Status: Decided Date: 2026-03-23 Relates to: ADR-T-001 (root crate conventions)
Rust edition 2024 (stabilised in Rust 1.85) introduces language and
library changes that affect compilation. Although the workspace still
targets edition = "2021", several transitive dependencies have
already published releases that set edition = "2024" in their own
Cargo.toml. Those crates require rustc >= 1.85 to compile.
This creates a conflict: keeping the workspace on edition 2021 is desirable until all first-party code is migrated, but the latest versions of some dependencies can no longer build on the previous MSRV (1.80).
Even after downgrading every edition-2024 crate, the remaining dependency tree still requires at least rustc 1.83 due to non-edition MSRV bumps in transitive crates:
| Minimum rustc | Crates (examples) |
|---|---|
| 1.83 | async-compression, compression-codecs, crc, icu_*, pest* |
| 1.82 | axum-server, idna_adapter, indexmap, serde_with, yoke, zerovec |
| 1.81 | base64ct, derive_more, zerofrom |
Since 1.83 is the highest floor in that set, it becomes the new MSRV.
| Option | Strategy | Edition compat | Risk |
|---|---|---|---|
| A. Pin deps, raise MSRV to 1.83 | Downgrade or pin every transitive dep that requires edition 2024; stay on edition 2021 | All deps build under 2021 | Pins will drift; must be actively maintained until the full migration |
| B. Jump straight to edition 2024 | Bump edition = "2024" workspace-wide, require rustc >= 1.85 |
Native | Large migration surface — all first-party code must pass 2024 lints in one step |
| C. Stay on current MSRV (1.80) | Pin even more aggressively, avoid the 1.81–1.83 crates too | All deps build under 2021 on 1.80 | Too many pins; some crates have no viable older version |
Option C was rejected because the transitive dependency floor at 1.83 cannot be avoided without forking crates. Option B is the end goal but premature — edition 2024 migration should be a separate, focused ADR. Option A buys time for that migration.
Option A — Pin or downgrade affected transitive dependencies so the entire dependency tree compiles under edition 2021 with a raised MSRV of 1.83.
| Setting / Crate | From | To | Reason |
|---|---|---|---|
rust-version |
1.80 | 1.83 | Highest MSRV required by transitive deps |
jsonwebtoken |
10 (with rust_crypto) |
9.3 | v10 pulls simple_asn1 0.6.4 -> time 0.3.47 (edition 2024) |
rand |
0 (resolved to 0.10) | 0.9 | rand 0.10 depends on rand_core 0.10 (edition 2024) |
The following crates were pinned to older versions to avoid edition-2024-only releases in the lock file:
| Crate | From | To | Chain |
|---|---|---|---|
time |
0.3.47 | 0.3.41 | time-core 0.1.8 -> edition 2024 |
time-core |
0.1.8 | 0.1.4 | edition 2024 |
time-macros |
0.2.27 | 0.2.22 | pulled by time |
deranged |
0.5.8 | 0.4.0 | pulled by time |
num-conv |
0.2.0 | 0.1.0 | pulled by time |
simple_asn1 |
0.6.4 | 0.6.3 | required time ^0.3.47 |
serde_with |
3.18.0 | 3.17.0 | required time ~0.3.47 |
serde_with_macros |
3.18.0 | 3.17.0 | pulled by serde_with |
darling |
0.23.0 | 0.21.3 | pulled by serde_with |
darling_core |
0.23.0 | 0.21.3 | pulled by darling |
darling_macro |
0.23.0 | 0.21.3 | pulled by darling |
clap |
4.6.0 | 4.5.61 | edition 2024 |
clap_builder |
4.6.0 | 4.5.61 | pulled by clap |
clap_derive |
4.6.0 | 4.5.61 | pulled by clap |
clap_lex |
1.1.0 | 1.0.1 | edition 2024 |
globset |
0.4.18 | 0.4.15 | edition 2024 |
ignore |
0.4.25 | 0.4.22 | required globset ^0.4.18 |
home |
0.5.12 | 0.5.11 | edition 2024 |
image |
0.25.10 | 0.25.6 | removed moxcms/pxfm (edition 2024) |
png |
0.18.1 | 0.17.16 | pulled by image |
jsonwebtoken |
10.3.0 | 9.3.1 | direct change (see above) |
quickcheck |
1.1.0 | 1.0.3 | required rand ^0.10 |
env_logger |
0.11.9 | 0.8.4 | pulled by quickcheck |
uuid |
1.22.0 | 1.20.0 | getrandom 0.4 edition 2024 |
base64ct |
1.8.3 | 1.7.3 | edition 2024 |
psm |
0.1.30 | 0.1.24 | removed ar_archive_writer (edition 2024) |
tera |
1.20.1 | 1.20.0 | edition 2024 |
No longer in the dependency tree after the downgrades:
rand 0.10,rand_core 0.10,chacha20,cpufeatures— pulled byrand 0.10getrandom 0.4— edition 2024moxcms,pxfm— pulled byimage 0.25.10ar_archive_writer— pulled bypsm 0.1.30
rand 0.9 renames rand::RngExt back to rand::Rng. All call
sites were updated accordingly (no behavioural change).
- The workspace version is bumped to 3.1.0-develop.
- The workspace MSRV is now 1.83.
- All dependency versions are frozen in
Cargo.lockto editions <= 2021. - A future ADR will cover the actual migration to
edition = "2024", at which point these pins can be lifted and crates updated to their latest versions. - A new MSRV CI job reads
rust-versionfromCargo.tomland verifies the workspace builds and tests pass on that exact toolchain.