Opus 4.8 now powers Amp's smart
mode, replacing Opus 4.7.
It is a better coding agent than Opus 4.7: more faithful to the prompt, tighter in the changes it makes, and better at checking its own work. In our internal evals it solved 62% of tasks, up from 4.7's 52%.
Opus 4.7 was already strong on hard, multi-file work, and Opus 4.8 keeps that. What changes is how it gets there: with fewer wasted steps and more self-checking.
The clearest difference is restraint and verification.
Opus 4.7 can sometimes over-engineer, reaching for a more elaborate solution than the task needs. It also verifies its own work less, occasionally moving on even when a command's output is already warning that something is off.
Opus 4.8 makes a more focused change that solves the specific intended task, then checks itself. It leans on a tighter write→test loop, often spinning up a quick script, test, or skill to confirm the change works before proceeding. In our evals it ran tests and code 15% more per task than 4.7.
That restraint is easiest to see on hard tasks. On everyday work the two make a similar number of tool calls. The harder a task gets, the tighter 4.8 stays, just where 4.7 tends to run long and fail more often.
Opus 4.8 is noticeably better at using its tools and sub-agents without being told to.
When a task needs outside context, it actually calls librarian
instead of inferring a library's behavior from the local code. Across our eval it reached for it 14 times, versus once for Opus 4.7. It also reaches for a repo's skills more often to verify its work, for example by driving the browser or the CLI, rather than just assuming the change worked.
When it edits, it leans on edit_file
for surgical, in-place changes rather than rewriting whole files with create_file
. In our evals 79% of its file edits go through edit_file
, up from 63% on Opus 4.7.
We dropped the Read
tool from smart
.
Opus 4.8 is good enough at reading files straight from the shell with cat
, rg
, sed
, and nl
. It parallelizes those reads when it needs several files at once.
Opus 4.8 has a fast mode at roughly 2.5× the speed. It now costs 2× base tokens, down from 6× on 4.7—3× cheaper.
Toggle fast mode for a thread from the CLI command palette (Ctrl+O) → speed: use fast
.
Opus 4.8 stays close to what you ask, changes less to get there, and checks its own work. A few habits make it shine: