feat(files): SFTP member storage — private workspaces + shared public area + mgmt TUI

Implements M4 (Files). A fully virtual Go SFTP server (pkg/sftp + crypto/ssh,
no OS users) wired as an "sftp" subsystem on the existing :22 wish listener, so
members reach their files with their login key:

    sftp files@bbs.profullstack.com     # scp/rsync ride the same endpoint

Identity is the SSH key (the username is conventional/ignored). Two areas per
session: a private, quota-limited /me workspace and a single shared public file
area /public (old-school BBS file area; world-read, members-only write by
default, operator-moderated). This reverses the old NG1 "no sharing" boundary in
favour of one sanctioned, inspectable sharing surface (PRD §9.3 amended).

internal/files:
- backend.go  service, layout, quota/usage, live-session registry, operator API
- fs.go       per-session virtual FS; resolve() is the single security
              chokepoint (area confinement + symlink-escape guard) + pkg/sftp
              request handlers
- server.go   subsystem handler: key auth -> member session -> request server,
              with byte metering and force-disconnect
- tui.go      in-BBS member browser (hub plugin "Files")
- admin.go    operator management TUI: sessions, workspaces/quotas, public area

Operator console: ssh sftp@<host> (allowlist-gated; sftpadmin@/filesadmin@
aliases) — list/disconnect sessions, set per-user quotas, revoke SFTP access,
toggle public write, moderate the public area.

store: files_access (per-user quota override + revoked) and files_settings
(public-write mode) tables + methods. main.go wiring guarded by AGENTBBS_FILES
(+ AGENTBBS_FILES_QUOTA_MB, default 1 GiB). Route names reserved.

Tests (incl -race): path traversal/confinement, symlink-escape rejection,
public-write ACL, quota enforcement, usage accounting, and an end-to-end run
against a real SFTP client. Docs: docs/files.md; PRD §5.3/§5.3.1/§9.3 + README
updated.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

README.md

@@ -36,7 +36,7 @@ plugins around one shared account system; the full product plan is in
 | M3 — AgentGames (`game@` + WebSocket; TTT/C4, ELO ladder, replays) | ✅ |
 | IRC (`irc.bbs.profullstack.com` — Ergo network for humans + agents) | ✅ |
 | News (`news.profullstack.com` — members-only Usenet/NNTP for humans + agents) | ✅ |
-| M4 — Files (cl1.tech SFTP workspaces) | ⬜ |
+| M4 — Files (SFTP: private workspaces + shared public area, mgmt TUI) | ✅ |
 | M5 — AgentAd marketplace (built on the AgentAd standard in logicsrc) | ⬜ |
 
 ## Run it
@@ -67,6 +67,8 @@ Configuration (env):
 | `AGENTBBS_GAME_MOVE_TIMEOUT` | `15` | AgentGames per-move deadline (s) — see [docs/agentgames.md](docs/agentgames.md) |
 | `AGENTBBS_GAME_QUEUE_WAIT` | `120` | how long a lone agent waits for an opponent (s) |
 | `AGENTBBS_GAME_WS_ADDR` | `127.0.0.1:8090` | AgentGames WebSocket endpoint (loopback; Caddy proxies `/play`) |
+| `AGENTBBS_FILES` | `1` | member SFTP storage subsystem + Files plugin (`0` disables) — see [docs/files.md](docs/files.md) |
+| `AGENTBBS_FILES_QUOTA_MB` | `1024` | default per-user workspace quota (MB) |
 
 Ops:
 
@@ -143,6 +145,24 @@ news.profullstack.com:563   # implicit TLS; login = your BBS member name
 Set `NEWS=0` to skip it. Needs a DNS record `news.profullstack.com A -> host`.
 Full details: [`docs/news.md`](docs/news.md).
 
+### Files (SFTP)
+
+Every member gets file storage over **SFTP**, on the same `:22` listener and the
+same SSH key they log in with (`internal/files`, a virtual Go SFTP server — no OS
+users). Two areas: a **private, quota-limited** `/me` workspace and a single
+**shared public file area** `/public` (old-school BBS file area; members-only
+write by default). `scp` and `rsync` ride the same endpoint:
+
+```bash
+sftp files@bbs.profullstack.com           # username is conventional; your key is your identity
+scp file.pdf files@bbs.profullstack.com:/me/
+```
+
+There's also an in-hub **Files** browser and an operator management TUI
+(`ssh sftp@bbs.profullstack.com`, operators only) for sessions, quotas, and
+moderating the public area. Set `AGENTBBS_FILES=0` to disable. Full details:
+[`docs/files.md`](docs/files.md).
+
 ## Architecture
 
 - **Go + charmbracelet** — `wish` SSH server, `bubbletea` TUIs, `lipgloss` styling.

cmd/agentbbs/admin.go

@@ -13,6 +13,7 @@ import (
 	"github.com/profullstack/agentbbs/internal/admin"
 	"github.com/profullstack/agentbbs/internal/auth"
 	"github.com/profullstack/agentbbs/internal/calls"
+	"github.com/profullstack/agentbbs/internal/files"
 	"github.com/profullstack/agentbbs/internal/plugin"
 )
 
@@ -154,6 +155,32 @@ func (a *app) adminTeaHandler(s ssh.Session) (tea.Model, []tea.ProgramOption) {
 	return m, []tea.ProgramOption{tea.WithAltScreen()}
 }
 
+// filesAdminTeaHandler launches the SFTP server management TUI. Like admin@ it
+// is gated by the operator allowlist and re-checked here so a direct hit is
+// safe. Members transfer files via the sftp subsystem, not this route.
+func (a *app) filesAdminTeaHandler(s ssh.Session) (tea.Model, []tea.ProgramOption) {
+	if a.files == nil {
+		wish.Println(s, "the Files service is disabled (AGENTBBS_FILES=0).")
+		_ = s.Exit(1)
+		return nil, nil
+	}
+	fp := auth.Fingerprint(s.PublicKey())
+	var name string
+	if fp != "" {
+		if u, found, _ := a.st.UserByFingerprint(fp); found {
+			name = u.Name
+		}
+	}
+	if name == "" || !auth.IsAdmin(name) {
+		wish.Println(s, "the SFTP management console is restricted to operators.")
+		_ = s.Exit(1)
+		return nil, nil
+	}
+	sessID, _ := a.st.RecordSession(0, s.User(), remoteIP(s), "sftp-admin")
+	go func() { <-s.Context().Done(); _ = a.st.EndSession(sessID) }()
+	return files.NewAdminModel(a.files), []tea.ProgramOption{tea.WithAltScreen()}
+}
+
 func sortedKeys(m map[string]bool) []string {
 	out := make([]string, 0, len(m))
 	for k := range m {

cmd/agentbbs/main.go

@@ -55,6 +55,7 @@ import (
 	"github.com/profullstack/agentbbs/internal/brand"
 	"github.com/profullstack/agentbbs/internal/calls"
 	"github.com/profullstack/agentbbs/internal/chat"
+	"github.com/profullstack/agentbbs/internal/files"
 	"github.com/profullstack/agentbbs/internal/forgejo"
 	"github.com/profullstack/agentbbs/internal/forwardemail"
 	"github.com/profullstack/agentbbs/internal/games"
@@ -102,6 +103,7 @@ type app struct {
 	fe       forwardemail.Config // premium @bbs email provisioning
 	forgejo  forgejo.Config      // AgentGit git.profullstack.com account provisioning
 	live     *liveReg            // in-memory live-session registry (admin console)
+	files    *files.Service      // SFTP file storage (nil when AGENTBBS_FILES=0)
 	gamesReg *games.Registry     // AgentGames catalog
 	mm       *games.Matchmaker   // AgentGames matchmaker (agent-vs-agent)
 	dataDir  string
@@ -173,6 +175,22 @@ func main() {
 		time.Duration(envInt("AGENTBBS_GAME_QUEUE_WAIT", 120))*time.Second)
 	a.registry = []plugin.Plugin{arcade.Plugin{}, agentgames.New(a.gamesReg), qryptinviteplugin.Plugin{}, about.Plugin{}}
 
+	// Files (SFTP): per-user workspaces + a shared public area, reached over the
+	// :22 listener via `sftp files@<host>` (docs/files.md). Disable with
+	// AGENTBBS_FILES=0. The in-BBS browser is a hub plugin; the operator
+	// management TUI is the sftp@ route.
+	if env("AGENTBBS_FILES", "1") == "1" {
+		fsvc, err := files.New(a.st, files.Config{
+			Root:         filepath.Join(dataDir, "files"),
+			DefaultQuota: int64(envInt("AGENTBBS_FILES_QUOTA_MB", 1024)) << 20,
+		})
+		if err != nil {
+			log.Fatal("files", "err", err)
+		}
+		a.files = fsvc
+		a.registry = append(a.registry, files.NewPlugin(fsvc))
+	}
+
 	// Custom domains: maintain the symlink farm Caddy serves and answer its
 	// on-demand-TLS "ask" query so certs are only issued for mapped domains.
 	if sm, err := sites.NewManager(st, dataDir); err != nil {
@@ -250,7 +268,7 @@ func main() {
 	}
 
 	addr := env("AGENTBBS_ADDR", ":2222")
-	srv, err := wish.NewServer(
+	opts := []ssh.Option{
 		wish.WithAddress(addr),
 		wish.WithHostKeyPath(filepath.Join(dataDir, "ssh", "host_ed25519")),
 		// Keys are always accepted at the transport layer; identity and
@@ -264,7 +282,13 @@ func main() {
 			a.track(), // register every session for the admin console
 			logging.Middleware(),
 		),
-	)
+	}
+	// SFTP rides the same :22 listener as a subsystem; identity is the SSH key,
+	// so `sftp files@<host>` works with the member's login key.
+	if a.files != nil {
+		opts = append(opts, wish.WithSubsystem("sftp", a.files.Subsystem()))
+	}
+	srv, err := wish.NewServer(opts...)
 	if err != nil {
 		log.Fatal("server", "err", err)
 	}
@@ -291,9 +315,11 @@ func main() {
 func (a *app) router() wish.Middleware {
 	btMw := bm.Middleware(a.teaHandler)
 	adminMw := bm.Middleware(a.adminTeaHandler)
+	filesAdminMw := bm.Middleware(a.filesAdminTeaHandler)
 	return func(next ssh.Handler) ssh.Handler {
 		hubHandler := activeterm.Middleware()(btMw(next))
 		adminHandler := activeterm.Middleware()(adminMw(next))
+		filesAdminHandler := activeterm.Middleware()(filesAdminMw(next))
 		return func(s ssh.Session) {
 			user := strings.ToLower(s.User())
 			code, isVideo := calls.RouteCode(user)
@@ -318,6 +344,8 @@ func (a *app) router() wish.Middleware {
 				a.handleNews(s)
 			case auth.IsMailName(user):
 				a.handleMail(s)
+			case auth.IsFilesAdminName(user):
+				filesAdminHandler(s)
 			case isVideo:
 				a.handleVideo(s, code)
 			case user == "agent":

docs/PRD.md

@@ -30,7 +30,7 @@ supply inventory. The BBS hub is the funnel that builds that audience.
 |---|---|
 | `profullstack.com` | Primary BBS host — `ssh play@profullstack.com` (guest) and member access |
 | `logicsrc.com` | Home of the AgentGames spec and developer/agent-facing docs |
-| `cl1.tech` | Managed file-transfer service (SFTP product), surfaced in-BBS as a plugin |
+| `bbs.profullstack.com` | Member file storage over SFTP — `sftp files@bbs.profullstack.com` (same SSH key as login) |
 
 ### 1.2 One-line pitch
 
@@ -100,7 +100,7 @@ supply inventory. The BBS hub is the funnel that builds that audience.
         ▼                 ▼                   ▼                 ▼
    ┌─────────┐      ┌───────────┐      ┌────────────┐    ┌──────────┐
    │ Arcade  │      │ AgentGames│      │ Files       │    │ AgentAd  │
-   │ plugin  │      │ plugin    │      │ (cl1.tech)  │    │ plugin   │
+   │ plugin  │      │ plugin    │      │ (SFTP)      │    │ plugin   │
    └────┬────┘      └─────┬─────┘      └─────┬──────┘    └────┬─────┘
         └─────────── sandbox runner ─────────┘                │
                           │                                   │
@@ -193,20 +193,46 @@ Same backend, inverted player: **AI agents connect and compete**.
 - **Spec home:** the protocol and SDK live on `logicsrc.com` for agent
   developers.
 
-### 5.3 Files (cl1.tech)
+### 5.3 Files (SFTP)
 
-A managed file workspace, surfaced in-BBS and as a standalone SFTP product on
+Member file storage for bbs.profullstack.com, surfaced in-BBS and reachable
-`cl1.tech`.
+directly over SFTP with the member's existing SSH login key.
 
-- **Model:** strictly **private, per-user** storage. Each account is chrooted to
+- **Model:** two areas per server:
-  its own directory tree with a disk quota.
+  1. **Private, per-user** storage — each account is virtually chrooted to its
-- **Access:** SFTP via OpenSSH `internal-sftp` (chrooted) or a Go SFTP server
+     own directory tree with a disk quota. The default and primary surface.
-  (`pkg/sftp` + `crypto/ssh`) for fully virtual users, quotas, and logging in
+  2. **A single shared public file area** — an operator-run, communal directory
-  application code.
+     (old-school BBS file area). World-readable; write access is a tunable
-- **In-BBS view:** a TUI file browser for the user's own workspace (list,
+     (members-only by default). Operator-moderated; not encrypted or blind.
-  rename, delete, view usage vs. quota).
+- **Access:** a **virtual Go SFTP server** (`pkg/sftp` + `crypto/ssh`) for fully
-- **Explicitly out of scope:** any user-to-user transfer, shared drop, or
+  virtual users, app-level quotas, per-path ACLs, and logging — no OS users.
-  public directory feature (§9.3, NG1).
+  Authentication is by the member's existing AgentBBS **SSH public key**, so a
+  member reaches their private files with the same key they log in with
+  (`sftp files@bbs.profullstack.com`). `scp`/`rsync -e ssh` work over the same
+  endpoint.
+- **In-BBS view:** a TUI file browser for the user's own workspace and the
+  shared area (list, rename, delete, up/download path, view usage vs. quota).
+- **Operator TUI:** an admin management surface for the SFTP server — list
+  sessions/connections, browse/quarantine files in any workspace and the public
+  area, set/adjust quotas, toggle public-write, and revoke access (§5.3.1).
+- **Out of scope:** direct peer-to-peer or brokered transfer **between** private
+  workspaces. Sharing happens only through the single moderated public area
+  (§9.3, NG1 as amended).
+
+#### 5.3.1 Management TUI
+
+A `bubbletea` admin console (gated to operators/admins), reachable both as an
+in-BBS admin route and standalone. Panes:
+
+- **Sessions:** live SFTP connections (user, key fingerprint, bytes, idle time),
+  with force-disconnect.
+- **Workspaces:** per-user usage vs. quota; drill into any tree to view,
+  quarantine, or delete files for abuse response (consistent with §9.2 — the
+  operator can act on its own systems).
+- **Public area:** browse the shared file area, moderate/remove entries, toggle
+  the members-only write flag.
+- **Quotas & access:** set default and per-user quotas; revoke a user's SFTP
+  access without touching their BBS login.
 
 ### 5.4 AgentAd (marketplace)
 
@@ -306,12 +332,18 @@ The platform does **not** adopt content-blind/zero-knowledge storage designed so
 the operator cannot inspect hosted files. Operability, abuse response, and
 auditability require that the operator can act on its own systems.
 
-### 9.3 No user-to-user distribution
+### 9.3 No peer-to-peer distribution (amended)
 
-File workspaces are private and per-user. The platform provides **no** feature
+Private workspaces remain private and per-user: the platform provides **no**
-for users to share or transfer files to one another — no shared directories, no
+feature for users to transfer files directly to one another — no peer drop, no
-peer drop, no brokered transfer — in any transport or encryption configuration.
+brokered workspace-to-workspace transfer — in any transport or encryption
-This is a hard product boundary, not a tunable.
+configuration. That direct path is a hard product boundary, not a tunable.
+
+Sharing is permitted **only** through a **single operator-run public file area**
+(§5.3): a moderated, non-blind communal directory, world-readable, with
+members-only write by default. Because it is operator-run and inspectable
+(§9.2), the operator can moderate and act on takedown notices (§9.4). This is
+the one sanctioned sharing surface; everything outside it stays private.
 
 ### 9.4 Standard hosting compliance
 
@@ -333,7 +365,7 @@ from the start.
 | **M1 — Arcade** | doom-ascii + Freedoom/shareware, sandbox runner, guest play, member saves & leaderboards |
 | **M2 — Admin** | plugin enable/disable, user moderation, session audit |
 | **M3 — AgentGames** | game protocol, phase-1 catalog, agent auth, ladders, replays; spec published on logicsrc.com |
-| **M4 — Files (cl1.tech)** | private per-user SFTP workspaces, quotas, in-BBS browser |
+| **M4 — Files (SFTP)** | virtual Go SFTP server (key auth), private per-user workspaces + quotas, single shared public area, in-BBS file browser, operator management TUI |
 | **M5 — AgentAd** | two-sided marketplace, buyer storefront, seller dashboard, creative review, revenue share |
 | **M6 — Hardening & scale** | rate limits, fail2ban, metrics, Postgres migration path, web buyer dashboard |
 
@@ -345,8 +377,10 @@ from the start.
    websocket/API endpoint? (Affects how non-interactive agents authenticate.)
 2. **Sandbox technology:** Docker/Podman per session vs. `systemd-run` transient
    scopes — which fits the target VPS footprint best?
-3. **Account model for the Files plugin:** real chrooted system users via
+3. ~~**Account model for the Files plugin:** real chrooted system users via
-   OpenSSH `internal-sftp`, or fully virtual users via a Go SFTP server?
+   OpenSSH `internal-sftp`, or fully virtual users via a Go SFTP server?~~
+   **Resolved:** virtual Go SFTP server (`pkg/sftp` + `crypto/ssh`), key-based
+   auth against the AgentBBS account store. (§5.3)
 4. **AgentAd inventory mix:** which surfaces ship first (interstitials vs. hub
    banners vs. sponsored ladder slots)?
 5. **Web footprint:** does the AgentAd buyer dashboard warrant a web app in v1,

docs/files.md

@@ -0,0 +1,95 @@
+# Files (SFTP) — member storage
+
+AgentBBS gives every verified member file storage over **SFTP**, reachable with
+the same SSH key they log in with. It rides the existing `:22` listener as an
+SSH *subsystem*, so there is no new port and no separate account:
+
+```bash
+# interactive
+sftp files@bbs.profullstack.com
+
+# one-shot copies (same endpoint, same key)
+scp report.pdf files@bbs.profullstack.com:/me/
+rsync -avz ./site/ -e ssh files@bbs.profullstack.com:/me/site/
+```
+
+The username (`files`) is conventional and ignored — **identity is your SSH
+key** (one key = one account, like the rest of the BBS). `scp`/`rsync` work
+because they tunnel over the same SSH transport.
+
+## Two areas
+
+When you connect you see a virtual root with two directories:
+
+| Path | What it is | Access |
+|---|---|---|
+| `/me` | Your **private** per-user workspace | read/write, quota-limited |
+| `/public` | The single **shared public file area** (old-school BBS file area) | world-read; members-only write by default |
+
+There is **no** path from one member's `/me` to another's — the only sharing
+surface is the one public area (PRD §9.3, amended). Both areas are confined: a
+path that tries to escape its root (`../`, an absolute path, or a planted
+symlink) is rejected.
+
+## Quotas
+
+Each private workspace has a byte quota (default **1 GiB**, set by
+`AGENTBBS_FILES_QUOTA_MB`). Writes that would exceed it fail. Operators can set a
+per-user override in the management TUI. The public area is operator-managed and
+not metered per user.
+
+## In-BBS browser
+
+Inside the hub, the **Files** entry opens a TUI browser for your workspace and
+the public area: navigate, view text files, make directories, rename, and
+delete, with a live usage gauge. Actual transfers happen over SFTP/scp/rsync (a
+PTY can't move file bytes).
+
+## Operator management TUI
+
+Operators (the `$AGENTBBS_ADMINS` allowlist) reach the SFTP management console
+with:
+
+```bash
+ssh sftp@bbs.profullstack.com      # aliases: sftpadmin@, filesadmin@
+```
+
+Panes (Tab to switch):
+
+- **Sessions** — live SFTP connections (user, remote, rx/tx, idle); `x`
+  force-disconnects.
+- **Workspaces** — every member's usage vs. quota; `Q` sets a per-user quota,
+  `x` revokes/restores SFTP access (the BBS login is unaffected).
+- **Public area** — `t` toggles members' write access; `x` removes an entry
+  (moderation).
+
+Per PRD §9.2 the operator can inspect and act on hosted files; storage is not
+content-blind.
+
+## Configuration
+
+| Var | Default | Meaning |
+|---|---|---|
+| `AGENTBBS_FILES` | `1` | enable the SFTP subsystem + Files plugin (`0` disables) |
+| `AGENTBBS_FILES_QUOTA_MB` | `1024` | default per-user workspace quota (MB) |
+| `AGENTBBS_DATA` | `./data` | storage lives under `<data>/files/{users,public}` |
+
+## Implementation
+
+- `internal/files` — a fully virtual Go SFTP server (`github.com/pkg/sftp` +
+  `crypto/ssh`); no OS users.
+  - `backend.go` — service, layout, quota/usage, live-session registry, operator
+    surface.
+  - `fs.go` — per-session virtual filesystem: `resolve()` is the single security
+    chokepoint (area confinement + symlink-escape guard) and the pkg/sftp
+    request handlers.
+  - `server.go` — the `wish.WithSubsystem("sftp", …)` handler: key auth → member
+    session → request server, with byte metering and force-disconnect.
+  - `tui.go` — the in-BBS member browser plugin.
+  - `admin.go` — the operator management TUI.
+- Storage: `files_access` (per-user quota override + revoked flag) and
+  `files_settings` (e.g. public-write mode) in the shared SQLite store.
+
+Security is covered by `internal/files/*_test.go`: path-traversal/confinement,
+symlink-escape rejection, the public-write ACL, quota enforcement, and an
+end-to-end run against a real SFTP client.

go.mod

@@ -16,6 +16,7 @@ require (
 	github.com/livekit/protocol v1.46.0
 	github.com/livekit/server-sdk-go/v2 v2.16.6
 	github.com/pion/webrtc/v4 v4.2.15
+	github.com/pkg/sftp v1.13.10
 	golang.org/x/crypto v0.50.0
 	golang.org/x/term v0.42.0
 	modernc.org/sqlite v1.52.0
@@ -62,6 +63,7 @@ require (
 	github.com/jxskiss/base62 v1.1.0 // indirect
 	github.com/klauspost/compress v1.18.4 // indirect
 	github.com/klauspost/cpuid/v2 v2.3.0 // indirect
+	github.com/kr/fs v0.1.0 // indirect
 	github.com/lithammer/shortuuid/v4 v4.2.0 // indirect
 	github.com/livekit/mageutil v0.0.0-20250511045019-0f1ff63f7731 // indirect
 	github.com/livekit/mediatransportutil v0.0.0-20260521165806-8004f10ad0c5 // indirect

go.sum

@@ -149,6 +149,8 @@ github.com/klauspost/compress v1.18.4 h1:RPhnKRAQ4Fh8zU2FY/6ZFDwTVTxgJ/EMydqSTzE
 github.com/klauspost/compress v1.18.4/go.mod h1:R0h/fSBs8DE4ENlcrlib3PsXS61voFxhIs2DeRhCvJ4=
 github.com/klauspost/cpuid/v2 v2.3.0 h1:S4CRMLnYUhGeDFDqkGriYKdfoFlDnMtqTiI/sFzhA9Y=
 github.com/klauspost/cpuid/v2 v2.3.0/go.mod h1:hqwkgyIinND0mEev00jJYCxPNVRVXFQeu1XKlok6oO0=
+github.com/kr/fs v0.1.0 h1:Jskdu9ieNAYnjxsi0LbQp1ulIKZV1LAFgK1tWhpZgl8=
+github.com/kr/fs v0.1.0/go.mod h1:FFnZGqtBN9Gxj7eW1uZ42v5BccTP0vu6NEaFoC2HwRg=
 github.com/kr/pretty v0.1.0 h1:L/CwN0zerZDmRFUapSPitk6f+Q3+0za1rQkzVuMiMFI=
 github.com/kr/pretty v0.1.0/go.mod h1:dAy3ld7l9f0ibDNOQOHHMYYIIbhfbHSm3C4ZsoJORNo=
 github.com/kr/text v0.2.0 h1:5Nx0Ya0ZqY2ygV366QzturHI13Jq95ApcVaJBhpS+AY=
@@ -243,6 +245,8 @@ github.com/pion/webrtc/v4 v4.2.15 h1:Ir/MauNFCfg+kgyBYPQLiGdVWFlzEcLxqtuzAkYkky0
 github.com/pion/webrtc/v4 v4.2.15/go.mod h1:CPTcyLfIzC4scOkQ4UY4pj6WvbUGhcNLIpK28cP5h6M=
 github.com/pkg/errors v0.9.1 h1:FEBLx1zS214owpjy7qsBeixbURkuhQAwrK5UwLGTwt4=
 github.com/pkg/errors v0.9.1/go.mod h1:bwawxfHBFNV+L2hUp1rHADufV3IMtnDRdf1r5NINEl0=
+github.com/pkg/sftp v1.13.10 h1:+5FbKNTe5Z9aspU88DPIKJ9z2KZoaGCu6Sr6kKR/5mU=
+github.com/pkg/sftp v1.13.10/go.mod h1:bJ1a7uDhrX/4OII+agvy28lzRvQrmIQuaHrcI1HbeGA=
 github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
 github.com/pmezard/go-difflib v1.0.1-0.20181226105442-5d4384ee4fb2 h1:Jamvg5psRIccs7FGNTlIRMkT8wgtp5eCXdBlqhYGL6U=
 github.com/pmezard/go-difflib v1.0.1-0.20181226105442-5d4384ee4fb2/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=

internal/auth/auth.go

@@ -69,6 +69,11 @@ var NewsNames = map[string]bool{"news": true}
 // an interactive TUI with a PTY, or a JSON bot mode with a command/no PTY.
 var MailNames = map[string]bool{"mail": true}
 
+// FilesAdminNames route an operator into the SFTP server management TUI. Members
+// transfer files via the "sftp" subsystem (sftp files@<host>); this interactive
+// route is the operator console and is gated by the admin allowlist.
+var FilesAdminNames = map[string]bool{"sftp": true, "sftpadmin": true, "filesadmin": true}
+
 // GameNames are usernames that route to AgentGames: the line-delimited-JSON
 // agent-vs-agent match protocol (PRD §5.2). `play@` stays a guest hub alias.
 var GameNames = map[string]bool{"game": true, "games": true}
@@ -103,6 +108,10 @@ func IsNewsName(u string) bool { return NewsNames[strings.ToLower(u)] }
 // IsMailName reports whether the SSH username requests the AgentMail client.
 func IsMailName(u string) bool { return MailNames[strings.ToLower(u)] }
 
+// IsFilesAdminName reports whether the SSH username requests the SFTP server
+// management TUI (operator-gated).
+func IsFilesAdminName(u string) bool { return FilesAdminNames[strings.ToLower(u)] }
+
 // systemReserved are names that don't drive an SSH route but would still
 // collide with a per-user subdomain (<name>.<host>), the agent route, or common
 // infra hostnames — so members may not claim them as account names.
@@ -119,7 +128,8 @@ var systemReserved = map[string]bool{
 func IsReservedName(name string) bool {
 	n := strings.ToLower(name)
 	if GuestNames[n] || PodNames[n] || JoinNames[n] || DomainNames[n] || AdminNames[n] ||
-		TorURLNames[n] || TorIRCNames[n] || TorNames[n] || IRCNames[n] || NewsNames[n] || systemReserved[n] {
+		TorURLNames[n] || TorIRCNames[n] || TorNames[n] || IRCNames[n] || NewsNames[n] ||
+		MailNames[n] || FilesAdminNames[n] || systemReserved[n] {
 		return true
 	}
 	return strings.HasPrefix(n, "video-") // video-<code> call routes

internal/auth/auth_test.go

@@ -85,3 +85,24 @@ func TestIsReservedName(t *testing.T) {
 		}
 	}
 }
+
+func TestIsFilesAdminName(t *testing.T) {
+	for _, name := range []string{"sftp", "SFTP", "sftpadmin", "filesadmin"} {
+		if !IsFilesAdminName(name) {
+			t.Errorf("IsFilesAdminName(%q) = false, want true", name)
+		}
+	}
+	for _, name := range []string{"files", "bbs", "anthony", ""} {
+		if IsFilesAdminName(name) {
+			t.Errorf("IsFilesAdminName(%q) = true, want false", name)
+		}
+	}
+}
+
+func TestFilesAdminNamesReserved(t *testing.T) {
+	for _, name := range []string{"sftp", "sftpadmin", "filesadmin", "mail"} {
+		if !IsReservedName(name) {
+			t.Errorf("IsReservedName(%q) = false, want true (route name)", name)
+		}
+	}
+}

internal/files/admin.go

@@ -0,0 +1,339 @@
+package files
+
+import (
+	"fmt"
+	"strconv"
+	"strings"
+	"time"
+
+	tea "github.com/charmbracelet/bubbletea"
+	"github.com/charmbracelet/lipgloss"
+
+	"github.com/profullstack/agentbbs/internal/store"
+)
+
+// NewAdminModel returns the operator management TUI for the SFTP server. Gate
+// the route that launches it on the operator allowlist (auth.IsAdmin).
+func NewAdminModel(svc *Service) tea.Model {
+	m := admin{svc: svc}
+	m.reload()
+	return m
+}
+
+type adminTab int
+
+const (
+	tabSessions adminTab = iota
+	tabWorkspaces
+	tabPublic
+	numTabs
+)
+
+var tabNames = []string{"Sessions", "Workspaces", "Public area"}
+
+type admin struct {
+	svc *Service
+	tab adminTab
+	sel int
+	msg string
+
+	sessions []Conn
+	users    []store.User
+	public   []Entry
+
+	input   bool
+	prompt  string
+	buf     string
+	onInput func(string)
+}
+
+func (m *admin) reload() {
+	m.sessions = m.svc.Sessions()
+	m.users, _ = m.svc.Users()
+	m.public, _ = m.svc.PublicList()
+	if m.sel < 0 {
+		m.sel = 0
+	}
+}
+
+func (m admin) Init() tea.Cmd { return nil }
+
+func (m admin) rows() int {
+	switch m.tab {
+	case tabSessions:
+		return len(m.sessions)
+	case tabWorkspaces:
+		return len(m.users)
+	case tabPublic:
+		return len(m.public)
+	}
+	return 0
+}
+
+func (m admin) Update(msg tea.Msg) (tea.Model, tea.Cmd) {
+	key, ok := msg.(tea.KeyMsg)
+	if !ok {
+		return m, nil
+	}
+	if m.input {
+		return m.updateInput(key)
+	}
+	switch key.String() {
+	case "q", "esc":
+		return m, tea.Quit
+	case "tab", "right", "l":
+		m.tab = (m.tab + 1) % numTabs
+		m.sel, m.msg = 0, ""
+	case "shift+tab", "left", "h":
+		m.tab = (m.tab + numTabs - 1) % numTabs
+		m.sel, m.msg = 0, ""
+	case "up", "k":
+		if m.sel > 0 {
+			m.sel--
+		}
+	case "down", "j":
+		if m.sel < m.rows()-1 {
+			m.sel++
+		}
+	case "g":
+		m.reload()
+		m.msg = "refreshed"
+	default:
+		return m.action(key)
+	}
+	return m, nil
+}
+
+func (m admin) action(key tea.KeyMsg) (tea.Model, tea.Cmd) {
+	switch m.tab {
+	case tabSessions:
+		if key.String() == "x" {
+			if c := m.curSession(); c != nil {
+				if m.svc.Kick(c.ID) {
+					m.msg = "disconnected " + c.User
+				}
+				m.reload()
+			}
+		}
+	case tabWorkspaces:
+		switch key.String() {
+		case "Q":
+			if u := m.curUser(); u != nil {
+				uid := u.ID
+				m.startInput("quota MB for "+u.Name+" (0 = default): ", func(s string) {
+					mb, err := strconv.ParseInt(strings.TrimSpace(s), 10, 64)
+					if err != nil || mb < 0 {
+						m.msg = warnStyle.Render("invalid number")
+						return
+					}
+					if err := m.svc.SetQuota(uid, mb<<20); err != nil {
+						m.msg = warnStyle.Render(err.Error())
+						return
+					}
+					m.msg = fmt.Sprintf("quota set to %d MB", mb)
+				})
+			}
+		case "x":
+			if u := m.curUser(); u != nil {
+				fa, _ := m.svc.Access(u.ID)
+				if err := m.svc.SetRevoked(u.ID, !fa.Revoked); err != nil {
+					m.msg = warnStyle.Render(err.Error())
+				} else if fa.Revoked {
+					m.msg = "restored SFTP for " + u.Name
+				} else {
+					m.msg = "revoked SFTP for " + u.Name
+				}
+			}
+		}
+	case tabPublic:
+		switch key.String() {
+		case "t":
+			on := !m.svc.PublicWritable()
+			if err := m.svc.SetPublicWrite(on); err != nil {
+				m.msg = warnStyle.Render(err.Error())
+			} else if on {
+				m.msg = "public area is now writable (members)"
+			} else {
+				m.msg = "public area is now read-only"
+			}
+		case "x":
+			if e := m.curPublic(); e != nil {
+				name := e.Name
+				if err := m.svc.PublicRemove(name); err != nil {
+					m.msg = warnStyle.Render(err.Error())
+				} else {
+					m.msg = "removed " + name
+				}
+				m.reload()
+			}
+		}
+	}
+	return m, nil
+}
+
+func (m admin) updateInput(key tea.KeyMsg) (tea.Model, tea.Cmd) {
+	switch key.Type {
+	case tea.KeyEnter:
+		m.input = false
+		if m.onInput != nil {
+			m.onInput(m.buf)
+		}
+		m.buf = ""
+		m.reload()
+	case tea.KeyEsc:
+		m.input, m.buf = false, ""
+	case tea.KeyBackspace:
+		if m.buf != "" {
+			m.buf = m.buf[:len(m.buf)-1]
+		}
+	case tea.KeyRunes, tea.KeySpace:
+		m.buf += string(key.Runes)
+	}
+	return m, nil
+}
+
+func (m *admin) startInput(prompt string, cb func(string)) {
+	m.input, m.prompt, m.buf, m.onInput = true, prompt, "", cb
+}
+
+func (m admin) curSession() *Conn {
+	if m.tab != tabSessions || m.sel >= len(m.sessions) {
+		return nil
+	}
+	return &m.sessions[m.sel]
+}
+func (m admin) curUser() *store.User {
+	if m.tab != tabWorkspaces || m.sel >= len(m.users) {
+		return nil
+	}
+	return &m.users[m.sel]
+}
+func (m admin) curPublic() *Entry {
+	if m.tab != tabPublic || m.sel >= len(m.public) {
+		return nil
+	}
+	return &m.public[m.sel]
+}
+
+func (m admin) View() string {
+	var b strings.Builder
+	b.WriteString(titleStyle.Render("SFTP server — management") + "\n")
+
+	var tabs []string
+	for i, name := range tabNames {
+		if adminTab(i) == m.tab {
+			tabs = append(tabs, selStyle.Render(" "+name+" "))
+		} else {
+			tabs = append(tabs, dimStyle.Render(" "+name+" "))
+		}
+	}
+	b.WriteString(strings.Join(tabs, " ") + "\n\n")
+
+	switch m.tab {
+	case tabSessions:
+		b.WriteString(m.viewSessions())
+	case tabWorkspaces:
+		b.WriteString(m.viewWorkspaces())
+	case tabPublic:
+		b.WriteString(m.viewPublic())
+	}
+
+	b.WriteString("\n")
+	if m.input {
+		b.WriteString(titleStyle.Render(m.prompt) + m.buf + "_\n")
+	} else {
+		if m.msg != "" {
+			b.WriteString(m.msg + "\n")
+		}
+		b.WriteString(dimStyle.Render(m.help()))
+	}
+	return lipgloss.NewStyle().Padding(1, 2).Render(b.String())
+}
+
+func (m admin) help() string {
+	common := "tab switch · ↑/↓ move · g refresh · q quit"
+	switch m.tab {
+	case tabSessions:
+		return "x disconnect · " + common
+	case tabWorkspaces:
+		return "Q set quota · x revoke/restore · " + common
+	case tabPublic:
+		return "t toggle write · x remove entry · " + common
+	}
+	return common
+}
+
+func (m admin) viewSessions() string {
+	if len(m.sessions) == 0 {
+		return dimStyle.Render("  no live SFTP connections")
+	}
+	var b strings.Builder
+	b.WriteString(dimStyle.Render(fmt.Sprintf("  %-16s %-22s %10s %10s %8s\n", "user", "remote", "rx", "tx", "idle")))
+	for i, c := range m.sessions {
+		line := fmt.Sprintf("  %-16s %-22s %10s %10s %8s",
+			c.User, c.Remote, humanBytes(c.RX), humanBytes(c.TX), since(c.Started))
+		b.WriteString(rowStyle(i == m.sel).Render(line) + "\n")
+	}
+	return b.String()
+}
+
+func (m admin) viewWorkspaces() string {
+	if len(m.users) == 0 {
+		return dimStyle.Render("  no members")
+	}
+	var b strings.Builder
+	b.WriteString(dimStyle.Render(fmt.Sprintf("  %-16s %10s %10s %6s %s\n", "user", "used", "quota", "use%", "access")))
+	for i, u := range m.users {
+		usage, _ := m.svc.Usage(u)
+		fa, _ := m.svc.Access(u.ID)
+		access := "ok"
+		if fa.Revoked {
+			access = warnStyle.Render("revoked")
+		}
+		line := fmt.Sprintf("  %-16s %10s %10s %5d%% %s",
+			u.Name, humanBytes(usage.Bytes), humanBytes(usage.Quota), pct(usage.Bytes, usage.Quota), access)
+		b.WriteString(rowStyle(i == m.sel).Render(line) + "\n")
+	}
+	return b.String()
+}
+
+func (m admin) viewPublic() string {
+	state := "writable (members)"
+	if !m.svc.PublicWritable() {
+		state = "read-only"
+	}
+	var b strings.Builder
+	b.WriteString(dimStyle.Render("  public-area write: ") + state + "\n\n")
+	if len(m.public) == 0 {
+		b.WriteString(dimStyle.Render("  (empty)"))
+		return b.String()
+	}
+	for i, e := range m.public {
+		name := e.Name
+		meta := humanBytes(e.Size)
+		if e.IsDir {
+			name += "/"
+			meta = "dir"
+		}
+		b.WriteString(rowStyle(i == m.sel).Render(fmt.Sprintf("  %-28s %8s", name, meta)) + "\n")
+	}
+	return b.String()
+}
+
+func rowStyle(selected bool) lipgloss.Style {
+	if selected {
+		return selStyle
+	}
+	return lipgloss.NewStyle()
+}
+
+func since(t time.Time) string {
+	d := time.Since(t).Round(time.Second)
+	if d < time.Minute {
+		return fmt.Sprintf("%ds", int(d.Seconds()))
+	}
+	if d < time.Hour {
+		return fmt.Sprintf("%dm", int(d.Minutes()))
+	}
+	return fmt.Sprintf("%dh", int(d.Hours()))
+}

internal/files/backend.go

@@ -0,0 +1,317 @@
+// Package files implements member file storage for AgentBBS, reachable over
+// SFTP with the member's existing SSH login key (docs/files.md). It is wired as
+// an "sftp" subsystem on the shared wish server (port 22), so a member runs
+//
+//	sftp files@bbs.profullstack.com
+//
+// and lands in a virtual filesystem with two areas:
+//
+//	/me      — their private, per-user workspace (quota-limited)
+//	/public  — a single shared file area (old-school BBS file area); world-read,
+//	           members-only write by default, operator-moderated.
+//
+// Identity is the SSH public key (one key = one account, like the rest of the
+// BBS); the SFTP username is conventional ("files") and ignored. The server is a
+// fully virtual Go SFTP server (github.com/pkg/sftp) — there are no OS users.
+//
+// Security: every path the client supplies is resolved through resolve() in
+// fs.go, which confines it to its area root (no traversal, no symlink escape);
+// see the path-traversal tests. Per §9.2 the operator can inspect and act on
+// hosted files (the management TUI), and per §9.3 (amended) the only sharing
+// surface is the single public area — there is no workspace-to-workspace
+// transfer.
+package files
+
+import (
+	"io/fs"
+	"os"
+	"path/filepath"
+	"sync"
+	"sync/atomic"
+	"time"
+
+	"github.com/profullstack/agentbbs/internal/store"
+)
+
+// Setting keys persisted in files_settings.
+const (
+	// settingPublicWrite is "members" (default) or "off". When "off", the
+	// shared public area is read-only for everyone (operators moderate via the
+	// management TUI / filesystem).
+	settingPublicWrite = "public_write"
+)
+
+// DefaultQuota is the per-user workspace quota when none is configured.
+const DefaultQuota int64 = 1 << 30 // 1 GiB
+
+// FilesStore is the slice of the store the Files service needs.
+type FilesStore interface {
+	UserByFingerprint(fp string) (store.User, bool, error)
+	UserByName(name string) (store.User, bool, error)
+	ListUsers(limit int) ([]store.User, error)
+	FilesAccess(userID int64) (store.FilesAccess, error)
+	SetFilesQuota(userID, bytes int64) error
+	SetFilesRevoked(userID int64, revoked bool) error
+	FilesSetting(key string) (string, bool, error)
+	SetFilesSetting(key, value string) error
+}
+
+// Config configures the Files service.
+type Config struct {
+	// Root is the storage root, e.g. <dataDir>/files. The service owns
+	// <Root>/users/<name> (private) and <Root>/public (shared).
+	Root string
+	// DefaultQuota is the per-user workspace quota in bytes (0 → DefaultQuota).
+	DefaultQuota int64
+}
+
+// Service is the shared Files engine: one instance backs the SFTP subsystem,
+// the in-BBS browser, and the operator management TUI.
+type Service struct {
+	st  FilesStore
+	cfg Config
+	reg *registry
+}
+
+// New builds a Files service and ensures the storage layout exists.
+func New(st FilesStore, cfg Config) (*Service, error) {
+	if cfg.DefaultQuota <= 0 {
+		cfg.DefaultQuota = DefaultQuota
+	}
+	cfg.Root = filepath.Clean(cfg.Root)
+	for _, d := range []string{cfg.Root, filepath.Join(cfg.Root, "users"), filepath.Join(cfg.Root, "public")} {
+		if err := os.MkdirAll(d, 0o755); err != nil {
+			return nil, err
+		}
+	}
+	return &Service{st: st, cfg: cfg, reg: newRegistry()}, nil
+}
+
+// privRoot is the absolute private-workspace directory for a member.
+func (s *Service) privRoot(user string) string {
+	return filepath.Join(s.cfg.Root, "users", user)
+}
+
+// pubRoot is the absolute shared public-area directory.
+func (s *Service) pubRoot() string { return filepath.Join(s.cfg.Root, "public") }
+
+// ensureWorkspace creates a member's private workspace if absent.
+func (s *Service) ensureWorkspace(user string) error {
+	return os.MkdirAll(s.privRoot(user), 0o700)
+}
+
+// quotaFor returns the effective quota (bytes) for a user: their per-user
+// override if set, else the server default.
+func (s *Service) quotaFor(userID int64) int64 {
+	if fa, err := s.st.FilesAccess(userID); err == nil && fa.QuotaBytes > 0 {
+		return fa.QuotaBytes
+	}
+	return s.cfg.DefaultQuota
+}
+
+// publicWritable reports whether members may write to the shared area. The
+// persisted files_settings value wins; default is true (members-only write).
+func (s *Service) publicWritable() bool {
+	if v, ok, err := s.st.FilesSetting(settingPublicWrite); err == nil && ok {
+		return v != "off"
+	}
+	return true
+}
+
+// SetPublicWrite toggles members' write access to the shared public area.
+func (s *Service) SetPublicWrite(on bool) error {
+	v := "off"
+	if on {
+		v = "members"
+	}
+	return s.st.SetFilesSetting(settingPublicWrite, v)
+}
+
+// dirSize returns the total bytes used under root (regular files only; symlinks
+// are not followed). A missing root counts as 0.
+func dirSize(root string) (int64, error) {
+	var total int64
+	err := filepath.WalkDir(root, func(_ string, d fs.DirEntry, err error) error {
+		if err != nil {
+			if os.IsNotExist(err) {
+				return nil
+			}
+			return err
+		}
+		if d.Type().IsRegular() {
+			info, err := d.Info()
+			if err != nil {
+				if os.IsNotExist(err) {
+					return nil
+				}
+				return err
+			}
+			total += info.Size()
+		}
+		return nil
+	})
+	if os.IsNotExist(err) {
+		return 0, nil
+	}
+	return total, err
+}
+
+// Usage is a member's workspace usage snapshot.
+type Usage struct {
+	Bytes int64
+	Quota int64
+}
+
+// Free reports remaining bytes (never negative).
+func (u Usage) Free() int64 {
+	if u.Quota <= u.Bytes {
+		return 0
+	}
+	return u.Quota - u.Bytes
+}
+
+// Usage computes a member's private-workspace usage against their quota.
+func (s *Service) Usage(u store.User) (Usage, error) {
+	used, err := dirSize(s.privRoot(u.Name))
+	if err != nil {
+		return Usage{}, err
+	}
+	return Usage{Bytes: used, Quota: s.quotaFor(u.ID)}, nil
+}
+
+// --- live session registry (for the management TUI's Sessions pane) ----------
+
+// Conn is a snapshot of a live SFTP connection, as shown by the management TUI.
+type Conn struct {
+	ID      int64
+	User    string
+	Key     string // SSH key fingerprint
+	Remote  string
+	Started time.Time
+	RX      int64 // bytes received from the client (uploads)
+	TX      int64 // bytes sent to the client (downloads)
+}
+
+// liveConn is the registry's mutable view of an active connection. Its atomic
+// counters are updated by countingRWC; snapshots copy out plain Conn values.
+type liveConn struct {
+	id      int64
+	user    string
+	key     string
+	remote  string
+	started time.Time
+	rxBytes atomic.Int64
+	txBytes atomic.Int64
+	closer  func() error
+}
+
+type registry struct {
+	mu   sync.Mutex
+	next int64
+	live map[int64]*liveConn
+}
+
+func newRegistry() *registry { return &registry{live: map[int64]*liveConn{}} }
+
+func (r *registry) add(user, key, remote string, closer func() error) *liveConn {
+	r.mu.Lock()
+	defer r.mu.Unlock()
+	r.next++
+	c := &liveConn{id: r.next, user: user, key: key, remote: remote, started: time.Now(), closer: closer}
+	r.live[c.id] = c
+	return c
+}
+
+func (r *registry) remove(id int64) {
+	r.mu.Lock()
+	defer r.mu.Unlock()
+	delete(r.live, id)
+}
+
+func (r *registry) snapshot() []Conn {
+	r.mu.Lock()
+	defer r.mu.Unlock()
+	out := make([]Conn, 0, len(r.live))
+	for _, c := range r.live {
+		out = append(out, Conn{
+			ID: c.id, User: c.user, Key: c.key, Remote: c.remote, Started: c.started,
+			RX: c.rxBytes.Load(), TX: c.txBytes.Load(),
+		})
+	}
+	return out
+}
+
+// Sessions returns a snapshot of live SFTP connections, newest first.
+func (s *Service) Sessions() []Conn {
+	cs := s.reg.snapshot()
+	for i, j := 0, len(cs)-1; i < j; i, j = i+1, j-1 {
+		cs[i], cs[j] = cs[j], cs[i]
+	}
+	return cs
+}
+
+// --- operator / management surface ------------------------------------------
+
+// Users lists accounts for the management TUI (newest first).
+func (s *Service) Users() ([]store.User, error) { return s.st.ListUsers(10000) }
+
+// Access returns a user's SFTP access record (quota override + revoked flag).
+func (s *Service) Access(userID int64) (store.FilesAccess, error) {
+	return s.st.FilesAccess(userID)
+}
+
+// SetQuota sets a per-user quota override (bytes; 0 = server default).
+func (s *Service) SetQuota(userID, bytes int64) error { return s.st.SetFilesQuota(userID, bytes) }
+
+// SetRevoked revokes/restores a user's SFTP access (BBS login is unaffected).
+func (s *Service) SetRevoked(userID int64, revoked bool) error {
+	return s.st.SetFilesRevoked(userID, revoked)
+}
+
+// PublicWritable reports whether members may currently write to the public area.
+func (s *Service) PublicWritable() bool { return s.publicWritable() }
+
+// PublicList lists the top level of the shared public area for moderation.
+func (s *Service) PublicList() ([]Entry, error) {
+	des, err := os.ReadDir(s.pubRoot())
+	if err != nil {
+		return nil, err
+	}
+	out := make([]Entry, 0, len(des))
+	for _, de := range des {
+		fi, err := de.Info()
+		if err != nil {
+			continue
+		}
+		out = append(out, Entry{Name: de.Name(), IsDir: de.IsDir(), Size: fi.Size(), ModTime: fi.ModTime()})
+	}
+	return out, nil
+}
+
+// PublicRemove deletes a top-level entry from the public area (moderation). name
+// is treated as a single segment; traversal is rejected.
+func (s *Service) PublicRemove(name string) error {
+	base := filepath.Base(filepath.Clean("/" + name))
+	if base == "." || base == "/" || base == ".." {
+		return os.ErrInvalid
+	}
+	target := filepath.Join(s.pubRoot(), base)
+	if !within(s.pubRoot(), target) {
+		return os.ErrPermission
+	}
+	return os.RemoveAll(target)
+}
+
+// Kick force-disconnects a live SFTP connection by id. Returns false if unknown.
+func (s *Service) Kick(id int64) bool {
+	s.reg.mu.Lock()
+	c, ok := s.reg.live[id]
+	s.reg.mu.Unlock()
+	if !ok {
+		return false
+	}
+	if c.closer != nil {
+		_ = c.closer()
+	}
+	return true
+}

internal/files/e2e_test.go

@@ -0,0 +1,87 @@
+package files
+
+import (
+	"io"
+	"net"
+	"sort"
+	"testing"
+
+	"github.com/pkg/sftp"
+)
+
+// startE2E wires a real sftp client to the request server for one member, over
+// an in-memory pipe (no SSH transport).
+func startE2E(t *testing.T) *sftp.Client {
+	t.Helper()
+	svc, _, u := newTestService(t)
+	sess, err := svc.newSession(u)
+	if err != nil {
+		t.Fatal(err)
+	}
+	srvConn, cliConn := net.Pipe()
+	handlers := sftp.Handlers{FileGet: sess, FilePut: sess, FileCmd: sess, FileList: sess}
+	server := sftp.NewRequestServer(srvConn, handlers)
+	go func() { _ = server.Serve() }()
+	client, err := sftp.NewClientPipe(cliConn, cliConn)
+	if err != nil {
+		t.Fatalf("NewClientPipe: %v", err)
+	}
+	t.Cleanup(func() { _ = client.Close(); _ = server.Close() })
+	return client
+}
+
+func TestE2E_RootListing(t *testing.T) {
+	client := startE2E(t)
+	infos, err := client.ReadDir("/")
+	if err != nil {
+		t.Fatalf("ReadDir /: %v", err)
+	}
+	var names []string
+	for _, fi := range infos {
+		names = append(names, fi.Name())
+	}
+	sort.Strings(names)
+	if len(names) != 2 || names[0] != "me" || names[1] != "public" {
+		t.Errorf("root listing = %v, want [me public]", names)
+	}
+}
+
+func TestE2E_UploadDownloadPrivate(t *testing.T) {
+	client := startE2E(t)
+	f, err := client.Create("/me/hello.txt")
+	if err != nil {
+		t.Fatalf("Create: %v", err)
+	}
+	if _, err := f.Write([]byte("hello bbs")); err != nil {
+		t.Fatalf("Write: %v", err)
+	}
+	if err := f.Close(); err != nil {
+		t.Fatalf("Close: %v", err)
+	}
+
+	rf, err := client.Open("/me/hello.txt")
+	if err != nil {
+		t.Fatalf("Open: %v", err)
+	}
+	defer rf.Close()
+	got, err := io.ReadAll(rf)
+	if err != nil {
+		t.Fatalf("ReadAll: %v", err)
+	}
+	if string(got) != "hello bbs" {
+		t.Errorf("read = %q, want %q", got, "hello bbs")
+	}
+}
+
+func TestE2E_TraversalDenied(t *testing.T) {
+	client := startE2E(t)
+	// A normalizing client may collapse "/me/../.." to "/" before sending, so
+	// the guarantee we assert is the negative one: no escape ever yields a
+	// handle onto a system path.
+	if _, err := client.Open("/me/../../../../etc/passwd"); err == nil {
+		t.Error("opening an escaping path should fail")
+	}
+	if _, err := client.Open("/etc/passwd"); err == nil {
+		t.Error("opening an unknown area should fail")
+	}
+}

internal/files/files_test.go

@@ -0,0 +1,187 @@
+package files
+
+import (
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+
+	"github.com/pkg/sftp"
+	"github.com/profullstack/agentbbs/internal/store"
+)
+
+func newTestService(t *testing.T) (*Service, store.Store, store.User) {
+	t.Helper()
+	dir := t.TempDir()
+	st, err := store.Open(filepath.Join(dir, "test.db"))
+	if err != nil {
+		t.Fatalf("store.Open: %v", err)
+	}
+	t.Cleanup(func() { _ = st.Close() })
+	svc, err := New(st, Config{Root: filepath.Join(dir, "files"), DefaultQuota: 1 << 20})
+	if err != nil {
+		t.Fatalf("New: %v", err)
+	}
+	u, err := st.EnsureUser("alice", "member", "SHA256:alicekey")
+	if err != nil {
+		t.Fatalf("EnsureUser: %v", err)
+	}
+	return svc, st, u
+}
+
+func TestResolveConfinement(t *testing.T) {
+	svc, _, u := newTestService(t)
+	sess, err := svc.newSession(u)
+	if err != nil {
+		t.Fatal(err)
+	}
+	priv := svc.privRoot(u.Name)
+	pub := svc.pubRoot()
+
+	// These must never resolve to a path outside their area root. Some are
+	// expected to error outright; for the rest, assert containment.
+	escapes := []string{
+		"/me/../../../etc/passwd",
+		"/me/../../etc",
+		"/me/sub/../../../../etc/shadow",
+		"/public/../me/secret",
+		"/public/../../etc",
+		"/../etc/passwd",
+		"/me/./../../public/../../root",
+	}
+	for _, p := range escapes {
+		res, err := sess.resolve(p)
+		if err != nil {
+			continue // rejected outright — fine
+		}
+		if res.root {
+			continue // collapsed to the synthetic root — fine
+		}
+		ok := within(priv, res.real) || within(pub, res.real)
+		if !ok {
+			t.Errorf("resolve(%q) escaped: %q (priv=%q pub=%q)", p, res.real, priv, pub)
+		}
+	}
+}
+
+func TestResolveAreas(t *testing.T) {
+	svc, _, u := newTestService(t)
+	sess, _ := svc.newSession(u)
+
+	root, _ := sess.resolve("/")
+	if !root.root {
+		t.Error("/ should be the synthetic root")
+	}
+	me, err := sess.resolve("/me/notes.txt")
+	if err != nil || me.area != areaMe || !me.writable {
+		t.Errorf("/me should be writable me-area: %+v err=%v", me, err)
+	}
+	if !within(svc.privRoot(u.Name), me.real) {
+		t.Errorf("/me path %q not under priv root", me.real)
+	}
+	pub, err := sess.resolve("/public/shared.txt")
+	if err != nil || pub.area != areaPublic {
+		t.Errorf("/public should be public area: %+v err=%v", pub, err)
+	}
+	if _, err := sess.resolve("/etc/passwd"); err == nil {
+		t.Error("unknown top-level area should be rejected")
+	}
+}
+
+func TestSymlinkEscapeBlocked(t *testing.T) {
+	svc, _, u := newTestService(t)
+	sess, _ := svc.newSession(u)
+	priv := svc.privRoot(u.Name)
+
+	// Plant a symlink inside the workspace pointing at the system root.
+	link := filepath.Join(priv, "escape")
+	if err := os.Symlink("/etc", link); err != nil {
+		t.Skipf("symlink unsupported: %v", err)
+	}
+	if _, err := sess.resolve("/me/escape/passwd"); err == nil {
+		t.Error("path through an escaping symlink must be rejected")
+	}
+}
+
+func TestPublicWriteACL(t *testing.T) {
+	svc, st, u := newTestService(t)
+
+	// Default: members may write to the public area.
+	sess, _ := svc.newSession(u)
+	r := sftp.NewRequest("Mkdir", "/public/uploads")
+	if err := sess.Filecmd(r); err != nil {
+		t.Fatalf("public mkdir should succeed by default: %v", err)
+	}
+
+	// Turn public write off → writes denied, reads still fine.
+	if err := svc.SetPublicWrite(false); err != nil {
+		t.Fatal(err)
+	}
+	_ = st
+	sess2, _ := svc.newSession(u)
+	if err := sess2.Filecmd(sftp.NewRequest("Mkdir", "/public/more")); err != sftp.ErrSSHFxPermissionDenied {
+		t.Errorf("public write should be denied when off, got %v", err)
+	}
+	res, err := sess2.resolve("/public/uploads")
+	if err != nil || res.writable {
+		t.Errorf("public should resolve read-only when write is off: %+v err=%v", res, err)
+	}
+}
+
+func TestQuotaEnforced(t *testing.T) {
+	svc, _, u := newTestService(t)
+	sess, _ := svc.newSession(u)
+	sess.quota = 100 // tiny
+
+	f, err := os.Create(filepath.Join(svc.privRoot(u.Name), "big"))
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer f.Close()
+	w := &quotaWriter{f: f, sess: sess}
+
+	if _, err := w.WriteAt(make([]byte, 80), 0); err != nil {
+		t.Fatalf("write within quota failed: %v", err)
+	}
+	if _, err := w.WriteAt(make([]byte, 80), 80); err != sftp.ErrSSHFxFailure {
+		t.Errorf("write over quota should fail, got %v", err)
+	}
+}
+
+func TestUsage(t *testing.T) {
+	svc, _, u := newTestService(t)
+	if err := svc.ensureWorkspace(u.Name); err != nil {
+		t.Fatal(err)
+	}
+	want := []byte(strings.Repeat("x", 512))
+	if err := os.WriteFile(filepath.Join(svc.privRoot(u.Name), "a.txt"), want, 0o644); err != nil {
+		t.Fatal(err)
+	}
+	usage, err := svc.Usage(u)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if usage.Bytes != 512 {
+		t.Errorf("usage = %d, want 512", usage.Bytes)
+	}
+	if usage.Quota != 1<<20 {
+		t.Errorf("quota = %d, want default", usage.Quota)
+	}
+}
+
+func TestRevokeBlocksAndQuotaOverride(t *testing.T) {
+	svc, st, u := newTestService(t)
+	if err := st.SetFilesQuota(u.ID, 4096); err != nil {
+		t.Fatal(err)
+	}
+	if got := svc.quotaFor(u.ID); got != 4096 {
+		t.Errorf("quotaFor = %d, want 4096 override", got)
+	}
+	if err := st.SetFilesRevoked(u.ID, true); err != nil {
+		t.Fatal(err)
+	}
+	fa, err := st.FilesAccess(u.ID)
+	if err != nil || !fa.Revoked {
+		t.Errorf("FilesAccess revoked = %+v err=%v", fa, err)
+	}
+}

internal/files/fs.go

@@ -0,0 +1,470 @@
+package files
+
+import (
+	"errors"
+	"io"
+	"os"
+	"path"
+	"path/filepath"
+	"sort"
+	"strings"
+	"sync/atomic"
+	"time"
+
+	"github.com/pkg/sftp"
+	"github.com/profullstack/agentbbs/internal/store"
+)
+
+// area names exposed at the virtual root.
+const (
+	areaMe     = "me"
+	areaPublic = "public"
+)
+
+// errEscape is returned when a resolved path would leave its area root. It maps
+// to an SFTP permission-denied; it must never reach the client as a real path.
+var errEscape = errors.New("files: path escapes its area")
+
+// session is one member's view of the filesystem for the life of an SFTP
+// connection. It implements the pkg/sftp request handlers and enforces area
+// confinement, the public-area ACL, and the per-user quota.
+type session struct {
+	svc      *Service
+	user     store.User
+	pubWrite bool
+	quota    int64
+	used     atomic.Int64 // live private-workspace usage, for quota checks
+}
+
+func (s *Service) newSession(u store.User) (*session, error) {
+	if err := s.ensureWorkspace(u.Name); err != nil {
+		return nil, err
+	}
+	used, err := dirSize(s.privRoot(u.Name))
+	if err != nil {
+		return nil, err
+	}
+	sess := &session{svc: s, user: u, pubWrite: s.publicWritable(), quota: s.quotaFor(u.ID)}
+	sess.used.Store(used)
+	return sess, nil
+}
+
+// resolved is the outcome of mapping a client (virtual) path to disk.
+type resolved struct {
+	real     string // absolute on-disk path ("" for the synthetic root)
+	area     string // "", areaMe, or areaPublic
+	root     bool   // the synthetic "/" listing me + public
+	writable bool   // whether this area accepts writes for this member
+}
+
+// resolve maps a client path to disk, confined to its area root. It rejects any
+// path that escapes (lexically or via an existing symlink). This is the single
+// security chokepoint — every handler goes through it.
+func (s *session) resolve(p string) (resolved, error) {
+	clean := path.Clean("/" + strings.TrimSpace(p))
+	if clean == "/" || clean == "." {
+		return resolved{root: true}, nil
+	}
+	seg := strings.SplitN(strings.TrimPrefix(clean, "/"), "/", 2)
+	rest := ""
+	if len(seg) == 2 {
+		rest = seg[1]
+	}
+	var areaRoot, area string
+	writable := false
+	switch seg[0] {
+	case areaMe:
+		areaRoot, area, writable = s.svc.privRoot(s.user.Name), areaMe, true
+	case areaPublic:
+		areaRoot, area, writable = s.svc.pubRoot(), areaPublic, s.pubWrite
+	default:
+		return resolved{}, os.ErrNotExist
+	}
+	real, err := safeJoin(areaRoot, rest)
+	if err != nil {
+		return resolved{}, err
+	}
+	return resolved{real: real, area: area, writable: writable}, nil
+}
+
+// safeJoin joins rel onto root and verifies the result stays within root, both
+// lexically and after resolving any symlinks that already exist on the path.
+func safeJoin(root, rel string) (string, error) {
+	full := filepath.Join(root, filepath.FromSlash(rel))
+	full = filepath.Clean(full)
+	if !within(root, full) {
+		return "", errEscape
+	}
+	// Symlink guard: resolve the longest existing prefix and re-check. This
+	// catches a symlink (created out-of-band) that points outside the area.
+	probe := full
+	for {
+		if resolvedPath, err := filepath.EvalSymlinks(probe); err == nil {
+			if !within(root, resolvedPath) {
+				return "", errEscape
+			}
+			break
+		}
+		parent := filepath.Dir(probe)
+		if parent == probe {
+			break
+		}
+		probe = parent
+	}
+	return full, nil
+}
+
+// within reports whether p is root itself or lives under it.
+func within(root, p string) bool {
+	if p == root {
+		return true
+	}
+	return strings.HasPrefix(p, root+string(os.PathSeparator))
+}
+
+// OpenFor builds a member session by account name, for the in-BBS browser. It
+// returns the resolved store user too.
+func (s *Service) OpenFor(name string) (*session, store.User, error) {
+	u, ok, err := s.st.UserByName(name)
+	if err != nil {
+		return nil, store.User{}, err
+	}
+	if !ok {
+		return nil, store.User{}, os.ErrNotExist
+	}
+	sess, err := s.newSession(u)
+	return sess, u, err
+}
+
+// Entry is a directory entry for the in-BBS browser.
+type Entry struct {
+	Name    string
+	IsDir   bool
+	Size    int64
+	ModTime time.Time
+}
+
+// entries lists a virtual directory for the browser, with the synthetic root
+// showing the two areas. Directories sort before files, then by name.
+func (s *session) entries(vpath string) ([]Entry, error) {
+	res, err := s.resolve(vpath)
+	if err != nil {
+		return nil, err
+	}
+	if res.root {
+		return []Entry{{Name: areaMe, IsDir: true}, {Name: areaPublic, IsDir: true}}, nil
+	}
+	des, err := os.ReadDir(res.real)
+	if err != nil {
+		return nil, err
+	}
+	out := make([]Entry, 0, len(des))
+	for _, de := range des {
+		fi, err := de.Info()
+		if err != nil {
+			continue
+		}
+		out = append(out, Entry{Name: de.Name(), IsDir: de.IsDir(), Size: fi.Size(), ModTime: fi.ModTime()})
+	}
+	sort.Slice(out, func(i, j int) bool {
+		if out[i].IsDir != out[j].IsDir {
+			return out[i].IsDir
+		}
+		return out[i].Name < out[j].Name
+	})
+	return out, nil
+}
+
+// canWrite reports whether the area containing vpath accepts writes.
+func (s *session) canWrite(vpath string) bool {
+	res, err := s.resolve(vpath)
+	return err == nil && !res.root && res.writable
+}
+
+func (s *session) mkdir(vpath string) error {
+	res, err := s.resolve(vpath)
+	if err != nil {
+		return err
+	}
+	if res.root || !res.writable {
+		return os.ErrPermission
+	}
+	return os.Mkdir(res.real, 0o755)
+}
+
+// remove deletes a file or directory (recursively) within a writable area.
+func (s *session) remove(vpath string) error {
+	res, err := s.resolve(vpath)
+	if err != nil {
+		return err
+	}
+	if res.root || !res.writable {
+		return os.ErrPermission
+	}
+	return os.RemoveAll(res.real)
+}
+
+// rename moves within a single writable area (no cross-area moves).
+func (s *session) rename(oldv, newv string) error {
+	src, err := s.resolve(oldv)
+	if err != nil {
+		return err
+	}
+	dst, err := s.resolve(newv)
+	if err != nil {
+		return err
+	}
+	if src.root || dst.root || !src.writable || !dst.writable || src.area != dst.area {
+		return os.ErrPermission
+	}
+	return os.Rename(src.real, dst.real)
+}
+
+// readFile returns up to max bytes of a file for in-TUI viewing; truncated is
+// true if the file was longer.
+func (s *session) readFile(vpath string, max int64) (data []byte, truncated bool, err error) {
+	res, err := s.resolve(vpath)
+	if err != nil {
+		return nil, false, err
+	}
+	if res.root {
+		return nil, false, os.ErrInvalid
+	}
+	f, err := os.Open(res.real)
+	if err != nil {
+		return nil, false, err
+	}
+	defer f.Close()
+	buf := make([]byte, max+1)
+	n, err := io.ReadFull(f, buf)
+	if err != nil && err != io.EOF && err != io.ErrUnexpectedEOF {
+		return nil, false, err
+	}
+	if int64(n) > max {
+		return buf[:max], true, nil
+	}
+	return buf[:n], false, nil
+}
+
+// --- pkg/sftp request handlers ----------------------------------------------
+
+// Fileread serves downloads.
+func (s *session) Fileread(r *sftp.Request) (io.ReaderAt, error) {
+	res, err := s.resolve(r.Filepath)
+	if err != nil {
+		return nil, sftpErr(err)
+	}
+	if res.root {
+		return nil, sftp.ErrSSHFxOpUnsupported
+	}
+	f, err := os.Open(res.real)
+	if err != nil {
+		return nil, sftpErr(err)
+	}
+	return f, nil
+}
+
+// Filewrite serves uploads, enforcing the per-user quota in the private area.
+func (s *session) Filewrite(r *sftp.Request) (io.WriterAt, error) {
+	res, err := s.resolve(r.Filepath)
+	if err != nil {
+		return nil, sftpErr(err)
+	}
+	if res.root || !res.writable {
+		return nil, sftp.ErrSSHFxPermissionDenied
+	}
+	var startSize int64
+	if fi, err := os.Stat(res.real); err == nil {
+		startSize = fi.Size()
+	}
+	f, err := os.OpenFile(res.real, fileFlags(r.Pflags()), 0o644)
+	if err != nil {
+		return nil, sftpErr(err)
+	}
+	// The public area is operator-managed (no per-user quota); the private
+	// workspace is metered.
+	if res.area != areaMe {
+		return f, nil
+	}
+	return &quotaWriter{f: f, sess: s, tracked: startSize}, nil
+}
+
+// Filecmd handles mutating operations other than read/write.
+func (s *session) Filecmd(r *sftp.Request) error {
+	res, err := s.resolve(r.Filepath)
+	if err != nil {
+		return sftpErr(err)
+	}
+	if res.root || !res.writable {
+		return sftp.ErrSSHFxPermissionDenied
+	}
+	switch r.Method {
+	case "Mkdir":
+		return sftpErr(os.Mkdir(res.real, 0o755))
+	case "Rmdir":
+		return sftpErr(os.Remove(res.real))
+	case "Remove":
+		return sftpErr(os.Remove(res.real))
+	case "Setstat":
+		return s.setstat(res.real, r)
+	case "Rename":
+		dst, err := s.resolve(r.Target)
+		if err != nil {
+			return sftpErr(err)
+		}
+		if dst.root || !dst.writable || dst.area != res.area {
+			// Renames stay within one writable area — no cross-area (and so no
+			// workspace-to-workspace) moves.
+			return sftp.ErrSSHFxPermissionDenied
+		}
+		return sftpErr(os.Rename(res.real, dst.real))
+	case "Symlink", "Link":
+		// No symlinks/hardlinks: they are an escape vector and have no place in
+		// a metered virtual workspace.
+		return sftp.ErrSSHFxOpUnsupported
+	default:
+		return sftp.ErrSSHFxOpUnsupported
+	}
+}
+
+func (s *session) setstat(real string, r *sftp.Request) error {
+	a := r.Attributes()
+	if a.Size != 0 || r.AttrFlags().Size {
+		if err := os.Truncate(real, int64(a.Size)); err != nil {
+			return sftpErr(err)
+		}
+	}
+	if r.AttrFlags().Permissions {
+		if err := os.Chmod(real, a.FileMode().Perm()); err != nil {
+			return sftpErr(err)
+		}
+	}
+	return nil
+}
+
+// Filelist handles List (readdir), Stat, and Readlink.
+func (s *session) Filelist(r *sftp.Request) (sftp.ListerAt, error) {
+	res, err := s.resolve(r.Filepath)
+	if err != nil {
+		return nil, sftpErr(err)
+	}
+	switch r.Method {
+	case "List":
+		if res.root {
+			return listerAt{dirInfo(areaMe), dirInfo(areaPublic)}, nil
+		}
+		entries, err := os.ReadDir(res.real)
+		if err != nil {
+			return nil, sftpErr(err)
+		}
+		infos := make([]os.FileInfo, 0, len(entries))
+		for _, e := range entries {
+			fi, err := e.Info()
+			if err != nil {
+				continue
+			}
+			infos = append(infos, fi)
+		}
+		return listerAt(infos), nil
+	case "Stat":
+		if res.root {
+			return listerAt{dirInfo("/")}, nil
+		}
+		fi, err := os.Stat(res.real)
+		if err != nil {
+			return nil, sftpErr(err)
+		}
+		return listerAt{fi}, nil
+	case "Readlink":
+		return nil, sftp.ErrSSHFxOpUnsupported
+	default:
+		return nil, sftp.ErrSSHFxOpUnsupported
+	}
+}
+
+// --- helpers ----------------------------------------------------------------
+
+// quotaWriter wraps an *os.File and fails writes that would push the member's
+// private workspace over quota. It is conservative: it counts the high-water
+// mark of each file and never decrements live usage (recomputed next session).
+type quotaWriter struct {
+	f       *os.File
+	sess    *session
+	tracked int64 // current accounted size of this file
+}
+
+func (w *quotaWriter) WriteAt(p []byte, off int64) (int, error) {
+	end := off + int64(len(p))
+	if end > w.tracked {
+		delta := end - w.tracked
+		if w.sess.used.Add(delta) > w.sess.quota {
+			w.sess.used.Add(-delta)
+			return 0, sftp.ErrSSHFxFailure // "quota exceeded"
+		}
+		w.tracked = end
+	}
+	return w.f.WriteAt(p, off)
+}
+
+func (w *quotaWriter) Close() error { return w.f.Close() }
+
+// fileFlags maps SFTP open flags to os.OpenFile flags for writes.
+func fileFlags(f sftp.FileOpenFlags) int {
+	flags := os.O_WRONLY
+	if f.Creat {
+		flags |= os.O_CREATE
+	}
+	if f.Trunc {
+		flags |= os.O_TRUNC
+	}
+	if f.Append {
+		flags |= os.O_APPEND
+	}
+	if f.Excl {
+		flags |= os.O_EXCL
+	}
+	return flags
+}
+
+// sftpErr translates an OS/internal error into the SFTP status a client should
+// see, without leaking real paths. nil passes through.
+func sftpErr(err error) error {
+	switch {
+	case err == nil:
+		return nil
+	case errors.Is(err, errEscape):
+		return sftp.ErrSSHFxPermissionDenied
+	case errors.Is(err, os.ErrNotExist):
+		return sftp.ErrSSHFxNoSuchFile
+	case errors.Is(err, os.ErrPermission):
+		return sftp.ErrSSHFxPermissionDenied
+	case errors.Is(err, os.ErrExist):
+		return sftp.ErrSSHFxFailure
+	default:
+		return sftp.ErrSSHFxFailure
+	}
+}
+
+// listerAt adapts a slice of FileInfo to sftp.ListerAt.
+type listerAt []os.FileInfo
+
+func (l listerAt) ListAt(dst []os.FileInfo, off int64) (int, error) {
+	if off >= int64(len(l)) {
+		return 0, io.EOF
+	}
+	n := copy(dst, l[off:])
+	if int(off)+n >= len(l) {
+		return n, io.EOF
+	}
+	return n, nil
+}
+
+// dirInfo is a synthetic directory FileInfo for the virtual-root entries.
+type dirInfo string
+
+func (d dirInfo) Name() string     { return string(d) }
+func (dirInfo) Size() int64        { return 0 }
+func (dirInfo) Mode() os.FileMode  { return os.ModeDir | 0o555 }
+func (dirInfo) ModTime() time.Time { return time.Time{} }
+func (dirInfo) IsDir() bool        { return true }
+func (dirInfo) Sys() any           { return nil }

internal/files/server.go

@@ -0,0 +1,94 @@
+package files
+
+import (
+	"io"
+
+	"github.com/charmbracelet/ssh"
+	"github.com/pkg/sftp"
+
+	"github.com/profullstack/agentbbs/internal/auth"
+)
+
+// Subsystem returns the wish/ssh "sftp" subsystem handler. Wire it with
+//
+//	wish.WithSubsystem("sftp", svc.Subsystem())
+//
+// so members reach their files over the existing :22 listener. Identity is the
+// connecting SSH key (the username is ignored); access is refused for non-members,
+// banned accounts, and members whose SFTP access an operator has revoked.
+func (s *Service) Subsystem() ssh.SubsystemHandler {
+	return func(sess ssh.Session) {
+		fp := auth.Fingerprint(sess.PublicKey())
+		if fp == "" {
+			io.WriteString(sess.Stderr(), "files: an SSH key is required (try: sftp -i ~/.ssh/id_ed25519 ...)\n")
+			_ = sess.Exit(1)
+			return
+		}
+		u, ok, err := s.st.UserByFingerprint(fp)
+		if err != nil {
+			io.WriteString(sess.Stderr(), "files: account lookup failed\n")
+			_ = sess.Exit(1)
+			return
+		}
+		if !ok {
+			io.WriteString(sess.Stderr(), "files: this key isn't a member — register first: ssh join@\n")
+			_ = sess.Exit(1)
+			return
+		}
+		if u.Banned {
+			io.WriteString(sess.Stderr(), "files: this account is suspended\n")
+			_ = sess.Exit(1)
+			return
+		}
+		if fa, err := s.st.FilesAccess(u.ID); err == nil && fa.Revoked {
+			io.WriteString(sess.Stderr(), "files: SFTP access has been revoked for this account\n")
+			_ = sess.Exit(1)
+			return
+		}
+
+		fsSess, err := s.newSession(u)
+		if err != nil {
+			io.WriteString(sess.Stderr(), "files: could not open your workspace\n")
+			_ = sess.Exit(1)
+			return
+		}
+
+		rw := &countingRWC{inner: sess}
+		conn := s.reg.add(u.Name, fp, sess.RemoteAddr().String(), rw.Close)
+		rw.conn = conn
+		defer s.reg.remove(conn.id)
+
+		handlers := sftp.Handlers{FileGet: fsSess, FilePut: fsSess, FileCmd: fsSess, FileList: fsSess}
+		srv := sftp.NewRequestServer(rw, handlers)
+		defer srv.Close()
+		if err := srv.Serve(); err != nil && err != io.EOF {
+			io.WriteString(sess.Stderr(), "files: session ended\n")
+		}
+	}
+}
+
+// countingRWC wraps the SSH channel to meter bytes for the management TUI and to
+// expose Close for force-disconnect. Read = bytes from the client (uploads);
+// Write = bytes to the client (downloads).
+type countingRWC struct {
+	inner io.ReadWriteCloser
+	conn  *liveConn
+}
+
+func (c *countingRWC) Read(p []byte) (int, error) {
+	n, err := c.inner.Read(p)
+	if c.conn != nil {
+		c.conn.rxBytes.Add(int64(n))
+	}
+	return n, err
+}
+
+func (c *countingRWC) Write(p []byte) (int, error) {
+	n, err := c.inner.Write(p)
+	if c.conn != nil {
+		c.conn.txBytes.Add(int64(n))
+	}
+	return n, err
+}
+
+func (c *countingRWC) Close() error { return c.inner.Close() }

internal/files/tui.go

@@ -0,0 +1,358 @@
+package files
+
+import (
+	"fmt"
+	"path"
+	"strings"
+
+	tea "github.com/charmbracelet/bubbletea"
+	"github.com/charmbracelet/lipgloss"
+
+	"github.com/profullstack/agentbbs/internal/auth"
+	"github.com/profullstack/agentbbs/internal/plugin"
+	"github.com/profullstack/agentbbs/internal/store"
+)
+
+// viewMax caps how much of a file the in-BBS viewer loads.
+const viewMax = 64 << 10
+
+var (
+	titleStyle = lipgloss.NewStyle().Bold(true).Foreground(lipgloss.Color("#4ade80"))
+	dimStyle   = lipgloss.NewStyle().Foreground(lipgloss.Color("241"))
+	dirStyle   = lipgloss.NewStyle().Foreground(lipgloss.Color("#60a5fa")).Bold(true)
+	selStyle   = lipgloss.NewStyle().Foreground(lipgloss.Color("0")).Background(lipgloss.Color("#4ade80"))
+	warnStyle  = lipgloss.NewStyle().Foreground(lipgloss.Color("#f87171"))
+)
+
+// NewPlugin returns the in-BBS file browser plugin bound to svc.
+func NewPlugin(svc *Service) plugin.Plugin { return browserPlugin{svc: svc} }
+
+type browserPlugin struct{ svc *Service }
+
+func (browserPlugin) ID() string          { return "files" }
+func (browserPlugin) Title() string       { return "Files" }
+func (browserPlugin) Description() string { return "Your SFTP workspace + the shared public area" }
+func (browserPlugin) RequiresAuth() bool  { return true }
+
+func (p browserPlugin) New(user auth.User, _ plugin.Context) tea.Model {
+	sess, su, err := p.svc.OpenFor(user.Name)
+	m := browser{svc: p.svc, sess: sess, user: su, cwd: "/", host: "bbs.profullstack.com"}
+	if err != nil {
+		m.fatal = "could not open your workspace: " + err.Error()
+		return m
+	}
+	m.reload()
+	return m
+}
+
+type mode int
+
+const (
+	modeBrowse mode = iota
+	modeView
+	modeInput
+	modeConfirm
+)
+
+type browser struct {
+	svc   *Service
+	sess  *session
+	user  store.User
+	host  string
+	cwd   string
+	items []Entry
+	sel   int
+	msg   string
+	fatal string
+
+	mode    mode
+	prompt  string       // input prompt label
+	input   string       // typed text
+	onInput func(string) // committed-input callback
+	confirm string       // confirmation question
+	onYes   func()       // confirmed-action callback
+
+	viewName string
+	viewBody string
+}
+
+func (m *browser) reload() {
+	items, err := m.sess.entries(m.cwd)
+	if err != nil {
+		m.msg = warnStyle.Render("error: " + err.Error())
+		m.items = nil
+		return
+	}
+	m.items = items
+	if m.sel >= len(items) {
+		m.sel = len(items) - 1
+	}
+	if m.sel < 0 {
+		m.sel = 0
+	}
+}
+
+func (m browser) Init() tea.Cmd { return nil }
+
+func (m browser) Update(msg tea.Msg) (tea.Model, tea.Cmd) {
+	key, ok := msg.(tea.KeyMsg)
+	if !ok {
+		return m, nil
+	}
+	if m.fatal != "" {
+		return m, plugin.Exit
+	}
+	switch m.mode {
+	case modeView:
+		m.mode = modeBrowse
+		return m, nil
+	case modeInput:
+		return m.updateInput(key)
+	case modeConfirm:
+		return m.updateConfirm(key)
+	default:
+		return m.updateBrowse(key)
+	}
+}
+
+func (m browser) updateBrowse(key tea.KeyMsg) (tea.Model, tea.Cmd) {
+	switch key.String() {
+	case "q", "esc":
+		return m, plugin.Exit
+	case "up", "k":
+		if m.sel > 0 {
+			m.sel--
+		}
+	case "down", "j":
+		if m.sel < len(m.items)-1 {
+			m.sel++
+		}
+	case "left", "h", "backspace":
+		if m.cwd != "/" {
+			m.cwd = path.Dir(strings.TrimRight(m.cwd, "/"))
+			m.sel = 0
+			m.msg = ""
+			m.reload()
+		}
+	case "enter", "right", "l":
+		return m.open()
+	case "n":
+		if m.sess.canWrite(m.childPath("x")) {
+			m.startInput("new directory name: ", func(name string) {
+				if name = clean(name); name == "" {
+					return
+				}
+				if err := m.sess.mkdir(m.childPath(name)); err != nil {
+					m.msg = warnStyle.Render("mkdir: " + err.Error())
+				} else {
+					m.msg = "created " + name + "/"
+				}
+				m.reload()
+			})
+		} else {
+			m.msg = warnStyle.Render("this area is read-only")
+		}
+	case "r":
+		if cur := m.current(); cur != nil && m.sess.canWrite(m.childPath(cur.Name)) {
+			old := cur.Name
+			m.startInput("rename "+old+" to: ", func(name string) {
+				if name = clean(name); name == "" {
+					return
+				}
+				if err := m.sess.rename(m.childPath(old), m.childPath(name)); err != nil {
+					m.msg = warnStyle.Render("rename: " + err.Error())
+				} else {
+					m.msg = "renamed to " + name
+				}
+				m.reload()
+			})
+		} else {
+			m.msg = warnStyle.Render("nothing to rename here")
+		}
+	case "d":
+		if cur := m.current(); cur != nil && m.sess.canWrite(m.childPath(cur.Name)) {
+			name := cur.Name
+			m.startConfirm("delete "+name+"? (y/n)", func() {
+				if err := m.sess.remove(m.childPath(name)); err != nil {
+					m.msg = warnStyle.Render("delete: " + err.Error())
+				} else {
+					m.msg = "deleted " + name
+				}
+				m.reload()
+			})
+		} else {
+			m.msg = warnStyle.Render("nothing to delete here")
+		}
+	}
+	return m, nil
+}
+
+func (m browser) open() (tea.Model, tea.Cmd) {
+	cur := m.current()
+	if cur == nil {
+		return m, nil
+	}
+	target := m.childPath(cur.Name)
+	if cur.IsDir {
+		m.cwd = target
+		m.sel = 0
+		m.msg = ""
+		m.reload()
+		return m, nil
+	}
+	body, truncated, err := m.sess.readFile(target, viewMax)
+	if err != nil {
+		m.msg = warnStyle.Render("open: " + err.Error())
+		return m, nil
+	}
+	m.viewName = cur.Name
+	m.viewBody = string(body)
+	if truncated {
+		m.viewBody += "\n\n" + dimStyle.Render("… (truncated; download the full file over SFTP)")
+	}
+	m.mode = modeView
+	return m, nil
+}
+
+func (m browser) updateInput(key tea.KeyMsg) (tea.Model, tea.Cmd) {
+	switch key.Type {
+	case tea.KeyEnter:
+		m.mode = modeBrowse
+		if m.onInput != nil {
+			m.onInput(m.input)
+		}
+		m.input = ""
+	case tea.KeyEsc:
+		m.mode = modeBrowse
+		m.input = ""
+	case tea.KeyBackspace:
+		if m.input != "" {
+			m.input = m.input[:len(m.input)-1]
+		}
+	case tea.KeyRunes, tea.KeySpace:
+		m.input += string(key.Runes)
+	}
+	return m, nil
+}
+
+func (m browser) updateConfirm(key tea.KeyMsg) (tea.Model, tea.Cmd) {
+	switch key.String() {
+	case "y", "Y":
+		m.mode = modeBrowse
+		if m.onYes != nil {
+			m.onYes()
+		}
+	case "n", "N", "esc":
+		m.mode = modeBrowse
+		m.msg = "cancelled"
+	}
+	return m, nil
+}
+
+func (m *browser) startInput(prompt string, cb func(string)) {
+	m.mode = modeInput
+	m.prompt = prompt
+	m.input = ""
+	m.onInput = cb
+}
+
+func (m *browser) startConfirm(q string, cb func()) {
+	m.mode = modeConfirm
+	m.confirm = q
+	m.onYes = cb
+}
+
+func (m browser) current() *Entry {
+	if m.sel < 0 || m.sel >= len(m.items) {
+		return nil
+	}
+	return &m.items[m.sel]
+}
+
+func (m browser) childPath(name string) string {
+	return path.Join(m.cwd, name)
+}
+
+func (m browser) View() string {
+	if m.fatal != "" {
+		return lipgloss.NewStyle().Padding(1, 2).Render(warnStyle.Render(m.fatal) + "\n\npress any key to return")
+	}
+	if m.mode == modeView {
+		return lipgloss.NewStyle().Padding(1, 2).Render(
+			titleStyle.Render("Files · "+m.viewName) + "\n\n" + m.viewBody +
+				"\n\n" + dimStyle.Render("press any key to go back"))
+	}
+
+	var b strings.Builder
+	usage, _ := m.svc.Usage(m.user)
+	b.WriteString(titleStyle.Render("Files") + "  " + dimStyle.Render(m.cwd) + "\n")
+	b.WriteString(dimStyle.Render(fmt.Sprintf("workspace: %s / %s  (%d%% used)  ·  transfer: sftp files@%s\n\n",
+		humanBytes(usage.Bytes), humanBytes(usage.Quota), pct(usage.Bytes, usage.Quota), m.host)))
+
+	if len(m.items) == 0 {
+		b.WriteString(dimStyle.Render("  (empty)\n"))
+	}
+	for i, e := range m.items {
+		name := e.Name
+		meta := humanBytes(e.Size)
+		if e.IsDir {
+			name += "/"
+			meta = "dir"
+		}
+		line := fmt.Sprintf("  %-28s %8s", name, meta)
+		switch {
+		case i == m.sel:
+			b.WriteString(selStyle.Render(line))
+		case e.IsDir:
+			b.WriteString(dirStyle.Render(line))
+		default:
+			b.WriteString(line)
+		}
+		b.WriteString("\n")
+	}
+
+	b.WriteString("\n")
+	switch m.mode {
+	case modeInput:
+		b.WriteString(titleStyle.Render(m.prompt) + m.input + "_\n")
+	case modeConfirm:
+		b.WriteString(warnStyle.Render(m.confirm) + "\n")
+	default:
+		if m.msg != "" {
+			b.WriteString(m.msg + "\n")
+		}
+		b.WriteString(dimStyle.Render("↑/↓ move · enter open · n new dir · r rename · d delete · ←/bksp up · q quit"))
+	}
+	return lipgloss.NewStyle().Padding(1, 2).Render(b.String())
+}
+
+// clean trims a user-typed file/dir name to a single safe path segment.
+func clean(s string) string {
+	s = strings.TrimSpace(s)
+	s = strings.ReplaceAll(s, "/", "")
+	if s == "." || s == ".." {
+		return ""
+	}
+	return s
+}
+
+func pct(used, quota int64) int {
+	if quota <= 0 {
+		return 0
+	}
+	return int(used * 100 / quota)
+}
+
+// humanBytes formats a byte count compactly (e.g. 1.5G).
+func humanBytes(n int64) string {
+	const unit = 1024
+	if n < unit {
+		return fmt.Sprintf("%dB", n)
+	}
+	div, exp := int64(unit), 0
+	for x := n / unit; x >= unit; x /= unit {
+		div *= unit
+		exp++
+	}
+	return fmt.Sprintf("%.1f%c", float64(n)/float64(div), "KMGTPE"[exp])
+}

internal/store/store.go

@@ -182,6 +182,23 @@ type Store interface {
 	// per-group number, and returns the stored row (with its number).
 	InsertNewsArticle(a NewsArticle) (NewsArticle, error)
 
+	// Files (SFTP) — per-user workspaces + the shared public area (docs/files.md).
+
+	// FilesAccess returns a user's SFTP access record (per-user quota override
+	// and revoked flag). A user with no row reports the zero value
+	// (QuotaBytes 0 = use the server default, Revoked false).
+	FilesAccess(userID int64) (FilesAccess, error)
+	// SetFilesQuota sets a per-user quota override in bytes (0 clears the
+	// override, falling back to the server default). Idempotent upsert.
+	SetFilesQuota(userID, bytes int64) error
+	// SetFilesRevoked revokes (or restores) a user's SFTP access without
+	// touching their BBS login. Idempotent upsert.
+	SetFilesRevoked(userID int64, revoked bool) error
+	// FilesSetting reads a Files service setting (e.g. the public-write mode).
+	FilesSetting(key string) (string, bool, error)
+	// SetFilesSetting writes a Files service setting. Idempotent upsert.
+	SetFilesSetting(key, value string) error
+
 	Close() error
 }
 
@@ -213,6 +230,14 @@ type NewsArticle struct {
 	CreatedAt time.Time
 }
 
+// FilesAccess is a user's SFTP access record. QuotaBytes is a per-user override
+// (0 means "use the server default"); Revoked blocks SFTP without affecting the
+// BBS login.
+type FilesAccess struct {
+	QuotaBytes int64
+	Revoked    bool
+}
+
 // RatingRow is one ladder entry.
 type RatingRow struct {
 	User   string
@@ -471,6 +496,16 @@ CREATE TABLE IF NOT EXISTS news_articles (
 );
 CREATE INDEX IF NOT EXISTS idx_news_articles_grp ON news_articles(grp, num);
 CREATE INDEX IF NOT EXISTS idx_news_articles_msgid ON news_articles(msg_id);
+CREATE TABLE IF NOT EXISTS files_access (
+  user_id INTEGER PRIMARY KEY,
+  quota_bytes INTEGER NOT NULL DEFAULT 0,
+  revoked INTEGER NOT NULL DEFAULT 0,
+  updated_at TEXT NOT NULL DEFAULT (strftime('%Y-%m-%dT%H:%M:%fZ','now'))
+);
+CREATE TABLE IF NOT EXISTS files_settings (
+  key TEXT PRIMARY KEY,
+  value TEXT NOT NULL DEFAULT ''
+);
 `
 
 func (s *sqliteStore) EnsureUser(name, kind, fp string) (User, error) {
@@ -929,4 +964,65 @@ func (s *sqliteStore) RecordQryptInvite(username, jti string, quota int) error {
 	return tx.Commit()
 }
 
+// --- Files (SFTP) ------------------------------------------------------------
+
+func (s *sqliteStore) FilesAccess(userID int64) (FilesAccess, error) {
+	var fa FilesAccess
+	var revoked int
+	err := s.db.QueryRow(
+		`SELECT quota_bytes, revoked FROM files_access WHERE user_id = ?`, userID,
+	).Scan(&fa.QuotaBytes, &revoked)
+	if errors.Is(err, sql.ErrNoRows) {
+		return FilesAccess{}, nil
+	}
+	if err != nil {
+		return FilesAccess{}, err
+	}
+	fa.Revoked = revoked != 0
+	return fa, nil
+}
+
+func (s *sqliteStore) SetFilesQuota(userID, bytes int64) error {
+	_, err := s.db.Exec(`
+		INSERT INTO files_access (user_id, quota_bytes, updated_at)
+		VALUES (?, ?, strftime('%Y-%m-%dT%H:%M:%fZ','now'))
+		ON CONFLICT(user_id) DO UPDATE SET
+		  quota_bytes = excluded.quota_bytes,
+		  updated_at  = excluded.updated_at`, userID, bytes)
+	return err
+}
+
+func (s *sqliteStore) SetFilesRevoked(userID int64, revoked bool) error {
+	r := 0
+	if revoked {
+		r = 1
+	}
+	_, err := s.db.Exec(`
+		INSERT INTO files_access (user_id, revoked, updated_at)
+		VALUES (?, ?, strftime('%Y-%m-%dT%H:%M:%fZ','now'))
+		ON CONFLICT(user_id) DO UPDATE SET
+		  revoked    = excluded.revoked,
+		  updated_at = excluded.updated_at`, userID, r)
+	return err
+}
+
+func (s *sqliteStore) FilesSetting(key string) (string, bool, error) {
+	var v string
+	err := s.db.QueryRow(`SELECT value FROM files_settings WHERE key = ?`, key).Scan(&v)
+	if errors.Is(err, sql.ErrNoRows) {
+		return "", false, nil
+	}
+	if err != nil {
+		return "", false, err
+	}
+	return v, true, nil
+}
+
+func (s *sqliteStore) SetFilesSetting(key, value string) error {
+	_, err := s.db.Exec(`
+		INSERT INTO files_settings (key, value) VALUES (?, ?)
+		ON CONFLICT(key) DO UPDATE SET value = excluded.value`, key, value)
+	return err
+}
+
 func (s *sqliteStore) Close() error { return s.db.Close() }

setup.sh

@@ -306,6 +306,13 @@ AGENTBBS_NEWS_TLS_KEY=${DATA_DIR}/news-tls/privkey.pem
 # AGENTBBS_NEWS_ADDR=127.0.0.1:1119
 # AGENTBBS_NEWS_TLS_ADDR=:563
 # AGENTBBS_NEWS_GROUPS=pfs.announce:Announcements,pfs.general:General,pfs.agents:Agents
+
+# Files (SFTP): member storage on the same :22 listener (sftp files@${DOMAIN}).
+# Private per-user workspace (/me, quota-limited) + a shared public area
+# (/public). Storage lives under \${AGENTBBS_DATA}/files. Operators manage it via
+# \`ssh sftp@${DOMAIN}\`. Set AGENTBBS_FILES=0 to disable. See docs/files.md.
+# AGENTBBS_FILES=1
+# AGENTBBS_FILES_QUOTA_MB=1024
 ENV
   chmod 0640 "$ENV_DIR/agentbbs.env"
 fi