fix: declare typing-extensions as core's runtime dependency (#158)

Bare `pip install lite-bootstrap` + `import lite_bootstrap` (no extras) crashed
on undeclared typing_extensions: base.py uses `typing_extensions.Self` and
healthchecks_instrument.py's TypedDict is a FastAPI response model that pydantic
requires be a `typing_extensions.TypedDict` on Python < 3.12 (stdlib
typing.TypedDict is rejected there). So genuine zero-dependency core is not
achievable while supporting 3.10/3.11 — declare typing-extensions (pure Python,
free-threaded-friendly). Pre-existing (bare 1.2.3 failed identically); surfaced
by a clean-room 3.14t install of published 1.3.0. Ships as 1.3.1.

Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: lesnik512

planning/changes/2026-07-19.03-core-zero-dep-typing-extensions.md

@@ -0,0 +1,72 @@
+---
+summary: Declare `typing-extensions` as core's runtime dependency so a bare `import lite_bootstrap` (no extras) works — the code uses it at runtime and pydantic requires `typing_extensions.TypedDict` on Python < 3.12, so genuine zero-dependency is not achievable while supporting 3.10/3.11.
+---
+
+# Design: Declare the runtime `typing_extensions` core dependency
+
+## Summary
+
+`lite-bootstrap` core imports `typing_extensions` at runtime but never declared
+it, so a bare `pip install lite-bootstrap` + `import lite_bootstrap` (no extras)
+crashes with `ModuleNotFoundError: No module named 'typing_extensions'`. Declare
+`typing-extensions` as core's one dependency. (An attempt to instead *remove* the
+usage and keep core zero-dependency failed on Python < 3.12 — see below.)
+
+## Motivation
+
+Found by a clean-room install of the published `1.3.0` on a fresh 3.14t venv:
+core installed with **zero** declared dependencies (after orjson became opt-in),
+but `import lite_bootstrap` immediately raised on `base.py`'s top-level
+`import typing_extensions`. Pre-existing (bare `lite-bootstrap==1.2.3` fails
+identically — its only core dep, `orjson`, doesn't pull `typing_extensions`);
+every install with any extra masked it, since extras pull `typing_extensions` in
+transitively. 1.3.0's "zero-dependency core" claim was therefore false.
+
+Two runtime uses:
+
+- `base.py:4,24,30` — `typing_extensions.Self` return annotations.
+- `healthchecks_instrument.py:8` — `class HealthCheckTypedDict(typing_extensions.TypedDict, ...)`,
+  used as a FastAPI response model (`health_check_handler() -> HealthCheckTypedDict`).
+
+## Design
+
+`pyproject.toml`: `dependencies = ["typing-extensions"]`. `typing-extensions` is
+pure Python, so core stays free-threaded-friendly; it is the leanest possible
+core (one small, ubiquitous dependency).
+
+## Rejected: remove the usage to keep core zero-dependency
+
+Attempted (deferred `Self` annotations via `from __future__ import annotations` +
+`TYPE_CHECKING`, and `typing.TypedDict` in healthchecks). It passed locally on
+3.12 and on an isolated 3.10 TypedDict construction, but **failed the CI matrix
+on 3.10 and 3.11**: pydantic rejects a stdlib `typing.TypedDict` model on Python
+< 3.12 —
+
+```
+PydanticUserError: Please use `typing_extensions.TypedDict` instead of
+`typing.TypedDict` on Python < 3.12.
+```
+
+Because `HealthCheckTypedDict` is a FastAPI/pydantic response model, it must be a
+`typing_extensions.TypedDict` for as long as 3.10/3.11 are supported. So core
+genuinely needs `typing_extensions` at runtime; declaring it is the honest fix.
+
+## Non-goals
+
+- Dropping Python 3.10/3.11 (which would make zero-dep achievable). Out of scope.
+- Amending the published `1.3.0` note (immutable); `1.3.1` states the corrected
+  "one pure-Python dependency" story.
+
+## Testing
+
+- Clean-room bare install on 3.14t: `pip install lite-bootstrap` now pulls
+  `typing-extensions`, and `import lite_bootstrap` + `FreeBootstrapper.bootstrap()`
+  succeed.
+- `just test` 100% coverage on the full 3.10-3.14 matrix (the FastAPI healthcheck
+  schema builds on every version); `just lint-ci` clean.
+
+## Risk
+
+- **None material.** Adds one pure-Python dependency that the code already
+  required at runtime; strictly fixes a crash. `typing-extensions` is already
+  present transitively in every non-bare install.

planning/releases/1.3.1.md

@@ -0,0 +1,30 @@
+# lite-bootstrap 1.3.1 — fix bare-install import (`typing-extensions`)
+
+**1.3.1 is a patch release. Fully backward compatible with 1.3.0.**
+
+## Bug fixes
+
+- **Bare `import lite_bootstrap` no longer crashes on a missing
+  `typing_extensions`.** Core uses `typing_extensions` at runtime (a `Self`
+  return annotation, and a `TypedDict` FastAPI response model that pydantic
+  requires be a `typing_extensions.TypedDict` on Python < 3.12) but never
+  declared it, so `pip install lite-bootstrap` with no extras followed by
+  `import lite_bootstrap` raised `ModuleNotFoundError: No module named
+  'typing_extensions'`. `typing-extensions` is now declared as core's single
+  dependency. It is pure Python, so free-threaded support is unchanged, and this
+  is the leanest possible core.
+
+  This corrects 1.3.0's note, which called core "zero-dependency": the code
+  genuinely needs `typing_extensions` while Python 3.10/3.11 are supported. The
+  bug was pre-existing (bare `1.2.3` failed the same way); every install with any
+  extra masked it, because extras pull `typing_extensions` in transitively.
+
+## Backwards compatibility
+
+Fully compatible with 1.3.0. No API or configuration changes; the only
+difference is that a bare-core install now resolves `typing-extensions` and
+imports cleanly.
+
+## References
+
+- `planning/changes/2026-07-19.03-core-zero-dep-typing-extensions.md`

pyproject.toml

@@ -20,7 +20,12 @@ classifiers = [
     "Topic :: Software Development :: Libraries",
 ]
 version = "0"
-dependencies = []
+dependencies = [
+    # Runtime use: `typing_extensions.Self` (base.py) and `typing_extensions.TypedDict`
+    # (healthchecks) — the latter is required by pydantic/FastAPI on Python < 3.12
+    # (`typing.TypedDict` is rejected there). Pure Python, so ft-friendly.
+    "typing-extensions",
+]
 
 [project.urls]
 Homepage = "https://lite-bootstrap.modern-python.org"