Output budgets

A noisy command can dump thousands of lines. That hurts twice: it costs the agent context window, and the volume itself degrades the agent’s reasoning. Output budgets shape a command’s output before it reaches the model.

Pass budget to session_exec, or output_budget to session_create for a session default:

// keep only the last 200 lines of a noisy build
{ "session_id": "1_local", "command": "npm run build",
  "budget": { "keep": { "mode": "tail", "n": 200 } } }

// grep a 50k-line log for errors, with 2 lines of context around each
{ "session_id": "1_local", "command": "cat big.log",
  "budget": { "grep": { "pattern": "error|fail", "context": 2 } } }

Keep modes are tail, head, and head_tail; grep is a separate filter; both honor a max_chars cap.

Shaping is line-based, applied client-side, and runs after secret redaction. It never changes the exit code or any side effect of the command, only what text comes back. When a budget is applied, the result carries a budget report so the agent knows the output was shaped:

"budget": {
  "stdout": { "mode": "tail", "lines_total": 4123, "lines_kept": 200 },
  "stderr": { "mode": "tail", "lines_total": 12, "lines_kept": 12 }
}

Use budgets liberally on commands you expect to be loud (builds, installs, big log reads); the agent keeps the signal without the noise.