# Backend Agentic Service API Contract

**Last updated**: 2026-07-14

This document describes the Python agentic backend used by the frontend for AI chat, help/report tools, charts, and traceability data shown alongside chat answers.

Base path examples use relative URLs. Configure the frontend with the deployed Python service base URL.

## Overview

The Python backend owns the generative AI interaction surface:

1. Stream chat answers from the AI agent.
2. Execute tool-style actions for help and report generation.
3. Return report versions, report details, and report-readiness signals.
4. Return traceability for a completed assistant answer.
5. Return chart specifications produced for a completed assistant answer.

The frontend uses this service during the analysis conversation flow:

1. User sends a chat message.
2. Frontend calls `POST /api/v2/chat/stream` and renders the streamed answer.
3. When the stream emits `done`, frontend uses the returned `message_id` as the assistant answer correlation id.
4. Frontend calls `GET /api/v1/traceability` for planning, tool calls, and source provenance.
5. Frontend calls `GET /api/v1/charts` with the same `message_id` and renders any returned charts under the answer.
6. Frontend calls `/api/v1/tools/help` for guided help and `/api/v1/tools/report` for report generation (the Generate-Report button; `GET …/readiness` drives the button state).

## Endpoint Summary

| Method | Path | Purpose |
| --- | --- | --- |
| `POST` | `/api/v2/chat/stream` | Stream an AI chat answer for one analysis conversation. |
| `GET` | `/api/v1/tools/list` | List available frontend tools. |
| `POST` | `/api/v1/tools/help` | Stream contextual help for the current analysis conversation. |
| `POST` | `/api/v1/tools/report` | Generate and persist a new report version. |
| `GET` | `/api/v1/tools/report/{analysis_id}` | List report versions for an analysis. |
| `GET` | `/api/v1/tools/report/{analysis_id}/records` | List analysis records for report curation. |
| `GET` | `/api/v1/tools/report/{analysis_id}/readiness` | Report-readiness signal for the Generate-Report button. |
| `GET` | `/api/v1/tools/report/{analysis_id}/{version}` | Retrieve one report version. |
| `GET` | `/api/v1/traceability` | Retrieve provenance for one assistant answer. |
| `GET` | `/api/v1/charts` | Retrieve chart(s) produced for one assistant answer. |

## Common Concepts

### Identifiers

- `user_id`: user identifier passed by the frontend.
- `analysis_id`: analysis conversation identifier.
- `message_id`: assistant answer identifier generated by Python and returned in the stream `done` event; used to correlate chat streaming, Golang message persistence, traceability, and charts. It is a UUID string (e.g. `77f06761-0fdf-4cc5-84f8-5f81bcbb6f84`); the `msg_…` values in the examples below are illustrative placeholders only. Never generate or send it from the frontend.

### Server-Sent Events

Chat and help endpoints return `text/event-stream`.

Frontend should parse events by `event` name and `data` payload. Blank lines separate SSE events.

Common event types:

| Event | Data | Meaning |
| --- | --- | --- |
| `sources` | JSON array | Always `[]` — real sources moved to `GET /api/v1/traceability`. Event kept for backward compatibility. |
| `status` | text | Optional progress update for slower paths. |
| `chunk` | text | Answer text fragment. Concatenate chunks in order. |
| `done` | JSON object | Terminal success event. Includes `message_id`. |
| `error` | text | Terminal error event. Stream stops after this. |

The stream carries answer text only. Planning, tool call details, and full provenance are fetched from `GET /api/v1/traceability` after the stream is done; charts are fetched from `GET /api/v1/charts`. The `done` event carries no chart hint — fetch `GET /api/v1/charts` unconditionally on every `done` (the response tells you if there is nothing to render).

## Chat

### `POST /api/v2/chat/stream`

Streams an AI answer for one user message in an analysis conversation. The frontend must not generate or send `message_id`; Python generates it and returns it in the terminal `done` event.

Request body:

```json
{
  "user_id": "u_1a2b3c",
  "analysis_id": "an_42",
  "message": "What were total sales by region last quarter?"
}
```

Fields:

| Field | Required | Description |
| --- | --- | --- |
| `user_id` | Yes | User identifier. |
| `analysis_id` | Yes | Analysis conversation identifier. |
| `message` | Yes | User message text. |

Response: `text/event-stream`.

Example structured answer:

```text
event: sources
data: []

event: status
data: Planning analysis...

event: status
data: Running 3 steps...

event: chunk
data: Total sales by region last quarter:

event: chunk
data: Central led at $1.21M (38%), East $0.74M, West $0.55M (down 12% QoQ).

event: done
data: {"message_id":"msg_88f1"}
```

Example simple chat answer:

```text
event: sources
data: []

event: chunk
data: I'm your AI data analyst. Connect a source or ask a question to get started.

event: done
data: {"message_id":"msg_12"}
```

Behavior notes:

- Greeting and farewell messages may use a fast canned path.
- Stateless `chat` intent may use a 1-hour Redis response cache.
- The router may classify messages into intents such as `chat`, `help`, `check`, `unstructured_flow`, `structured_flow`, or `out_of_scope`.
- `sources` in the stream is **always `[]`** — read the real `sources[]` from `GET /api/v1/traceability` after `done`.
- `status` events are optional and should be safe for the frontend to ignore.
- When the user explicitly asks to plot/visualize ("show me a bar chart of…", "buatkan grafik…"), the answer text describes the result and the chart itself is delivered via `GET /api/v1/charts` — it is never embedded in `chunk` text.

## Tools

### `GET /api/v1/tools/list`

Returns the deterministic list of tools available to the frontend.

Request: none.

Response `200`:

```json
{
  "count": 1,
  "tools": [
    {
      "command": "/help",
      "name": "help",
      "type": "skill",
      "description": "Show what the assistant can do and guide your next step."
    }
  ]
}
```

The catalog is `/help` only. `/report` is not a slash command — report generation is a right-side **Generate** button; the button calls `POST /api/v1/tools/report`.

Tool item shape:

```json
{
  "command": "/help",
  "name": "help",
  "type": "skill",
  "description": "Show what the assistant can do and guide your next step."
}
```

Frontend behavior:

- Surface `/help` in the slash menu.
- Surface report generation as a button or explicit UI action, driven by `GET /tools/report/{analysis_id}/readiness`.

### `POST /api/v1/tools/help`

Streams contextual guidance for the current analysis conversation.

Request body:

```json
{
  "user_id": "u_1a2b3c",
  "analysis_id": "an_42"
}
```

Response: `text/event-stream` using the same event shape as chat.

Help responses usually emit `sources: []` and no `status` pings.

Example:

```text
event: sources
data: []

event: chunk
data: Your goal is set. You can start exploring now. Try a question like "average order value by month", then I can generate a report.

event: done
data: {"message_id":"msg_h7"}
```

## Reports

### `POST /api/v1/tools/report`

Generates, persists, and returns a new report version for an analysis.

Query params:

| Query | Required | Description |
| --- | --- | --- |
| `analysis_id` | Yes | Analysis identifier. |
| `user_id` | Yes | User identifier. |
| `exclude_record_ids` | No | Record ids to leave out of this version (repeat the param per id). Get ids from `GET /tools/report/{analysis_id}/records`. Excluded runs are listed in the report's "Excluded Analyses" section. Excluding every substantive record returns `409`. |

Example:

```text
POST /api/v1/tools/report?analysis_id=an_42&user_id=u_1a2b3c
POST /api/v1/tools/report?analysis_id=an_42&user_id=u_1a2b3c&exclude_record_ids=rec_a1&exclude_record_ids=rec_c3
```

Status codes:

| Status | Meaning |
| --- | --- |
| `201` | New report version generated. |
| `409` | Report floor/precondition not met. |
| `500` | Generation or persistence failed. |

Response `201`:

```json
{
  "report_id": "8f3a2b1c9d4e4f6a8b0c1d2e3f4a5b6c",
  "analysis_id": "an_42",
  "user_id": "u_1a2b3c",
  "version": 2,
  "generated_at": "2026-06-30T09:14:33.512Z",
  "problem_statement": {
    "objective": "Understand which regions drive revenue and why Q1 dipped.",
    "business_questions": [
      "Which regions contribute most to total revenue?",
      "Did any region decline quarter-over-quarter?"
    ]
  },
  "record_ids": ["rec_a1", "rec_b2"],
  "executive_summary": "Revenue is concentrated in the Central region (38% of total). The West was the only region to contract, down 12% QoQ, the main driver of the Q1 dip.",
  "bq_answers": [
    {
      "question": "Which regions contribute most to total revenue?",
      "answer": "The Central region leads with 38% of total revenue.",
      "status": "answered",
      "record_ids": ["rec_a1"]
    },
    {
      "question": "Did any region decline quarter-over-quarter?",
      "answer": "Yes — the West region fell 12% QoQ.",
      "status": "answered",
      "record_ids": ["rec_b2"]
    }
  ],
  "findings": [
    {
      "text": "Central region contributed 38% of total revenue, the largest share.",
      "record_ids": ["rec_a1"],
      "supporting_data": null
    },
    {
      "text": "West region revenue fell 12% quarter-over-quarter.",
      "record_ids": ["rec_b2"],
      "supporting_data": null
    }
  ],
  "caveats": [
    {
      "text": "March data for the East region was partially missing, around 6% of rows.",
      "record_ids": ["rec_b2"]
    }
  ],
  "open_questions": [
    {
      "text": "What drove the West region's QoQ decline?",
      "record_ids": ["rec_b2"]
    }
  ],
  "unresolved": [
    {
      "text": "Correlate churn with tenure — churn column not found in the source.",
      "record_ids": ["rec_d4"]
    }
  ],
  "excluded": [],
  "evidence_tables": {
    "rec_a1": [
      {
        "title": "Aggregate revenue by region",
        "columns": ["region", "total_revenue"],
        "rows": [["Central", "18321"], ["West", "9954"]],
        "truncated": false
      }
    ]
  },
  "charts": {
    "rec_a1": [
      {
        "schema": "dataeyond.chart.v1",
        "chart_type": "bar",
        "title": "Revenue by region",
        "plotly": {
          "data": [{ "type": "bar", "x": ["Central", "East", "West"], "y": [1210000, 740000, 550000], "name": "revenue" }],
          "layout": { "title": { "text": "Revenue by region" }, "xaxis": { "title": { "text": "region" } }, "yaxis": { "title": { "text": "revenue" } } }
        }
      }
    ]
  },
  "data_sources": [
    {
      "source_id": "src_sales_db",
      "name": "orders",
      "source_type": "postgres",
      "detail": {
        "tables": ["orders"],
        "row_count": 48213,
        "columns": ["region", "amount", "ordered_at"]
      }
    }
  ],
  "method_steps": [
    {
      "task_id": "t1",
      "stage": "data_understanding",
      "objective": "Inventory the sales source",
      "status": "success",
      "tools_used": ["check_data"]
    },
    {
      "task_id": "t2",
      "stage": "modeling",
      "objective": "Aggregate revenue by region",
      "status": "success",
      "tools_used": ["analyze_aggregate"]
    }
  ],
  "rendered_markdown": "# Analysis Report\n\n*Generated 2026-06-30 by u_1a2b3c*\n\n## Objective\nUnderstand which regions drive revenue..."
}
```

Field notes:

- `bq_answers` — one entry per business question. `status` is `answered` | `partial` | `unanswered`; `record_ids` cite the backing analyses. Written in the analysis's language (Indonesian objective → Indonesian answers).
- `unresolved` — runs that were attempted but produced no usable evidence. Not part of the findings body.
- `excluded` — runs the caller excluded via `exclude_record_ids`.
- `evidence_tables` — `record_id` → small result tables copied from the run's stored outputs (max 3 tables per record, max 10 rows each; `truncated: true` when rows were capped). Rendered as markdown tables under the matching Key Findings group in `rendered_markdown`.
- `charts` — `record_id` → chart envelopes (same `dataeyond.chart.v1` shape as `GET /api/v1/charts` returns; max 3 per record) copied from the run's stored outputs. `rendered_markdown` contains an `## EDA` section where each chart appears as a fenced block:

  ````text
  ```plotly
  {
    "schema": "dataeyond.chart.v1",
    "chart_type": "bar",
    "title": "…",
    "plotly": { "data": [ … ], "layout": { … } }
  }
  ```
  ````

  The fence content is the full envelope — parse it and render `Plotly.newPlot(el, parsed.plotly.data, parsed.plotly.layout)`. A bold caption line (the chart title) precedes each fence.

Precondition:

- Reports require at least one completed analysis record for the session. A run counts when an analysis step succeeded **or** a chart was produced — a chart-only session can generate a report.
- If slow-path analysis recording is disabled, report generation can return `409` by design.

Response `409`:

```json
{
  "detail": "Not ready to generate a report - still needs at least one completed analysis."
}
```

### `GET /api/v1/tools/report/{analysis_id}`

Lists report versions for one analysis, oldest first.

Response `200`:

```json
[
  {
    "report_id": "1b2c3d4e",
    "version": 1,
    "generated_at": "2026-06-24T15:02:11Z",
    "record_count": 1
  },
  {
    "report_id": "8f3a2b1c",
    "version": 2,
    "generated_at": "2026-06-25T09:14:33Z",
    "record_count": 2
  }
]
```

If no reports exist, returns `[]`.

### `GET /api/v1/tools/report/{analysis_id}/records`

Lists the persisted analysis runs a report would be built from, oldest first. The frontend shows this before generating so the user can deselect runs; the chosen ids go to `POST /tools/report` as `exclude_record_ids`.

Response `200`:

```json
[
  {
    "record_id": "rec_a1",
    "goal_restated": "Rank regions by total revenue",
    "created_at": "2026-06-30T08:55:02Z",
    "substantive": true,
    "findings_count": 2
  },
  {
    "record_id": "rec_d4",
    "goal_restated": "Correlate churn with tenure",
    "created_at": "2026-06-30T09:01:47Z",
    "substantive": false,
    "findings_count": 1
  }
]
```

`substantive: false` means the run produced no usable result (no analysis step or chart succeeded) — that run is listed in the report's `unresolved` JSON field rather than the findings body. If no runs exist, returns `[]`.

### `GET /api/v1/tools/report/{analysis_id}/readiness`

Deterministic report-readiness signal for the Generate-Report button — the same producer as Help's readiness signal, so the button and Help never disagree.

Response `200`:

```json
{
  "ready": false,
  "missing": ["a new analysis since the last report"]
}
```

Note: `POST /tools/report` itself only enforces the floor (at least one completed analysis). The delta gap in `missing` is a soft warning the frontend can surface ("nothing new since the last report") without blocking the button.

### `GET /api/v1/tools/report/{analysis_id}/{version}`

Returns one report version. Shape is the same as the `201` response from `POST /api/v1/tools/report`.

Response `404`:

```json
{
  "detail": "No report v3 for analysis 'an_42'."
}
```

## Charts

A chart is produced when the user explicitly asks to plot/visualize something in chat. The chart is never embedded in the streamed text — it is fetched separately after the stream completes, then rendered with plotly.js under the assistant message.

### `GET /api/v1/charts`

Returns every chart produced during one assistant answer.

Call this after the chat stream emits `done`, using the `message_id` from the `done` event (same fetch-on-`done` pattern as traceability). Chart rows are written before `done`, so there is no polling race. Every response is HTTP `200` — branch on the `status` field, not the HTTP code.

Query params:

| Query | Required | Description |
| --- | --- | --- |
| `message_id` | Yes | Assistant answer identifier returned by the stream's `done` event. |

Example:

```text
GET /api/v1/charts?message_id=88f10c3a-6f03-4204-bf98-41ffc20388b2
```

Response `200` — `status: "success"` (≥1 chart to render):

```json
{
  "status": "success",
  "message": "1 chart(s) for this message.",
  "count": 1,
  "charts": [
    {
      "chart_id": "3fbd8e2e-8e21-4d4b-9b21-9e6b6a0a6a6e",
      "chart_type": "bar",
      "title": "Revenue by region",
      "spec": {
        "schema": "dataeyond.chart.v1",
        "chart_type": "bar",
        "title": "Revenue by region",
        "plotly": {
          "data": [{ "type": "bar", "x": ["Central", "East", "West"], "y": [1210000, 740000, 550000], "name": "revenue" }],
          "layout": { "title": { "text": "Revenue by region" }, "xaxis": { "title": { "text": "region" } }, "yaxis": { "title": { "text": "revenue" } } }
        }
      },
      "created_at": "2026-07-13T03:21:09.114Z"
    }
  ]
}
```

Response `200` — `status: "empty"` (the turn completed but produced no charts; the common case, not an error):

```json
{
  "status": "empty",
  "message": "This message completed without producing charts.",
  "count": 0,
  "charts": []
}
```

Response `200` — `status: "not_found"` (no completed turn is known for this `message_id`; usually a stale or mistyped id):

```json
{
  "status": "not_found",
  "message": "No completed turn is known for this message_id.",
  "count": 0,
  "charts": []
}
```

The `dataeyond.chart.v1` envelope (the shape of `charts[].spec`):

```json
{
  "schema": "dataeyond.chart.v1",
  "chart_type": "bar",
  "title": "Revenue by region",
  "plotly": {
    "data": [{ "type": "bar", "x": ["A", "B"], "y": [1, 2], "name": "revenue" }],
    "layout": { "title": { "text": "Revenue by region" } }
  }
}
```

Field rules:

- `status` is the outcome marker: `success` | `empty` | `not_found`. Branch on it; do not parse `message` (human-readable, for logs only).
- `spec` is the full envelope, unmodified — render straight from it: `Plotly.newPlot(el, spec.plotly.data, spec.plotly.layout)`.
- `chart_type` / `title` are copied out of `spec` for convenience (list rendering without parsing `spec`); `title` may be `null`. Chart types: `bar`, `line`, `pie`, `scatter`.
- A turn can produce more than one chart; `charts` is ordered by creation time.

Frontend rendering guidance:

- Fetch unconditionally on every `done`; `status: "empty"` means render nothing extra.
- Render each chart under the assistant message it belongs to.
- Treat `status: "not_found"` as a signal worth logging (stale id or fetch bug) — not as a user-facing error.
- Chart iteration is a follow-up chat turn (e.g. "make it a line chart") — there is no separate edit endpoint.
- The same envelope shape appears inside report markdown as ` ```plotly ` fenced blocks (see Reports → `charts`), so one renderer can serve both surfaces.

## Traceability

### `GET /api/v1/traceability`

Returns user-facing provenance for one assistant answer.

The frontend should call this after the chat/help stream emits `done`, using the `message_id` from the `done` event. The row is written **before** `done`, so an immediate GET returns `200` (no polling race). A `404` means the id is unknown or the turn errored before completing (error turns never produce a row).

Query params:

| Query | Required | Description |
| --- | --- | --- |
| `analysis_id` | Yes | Analysis identifier. |
| `message_id` | Yes | Assistant answer identifier returned by the stream. |

Example:

```text
GET /api/v1/traceability?analysis_id=an_42&message_id=msg_88f1
```

`intent` values the frontend may see: `chat` · `help` · `check` · `unstructured_flow` · `structured_flow` · `out_of_scope` · `blocked` (`blocked` = input-guard or content-filter refusal; `chat` also covers the greeting fast-path and cache replays).

Field rules:

- `planning`: present only when the planner ran (`structured_flow`); otherwise `null`.
- `thinking`: **always `null` in v1** — the field stays in the payload so it can be populated later without a contract change.
- `tool_calls`: every invoked tool with `summary` (plain-English one-liner), `input`, `output`, `status`, `task_id` (nullable), and `error` (nullable); empty for chat / help / greeting / refusal paths. `input`/`output` are the raw tool I/O (opaque ids) — render them in a collapsible "technical details" section, not the headline; use `summary` for the headline.
- A `render_chart` tool call reports a compact chart summary in `output` (`chart_type`, `title`, `trace_count`, `point_count`) — the full spec is served by `GET /api/v1/charts`, not here.
- `data_used`: one entry per structured data pull, resolved to **real names** for display (empty when no structured pull ran). Split into `columns_read` (columns read straight from the user's data, each tagged with its `roles`) and `output_columns` (`kind: "column"` = read from data, `kind: "computed"` = calculated, carrying a `formula` and no id). Also carries `tables` (all touched, including join targets), `joins`, `filters` (with a plain-language `description`), `group_by`, `order_by`, `limit`, `rows_returned`, and the executed `query`.
- **`id` fields are machine-only.** Every `id` in `data_used` (`source.id`, `tables[].id`, `columns_read[].id`) is for linking/audit — **the frontend must never render it.** Show `name` (qualified as `table.name`). A `computed` output column has no id by design.
- `sources`: required for retrieval flows; empty for chat / help / refusal paths and for `check`. Database sources also carry `source_name` (the DB's real name) and `tables` (every table touched).
- Summaries and filter descriptions are built from fixed templates, never an LLM — traceability adds no latency and cannot hallucinate.
- The payload also carries an internal `user_id` (ownership); the frontend may ignore it.
- Truncation: `preview` ≤ 5 rows; any string inside `input`/`output`/`preview`/`snippet` ≤ 300 chars (executed `query` ≤ 2000); rows beyond the preview are dropped (`row_count` is preserved).

Response `200` for `structured_flow`:

```json
{
  "analysis_id": "an_42",
  "message_id": "msg_88f1",
  "user_id": "user_7",
  "intent": "structured_flow",
  "generated_at": "2026-07-06T03:21:09.114Z",
  "planning": {
    "goal_restated": "Find which regions drive revenue and why Q1 dipped.",
    "assumptions": [],
    "steps": [
      {
        "step": 1,
        "stage": "data_understanding",
        "objective": "Inventory the sales source",
        "status": "success",
        "tools_used": ["check_data"]
      },
      {
        "step": 2,
        "stage": "modeling",
        "objective": "Aggregate revenue by region",
        "status": "success",
        "tools_used": ["retrieve_data", "analyze_aggregate"]
      }
    ]
  },
  "thinking": null,
  "tool_calls": [
    {
      "order": 1,
      "task_id": null,
      "name": "check_data",
      "summary": "Inspected your data source structure",
      "input": { "source_hint": "structured" },
      "output": {
        "kind": "table",
        "columns": ["source_id", "name", "source_type", "table_count"],
        "row_count": 1,
        "preview": [["src_sales_db", "orders", "schema", 1]]
      },
      "status": "success",
      "error": null
    },
    {
      "order": 2,
      "task_id": null,
      "name": "retrieve_data",
      "summary": "Retrieved 4 rows across 2 columns from orders",
      "input": { "ir": { "source_id": "src_sales_db", "table_id": "orders", "select": ["region", "amount"], "group_by": ["region"] } },
      "output": {
        "kind": "table",
        "columns": ["region", "total"],
        "row_count": 4,
        "preview": [["Central", 1210000], ["East", 740000]]
      },
      "status": "success",
      "error": null
    }
  ],
  "data_used": [
    {
      "source": { "id": "src_sales_db", "name": "sales db", "type": "schema" },
      "tables": [ { "id": "orders", "name": "orders", "role": "base" } ],
      "joins": [],
      "columns_read": [
        { "id": "c_region", "name": "region", "table": "orders", "data_type": "string",  "pii": false, "roles": ["selected", "grouped"] },
        { "id": "c_amount", "name": "amount", "table": "orders", "data_type": "decimal", "pii": false, "roles": ["aggregated"] }
      ],
      "output_columns": [
        { "name": "region", "kind": "column",   "from": "orders.region" },
        { "name": "total",  "kind": "computed", "from": "orders.amount", "formula": "SUM(orders.amount)" }
      ],
      "filters": [],
      "group_by": ["orders.region"],
      "order_by": [],
      "limit": null,
      "rows_returned": 4,
      "query": "SELECT region, SUM(amount) AS total FROM orders GROUP BY region"
    }
  ],
  "sources": [
    {
      "type": "database",
      "source_id": "src_sales_db",
      "source_name": "sales db",
      "name": "orders",
      "tables": ["orders"],
      "query": "SELECT region, SUM(amount) AS total FROM orders GROUP BY region",
      "detail": {
        "table": "orders",
        "row_count": 4
      }
    }
  ]
}
```

> Note: `retrieve_data`'s real `input` is the compiled query IR under an `ir` key (the planner builds an IR, never raw SQL). The executed SQL/rendered query appears on the corresponding `sources[].query`.

Response `200` for `unstructured_flow`:

```json
{
  "analysis_id": "an_42",
  "message_id": "msg_55",
  "user_id": "user_7",
  "intent": "unstructured_flow",
  "generated_at": "2026-07-06T03:40:02.001Z",
  "planning": null,
  "thinking": null,
  "tool_calls": [
    {
      "order": 1,
      "task_id": null,
      "name": "retrieve_knowledge",
      "input": { "query": "technology stack used in this project" },
      "output": { "kind": "documents", "row_count": 4 },
      "status": "success",
      "error": null
    }
  ],
  "sources": [
    {
      "type": "document",
      "document_id": "doc_7",
      "filename": "tech_handbook.pdf",
      "page_label": "12",
      "query": "technology stack used in this project",
      "snippet": "The backend is built on FastAPI with async SQLAlchemy...",
      "score": 0.83
    }
  ]
}
```

Response `200` for chat / greeting / help / refusals (`out_of_scope`, `blocked`):

```json
{
  "analysis_id": "an_42",
  "message_id": "msg_12",
  "user_id": "user_7",
  "intent": "chat",
  "generated_at": "2026-07-06T03:05:00.000Z",
  "planning": null,
  "thinking": null,
  "tool_calls": [],
  "sources": []
}
```

Response `404`:

```json
{
  "detail": "No traceability for message 'msg_88f1' yet."
}
```

Frontend rendering guidance:

- Render traceability separately from the streamed answer.
- Default state can be collapsed.
- Show planning, tool calls, and sources as separate sections.
- Treat `planning: null`, `tool_calls: []`, and `sources: []` as valid states.