SecurityValidator hook fires PreToolUse:Read error: missing 'yaml' package in ~/.pai/

[virtualian]

Symptom

Every Read tool call in a Claude Code session emits this non-blocking warning:

PreToolUse:Read hook error
Failed with non-blocking status code: error:
Cannot find package 'yaml' from '/Users/ianmarr/.pai/hooks/SecurityValidator.hook.ts'

Status is non-blocking, so the Read still succeeds — but the warning fires on every Read across the entire session, polluting output and obscuring real errors.

Root cause

SecurityValidator.hook.ts imports the third-party yaml package:

// ~/.pai/hooks/SecurityValidator.hook.ts:66
import { parse as parseYaml } from 'yaml';

But there is no package.json or node_modules resolvable from ~/.pai/hooks/ upward:

$ ls /Users/ianmarr/.pai/package.json /Users/ianmarr/.pai/node_modules
ls: /Users/ianmarr/.pai/node_modules: No such file or directory
ls: /Users/ianmarr/.pai/package.json: No such file or directory

$ ls /Users/ianmarr/.pai/hooks/package.json /Users/ianmarr/.pai/hooks/node_modules
ls: /Users/ianmarr/.pai/hooks/node_modules: No such file or directory
ls: /Users/ianmarr/.pai/hooks/package.json: No such file or directory

Bun resolves npm imports starting from the source file's directory and walking up. With no node_modules containing yaml anywhere on that path, the hook crashes during import.

Scope

Likely affects more than just SecurityValidator.hook.ts. The same pattern exists in Releases/v4.0.3+/.claude/hooks/SecurityValidator.hook.ts:66, so this is not runtime-only drift — fresh installs of v4.0.3+ should hit the same issue unless the install path arranges yaml to be resolvable. Worth auditing every hook in ~/.pai/hooks/*.ts for third-party imports (17 hooks present) to scope the full failure surface.

Reproduction

1. Have PAI v4.0.3+ installed with hooks at ~/.pai/hooks/.
2. Start any Claude Code session.
3. Trigger any tool that fires PreToolUse:Read (e.g. read any file).
4. Observe Cannot find package 'yaml' from '/Users/ianmarr/.pai/hooks/SecurityValidator.hook.ts' warning.

Suggested directions (not committing to one)

• (a) Add package.json + bun-install at runtime root. Place a minimal ~/.pai/package.json declaring yaml (and any other hook deps), run bun install during install, and ensure ~/.pai/node_modules is populated. Most direct fix.
• (b) Resolve from ~/.claude/. If ~/.claude/ already has node_modules with yaml, configure Bun resolution roots so ~/.pai/hooks/*.ts can import from ~/.claude/node_modules. Avoids duplicating deps.
• (c) Bundle deps into the hook. bun build --bundle the hook so all imports are inlined. No runtime resolution needed but loses easy patching.
• (d) Eliminate the dep. yaml is only used to parse patterns.yaml (security pattern definitions). Could swap for a JSON file or hand-written parser if the format is small enough. Reduces dependency surface.

Investigation context

• Hook mtime: 7 Apr 20:31 — predates current PAI work; not introduced by recent PRs.
• Same import { parse as parseYaml } from 'yaml'; line is present in repo at Releases/v4.0.3+/.claude/hooks/SecurityValidator.hook.ts:66 — so the fix needs to land in the shipped artefact, not just the runtime.
• Discovered while applying Implement PAI user-choice Q&A contract (closes #148) #154 to live runtime; unrelated to that work, but visible because every Read in the session triggered the warning.