Configuration

Every setting the daemon reads: the four layers and which wins, the TOML blocks with their defaults, and the environment variables that override them.

Four layers, later ones win:

built-in defaults
a TOML file, passed with --config
environment variables
command-line flags

Every field has a default, so a daemon with no configuration at all starts and serves.

The top level

Key	Default	What it does
`bind_addr`	`127.0.0.1:8787`	The native API: REST, MCP over HTTP, the CDP WebSocket. Non-loopback requires `[tls]`.
`adspower_bind`	off	The AdsPower adapter. Loopback only, and off until you set it.
`data_dir`	`%ProgramData%\Scalebrowser`	Database, engines, profile directories, the at-rest key.
`engines_dir`	follows `data_dir`	Set it only to split the tree deliberately. Once set, it stops following.
`profiles_dir`	follows `data_dir`	Same.
`bearer_token`	generated on first start	The token clients send.
`engine_feed_url`	none	A signed engine feed to check at startup. Without one the daemon never reaches out and `engine install` is the only path in.
`webui_dir`	the embedded bundle	Serve the management interface from a directory instead.
`ja4t_reflector_url`	none	An endpoint that reports the TCP fingerprint it saw. Fetched through the proxy during a check, which is the only way to learn the exit device's fingerprint.
`error_reporting`	`false`	Crash reports. Off by default: on an anti-detect product, telemetry nobody asked for is a surprise that costs the relationship.
`error_dsn`	none	Where they go. Empty disables reporting whatever the flag says.
`log_json`	`false`	Machine-readable log lines. On where something parses them, off where a person reads them.

`[secret]`

Where the at-rest master key comes from. One of the two:

Key	What it does
`key_env`	Name of the environment variable holding it.
`key_file`	Path to a file holding it.

`[capacity]`

Hard limits, so a launch is refused rather than the host running out of memory.

Key	Default	What it does
`max_concurrent`	`64`	Browsers on this machine at once.
`ram_budget_mb`	`24576`	Memory the pool may use.
`vram_budget_mb`	none	Video memory, when you want a ceiling on it.

Three limits apply to a launch and the strictest wins: these two, and the host's measured free memory. Exceeding any of them is error 4003.

`[tls]`

Key	What it does
`cert_path`	PEM certificate chain.
`key_path`	PEM private key.

Required for a non-loopback bind, optional on loopback, and honoured there too if set.

`[mcp]`

Everything here is decided server-side. No tool call can widen the catalog or leave read-only mode.

Key	Default	What it does
`profiles`	`["core"]`	Which tool profiles are served.
`read_only`	`false`	Mutating tools are neither listed nor executed.
`lease_ttl_secs`	`900`	How long a reservation lives by default.
`lease_ttl_max_secs`	`14400`	Ceiling on what a caller may ask for. Four hours.
`url_allowlist`	`[]`	Exceptions to the `open_page` address rule. Exact hosts or `host:port`.
`artifact_quota`	`256`	How many artifacts are kept per profile.
`artifact_max_bytes`	24 MiB	Ceiling on one artifact.
`artifact_ttl_secs`	`14400`	Retention. Matches the lease ceiling, so an artifact from the start of a long run is still there at the end.
`allowed_hosts`	`[]`	Extra `Host` values the MCP transport accepts, on top of loopback and the configured bind.
`snapshot_full_every`	`5`	Force a full page map every N steps. `0` disables it.
`transcribe_command`	`[]`	Your program for audio challenges. One argument in, text out.
`inbox_command`	`[]`	Your program for non-IMAP inboxes, such as an SMS service.
`inbox_require_proxy`	`false`	Refuse an inbox read that would leave over this machine's own connection.

url_allowlist empty is the safe state. Empty means open_page permits public http and https only: no file:, no loopback, no private or link-local networks, no cloud metadata address. Every entry you add is a door into your own network that an agent can walk through.

`[observability]`

Key	Default	What it does
`sample_interval_ms`	`3000`	Cadence of the background sampler behind `GET /v1/metrics`.
`enable_prometheus`	`false`	The opt-in scrape endpoint.
`prometheus_bind`	`127.0.0.1:9464`	Its listener. Unauthenticated plaintext; keep it on loopback.

`[runs]`

Key	Default	What it does
`shots`	`true`	Keep a still per step in the activity trail.
`shots_max_gb`	`20`	Disk ceiling for them.
`shots_max_age_days`	`30`	Retention.
`page_watcher`	`true`	Follow what the bound tab is showing.

`[exit]`

The exit-address rule.

Key	Default	What it does
`enabled`	`true`	The whole rule.
`probe_url`	`https://probe.scalebrowser.net/v1/addr`	Where the address is measured.
`neighbour_hard`	`false`	Treat two addresses in one IPv4 `/24` as a collision, not advice.
`heartbeat_secs`	`30`	Keep-alive beat, where a provider documents an idle cut-off.
`check_secs`	`120`	Address check.
`max_draws`	`5`	How many session tags a start may try before refusing with `4013`.

`[sync]` and `[remote]`

Profile sync and remote access have their own blocks. Both have a switch in the management app, and for remote access that switch is the one to use: the daemon reads it on every beat, so it takes effect without a restart.

Environment variables

Every one of these overrides the TOML.

Variable	Sets
`SCALEBROWSER_BEARER_TOKEN`	The API token clients send.
`SCALEBROWSER_MASTER_KEY`	The at-rest key.
`SCALEBROWSER_API_TOKEN`	The pairing token for this machine.
`SCALEBROWSER_DATA_DIR`	`data_dir`.
`SCALEBROWSER_ENGINES_DIR`	`engines_dir`.
`SCALEBROWSER_PROFILES_DIR`	`profiles_dir`.
`SCALEBROWSER_BIND_ADDR`	`bind_addr`.
`SCALEBROWSER_ADSPOWER_BIND`	`adspower_bind`. Takes the word `off`.
`SCALEBROWSER_WEBUI_DIR`	`webui_dir`.
`SCALEBROWSER_ENGINE_FEED_URL`	`engine_feed_url`.
`SCALEBROWSER_CONTROL_PLANE_URL`	Where the account lives.
`SCALEBROWSER_MCP_PROFILES`	`[mcp] profiles`, comma separated.
`SCALEBROWSER_MCP_READ_ONLY`	`[mcp] read_only`.
`SCALEBROWSER_ENABLE_PROMETHEUS`	`[observability] enable_prometheus`.
`SCALEBROWSER_PROMETHEUS_BIND`	`[observability] prometheus_bind`.
`SCALEBROWSER_SAMPLE_INTERVAL_MS`	`[observability] sample_interval_ms`.
`SCALEBROWSER_ERROR_DSN`	`error_dsn`.
`SCALEBROWSER_ERROR_REPORTING`	`error_reporting`.

Two more are about the host rather than the daemon: SB_HOST_GPU_CLASS and SB_HOST_GPU_VENDOR skip the boot GPU probe.

Never set SB_HOST_GPU_CLASS on a machine you are actually running profiles on, unless you also set the vendor. The skipped probe never learns which GPU family the host has, and the profile can then ship a GPU string from the wrong one, which is a contradiction a page finds in one comparison.

CLI reference: the flags and subcommands.
Troubleshooting: what these settings look like when one is wrong.
MCP server: what [mcp] does to an agent.