669bede5c5
# Objective Closes #4868. Reintroduce automatic language detection for user-created untitled buffers without allowing it to override language choices made by users or owning surfaces. More details: + https://github.com/zed-industries/zed/pull/61201 + https://github.com/zed-industries/zed/pull/61351 ## Solution VS Code distinguishes between inferred and explicitly selected languages, and only continues automatic detection in the former state. This change introduces a buffer-local opt-in flag with the same purpose. It defaults to disabled and is enabled only for user-created untitled buffers and restored untitled buffers that did not persist a language. Choosing a language through the language picker disables detection, while automatically detected languages remain eligible for later redetection. Buffers whose language is assigned by their owning surface, such as Channel Notes, never opt in. Rather than adding persisted state or changing the database schema, restoration reuses the existing optional serialized language. An opted-in buffer that remains Plain Text is serialized without a language and resumes detection after restoration. Once automatic detection has selected a language, that language is serialized normally and restoration leaves detection disabled, effectively treating it as an explicit selection. This also matches VS Code's effective default after restoration. Candidate selection adopts VS Code's confidence-group filtering. Results below the minimum confidence are discarded, and candidate groups are accepted only after a clear confidence gap. The detector then selects the first available Zed language without eagerly loading every candidate. I then added a separate switching rule: Zed keeps the current language unless another candidate has a clear confidence advantage, reducing language changes as model scores fluctuate during editing. Model inference runs off-thread on a bounded sample, and stale results are discarded. I also evaluated penalizing YAML and using stricter global switching thresholds, but neither reliably resolves the ambiguity between Markdown and YAML. In the reproduction from #61351, Betlang assigns YAML more than 80% confidence during editing and peaks around 90%. This is reasonable from the content alone: `#` denotes a YAML comment, while `-` denotes a sequence item. Adding ordinary prose or a fenced code block shifts the model strongly toward Markdown. A fixed penalty would overfit this example and risk suppressing legitimate YAML detection. Since known-language buffers do not opt in and manual language selection takes precedence, I consider this level of ambiguity acceptable and prefer not to introduce language-specific score tuning. Model inference itself is fast. As noted in #61201: > In release builds on Linux with an Intel Core i5-13600KF, the `betlang::detect` call alone typically completes within 3 ms when processing the maximum sampled input. The main concern is the work surrounding inference. Without debouncing, rapid typing creates a snapshot and launches a background detection task on every keystroke, while the detected language may change before the user has finished typing. This change therefore adds a 200 ms debounce delay, allowing detection to run and update the language only after the user pauses. ## Testing Automated coverage verifies that short inputs remain Plain Text, sufficient Rust content is detected as Rust, replacing it with Go content triggers redetection, and manually selecting Plain Text prevents subsequent automatic changes. Restoration coverage verifies that a stored language keeps detection disabled, while an empty language-less untitled buffer resumes detection. Beyond the automated tests, I manually tested automatic language detection while editing untitled buffers. ## Self-Review Checklist: - [x] I've reviewed my own diff for quality, security, and reliability - [x] Unsafe blocks (if any) have justifying comments - [x] The content adheres to Zed's UI standards ([UX/UI](https://github.com/zed-industries/zed/blob/main/CONTRIBUTING.md#uiux-checklist) and [icon](https://github.com/zed-industries/zed/blob/main/crates/icons/README.md) guidelines) - [x] Tests cover the new/changed behavior - [x] Performance impact has been considered and is acceptable ## Showcase https://github.com/user-attachments/assets/103fc731-e12e-48d6-ae89-03978f1c9d74 --- Release Notes: - Added automatic language detection for untitled buffers. --------- Co-authored-by: Max Stevens <maxstevens2708@gmail.com> Co-authored-by: Christopher Biscardi <chris@christopherbiscardi.com>
Zed
Welcome to Zed, a high-performance, multiplayer code editor from the creators of Atom and Tree-sitter.
Installation
On macOS, Linux, and Windows you can download Zed directly or install Zed via your local package manager (macOS/Linux/Windows).
Other platforms are not yet available:
- Web (tracking discussion)
Developing Zed
Contributing
See CONTRIBUTING.md for ways you can contribute to Zed.
Also... we're hiring! Check out our jobs page for open roles.
Licensing
Zed source code is licensed primarily under GPL-3.0-or-later, with Apache-2.0 components where marked.
License information for third party dependencies must be correctly provided for CI to pass.
We use cargo-about to automatically comply with open source licenses. If CI is failing, check the following:
- Is it showing a
no license specifiederror for a crate you've created? If so, addpublish = falseunder[package]in your crate's Cargo.toml. - Is the error
failed to satisfy license requirementsfor a dependency? If so, first determine what license the project has and whether this system is sufficient to comply with this license's requirements. If you're unsure, ask a lawyer. Once you've verified that this system is acceptable add the license's SPDX identifier to theacceptedarray inscript/licenses/zed-licenses.toml. - Is
cargo-aboutunable to find the license for a dependency? If so, add a clarification field at the end ofscript/licenses/zed-licenses.toml, as specified in the cargo-about book.
Sponsorship
Zed is developed by Zed Industries, Inc., a for-profit company.
If you’d like to financially support the project, you can do so via GitHub Sponsors. Sponsorships go directly to Zed Industries and are used as general company revenue. There are no perks or entitlements associated with sponsorship.