fidzu : Mozilla

Following the rollout of Firefox's Shake to Summarize feature to Android devices this May, we wanted to take a closer look at the modeling work behind the feature. In a previous blog post, we discussed our model selection process. Now that Shake to Summarize has been available on both iOS and Android for a few months, we wanted to take it a step further and outline our approach to prompt development.

This is the story of a Shake to Summarize use case that required a little extra prompt tuning: online recipes.

Framing the Problem

The first step in developing a useful prompt is clearly describing what you want the LLM to do. LLMs thrive on specificity, so the more sharply you can define your task, the better your results are likely to be.

This is especially important when using smaller LLMs (like we are here), since these little models are not as good at reading between the lines and intuiting unstated intentions as their more powerful cousins are.

For this application, we were looking to create summaries. On the face of it, this seems pretty straightforward. However, as we iterated on prompts, we quickly discovered that what constitutes a "good" summary depends largely on what one is summarizing.

For example, a useful summary of a novel should provide us with a quick overview of the plot without getting into too many specific details; we wouldn't expect the summary to contain anything from the text verbatim.

In contrast, a summary of a recipe website should include the recipe essentially as written. If the recipe says "cook lovingly" we might be OK with shortening it to "cook," but if it calls for 4 cups of vegetable broth, a Tbsp of oregano and a tsp of thyme, we want these details relayed to us exactly. Merely stating, "this recipe calls for some broth and some spices" would not be adequate.

Forming the Prompt

From here, it became clear that we wanted not just one "summarize" instruction, but a whole set of instructions - one for each category of webpage that we wished to summarize. We worked with the product team to compile a list of article types that we were targeting for this feature. For each article type, we then gave a brief description of what a good summary would look like:

Recipe - Ingredients as written, along with the key steps, time required, and any tips given by the author or commenters

News - Only the important details: what happened, when, and what would be the likely consequences to the reader

How-to - Start with the required materials, skills, tools, etc., along with the main steps and any specific warnings called out by the author

Review - Highlight the bottom line rating. If it is a product review, include the pros and cons, the price, and who the target audience is.

Research - Key finding and level of confidence the researchers have in their results as well as the projected real-world impact.

Opinion - The main argument, along with any key evidence cited in support

We then wrapped this list in some general instructions to ground the model in the task and came up with our initial prompt (formatted for readability) [source]:

You are a Content Summarizer. You create mobile-optimized summaries by first understanding what users actually need from each type of content.

Process:

Step 1: Identify and Adapt.

Step 2: Based on content type, prioritize:

Recipe - Servings, Total time, Ingredients list, Key steps, Tips.

News - What happened, when, where.

How-to - Total time, Materials, Key steps, Warnings.

Review - Bottom line rating, price.

Opinion - Main arguments, Key evidence.

Personal Blog - Author, main points.

Fiction - Author, summary of plot.

All other content types - Provide a brief summary of no more than 6 sentences.

Step 3: Format for mobile using concise language and paragraphs with 3 sentences maximum.

Bold critical details (numbers, warnings, key terms).

We Foxfooded the above prompt and found that it mostly worked pretty well. The summaries the model produced were concise, accurate, and informative.

The only exception was recipes.

We found that, when the prompt above was used for recipes, the model tended to summarize too much - often leaving out key ingredients, or in some cases, leaving out the recipe entirely.

For example, when asked to summarize a lentil soup recipe the model returned:

The webpage provides a detailed recipe for a vegan lentil soup, which the author claims is the best they've ever made. The soup is made with pantry staples like lentils, diced tomatoes, vegetable broth, and spices (cumin, curry powder, thyme), along with fresh vegetables (onion, carrots, garlic) and greens (kale or collard greens). A key step is blending a portion of the soup to create a creamy texture without dairy.

The summary is accurate, so far as it goes, but it isn't exactly useful. If our goal is to have the summary be a quick way to access the recipe itself, without having to read through the narrative preamble, this wouldn't cut it.

Focusing the Prompt

To address this problem, we needed to be more explicit with the instructions we gave the model when summarizing recipes: we needed to tell it which information we were interested in and which it could safely discard.

Although we could have added this extra guidance directly to the prompt above, doing so risked causing the model to over-index on the recipe formatting and ignore the other article types. Instead, we developed a separate prompt which contained only the recipe instructions and directed recipe summarization requests to use it, rather than the general one [source].

To perform this routing, we used the structured data embedded in each webpage. While this categorization could have been handled by another model pass, metadata from the webpage itself allowed us to quickly and deterministically identify the page categories without additional inference overhead. To capture cases where this data is either missing or inaccurate, we also maintain some lightweight recipe guidance in the general prompt.

After this change, the summary returned by the model for the above recipe became much more usable (shortened for brevity):

Servings: 6

Total Time: 50 minutes

Prep Time: 10 minutes

Cook Time: 40 minutes

Ingredients

• ¼ cup extra virgin olive oil
• 1 medium yellow or white onion, chopped
• 2 carrots, peeled and chopped
• …

Instructions

1. Warm the olive oil in a large Dutch oven or pot over medium heat.
2. Add the chopped onion and carrot, cooking until the onion softens and turns translucent, about 5 minutes.
3. …

Tips

• Use an immersion blender for easier blending without transferring soup.
• …

Nutrition

• Calories: 320
• …

With this change in place, we ran a quick test over a curated set of recipe sites and found that the new system was more than twice as likely to return a complete and accurate summary than our previous one. Success!

The system was now working as expected: summaries were useful and recipes were complete.

Reflections

From this experience we learned that the model produced the best results when it was told explicitly what we wanted it to do. When the instructions were vague or left too much up to the model, performance suffered.

To this end, we found that framing this problem as a routing problem - where the specific kinds of articles are routed to specific prompts - worked well. Since the task of summarization is not monolithic, our summarization pipeline should not be either.

Even though our current approach has only a single category-specific prompt, we hypothesize that the system would see further gains by using dedicated prompts for other page types as well.

More broadly, this experience reinforced an important lesson for us: improving AI systems is not solely about building larger or more capable models. Some of the biggest gains come from reducing ambiguity, narrowing the task, and designing systems that help the model succeed. Within the right harness, smaller, open source models can deliver great value.

While building more capable models continues to advance the field, our experience shows that thoughtful system design and solid engineering still matter.

The post Under the Hood: Prompt tuning Shake to Summarize for recipes appeared first on The Mozilla Blog.

01 Oct 2026 4:00pm GMT

The Rust team is happy to announce a new version of Rust, 1.99.0. Rust is a programming language empowering everyone to build reliable and efficient software.

If you have a previous version of Rust installed via rustup, you can get 1.99.0 with:

$ rustup update stable

If you don't have it already, you can get rustup from the appropriate page on our website, and check out the detailed release notes for 1.99.0.

If you'd like to help us out by testing future releases, you might consider updating locally to use the beta channel (rustup default beta) or the nightly channel (rustup default nightly). Please report any bugs you might come across!

What's in 1.99.0 stable

extern "C" variadics

Rust 1.99.0 stabilizes defining C-ABI variadic functions with "C" and "C-unwind" ABIs. Variadic functions defined this way use a variable argument list (...) and accept an arbitrary number of arguments. Rust could already call externally-defined variadic functions (e.g., libc::printf). With Rust 1.99, these functions can now be written in Rust itself:

/// SAFETY: must be called with (at least) 2 i32 arguments.
unsafe extern "C" fn sum(mut args: ...) -> i32 {
    // SAFETY: guaranteed by the caller.
    let a = unsafe { args.next_arg::<i32>() };
    let b = unsafe { args.next_arg::<i32>() };
    a + b
}

fn foo() -> i32 {
    unsafe { sum(0i32, 2i32) }
}

The type of ... is VaList, which is ABI-compatible with the C va_list type across targets. What types can be read from a VaList is guarded by the VaArgSafe trait.

For more details on c-variadic functions, see the Reference. This release also stabilizes support for defining naked variadic functions with non-"C" ABIs, which must be written via inline assembly.

Layout information from raw pointers

This release settles the safety requirements for retrieving the size and alignment on raw pointers to both Sized (trivially safe, already possible on stable) and non-Sized types.

This is done by stabilizing three functions:

• Layout::for_value_raw
• mem::size_of_val_raw
• mem::align_of_val_raw

Recommend against round-trip unleaking after Box::leak

While there are no changes to the language semantics in Rust 1.99, we have updated the documentation on Box::leak to recommend against patterns that later deallocate that memory. This was done because such code was found to have problematic interactions with current and future potential compiler optimizations, and is especially problematic with the upcoming stabilization of custom allocators. Instead, Box::into_non_null or Box::into_raw should be preferred.

This guidance also applies to other leak functions in the standard library.

Stabilized APIs

• IntoIterator for Box<[T; N]>
• IntoIterator for &Box<[T; N]>
• IntoIterator for &mut Box<[T; N]>
• VecDeque::retain_back
• core::ffi::VaList
• Box::into_non_null
• Box::from_non_null
• Vec::into_parts
• Vec::from_parts
• core::mem::size_of_val_raw
• core::mem::align_of_val_raw
• core::alloc::Layout::for_value_raw
• String::from_utf8_lossy_owned
• string::FromUtf8Error::into_utf8_lossy
• FusedIterator for StepBy<I>
• std::fs::set_times
• std::fs::set_times_nofollow

Other changes

Check out everything that changed in Rust, Cargo, and Clippy.

Contributors to 1.99.0

Many people came together to create Rust 1.99.0. We couldn't have done it without all of you. Thanks!

01 Oct 2026 12:00am GMT

Hi Mozillian,

In this edition, we're exploring the new Firefox design, Mozilla's recent partnership with Mistral to expand choice in AI-powered browsing, and several ways to get involved with MozFest. You can join a livestream about the value of bringing open-source communities together in person, volunteer at MozFest in Barcelona, or take part in the latest privacy discussion from the Firefox community on Reddit.

Read on for the latest updates and opportunities to participate!

More modern. More flexible. Still Firefox.

Firefox 157 introduces a new Firefox design with updated colors, icons and themes that make the browser feel more modern while preserving the familiar Firefox experience. The release also brings back Compact Mode and adds easier theme selection, new wallpapers and more ways to customize the New Tab page. Underneath the new look, Firefox remains independent and open source, with built-in privacy protections and controls that let you decide how your browser works, including how AI features appear.

Learn more

Mozilla and Mistral partner to expand AI choice

Mozilla and Mistral have announced a partnership aimed at increasing competition and preserving user choice in AI-powered browsing. As part of the collaboration, the open-source Mistral Small 4 model is coming to Firefox Smart Window Beta as a new option for users in the US and Canada. Smart Window Beta is also expanding to France with official French-language support, with additional European markets planned. Users can continue choosing from multiple AI models, reinforcing Firefox's commitment to avoiding lock-in and keeping the web open to different technologies and providers.

Learn more

Does open source need IRL? The case for MozFest

Is showing up in person important for open source? Join the Owners Not Renters livestream on Tuesday, September 29, to hear the story behind MozFest and explore why gathering in person still matters for open-source communities ahead of MozFest, taking place October 28-30 in Barcelona. Kali Villarosa (MoFo), Seher Shafiq (MoFo) and Brian Behlendorf (co-founded Apache) will join host Marcus Rein for an open conversation, followed by a live Q&A. Bring your questions and your hot takes!

Watch and participate

MozFest call for Volunteers

From 28-30 October 2026, the Mozilla Foundation will host the Mozilla Festival in Barcelona, bringing together people from diverse fields to explore how we can work collectively to "re-wild" the web. To help bring the Festival to life, we're building a team of volunteers. By joining, you'll help deliver a major event in support of Mozilla's mission while also having opportunities to participate in sessions throughout the three-day Festival.

Sign up to volunteer

From the Reddit Community

Privacy conversations are going mainstream, and Firefox has been at this for 20+ years. In light of a recent video making the rounds about the importance of privacy, the Firefox Team shared a rundown of built-in privacy features (ad blocking, tracking protection, encrypted sync, a free VPN, and more). Jump in at r/firefox and share your own privacy tips and configs!

Join the discussion

---

P.S.

Enjoyed these updates? Subscribe to the Mozilla Community Newsletter and get the latest updates delivered straight to your inbox.

30 Sep 2026 5:01pm GMT

Hello and welcome to another issue of This Week in Rust! Rust is a programming language empowering everyone to build reliable and efficient software. This is a weekly summary of its progress and community. Want something mentioned? Tag us at @thisweekinrust.bsky.social on Bluesky or @ThisWeekinRust on mastodon.social, or send us a pull request. Want to get involved? We love contributions.

This Week in Rust is openly developed on GitHub and archives can be viewed at this-week-in-rust.org. If you find any errors in this week's issue, please submit a PR.

Want TWIR in your inbox? Subscribe here.

Updates from Rust Community

Newsletters

• Scientific Computing in Rust #22 (September 2026)
• The Embedded Rustacean Issue #81

Observations/Thoughts

• Can safe Rust ever beat Google's C Brotli?
• Building a DMA based driver for the RP2350 I2C (safety not included)
• Advanced soft-bodies for games with the Rapier physics engine
• Supporting native Rust in Workers with the new Emscripten target for wasm-bindgen
• Rusty thoughts on "Parse, don't validate"
• The state of SIMD in Rust in 2026
• How do you stop being a Rust novice?
• We Have Named Arguments at Home: a reply to the blog post Arguing about arguments mentioned in the last issue
• Upstream Rust maintenance report (August-September 2026)
• Rust in the kernel? What about Rust without the kernel!
• Compiling the kernel with gccrs
• Listening to the radio with Rust
• Native support for Rust on the GPU

Rust Walkthroughs

• How to speed up the Rust compiler in September 2026
• Building Real-Time Notifications with SSE and Pub/Sub
• Green Threads from Scratch
• A Type Stronger than the Sum of its Components
• Deser: Rethinking Rust Serialization
• Dropping Swift from our Bevy iOS crates
• Pining for Arc Downcasting in Rust
• Topcoat is pushing the boundary of server applications with Rust
• Rust Reborrowing, Aliasing, and Mutable References
• A very condensed introduction of the basics of Rust
• [video] Making Our GPUI App Interactive with State and Events
• [ES] Domain-Flow-Effects (DFE): an architecture designed for Rust

Miscellaneous

• [DE]Rust & Linux Community Event - November 20-21, 2026 @ TUXEDO, Augsburg - Help us choose the workshop topic

Crate of the Week

This week's crate is ying-profiler, a native Rust sampling memory profiler.

Thanks to Evan Chan for the self-suggestion!

Please submit your suggestions and votes for next week!

Calls for Testing

An important step for RFC implementation is for people to experiment with the implementation and give feedback, especially before stabilization.

If you are a feature implementer and would like your RFC to appear in this list, add a call-for-testing label to your RFC along with a comment providing testing instructions and/or guidance on which aspect(s) of the feature need testing.

No calls for testing were issued this week by Rust, Cargo, Rustup or Rust language RFCs.

Let us know if you would like your feature to be tracked as a part of this list.

Call for Participation; projects and speakers

CFP - Projects

Always wanted to contribute to open-source projects but did not know where to start? Every week we highlight some tasks from the Rust community for you to pick and get started!

Some of these tasks may also have mentors available, visit the task page for more information.

• unsynced - strace frontend fails on pwritev2 with offset -1 (current file offset)
• unsynced - Model hard links (link/linkat) instead of warning
• unsynced - Add an ext4 data=writeback persistence profile
• MemoryWhale - Cover friendly errors for incomplete mw arguments
• MemoryWhale - Lock down mw --help output
• dataprof - Remote Parquet refusal messages should say to download the file when the server ignores Range
• dataprof - ScoreBounds::dimension_scores docs still list estimated key counts as unbounded
• dataprof - The progress finished event under-counts rows when a row cap stops the incremental engine

If you are a Rust project owner and are looking for contributors, please submit tasks here or through a PR to TWiR or by reaching out on Bluesky or Mastodon!

CFP - Events

Are you a new or experienced speaker looking for a place to share something cool? This section highlights events that are being planned and are accepting submissions to join their event as a speaker.

If you are an event organizer hoping to expand the reach of your event, please submit a link to the website through a PR to TWiR or by reaching out on Bluesky or Mastodon!

Updates from the Rust Project

546 pull requests were merged in the last week

Compiler

• computing crate_hash from metadata encoding instead of HIR (implements #94878)
• detect missing else in let statement
• give noalias back to refs in closures
• implement forced keywords (k#)
• use SmallVec in LocalizedConstraintGraph

Library

• add Div and Mul for Complex<{float}>
• alloc: stabilise Allocator
• additional NonZero conversions
• allow elided ('static) lifetimes in thread_local!
• implement PartialEq<VecDeque<U>> for Vec<T>, &[T], &mut [T], [T; N], &[T; N] and &mut [T; N]
• make dropping an empty BTreeMap free
• stabilize SyncView
• stabilize Box::take
• stabilize Result::into_{ok,err}
• stabilize funnel_shifts (including const)
• stabilize mem::conjure_zst
• stabilize vec_try_remove
• use wrapping arithmetic in from_str_radix

Cargo

• builtin-deps: add builtin dependencies manifest syntax
• config: add build.profile, install.profile
• metadata: mirror package features in features_v2
• builtin-deps: fix builtin dependencies manifest validation
• diag: Don't report unused normal deps when static libs are skipped
• package: preserve feature metadata in normalized manifests

Rustdoc

• correctly check that an item is not doc(hidden) with --generate-link-to-definition
• fix intra doc link resolution when a doc comment is composed of both inner and outer doc comment
• fix invalid jump to def link when #[rustc_allow_incoherent_impl] is involved
• fix quadratic naming of duplicate sidebar links

Clippy

• while_let_loop: detect the pattern when the loop has a label
• add new try_from_instead_of_from_str lint
• don't suggest Box::leak in nonnull_unchecked_on_box_ptr
• fix collapsible_match consuming/mutation checking
• fix match_str_case matching str inside or patterns
• improve doc attr span tracking for proc-macro

Rust-Analyzer

• don't fail extension activation when the server fails to start
• add type_match relevance for type-alias
• coercion safe fn to unsafe fn
• complete 'false' in cfg attribute
• complete attr value inside string without quotes
• const eval cast of single-variant enum
• deduplicate 'derive' and 'test' attribute macro
• do not type match unknown type
• don't clear semantic tokens cache on refresh
• hover show impl header when impl with trait
• panic in async closures with higher-ranked trait bounds
• return UB instead of panicking when reading the discriminant of an uninhabited enum

Rust Compiler Performance Triage

This week was fairly positive. We had no pure regressions, and most of the results came from a few architectural improvements with mixed or mostly positive impact. Some improvements also come from addressing previously triaged regression caused by missing no_alias annotation for references in closures.

The biggest improvement this week is in rustdoc, from tackling quadratic behaviour when generating sidebar links. This was reported by a user, but the effect didn't show up in our benchmarks, so we added a special stress test for it.

Triage done by @panstromek. Revision range: 3670d253..c1070d69

Summary:

(instructions:u)	mean	range	count
Regressions ❌ (primary)	0.6%	[0.2%, 0.8%]	8
Regressions ❌ (secondary)	1.4%	[0.1%, 5.8%]	30
Improvements ✅ (primary)	-0.6%	[-1.7%, -0.2%]	192
Improvements ✅ (secondary)	-1.5%	[-82.5%, -0.1%]	101
All ❌✅ (primary)	-0.6%	[-1.7%, 0.8%]	200

0 Regressions, 2 Improvements, 6 Mixed; 3 of them in rollups 26 artifact comparisons made in total

Full report here

Approved RFCs

Changes to Rust follow the Rust RFC (request for comments) process. These are the RFCs that were approved for implementation this week:

• No RFCs were approved this week.

Final Comment Period

Every week, the team announces the 'final comment period' for RFCs and key PRs which are reaching a decision. Express your opinions now.

Tracking Issues & PRs

Rust

• Stop using dlltool for generating import libraries on MinGW
• Stabilize ptr::try_cast_aligned
• [disposition: close] 1.99 beta crater regression: overflow evaluating the requirement
• implement FCW for rustc_allowed_through_unstable_modules items
• fix VisibleForLeakCheck in RegionOutlives fast path
• Stabilize debug_closure_helpers
• Support type-relative assoc item paths in generic param defaults & const param types
• FCW for #[panic_handler] on unsafe fn.
• Stabilize optimize attribute
• Allow unary operand types to be inferred later
• Feat - #[inline(always)] + #[target_feature(enable = "....")] #2
• Tracking Issue for CStr::display
• Syntactically reject leading parenthesized precise capturing lists in bare trait object types ((use<…>)+)

Rust RFCs

• f16b type

Cargo

• feat(trim-paths): stabilize profile.trim-paths

Compiler Team (MCPs only)

• Create new Tier 3 Target for QTEE: aarch64-unknown-qtee

No Items entered Final Comment Period this week for Language Team, Language Reference, Leadership Council or Unsafe Code Guidelines. Let us know if you would like your PRs, Tracking Issues or RFCs to be tracked as a part of this list.

New and Updated RFCs

• Make trait methods callable in const contexts, take III

Upcoming Events

Rusty Events between 2026-09-30 - 2026-10-28 🦀

Virtual

• 2026-09-30 | Virtual (Cardiff, UK) | Rust and C++ Cardiff
  • Operating Systems Book Club: Segmentation and Introduction to Paging
• 2026-10-01 | Virtual | Rust Foundation & JetBrains
  • Livestream: Smarter Coding Agents for Rust with Symposium
• 2026-10-02 | Virtual | Rust Girona
  • Sessió setmanal de codificació / Weekly coding session
• 2026-10-03 | Virtual (Amsterdam, NL) | Bevy Game Development
  • Bevy Meetup #14
• 2026-10-04 | Virtual (Dallas, TX, US) | Dallas Rust User Meetup
  • Rust Deep Learning: First Sunday
• 2026-10-06 | Virtual (London, UK) | Women in Rust
  • 👋 Community Catch Up
• 2026-10-07 | Virtual (Indianapolis, IN, US) | Indy Rust
  • Indy.rs - with Social Distancing
• 2026-10-08 | Virtual (Berlin, DE) | Rust Berlin
  • Rust Hack and Learn
• 2026-10-08 | Virtual (Nürnberg, DE) | Rust Nuremberg
  • Rust Nürnberg online
• 2026-10-10 | Virtual (Gdansk, PL) | Stacja IT Trójmiasto
  • [BEZPŁATNIE] Programowanie w języku Rust
• 2026-10-10 | Hybrid (Kuala Lumpur, Malaysia) | Rust Malaysia Meetup
  • Rust Meetup October 2026
• 2026-10-13 | Virtual (Dallas, TX, US) | Dallas Rust User Meetup
  • Second Tuesday
• 2026-10-14 - 2026-10-17 | Hybrid (Barcelona, ES) | EuroRust
  • EuroRust 2026
• 2026-10-18 | Virtual (Dallas, TX, US) | Dallas Rust User Meetup
  • Rust Deep Learning: Third Sunday
• 2026-10-20 | Virtual (Washington, DC, US) | Rust DC
  • Mid-month Rustful
• 2026-10-21 | Hybrid (Vancouver, CA) | Vancouver Rust
  • Disposable Agent Sandboxes in Rust
• 2026-10-22 | Virtual (Berlin, DE) | Rust Berlin
  • Rust Hack and Learn
• 2026-10-27 | Virtual (Dallas, TX, US) | Dallas Rust User Meetup
  • Fourth Tuesday Rust Bookclub
• 2026-10-27 | Virtual (London, UK) | Women in Rust
  • Lunch & Learn: Reasoning with Async Rust

Asia

• 2026-10-09 | Hybrid (Kuala Lumpur, MY) | Rust Malaysia Meetup
  • Rust Meetup August 2026

Europe

• 2026-09-30 | Basel, CH | Rust Basel
  • Rust Meetup #16 @ ERNI
• 2026-09-30 | Berlin, DE | Rust Berlin
  • Rust Berlin Talks: The next generation
• 2026-10-01 | Berlin, DE | Rust Berlin
  • Rust Berlin on location 🏳️‍🌈 - Edition 018
• 2026-10-01 | Oxford, GB | Oxford ACCU/Rust Meetup.
  • Embedded Rust for Duffers
• 2026-10-05 | München, DE | Rust Munich
  • Rust Munich 2026 / 3
• 2026-10-08 | Oslo, NO | Rust Oslo
  • Rust Hack'n'Learn at Kampen Bistro
• 2026-10-08 | Geneva, CH | Rust Geneva
  • Rust Meetup Geneva
• 2026-10-14 | Barcelona, ES | BcnRust
  • 22nd bcnrust session
• 2026-10-14 - 2026-10-17 | Hybrid (Barcelona, ES) | EuroRust
  • EuroRust 2026
• 2026-10-20 | Leipzig, DE | Rust - Modern Systems Programming in Leipzig
  • Topic TBD

North America

• 2026-10-01 | Saint Louis, MO, US | STL Rust
  • Building a Minimal, Rootless Container in Rust
• 2026-10-03 | Boston, MA, US | Boston Rust Meetup
  • Alewife Rust Lunch, Oct 3
• 2026-10-08 | Lehi, UT, US | Utah Rust
  • Lightning Talks N' Chill
• 2026-10-08 | New York, NY, US | Rust NYC
  • Rust NYC: Zero Knowledge Proofs & GPUs in Rendering
• 2026-10-08 | San Diego, CA, US | San Diego Rust
  • San Diego Rust October Meetup - Back in person!
• 2026-10-10 | Boston, MA, US | Boston Rust Meetup
  • Back Bay Rust Lunch, Oct 10
• 2026-10-14 | Los Angeles, CA, US | Rust Los Angeles
  • Rust LA October: AI & Rust w/ Oxen.AI & Origin Lab!
• 2026-10-20 | San Francisco, CA, US | San Francisco Rust Study Group
  • Rust Hacking in Person
• 2026-10-21 | Hybrid (Vancouver, CA) | Vancouver Rust
  • Disposable Agent Sandboxes in Rust
• 2026-10-21 | San Francisco, CA, US | Bay Area Rust
  • Bay Area Rust - Embedded Meetup
• 2026-10-28 | Austin, TX, US | Rust ATX
  • Rust Lunch - Fareground

South America

• 2026-10-08 | Buenos Aires, AR | Rust en Español
  • WebApp Ergonomics y Secretos Distribuidos.

If you are running a Rust event please add it to the calendar to get it mentioned here. Please remember to add a link to the event too. Email the Rust Community Team for access.

Jobs

Please see the latest Who's Hiring thread on r/rust

Quote of the Week

The community is obnoxiously helpful. I asked a simple question on the Rust community Discord server. What is the best way to read a file in Rust? I expected a straightforward response. Instead, I got back a 2,000-word essay on the inner workings of IO, buffering, error handling, and ownership, plus links to four different blog posts and three different approaches depending on file size, and a working code example.

...

The Rust community has weaponized education against me. I'm now a better engineer than I was yesterday against my will.

- tris on youtube

Thanks to MusicalNinjaDad for the suggestion!

Please submit quotes and vote for next week!

This Week in Rust is edited by:

• nellshamrell
• llogiq
• ericseppanen
• extrawurst
• U007D
• mariannegoldin
• bdillo
• opeolluwa
• bnchi
• KannanPalani57
• tzilist

Email list hosting is sponsored by The Rust Foundation

Discuss on r/rust

30 Sep 2026 4:00am GMT

On September 29, Firefox 157 shipped Nova, the biggest refresh of the Firefox interface since Proton back in 2021. The browser frame is cleaner, the sidebar plays a bigger role, and vertical tabs are a first-class layout. Your theme continues to load, and most color and image properties work as they did before.

What does change is where those colors and images display, how some of them look next to each other, and a handful of properties that no longer have a visible effect. Most themes will look fine. Some, especially themes built around a background image, look different enough that you will want to take a look.

This post walks through what changed compared with the Proton interface, what to check in your theme, and what is still being worked on. If you only have five minutes, jump to the checklist.

What changed in the browser frame

The toolbar and sidebar now sit flush with the window edges, with no gaps between them.

For your theme, this means your frame color and background image have less empty space around them, and the edges where the toolbar, sidebar, and page meet are more visible.

Area	Proton	Nova (Firefox 157)
Toolbar and sidebar	Flush with the window, no gaps or floating borders	Same as before
Horizontal tabs	Theme background applied to the tab strip	Same as before
Vertical tabs	Tab bar color on the tab strip	Tab bar color also shows on the toolbar
Sidebar	Separate panel	Shares the theme background with the toolbar area

colors, accents and tabs

Accent color. The default Firefox theme uses Nova's purple accent. Every other theme, including yours, uses the operating system's accent color for buttons and other accented controls. Themes cannot set the accent color through the manifest, and is why your theme cannot show the purple you see in the default theme.

Focus and link colors. Firefox still applies its own blue and cyan to focus rings and some links when a theme other than the default is active.

The selected tab. Proton always drew a shadow under the selected tab, which helped it stand out even when a theme did not style it. Nova removes that shadow. If your theme relies on it, the selected tab can blend into the tab strip. Set the selected tab colors, with tab_selected and tab_line, so the selected tab stands out.

Button hover colors. Your button_background_hover and button_background_active colors also apply to buttons on the tab strip, and for buttons that sit on your frame background with vertical tabs. A solid color picked to match the toolbar can almost disappear there. Semi-transparent colors, for example rgba(0, 0, 0, 0.15) for hover and rgba(0, 0, 0, 0.3) for pressed, work on both backgrounds.

Sidebar and vertical tabs

• The sidebar shares your background. The theme background now continues under the sidebar, so the sidebar and the toolbar area appear as one surface.
• Set sidebar colors explicitly. Use sidebar and sidebar_text for sidebar panels. If you leave them out, Firefox picks colors for you, relevant to your theme's color.
• sidebar_border is now a separator. The sidebar splitter is gone; the property now colors the line between the sidebar and the page.
• Sidebar buttons follow your text color. Buttons and icons in the sidebar are derived from your text color rather than your toolbar button colors, so they can look slightly different from the toolbar.
• Vertical tabs and the toolbar. With vertical tabs, your tab bar color is also applied to the toolbar. If those two colors were chosen to contrast, check how they look together.
• Expand on hover. In Firefox 157, a sidebar that expands on hover may not show your theme's background. This is fixed in Firefox 158.

Properties that changed or no longer work

Some theme properties behave differently in Nova. Your theme still loads if it uses them; they just have no visible effect, or style something different.

Property	In Nova
ntp_text	No longer styles the new tab page search box
popup_text	No longer styles the address bar dropdown; other popups still use it
sidebar_highlight	No visible effect; the default highlight color is used
sidebar_highlight_text	No visible effect
toolbar_bottom_separator	Acts as a separator next to or below the toolbar and around the page

The theme manifest reference on MDN is being updated with these changes.

Themes with background images

Themes using images are where you are most likely to see a difference. Your image can now show behind the sidebar and vertical tabs, and an image designed for a wide, short toolbar rarely looks good stretched or tiled down a vertical panel. In our testing of popular themes, the image themes that look off in the sidebar mostly did before Nova too. We did test a number of themes but we invite you to do your own testing. Nova makes the sidebar more visible, so the issues are easier to notice.

You can now choose where your images go with the backgrounds_area property, available from Firefox 156:

• "auto" (the default): Firefox decides from additional_backgrounds_alignment. If any image is aligned to the vertical center or bottom, images stay in the top toolbars; otherwise they cover the whole window.
• "window": images cover the whole window, including behind the sidebar and vertical tabs.
• "top_toolbars": images stay in the toolbars at the top of the window, and the sidebar uses your frame color.

If your image was made for the toolbar only, "top_toolbars" with a frame color that suits the image is usually the quickest fix.

Also set a toolbar color, even a semi-transparent one. Without it, notification bars that appear above the page sit directly on your image and can be hard to read.

New Gradient Support

Nova's color themes use gradients, and you can too. The Nova theme manifests are the best working example; look at how they set colors for each surface, including the sidebar. backgrounds_area applies to gradients the same way it applies to images. Older versions of Firefox ignore color properties they don't recognize, so your theme still loads there; if you use a feature older versions reject, set strict_min_version in your manifest.

Checklist: what to check in your theme

Install your theme in Firefox 157 and look at it in each of these states:

1. Horizontal tabs and vertical tabs.
2. Sidebar closed, open, and expanded on hover. Also toggle "Customize sidebar" while the sidebar is open or expanded.
3. Compact density, if your users are likely to use it (under settings -> appearance density(.
4. A private window.
5. Light and dark system settings, since the accent follows the operating system.
6. Hover over the buttons on the tab strip.

Then, if something looks off:

• Set tab_selected and tab_line so the selected tab stands out without Firefox's old shadow.
• Set sidebar and sidebar_text to colors that match your theme.
• Use semi-transparent button_background_hover and button_background_active colors.
• Check that your tab bar and toolbar colors work together with vertical tabs enabled.
• For image themes, choose a backgrounds_area and set a toolbar color.
• Remove or ignore properties that no longer have an effect.
• Publish an update on AMO so your users get the changes.

What we are still working on

Nova will evolve after launch. Firefox 158 ships on October 13 with the expand-on-hover sidebar fix. We are also working on these, with no release date yet:

• Focus and link colors that fit your theme instead of the fixed blue and cyan.
• A popup_icons color for icons in menus and panels, separate from toolbar icons.
• Theme colors for hover and selected states inside sidebar panels.
• Better hover states for tab strip buttons.

We will post again when these land.

For users who prefer the old look

Some of your users may miss Proton. From September 29, Mozilla is featuring a Firefox Proton theme in the Add-ons Manager for anyone who wants the previous look. It is a normal theme, so users can switch between it and yours at any time.

Resources

• Theme manifest reference on MDN: every color, image, and property, including backgrounds_area.
• Static themes on Extension Workshop : updated for Nova.
• Nova theme manifests: worked examples for gradients and sidebar colors; the themes themselves are on AMO, for example Nova Sun.

Questions?

We want your theme to look its best in Nova. If something looks wrong and the checklist does not fix it, tell us on Discourse and include a link to your theme and a screenshot. Those reports help us find the cases that need a Firefox fix rather than a theme change.

Thank you for making Firefox look like you and like your users.

The post Nova is here: what changes for your Firefox theme appeared first on Mozilla Add-ons Community Blog.

29 Sep 2026 3:34pm GMT

What comes to mind when you think of Firefox? Is it our best-in-class privacy features and ad blocking capabilities? Our partnerships with Wrexham, NVIDIA or Mistral? Or maybe our adorable mascot Kit?

If you've been following Firefox this year, you've seen us add new ways to get things done while giving you more choice over how you browse. That includes browsing two pages side by side, adding an extra layer of privacy with built-in VPN, blocking trackers for smoother scrolling and faster load times, and deciding how AI shows up in Firefox.

For the past few months, many of you have also been trying out our new Firefox design in Nightly and sharing your thoughts with us as we continued to refine the experience.

Today, we're rolling out that design with FX 157 to everyone using Firefox across desktop and mobile devices. Firefox has done a lot of growing over the last year; now it looks the part.

A more modern Firefox

When we first shared our plans to design Firefox for the future, we said we wanted Firefox to feel "current, but not generic. Warm, but still precise."

That design ethos now carries across all of Firefox. We've refreshed the colors, icons and themes throughout the browser, from the tabs and toolbars you use every day to your New Tab page, Private Browsing experience and more, with no cost to your browser performance.

This shared design language across desktop and mobile gives Firefox a consistent foundation for new features and experiences, while keeping the personality that makes Firefox unique.

Make Firefox yours

We've added more choices for how Firefox looks and works, including the return of a feature many of you asked for:

Compact Mode is back. As people started trying the new design, we heard from many of you who wanted to fit more into your browser window. Compact Mode reduces the size of your tabs and toolbar to give more of your screen to the web, with an auto-compact option for smaller screens.

Find your look. A new theme picker makes it easier to explore different looks for Firefox, with new themes and wallpapers to choose from.

Set up New Tab your way. Choose what you want to see on your homepage. Now, you have a dedicated space to pin and organize shortcuts so sites you use all the time stay put.

Refined, not reinvented

Themes and wallpapers may change over time, but the things that made people choose Firefox in the first place are still the same. We're still independent and open source, with privacy protections built into the browser and controls that put you in charge of how Firefox works for you.

This carries through everything we build, from the height of your toolbars and what belongs on your New Tab page to which AI features show up in your browser, which model you choose and what context you want it to have.

Today's Firefox is a renewal, grounded in the same principles that have shaped it from the beginning, with a new design built to carry Firefox forward.

For those who have come with us on this journey, thank you for helping us shape the future of Firefox.

If you've been away on hiatus, welcome back. Try the latest Firefox and let us know what you think.

The post More modern. More flexible. Still Firefox. appeared first on The Mozilla Blog.

29 Sep 2026 1:00pm GMT

Highlights

• Rév O'Conner added a settings popup to control the layout of the Inspector. "Auto" automatically switches the layout at a given toolbox width.
  • 
• The new sidebar (sidebar.revamp) and switcher setting will be enabled by default for users along with Nova in DevEdition, Beta and Release channels. To ease the transition for old sidebar users, the "Open tools from sidebar" option will be unchecked for those users to more closely resemble the old sidebar experience. The migration won't apply to users who had already tried the new sidebar and reverted back.
• The custom wallpaper library for the New Tab page is coming along! This allows you to save multiple images to your wallpaper folder, rather than replacing one image at a time. While it's still in development, you can test it by setting browser.newtabpage.activity-stream.newtabWallpapers.customWallpaper.library.enabled to true, starting in Firefox 157.
  • 
• Mark added an MDN search engine for Nightly and Developer Edition. Select it from the menus, or type @mdn <search term>.
  • 
  • 

Friends of the Firefox team

Resolved bugs (excluding employees)

Script to find new contributors from bug list

Volunteers that fixed more than one bug

• :Benjamin Peterson
• Amadi
• any1here
• Caleb Pickard
• Chris Vander Linden
• Gopalarathnam Venkatesan
• Igor [:ExplodingJoysticks]
• Khalid AlHaddad
• Lukáš Lipinský
• Mayank Bansal
• Nazeer Ahmed Shaikh
• Noah Varghese
• Sameem [:sameembaba]
• Sebastian Zartner [:sebo]
• sfshah
• Xiaosen Zhuang

New contributors (🌟 = first patch)

• Amadi:
  • Network monitor opens files in last tab
  • Remove the unused _discarded field in UrlbarParentController.sys.mjs
  • Update comments that point at the removed openUILinkIn function
  • Screenshot default filename contains trailing whitespace on pages without title
• Caleb Pickard
  • 🌟 Remove BROWSER_SEARCH_PREF constant
  • The phrase "The count URI loads…" appears repeatedly in the search telemetry code. It should read "The count *of* URI loads…"
• dchen705: Remove unnecessary module import in browser/components/urlbar/tests/browser/head.js
• Ekerin Agboola: Remove old documentation related to the removed SEARCH_SUGGESTIONS_LATENCY_MS histogram
• Igor [:ExplodingJoysticks]:
  • Cleanup dead code in PageThumbs (preserveAspectRatio)
  • Dead code in services/crypto/modules/utils.sys.mjs#
• Gopalarathnam Venkatesan:
  • "Add class" button (.cls) should be disabled when a class can't be added to the selected node
  • Remove unused lightweightThemes.getMoreURL pref
  • Remove orphaned selectHistoryMode JSDoc from browser/components/preferences/tests/privacy/head.js
  • gBrowser.selectedTabs does not return tabs in tab order
• 🌟 Jieke Jiang: Remove unused AboutReaderParent._getArticle
• 🌟 Andrew: White flash on startup caused by abouthome_cache storing incompatible startup frame
• 🌟 Rév O'Conner: Inspector does not respect panel layout
• 🌟 Kana: browser_privatebrowsing_resetPBM.js awaits an array instead of Promise.all, so the tab-close wait does nothing
• Raúl: L10nCache.add() throws on an unknown Fluent ID instead of reporting it
• 🌟 Samuel Mbabhazi: Use new color syntax throughout the DevTools
• K: "Go to line" sets a cursor line which does not exist in footer location indicator
• sfshah:
  • Turn devtools/client/jsonview/converter-child.js into an ES class
  • 🌟 Fix misspellings in SearchService.shouldShowInstallPrompt
• Nazeer Ahmed Shaikh
  • Remove deprecated logs from tt(c) harness
  • 🌟 test_dont_suggest_default_engine task is duplicated in browser_contextualsearch.js mochitest
• Noah Varghese:
  • Make browser/components/syncedtabs/sidebar.xhtml an HTML file
  • 🌟 Remove usages of "six" from toolkit/components/telemetry/tests/marionette/
• Valerie Racine (:v-racine): Fix incorrect assertion message in browser_adoptTab_failure.js
• 🌟 Xiaosen Zhuang:
  • Fix the undefined -border-color-dead-row custom property in aboutMemory.css
  • Use documentGlobal instead of the removed ownerGlobal in FormAutofillPreferences

Project Updates

Add-ons / Web Extensions

Addon Manager & about:addons

• As part of Project Nova related work:
  • Fixed responsive layout issues that caused horizontal scrolling in about:addons at high zoom levels - Bug 2059864
  • Fixed the "Discover extensions" button appearing multiple times in about:addons - Bug 2070281
  • Added telemetry for theme-picker shown events and for appearance/native-theme changes in about:addons - Bug 2069417 / Bug 2070341
  • Added an accessible name to the themes mode control in about:addons, fixed in Firefox 158 and uplifted to the Firefox 157 beta channel - Bug 2064563
    • Thanks to Mark Kennedy for the help on fixing this accessibility gap
  • Updated the built-in dark and light theme previews to use the nova style - Bug 2070274
    • Thanks to Emilio Cobos Álvarez for the fix to the default light and dark theme previews.
  • Fixed the Nova default and AMO curated theme previews to follow the OS light/dark mode while ignoring the Website appearance setting, fixed in Firefox 158 and uplifted to the Firefox 157 beta channel - Bug 2070562
• Stopped setting unused taarId session cookies for AMO on startup - Bug 1871561
  • Thanks to Manuel Bucher for helping us to clean up these unused internals.

WebExtension APIs

• Fixed webRequest requestBody parsing so POST form fields named __proto__ are no longer dropped - Bug 2061470
• Changed alarms.clearAll() to resolve with undefined instead of a boolean, starting in Firefox 157 - Bug 2067229
  • Thanks to Ollie Hensman-Crook for the fix to the alarms API.
• Implemented native messaging support via xdg-native-messaging-proxy for Flatpak and Snap builds - Bug 1955255
  • Thanks to Jan Horak for the native messaging work on Linux packaging.
• As part of Florian Quèze effort to investigate and fix intermittent failures:
  • Made windows.update() wait for the window to actually resize or move before resolving, fixing an intermittent Linux test failure - Bug 1307759
  • Fixed a pageAction popup incorrectly opening via a commands API shortcut while the extension was already shutting down - Bug 2039637
  • Fixed action.openPopup() rejecting when a tab hover preview was showing, a regression from Bug 2022281 in Firefox 150, with the fix shipping in Firefox 157 and no uplift planned - Bug 2062229

DevTools

• The team has a few sizable ongoing projects.
  • Bomsy is working on moving Stylesheets to the Debugger so we can retire the (XUL-based) Style Editor, and turn the Debugger into a "Sources" panel (keeping all the existing functionality of course). (pref: devtools.debugger.features.stylesheets-in-debugger)
  • Alex is investigating ways to better handle CSS authored text and CSSOM changes in the Inspector, building information directly from the Rust CSS engine, with the hope it will bring performance improvement editing styles in the Rules view.
  • Nicolas is implementing a way to show to the user how the engine goes from a CSS declaration value to the computed value so it's easier to follow what's the result of the different call sites, or how the different units (em, %, vmin, …) are computed to their final (e.g. px) values. (pref: devtools.inspector.css-explainers)

External contributions

• Chris Vander Linden finalized a multi-months project to add a search toolbar in the Netmonitor Raw Response panel, adapting and reusing the component we are using in the Debugger (#1941575)
  • 
• Amadi made the "Open in new tab" context menu entry to open tab next to the selected tab, not at the very end of the tab list (#2059979)
• Mayank Bansal optimized the performance of console.clear() (#2068156, #2068157, #2067000)
• Benoit added JSON Lines (JSONL/NDJSON) support in the Netmonitor Response panel (#2059673)
• Gopalarathnam Venkatesan made the "Add class" button (.cls) to be disabled when a class can't be added to the selected node (e.g. it's a text node, or a comment, or the doctype node) (#2000150)
• K fixed an issue with the "Go to line" action in the Debugger (#2064575)
• Samuel Mbabhazi refactored our CSS codebase to use new color syntax (e.g. rgb(255 0 0) instead of rgb(255, 0, 0)) (#2054228)
• sfshah turned devtools/client/jsonview/converter-child.js into an ES class (#2004273)

Team/Project Update

• Florian Quèze [:florian] is working on fixing test flakiness in devtools/client/debugger and already landed an impressive stack of patches (#2001947, #2070917, #2070920, #2070932, #2070970, #2027953, #1932082, #2070923, #2070933, #1814093, #1868969, #2071238)
  • that also includes fixing various accessibility issues that were spotted by a11y_checks #2070911, #2070955, #2071227, #2071231)
  • Note that Julian Descottes [:jdescottes] also has an ongoing quest to reduce intermittent failures in our codebase and fixed a few those last 2 weeks (#1767707, 2069100, #2009386)
  • [florian] 24 patches landed on Friday, you can see the impact on https://tests.firefox.dev/tests.html?path=devtools%2Fclient%2Fdebugger
• Nicolas Chevobbe [:nchevobbe] fixed a few issues spotted by Jake in the Inspector for the new-ish attr()CSS function (#2068479, #2068480, #2068483)
• Alexandre Poirot [:ochameau] fixed an OOM crash when viewing source mapped file for a large wasm module with many workers (#2058286)
• Julian Descottes [:jdescottes] improved performance of the Inspector when Devtools was opened on a page with many grid elements (#1988868)
• Hubert Boma Manilla (:bomsy) fixed an infinite loop in the Debugger search if you were searching for $ on a big JS file (#2068517)

WebDriver

• Sameem merged two internal helpers (remote/shared/Sync.sys.mjs and remote/marionette/sync.sys.mjs) which removed some code duplication.
• Khalid AlHaddad unified the navigation commands in Marionette and WebDriver BiDi to always initiate navigations via browsingContext.loadURI().
• Khalid AlHaddad updated the WebDriver BiDi client used by WebDriver tests so that browsing_context.locate_nodes returns the nodes array directly instead of the enclosing result object, matching the updated command response.
• Julian Descottes made the destinationFolder mandatory when calling the browser.setDownloadBehavior command with type="allowed" - which aligns us with the specification. In order to restore the default behavior without having to specify a folder, clients should call setDownloadBehavior with null instead.
• Henrik Skupin fixed a bug in geckodriver where specifying androidIntentArguments in the capabilities caused the default intent arguments to be omitted.

Fluent

• According to arewefluentyet.com, ~74.77% of our strings are now using Fluent!

Lint, Docs and Workflow

• According to arewemozsrcyet.com, ~59% of our modules are now using moz-src.
• eslint-plugin-mozilla has switched from using Mocha to Jest for tests.
  • Planning on future updates to investigate getting devtools & newtab to use the jest installed at the top-level, rather than separately installed copies.

Information Management/Sidebar

• We're working away on bug fixes for sidebar, vertical tabs, split-view, and Nova
• Thanks Florian (:fqueze) for landing a set of patches that have markedly reduced test flakiness in the Sidebar component

New Tab Page

• Custom wallpaper library
  • Dre added a "Your images" folder to the wallpaper picker on the New Tab Page, letting users save and switch between multiple custom wallpapers directly from the picker UI (desktop channels), which reduces friction for users who frequently change backgrounds.
  • Dre implemented storage and migration for multiple custom wallpapers so users keep their existing wallpaper during upgrade while gaining the ability to save and switch multiple wallpapers - migration moves old single-wallpaper prefs into the new multi-wallpaper storage and the NTP now reads the wallpaper array at load/sync points.
  • Dre updated New Tab Page strings to support multiple custom wallpapers so users now see accurate, localized labels and accessibility text when managing or switching between multiple custom backgrounds, reducing confusion in the UI during wallpaper selection.
  • Dre added a delete affordance for saved custom wallpapers inside the New Tab Page picker so users can remove unwanted images from their saved set without going to profile files or prefs, improving manageability of user-provided wallpapers.
• We've completed a mass migration of our unit tests from Mocha (not mochi) / Karma to Jest/RTL, which is more modern and actively maintained.
• Sections is now enabled globally for all regions that show the content feed!
• Reem Hamoui fixed Lists widget so that keyboard users can now tab to completed items on the New Tab Page and see a visible selection/focus state
• Reem Hamoui fixed the Timer widget so that keyboard users can toggle focus vs break modes with standard keys (Enter/Space/arrow keys) thanks to restored keyboard handlers and tabindex semantics.
• Reem Hamoui made it so that screenreaders now announce wallpaper names via added aria-labels/alt text and role improvements in the Customize UI.
• Maxx Crawford made it so that the Customize UI now filters wallpapers by their metadata and no longer surfaces images marked hidden or in specific visibility groups.
• Irene Ni added Section Layout Name (String) telemetry to newtab content impression & click events so impressions/clicks now carry layout identifiers for more granular UX and A/B analysis
• Reem Hamoui added accessible names (aria-label/aria-labelledby) to the HNT Customize panel back buttons to fix screen-reader discoverability and keyboard/AT announcement when navigating the New Tab Customize flow.
• Nina Pypchenko [:nina-py] preserved iframe rendering for New Tab Page widgets during drag operations to prevent iframe-backed widgets from going blank while being moved.
• Nina Pypchenko [:nina-py] restored the Stocks widget dropdown and menu visibility under High Contrast Mode by adjusting contrast-aware CSS and ARIA roles so users relying on HCM can access stock controls again.
• Nina Pypchenko [:nina-py] fixed a results text overflow for long search queries in the Stocks widget by adding word-wrap/clamping to result lines, preventing layout breakage and truncated controls when users enter long symbols or queries.
• Nina Pypchenko [:nina-py] added telemetry for theme selection in the New Tab customization panel by emitting a selection ping on change, enabling measurement of user theme choices without changing UX.
• Irene Ni restored the Lists widget switcher checkmark for the selected list by fixing menu item selection-state rendering so users can again see which list is active in the switcher.
• Reem Hamoui updated the Privacy widget CTA and spacing on the New Tab Page, adjusting CSS/layout and CTA copy so the action is more discoverable and has a clearer tap/click target across responsive breakpoints.
• Reem Hamoui updated the zero-state copy for the New Tab Privacy widget to clarify what the widget does and the next steps for users when no privacy events or trackers are present, reducing confusion for first-time or cleared-state users.
• Maxx Crawford landed Fluent strings for the Nova launch New Tab customization callout, enabling localized text in the New Tab customization callout so users in supported locales see translated UI instead of missing-string fallbacks.
• Nina Pypchenko made the customization panel reset when closed, ensuring about:newtab customization state (temporary tile/layout previews) is cleared on close so users no longer see stale previews when reopening the panel.
• Dão Gottwald fixed New Tab to pick up system High Contrast Mode on Linux and macOS, restoring correct high-contrast colors/contrast on those platforms for users who rely on OS-level accessibility settings.
• Irene Ni restored theme matching for New Tab context menus by reapplying theme-aware CSS variables in the New Tab Page contextmenu styles, fixing mismatched colors for users with custom/light/dark themes.
• Dustin Whisman fixed New Tab section context menu button color regression by adjusting the section-contextmenu button style rules (button color variables and state selectors) so section actions now respect theme contrast.
• Irene Ni restored transparency to New Tab card backgrounds by removing opaque background rules so cards correctly display background images/themes and improve visual consistency across DPI/compositing setups.

Picture-in-Picture

• Thanks to Sebastian Zartner [:sebo] for fixing broken Dailymotion captions on the PiP player.
• kpatenio fixed YouTube's displayed playback speed settings being out of sync with PiP.
  • Reminder that the playback speed settings can be enabled with media.videocontrols.picture-in-picture.playback-speed.enabled.
  • 
• Thanks to Sylvestre Ledru [:Sylvestre] for helping fix a broken link in our PiP docs as a part of Bug 2071683.

Search and Urlbar

Address Bar

• Dao and Moritz are working on bringing the full urlbar experience into the newtab page, now enabled on nightly and going through polish and improvements.. (Bug 2068104, Bug 2068633, Bug 2069260, Bug 2064747)
• Drew enabled AMP and Wikipedia by default in AT, BE, CH, ES, IE, LU, NL, PL, PT and SE. (Bug 2066294)
• James gated adaptive autofill page results behind a minimum score threshold. (Bug 2066171)
• any1here stopped disabled Manage AI and Labs quick actions being displayed when disabled. (Bug 2070378)

Search

• Dale landed the Recent Searches widget which will be be used launched as an experiment (Bug 2063718)
  • 
• Caleb fixed the search box eating the first character typed into it. (Bug 1953361)
• Mark configured Wikipedia search for Sardinian (sc) to use the Sardinian Wikipedia rather than the Italian one. (Bug 2057690)

Places

• Marco fixed bookmarked Google Maps using Google's default favicon. (Bug 1575809)
• Marco fixed the Downloads and History windows going full-screen instead of floating on macOS. (Bug 2058062)

Tests

• Dashboards:
  • Most frequent oranges: https://tests.firefox.dev/intermittent.html#date=21days
  • Folders with the most flaky tests: https://tests.firefox.dev/flaky.html?kind=mochitest#date=21days&view=list
  • Issues of tests in a given folder: https://tests.firefox.dev/tests.html
    • Eg devtools debugger tests shows progress of the recent effort to fix these tests recently
• Flakiness burn down
  • Multi-agent Claude sessions running for hours investigating and fixing tests of a given set provided in the prompt. Still iterating on the process. Did this 3 times so far:
    • Bug 2062142 - [meta] Fix the flakiness in browser/components/extensions/test/browser
    • Top 20 intermittent mochitest bugs annotated by sheriffs.
      • Probably what made the mochitest line go down for the first time on https://tests.firefox.dev/
      • And what helped with the sidebar component, even though sidebar wasn't my target.
    • Bug 2070797 - [meta] Fix the flakiness in devtools/client/debugger/test/mochitest
      • https://tests.firefox.dev/tests.html?path=devtools%2Fclient%2Fdebugger%2Ftest%2Fmochitest
• Profile your claude session for cost and context size: https://github.com/fqueze/claude-profiler
  • To monitor cost during your sessions, try https://github.com/padenot/foxtail

28 Sep 2026 7:31pm GMT

Bugs resolved in Moz-Phab 2.21.0:

• bug 2068637 code review bot fails to apply patches when the parent is not known
• bug 2073291 moz-phab submit could load reviewers and review groups in parallel with revisions and diffs
• bug 2075401 "Phabricator Error: Validation errors" from moz-phab submit should display the revision

Discuss these changes in #engineering-workflow on Slack or #Conduit Matrix.

1 post - 1 participant

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25 Sep 2026 6:18pm GMT

We spend a lot of time browsing online. Whether you are researching for work, planning a trip, paying your bills, or scrolling through social media, your browser is there for it all.

While all these tasks are very different in nature, a lot of people still tend to stick to the same window type for all their use cases. But what if there was a different way to browse?

You may have noticed Firefox now has three window options for desktop. On top of the Classic and Private windows you've known for years, a third choice has been rolling out in beta: Smart Window. This optional AI-powered browsing experience is built to move your work forward and help finish what you started online.

Following the recent addition of several new Smart Window capabilities, we thought now would be the perfect time for a breakdown of what each of our three window options actually does, and when to use them.

Classic: Timeless and tailored to you

Classic Window is still the most customizable option of the three. While Private and Smart windows share many of the same features and capabilities as Classic, a Classic Window offers the widest range of Firefox's standard personalization options. It gives you the broadest canvas for tailoring Firefox to the way you browse.

What makes it Classic:

• Full oversight over controls, buttons, and toolbars.
• Access to the entire Firefox add-ons library.
• Advanced customization and configuration options.
• The ability to sync your history, bookmarks, and open tabs across your signed-in devices.

When to use it:

Classic is your home base. It's the best place to start customizing around your browsing needs, whether that means an extension setup specifically tailored to your workflow, a special theme that matches your style, or just the familiar Firefox experience you created over years of tweaking to your personal taste. While many customizations are also available on Private and Smart window, Classic offers the most extensive line-up of optional browser features, extensions, and aesthetics to personalize your setup.

Classic is the right move for general browsing like scrolling through social media, conducting a quick Google search, or reading online articles. It's also the best place to start if you are looking to build your browser around you.

Private Window: Browse with greater peace of mind

Private Window stays true to its name and number one priority: it's designed to limit the information associated with your browser session. When a Private Window is closed, Firefox doesn't retain session information, such as what you searched for, the sites you visited, or the cookies they set.

What makes it Private:

• Pages visited from a Private Window will not be added to the list of sites in Firefox's History menu, the Library window's history list, nor the address bar drop-down list.
• Nothing entered into text boxes on web pages and Search bar will be saved for Form autocomplete.
• Cookies set in a Private Window are kept only temporarily in memory, separate from your regular cookies, and are discarded after your last Private Window is closed.
• Extensions are off by default in a Private Window, unless you explicitly grant them permission.

When to use it:

A Private Window is recommended when you don't want activity from a browsing session sitting in your history, such as shopping for a gift. It's also helpful when browsing on a shared device, ensuring your history, logins, and cookies will not be saved for the next person.

You may not need a Private Window every time you open your browser, but it's always there for you when you do.

Smart Window: Firefox's privacy-first, AI-powered browsing experience to help get stuff done

Smart Window is Firefox's newest window type, currently rolling out in Beta to users in the U.S., Canada, and France. Think of it as a Classic Firefox window with a built-in AI assistant layered on top - one that you can choose to have utilize your open tabs, recent browsing, and the page in front of you, so it can help you do more without switching contexts - all with the privacy and security you expect from Firefox.

What makes it Smart:

• A built-in assistant that can summarize pages, generate recommendations, compare information, and plan tasks using your open tabs.
• The ability to retrieve current web information and display the sources behind its response without taking you to a separate search results page, supported by Firefox's new partnership with Exa.
• Suggested groups for related tabs.
• Visual previews of pages from your browsing history, so you can surface the page you're looking for more easily among similar results without opening each one.
• The choice of three AI models to power the assistant, as well as the option to bring your own model.
• Optional "memories," built from either your Smart Window chats or your browsing activity in both Smart and Classic windows, or both. Memories help the assistant give you more helpful, personalized answers over time. They are stored locally on your device and can be deleted at any time.

When to use it:

Smart Window shines when you need a little extra help finishing what you started. Its ability to work with the context you choose to share can help you make progress on ongoing tasks that may require more than one session, like trip or event planning, comparison price shopping, or conducting research for work or personal reasons.

And with Smart Window's optional memories, which learn your patterns and preferences over time (with your permission), Smart Window gets more useful the more you use it, keeping you from having to spell everything out from scratch each time.

Selecting the right window for the job

None of these windows is "better" than the others, they're built for different moments.

The good news is you are never locked into one. Firefox lets you move between all three depending on what you're doing, so you can choose the window that fits each task.

You can access Classic and Private windows at any time from the Firefox menu. As for Smart Window, it remains in beta, with current availability to people in the U.S., Canada, and France.

To try Smart Window, visit https://www.firefox.com/smart-window. Or, if it's not available in your region yet, you can sign up to be notified when it is.

The post Classic, Private, or Smart? Choose the right Firefox window for every task appeared first on The Mozilla Blog.

24 Sep 2026 5:00pm GMT

Greetings once more from the Thunderbird development team!

As the Northern hemisphere summer comes to an end and a slew of PTO, company holidays and projects have wrapped up, what better time to share progress and next steps on the work the Thunderbird Desktop Engineering team has on their plates!?

Exchange support moving well

The powerhouse Exchange engineering team had some great momentum over the summer and completed their work on implementation of the Graph protocol to support email accounts - well in advance of their deadline. They have since moved on to start work to support Exchange calendars using the Graph protocol which is a significant milestone given that our calendar code hasn't had significant changes for some time.

While some team members are now juggling multiple projects, good progress has been made to wrestle the foundations into place, with calendar discovery and persistence in place, along with display of calendar items. Following a brief hiatus to focus on other priorities, the team is once again back into gear.

Keep track of our Graph API Calendar implementation here.

Account Setup & Authentication

Since I last wrote, many of the account setup and account authentication improvements have landed (mostly in versions 156 & 157), unlocking some important security use cases which are becoming more frequently requested and mandated by organizations and legislation around the world.

While diving into the code is an enjoyable adventure, the newly-minted articles devoted to the topic of Oauth customization might be a better starting point for most:
Knowledge Base - Custom OAuth for Thunderbird

UI overhauls - why just one?!

The front end engineering team has completed the rebuild of our account setup manual configuration flows to include new protocol options and security customizations, so it is time to pick up where we left off on our Calendar UI rebuild.

The majority of the front end team is now either focused on Calendar Event data write operations stemming from the Event Read dialog (delete event, RSVPs, Reminders) - or beginning the largest part of the journey, which is the implementation of a new Calendar Create/Edit dialog, along with REDUX-based state management, a new WYSIWYG editor and more reusable components such as date pickers.

Follow the Calendar Event Create/Edit work here

While that work is underway, why not weave in some more improvements?!

After some extensive user research and testing, our design team has begun work to improve the Settings UI, starting with some updates to humanize and homogenize the various options, headings and guidance provided in that area of the application.

Read more about that journey here

Contributions are on the rise! Some AI guidance…

In the past few months, we've seen a wonderful increase in contributions from community members - partially thanks to our move away from Mercurial to a more familiar Git-based workflow - and partially thanks to many LLMs doing a great job of interpreting our public codebase and making it far more accessible. Or it could be that our team is just such a friendly bunch that we've attracted a great group of people willing to support.

Whatever the reason, we're happy to see new names. faces and ideas in our chats and review queue!!

Having said that…We've reached the point where the velocity of work is beginning to pile up and clog our review queue - so I felt it might be time to share some guidance to make the process easier for both external contributors and the internal review team. Bear in mind that while we use AI workflows in several areas, our goal is to preserve a codebase which can be maintained by humans. We're working on a policy that may word some of these points better, but from the past few months of my experience here's what I see as being helpful:

1. Keep patches to a digestible size and understandable complexity - Contributions should save more development time than it takes to review. If the patch contribution creates heavy work for maintainers, it will be deprioritized - so the best approach is to break the work up into pieces that can be understood more easily and discussed together. Bear in mind that many cloud-based models aren't primarily designed to be frugal with token usage so it's easy for patches to grow (much) larger than they actually need to be to solve the problem. Be specific with prompts to minimize the surface area of changes so they are reviewable.
2. Humanize or write comments (within code and throughout the code review process) by hand - While we've become accustomed to interacting with a variety of automated systems in our daily lives, a good chunk of the joy involved in our work is to share knowledge with each other and refine the code so that it can be reused and understood by humans.
3. Be wary of license infringement - much of our work is under the MPL license and we must all take care not to introduce refactored code that originally came from licensed software which can be rewritten and translated using LLM, then relabelled under our licence.
4. Be transparent - it will often help to share prompts and your model when submitting code for review. Refining all aspects of our workflow is important, and we can all benefit from a collective evolution of skills and prompts that improve over time with input from the team and community.
5. We encourage contact with a member of the team to discuss approach and architecture in advance of spending time and tokens on a patch. Some areas of the codebase are already slated for redevelopment and it's not always obvious what is underway and planned. Having a quick conversation to say "Hey, I'm thinking about working on this" is a great start to landing something that spends less time in review and uses less tokens, energy & the world's natural resources.
6. Of course if none of these guidelines are followed, we'll still be very happy to receive help from the wider community - the process may just take longer and be a bit less pleasant.

Enterprise

As parts of the world turn their infrastructure priorities toward digital sovereignty, we've seen an increase in interest from governments, institutions and organizations around the world who are looking to either improve their existing FOSS-based infrastructure or deploy for the first time. That has resulted in some focused efforts throughout Q3 to improve our Enterprise security and policy framework to bring it in line with the strides that the Firefox engineering team has made, and also roll out more Thunderbird-specific administrative mechanisms that allow granular control over end user configurations. Read more about your options and follow the work below:

Thunderbird Enterprise Policies and Relevant Preferences

Thunderbird Enterprise PoC Work Items

Maintenance, Upstream adaptations, Recent Features and Fixes

Waves of changes from upstream Firefox have continually kept the team on their toes throughout July & August, but the small but mighty gang have kept Daily builds largely intact each day. In addition, the team and contributor community have continued landing a series of reliability, stability, and usability improvements across the application. Recent highlights include:

• Nico has a series of calendar improvements in the works with several now cleared for landing: D319397, D320418, D320419
• Hurtmut has again come to the rescue with a number of patches but most recently solved a widespread filtering problem introduced upstream which will need to be uplifted as a matter of urgency.
• Richard pushed many patches since my last update, many related to upstream changes required after the Firefox project "Nova" was unleashed. He's also been on the lookout for other breaking changes such as XUL attribute modifications.
• Max was on fire and in constant comms with the team to deliver a large number of important changes but also helped to refine some of our processes relating to AI-driven workflows. Recently, he led an investigation into growing concerns over instability with connections with Gmail accounts in Bug 2028760.
• and many more which are listed in release notes for beta.

If you would like to see new features as they land, and help us find some early bugs, you can try running daily and check the pushlog to see what has recently landed. This assistance is immensely helpful for catching problems early.

-

Toby Pilling

Senior Manager, Desktop Engineering

The post Thunderbird Monthly Development Digest: September 2026 appeared first on The Thunderbird Blog.

23 Sep 2026 10:35pm GMT

Bugs resolved in Moz-Phab 2.20.0:

• bug 2066178 Drop support for Python 3.9
• bug 2068605 preserve file logging from moz-phab list --format json and moz-phab patch --raw
• bug 2071586 Review queue reminders should ignore group reviews (at least optionally)
• bug 2073088 moz-phab submit is getting the file size from hg/git even if it could infer it from the blob itself
• bug 2074036 List index out of range

Discuss these changes in #engineering-workflow on Slack or #Conduit Matrix.

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23 Sep 2026 4:45pm GMT

Hello and welcome to another issue of This Week in Rust! Rust is a programming language empowering everyone to build reliable and efficient software. This is a weekly summary of its progress and community. Want something mentioned? Tag us at @thisweekinrust.bsky.social on Bluesky or @ThisWeekinRust on mastodon.social, or send us a pull request. Want to get involved? We love contributions.

This Week in Rust is openly developed on GitHub and archives can be viewed at this-week-in-rust.org. If you find any errors in this week's issue, please submit a PR.

Want TWIR in your inbox? Subscribe here.

Updates from Rust Community

Official

• Be alert: targeted attacks on prominent Rustaceans
• GitHub Actions leaking secrets when Miri output is cached
• Maintainer spotlight: Alejandra González (@blyxyas)
• Announcing a Maintainer in Residence: Scott Schafer for the Cargo team

Foundation

• Guest Post: Rust Is Tier-1 Language at Microsoft

Project/Tooling Updates

• Fearless SIMD v1.0 is here
• Syncing Rust GCC backend or how to test Murphy's law
• Benchmarking Wild vs Mold

Observations/Thoughts

• Arguing about arguments
• Nine Rules for Vibe Validation of Vibe-Coded (Rust) Algorithms

Rust Walkthroughs

• [video] Understanding Rust Ownership by Building a Zero-Copy Log Line Parser
• Finding Bugs
• Why datadiff matches arrays by key instead of computing tree edit distance
• [video] RustCurious lesson 10: Three Ways to Fix Any Borrowing Error
• Solving for faster SHA-1 collision detection
• Small and secure Docker images for Rust: Alpine vs Debian vs Scratch

Crate of the Week

This week's crate is fastlogging-rs, a fast logger which supports 8 different programming languages.

Thanks to brmmm3 for the self-suggestion!

Please submit your suggestions and votes for next week!

Calls for Testing

An important step for RFC implementation is for people to experiment with the implementation and give feedback, especially before stabilization.

If you are a feature implementer and would like your RFC to appear in this list, add a call-for-testing label to your RFC along with a comment providing testing instructions and/or guidance on which aspect(s) of the feature need testing.

No calls for testing were issued this week by Rust, Cargo, Rustup or Rust language RFCs.

Let us know if you would like your feature to be tracked as a part of this list.

RFCs

Rust

Rustup

If you are a feature implementer and would like your RFC to appear on the above list, add the new call-for-testing label to your RFC along with a comment providing testing instructions and/or guidance on which aspect(s) of the feature need testing.

Call for Participation; projects and speakers

CFP - Projects

Always wanted to contribute to open-source projects but did not know where to start? Every week we highlight some tasks from the Rust community for you to pick and get started!

Some of these tasks may also have mentors available, visit the task page for more information.

• sysknife - A successful automatic rollback renders to the operator as unknown
• sysknife - sysknife-setup --uninstall deletes .mcp.json whole, taking every other MCP server with it
• sysknife - audit export publishes request_hash, an unsalted hash over unredacted params, with no statement of its sensitivity
• Apache Iggy - Python SDK: expose consumer shutdown and offset drain timeout
• Apache Iggy - Python SDK: expose client disconnect and shutdown lifecycle methods

If you are a Rust project owner and are looking for contributors, please submit tasks here or through a PR to TWiR or by reaching out on Bluesky or Mastodon!

CFP - Events

Are you a new or experienced speaker looking for a place to share something cool? This section highlights events that are being planned and are accepting submissions to join their event as a speaker.

If you are an event organizer hoping to expand the reach of your event, please submit a link to the website through a PR to TWiR or by reaching out on Bluesky or Mastodon!

Updates from the Rust Project

618 pull requests were merged in the last week

Compiler

• A couple polonius constraints perf improvements
• AST lowering cleanups
• an assortment of polonius tweaks
• check tainted_by_error in LateLint
• even more cleanups for rustc_builtin_macros
• perf: keep the first macro syntax-context mapping inline
• suggest fully qualified path on method name collision

Library

• add Dir::try_clone
• add case mapping fast paths for Latin-1
• complex conjugate, negation and default
• constify comparison traits on sliced types
• implement const Iterator for Range
• stabilize CommandExt::show_window
• stabilize feature(trim_prefix_suffix) ({str,[T], Path}::trim_prefix and {str, [T]}::trim_suffix)
• stabilize windows_process_extensions_main_thread_handle

Cargo

• build-rs: make unstable compile
• account for (uplift) hardlinks when calculating clean file size
• fix: return correct package specs when resolving workspace deps
• remove -Zasymmetric-token / cargo:paseto
• report the number of errors with build.warnings='deny'

Rustdoc

• Correctly handle dyn trait methods linking for jump to def feature
• Correctly handle intra-doc links on inlined same item with different names

Clippy

• add must_use_without_reason lint
• fix const_trait_impl related infinite loop in needless_borrows_for_generic_args
• generalize extend_with_drain to VecDeque and BinaryHeap
• lint suboptimal_flops for mul_add, custom_abs and radians in const context
• lint nested format_args! for uninlined args

Rust-Analyzer

• prioritise required items in trait autocomplete
• support completions inside cfg!()
• support hover on cfg predicate
• complete cfg value in string
• correct order deprecated const in builtin ty
• not complete attr args when before exists args
• watch include roots recursively once, not every directory

Rust Compiler Performance Triage

Approved RFCs

Changes to Rust follow the Rust RFC (request for comments) process. These are the RFCs that were approved for implementation this week:

• No RFCs were approved this week.

Final Comment Period

Every week, the team announces the 'final comment period' for RFCs and key PRs which are reaching a decision. Express your opinions now.

Tracking Issues & PRs

Rust

• Types FCP v2: Supertrait item shadowing stabilization
• declare C and C-unwind as mutually ABI-compatible
• Distinguish repr(C) ZSTs from others in ABI compatibility rules
• Implement Default for NumBuffer
• rustc: Stabilize the WebAssembly wide-arithmetic feature
• Allow elided ('static) lifetimes in thread_local!
• Stabilize mem::conjure_zst
• Prevent mutating the global environment pointer in CommandExt::exec and opt to use execve and resolve path manually
• Stabilize debug_closure_helpers
• Additional NonZero conversions
• Stabilize funnel_shifts (including const)
• Stabilize Result::into_{ok,err}
• windows: stabilise inherit_handles

Cargo

• OUT_DIR is also set when running the program
• feat(config): Add build.profile, install.profile
• fix(git)!: Default to net.git-fetch-with-cli if git is present

Compiler Team (MCPs only)

• Create a new tier 3 target: wasm32-webp2
• Test wasm in CI with threads & unwinding

Leadership Council

• Formulate a trusted-contributors marker team
• Participation in Outreachy Dec 2026 (dedication of funds)

No Items entered Final Comment Period this week for Rust RFCs, Language Team, Language Reference or Unsafe Code Guidelines. Let us know if you would like your PRs, Tracking Issues or RFCs to be tracked as a part of this list.

New and Updated RFCs

• No New or Updated RFCs were created this week.

Upcoming Events

Rusty Events between 2026-09-23 - 2026-10-21 🦀

Virtual

• 2026-09-24 | Virtual (Berlin, DE) | Rust Berlin
  • Rust Hack and Learn
• 2026-09-24 | Virtual (Charlottesville, VA, US) | Charlottesville Rust Meetup
  • Rust Cells - Interior Mutability from Rust Core to Tock OS
• 2026-09-29 | Virtual (London, UK) | Women in Rust
  • Lunch & Learn: Crates, Tips & Tricks Lightning Talks - Bring your ideas!
• 2026-09-30 | Virtual (Cardiff, UK) | Rust and C++ Cardiff
  • Operating Systems Book Club: Segmentation and Introduction to Paging
• 2026-10-02 | Virtual | Rust Girona
  • Sessió setmanal de codificació / Weekly coding session
• 2026-10-04 | Virtual (Dallas, TX, US) | Dallas Rust User Meetup
  • Rust Deep Learning: First Sunday
• 2026-10-06 | Virtual (London, UK) | Women in Rust
  • 👋 Community Catch Up
• 2026-10-07 | Virtual (Indianapolis, IN, US) | Indy Rust
  • Indy.rs - with Social Distancing
• 2026-10-08 | Virtual (Berlin, DE) | Rust Berlin
  • Rust Hack and Learn
• 2026-10-08 | Virtual (Nürnberg, DE) | Rust Nuremberg
  • Rust Nürnberg online
• 2026-10-10 | Virtual (Gdansk, PL) | Stacja IT Trójmiasto
  • [BEZPŁATNIE] Programowanie w języku Rust
• 2026-10-13 | Virtual (Dallas, TX, US) | Dallas Rust User Meetup
  • Second Tuesday
• 2026-10-14 - 2026-10-17 | Hybrid (Barcelona, ES) | EuroRust
  • EuroRust 2026
• 2026-10-18 | Virtual (Dallas, TX, US) | Dallas Rust User Meetup
  • Rust Deep Learning: Third Sunday
• 2026-10-20 | Virtual (Washington, DC, US) | Rust DC
  • Mid-month Rustful
• 2026-10-21 | Hybrid (Vancouver, CA) | Vancouver Rust
  • Disposable Agent Sandboxes in Rust

Asia

• 2026-09-23 | Maharashtra, IN | Rust Pune
  • Exploring standard traits in Rust

Europe

• 2026-09-24 | Aarhus, DK | Rust Aarhus
  • Talk Night at SkyTEM
• 2026-09-24 | Amsterdam, NL | Rust Developers Amsterdam Group
  • Rust Meetup @ BlockTech
• 2026-09-24 | Frankfurt, DE | Rust Rhein-Main
  • AI Agentic Coding
• 2026-09-24 | London, UK | Rust London User Group
  • Rust London, Lloyds Banking Group, with Luca Palmieri & Mainmatter
• 2026-09-25 | Edinburgh, UK | Rust and Friends
  • Rust and Friends (daytime coffee)
• 2026-09-26 | Stockholm, SE | Stockholm Rust
  • Ferris' Fika Forum #30
• 2026-09-28 | Augsburg, DE | Rust Meetup Augsburg
  • Rust Meetup #21: Maximilian Grauvogl & Marcel Fink - From Bits to Bugs: A Rust generator for SUIT Manifests and Structure-Aware Parser Fuzzing
• 2026-09-29 | Manchester, UK | Rust Manchester
  • Rust Manchester September Code Night
• 2026-09-29 | Milano, IT | Rust Language Milan
  • Why Rust is not really OOP?
• 2026-09-30 | Basel, CH | Rust Basel
  • Rust Meetup #16 @ ERNI
• 2026-09-30 | Berlin, DE | Rust Berlin
  • Rust Berlin Talks: The next generation
• 2026-10-05 | München, DE | Rust Munich
  • Rust Munich 2026 / 3
• 2026-10-08 | Oslo, NO | Rust Oslo
  • Rust Hack'n'Learn at Kampen Bistro
• 2026-10-10 | Geneva, CH | Rust Geneva
  • Rust Meetup Geneva
• 2026-10-14 | Barcelona, ES | BcnRust
  • 22nd bcnrust session
• 2026-10-14 - 2026-10-17 | Hybrid (Barcelona, ES) | EuroRust
  • EuroRust 2026
• 2026-10-20 | Leipzig, DE | Rust - Modern Systems Programming in Leipzig
  • Topic TBD

North America

• 2026-09-23 | Austin, TX, US | Rust ATX
  • Rust Lunch - Fareground
• 2026-09-23 | Austin, TX, US | Rust ATX
  • Rust Lunch - Fareground
• 2026-09-24 | Atlanta, GA, US | Rust Atlanta
  • Rust-Atl
• 2026-09-26 | Boston, MA, US | Boston Rust Meetup
  • Harvard Rust Lunch, Sep 26
• 2026-10-01 | Saint Louis, MO, US | STL Rust
  • Building a Minimal, Rootless Container in Rust
• 2026-10-03 | Boston, MA, US | Boston Rust Meetup
  • Alewife Rust Lunch, Oct 3
• 2026-10-08 | San Diego, CA, US | San Diego Rust
  • San Diego Rust October Meetup - Back in person!
• 2026-10-10 | Boston, MA, US | Boston Rust Meetup
  • Back Bay Rust Lunch, Oct 10
• 2026-10-14 | Los Angeles, CA, US | Rust Los Angeles
  • Rust LA October: AI & Rust w/ Oxen.AI & Origin Lab!
• 2026-10-20 | San Francisco, CA, US | San Francisco Rust Study Group
  • Rust Hacking in Person
• 2026-10-21 | Hybrid (Vancouver, CA) | Vancouver Rust
  • Disposable Agent Sandboxes in Rust

Oceania

• 2026-09-29 | Barton, AU | Canberra Rust User Group
  • September Meetup

South America

• 2026-10-08 | Buenos Aires, AR | Rust en Español
  • WebApp Ergonomics y Secretos Distribuidos.

If you are running a Rust event please add it to the calendar to get it mentioned here. Please remember to add a link to the event too. Email the Rust Community Team for access.

Jobs

Please see the latest Who's Hiring thread on r/rust

Quote of the Week

operational pedantics

- Clar Fon on rust zulip

Thanks to Jules Bertholet for the suggestion!

Please submit quotes and vote for next week!

This Week in Rust is edited by:

• nellshamrell
• llogiq
• ericseppanen
• extrawurst
• U007D
• mariannegoldin
• bdillo
• opeolluwa
• bnchi
• KannanPalani57
• tzilist

Email list hosting is sponsored by The Rust Foundation

Discuss on r/rust

23 Sep 2026 4:00am GMT

Github Link

The following changes have been pushed to bugzilla.mozilla.org:

Thanks to Kohei for his work on the newly revised Guided Bug Entry form! If you want to check it out yourself, then click on the Switch to Bugzilla Helper link at the bottom of the enter bug product selection page. Normally users without canconfirm permissions will see the Guided Bug page by default which a large percentage of our Bugzilla users.

• Bug 1995464 - Overhaul guided bug entry form
• Bug 2002553 - BMO rest api search: Failed to fetch key from network storage when an attachment has been deleted

Discuss these changes in the BMO Matrix Room

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22 Sep 2026 10:25pm GMT

The latest version of the Firefox Profiler is now live! Check out the full changelog below to see what's changed:

Highlights:

• [fatadel] Show a category breakdown in profiler-cli (#6256)
• [fatadel] Show allocation data in the cli (#6246)
• [Florian Quèze] profiler-cli: add a thread list command (#6273)
• [Florian Quèze] profiler-cli: add a thread list command (#6273)
• [Nazım Can Altınova] Add a permalink command to profiler-cli for already published profiles (#6331)
• [Florian Quèze] profiler-cli: add profile markers for cross-thread marker search (#6276)
• [Nazım Can Altınova] Add --with-samply to "profiler-cli load" (#6339)

Other Changes:

• [Florian Quèze] profiler-cli: name the process in the thread banner, and follow the queried thread (#6269)
• [fatadel] Drive PII sanitization from marker schemas (#6291)
• [fatadel] Move FileIO table labels into marker schemas (#6296)
• [Markus Stange] Add missing finishRawMarkerTableBuilder. (#6318)
• [fatadel] Fix the upload error button contrast (#6315)
• [Markus Stange] Allow typed arrays in the nativeSymbols table (#6300)
• [Markus Stange] Remove brittle test. (#6322)
• [Markus Stange] Fix file extension typo. (#6325)
• [Markus Stange] Typed arrays + flags for the FuncTable (#6323)
• [fatadel] Convert extension text markers to structured payloads (#6314)
• [Florian Quèze] profiler-cli: include per-marker fields and data in --list --json (#6275)
• [Markus Stange] Speed up call tree sidebar by sharing work with the activity graph (#6329)
• [Nazım Can Altınova] Sync: l10n → main (Sept 22, 2026) (#6341)
• [Nazım Can Altınova] Bump profiler-cli version to 0.10.0 (#6342)

Big thanks to our amazing localizers for making this release possible:

• el: Jim Spentzos
• ro: robbp

Find out more about the Firefox Profiler on profiler.firefox.com! If you have any questions, join the discussion on our Matrix channel!

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22 Sep 2026 4:42pm GMT

Firefox DevTools MCP (firefox-devtools-mcp) 0.10.4 is out on npm.

Changes

This release only contains additional hooks and configuration files to register Firefox DevTools MCP on various third-party aggregators, as well as a new task to automatically register the mcp on https://registry.modelcontextprotocol.io/ on release.

Full changelog: Release v0.10.4 · mozilla/firefox-devtools-mcp · GitHub
Repository and issues: GitHub - mozilla/firefox-devtools-mcp: Model Context Protocol server for Firefox DevTools - enables AI assistants to inspect and control Firefox browser through WebDriver BiDi · GitHub
Public chatroom: https://chat.mozilla.org/#/room/#firefox-devtools-mcp:mozilla.org

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22 Sep 2026 12:43pm GMT

At the end of August, we announced our first Maintainers in Residence, Rust Project contributors who are funded for their upstream contributions and maintenance work from the Rust Foundation Maintainers Fund (RFMF). Since then, the Rust Leadership Council has dedicated more funds from its Project Priorities budget to RFMF, and together with AWS also providing additional funds, this allowed us to open a new full-time Maintainer in Residence (MiR) position to support the Cargo team. We would like to thank the Rust Leadership Council, AWS, and also the Rust Foundation for providing us with this opportunity! If you would like to help us hire more maintainers to improve Rust, consider donating to RFMF.

This post explains why we chose to support the Cargo team specifically, and introduces Scott Schafer, the new Cargo Maintainer in Residence.

Why Cargo?

The new MiR full-time position is dedicated to helping with the maintenance of Cargo, our build system and package manager. The Cargo project is deeply involved in many new Rust features, improvements, and Project Goals. Combined with its cross-cutting nature, where it has to support many different use-cases and integrate with several other tools, it takes a lot of work just to keep up with its maintenance needs, let alone support so many feature requests and proposed changes.

Because of that, the Cargo team has sometimes struggled with meeting its maintenance demands. You might remember that for several years, it actually held a feature freeze, to reduce Cargo's internal tech debt, perform necessary refactorings, go through the issue and pull request backlog, and come up with scalable internal development and design processes, so that they could eventually go back to even thinking about adding new features.

Recently, some changes occurred within the team, which made it more difficult for them to meet their maintenance baseline. Some members of the team left, while others lost their dedicated funding for working on Cargo maintenance and had to scale down their involvement. The Funding team thus considered it very important to support this team, given that we had an opportunity to do so. And thus we decided to hire a full-time maintainer to work on Cargo for (at least) the next 12 months.

Even though we know that a single full-time maintainer will not completely solve the maintenance struggles of the Cargo team, we hope that it will improve the situation, and provide a bit of a relief for the team.

Introducing Scott Schafer

We are very happy to welcome Scott Schafer (@muscraft) into the Maintainer in Residence role! Scott has joined the Cargo team three years ago, and apart from working on Cargo, he is also the lead of the Rust Docker team, which prepares official Docker images for every Rust version.

Apart from working on general maintenance of Cargo, Scott has implemented Cargo's Workspace inheritance feature, and has also spearheaded a complex multi-year effort to switch the rendering of diagnostics in the Rust compiler to use the annotate-snippets crate. This effort has been completed in the Rust 1.93.0 release. Thanks to it, the same diagnostics interface can now be shared between the compiler and Cargo (and also other tools), which amongst other things unblocked further development of the Cargo linting system, which has now been stabilized and will ship in the Rust 1.100.0 release.

Everyone we talked about was very excited about Scott becoming a Cargo Maintainer in Residence, and we share that feeling. We wish Scott all the best in his new role, and we are very happy that we can support his maintenance work.

Here is what Scott thinks about it:

I am incredibly excited to work on Cargo full-time! There have been so many things that I wish I could've worked on over the years, that I will now be able to get to. I hope that my efforts will bring Cargo into a more maintainable state.

Conclusion

We are incredibly happy that we keep getting more funds for the Rust Foundation Maintainers Fund, which allows us to support Rust Project contributors. The funding team will be working with the supported maintainers, and also the funders, to ensure that they are all happy with the arrangement, so that we can secure stable funding for Rust maintenance for years to come.

If you would like to help us support more Rust maintainers, consider donating to RFMF!

22 Sep 2026 12:00am GMT