate → match pass → build/suggest/out-of-scope decision. |
| `backend/app/services/ai_tree_builder.py` | Node-by-node generation. `generate_next_node(problem_text, category, walked_path) -> TreeNode`. Reuses `get_ai_provider` + `generate_json` + `parse_llm_json`. Owns the constrained system prompt and per-node validation. |
| `backend/app/services/l1_category_service.py` | Read/write an account's enabled L1 categories; expose the default allowlist and the always-forbidden hard floor. |

**Reused as-is:**
- `flow_matching_engine.find_matches()` — semantic + keyword + recency match pass.
- `knowledge_flywheel` proposal-creation + dedupe (`_find_similar_pending_proposal`) — outcome-validated capture.
- `notification_service` — engineer escalation notification.
- Phase 1 `L1WalkTreeVariant` walker — its stubbed synthetic-step UI is replaced by real AI node rendering.

**Intake decision flow:**

Order matters: **match first, gate only the build path.** The category allowlist exists to bound *generic AI building* for safety — it must not block a human-authored flow that already exists for that problem. So matching against published flows runs before any category check; the category gate applies only when we fall through to building.

```
POST /l1/intake (problem_statement, customer_*, force_build?)
  → match_or_build(account_id, problem_text, problem_domain, ticket_ref, force_build):
      1. if not force_build:
             hits = flow_matching_engine.find_matches(problem_text, problem_domain, account_id)
             best = max(hits, default=None)                       # published flows (Trees) only
             if best and best.score >= MATCH_THRESHOLD:
                 return {outcome: 'matched', flow_id, session_kind: 'flow'}
             if best and best.score >= SUGGEST_THRESHOLD:
                 return {outcome: 'suggest', near_miss, can_build: true}
      2. category = classify(problem_text)                        # new — only on build path
      3. if category not in account.enabled_l1_categories:
             return {outcome: 'out_of_scope', category}
      4. return {outcome: 'build', session_kind: 'ai_build', category}
```

**Match scope (Finding 2):** `flow_matching_engine.find_matches()` matches **published flows (`trees`) only** — it returns `{tree_id, tree_name, score, ...}` and has no notion of `FlowProposal`s. Phase 2A therefore matches against published flows only; the `matched` outcome is always `session_kind: 'flow'`. This is sufficient because the flywheel promotes good AI drafts to published flows (§6), which then become matchable on future intakes. Matching against not-yet-promoted proposals is a deferred enhancement (would require extending the engine), noted in §13.

Frontend dispatches on `outcome`:
- `matched` → start a `flow` walk (Phase 1 path).
- `suggest` → inline prompt ("Found a similar flow — use it, or build new?"); "Build new" re-calls intake with `force_build=true` (which skips the match pass and runs the category gate before building).
- `out_of_scope` → inline prompt offering ad-hoc walk or escalate-without-walk (Phase 1 paths).
- `build` → create an `ai_build` session, navigate to the walker, fetch the first node.

## 4. The streaming build & node schema

`ai_tree_builder.generate_next_node()` is called with the problem statement, the resolved category, and the **full walked path so far**. It returns exactly one node. Passing the whole path every call is what keeps independently-generated nodes coherent and lets the model decide when it has exhausted safe steps.

**Node shape (`proposed_flow_data` node, also the live `walked_path` entry):**
```json
// question — yes/no branch; both branches regenerate
{ "node_type": "question", "id": "n3", "text": "Is the printer showing a 'ready' status light?",
  "yes_next": "generate", "no_next": "generate" }

// instruction — a single safe, reversible action; advances on acknowledgement
{ "node_type": "instruction", "id": "n4", "text": "Unplug the printer for 30 seconds, then power it back on.",
  "next": "generate" }

// resolved — terminal success
{ "node_type": "resolved", "id": "n7", "text": "Printer is back online and printing test pages." }

// escalate — terminal handoff (escalate-early safety valve)
{ "node_type": "escalate", "id": "n7", "reason_category": "exhausted_safe_steps",
  "text": "This looks like a driver-level fault beyond L1 scope — escalating to engineering." }
```

`"generate"` is a sentinel meaning "call `generate_next_node` again with the new answer appended." The first node is fetched synchronously on `ai_build` session creation (intake). Each subsequent node is fetched when the tech answers/acknowledges — target latency ~2–4s per node; show a per-node "Thinking through the next step…" affordance.

**Endpoint:** `POST /l1/sessions/{id}/next-node` body `{node_id, answer?: 'yes'|'no', acknowledged?: true, note?}`. Appends the answered node to `walked_path`, then generates and returns the next node (or a terminal node). Replaces the Phase 1 synthetic stepping in `L1WalkTreeVariant`.

## 5. Safety model (layered)

**Layer 1 — classification gate (build path only).** Runs only after the match pass misses (§3) — a human-authored flow is never blocked by category settings. `classify(problem_text)` maps the problem to a category via a lightweight model call (low token budget, returns one category key from the enabled set or `unknown`); on model failure it falls back to keyword matching against category aliases. If the result is not in the account's enabled set (or is `unknown`), intake returns `out_of_scope` (offer adhoc/escalate); no build happens.

**Layer 2 — constrained generation.** The `ai_tree_builder` system prompt restricts output to:
- Safe, reversible, observe-or-restart-class steps only (toggle/restart/reconnect/re-enter, check-status questions).
- A **hard floor of always-forbidden actions** (see §5.1) that NO category may unlock.
- An explicit instruction to emit an `escalate` node — never guess — once it runs out of in-scope safe steps.

**Layer 3 — per-node validation.** Server-side, every generated node is checked before being returned:
- Reject (and regenerate once, then escalate) nodes whose text matches forbidden-action patterns (§5.1).
- Enforce a **depth cap** (default `L1_BUILD_MAX_DEPTH = 12`): once the walked path hits the cap, force an `escalate` node.
- Validate node JSON shape (Pydantic); malformed → regenerate once, then escalate.

**Layer 4 — standing disclaimer.** Persistent banner on every `ai_build` walk:

> *"These are high-confidence troubleshooting steps, but they come from outside your organization's knowledge base — review them before acting. When in doubt, escalate early."*

### 5.1 Hard floor — always forbidden (admins cannot enable)
Regardless of enabled categories, the builder must never produce steps that:
- Modify the Windows registry, system files, or boot configuration.
- Delete, format, or repartition data/disks; remove user profiles or mailboxes.
- Change credentials, MFA, security/firewall/AV settings, or disable protections.
- Run scripts/commands with elevated/admin privileges.
- Touch domain controllers, DNS, DHCP, or production server config.
- Make purchases, license changes, or anything with billing impact.

*(This list is a product decision — review and edit during spec review.)*

### 5.2 Default enabled category allowlist (admin-editable)
Ships enabled by default; Account Owners/Admins toggle per account:
`password_reset`, `account_lockout`, `printer`, `email_outlook_client`, `wifi_network_basics`, `vpn_connect`, `teams_zoom_av`, `browser_cache_cookies`, `peripheral_reconnect`, `os_restart_update`.

*(This list is a product decision — review and edit during spec review.)*

### 5.3 Tunables
| Setting | Default | Notes |
|---|---|---|
| `MATCH_THRESHOLD` | 0.75 | Carried from predecessor spec §8.1. |
| `SUGGEST_THRESHOLD` | 0.60 | Carried from predecessor spec §8.1. |
| `L1_BUILD_MAX_DEPTH` | 12 | Force escalate beyond this many nodes. |
| `get_model_for_action('l1_realtime_build')` | Sonnet | Latency-sensitive; benchmark Sonnet vs Opus during plan. |
| Per-node max_tokens | 1024 | One node is small. |

## 6. Flywheel capture

On `resolve` of an `ai_build` session (`l1_session_service.resolve` extension):
1. **Normalize** the `walked_path` into a complete, valid `tree_structure` (§6.1) — approval requires a dict with a real `id` (see Finding 5 / `_create_tree_from_proposal`).
2. Create a `FlowProposal`: `source='ai_realtime_l1'`, `validated_by_outcome=true`, `proposed_flow_data={tree_structure, match_keywords}`, `l1_session_id=<this session>` (NOT `source_session_id` — see §6.2 / Finding 1), `linked_ticket_id/kind=<session ticket>`, `problem_domain=<category>`, `status='pending'`.
3. Run the existing `_find_similar_pending_proposal` dedupe — merge (bump supporting count) if a near-duplicate pending proposal exists, else insert.
4. Emit the existing `proposal.pending` notification to the review queue.

Engineers promote good proposals to authored flows in the existing review queue. Promoted flows are then found by `flow_matching_engine` on future intakes → the KB compounds. `source='ai_realtime_l1'` rows surface in the existing queue (badge them "AI · outcome-validated").

### 6.1 Tree normalization (Finding 5)
The live `walked_path` holds only traversed nodes, and `"generate"` is a runtime sentinel, not a real edge — that is not a valid tree and would fail the `_create_tree_from_proposal` guard (`tree_structure` must be a dict with an `id`). At resolve time, `ai_tree_builder.normalize_walked_path(walked_path) -> tree_structure` produces a complete object:
- Assign stable string `id`s to every node; the first node becomes the root and `tree_structure.id` = root id.
- `question` nodes: the **traversed** branch (`yes`/`no` the tech actually chose) points to the next traversed node; the **untraversed** branch points to a terminal `{node_type: 'needs_review', text: 'Branch not explored during the originating call'}` stub.
- `instruction` nodes point to the next traversed node.
- The traversal ends at the real terminal node (`resolved` or `escalate`).
This yields a structurally valid, reviewable tree: engineers fill in the `needs_review` branches when promoting. (Trees are `tree_type='troubleshooting'`.)

### 6.2 FlowProposal L1 source linkage (Finding 1 — Blocker)
`FlowProposal.source_session_id` is currently `nullable=False` FK → `ai_sessions`, and the review UI (`ProposalDetail.tsx`) links the "Source Session" to `/pilot/{source_session_id}` (a FlowPilot chat surface). An L1 `ai_build` session is an `l1_walk_session`, not an `ai_session`, so it cannot populate `source_session_id`. Changes:
- **Model/migration:** add `FlowProposal.l1_session_id` (nullable FK → `l1_walk_sessions.id`, `ondelete=SET NULL`, indexed). Make `source_session_id` **nullable**. Add CHECK `((source_session_id IS NOT NULL) <> (l1_session_id IS NOT NULL))` — exactly one source set.
- **Review UI:** when `l1_session_id` is set (source `ai_realtime_l1`), render the "Source" block as a read-only walked-path summary (problem statement + the resolved path) instead of a `/pilot/...` link. Existing ai_session-sourced proposals are unchanged.
- **Tree promotion:** `_create_tree_from_proposal` sets `Tree.source_session_id` from the proposal — for L1-sourced proposals leave it NULL (confirm `Tree.source_session_id` is nullable; if not, include in the migration).

## 7. Minimum escalation handoff

On `escalate` (terminal node reached, or the L1 hits the Escalate modal during an `ai_build` walk) — extends `l1_session_service.escalate`. **The engineer-visible surface is the primary, dependency-free handoff; the bell-badge notification is a thin addition that requires three specific extensions to the FlowPilot-shaped notification system (Finding 3).**

1. **Engineer-visible surface (primary).** Escalated L1 sessions appear in an engineer-facing list — extend the existing `/escalations` queue (`EscalationQueuePage`) with an "L1 escalations" section, backed by a new `GET /l1/escalations`. Each row: problem statement, walked-path summary, who escalated, when, reason category. Pollable; no dependency on the notification subsystem.

2. **Bell-badge notification (Finding 3 — three explicit changes).** The notification system is currently FlowPilot-specific:
   - `VALID_EVENTS` (`backend/app/schemas/notification.py`) has no `l1.session.escalated`. **Add it** to the set (and to the default `events_enabled` map).
   - `_build_notification_link` (`notification_service.py`) only knows `session.escalated → /pilot/{session_id}?pickup=true`. **Add** `l1.session.escalated → /escalations` and **add** a body template for the new event. The existing `session.escalated` event must NOT be reused — an L1 escalation has no ai_session and no `/pilot` pickup flow.
   - Default recipients (`_resolve_recipients`, ~line 184) are owner/admin/team_admin only — ordinary **engineers are excluded**. Since L1 escalations must reach engineers who can pick them up, the call **must pass explicit `target_user_ids`** = the account's active `engineer`-role users (plus owner/admin), not rely on the default set.

**Still deferred** (documented, not built): PSA ticket reassign, escalation-package markdown generation, AI chat handoff/session creation.

## 8. Data model & migrations

**Migration 1 — `ai_build` session kind.**
- Extend `l1_walk_sessions` `ck_l1_walk_sessions_session_kind` CHECK to include `'ai_build'`.
- Extend `ck_l1_walk_sessions_target_consistency`: for `ai_build`, both `flow_id` and `flow_proposal_id` are NULL (same as `adhoc`).

**Migration 2 — account L1 category settings.**
- Add `accounts.enabled_l1_categories` `JSONB NOT NULL DEFAULT '<default allowlist>'::jsonb` (list of category keys). RLS already covers `accounts`.

**Migration 3 — FlowProposal L1 source linkage (Finding 1).**
- Add `flow_proposals.l1_session_id` nullable FK → `l1_walk_sessions.id` (`ondelete=SET NULL`, indexed).
- Make `flow_proposals.source_session_id` **nullable** (was `NOT NULL`).
- Add CHECK `((source_session_id IS NOT NULL) <> (l1_session_id IS NOT NULL))` — exactly one source.
- Confirm `trees.source_session_id` is nullable (L1-promoted trees leave it NULL); if not, drop its NOT NULL here.

No new tables — live build state rides on the existing `l1_walk_sessions.walked_path`; persisted trees ride on `FlowProposal.proposed_flow_data`.

## 9. API surface

| Method | Path | Notes | Auth |
|---|---|---|---|
| POST | `/l1/intake` | **Extended**: now runs `match_or_build`; response carries `outcome` (`matched`/`suggest`/`out_of_scope`/`build`). | `require_l1_or_coverage` |
| POST | `/l1/sessions/{id}/next-node` | **New**: record answer/ack on current node, generate + return next node (or terminal). | `require_l1_or_coverage` |
| GET | `/accounts/me/l1-categories` | **New**: list enabled + available categories + hard-floor (read-only) list. | `require_l1_or_above` (read) |
| PATCH | `/accounts/me/l1-categories` | **New**: set enabled categories. | `require_account_owner_or_admin` (Finding 6) |
| GET | `/l1/escalations` | **New** (or extend `/escalations`): engineer-visible escalated-from-L1 list. | `require_engineer_or_admin` |

**Finding 6 — new auth dep.** The category control is an owner/admin setting, but `require_engineer_or_admin` also admits `engineer`. No existing dep matches "owner or account-admin" (`require_account_owner` is owner-only; `require_admin` is super-admin-only). Add `require_account_owner_or_admin` to `deps.py`: allow `super_admin` bypass, then `account_role in ('owner', 'admin')`, else 403. Use it for the PATCH.

## 10. Frontend

- `L1WalkTreeVariant` — replace synthetic stepping with real node rendering driven by `/next-node`; render `question` (yes/no), `instruction` (acknowledge), `resolved`/`escalate` (terminal). Per-node loading affordance. Disclaimer banner mounted for `ai_build` sessions.
- `L1Dashboard` intake handler — dispatch on `match_or_build` `outcome` (suggest prompt, out-of-scope prompt, build → walker).
- New admin settings panel (under `/account`) — toggle enabled L1 categories; show hard-floor list as read-only "always excluded."
- Engineer escalations surface — "L1 escalations" section/list.

## 11. Testing strategy

**Backend unit:**
- `ai_tree_builder.generate_next_node` — returns valid node per type; escalate-early when path is deep / model signals exhaustion; regenerate-then-escalate on malformed/forbidden output; depth cap forces escalate.
- Per-node validation — forbidden-action patterns rejected; hard-floor enforced even if a category is enabled.
- `match_or_build` — all four outcomes at threshold boundaries (`score == MATCH_THRESHOLD`, `== SUGGEST_THRESHOLD`); **match runs before the category gate** (a matched published flow is returned even when its category is disabled — Finding 4); `force_build` skips match but still applies the category gate; `out_of_scope` only on the build path when category disabled/unknown.
- `classify` — known categories map correctly; unknown → out_of_scope.
- `normalize_walked_path` (Finding 5) — produces a dict with a root `id`; untraversed `question` branches become `needs_review` stubs; output passes the `_create_tree_from_proposal` validity guard.
- Flywheel capture — resolve creates `ai_realtime_l1` proposal with `l1_session_id` set and `source_session_id` NULL (Finding 1); CHECK accepts exactly-one-source; dedupe merges near-duplicate.
- Escalation handoff — `l1.session.escalated` accepted by the notification schema (Finding 3); link resolves to `/escalations`; explicit engineer `target_user_ids` receive it; escalated session appears in `GET /l1/escalations`.

**Backend integration:**
- Full intake→build→resolve creates an outcome-validated proposal.
- Intake→build→escalate notifies engineers and surfaces in the escalations list.
- Migrations roundtrip; `ai_build` CHECK + target-consistency hold.

**Frontend e2e (extend `l1-workspace.spec.ts`):**
- L1 intake with no match → AI build → answer nodes → resolve → proposal created.
- L1 build → escalate node → escalate handoff.
- Admin toggles a category off → that problem class returns out-of-scope.

**AI quality (plan-time):** small eval set of common L1 problems; assert trees stay in-scope, reach resolution or escalate cleanly, never emit hard-floor actions. Benchmark Sonnet vs Opus for the model-tier decision.

## 12. Risks & open questions

- **Hallucinated-but-plausible steps** for niche/company-specific apps. Mitigation: classification gate + constrained prompt + escalate-early + disclaimer. Residual risk accepted for v1; eval set bounds it.
- **Latency on a live call.** Node-by-node means ~2–4s per branch. Mitigation: Sonnet, small per-node token budget, clear loading affordance. Benchmark at plan time.
- **Coherence across independently-generated nodes.** Mitigation: full walked-path context every call.
- **Classification accuracy.** A misclassify could wrongly gate a valid problem out, or let a borderline one through. Mitigation: hard floor is category-independent; out-of-scope still offers adhoc/escalate (no dead end).
- **Open (product, for spec review):** the default category allowlist (§5.2) and the hard-floor list (§5.1) — confirm/edit. Model tier — confirm Sonnet pending benchmark.

## 13. Out of scope (restated)
KB ingestion + connectors, RAG grounding, PSA reassign, escalation-package generation, AI chat handoff. Each is its own later phase with its own spec.

**Also deferred (surfaced in review):**
- **Matching against unpromoted `FlowProposal`s** (Finding 2). `flow_matching_engine` matches published flows only. Extending it to also surface outcome-validated drafts before promotion is a later enhancement; Phase 2A relies on engineer promotion (draft → published flow → matchable).

## 14. Review revisions (2026-05-29 Codex review)
All six findings verified against code and resolved in this spec:
1. **Blocker — FlowProposal source linkage:** §6.2 + §8 Migration 3 (new nullable `l1_session_id`, `source_session_id` made nullable, exactly-one CHECK, review-UI link change).
2. **High — match scope:** §3 (match published flows only; proposal-matching deferred §13).
3. **High — escalation notification:** §7 (engineer surface is primary; three explicit notification-system changes enumerated).
4. **Medium — gate ordering:** §3 + §5 Layer 1 (match first; category gate only on the build path).
5. **Medium — flywheel tree shape:** §6.1 (`normalize_walked_path` produces a valid tree with root `id`; unexplored branches → `needs_review` stubs).
6. **Medium — category write auth:** §9 (new `require_account_owner_or_admin` dep; `require_engineer_or_admin` was too broad).