Fix CI

Author: wallstop

.github/workflows/ci-rust.yml

@@ -288,19 +288,30 @@ jobs:
           toolchain: nightly
           components: miri
 
-      - name: Cache cargo registry and build
+      - name: Cache cargo registry (no target for Miri)
         uses: actions/cache@v5
         with:
           path: |
             ~/.cargo/registry
             ~/.cargo/git
-            target
+          # NOTE: do not cache `target/` for Miri.
+          # `cargo miri` writes toolchain-specific wrapper artifacts under `target/miri/`.
+          # Caching/restoring those across changing nightly toolchains can break builds with:
+          #   "contains outdated or invalid JSON; try `cargo clean`".
           # Include matrix.name in cache key for job-specific caching
           key: miri-${{ matrix.os }}-${{ matrix.name }}-cargo-${{ hashFiles('**/Cargo.lock') }}
           restore-keys: |
             miri-${{ matrix.os }}-${{ matrix.name }}-cargo-
             miri-${{ matrix.os }}-cargo-
 
+      - name: Miri toolchain diagnostics
+        shell: bash
+        run: |
+          set -euo pipefail
+          rustc -Vv
+          cargo -Vv
+          cargo miri --version
+
       - name: Setup Miri
         run: cargo miri setup
 

.llm/skills/miri-verification.md

@@ -336,13 +336,16 @@ miri:
         toolchain: nightly
         components: miri
 
-    - name: Cache cargo registry and build
-      uses: actions/cache@v4
+    - name: Cache cargo registry (avoid target/ for Miri)
+      uses: actions/cache@v5
       with:
         path: |
           ~/.cargo/registry
           ~/.cargo/git
-          target
+        # NOTE: Avoid caching `target/` for Miri.
+        # `cargo miri` writes toolchain-specific wrapper artifacts under `target/miri/`.
+        # Restoring those across changing nightlies can fail with:
+        #   "contains outdated or invalid JSON; try `cargo clean`".
         key: miri-${{ matrix.os }}-cargo-${{ hashFiles('**/Cargo.lock') }}
         restore-keys: |
           miri-${{ matrix.os }}-cargo-