Configuration

Connection settings

The most commonly used MT5WebClient constructor settings are:

Setting	Default	Purpose
`uri`	MT5 Web Terminal URL	WebSocket endpoint. Use the endpoint authorized for your environment.
`timeout`	`30.0`	Command and initial connection timeout in seconds. A timeout after a possible send isolates the connection; it is not a server ACK/NACK.
`heartbeat_interval`	`30.0`	Seconds between heartbeat pings after login.
`auto_reconnect`	`False`	Reconnect and log in again after an unexpected disconnect.
`max_reconnect_attempts`	`5`	Maximum attempts per reconnect cycle.
`reconnect_delay` / `max_reconnect_delay`	`3.0` / `60.0`	Base and cap for exponential backoff with jitter.
`rate_limit` / `rate_burst`	`0` / `20`	Optional token-bucket command throttling; zero disables the limit.
`metrics`	`None`	Optional `MetricsCollector` implementation.

See API Reference for the complete constructor and cache-related settings.

Protocol compatibility settings

Historical bars: `rate_bar_format`

auto decodes only when response length uniquely identifies the standard 48-byte or extended 56-byte record. Ambiguous or mismatched lengths raise ProtocolError. If the server layout is known, select standard or extended explicitly, or pass bar_format to supported rate methods. Length validation cannot prove semantic correctness for every payload.

Tick prices: `tick_price_mode` and `tick_price_modes`

auto preserves the legacy symbol/magnitude heuristic and is the default. It is a compatibility behavior, not a universal wire-format guarantee.
scaled divides nonzero prices by 10 ** symbol.digits.
normalized leaves wire prices unchanged.
tick_price_modes={"EURUSD": "scaled"} overrides the global mode for a symbol; keys are case-insensitive and take precedence.

Apply the same setting to raw callbacks, typed events, and caches. Validate against a small authorized sample from the target server/build before relying on the values. A live probe is available as scripts/demo_tick_probe.py; its output is evidence to inspect, not an automatic acceptance decision.

Trade requests: `trade_protocol`

legacy is the default wire profile. build_6090 opts into the reserved bytes and market-deal behavior reported for one environment. The client does not infer this profile from the handshake build number. Broker, execution-mode, and build compatibility must be established independently.

Environment variables

Variable	Use
`PYMT5_SERVER`	WebSocket URI used by examples and integration tests.
`PYMT5_LOGIN` / `PYMT5_PASSWORD`	Credentials for explicitly enabled demo integration tests. Never commit their values.
`PYMT5_TEST_SYMBOL`	Liquid, active symbol for tick integration/probe runs.
`PYMT5_INTEGRATION=1`	Explicit opt-in to live integration tests; absent from the offline gate.
`PYMT5_LOG_LEVEL`	Library log threshold. Avoid verbose credential/session logging in captured reports.

The core client does not automatically load .env. Use your application’s secret manager or an explicit dotenv loader. Keep local environment files ignored by Git.

Recommended starting point

import os
from pymt5 import MT5WebClient

client = MT5WebClient(
    uri=os.environ["PYMT5_SERVER"],
    timeout=30.0,
    auto_reconnect=True,
    rate_bar_format="auto",
    tick_price_mode="auto",
    trade_protocol="legacy",
)

Start with read-only queries. Change compatibility modes only from evidence, and review Reliability and Security and Operational Safety before trading.