jackwener/OpenCLI · error · ArgumentError

Cannot switch to ${wantModel} model inside an existing conve

Error message

Cannot switch to ${wantModel} model inside an existing conversation.

What it means

The `claude ask` command throws this ArgumentError when the user explicitly passes --model while the browser session is inside an existing conversation (URL contains /chat/). The Claude UI only exposes the model selector on the new-chat page, so switching models mid-conversation is impossible via the automation. The error carries a hint to re-run with --new.

Source

Thrown at clis/claude/ask.js:80

                }
            }
        }

        // ensureClaudeComposer reads composer presence directly via getPageState,
        // so the previous standalone 2 s settle is redundant.
        await withRetry(() => ensureClaudeComposer(page, 'Claude ask requires a visible composer on the current page.'));

        // Model selector is only available on the new-chat page, not inside
        // an existing conversation. Also avoid changing the user's current
        // UI selection unless --model was explicitly passed.
        const currentUrl = await page.evaluate('window.location.href') || '';
        const inConversation = currentUrl.includes('/chat/');
        const modelExplicit = kwargs.__opencliOptionSources?.model === 'cli';

        const wantModel = kwargs.model || 'sonnet';
        if (modelExplicit) {
            if (inConversation) {
                throw new ArgumentError(
                    `Cannot switch to ${wantModel} model inside an existing conversation.`,
                    'Re-run with --new to start a fresh chat before selecting a model.',
                );
            }

            const modelResult = await withRetry(() => selectModel(page, wantModel));
            if (!modelResult?.ok) {
                if (modelResult?.upgrade) {
                    throw new ArgumentError(
                        `${wantModel} model requires a paid Claude plan.`,
                        'Pick --model sonnet or --model haiku, or upgrade your account.',
                    );
                }
                throw new CommandExecutionError(`Could not switch to ${wantModel} model`);
            }
            // Post-toggle settle dropped — the next CDP eval (setAdaptiveThinking) gives
            // React enough time to flush aria-checked updates between rountrips.
        }

View on GitHub (pinned to 49907e53dc)

Solutions

Re-run with --new to start a fresh chat before selecting a model.
Omit --model to keep the conversation's current model selection.
Navigate to a new chat (claude.ai/new) before invoking ask with --model.

Example fix

// before
opencli claude ask "explain" --model opus
// after
opencli claude ask "explain" --model opus --new

Defensive patterns

Strategy: validation

Validate before calling

// Start a new chat whenever --model is used
const url = await page.evaluate('window.location.href') || '';
if (opts.model && url.includes('/chat/')) opts.new = true;

Try / catch

try {
  await opencli.claude.ask(prompt, { model: 'opus' });
} catch (e) {
  if (/inside an existing conversation/.test(e.message)) {
    await opencli.claude.ask(prompt, { model: 'opus', new: true });
  } else throw e;
}

Prevention

Always pair --model with --new in scripts.
Omit --model when continuing existing conversations.
Track whether your session will resume a prior chat before passing --model.

When it happens

Trigger: Running `opencli claude ask ... --model opus` when the persistent session has resumed an existing conversation (currentUrl includes '/chat/') and --new was not passed, so the model selector cannot be clicked.

Common situations: Reusing a persistent session that automatically resumes the last chat; scripted calls that always pass --model but rely on session resumption; running the command a second time in a row without --new.

Understand the failure class

Background: "Unknown argument", "Invalid value", and "must be one of": invalid CLI argument errors explained — this error's family across 35 libraries.

Related errors

AI-assisted analysis of jackwener/OpenCLI@49907e53dc (2026-08-29). Data as JSON: /api/errors/8fc2dc9e6ca900a2. Report an issue: GitHub.