runtime-host project add with a regular file inside a Git repository shuts down the Host #5220

What happened

maka runtime-host project add does not validate that the supplied path is a directory. Passing a regular file inside a Git repository returns Project catalog mutation outcome is unknown and makes the Runtime Host exit with code 1. The next project list cannot connect to the Host. A mistyped project path should be rejected as invalid input while the Host stays available.

There is a second branch of the same missing validation: a regular file outside any Git repository is successfully added as an unavailable project (available: false, exit code 0), instead of being rejected.

How to reproduce

1. Build main (npm ci, npm run build). Create an isolated directory containing a Git repository, an ordinary file, and a separate Host state directory:

   repro_dir="$(mktemp -d)"
   git init --quiet "$repro_dir/repo"
   touch "$repro_dir/repo/README.md"
   mkdir "$repro_dir/state"

2. Start a Host and wait for the runtime_host_ready JSON event (keep this terminal open; substitute the printed absolute path for $repro_dir in the second terminal):

   node packages/cli/dist/cli.js runtime-host serve \
     --root "$repro_dir/state" --no-project-roots --json

3. In a second terminal, first confirm that the Host is available, then add the file, then query again:

   node packages/cli/dist/cli.js runtime-host project list --root "$repro_dir/state"
   node packages/cli/dist/cli.js runtime-host project add "$repro_dir/repo/README.md" --root "$repro_dir/state"
   node packages/cli/dist/cli.js runtime-host project list --root "$repro_dir/state"

4. The first query returns []. The add command exits 1 with Project catalog mutation outcome is unknown; the Host exits 1; the final query exits 1 with Runtime Host service is not available (unavailable).

Reproduced in three isolated Host instances. For the non-Git variant, use a plain directory instead of git init: the add command returns a project with name README.md, available: false, and exit code 0.

Environment

• Maka: built locally from main, 05164f5359467a9d00ea144395ab0b9f1f74750c (package version 0.2.0)
• OS: macOS 15.6 (24G84), arm64
• Surface: CLI / Runtime Host
• Node.js: v24.19.0
• Tested: September 12, 2026

Logs, screenshots, or additional context

Before:
  project list: exit 0, []
Trigger:
  RuntimeHostOperationError: Project catalog mutation outcome is unknown
  project add: exit 1
Host process:
  exit code 1, no signal
After:
  Error: Runtime Host service is not available (unavailable)
  project list: exit 1

The resolver calls realpath() but does not check stat().isDirectory() before repository discovery (packages/storage/src/project-catalog.ts, resolveProjectLocation). Within a Git repository it executes git -C <regular-file> rev-parse ...; this fails with Git's numeric exit status, which is not one of the filesystem codes recognized by isInvalidPathError. The coordinator consequently calls requestDrain() and reports commit_outcome_unknown (packages/runtime-host/src/server/project-catalog-coordinator.ts:143-149). Outside Git, the same file passes through as a folder project.

Related but different: #4806 concerns a valid directory below an invalid ancestor .git marker. This reproduction uses a valid Git repository and selects a regular file; the missing path-type check is also visible without Git.

Discovered and reproduced by Codex during user-authorized exploratory testing of a locally built main checkout. All fixtures and Host roots were isolated from the user's existing Maka data. The testing launcher only selected a separate profile name; the CLI commands and Host implementation were unchanged.