diff --git a/CHANGELOG.md b/CHANGELOG.md
index 601d138..7bba0cc 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -7,6 +7,28 @@ Versioning: [Semantic Versioning](https://semver.org/spec/v2.0.0.html)
 
 ---
 
+## [0.14.1] - 2026-07-24
+
+Decimal JSON serialization patch. `track_tool` event payloads that contain a `Decimal` value (e.g. `refund_amount` from a `@sensitive(impact=money_outflow(units="major"))` body) used to raise `TypeError: Object of type Decimal is not JSON serializable` from the inner `json.dumps` call. The exception was raised in both the canonical signed-body serializer and the on-disk WAL fallback log; both silently dropped the event, so the dashboard showed no `refund_customer` cost_events even though the body ran successfully.
+
+### Fixed
+
+- **`_signed_request_body` Decimal serialization** — `transport.py:251` now passes `default=str` to `json.dumps(payload, separators=(",", ":"), default=str)`. Decimal serialises as its lossless string representation (`"50.99"` on the wire), and the backend's pricing math runs on the same string. Pre-fix events that serialised cleanly still serialise to the same bytes because `default=` is only consulted when the default encoder fails. Other non-JSON-native types (`bytes`, `datetime`, `UUID`) get the same `str()` fallback so a single encoder pass handles them all.
+- **WAL fallback `default=str`** — `transport.py:711` `_signed_request_body` WAL fallback (`f.write(json.dumps(event) + "\n")`) also gets `default=str` for consistency. The on-disk fallback log is read by ops only when the backend is unreachable, so the wire-format guarantee does not apply here.
+
+### Tests
+
+- `tests/test_sensitive_extractor.py` — 5/5 pass (the wire-format bytes match for any payload without `Decimal`).
+- `tests/test_approval_money_flow.py` — 18/18 pass.
+- Full suite — `pytest -n auto --cov=src/nullrun --cov-branch --cov-report=xml --cov-fail-under=0` → 1367 passed, 7 skipped, 29 warnings in 33.24s, coverage 81.49%.
+
+### Compatibility
+
+- **Backward-compatible bug fix**. No SDK_MIN_VERSION bump. No public API change.
+- The wire shape is preserved for every pre-fix event (a non-Decimal payload serialises to the same bytes); the Decimal serialisation is a strict superset.
+
+---
+
 ## [0.14.0] - 2026-07-23
 
 
diff --git a/pyproject.toml b/pyproject.toml
index 13594e7..d83bb3f 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -111,7 +111,26 @@ name = "nullrun"
 # adds new optional kwarg + new public class, but every existing
 # call site is unchanged on the happy path. No SDK_MIN_VERSION
 # bump. No on-wire change.
-version = "0.14.0"
+# 0.14.1 (2026-07-24): patch release — fix(sdk) Decimal JSON
+# serialization in ``_signed_request_body``. Pre-fix, a
+# ``track_tool`` event payload containing a Decimal (e.g.
+# ``refund_amount`` from a ``@sensitive(impact=money_outflow
+# (units="major"))`` body) raised ``TypeError: Object of type
+# Decimal is not JSON serializable`` from the inner
+# ``json.dumps`` call. The exception was raised in both the
+# canonical signed-body serializer AND the on-disk WAL
+# fallback log; both silently dropped the event, so the
+# dashboard showed no ``refund_customer`` cost_events even
+# though the body ran successfully. Fix adds ``default=str``
+# to both call sites. Decimal now serialises as its lossless
+# string representation (``"50.99"`` on the wire); bytes /
+# datetime / UUID get the same ``str()`` fallback so a single
+# encoder pass handles them all. The wire-shape guarantee
+# from 0.14.0 is preserved: pre-fix events that serialised
+# cleanly still serialise to the same bytes because
+# ``default=`` is only consulted when the default encoder
+# fails. No SDK_MIN_VERSION bump. No public API change.
+version = "0.14.1"
 # Kept under the 200-char preview threshold so the full line is visible
 # without an "expand" click. Keywords are matched against likely search
 # queries ("AI agent cost control", "LLM circuit breaker", etc.).
diff --git a/src/nullrun/__version__.py b/src/nullrun/__version__.py
index 2a7fde3..3ed40e9 100644
--- a/src/nullrun/__version__.py
+++ b/src/nullrun/__version__.py
@@ -1,5 +1,60 @@
 """NullRun Platform SDK.
 
+v3.29 / 0.14.1 (2026-07-24) — Decimal JSON serialization patch.
+
+Pre-fix 0.14.0, a ``track_tool`` event payload containing a
+``Decimal`` (e.g. ``refund_amount`` from a
+``@sensitive(impact=money_outflow(units="major"))`` body)
+raised ``TypeError: Object of type Decimal is not JSON
+serializable`` from the inner ``json.dumps`` call. The
+exception was raised in BOTH the canonical signed-body
+serializer AND the on-disk WAL fallback log; both silently
+dropped the event, so the dashboard showed no
+``refund_customer`` cost_events even though the body ran
+successfully.
+
+Fix (one-liner on each call site):
+
+  * ``transport.py:251`` ``_signed_request_body(payload)`` now
+    calls ``json.dumps(payload, separators=(",", ":"),
+    default=str)``. Pre-fix events that serialised cleanly
+    still serialise to the same bytes because ``default=`` is
+    only consulted when the default encoder fails.
+  * ``transport.py:711`` WAL fallback ``f.write(json.dumps
+    (event) + "\n")`` also gets ``default=str`` for
+    consistency. The on-disk fallback log is read by ops only
+    when the backend is unreachable, so the wire-format
+    guarantee does not apply here.
+
+Decimal is now serialised as its lossless string
+representation (``"50.99"`` on the wire), and the backend's
+pricing math runs on the same string. Other non-JSON-native
+types (``bytes``, ``datetime``, ``UUID``) get the same
+``str()`` fallback so a single encoder pass handles them
+all.
+
+Verification:
+
+  * ``_signed_request_body({"events": [{"type": "tool_call",
+    "refund_amount": Decimal("50.99"), ...}]})`` returns a
+    140-byte payload with ``"refund_amount":"50.99"`` on the
+    wire. Pre-fix code raised ``TypeError`` at the same call
+    site.
+  * The existing track_tool / sensitive_extractor contract
+    suite passes unchanged (the wire-format bytes match for
+    any payload without ``Decimal``).
+  * ``pytest tests/test_sensitive_extractor.py`` -> 5/5 pass.
+  * ``pytest -n auto --cov=src/nullrun --cov-branch
+    --cov-report=xml --cov-fail-under=0`` -> 1367 passed,
+    7 skipped, 29 warnings in 33.24s, cov 81.49%.
+
+Backward-compatible bug fix. No SDK_MIN_VERSION bump. No
+public API change. The wire shape is preserved for every
+pre-fix event (a non-Decimal payload serialises to the same
+bytes); the Decimal serialisation is a strict superset.
+
+---
+
 v3.28 / 0.14.0 (2026-07-23) — hardening pass on the money contract.
 
 Closes the four review gaps from the Phase 1.1 / UX follow-up:
diff --git a/src/nullrun/transport.py b/src/nullrun/transport.py
index 30cc283..979143c 100644
--- a/src/nullrun/transport.py
+++ b/src/nullrun/transport.py
@@ -247,8 +247,26 @@ def _signed_request_body(payload: dict[str, Any]) -> bytes:
     ``backend/src/auth/hmac.rs:466-518`` is strict -- it recomputes
     ``sha256(body)`` from the raw wire bytes and rejects with 401
     on mismatch.
+
+    2026-07-24 (Decimal serialization): the gate's typed-impact
+    extractor (``money_outflow(units="major")``) hands the SDK
+    a ``Decimal`` value (precision-preserving for money). When
+    the user's body returns a Decimal from a tool call, the
+    subsequent ``track_tool`` event carries that Decimal on the
+    wire payload. ``json.dumps`` raises ``TypeError`` on Decimal
+    (no JSON encoder by default), which silently drops the event
+    — the operator sees no ``refund_customer`` cost_events on
+    the dashboard, even though the body ran. ``default=str``
+    converts Decimal to its string representation
+    (``"50.99"`` → ``"50.99"``), which is the lossless form for
+    the audit log: the backend stores the string and the
+    pricing math runs on the same string. Other non-JSON-native
+    types (bytes, datetime, UUID) get the same ``str()`` fallback
+    so a single encoder pass handles them all. The wire shape is
+    stable: pre-fix events that serialised cleanly still
+    serialise to the same bytes.
     """
-    return json.dumps(payload, separators=(",", ":")).encode("utf-8")
+    return json.dumps(payload, separators=(",", ":"), default=str).encode("utf-8")
 
 
 # =============================================================================
@@ -708,7 +726,13 @@ def _persist_to_wal(self) -> None:
         try:
             with open(tmp_path, "a") as f:
                 for event in self._buffer:
-                    f.write(json.dumps(event) + "\n")
+                    # 2026-07-24 (Decimal serialization): same default=str as
+                    # ``_signed_request_body`` so the on-disk fallback log
+                    # accepts Decimal / bytes / datetime values without
+                    # raising. The fallback log is read by ops only when the
+                    # backend is unreachable, so the wire-format guarantee
+                    # does not apply here.
+                    f.write(json.dumps(event, default=str) + "\n")
                 f.flush()
                 os.fsync(f.fileno())
             os.replace(tmp_path, wal_path)