A real-source editorial exercise

What changes when a TOML reader moves from Python 3.11 to 3.14?

Two pinned documentation versions answer some of the question. A local runtime probe answers a narrower part. Neither proves that an application has migrated successfully—and a citation that matches can still contradict the claim above it.

What was actually done

The agent retrieved CPython’s Doc/library/tomllib.rst at release-tag commits for 3.11.0 and 3.14.0, kept the exact raw files and full license notices, then ran a small local probe on CPython 3.14.4. The six claims and their judgments were authored by the same agent. They are editorial demonstrations, not six independent model samples or a prompt benchmark. No application was migrated.

All six claims have exact quote matches. Five are included in the brief. The sixth claims that tomllib can write TOML while citing “does not support writing TOML.” It is deliberately wrong and is explicitly rejected. 6/6 quote-matched is not 6/6 supported.

The first five claims cover binary file input, Decimal hooks, new documented exception fields/deprecation, read-only scope and one narrow runtime observation. Three questions preserve missing application-specific evidence. The reviewed artifact retains the rejected claim in its appendix, rather than quietly deleting it from the evidence.

Try the actual workflow

Open Source Brief and choose “Load Python documentation example.” No claim starts approved.
Preview all claims. For C1 and C2, follow both source links and check that the statements are shared by the two versions.
For C3, inspect the explicit 3.14 version-change directive; do not infer every older runtime behavior from omitted documentation.
For C5, read S3’s runtime and scope as well as the Decimal result. It is not a 3.11 runtime test.
Reject C6 despite its exact match. Approve only claims you judge supported. Add your own notes.
Download HTML or Markdown. Read the questions, excluded-claim appendix and source/rights register as a recipient. Save work JSON separately; reopening clears every approval.

Change a source or claim and preview again: decisions clear rather than silently applying to changed evidence. This is a current working copy, not a signed audit log. Retain previous downloads if you need earlier context.

Local runtime observation, not a migration guarantee

The probe used BytesIO/StringIO and tiny authored TOML strings. Binary input parsed, a text stream raised TypeError, Decimal retained 1.20, a list-returning float hook raised ValueError, and an invalid value exposed the documented error attributes. hasattr(tomllib, 'dumps') was false. The recorded timestamp belongs to that run; rebuilding this page does not rerun it.

{
  "observed_at": "2026-11-04T10:04:55.325813+00:00",
  "runtime": "CPython 3.14.4",
  "scope": "One local Python runtime. No Python 3.11 run, performance measurement, cross-version guarantee, real configuration migration or third-party writer test.",
  "results": {
    "binary_load": {
      "amount": 1.2
    },
    "decimal_loads": {
      "type": "Decimal",
      "value": "1.20"
    },
    "text_stream": {
      "exception": "TypeError",
      "message": "File must be opened in binary mode, e.g. use `open('foo.toml', 'rb')`"
    },
    "list_parse_float": {
      "exception": "ValueError",
      "message": "parse_float must not return dicts or lists"
    },
    "invalid_toml": {
      "exception": "TOMLDecodeError",
      "message": "Invalid value (at line 1, column 10)",
      "attributes": {
        "msg": "Invalid value",
        "doc": "amount = ]",
        "pos": 9,
        "lineno": 1,
        "colno": 10
      }
    },
    "has_dumps": false
  }
}

Exact observation JSON · Runnable probe source. No older interpreter, alternate implementation, benchmark, third-party writer or real configuration corpus was tested. Do not install or migrate based only on this brief.

Portable files and provenance

Editable source/answer work JSON (no approvals)
Script-free offline reviewed HTML · Reviewed Markdown
Exact generated prompt · Authored raw answer (not a model completion)
Commit-pinned retrieval and source hashes · Authorship, decisions and artifact hashes

Original documents and permission

Python software and documentation are licensed under the Python Software Foundation License Version 2. Copyright (c) 2001 Python Software Foundation; All Rights Reserved. Raw RST files are unchanged. This derivative reading aid adds selected quotations and agent-authored interpretation; it does not modify Python. No PSF endorsement. Complete source-release licenses are retained below and within the work/brief rights fields.

You may use, copy, modify and redistribute the agent-authored prompt, probe and editorial additions, including commercially, without attribution or warranty. This permission does not replace the Python source licenses and does not establish rights in documents you supply.