Summary of Changes

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This pull request enhances the robustness of shim detection within the application. Previously, shim identification could be flawed when the main binary was renamed by package managers, leading to incorrect argument parsing. The updated logic now directly verifies the executable's presence in the designated shims directory, ensuring that shimmed tools correctly receive their intended arguments without interference from the application's own CLI flags.

Highlights

• Improved Shim Detection: The method for detecting if a process is running as a shim has been updated to check if the executable's basename exists in the shims directory, rather than relying on the binary name's prefix.
• Fix for Binary Naming Conflicts: This change resolves an issue where package managers renaming the mise binary (e.g., mise-2026.3.7) caused shims to be incorrectly identified as mise itself, leading to misinterpretation of command-line arguments like -json.
• Code Refinement: The now-unused is_mise_binary() function has been removed, simplifying the codebase.

Greptile Summary

This PR fixes a shim-detection regression where package managers that name the mise binary mise-<version> (e.g. mise-2026.3.7) caused the binary to be incorrectly treated as a regular mise invocation because the old is_mise_binary() check matched the "mise-" prefix. The fix replaces that heuristic with a positive filesystem check: is_in_shims_dir() verifies that a file matching argv[0]'s basename actually exists in the configured shims directory, which is both more precise and more robust.

Key changes:

• src/shims.rs: New is_in_shims_dir() function joins dirs::SHIMS with MISE_BIN_NAME and checks is_symlink() || exists() — the is_symlink() arm correctly handles broken shim symlinks that .exists() would miss.
• src/env.rs: IS_RUNNING_AS_SHIM now calls is_in_shims_dir() instead of !is_mise_binary(). The now-unused is_mise_binary() helper is removed cleanly.
• src/shims.rs — handle_shim(): Guard updated to *env::MISE_TOOL_STUB || !*env::IS_RUNNING_AS_SHIM; the cfg!(test) early-return is handled inside the lazy, keeping test behaviour unchanged.
• e2e/cli/test_shims_args: Regression test that exercises the -json flag (collides with mise's -j/--jobs flag) to confirm shim args are passed through unaltered.

Confidence Score: 5/5

• Safe to merge — the fix is narrowly scoped, logically sound, and backed by a targeted regression test.
• The change is small (three files, ~30 lines net), the new positive filesystem check is strictly more correct than the old name-prefix heuristic, all existing shim e2e tests continue to pass, and a new regression test directly exercises the reported failure mode. No correctness, security, or platform-compatibility issues were identified.
• No files require special attention.

Important Files Changed

Flowchart

%%{init: {'theme': 'neutral'}}%%
flowchart TD
    A[Process starts with argv0] --> B{cfg test?}
    B -- yes --> C[IS_RUNNING_AS_SHIM = false]
    B -- no --> D{MISE_TOOL_STUB?}
    D -- yes --> E[IS_RUNNING_AS_SHIM = true]
    D -- no --> F[is_in_shims_dir]
    F --> G{shims dir contains bin_name?}
    G -- yes --> H[IS_RUNNING_AS_SHIM = true]
    G -- no --> I[IS_RUNNING_AS_SHIM = false]

    C --> J[handle_shim]
    I --> J
    E --> J
    H --> J

    J --> K{MISE_TOOL_STUB OR NOT IS_RUNNING_AS_SHIM?}
    K -- yes --> L[Return early - direct mise or tool-stub path]
    K -- no --> M[Exec as shim - resolve tool binary and exec]

_{Last reviewed commit: "fix(shim): skip shim..."}

Hyperfine Performance

mise x -- echo

mise env

mise hook-env

mise ls

xtasks/test/perf