[AAASM-4831] 🐛 (python): Harden langchain handler singleton + haystack positional-arg passthrough

[Chisanan232]

Description

Two non-exploitable hardening fixes (LOW cluster AAASM-4831) in the python-sdk framework adapters:

1. langchain (adapters/langchain/runtime.py) — auto_inject_callback_handler kept the module-level singleton for any second call regardless of the interceptor, so a differently-postured re-init without a prior shutdown() would silently reuse the stale handler. It now returns the existing handler only when the interceptor is identical (the matching-params re-init path, unchanged), and warns + clear-and-replaces on a mismatch. init_assembly blocks this path today, so this is defensive hardening for future refactors.

2. haystack (adapters/haystack/patch.py) — patched_invoke accepted **kwargs only, so a positional Tool.invoke(x) raised TypeError (crash, not a bypass). It now accepts *args and forwards them to the wrapped invoke, so a positional call is governed and forwarded. Haystack's ToolInvoker calls invoke(**final_args) today, so this is defensive but matches the wrapped signature.

Type of Change

• 🔧 Bug fix

Breaking Changes

• No

Related Issues

• Related JIRA ticket: AAASM-4831

Testing

• Unit tests added/updated

Added regression tests: (1) re-injecting the langchain handler with a different interceptor warns (RuntimeWarning) and replaces rather than silently keeping the stale one; existing idempotency test updated to use the same interceptor for the matching path. (2) haystack patched_invoke handles a positional arg without TypeError and still governs (allow forwards, deny blocks the wrapped function).

Validation: pytest test/ -k "langchain or haystack" → 183 passed, 3 skipped (haystack real-package tests, not installed); ruff check + ruff format clean; mypy agent_assembly clean on changed files.

Checklist

• Code follows project style guidelines
• Self-review completed
• Comments added for complex logic
• All tests passing

🤖 Generated with Claude Code

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
100.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

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[Chisanan232]

🤖 Claude Code — PR review

Scope (AAASM-4831, LOW): ✅ langchain callback handler warns+replaces on a differing-config re-init (was stale reuse); haystack patched_invoke accepts *args (positional call was a TypeError).

1. CI — ✅ green (19); 183 pass. 2. Scope — ✅ 2 adapter files + tests. 3. Side effects — none; matching-params path unchanged. 4. FE — n/a.
   Verdict: ready to merge pending Pioneer approval.