Summary

applyNodeConfig writes into options.hooks[event] without guaranteeing the hooks map is initialized. Any workflow that declares per-node hooks (e.g. archon-architect, archon-refactor-safely) crashes at runtime with:

```
TypeError: undefined is not an object (evaluating 'options.hooks[event] = matchers')
at applyNodeConfig (packages/providers/src/claude/provider.ts:394)
at sendQuery (packages/providers/src/claude/provider.ts:934)
```

The function explicitly acknowledges options.hooks may be undefined one line above (existingHooks typed as SDKHooksMap | undefined), so the fix is to materialize the object before the write loop runs.

Reproduction (pre-fix)

Run any workflow with per-node hooks against the Claude provider — the first AI node crashes in applyNodeConfig. Real-world impact: archon-architect dies on the analyze node; archon-refactor-safely fails identically.

Fix

if (Object.keys(builtHooks).length > 0) {
  const existingHooks = options.hooks as SDKHooksMap | undefined;
  options.hooks ??= {};   // ← added
  for (const [event, matchers] of Object.entries(builtHooks)) { ... }
}

Why this is safe

• Minimal: one line, landing after the existingHooks capture so the read semantics are preserved.
• Idempotent when options.hooks exists: ??= is a no-op; the merge-with-existing path runs identically.
• Fixes the crash path: when options.hooks is undefined, it becomes {}, then the loop populates it — exactly what the original code was trying to do.
• Downstream contract unchanged: existing tests already use optional chaining (args.options.hooks?.PostToolUse in provider.test.ts:1113), so callers already handle a potentially-absent hooks.

Alternatives considered

• Initializing options.hooks = {} at the top of applyNodeConfig — changes the contract when nodeConfig.hooks is absent (currently leaves options.hooks untouched).
• Refactoring the cast-based assignment pattern into typed narrowing — larger scope, better as a follow-up.

Test plan

• New regression test in provider.test.ts drives sendQuery with nodeConfig.hooks and asserts the SDK receives options.hooks populated. The test fails with the original TypeError on unpatched code (verified by stashing the fix and rerunning).
• Full suite — bun run test for packages/providers: 69 pass, 0 fail.
• bun run type-check — all 10 packages pass.
• bun run lint — clean.
• bun run format — no changes required.

Happy to adjust wording or expand tests — this surfaced while running archon-architect against an unrelated repo.

Summary by CodeRabbit

• Bug Fixes

  • Enhanced hook configuration initialization to ensure reliable setup and prevent potential undefined access errors when merging node-specific hooks with provider configurations.

• Tests

  • Added regression test validating that hook configurations are properly initialized and preserved during the merging of node-specific hooks with provider options, even when initial state is undefined.