[Kludex]

FormParser kept the spaces and tabs around a part header value, so Content-Transfer-Encoding: base64 (trailing space) or Content-Transfer-Encoding: base64 (tab) was treated as an unknown encoding, and the field was delivered still encoded.

from python_multipart import FormParser

body = (
    b"--b\r\n"
    b'Content-Disposition: form-data; name="f"\r\n'
    b"Content-Transfer-Encoding: base64 \r\n"
    b"\r\n"
    b"aGVsbG8=\r\n"
    b"--b--\r\n"
)
fields = []
parser = FormParser("multipart/form-data", lambda f: fields.append(f.value), None, boundary=b"b")
parser.write(body)
parser.finalize()
print(fields)  # before: [b'aGVsbG8='], after: [b'hello']

RFC 9110 §5.5 excludes leading and trailing whitespace from a field value. Only spaces and tabs are stripped, matching #364. The low-level MultipartParser callbacks still receive the raw bytes.

Session: pi --session 01a1cc04-bb37-7152-92e5-03b3625b499e

[chatgpt-codex-connector]

Codex Review Summary: ✅ Completed

This comment shows the latest Codex review activity on this pull request.

Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-11-11T20:23:59.232925Z	0eae2c0	PR opened

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[cubic-dev-ai]

No issues found across 3 files

_{View guided diff | Re-trigger cubic}

[codspeed]

Merging this PR will not alter performance

✅ 5 untouched benchmarks

---

_{Comparing strip-part-header-whitespace (c9ea84a) with main (6cebfd8)}