fix(ui): model/eval picker shows no list when CLI model discovery fails

[Copilot]

When listCopilotModels() returns [] or throws (CLI not found, changed --help format, or help written to stderr), availableModels stayed empty and the model picker rendered nothing — leaving users stuck in model-pick state with a blank screen.

Changes

• tui.tsx — always populate availableModels
  Fall back to PREFERRED_MODELS in both the empty-result and error cases, so the list always renders when entering model-pick state (affects both M eval-model and J judge-model pickers).

• copilot.ts — handle stderr and non-zero exits in listCopilotModels
  Some CLI builds write --help to stderr and/or exit non-zero. Now captures both streams, tries stdout first, falls back to stderr (including from thrown ExecFileException).

• extractModelChoices exported + unit tested
  Added 6 tests covering single-line, multi-line, missing choices:, empty string, and stderr-sourced help text.

// Before: error case silently left models empty, picker rendered nothing
.catch(() => {
  setAvailableModels([]);  // ← gated list never shows
});

// After: always have a usable list
.catch(() => {
  setAvailableModels(PREFERRED_MODELS);
});

Original prompt

Selection in TUI for model and eval is broken, there is no list shown

The user has attached the following file paths as relevant context:

• AGENTS.md

Created from VS Code.

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[Copilot]

Pull request overview

Fixes the TUI model/eval picker getting stuck with an empty (non-rendering) model list when Copilot CLI model discovery returns an empty list or fails, by adding safer fallbacks and improving Copilot CLI --help parsing.

Changes:

• Ensure the TUI always has a non-empty availableModels list by falling back to PREFERRED_MODELS on empty discovery results and on errors.
• Make listCopilotModels() resilient to CLIs that write help text to stderr and/or exit non-zero for --help.
• Export extractModelChoices() and add unit tests for multiple help-output formats and edge cases.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

File	Description
src/ui/tui.tsx	Adds fallback to PREFERRED_MODELS so the model picker always renders a list.
packages/core/src/services/copilot.ts	Captures/parses both stdout and stderr for --help, exports the parser helper.
src/services/tests/copilot.test.ts	Adds unit coverage for extractModelChoices() across common formats/edge cases.

[Copilot]

In listCopilotModels(), the catch currently swallows all execFileAsync failures and then returns [] if parsing yields no choices. That changes behavior for real execution failures (timeout, EACCES, broken binary, etc.): callers like eval --list-models will now report “No models detected” instead of surfacing the underlying error.

Consider only falling back to parsing stdout/stderr for expected non-zero --help exits, and if no models can be extracted, rethrow the original error (or throw a new error that includes the original failure) so genuine failures aren’t silently converted into an empty list.

Suggested change

	try {
	const result = await execFileAsync(cmd, args, { timeout: 5000 });
	stdout = result.stdout;
	stderr = result.stderr;
	} catch (err) {
	// Some CLIs exit with a non-zero code for --help; try to extract from stderr
	const e = err as { stderr?: string; stdout?: string };
	stdout = e.stdout ?? "";
	stderr = e.stderr ?? "";
	}
	const fromStdout = extractModelChoices(stdout);
	return fromStdout.length > 0 ? fromStdout : extractModelChoices(stderr);
	let execError: unknown = null;
	try {
	const result = await execFileAsync(cmd, args, { timeout: 5000 });
	stdout = result.stdout;
	stderr = result.stderr;
	} catch (err) {
	// Some CLIs exit with a non-zero code for --help; try to extract from stderr
	execError = err;
	const e = err as { stderr?: string; stdout?: string };
	stdout = e.stdout ?? "";
	stderr = e.stderr ?? "";
	}
	const fromStdout = extractModelChoices(stdout);
	if (fromStdout.length > 0) return fromStdout;
	const fromStderr = extractModelChoices(stderr);
	if (fromStderr.length > 0) return fromStderr;
	if (execError) {
	const e = execError as Error & { stderr?: string; stdout?: string };
	const details = e.stderr || e.stdout;
	const detailMsg = details ? `\nCopilot CLI output:\n${details}` : "";
	throw new Error(`Failed to list Copilot models: ${e.message}${detailMsg}`);
	}
	return [];