Add switch command for changing active #Preview in a live session#104
Merged
obj-p merged 2 commits intocli-mcp-parityfrom Apr 15, 2026
Merged
Add switch command for changing active #Preview in a live session#104obj-p merged 2 commits intocli-mcp-parityfrom
obj-p merged 2 commits intocli-mcp-parityfrom
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Fifth PR in the CLI/MCP parity stack. \`previewsmcp switch <index>\` forwards to the daemon's \`preview_switch\` MCP tool — recompiles the session with a different #Preview block selected. @State is reset; traits (color scheme, dynamic type, locale, …) persist across the switch. Session targeting mirrors \`configure\` and \`snapshot\`: - \`--session <uuid>\` — explicit - \`--file <path>\` — resolve by source file - no flag — use the sole running session As with \`configure\`, switching a session that doesn't exist is an error (no ephemeral fallback — a switch only makes sense against a live session). Client-side validation rejects negative indices before the RPC round trip. Out-of-range positive indices surface the daemon's "No preview at index N" error. Tests (4): negative-index validation, no-session error path, happy- path round trip (snapshot preview 0, switch to 1, snapshot, assert different bytes), and out-of-range-index error. Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
The review of PR #104 flagged that textFromContent was now duplicated across SessionResolver, SnapshotCommand, ConfigureCommand, and SwitchCommand (4 files) — past the rule-of-three, worth extracting. Adds MCPContentHelpers.swift with an extension on [Tool.Content]: extension Array where Element == Tool.Content { func joinedText() -> String { ... } } Call sites become `response.content.joinedText()` instead of `textFromContent(response.content)`. Reads slightly better at the call site as a property-like accessor, matches the shape future commands (elements, touch, stop, simulators) will want. No behavior change — the four private helpers were byte-identical. All 35 daemon-touching tests still pass. Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
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Summary
Fifth PR in the CLI/MCP parity stack. Adds `previewsmcp switch ` — forwards to the daemon's existing `preview_switch` MCP tool to recompile the session with a different `#Preview` block selected.
Test plan
4 new tests in `SwitchCommandTests`:
Regression:
Stack
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