diff --git a/hindsight-api-slim/hindsight_api/engine/consolidation/consolidator.py b/hindsight-api-slim/hindsight_api/engine/consolidation/consolidator.py
index 4d4022b69..e63c788f5 100644
--- a/hindsight-api-slim/hindsight_api/engine/consolidation/consolidator.py
+++ b/hindsight-api-slim/hindsight_api/engine/consolidation/consolidator.py
@@ -217,7 +217,7 @@ def _dedup_active(config: Any) -> bool:
     skipped — it behaves exactly as it did before this feature, regardless of the configured
     threshold. This is why the feature can ship enabled-by-default without breaking Oracle.
     """
-    if config is None or getattr(config, "consolidation_dedup_threshold", 1.0) >= 1.0:
+    if config is None or config.consolidation_dedup_threshold >= 1.0:
         return False
     return get_config().database_backend != "oracle"
 
@@ -962,7 +962,7 @@ def _effective_scope_limit(config: Any, fact_tags: list[str]) -> int:
     """
     if config is None:
         return -1
-    for rule in _parse_scope_limit_rules(getattr(config, "observation_scope_limits", None)):
+    for rule in _parse_scope_limit_rules(config.observation_scope_limits):
         if _scope_matches_globs(rule.globs, fact_tags):
             return rule.limit
     return config.max_observations_per_scope
@@ -2900,7 +2900,7 @@ async def _consolidate_batch_with_llm(
     # note, and response_schema (all bank/batch-variable) are kept OUT of the
     # cached prefix so one cache serves all and it never busts within a run.
     system_prompt = build_consolidation_system_prompt(
-        llm_output_language=getattr(config, "llm_output_language", None),
+        llm_output_language=config.llm_output_language if config is not None else None,
     )
     user_content = build_consolidation_input(
         facts_text=facts_lines,
diff --git a/hindsight-api-slim/hindsight_api/engine/memory_engine.py b/hindsight-api-slim/hindsight_api/engine/memory_engine.py
index f9e11fcd9..f6f17bafa 100644
--- a/hindsight-api-slim/hindsight_api/engine/memory_engine.py
+++ b/hindsight-api-slim/hindsight_api/engine/memory_engine.py
@@ -38,7 +38,6 @@ from ..config import (
     DEFAULT_RECALL_INCLUDE_CHUNKS,
     DEFAULT_RECALL_MAX_TOKENS,
     DEFAULT_REFLECT_SOURCE_FACTS_MAX_TOKENS,
-    DEFAULT_RETAIN_CHUNK_SIZE,
     DEFAULT_STORE_DOCUMENT_TEXT,
     ENV_MODEL_INIT_TIMEOUT,
     HindsightConfig,
@@ -4896,8 +4895,8 @@ class MemoryEngine(MemoryEngineInterface):
     def _retain_chunking_config(config: HindsightConfig) -> _RetainChunkingConfig:
         """The chunk boundaries ``config`` implies, as the retain pipeline uses them."""
         return _RetainChunkingConfig(
-            chunk_size=getattr(config, "retain_chunk_size", DEFAULT_RETAIN_CHUNK_SIZE),
-            structured_chunk_size=getattr(config, "retain_structured_chunk_size", None),
+            chunk_size=config.retain_chunk_size,
+            structured_chunk_size=config.retain_structured_chunk_size,
         )
 
     async def _run_retain_execution(
diff --git a/hindsight-api-slim/hindsight_api/engine/retain/fact_extraction.py b/hindsight-api-slim/hindsight_api/engine/retain/fact_extraction.py
index b121d3813..3d275f5cc 100644
--- a/hindsight-api-slim/hindsight_api/engine/retain/fact_extraction.py
+++ b/hindsight-api-slim/hindsight_api/engine/retain/fact_extraction.py
@@ -1130,9 +1130,9 @@ def _build_extraction_prompt_and_schema(config) -> tuple[str, type]:
         base_response_class = FactExtractionResponseNoCausal
 
     # Add entity labels section if configured and build dynamic schema
-    entity_labels_raw = getattr(config, "entity_labels", None)
+    entity_labels_raw = config.entity_labels
     labels_cfg = parse_entity_labels(entity_labels_raw)
-    free_form_entities = getattr(config, "entities_allow_free_form", True)
+    free_form_entities = config.entities_allow_free_form
     labels_section = _build_labels_prompt_section(labels_cfg, free_form_entities)
     if labels_section:
         prompt = prompt + labels_section
@@ -1145,7 +1145,7 @@ def _build_extraction_prompt_and_schema(config) -> tuple[str, type]:
     # tokenization and LLM output language are separate concerns.
     from ..prompt_utils import output_language_directive
 
-    prompt = prompt + output_language_directive(getattr(config, "llm_output_language", None))
+    prompt = prompt + output_language_directive(config.llm_output_language)
 
     response_schema = base_response_class
 
@@ -1193,7 +1193,7 @@ def _retain_mission_preamble(config) -> str:
     No brace-escaping needed: unlike the system template, the user message is
     used verbatim, not passed through str.format().
     """
-    retain_mission = getattr(config, "retain_mission", None)
+    retain_mission = config.retain_mission
     if not retain_mission:
         return ""
     return (
@@ -1543,9 +1543,9 @@ async def _extract_facts_from_chunk(
                 validated_entities = _coerce_entity_strings(get_value("entities"))
 
                 # Post-process label entities from structured labels object
-                entity_labels_raw = getattr(config, "entity_labels", None)
+                entity_labels_raw = config.entity_labels
                 labels_cfg = parse_entity_labels(entity_labels_raw)
-                free_form_entities = getattr(config, "entities_allow_free_form", True)
+                free_form_entities = config.entities_allow_free_form
                 if labels_cfg and labels_cfg.attributes:
                     labels_lookup = build_labels_lookup(labels_cfg)
                     labels_data = llm_fact.get("labels") or {}
@@ -2297,9 +2297,9 @@ async def extract_facts_from_contents_batch_api(
             validated_entities = _coerce_entity_strings(get_value("entities"))
 
             # Post-process label entities from structured labels object
-            entity_labels_raw = getattr(config, "entity_labels", None)
+            entity_labels_raw = config.entity_labels
             labels_cfg_batch = parse_entity_labels(entity_labels_raw)
-            free_form_entities_batch = getattr(config, "entities_allow_free_form", True)
+            free_form_entities_batch = config.entities_allow_free_form
             if labels_cfg_batch and labels_cfg_batch.attributes:
                 labels_lookup_batch = build_labels_lookup(labels_cfg_batch)
                 labels_data = llm_fact.get("labels") or {}
@@ -2758,7 +2758,7 @@ def _inject_label_tags(facts: list[ExtractedFactType], config) -> None:
     This lets entity labels double as tags, enabling filtering via the
     existing tags API without any extra query infrastructure.
     """
-    labels_cfg = parse_entity_labels(getattr(config, "entity_labels", None))
+    labels_cfg = parse_entity_labels(config.entity_labels)
     if not labels_cfg:
         return
     tag_group_keys = {g.key.lower() for g in labels_cfg.attributes if g.tag}
diff --git a/hindsight-api-slim/hindsight_api/engine/retain/orchestrator.py b/hindsight-api-slim/hindsight_api/engine/retain/orchestrator.py
index b380ce235..42ce50f52 100644
--- a/hindsight-api-slim/hindsight_api/engine/retain/orchestrator.py
+++ b/hindsight-api-slim/hindsight_api/engine/retain/orchestrator.py
@@ -67,7 +67,7 @@ def redact_document_body(body: str, config: Any) -> str:
     whole document once per sub-batch (issue #3282).
     """
     try:
-        policy = parse_policy(getattr(config, "memory_defense", None))
+        policy = parse_policy(config.memory_defense)
     except Exception:
         return body
     if not policy.enabled:
@@ -425,7 +425,7 @@ async def _pre_resolve_phase1(
             processed_facts,
             log_buffer,
             user_entities_per_content=user_entities_per_content,
-            entity_labels=getattr(config, "entity_labels", None),
+            entity_labels=config.entity_labels,
         )
 
         # Semantic ANN search on the same connection (autocommit, no transaction).
@@ -714,7 +714,7 @@ async def _streaming_batch_write_ext(
                             combined_content,
                             retain_params,
                             merged_tags,
-                            store_document_text=getattr(config, "store_document_text", True),
+                            store_document_text=config.store_document_text,
                         )
                         log_buffer.append(
                             f"[streaming] Document {effective_doc_id} updated (recovery, preserving existing chunks)"
@@ -729,7 +729,7 @@ async def _streaming_batch_write_ext(
                             retain_params,
                             merged_tags,
                             ops=pool.ops,
-                            store_document_text=getattr(config, "store_document_text", True),
+                            store_document_text=config.store_document_text,
                             txn=ext_txn,
                         )
                         log_buffer.append(f"[streaming] Document {effective_doc_id} tracked (full content)")
@@ -761,7 +761,7 @@ async def _streaming_batch_write_ext(
                         effective_doc_id,
                         batch_chunk_meta,
                         ops=pool.ops,
-                        store_document_text=getattr(config, "store_document_text", True),
+                        store_document_text=config.store_document_text,
                     )
 
                 # Entity registry reassert (Postgres `entities`): re-create the resolved parents
@@ -926,7 +926,7 @@ async def _delta_batch_write_ext(
                         effective_doc_id,
                         remapped_chunks,
                         ops=pool.ops,
-                        store_document_text=getattr(config, "store_document_text", True),
+                        store_document_text=config.store_document_text,
                     )
 
                 # Entity registry reassert (Postgres `entities`) — see the streaming path (#2662).
@@ -1218,7 +1218,7 @@ async def retain_batch(
     # object at this point (see _retain_batch_async_internal). On a non-allow
     # decision we redact in place or drop the item, and fire a
     # memory_defense.triggered webhook when one is configured.
-    _policy = parse_policy(getattr(config, "memory_defense", None))
+    _policy = parse_policy(config.memory_defense)
     _blocked_violations: list[BlockedViolation] = []
 
     if memory_defense_extension is not None and _policy.enabled:
@@ -1492,9 +1492,15 @@ async def retain_batch(
     # Even small documents go through the same path — they just end up as a
     # single batch. This eliminates the maintenance burden of two separate
     # retain code paths.
-    chunk_batch_size = getattr(config, "retain_chunk_batch_size", 100)
-    chunk_size = getattr(config, "retain_chunk_size", 3000)
-    structured_chunk_size = getattr(config, "retain_structured_chunk_size", None)
+    chunk_batch_size = config.retain_chunk_batch_size
+    # Direct attribute access, never getattr-with-default: these two decide chunk
+    # boundaries, and the delta path must derive them from the very same resolved
+    # config object. A getattr default silently substitutes the global value when
+    # handed the wrong config (StaticConfigProxy raises ConfigFieldAccessError,
+    # an AttributeError subclass, for bank-configurable fields) — which re-chunks
+    # at different boundaries and makes every stored chunk look changed. Fail loud.
+    chunk_size = config.retain_chunk_size
+    structured_chunk_size = config.retain_structured_chunk_size
     all_pre_chunks: list[str] = []
     chunk_to_content: list[int] = []  # maps chunk index -> index into contents
     for content_idx, content in enumerate(contents):
@@ -1703,7 +1709,7 @@ async def _store_document_bodies(
         content_hash=content_hash,
         # Honour store_document_text: when a deployment opts out of keeping the full text, only the
         # chunk texts (needed for citation) go to the store, not the whole document body.
-        original_text=combined_content if getattr(config, "store_document_text", True) else None,
+        original_text=combined_content if config.store_document_text else None,
         chunk_texts=list(chunk_texts),
         tags=list(merged_tags or []),
         metadata={},
@@ -2138,7 +2144,7 @@ async def _streaming_retain_batch(
                                 combined_content,
                                 retain_params,
                                 merged_tags,
-                                store_document_text=getattr(config, "store_document_text", True),
+                                store_document_text=config.store_document_text,
                             )
                         else:
                             # A 0-fact re-ingest still deletes the outgoing memories — tag that
@@ -2155,7 +2161,7 @@ async def _streaming_retain_batch(
                                 retain_params,
                                 merged_tags,
                                 ops=pool.ops,
-                                store_document_text=getattr(config, "store_document_text", True),
+                                store_document_text=config.store_document_text,
                                 txn=_edge_txn,
                             )
                             # Re-record the witness now that the group's writes have happened, so
@@ -2329,7 +2335,7 @@ async def _streaming_retain_batch(
                                 combined_content,
                                 retain_params,
                                 merged_tags,
-                                store_document_text=getattr(config, "store_document_text", True),
+                                store_document_text=config.store_document_text,
                             )
                             log_buffer.append(
                                 f"[streaming] Document {effective_doc_id} updated "
@@ -2345,7 +2351,7 @@ async def _streaming_retain_batch(
                                 retain_params,
                                 merged_tags,
                                 ops=pool.ops,
-                                store_document_text=getattr(config, "store_document_text", True),
+                                store_document_text=config.store_document_text,
                                 txn=_group_txn,
                             )
                             log_buffer.append(f"[streaming] Document {effective_doc_id} tracked (full content)")
@@ -2391,7 +2397,7 @@ async def _streaming_retain_batch(
                             effective_doc_id,
                             batch_chunk_meta,
                             ops=pool.ops,
-                            store_document_text=getattr(config, "store_document_text", True),
+                            store_document_text=config.store_document_text,
                         )
                         log_buffer.append(
                             f"  Store chunks: {len(batch_chunk_meta)} chunks in {time.time() - step_start:.3f}s"
@@ -2589,7 +2595,7 @@ async def _streaming_retain_batch(
                             combined_content,
                             retain_params,
                             merged_tags,
-                            store_document_text=getattr(config, "store_document_text", True),
+                            store_document_text=config.store_document_text,
                         )
                     else:
                         # A no-facts re-ingest still deletes the outgoing memories — tag that
@@ -2606,7 +2612,7 @@ async def _streaming_retain_batch(
                             retain_params,
                             merged_tags,
                             ops=pool.ops,
-                            store_document_text=getattr(config, "store_document_text", True),
+                            store_document_text=config.store_document_text,
                             txn=_edge_txn,
                         )
                         # Re-record the witness now that the group's writes have happened, so the
@@ -3211,7 +3217,7 @@ async def _try_delta_retain(
                         effective_doc_id,
                         remapped_chunks,
                         ops=pool.ops,
-                        store_document_text=getattr(config, "store_document_text", True),
+                        store_document_text=config.store_document_text,
                     )
                     for chunk_idx, chunk_id in chunk_id_map.items():
                         chunk_id_map_by_doc[(effective_doc_id, chunk_idx)] = chunk_id
@@ -3402,14 +3408,17 @@ def _chunk_contents_for_delta(contents: list[RetainContent], config) -> dict[int
     Chunk contents the same way the streaming path does, returning a map of
     global_chunk_index -> chunk_text.
 
-    Must use the same chunk_size as the streaming path (default 3000) so that
-    chunk boundaries match and delta can detect unchanged chunks.
-    Previously defaulted to 120000, causing all chunks to appear changed on retry.
+    Must read chunk_size/structured_chunk_size off the same resolved ``config``
+    the streaming path uses, so chunk boundaries match and delta can detect
+    unchanged chunks. Two earlier incidents came from this drifting: a 120000
+    default made all chunks appear changed on retry, and a getattr default
+    silently swapped a bank's resolved size for the global one.
     """
     result = {}
     global_chunk_idx = 0
-    chunk_size = getattr(config, "retain_chunk_size", 3000)
-    structured_chunk_size = getattr(config, "retain_structured_chunk_size", None)
+    # Same resolved-config invariant as the streaming path — see the note there.
+    chunk_size = config.retain_chunk_size
+    structured_chunk_size = config.retain_structured_chunk_size
     for content in contents:
         chunks = fact_extraction.chunk_text(
             content.content,
diff --git a/hindsight-api-slim/hindsight_api/engine/search/retrieval.py b/hindsight-api-slim/hindsight_api/engine/search/retrieval.py
index 9b2b835b4..00be800d2 100644
--- a/hindsight-api-slim/hindsight_api/engine/search/retrieval.py
+++ b/hindsight-api-slim/hindsight_api/engine/search/retrieval.py
@@ -14,7 +14,7 @@ from dataclasses import dataclass, field
 from datetime import UTC, datetime
 from typing import TYPE_CHECKING, Any, Optional
 
-from ...config import DEFAULT_BM25_MAX_QUERY_TERMS, get_config
+from ...config import get_config
 from ..db.ops import UpdatedWindow
 from ..memory_engine import fq_table, get_current_schema
 from ..sql import create_sql_dialect
@@ -267,7 +267,7 @@ async def retrieve_semantic_bm25_combined_sql(
     # --- BM25 UNION ALL arms (one per fact_type, only when tokens present) ---
     if _include_bm25:
         text_ext = config.text_search_extension
-        max_query_terms = getattr(config, "bm25_max_query_terms", DEFAULT_BM25_MAX_QUERY_TERMS)
+        max_query_terms = config.bm25_max_query_terms
         bm25_tokens = tokens
         # Native tsvector has no IDF and ranks every `@@` match, so a long OR
         # query over common terms scans and ranks a large fraction of the bank
@@ -281,7 +281,7 @@ async def retrieve_semantic_bm25_combined_sql(
             text_ext == "native"
             and max_query_terms > 0
             and len(tokens) > max_query_terms
-            and getattr(config, "bm25_selective_terms", True)
+            and config.bm25_selective_terms
             and getattr(conn, "backend_type", "postgresql") == "postgresql"
         ):
             bm25_tokens = await select_selective_bm25_tokens(
diff --git a/hindsight-api-slim/tests/test_ann_iterative_scan.py b/hindsight-api-slim/tests/test_ann_iterative_scan.py
index c0afc0d5b..7644f88a8 100644
--- a/hindsight-api-slim/tests/test_ann_iterative_scan.py
+++ b/hindsight-api-slim/tests/test_ann_iterative_scan.py
@@ -20,6 +20,8 @@ Covers:
 
 from __future__ import annotations
 
+import dataclasses
+
 import random
 import uuid
 from types import SimpleNamespace
@@ -106,7 +108,10 @@ class FakeConn:
 @pytest.fixture
 def search_path(monkeypatch):
     dialect = FakeDialect()
-    config = SimpleNamespace(
+    from hindsight_api.config import _get_raw_config
+
+    config = dataclasses.replace(
+        _get_raw_config(),
         semantic_min_similarity=0.0,
         bm25_min_score=0.0,
         text_search_extension="native",
diff --git a/hindsight-api-slim/tests/test_causal_relation_offsets.py b/hindsight-api-slim/tests/test_causal_relation_offsets.py
index 5aaff7fe3..b83b73902 100644
--- a/hindsight-api-slim/tests/test_causal_relation_offsets.py
+++ b/hindsight-api-slim/tests/test_causal_relation_offsets.py
@@ -1,8 +1,10 @@
+import dataclasses
 import json
 from types import SimpleNamespace
 
 import pytest
 
+from hindsight_api.config import _get_raw_config
 from hindsight_api.engine.response_models import TokenUsage
 from hindsight_api.engine.retain import fact_extraction
 from hindsight_api.engine.retain.fact_extraction import CausalRelation, Fact
@@ -30,7 +32,7 @@ async def test_causal_targets_are_offset_from_extraction_group_start(monkeypatch
     monkeypatch.setattr(fact_extraction, "_add_temporal_offsets", lambda *_args: None)
     monkeypatch.setattr(fact_extraction, "_inject_label_tags", lambda *_args: None)
 
-    config = SimpleNamespace(retain_extraction_mode="normal", retain_batch_enabled=False)
+    config = dataclasses.replace(_get_raw_config(), retain_extraction_mode="normal", retain_batch_enabled=False)
     facts, _, _ = await fact_extraction.extract_facts_from_contents(
         [RetainContent(content="preceding"), RetainContent(content="causal group")],
         llm_config=None,
@@ -64,7 +66,7 @@ async def test_each_chunk_uses_its_own_causal_index_base(monkeypatch):
     monkeypatch.setattr(fact_extraction, "_add_temporal_offsets", lambda *_args: None)
     monkeypatch.setattr(fact_extraction, "_inject_label_tags", lambda *_args: None)
 
-    config = SimpleNamespace(retain_extraction_mode="normal", retain_batch_enabled=False)
+    config = dataclasses.replace(_get_raw_config(), retain_extraction_mode="normal", retain_batch_enabled=False)
     facts, _, _ = await fact_extraction.extract_facts_from_contents(
         [RetainContent(content="two chunks")],
         llm_config=None,
@@ -145,7 +147,8 @@ async def test_batch_causal_targets_use_each_chunk_start(monkeypatch):
     monkeypatch.setattr(fact_extraction, "_add_temporal_offsets", lambda *_args: None)
     monkeypatch.setattr(fact_extraction, "_inject_label_tags", lambda *_args: None)
 
-    config = SimpleNamespace(
+    config = dataclasses.replace(
+        _get_raw_config(),
         retain_extract_causal_links=True,
         retain_chunk_size=100,
         retain_structured_chunk_size=100,
diff --git a/hindsight-api-slim/tests/test_fact_extraction_retry.py b/hindsight-api-slim/tests/test_fact_extraction_retry.py
index 389b6296c..0a671cfc9 100644
--- a/hindsight-api-slim/tests/test_fact_extraction_retry.py
+++ b/hindsight-api-slim/tests/test_fact_extraction_retry.py
@@ -9,6 +9,7 @@ BaseException'), which happened when last_error was only set in the
 BadRequestError handler and not for non-dict JSON responses.
 """
 
+import dataclasses
 import json
 from datetime import datetime, timezone
 from unittest.mock import AsyncMock, MagicMock, patch
@@ -134,22 +135,23 @@ async def test_output_too_long_drops_unsplittable_subchunk_without_recursing():
 
 def _make_config(llm_max_retries: int = 3, retain_llm_max_retries: int | None = None):
     """Build a minimal HindsightConfig for fact extraction tests."""
-    from hindsight_api.config import HindsightConfig
+    from hindsight_api.config import _get_raw_config
 
-    cfg = MagicMock(spec=HindsightConfig)
-    cfg.retain_llm_max_retries = retain_llm_max_retries
-    cfg.llm_max_retries = llm_max_retries
-    cfg.retain_llm_initial_backoff = None
-    cfg.llm_initial_backoff = 0.0
-    cfg.retain_llm_max_backoff = None
-    cfg.llm_max_backoff = 0.0
-    cfg.retain_max_completion_tokens = 8192
-    cfg.retain_extraction_mode = "concise"
-    cfg.retain_extract_causal_links = False
-    cfg.retain_mission = None
-    cfg.llm_temperature_retain = 0.1
-    cfg.llm_strict_schema_retain = False
-    return cfg
+    return dataclasses.replace(
+        _get_raw_config(),
+        retain_llm_max_retries=retain_llm_max_retries,
+        llm_max_retries=llm_max_retries,
+        retain_llm_initial_backoff=None,
+        llm_initial_backoff=0.0,
+        retain_llm_max_backoff=None,
+        llm_max_backoff=0.0,
+        retain_max_completion_tokens=8192,
+        retain_extraction_mode="concise",
+        retain_extract_causal_links=False,
+        retain_mission=None,
+        llm_temperature_retain=0.1,
+        llm_strict_schema_retain=False,
+    )
 
 
 def _make_llm_config(mock_response):
diff --git a/hindsight-api-slim/tests/test_llm_strict_schema.py b/hindsight-api-slim/tests/test_llm_strict_schema.py
index 222f13e36..b10e2a5b5 100644
--- a/hindsight-api-slim/tests/test_llm_strict_schema.py
+++ b/hindsight-api-slim/tests/test_llm_strict_schema.py
@@ -23,6 +23,7 @@ reads the same retain-scoped field rather than the global flag, keeping the batc
 and streaming paths in agreement.
 """
 
+import dataclasses
 from types import SimpleNamespace
 from unittest.mock import AsyncMock, MagicMock, patch
 
@@ -45,18 +46,16 @@ class _Resp(BaseModel):
 
 
 def _config_with(strict: bool) -> object:
-    """A config proxy that overrides only llm_strict_schema (avoids recursion)."""
-    from hindsight_api.config import get_config
+    """A real config overriding only llm_strict_schema.
 
-    real = get_config()
+    Delegating to ``get_config()`` used to work by accident: the retain path read
+    bank-configurable fields through getattr defaults, so the StaticConfigProxy
+    guard was swallowed. It now reads them directly, so the test needs the raw
+    resolved config rather than the global proxy.
+    """
+    from hindsight_api.config import _get_raw_config
 
-    class _Cfg:
-        llm_strict_schema = strict
-
-        def __getattr__(self, name):
-            return getattr(real, name)
-
-    return _Cfg()
+    return dataclasses.replace(_get_raw_config(), llm_strict_schema=strict)
 
 
 # --------------------------------------------------------------------------- #
@@ -298,22 +297,23 @@ def _retain_config(strict_retain: bool):
     A bank-resolved config, not the global one -- retain_extraction_mode and friends
     are bank-configurable and raise if read off global config.
     """
-    from hindsight_api.config import HindsightConfig
+    from hindsight_api.config import _get_raw_config
 
-    cfg = MagicMock(spec=HindsightConfig)
-    cfg.retain_llm_max_retries = 1
-    cfg.llm_max_retries = 1
-    cfg.retain_llm_initial_backoff = 0.0
-    cfg.llm_initial_backoff = 0.0
-    cfg.retain_llm_max_backoff = 0.0
-    cfg.llm_max_backoff = 0.0
-    cfg.retain_max_completion_tokens = 8192
-    cfg.retain_extraction_mode = "concise"
-    cfg.retain_extract_causal_links = False
-    cfg.retain_mission = None
-    cfg.llm_temperature_retain = 0.1
-    cfg.llm_strict_schema_retain = strict_retain
-    return cfg
+    return dataclasses.replace(
+        _get_raw_config(),
+        retain_llm_max_retries=1,
+        llm_max_retries=1,
+        retain_llm_initial_backoff=0.0,
+        llm_initial_backoff=0.0,
+        retain_llm_max_backoff=0.0,
+        llm_max_backoff=0.0,
+        retain_max_completion_tokens=8192,
+        retain_extraction_mode="concise",
+        retain_extract_causal_links=False,
+        retain_mission=None,
+        llm_temperature_retain=0.1,
+        llm_strict_schema_retain=strict_retain,
+    )
 
 
 @pytest.mark.asyncio
diff --git a/hindsight-api-slim/tests/test_multilingual_bm25.py b/hindsight-api-slim/tests/test_multilingual_bm25.py
index 9042430c5..b033cd744 100644
--- a/hindsight-api-slim/tests/test_multilingual_bm25.py
+++ b/hindsight-api-slim/tests/test_multilingual_bm25.py
@@ -233,7 +233,17 @@ def test_postgresql_extension_bm25_keeps_raw_query_text():
 
 
 @pytest.mark.asyncio
-async def test_combined_retrieval_uses_default_bm25_cap_for_legacy_config(monkeypatch):
+async def test_combined_retrieval_rejects_config_missing_bm25_cap(monkeypatch):
+    """A config object lacking the BM25 cap fields fails loudly instead of defaulting.
+
+    This used to read ``getattr(config, "bm25_max_query_terms", DEFAULT_...)`` and
+    silently fall back, on the theory that a config could predate the field. It
+    cannot: ``HindsightConfig`` is a dataclass that always defines both fields, so
+    only a stub like the one below can produce that state — and when one does reach
+    here it is a wrong-config bug, not a legacy config. Silently substituting a
+    global default for a resolved value is exactly what made #3584 undiagnosable.
+    """
+
     class FakeDialect:
         max_query_terms: int | None = None
 
@@ -263,18 +273,18 @@ async def test_combined_retrieval_uses_default_bm25_cap_for_legacy_config(monkey
     monkeypatch.setattr(retrieval_mod, "get_config", lambda: legacy_config)
     monkeypatch.setattr(retrieval_mod, "create_sql_dialect", lambda backend: fake_dialect)
 
-    result = await retrieval_mod.retrieve_semantic_bm25_combined_sql(
-        FakeConn(),
-        "[0.0]",
-        "alpha beta",
-        "bank-1",
-        ["observation"],
-        5,
-    )
+    with pytest.raises(AttributeError, match="bm25_max_query_terms"):
+        await retrieval_mod.retrieve_semantic_bm25_combined_sql(
+            FakeConn(),
+            "[0.0]",
+            "alpha beta",
+            "bank-1",
+            ["observation"],
+            5,
+        )
 
-    assert result == {"observation": retrieval_mod.SemanticBm25Result(semantic=[], bm25=[], graph_seeds=None)}
-    # A config predating the field falls back to the current default cap.
-    assert fake_dialect.max_query_terms == retrieval_mod.DEFAULT_BM25_MAX_QUERY_TERMS
+    # It raised while resolving the cap, so the dialect was never handed a bogus one.
+    assert fake_dialect.max_query_terms is None
 
 
 @pytest.mark.parametrize("selective", [True, False])
diff --git a/hindsight-api-slim/tests/test_prompt_brace_escape.py b/hindsight-api-slim/tests/test_prompt_brace_escape.py
index 13c7abf33..03cbb25d9 100644
--- a/hindsight-api-slim/tests/test_prompt_brace_escape.py
+++ b/hindsight-api-slim/tests/test_prompt_brace_escape.py
@@ -4,6 +4,7 @@ User-supplied text (missions, custom instructions) may contain literal braces
 (e.g. JSON examples). These must survive ``str.format()`` without crashing.
 """
 
+import dataclasses
 import pytest
 
 from hindsight_api.engine.prompt_utils import escape_for_prompt
@@ -104,18 +105,21 @@ class TestReflectBraceSafety:
 
 class TestRetainBraceSafety:
     def _make_config(self, **overrides):
-        """Minimal config-like object for _build_extraction_prompt_and_schema."""
-        from types import SimpleNamespace
+        """A real config for _build_extraction_prompt_and_schema.
+
+        Not a stub: the retain path reads its config fields directly, so a partial
+        namespace raises AttributeError on the first field it does not define.
+        """
+        from hindsight_api.config import _get_raw_config
 
         defaults = {
             "retain_extraction_mode": "concise",
             "retain_extract_causal_links": False,
             "retain_mission": None,
             "retain_custom_instructions": None,
-            "retain_taxonomy": None,
         }
         defaults.update(overrides)
-        return SimpleNamespace(**defaults)
+        return dataclasses.replace(_get_raw_config(), **defaults)
 
     def test_retain_mission_with_json(self):
         from hindsight_api.engine.retain.fact_extraction import (
diff --git a/hindsight-api-slim/tests/test_retain_chunking_config_access.py b/hindsight-api-slim/tests/test_retain_chunking_config_access.py
new file mode 100644
index 000000000..f12b2c2b4
--- /dev/null
+++ b/hindsight-api-slim/tests/test_retain_chunking_config_access.py
@@ -0,0 +1,49 @@
+"""
+The retain path must read its chunking parameters off the *resolved* config.
+
+Regression guard for #3584. Both the streaming write path and the delta compare
+chunk the same content, and delta detects unchanged chunks by comparing content
+hashes at equal chunk_index — so the two must agree on chunk boundaries. They do
+only as long as both derive chunk_size/structured_chunk_size from the same
+resolved HindsightConfig.
+
+These used to be read as ``getattr(config, "retain_chunk_size", 3000)``. Because
+``StaticConfigProxy`` signals "this field is bank-configurable" by raising
+``ConfigFieldAccessError`` — an ``AttributeError`` subclass — that default
+swallowed the guard and silently substituted the global value for the bank's.
+A bank configured at 12000 would then be re-chunked at 3000, no chunk index
+could match, and every append fell back to a full re-extraction of the whole
+document. Direct attribute access makes a wrong config object fail loudly.
+"""
+
+import dataclasses
+
+import pytest
+
+from hindsight_api.config import ConfigFieldAccessError, StaticConfigProxy, _get_raw_config
+from hindsight_api.engine.retain.orchestrator import _chunk_contents_for_delta
+from hindsight_api.engine.retain.types import RetainContent
+
+
+def _contents(text: str) -> list[RetainContent]:
+    return [RetainContent(content=text)]
+
+
+def test_delta_chunking_rejects_global_config():
+    """Handed global config, the delta chunker raises instead of defaulting to 3000."""
+    proxy = StaticConfigProxy(_get_raw_config())
+
+    with pytest.raises(ConfigFieldAccessError, match="retain_chunk_size"):
+        _chunk_contents_for_delta(_contents("word. " * 5000), proxy)
+
+
+def test_delta_chunking_uses_resolved_chunk_size():
+    """Boundaries come from the resolved value, not from a hardcoded default."""
+    text = "word. " * 5000
+
+    base = _get_raw_config()
+    at_12k = _chunk_contents_for_delta(_contents(text), dataclasses.replace(base, retain_chunk_size=12000))
+    at_3k = _chunk_contents_for_delta(_contents(text), dataclasses.replace(base, retain_chunk_size=3000))
+
+    assert max(len(c) for c in at_12k.values()) > 3000
+    assert len(at_12k) < len(at_3k)