Wave A PR 3: typed errors + 401/429 escalation + body-size + key validation

.github/workflows/ci.yml

@@ -0,0 +1,30 @@
+name: CI
+
+on:
+  pull_request:
+  push:
+    branches: [main]
+
+jobs:
+  check:
+    runs-on: ubuntu-latest
+    strategy:
+      fail-fast: false
+      matrix:
+        python-version: ["3.9", "3.10", "3.11", "3.12"]
+    steps:
+      - uses: actions/checkout@v4
+      - name: Set up Python ${{ matrix.python-version }}
+        uses: actions/setup-python@v5
+        with:
+          python-version: ${{ matrix.python-version }}
+      - name: Install
+        run: |
+          python -m pip install --upgrade pip
+          pip install -e ".[dev,all]"
+      - name: Ruff
+        run: ruff check recost/ tests/
+      - name: Mypy
+        run: mypy recost/
+      - name: Pytest
+        run: pytest -v

README.md

@@ -182,7 +182,8 @@ Unrecognized hosts still appear in telemetry, grouped under `"unknown"`.
 - Request timestamp, method, URL (query params stripped), host, path
 - Response status code
 - Round-trip latency (ms)
-- Request and response body size (bytes)
+- Request body size (bytes) — measured for JSON, form, bytes, and string payloads. Streaming uploads (async iterators, generators) are reported as 0 to avoid buffering large bodies.
+- Response body size (bytes) — derived from the `Content-Length` response header. HTTP chunked and SSE streams do not set this header and will report 0.
 - Matched provider, endpoint category, and estimated cost
 
 **Never captured:**