## Purpose

Provide a repeatable MVP demo flow that can run a chat diagnosis, expose its persisted execution trace, and submit feedback for the same diagnosis run.
## Requirements
### Requirement: Diagnosis trace can be queried by session id
The system SHALL expose a read-only HTTP endpoint `GET /api/diagnosis/{sessionId}/trace` that returns the persisted diagnosis trace for the requested session id. When `runId` is omitted, the endpoint SHALL return the latest diagnosis run for compatibility. When `runId` is provided, the endpoint SHALL return that exact run after validating it belongs to the path `sessionId`.

#### Scenario: Existing session latest trace is returned
- **WHEN** a caller requests trace data for a session id that has at least one `diagnosis_run`
- **THEN** the system returns a success response containing the resolved run id, session summary, run summary, ordered agent steps, ordered tool invocations, self-evaluation data, final answer, and feedback for the latest run

#### Scenario: Existing session exact trace is returned
- **WHEN** a caller requests trace data with `GET /api/diagnosis/{sessionId}/trace?runId=run-xxx`
- **THEN** the system validates that `runId` belongs to `sessionId`
- **AND** it returns a success response containing only the trace data for that run

#### Scenario: Missing session returns not found
- **WHEN** a caller requests trace data for a session id that does not exist in `chat_session`, `diagnosis_run`, or historical compatibility data
- **THEN** the system returns a 404 response using the existing session-not-found error contract

### Requirement: Trace aggregation is read-only
The system MUST build trace output from existing persisted diagnosis tables and MUST NOT mutate chat sessions, diagnosis runs, agent steps, tool invocations, feedback, or chat session state while serving the trace request.

#### Scenario: Trace query does not change persisted state
- **WHEN** a caller requests `GET /api/diagnosis/{sessionId}/trace`
- **THEN** the system reads `diagnosis_run`, `agent_step`, and `tool_invocation` records and returns an aggregate without saving any of those records

#### Scenario: Exact trace query does not change persisted state
- **WHEN** a caller requests `GET /api/diagnosis/{sessionId}/trace?runId=run-xxx`
- **THEN** the system reads the specified run and its trace detail records without saving any of those records

### Requirement: MVP demo profile is available
The system SHALL provide an `mvp-demo` Spring profile that documents the demo runtime intent and keeps mock log and metric providers enabled for repeatable diagnosis demonstrations.

#### Scenario: Demo profile loads mock evidence providers
- **WHEN** the application starts with `--spring.profiles.active=mvp-demo`
- **THEN** `prometheus.mock-enabled` and `cls.mock-enabled` are enabled by profile configuration

### Requirement: End-to-end MVP acceptance case is documented
The project SHALL include an end-to-end acceptance case that demonstrates start-up, chat diagnosis, trace query, and feedback submission using the same `sessionId + runId`.

#### Scenario: Reviewer follows the acceptance case
- **WHEN** a reviewer follows the documented MVP demo acceptance steps
- **THEN** they can run the application, submit a diagnosis question, query the exact trace endpoint, and submit feedback for the same run

### Requirement: MVP demo SHALL provide an interview runbook
The MVP demo SHALL include a concise interview runbook that explains how to demonstrate the Agent flow and how to narrate the engineering value.

#### Scenario: Walkthrough explains the demo story
- **WHEN** a developer opens the interview walkthrough
- **THEN** it SHALL explain the user question, Agent flow, evidence tools, verifier judgment, trace API, feedback, and eval baseline connection

#### Scenario: Walkthrough stays scoped to existing capabilities
- **WHEN** the walkthrough describes the demo
- **THEN** it SHALL avoid claiming unsupported runtime behavior or new production features

### Requirement: MVP demo SHALL provide executable local demo scripts
The MVP demo SHALL provide scripts and request payloads for running the payment-timeout case through existing local APIs.

#### Scenario: Demo script sends the fixed diagnosis request
- **WHEN** the demo script is executed against a running local service
- **THEN** it SHALL send the fixed payment-timeout chat request with a stable session id
- **AND** it SHALL read the returned run id for exact trace and feedback calls

#### Scenario: Demo script captures review artifacts
- **WHEN** the demo script finishes successfully
- **THEN** it SHALL write chat, exact trace, and feedback responses under a demo output directory

### Requirement: MVP demo SHALL be reproducible for interviews
The MVP demo SHALL provide a repeatable way to show a diagnosis answer, trace, verifier evaluation, and feedback.

#### Scenario: interview demo check script records an evidence bundle
- **WHEN** the user runs the interview demo check script against a running `mvp-demo` service
- **THEN** the script SHALL submit a fixed Chat diagnosis request
- **AND** it SHALL fetch the trace for the same `sessionId + runId`
- **AND** it SHALL submit useful feedback for that run
- **AND** it SHALL write chat, trace, feedback, and summary outputs under `mvp/demo/output/`

#### Scenario: interview demo check fails with actionable readiness output
- **WHEN** the target service is not reachable
- **THEN** the script SHALL fail before issuing diagnosis requests
- **AND** the failure message SHALL name the base URL and the expected startup profile

#### Scenario: interview documentation explains audit fields
- **WHEN** an interviewer asks how prompt or Gatekeeper changes are audited
- **THEN** the demo documentation SHALL point to `prompt_audit.version` and `gatekeeper_result.rule_set_version`
- **AND** it SHALL explain that deterministic eval fixtures are the regression source of truth

### Requirement: MVP demo SHALL provide a trace inspection checklist
The MVP demo SHALL document which trace fields to inspect for evidence, verifier behavior, and run-level auditability.

#### Scenario: Checklist maps fields to interview claims
- **WHEN** a developer reviews a trace response
- **THEN** the checklist SHALL map concrete JSON paths to the claims made in the interview walkthrough

### Requirement: MVP demo SHALL provide a browser trace workbench
The MVP demo SHALL provide a browser-accessible static page for inspecting one
diagnosis trace by session id and optional run id using the existing read-only Trace API.

#### Scenario: Existing trace renders in the workbench
- **WHEN** a reviewer opens the Trace workbench with a session id that exists
- **THEN** the page SHALL request `GET /api/diagnosis/{sessionId}/trace`
- **AND** it SHALL render session summary, ordered agent steps, ordered tool
  invocations, verifier evaluation, and final answer when present

#### Scenario: Exact trace renders in the workbench
- **WHEN** a reviewer opens the Trace workbench with `?sessionId=...&runId=...`
- **THEN** the page SHALL request `GET /api/diagnosis/{sessionId}/trace?runId=...`
- **AND** it SHALL render only that run's trace data

#### Scenario: Trace workbench handles missing or failed traces
- **WHEN** the Trace API returns an error or the session id is empty
- **THEN** the page SHALL show a clear error or empty state without mutating any
  diagnosis data

### Requirement: Trace workbench SHALL expose evidence and skill boundaries
The Trace workbench SHALL make tool evidence and skill-loading boundaries visible
without requiring raw JSON inspection first.

#### Scenario: Tool and verifier evidence are inspectable
- **WHEN** a trace includes tool invocations and verifier facts
- **THEN** the page SHALL show tool invocation counts, success status, tool
  filters, verifier facts, and evidence references

#### Scenario: RAG details are inspectable for lookup knowledge calls
- **WHEN** a `lookup_knowledge` invocation includes retrieval details
- **THEN** the page SHALL show query transform, retrieval trace, context pack,
  rerank trace, and evidence block data where available

#### Scenario: Skill boundary checks are visible
- **WHEN** a trace includes planner, executor, or verifier steps
- **THEN** the page SHALL show best-effort indicators for selected skill,
  planner `read_skill` text mentions, executor `read_skill` text mentions, and
  verifier `read_skill` text mentions

### Requirement: MVP demo SHALL provide stable evidence-pipeline scenarios
The MVP demo SHALL provide stable scenarios that explain how to demonstrate positive evidence, no-evidence, and safety/reject behavior for an Agent engineering interview.

#### Scenario: Scenario guide maps demo inputs to evidence claims
- **WHEN** a reviewer opens the demo scenario guide
- **THEN** it SHALL list the supported positive, no-evidence, and safety/reject scenarios
- **AND** it SHALL map each scenario to a request payload or fixture id
- **AND** it SHALL describe the expected Gatekeeper, Verifier, Composer, and trace fields to inspect

#### Scenario: Live and fixture-backed scenarios are distinguished
- **WHEN** a demo scenario is fixture-backed rather than live-scripted
- **THEN** the documentation SHALL say so explicitly
- **AND** it SHALL avoid promising deterministic live LLM output for that scenario