# Bug Report: fix-harness-command-template

Self-bug-hunt against the implementation. No adversarial pass yet (separate phase).

## Bugs found

None blocking. The fix is small (a few lines in `_invoke_harness` plus test scaffolding updates). Observations below are non-blocking.

## Observations (non-blocking)

### O1 — `_resolve_prompt` return value can be an empty string
If `prompt_ref` is `None` or `""`, `_resolve_prompt` returns `""` (line `return prompt_ref or ""`). Then `Path(resolved_prompt).read_text()` raises `OSError` and `prompt_content` becomes `""`. The default command becomes `["opencode", "run", "--dir", "{cwd}", ""]` — a single empty-string positional. Harmless (opencode treats empty message as no prompt); behavior matches v1's `"--prompt-file", ""` which was also empty.

### O2 — Tested harness commands don't exercise `--cwd` absent case for cross-platform
Tests assume `--dir` works on this machine (darwin). On Windows, `opencode run --dir <path>` should work the same way, but no Windows CI run is exercised here. Out of scope — the path-separator handling is opencode's job, not the runner's.

### O3 — `Path(resolved_prompt).read_text()` uses default encoding
No `encoding="utf-8"` argument. On Windows the default encoding is cp1252; a prompt file with non-ASCII content could mis-decode. Low-impact; the rest of the framework already uses default encoding in similar reads (e.g. `_state`, `_read_state_loop`). Documented as a follow-up if it ever bites.

### O4 — Test stub content uses a trailing newline
`_make_loop` writes `f"prompt: {prompt_ref}\n"` — the trailing `\n` is preserved in `{prompt_content}`. Tests assert with `.rstrip()` to handle it. In real usage, prompt files routinely end with a newline and the harness treats it as whitespace. Not a bug; just a note for future test maintainability.

### O5 — No smoke test against real `opencode run`
The SPEC noted an optional `@pytest.mark.skipif(not shutil.which("opencode"))` smoke test asserting `--dir` exists in `opencode run --help`. Not added in this task to keep the change focused. The 7 new unit tests cover the construction of the default command directly, which is the primary surface.

## Verdict

PASS — proceed to adversarial_bug_find.