fix(config): fall back to defaults on malformed numeric config values

CHANGELOG.md

@@ -41,6 +41,12 @@ All notable changes to vouch are documented here. Format follows
 - demo image build: `hatch_build.py` (the build hook pyproject.toml
   declares for console bundling) is copied into the docker build context;
   the image had been unbuildable since the hook landed (#474).
+- `recall.load_config` and `capture.load_config` now degrade to their
+  defaults on a malformed numeric value (e.g. `max_chars: a lot`), matching
+  the fallback contract their docstrings already promised and the pattern
+  `compile.load_config` already used. previously a config typo raised an
+  uncaught `ValueError` out of the SessionStart recall hook and any
+  hook-driven `observe()`/`finalize()` call (#488).
 
 ## [1.3.0] — 2026-07-14
 

src/vouch/capture.py

@@ -38,6 +38,15 @@ class CaptureConfig:
     dedup_window_seconds: float = DEFAULT_DEDUP_WINDOW_SECONDS
 
 
+def _coerce(value: Any, default: Any, cast: Any) -> Any:
+    # A config typo (min_observations: a few) must degrade to the default,
+    # not take down every hook-driven observe()/finalize() call.
+    try:
+        return cast(value)
+    except (TypeError, ValueError):
+        return default
+
+
 def load_config(store: KBStore) -> CaptureConfig:
     """Read ``capture:`` from config.yaml; fall back to defaults."""
     try:
@@ -51,9 +60,13 @@ def load_config(store: KBStore) -> CaptureConfig:
         return CaptureConfig()
     return CaptureConfig(
         enabled=bool(raw.get("enabled", DEFAULT_ENABLED)),
-        min_observations=int(raw.get("min_observations", DEFAULT_MIN_OBSERVATIONS)),
-        dedup_window_seconds=float(
-            raw.get("dedup_window_seconds", DEFAULT_DEDUP_WINDOW_SECONDS)
+        min_observations=_coerce(
+            raw.get("min_observations", DEFAULT_MIN_OBSERVATIONS),
+            DEFAULT_MIN_OBSERVATIONS, int,
+        ),
+        dedup_window_seconds=_coerce(
+            raw.get("dedup_window_seconds", DEFAULT_DEDUP_WINDOW_SECONDS),
+            DEFAULT_DEDUP_WINDOW_SECONDS, float,
         ),
     )
 

src/vouch/recall.py

@@ -13,6 +13,7 @@
 from __future__ import annotations
 
 from dataclasses import dataclass
+from typing import Any
 
 import yaml
 
@@ -32,6 +33,15 @@ class RecallConfig:
     max_chars: int = DEFAULT_MAX_CHARS
 
 
+def _coerce(value: Any, default: Any, cast: Any) -> Any:
+    # A config typo (max_chars: a lot) must degrade to the default, not
+    # take down the SessionStart hook that reads this config every run.
+    try:
+        return cast(value)
+    except (TypeError, ValueError):
+        return default
+
+
 def load_config(store: KBStore) -> RecallConfig:
     """Read ``recall:`` from config.yaml; fall back to defaults."""
     try:
@@ -45,7 +55,7 @@ def load_config(store: KBStore) -> RecallConfig:
         return RecallConfig()
     return RecallConfig(
         enabled=bool(raw.get("enabled", DEFAULT_ENABLED)),
-        max_chars=int(raw.get("max_chars", DEFAULT_MAX_CHARS)),
+        max_chars=_coerce(raw.get("max_chars", DEFAULT_MAX_CHARS), DEFAULT_MAX_CHARS, int),
     )
 
 

tests/test_capture.py

@@ -132,6 +132,19 @@ def test_load_config_capture_not_a_mapping(store: KBStore) -> None:
     assert cap.load_config(store).enabled is True
 
 
+def test_load_config_bad_numeric_values_fall_back_to_defaults(store: KBStore) -> None:
+    # a config typo must degrade, not take down every hook-driven
+    # observe()/finalize() call that reads this config.
+    store.config_path.write_text(
+        "capture:\n  enabled: true\n"
+        "  min_observations: a few\n  dedup_window_seconds: soon\n"
+    )
+    cfg = cap.load_config(store)
+    assert cfg.enabled is True
+    assert cfg.min_observations == cap.DEFAULT_MIN_OBSERVATIONS
+    assert cfg.dedup_window_seconds == cap.DEFAULT_DEDUP_WINDOW_SECONDS
+
+
 def test_read_observations_skips_blank_and_bad_lines(store: KBStore) -> None:
     p = cap.buffer_path(store, "s1")
     p.parent.mkdir(parents=True, exist_ok=True)

tests/test_recall.py

@@ -93,6 +93,17 @@ def test_load_config_recall_not_a_mapping(store: KBStore) -> None:
     assert recall.load_config(store).enabled is True
 
 
+def test_load_config_bad_max_chars_falls_back_to_default(store: KBStore) -> None:
+    # a config typo (max_chars: a lot) must degrade, not take down the
+    # SessionStart hook that reads this config on every new session.
+    store.config_path.write_text(
+        "recall:\n  enabled: true\n  max_chars: a lot\n", encoding="utf-8"
+    )
+    cfg = recall.load_config(store)
+    assert cfg.enabled is True
+    assert cfg.max_chars == recall.DEFAULT_MAX_CHARS
+
+
 def test_cli_recall_emits_digest(store: KBStore) -> None:
     from click.testing import CliRunner