fix: unwrap AppModuleResolver to find activator in self-healing

[samueljklee]

Summary

• Fix _invalidate_all_install_state() to correctly find the activator when the resolver is wrapped in an AppModuleResolver

Problem

The self-healing detection was working, but the actual fix (invalidating install state) was always failing silently with "No activator found" warning. This meant missing dependency issues like "tool-web module has a missing aiohttp dependency" would never self-heal.

Root Cause

At line 248-251 of session_runner.py, the resolver gets wrapped with AppModuleResolver, which stores the original BundleModuleResolver as self._bundle. However, _invalidate_all_install_state() was looking for _activator directly on the AppModuleResolver instead of unwrapping to get the BundleModuleResolver first.

Fix

Unwrap AppModuleResolver to get BundleModuleResolver before accessing _activator. This follows the same pattern already used in session_spawner.py.

Test plan

• Verify self-healing now works when dependency issues are detected
• Confirm the fix correctly handles both wrapped (AppModuleResolver) and direct (BundleModuleResolver) cases

🤖 Generated with Amplifier

[samueljklee]

PR Review: ✅ Approve

The Problem

The self-healing mechanism was detecting dependency issues correctly, but the actual fix (invalidating install state) was silently failing. The _invalidate_all_install_state() function couldn't find the activator because:

1. At lines 248-251, the BundleModuleResolver gets wrapped in an AppModuleResolver:

   prepared_bundle.resolver = AppModuleResolver(
       bundle_resolver=prepared_bundle.resolver,  # stored as self._bundle
       settings_resolver=fallback_resolver,
   )

2. The _activator lives on the BundleModuleResolver, but the code was looking for it directly on the AppModuleResolver wrapper.

The Fix

# Before:
activator = getattr(resolver, "_activator", None)

# After:
bundle_resolver = getattr(resolver, "_bundle", resolver)  # unwrap if wrapped
activator = getattr(bundle_resolver, "_activator", None)

The getattr(resolver, "_bundle", resolver) pattern elegantly handles both cases:

• If wrapped (AppModuleResolver): returns resolver._bundle (the BundleModuleResolver)
• If direct (BundleModuleResolver): returns resolver itself (no _bundle attribute)

Assessment

Aspect	Verdict
Root cause analysis	✅ Correct
Fix correctness	✅ Correct
Pattern consistency	✅ Follows existing pattern in session_spawner.py
Code change size	✅ Minimal (+4/-1)
Risk	✅ Low - handles both wrapped and direct cases

Ship it. The fix is correct, minimal, and follows established patterns in the codebase.

[colombod]

Is there a better way than accessing protected state in python, this is something easy to break since in foundation this could change even if we constrain to keeping the public surface locked. Maybe we review the proposed refactored change in foundation :microsoft/amplifier-foundation#41

[samueljklee]

Changes here have been brought into #71 . Closing this PR.