The short version: CopyRates now errors out instead of returning partial data when you request beyond available history — some EAs may stop opening trades. The drawdown calculation in trading reports got a bug fix, so your numbers will look different. WebRequest and ONNX support both improved. If you're running EAs, back up your .set files before updating, and check your logs right after.
MetaQuotes pushed MT5 Build 5800 on April 16, 2026. The changelog is long. Most of it is UI tweaks and developer tooling that won't matter to you. But a few changes directly affect whether your EA runs correctly and whether your trading report numbers still make sense.
This isn't a translated changelog. We're only covering the parts that matter to EA traders. Our team already installed 5800 in a test environment, and some of what follows comes from issues we hit ourselves.
What Build 5800 Changed
Let's run through the main changes quickly.
The trading dialog got a redesign. The new version integrates the DOM (Depth of Market) right into the order window, so you can see the order book while placing trades. Nice for manual traders. But EAs place orders programmatically — they don't touch this dialog. Move on.
The help system switched engines. Pressing F1 used to open a local CHM file. Now it renders a web page. Loads faster, but if you use dark mode, brace yourself — the help pages are blindingly white. People are already complaining on the MQL5 forum. MetaQuotes hasn't addressed it yet.
MQL5 got L1 Trend Filter, a trend extraction method based on L1-norm regularization with OpenBLAS matrix operations under the hood. Good news for quant developers. Regular EA users won't need it for now. If you're curious, here's the MQL5 documentation.
ONNX CUDA support expanded — coverage now stretches from Turing all the way to Blackwell. More on that below.
MetaEditor added a CSV table view. Previously you'd stare at raw comma-separated text. Now there's an actual table interface. Small quality-of-life win.
Plus a bunch of bug fixes. Let's dig into the ones that actually affect your trading.
EA Impact Quick Reference
| Change | Impact | What You Need to Do |
|---|---|---|
| CopyRates return value change | High | Check EA logs after updating |
| Drawdown calculation fix | Medium | Be aware — trading report numbers will change |
| OpenBLAS/ONNX library fix | Low | ML-based EAs: verify DLLs |
| WebRequest Keep-Alive | Low (good news) | Nothing — it just works better |
| CopyTicksRange fix | Medium | Multi-symbol EAs: re-run backtests |
| ONNX CUDA expansion | Low | ML users benefit |
The Changes That Actually Matter for EA Traders
This is the section you came here for.
CopyRates Behavior Changed — This Is the One That'll Bite You
This is the biggest change for EA users in Build 5800.
CopyRates is the MQL5 function that fetches candlestick history. Almost every EA uses it. Previously, if you requested more data than the broker's server actually had, MT5 would helpfully return whatever it could find. Ask for 10,000 bars, server only has 8,000? Here's 8,000. No complaints.
After Build 5800, that same request returns -1. Error.
We found this the hard way. A couple of our EAs pull longer history windows during initialization for moving average calculations. After updating, two of them silently stopped opening trades on certain brokers. No error popups, no crashes — they just sat there doing nothing. We had to dig into the logs to find CopyRates failing because the requested range exceeded available history on that specific server.
You don't need to modify any code yourself. But after updating, you absolutely need to check your EA logs. Open the Toolbox panel in MT5, go to the Journal tab, and look for anything new. If you see CopyRates returned -1 or similar messages, get in touch with your EA developer.
For more on reading EA error logs, check our MT5 error code guide.
Drawdown Calculation Got Fixed — Your Trading Report Numbers Will Change
MT5 had a bug in how it generated trading reports for live and demo accounts. When you withdrew money from your account, the resulting balance decrease got counted as drawdown. You pull $5,000 out of a profitable account, and MT5 recorded it as if you'd lost $5,000. That's obviously wrong.
Build 5800 fixes this.
To be clear: this affects trading reports — the account history reports you export from live or demo accounts. If you've ever shared a trading report with an investor or posted one on a forum, the drawdown number may have been inflated by withdrawals. After updating, the same account history will show a smaller max drawdown figure. Your account didn't suddenly get better. The math just got corrected.
For a detailed breakdown of how to read trading report metrics properly, our EA backtesting guide covers the key indicators. And if you've noticed gaps between your backtest results and live performance, take a look at why backtests and live trading diverge — that's a separate issue, but worth understanding alongside this fix.
OpenBLAS and ONNX Library Downloads Fixed
Build 5800 patched the update logic for OpenBLAS and ONNX libraries. Some users had been hitting issues where these files went missing or ended up at the wrong version after a platform update, which would break any EA relying on matrix operations or ONNX models.
Most EAs don't use these. But if you're running something that involves machine learning or advanced statistical modeling, and it starts throwing errors after updating, check whether openblas.dll exists in your MT5 installation directory and that it's the right version.
WebRequest Is More Stable Now
EAs that use the WebRequest function for HTTP calls will benefit here. The typical use case: Telegram push notifications, remote monitoring dashboards, pulling data from external APIs.
We've helped users troubleshoot "Telegram messages stopped sending" more times than we can count. The root cause was almost always the same — the HTTP connection dropped, and the EA sat waiting for a timeout before it could reconnect. The Keep-Alive mechanism is improved now, which should reduce these disconnection issues significantly.
No code changes needed. It just works better after the update.
Multi-Symbol Data in Strategy Tester Got Fixed
If you run multi-symbol EAs — ones that trade several currency pairs or instruments simultaneously — pay attention to this one.
The Strategy Tester had a bug where CopyTicksRange would return error 4401 when fetching tick data for symbols other than the primary test symbol. This meant multi-symbol backtest results were unreliable.
Plain English: multi-symbol EA backtests are more accurate now. If you've been scratching your head over why a multi-pair EA's backtest looked nothing like its live performance, try re-running the backtest on Build 5800. We re-tested several of our multi-symbol portfolio strategies after updating, and the results lined up noticeably better with live performance.
ONNX CUDA Support Covers More GPUs
This one's for people running ONNX models on GPU. The supported NVIDIA architectures now span from Turing (RTX 20 series) through Ampere (RTX 30), Ada Lovelace (RTX 40), Hopper (data center cards), all the way to Blackwell (RTX 50 series).
If you're using ONNX machine learning EAs, you can now leverage newer GPUs for inference. Not running ML models? Skip this.
What to Do Before and After Updating
Before you update, back up your EA parameter files (.set files). You'll find them in MQL5/Profiles/Tester/. Back up your chart templates and layouts too — there were reports before Build 5800 of layouts getting lost after unexpected shutdowns.
After updating, run through this checklist:
- Open your EA logs and look for new errors, especially anything related to
CopyRates - If your trading report shows different drawdown numbers than before, that's not a bug — withdrawals are no longer counted as drawdown
- EAs using Telegram notifications don't need any changes
- ML-based EAs throwing errors? Check that
openblas.dllexists in your MT5 directory and is the correct version - Running EAs on a VPS? Update and test locally first. Only update the VPS once you've confirmed everything works
- While you're re-running backtests, it's a good time to check whether your EA has overfitting issues
- New to EAs entirely? Start with our step-by-step MT5 EA installation guide
What the Community Is Saying
As of now, the MQL5 forum hasn't seen any major wave of EA compatibility complaints.
Most of the grumbling is about the UI. The dark mode help pages are hard to read (white background, no dark mode support). The chart zoom ceiling is lower than before, which has annoyed some traders. MetaEditor had a focus bug in its Find dialog, though that was actually fixed in the earlier Build 5792.
Overall, this is a pretty smooth update. According to the MetaQuotes official changelog, Build 5800 focused on UI modernization and expanding the MQL5 math library. No fundamental changes to how EAs execute. But that CopyRates behavior change is a quiet one — MT5 won't pop up a warning to tell you about it. You'll only notice when your EA stops trading.
You can follow other users' feedback on the MQL5 official forum, read the Build 5800 full changelog for every detail, or check FX News Group's coverage for a concise English summary.
If you're looking for EAs that are tested and maintained through platform updates like this, take a look at our products page. FXTool members get compatibility updates first whenever a new build drops.
About the author: The FXTool team builds and tests MetaTrader trading tools daily. We run every EA we sell on live accounts and publish the results. This guide reflects what we've learned from building 50+ EAs and working with thousands of retail traders.
Risk disclosure: Forex trading involves significant risk and may result in the loss of your entire investment. Past EA performance does not guarantee future results. Only trade with money you can afford to lose.