After each turn that changed code, Haiku 5.5 reads the diff in the background and pins one line under your prompt: ✓ when nothing broke, ⚠ when something did. Details are one click away, and one more click hands them to Claude. About a tenth of a cent a review.
Coding agents are fast and confident, and the mistakes that slip through are the quiet ones: a guard deleted while "simplifying", an error swallowed, a function that now does something other than what you asked.
Every successful Edit, Write and NotebookEdit in the turn is recorded, subagents' too, as the diff Claude Code itself produced, with line numbers.
When the turn ends, the diff and your request go to Haiku 5.5. It runs in the background; the next turn doesn't wait.
The verdict is pinned under the prompt. A warning opens a band with Details, Ask Claude to fix and Dismiss.
The reviewer answers one question: did this change break something? It is told never to invent a problem, and a reply it can't parse never counts as a warning.
Haiku 5.5 costs $0.10 per million input tokens and $0.50 per million output, about 40× less than Opus. The session's running total is in the line itself.
| Turn | Diff sent | Review |
|---|---|---|
| A one-function fix | ~2K tokens | ~$0.0003 |
| A typical feature turn | ~6K tokens | ~$0.0008 |
| A big refactor (cut at 24K characters) | ~8K tokens | ~$0.001 |
Want a deeper pass? /second-opinion model sonnet reviews with Sonnet 5.5 at about twenty times the price.
/second-opinionEvery finding with file and line, the model and what it cost.
/second-opinion fix"Check whether it is real; fix it if so, say why not otherwise."
/second-opinion off · onRemembered across sessions.
/second-opinion modelCheap and quick, or careful.
privacyThe diff goes to Claude through your Claude Code session's own connection. Nothing else leaves the machine.
no setupIt runs inside Claude Code. No API key, no Python, no config file.
claude plugin marketplace add egorfedorov/second-opinion claude plugin install second-opinion@second-opinion
# after a turn that changed code
/second-opinion
Needs a Claude Code version with plugin mods; recent versions have them.