PR #35651: fix(langchain): normalize custom detector output to prevent KeyError in hash/mask strategies

• Repository: langchain-ai/langchain
• Author: giulio-leone
• State: closed | merged: True
• Link: https://github.com/langchain-ai/langchain/pull/35651

Description (problem / solution / changelog)

Summary

Fixes #35647 — PIIMiddleware raises KeyError: 'value' when using a custom callable detector with hash or mask strategies.

Root Cause

Custom callable detectors may return dicts with "text" instead of "value" (as shown in the documentation examples):

def detector(content: str) -> list[dict]:
    return [{"text": "matched", "start": 0, "end": 7}]

Built-in and regex detectors produce proper PIIMatch objects with type, value, start, end. But custom callables are returned as-is from resolve_detector(). When _apply_hash_strategy or _apply_mask_strategy access match["value"], they fail with KeyError.

The redact and block strategies only use match["type"], match["start"], and match["end"] — which is why they work.

Fix

In resolve_detector(), wrap custom callable detectors in a normalizing function that:

• Maps "text" → "value" if "value" is missing
• Adds the pii_type as "type" if missing
• Produces proper PIIMatch objects for all downstream strategies

This is consistent with how regex string detectors are already wrapped (lines 362-375).

Tests

All 53 tests pass (51 existing + 2 new):

• test_custom_callable_detector_with_text_key_hash — verifies hash strategy works with text-only dicts
• test_custom_callable_detector_with_text_key_mask — verifies mask strategy works with text-only dicts

Changes

Changed files

• libs/langchain_v1/langchain/agents/middleware/_redaction.py (modified, +19/-1)
• libs/langchain_v1/tests/unit_tests/agents/middleware/implementations/test_pii.py (modified, +52/-0)

PR #35653: fix: handle custom PII detectors returning 'text' instead of 'value'

• Repository: langchain-ai/langchain
• Author: gambletan
• State: closed | merged: False
• Link: https://github.com/langchain-ai/langchain/pull/35653

Description (problem / solution / changelog)

Summary

Fixes #35647

Custom PII detectors may return match dicts with text instead of value (following common regex match conventions) and may omit the type key. This causes KeyError: 'value' when hash and mask strategies try to access match['value'].

Changes

Added a _normalize_match() helper in _redaction.py that:

• Accepts text as an alias for value
• Auto-populates type from the configured pii_type if missing
• Wraps custom callable detectors with normalization on output

Built-in detectors already return properly-typed PIIMatch dicts, so this only affects custom detectors.

Reproduction

def detect_phone(content: str) -> list[dict]:
    matches = []
    for match in re.finditer(r'\+91[\s.-]?[6-9]\d{9}', content):
        matches.append({
            "text": match.group(0),  # "text" not "value"
            "start": match.start(),
            "end": match.end(),
        })
    return matches

# Before fix: KeyError: 'value'
# After fix: works correctly
PIIMiddleware("phone", detector=detect_phone, strategy="hash")

Test plan

• Verify custom detectors with text key work with all strategies
• Verify built-in detectors still work unchanged
• Verify existing tests pass

🤖 Generated with Claude Code

Changed files

• libs/langchain_v1/langchain/agents/middleware/_redaction.py (modified, +26/-1)

PR #35662: langchain: fix KeyError on custom PII detector with hash/mask strategies

• Repository: langchain-ai/langchain
• Author: MaxwellCalkin
• State: closed | merged: False
• Link: https://github.com/langchain-ai/langchain/pull/35662

Description (problem / solution / changelog)

Summary

Fixes #35647

When a custom detector callable is provided to PIIMiddleware, it returns dicts with "text", "start", and "end" keys per the documented API. However, _apply_hash_strategy and _apply_mask_strategy access match["value"], which doesn't exist in the custom detector's output, causing KeyError: 'value'.

The "redact" and "block" strategies happen to work because they only access match["type"], match["start"], and match["end"] — never match["value"].

Root Cause

In resolve_detector(), when the detector is a callable (not None and not a str regex), it's returned directly without normalization:

# line 376
return detector

Built-in detectors and regex detectors always produce proper PIIMatch dicts with value key, but custom callables return {"text": ..., "start": ..., "end": ...} per the docs.

Fix

Wrap the custom callable to normalize its output into proper PIIMatch TypedDicts:

• match.get("value", match.get("text", "")) — accepts both value and text keys for backwards compatibility
• match.get("type", pii_type) — defaults the type to the configured pii_type if not provided

This is consistent with how regex_detector already normalizes regex match objects into PIIMatch dicts in the same function.

Test Plan

• Custom detector with "text" key works with all four strategies (block, redact, mask, hash)
• Custom detector with "value" key still works (backwards compatible)
• Built-in detectors and regex string detectors are unaffected (different code paths)

This PR was authored by Claude, Anthropic's AI assistant, as part of an effort to contribute meaningfully to open-source projects. More context: https://x.com/MaxwellCalkin/status/1898441007704731844

Changed files

• libs/langchain_v1/langchain/agents/middleware/_redaction.py (modified, +13/-1)