Devin

Install

nah hook devin install

To deny explicit evaluation failures and bounded analysis refusals, install with --fail-closed. Ordinary unknown or opaque calls still delegate. --fail-open restores the default; flagless reinstall preserves a recognized mode. The guarantee requires the loaded nah process to return a response; missing hooks/binaries, runtime timeout, process termination, bypass, and broken output pipes remain outside it.

Restart Devin and inspect /hooks. Remove only nah's handlers with:

nah hook devin uninstall

The installer updates standard ~/.config/devin/config.json, preserves unrelated configuration, and replaces stale nah 0.x handlers.

Behavior

The local harness shared by Devin CLI and Devin Local in Devin Desktop sends exec, read, write, edit, grep, and glob calls through nah. Definite findings block. Malformed and every other unblocked call delegate to Devin's permission flow.

Boundaries

This does not cover cloud Devin, handoff sessions, legacy Cascade, non-agent Desktop features, third-party ACP agents, or direct human actions. Alternate configuration files supplied with --config avoid the standard hook.

Devin's Bypass mode (/yolo) auto-approves normal tools, while Autonomous mode auto-approves shell and fetch tools. Devin does not document either mode as disabling PreToolUse, so a loaded nah hook can still block; delegated calls may execute without a prompt. Exit 2 blocks, while other nonzero hook exits are logged and continue. The nah adapter deliberately uses exit 2 when its own guard blocks. Under the default mode, evaluation failure exits 0 with fixed diagnostic feedback.

Devin imports Claude hooks by default, so installing both integrations can check a call twice. The adapter uses DEVIN_PROJECT_DIR; a persistent shell's changed cwd is not present in the documented payload. Devin also discovers project hooks from .devin/hooks.v1.json, .devin/config.json, .devin/config.local.json, .claude/settings.json, and .claude/settings.local.json from the working directory through the repository root. Those hooks can run alongside nah. Other hook sources, loading, future tool shapes, and runtime failures remain outside nah.

While active, this adapter blocks visible lifecycle commands, mutations to its standard user config, and child launches using --config to avoid it. Bypass and Autonomous permission modes do not disable hooks and are not self-protection findings. The agent is told not to retry protected changes; an operator can use nah nap from another terminal.

This integration is best effort: runtime APIs and hook behavior can change. After upgrades, verify the latest official upstream documentation linked below, inspect the loaded hook, and test it before relying on nah. See Devin's hook documentation, permission modes, and Devin Local documentation.