Miri can't find target triple in CI

nazar-pc · January 10, 2026, 6:52am

I'm getting the following error in GitHub Actions CI:

Run cargo -Zgitoxide -Zgit miri nextest run --target riscv64a23-unknown-linux-gnu --locked 
info: syncing channel updates for 'nightly-2026-01-01-x86_64-unknown-linux-gnu'
info: latest update on 2026-01-01, rust version 1.94.0-nightly (8d670b93d 2025-12-31)
info: downloading component 'cargo'
info: downloading component 'clippy'
info: downloading component 'miri'
info: downloading component 'rust-docs'
info: downloading component 'rust-src'
info: downloading component 'rust-std'
info: downloading component 'rustc'
info: downloading component 'rustfmt'
info: installing component 'cargo'
info: installing component 'clippy'
info: installing component 'miri'
info: installing component 'rust-docs'
info: installing component 'rust-src'
info: installing component 'rust-std'
info: installing component 'rustc'
info: installing component 'rustfmt'
Preparing a sysroot for Miri (target: riscv64a23-unknown-linux-gnu)... done
  error: unknown triple string: riscv64a23-unknown-linux-gnu
  ├─▶ triple not in builtin platforms and heuristic parsing failed
  ╰─▶ Unrecognized architecture: riscv64a23
   ╭────
 1 │ riscv64a23-unknown-linux-gnu
   · ──────────────┬─────────────
   ·               ╰── triple not in builtin platforms and heuristic parsing failed
   ╰────

My rust-toolchain.toml contains the following, as such I do not have explicit toolchain steps:

[toolchain]
channel = "nightly-2026-01-01"
components = ["miri", "rust-src"]
targets = []
profile = "default"

Even more confusingly, it works locally with the same exact version of rustup 1.28.2.

Any idea why would CI be any different? It seems like it is using some components from stable toolchain that do not know about that triple yet despite logs saying otherwise.

bjorn3 · January 10, 2026, 10:10am

The only references to that exact error message I can find are

github.com/guppy-rs/guppy

target-spec/src/errors.rs

984613f7d


      
          enum TripleParseErrorKind {
              Lexicon(cfg_expr::target_lexicon::ParseError),
              LexiconDisabled,
          }
          
          impl fmt::Display for TripleParseErrorKind {
              fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
                  match self {
                      Self::Lexicon(_) => write!(
                          f,
                          "triple not in builtin platforms and heuristic parsing failed"
                      ),
                      Self::LexiconDisabled => write!(
                          f,
                          "triple not in builtin platforms and heuristic parsing disabled"
                      ),
                  }
              }
          }
          
          impl error::Error for TripleParseErrorKind {

and

github.com/nextest-rs/nextest

integration-tests/tests/integration/snapshots/integration__rustc_vv_invalid_triple.snap

9c3fd6b46


      
          
          --- stderr ---
          error: the host platform could not be detected
          
          Caused by:
            parsing `rustc -vV` output failed, and detecting the build target failed as well
            - host platform error:
              unknown platform triple
                caused by:
                - unknown triple string: invalid-triple
                - triple not in builtin platforms and heuristic parsing failed
                - Unrecognized architecture: invalid
            - build target error:
              error parsing `rustc -vV` output
                caused by:
                - output from `rustc -vV` did not contain a `host: ` line; output:
                  ---
                  (__NEXTEST_FORCE_BUILD_TARGET set to "error", forcibly failing build target detection)
                  ---

Maybe something to do with the nextest version?

nazar-pc · January 12, 2026, 4:09pm

Indeed, I had slightly older version of nextest in CI, switching to the latest fixed it.
Thank you!

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Miri can't find target triple in CI

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