diff --git a/apps/simplex-support-bot/README.md b/apps/simplex-support-bot/README.md
index 19b9ab8bd6..8e9d244d97 100644
--- a/apps/simplex-support-bot/README.md
+++ b/apps/simplex-support-bot/README.md
@@ -12,30 +12,18 @@ A business-address bot that triages incoming support chats, optionally runs them
 
 ```bash
 cd apps/simplex-support-bot
-npm install      # downloads native libs + transitive deps
+npm install
 npm run build    # tsc
 ```
 
-By default this installs the **SQLite** backend.
+The native library is downloaded on first start into the user cache. To download it ahead of time (for example in a Dockerfile), run as the user that runs the bot:
 
-To use **PostgreSQL** instead, drop a `.npmrc` next to `package.json` *before* `npm install`:
-
-```bash
-echo 'simplex_backend=postgres' > .npmrc
-npm install      # now pulls postgres-flavored native libs
-npm run build
+```sh
+npx simplex-chat install --backend sqlite
+npx simplex-chat install --backend postgres   # Linux x86_64 only
 ```
 
-`.npmrc` lives next to the package — npm reads it natively, no extra setup.
-
-### Switching backends
-
-`npm install` is a no-op for already-installed deps, so editing `.npmrc` and re-running `npm install` will *not* re-trigger `simplex-chat`'s preinstall. To switch backends, force a clean install:
-
-```bash
-rm -rf node_modules
-npm install      # download-libs.js re-runs and pulls the right native lib
-```
+Select the database with `--db sqlite` (default) or `--db postgres`.
 
 ## Run
 
@@ -47,11 +35,9 @@ npm start -- --team-group "Support Team"
 
 # PostgreSQL
 npm start -- --team-group "Support Team" \
-             --pg-conn "postgres://user:pass@host/db"
+             --db postgres --pg-conn "postgres://user:pass@host/db"
 ```
 
-The bot runs via `npm start` so npm can expose `.npmrc` settings to the process — `detectBackend()` reads `npm_config_simplex_backend` to know which backend was installed.
-
 ## Flags
 
 Run `npm start -- --help` for the auto-generated reference. Summary:
@@ -60,6 +46,7 @@ Run `npm start -- --help` for the auto-generated reference. Summary:
 |---|---|---|---|---|
 | `--team-group` | both | yes | — | team group display name |
 | `--state-file` | both | no | `./data/state.json` | path to bot state JSON |
+| `--db` | both | no | `sqlite` | `sqlite` or `postgres` |
 | `--sqlite-file-prefix` | sqlite | no | `./data/simplex` | DB file prefix (creates `<prefix>_chat.db`, `<prefix>_agent.db`) |
 | `--sqlite-key` | sqlite | no | (unencrypted) | SQLCipher encryption key |
 | `--pg-conn` | postgres | yes | — | PostgreSQL connection string |
@@ -76,7 +63,7 @@ Run `npm start -- --help` for the auto-generated reference. Summary:
 | Var | Purpose |
 |---|---|
 | `GROK_API_KEY` | xAI API key; enables Grok replies |
-| `SIMPLEX_BACKEND` | alternative to `.npmrc` for selecting the install backend (`sqlite` or `postgres`) |
+| `SIMPLEX_LIBS_DIR` | directory with a local libsimplex build for the `--db` backend, instead of the downloaded one |
 
 ## Local development against unreleased lib changes
 
@@ -94,8 +81,6 @@ npm link simplex-chat
 
 ## Troubleshooting
 
-- **`--pg-conn is required when backend is postgres`** — the postgres backend is installed but you didn't pass a connection string.
+- **`--pg-conn is required with --db postgres`** — pass a connection string, or use `--db sqlite`.
 - **`libpq5` errors at startup** — install `libpq5` on the host (`apt install libpq5` on Debian/Ubuntu).
 - **`ENOENT: no such file or directory, open './data/state.json'`** — the parent directory of `--state-file` must exist; `mkdir -p data` before starting.
-- **Wrong backend installed** — check `node_modules/simplex-chat/libs/installed.txt`. Edit `.npmrc`, then `rm -rf node_modules && npm install` to switch (`npm install` alone won't re-run the dep's preinstall).
-- **`libpq` connection error** at startup with sqlite-flavored config (or vice versa) — `.npmrc` was changed but libs weren't reinstalled. See "Switching backends" above.
diff --git a/apps/simplex-support-bot/bot.test.ts b/apps/simplex-support-bot/bot.test.ts
index 37521e49dc..a9785de1e3 100644
--- a/apps/simplex-support-bot/bot.test.ts
+++ b/apps/simplex-support-bot/bot.test.ts
@@ -2403,54 +2403,48 @@ describe("parseConfig Validation", () => {
       .toThrow(/--complete-hours must be a non-negative integer, got "abc"/)
   })
 
-  test("postgres backend without --pg-conn → throws", () => {
-    const prev = process.env.SIMPLEX_BACKEND
-    process.env.SIMPLEX_BACKEND = "postgres"
-    try {
-      expect(() => parseConfig(baseArgs))
-        .toThrow(/--pg-conn is required when backend is postgres/)
-    } finally {
-      if (prev === undefined) delete process.env.SIMPLEX_BACKEND
-      else process.env.SIMPLEX_BACKEND = prev
-    }
+  test("--db postgres without --pg-conn → throws", () => {
+    expect(() => parseConfig([...baseArgs, "--db", "postgres"]))
+      .toThrow(/--pg-conn is required with --db postgres/)
   })
 
-  test("postgres backend with --pg-conn → db is postgres DbConfig", () => {
-    const prev = process.env.SIMPLEX_BACKEND
-    process.env.SIMPLEX_BACKEND = "postgres"
-    try {
-      const cfg = parseConfig([...baseArgs, "--pg-conn", "postgres://user:pass@localhost/db"])
-      expect(cfg.db).toEqual({type: "postgres", connectionString: "postgres://user:pass@localhost/db"})
-    } finally {
-      if (prev === undefined) delete process.env.SIMPLEX_BACKEND
-      else process.env.SIMPLEX_BACKEND = prev
-    }
+  test("--db postgres with --pg-conn → db is postgres DbConfig", () => {
+    const cfg = parseConfig([...baseArgs, "--db", "postgres", "--pg-conn", "postgres://user:pass@localhost/db"])
+    expect(cfg.db).toEqual({type: "postgres", connectionString: "postgres://user:pass@localhost/db"})
   })
 
-  test("postgres backend with --pg-schema → DbConfig carries schemaPrefix", () => {
-    const prev = process.env.SIMPLEX_BACKEND
-    process.env.SIMPLEX_BACKEND = "postgres"
-    try {
-      const cfg = parseConfig([...baseArgs, "--pg-conn", "postgres://localhost/db", "--pg-schema", "bot"])
-      expect(cfg.db).toEqual({type: "postgres", connectionString: "postgres://localhost/db", schemaPrefix: "bot"})
-    } finally {
-      if (prev === undefined) delete process.env.SIMPLEX_BACKEND
-      else process.env.SIMPLEX_BACKEND = prev
-    }
+  test("--db postgres with --pg-schema → DbConfig carries schemaPrefix", () => {
+    const cfg = parseConfig([...baseArgs, "--db", "postgres", "--pg-conn", "postgres://localhost/db", "--pg-schema", "bot"])
+    expect(cfg.db).toEqual({type: "postgres", connectionString: "postgres://localhost/db", schemaPrefix: "bot"})
   })
 
-  test("sqlite backend (default) → db is sqlite DbConfig with default filePrefix", () => {
-    const prevBackend = process.env.SIMPLEX_BACKEND
-    const prevNpm = process.env.npm_config_simplex_backend
-    delete process.env.SIMPLEX_BACKEND
-    delete process.env.npm_config_simplex_backend
-    try {
-      const cfg = parseConfig(baseArgs)
-      expect(cfg.db).toEqual({type: "sqlite", filePrefix: "./data/simplex"})
-    } finally {
-      if (prevBackend !== undefined) process.env.SIMPLEX_BACKEND = prevBackend
-      if (prevNpm !== undefined) process.env.npm_config_simplex_backend = prevNpm
-    }
+  test("default --db → sqlite DbConfig with default filePrefix", () => {
+    const cfg = parseConfig(baseArgs)
+    expect(cfg.db).toEqual({type: "sqlite", filePrefix: "./data/simplex"})
+  })
+
+  test("--pg-conn with sqlite → throws", () => {
+    expect(() => parseConfig([...baseArgs, "--pg-conn", "postgres://localhost/db"]))
+      .toThrow(/--pg-conn and --pg-schema require --db postgres/)
+  })
+
+  test("--pg-schema with sqlite → throws", () => {
+    expect(() => parseConfig([...baseArgs, "--pg-schema", "bot"]))
+      .toThrow(/--pg-conn and --pg-schema require --db postgres/)
+  })
+
+  test("--sqlite-key with postgres → throws", () => {
+    expect(() => parseConfig([...baseArgs, "--db", "postgres", "--pg-conn", "c", "--sqlite-key", "k"]))
+      .toThrow(/--sqlite-file-prefix and --sqlite-key require --db sqlite/)
+  })
+
+  test("--sqlite-file-prefix with postgres → throws", () => {
+    expect(() => parseConfig([...baseArgs, "--db", "postgres", "--pg-conn", "c", "--sqlite-file-prefix", "./x"]))
+      .toThrow(/--sqlite-file-prefix and --sqlite-key require --db sqlite/)
+  })
+
+  test("invalid --db → throws", () => {
+    expect(() => parseConfig([...baseArgs, "--db", "mysql"])).toThrow(/Allowed choices are sqlite, postgres/)
   })
 
   test("sqlite backend with --sqlite-key → DbConfig carries encryptionKey", () => {
@@ -2468,18 +2462,6 @@ describe("parseConfig Validation", () => {
       .toThrow(/required option '--team-group/)
   })
 
-  test("invalid SIMPLEX_BACKEND → throws", () => {
-    const prev = process.env.SIMPLEX_BACKEND
-    process.env.SIMPLEX_BACKEND = "mysql"
-    try {
-      expect(() => parseConfig(baseArgs))
-        .toThrow(/Invalid SIMPLEX_BACKEND: "mysql"/)
-    } finally {
-      if (prev === undefined) delete process.env.SIMPLEX_BACKEND
-      else process.env.SIMPLEX_BACKEND = prev
-    }
-  })
-
   test("--complete-hours negative → throws", () => {
     // parseArgs refuses "-1" as a bare arg (ambiguous with a short flag), so use `=` form
     expect(() => parseConfig([...baseArgs, "--complete-hours", "-1"]))
diff --git a/apps/simplex-support-bot/src/config.ts b/apps/simplex-support-bot/src/config.ts
index 8fbd006aef..e180a2279f 100644
--- a/apps/simplex-support-bot/src/config.ts
+++ b/apps/simplex-support-bot/src/config.ts
@@ -1,4 +1,4 @@
-import {Command} from "commander"
+import {Command, Option} from "commander"
 import {api} from "simplex-chat"
 
 export interface IdName {
@@ -6,8 +6,6 @@ export interface IdName {
   name: string
 }
 
-export type Backend = "sqlite" | "postgres"
-
 export interface Config {
   stateFile: string          // local path to the bot's state JSON
   db: api.DbConfig           // passed to ChatApi.init / bot.run
@@ -21,18 +19,6 @@ export interface Config {
   grokApiKey: string | null
 }
 
-// Mirrors packages/simplex-chat-nodejs/src/download-libs.js so runtime detection
-// matches what was used at install time. Works whether the user installed via
-// SIMPLEX_BACKEND env var, .npmrc (→ npm_config_simplex_backend), or the
-// --simplex_backend=postgres CLI flag (also surfaced as npm_config_*).
-export function detectBackend(): Backend {
-  const raw = (process.env.SIMPLEX_BACKEND || process.env.npm_config_simplex_backend || "sqlite").toLowerCase()
-  if (raw !== "sqlite" && raw !== "postgres") {
-    throw new Error(`Invalid SIMPLEX_BACKEND: "${raw}". Must be "sqlite" or "postgres".`)
-  }
-  return raw
-}
-
 export function parseIdName(s: string): IdName {
   const i = s.indexOf(":")
   if (i < 1) throw new Error(`Invalid ID:name format: "${s}"`)
@@ -57,21 +43,23 @@ function buildCommand(): Command {
     .description("business-address triage bot")
     .requiredOption("--team-group <name>", "team group display name")
     .option("--state-file <path>", "state JSON path", "./data/state.json")
+    .addOption(new Option("--db <backend>", "database backend").choices(["sqlite", "postgres"]).default("sqlite"))
     .option("--sqlite-file-prefix <path>", "SQLite DB file prefix", "./data/simplex")
     .option("--sqlite-key <key>", "SQLCipher encryption key (default: unencrypted)")
-    .option("--pg-conn <conn>", "PostgreSQL connection string (required for postgres)")
+    .option("--pg-conn <conn>", "PostgreSQL connection string (required with --db postgres)")
     .option("--pg-schema <prefix>", "PostgreSQL schema prefix (default: simplex_v1)")
     .option("-a, --auto-add-team-members <list>", "comma-separated ID:name pairs (e.g. 1:Alice,2:Bob)")
     .option("--timezone <iana>", "IANA timezone for weekend detection", "UTC")
     .option("--complete-hours <n>", "auto-complete chats after N hours idle (0 disables)", parseNonNegativeInt("--complete-hours"), 3)
     .option("--card-flush-seconds <n>", "debounce card state writes", parseNonNegativeInt("--card-flush-seconds"), 300)
     .option("--context-file <path>", "text file with Grok system context (required if GROK_API_KEY set)")
-    .addHelpText("after", "\nEnvironment:\n  GROK_API_KEY     xAI API key — enables Grok replies\n  SIMPLEX_BACKEND  sqlite | postgres — alternative to .npmrc for backend selection\n")
+    .addHelpText("after", "\nEnvironment:\n  GROK_API_KEY      xAI API key — enables Grok replies\n  SIMPLEX_LIBS_DIR  local libsimplex build for the --db backend\n")
 }
 
 interface RawOpts {
   teamGroup: string
   stateFile: string
+  db: api.DbConfig["type"]
   sqliteFilePrefix: string
   sqliteKey?: string
   pgConn?: string
@@ -93,19 +81,19 @@ export function parseConfig(args: string[]): Config {
     throw err
   }
   const opts = cmd.opts<RawOpts>()
+  const given = (option: keyof RawOpts) => cmd.getOptionValueSource(option) === "cli"
 
   const grokApiKey = process.env.GROK_API_KEY || null
 
-  const backend = detectBackend()
   let db: api.DbConfig
-  if (backend === "sqlite") {
+  if (opts.db === "sqlite") {
+    if (given("pgConn") || given("pgSchema")) throw new Error("--pg-conn and --pg-schema require --db postgres")
     db = opts.sqliteKey
       ? {type: "sqlite", filePrefix: opts.sqliteFilePrefix, encryptionKey: opts.sqliteKey}
       : {type: "sqlite", filePrefix: opts.sqliteFilePrefix}
   } else {
-    if (!opts.pgConn) {
-      throw new Error("--pg-conn is required when backend is postgres (PostgreSQL connection string)")
-    }
+    if (given("sqliteFilePrefix") || given("sqliteKey")) throw new Error("--sqlite-file-prefix and --sqlite-key require --db sqlite")
+    if (!opts.pgConn) throw new Error("--pg-conn is required with --db postgres")
     db = opts.pgSchema
       ? {type: "postgres", connectionString: opts.pgConn, schemaPrefix: opts.pgSchema}
       : {type: "postgres", connectionString: opts.pgConn}
diff --git a/apps/simplex-support-bot/vitest.config.ts b/apps/simplex-support-bot/vitest.config.ts
index c143572a87..3a70f6c5e7 100644
--- a/apps/simplex-support-bot/vitest.config.ts
+++ b/apps/simplex-support-bot/vitest.config.ts
@@ -5,13 +5,6 @@ export default defineConfig({
   test: {
     globals: true,
     testTimeout: 10000,
-    // Clear backend signals — .npmrc next to package.json otherwise injects
-    // npm_config_simplex_backend into every test's env, breaking sqlite-default
-    // assumptions in parseConfig tests.
-    env: {
-      SIMPLEX_BACKEND: "",
-      npm_config_simplex_backend: "",
-    },
   },
   resolve: {
     alias: {