Shim should auto-install missing requested version when another version is already installed

[SanderKnape]

What I'm doing

• I manage Terraform with mise (e.g. in a project mise.toml: terraform = "1.14.4").
• terraform version correctly show 1.14.4, installed through mise
• I update the project config to request 1.14.5: terraform = "1.14.5".
• I run terraform version

What I expect

• Mise installs the missing 1.14.5 and then runs that version (or at least installs it so the next run uses it).

What actually happens

• Mise reports that the version is missing, but does not install it
• mise ls shows 1.14.4 is installed, and that 1.14.5 is missing

What does work

• mise exec -- terraform version installs 1.14.5 and runs it as expected.
• mise hook-not-found -v terraform (simulating command-not-found) installs 1.14.5.
• So the gap is specific to running terraform directly

Request

Can mise install the missing terraform version when directly calling terraform?

That would align the behavior with:

• mise exec / mise run, which already install missing versions from config, and
• The command-not-found handler, which can install missing versions when at least one version of the tool exists.

mise doctor output

version: 2026.2.19 macos-arm64 (2026-02-22)
activated: yes
shims_on_path: no
self_update_available: no

build_info:
  Target: aarch64-apple-darwin
  Features: DEFAULT, NATIVE_TLS, SELF_UPDATE
  Built: Sun, 22 Feb 2026 17:11:13 +0000
  Rust Version: rustc 1.93.1 (01f6ddf75 2026-02-11) (Homebrew)
  Profile: release

shell:
  /bin/zsh
  zsh 5.9 (arm64-apple-darwin25.0)

aqua:
  baked in registry tools: 2231

dirs:
  cache: ~/Library/Caches/mise
  config: ~/.config/mise
  data: ~/.local/share/mise
  shims: ~/.local/share/mise/shims
  state: ~/.local/state/mise

config_files:
  ~/Projects/mise/mise.toml

ignored_config_files: (none)

backends:
  aqua
  asdf
  cargo
  conda
  core
  dotnet
  forgejo
  gem
  github
  gitlab
  go
  npm
  pipx
  spm
  http
  s3
  ubi
  vfox

plugins:

toolset:
  aqua:hashicorp/terraform@1.14.5  (missing)

path:
  ~/Downloads/google-cloud-sdk/bin
  ~/.goenv/shims
  ~/.goenv/bin
  /opt/homebrew/bin
  /Library/Frameworks/Python.framework/Versions/3.13/bin
  /usr/local/bin
  /System/Cryptexes/App/usr/bin
  /usr/bin
  /bin
  /usr/sbin
  /sbin
  /var/run/com.apple.security.cryptexd/codex.system/bootstrap/usr/local/bin
  /var/run/com.apple.security.cryptexd/codex.system/bootstrap/usr/bin
  /var/run/com.apple.security.cryptexd/codex.system/bootstrap/usr/appleinternal/bin
  /opt/pmk/env/global/bin
  /usr/local/share/dotnet
  ~/.dotnet/tools
  /opt/homebrew/bin
  /Applications/iTerm.app/Contents/Resources/utilities

env_vars:
  MISE_SHELL=zsh

settings:

1 problem found:

1. tool aqua:hashicorp/terraform@1.14.5 is not installed, install with `mise install`

mise WARN  missing: terraform@1.14.5

[jdx]

This is an intentional design decision — auto-installing tools during shim execution or the hook-env prompt hook would add unpredictable latency to shell prompts and command invocations. A cd into a project directory shouldn't silently block while downloading and installing tools.

That said, the existing not_found_auto_install setting (enabled by default) already handles most of this. When you run terraform and the configured version isn't installed, the shell's command_not_found_handler fires, which calls mise hook-not-found, installs the missing version, and re-runs the command. There's one extra round-trip compared to a fully proactive approach, but it only happens on the first invocation after a version change.

If you want fully proactive "install on cd" behavior, you can achieve this with a mise hook — for example an enter hook that runs mise install.

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This reply was AI-generated.

[SanderKnape]

My suggestion isn't about when entering a directory; it's when running a tool (e.g. terraform) that I'm managing through mise of which I just changed the version in the mise.toml file.

When you run terraform and the configured version isn't installed, the shell's command_not_found_handler fires, which calls mise hook-not-found, installs the missing version, and re-runs the command.

This isn't the case in my experience - I get a warning that the version isn't installed, but mise doesn't install the missing version.

[jdx]

Despite the title mentioning shims, your mise doctor output shows activated: yes and shims_on_path: no, so you're using mise activate, not shims.

If you were using shims, they would auto-install the missing version for you (via the not_found_auto_install setting, enabled by default).

With mise activate, the command_not_found_handler should actually handle this case too — when hook-env sees 1.14.5 isn't installed, it won't put terraform on PATH, so the next time you run terraform it should trigger the not-found handler and auto-install it.

My guess is you have another terraform on your system PATH (maybe from homebrew or the Google Cloud SDK, both of which are in your PATH). That would resolve first and prevent the not-found handler from ever firing. Can you check what which terraform returns after changing the version in your config?

Note that doing much more here in the non-shim approach is probably not possible — with mise activate, we only control PATH via the prompt hook and rely on the shell's command-not-found handler. We can't intercept a command that the shell already resolves to a binary on PATH. Shims would give you the behavior you're looking for since they intercept every invocation.

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This reply was AI-generated.