diff --git a/planning/releases/1.2.1.md b/planning/releases/1.2.1.md
new file mode 100644
index 0000000..afdb2c5
--- /dev/null
+++ b/planning/releases/1.2.1.md
@@ -0,0 +1,21 @@
+# lite-bootstrap 1.2.1 — lift the FastAPI 0.137 cap
+
+**1.2.1 is a patch release. No public-API or behavior changes.** It removes the temporary `fastapi<0.137` ceiling introduced in 1.1.1, now that the upstream `prometheus-fastapi-instrumentator` fix has shipped.
+
+## Dependency constraints
+
+- **`fastapi<0.137` cap removed** from the `fastapi` extra (the single declaration every `fastapi-*` extra composes from). FastAPI 0.137 and 0.138 now resolve.
+- **`prometheus-fastapi-instrumentator` floor raised** on the `fastapi-metrics` extra: `>=6.1` → `>=8.0.1`. The crash that motivated the cap required FastAPI ≥0.137 *and* instrumentator ≤8.0.0, so lifting the FastAPI ceiling is paired with a floor that guarantees the fixed instrumentator wherever metrics are installed.
+
+The original cap was added in 1.1.1 because `prometheus-fastapi-instrumentator` read `route.path` unconditionally and crashed on FastAPI 0.137's internal `_IncludedRouter` route type. That is fixed upstream in instrumentator [v8.0.1](https://github.com/trallnag/prometheus-fastapi-instrumentator/releases/tag/v8.0.1) (issue [#370](https://github.com/trallnag/prometheus-fastapi-instrumentator/issues/370), closed 2026-06-22). lite-bootstrap's own offline-docs guard (the `isinstance(route, Route)` filter shipped in 1.1.1) remains in place.
+
+Verified end-to-end against FastAPI 0.138.0 + prometheus-fastapi-instrumentator 8.0.2: full suite green at 100% coverage, including the offline-docs and metrics paths that previously crashed.
+
+## Backwards compatibility
+
+Fully backward compatible with 1.2.0. No public API or behavior changed; this is purely a loosening of resolution constraints. Installs that were held at FastAPI ≤0.136 by the cap will now resolve forward to current FastAPI.
+
+## References
+
+- Upstream fix: [prometheus-fastapi-instrumentator v8.0.1](https://github.com/trallnag/prometheus-fastapi-instrumentator/releases/tag/v8.0.1), issue [#370](https://github.com/trallnag/prometheus-fastapi-instrumentator/issues/370)
+- Original cap: 1.1.1 (PR [#122](https://github.com/modern-python/lite-bootstrap/pull/122))
diff --git a/pyproject.toml b/pyproject.toml
index a8cc3ac..fde75ae 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -51,11 +51,7 @@ free-all = [
     "lite-bootstrap[sentry,otl,logging,pyroscope]",
 ]
 fastapi = [
-    # FastAPI 0.137 introduced the internal `_IncludedRouter` route type, which
-    # prometheus-fastapi-instrumentator (<=8.0.0) does not handle (it reads `route.path`
-    # unconditionally and raises AttributeError). Cap until a fixed instrumentator ships.
-    # Upstream issue: https://github.com/trallnag/prometheus-fastapi-instrumentator/issues/370
-    "fastapi<0.137",
+    "fastapi",
 ]
 fastapi-sentry = [
     "lite-bootstrap[fastapi,sentry]",
@@ -69,7 +65,9 @@ fastapi-logging = [
 ]
 fastapi-metrics = [
     "lite-bootstrap[fastapi]",
-    "prometheus-fastapi-instrumentator>=6.1",
+    # >=8.0.1 carries the _IncludedRouter fix required for FastAPI >=0.137
+    # (trallnag/prometheus-fastapi-instrumentator#370).
+    "prometheus-fastapi-instrumentator>=8.0.1",
 ]
 fastapi-all = [
     "lite-bootstrap[fastapi-sentry,fastapi-otl,fastapi-logging,fastapi-metrics,pyroscope]",