# MsgLib read-only sidecar contract

Date: 2026-07-10

## Purpose

`MsgLibReadSidecar` is the bounded 32-bit .NET process used by the Go MCP layer to access copied or operator-local `MsgLib.db` files through the client-compatible `System.Data.SQLite` provider.

It exists because C26 proved the database opens with the bundled 32-bit SQLite provider and password `123`, while a 64-bit probe fails at provider loading. Go should coordinate the process; the sidecar owns only the narrow Windows/.NET DB read boundary.

## Protocol

- Protocol id: `isphere.msglib.v1`
- Transport: one JSON request on stdin, one JSON response on stdout.
- Process architecture: x86.
- Database mode: read-only only.
- Raw rows: not returned by the first contract.
- Message bodies: not returned by the first contract.
- DB mutation: never allowed.

Request envelope:

```json
{
  "protocol": "isphere.msglib.v1",
  "request_id": "example-1",
  "op": "self_check",
  "args": {}
}
```

Response envelope:

```json
{
  "protocol": "isphere.msglib.v1",
  "request_id": "example-1",
  "op": "self_check",
  "ok": true,
  "data": {},
  "error": null,
  "warnings": []
}
```

## Operations

### `self_check`

Returns sidecar identity, protocol, runtime, process bitness, and capability flags.

Key response fields:

- `sidecar_name`
- `sidecar_version`
- `protocol`
- `runtime`
- `process_bits`
- `requires_process_bits`
- `db_mutation_allowed=false`
- `message_body_reads_allowed=false`

### `schema_summary`

Validates provider load and read-only DB open, then returns schema metadata only.

Required args:

- `sqlite_dll_path`: path to bundled `System.Data.SQLite.dll`.
- `db_path`: path to a copied/operator-local `MsgLib.db`.

Optional args:

- `password`: default `123`.
- `include_counts`: default `true`; returns row counts only for target tables.
- `max_tables`: default `128`, clamped to `1..256`.
- `target_tables`: optional list; defaults to known display/message/file metadata tables.

Returned data:

- `metadata_only=true`
- `read_only=true`
- `message_body_values_returned=false`
- `sqlite_version`
- `tables`: table/view names only.
- `columns`: table column names/types only.
- `target_row_counts`: safe row counts for target tables only.

### `display_sources`

Same safe provider/DB validation as `schema_summary`, but additionally maps schema availability to product-facing display source candidates.

Returned data adds:

- `display_sources[]` entries with:
  - `source`
  - `table`
  - `available`
  - `required_columns`
  - `present_columns`

Initial display sources:

- `contacts_roster` from `TD_Roster`.
- `contacts_effigy` from `TD_CustomEffigy`.
- `recent_display` from `tblRecent`.
- `person_message_names` from `tblPersonMsg`.
- `group_message_names` from `tblMsgGroupPersonMsg`.
- `work_group_auth` from `TD_WorkGroupAuth`.
- `received_file_metadata` from `TD_ReceiveFileRecord`.
- `sent_file_metadata` from `TD_SendFileRecord`.

## Security and scope rules

- The sidecar must open DB files with read-only connection settings.
- `db_path` must point to a file named `MsgLib.db`.
- The first contract returns schema, columns, counts, and display-source availability only.
- It does not return message bodies, contact row values, file paths, or raw row sets.
- It does not implement send, file download, mark-read, login, hooks, injection, or DB writes.
- The Go MCP layer remains the coordinator; this process is a bounded local reader.

## Current implementation

Committed C27 implementation:

- Source: `native/MsgLibReadSidecar/`.
- Build script: `scripts/build-msglib-sidecar.ps1`.
- Verification script: `scripts/verify-msglib-sidecar.ps1`.
- Default verification builds an x86 executable and checks `self_check`.
- Evidence-backed verification with C26 paths checked provider load/read-only DB open and returned 8 display-source candidates.

## Go client wrapper

Committed C28 implementation:

- Source: `internal/msglib/`.
- `ConfigFromEnv` reads `ISPHERE_MSGLIB_SIDECAR_EXE`, `ISPHERE_MSGLIB_SQLITE_DLL`, `ISPHERE_MSGLIB_DB`, and optional `ISPHERE_MSGLIB_PASSWORD`.
- `NewClient` creates a process-backed client for protocol `isphere.msglib.v1`.
- `SelfCheck` calls `self_check` and decodes sidecar identity, protocol, bitness, and read-only/no-mutation flags.
- `DisplaySources` calls `display_sources` and decodes display-source availability metadata.
- The client uses stdin/stdout JSON, request ids, `context.Context`, per-call timeout, stderr capture, and typed `SidecarError` values.
- Unit tests use a fake sidecar process; normal tests do not require real `System.Data.SQLite.dll` or copied `MsgLib.db`.
- C28 does not register a new MCP tool and does not return message bodies, file paths, raw rows, contact row values, or group row values.

## Verification

Default verification builds and checks `self_check` only:

```powershell
powershell -NoProfile -ExecutionPolicy Bypass -File scripts\verify-msglib-sidecar.ps1
```

Evidence-backed provider verification is opt-in through environment variables and should use copied DB files only:

```powershell
$env:ISPHERE_MSGLIB_SQLITE_DLL = "<path-to-System.Data.SQLite.dll>"
$env:ISPHERE_MSGLIB_DB = "<path-to-copied-MsgLib.db>"
powershell -NoProfile -ExecutionPolicy Bypass -File scripts\verify-msglib-sidecar.ps1
```