Myco v0.5.1 — 永恒进化 delivered in code (MAJOR 6–10)

Release-metadata note: the myco-0.5.0 wheel filename was burned on a prior upload to PyPI and cannot be reused per the index's filename-reuse policy. v0.5.1 is the first MINOR-release wheel on PyPI carrying the full v0.5 content below; no code or doctrine delta vs what would have been v0.5.0.

TL;DR: the README's two load-bearing "the substrate changes shape with the work" claims (L0 principle 3) and "you never migrate again" stop being aspirational. Every MAJOR gap the v0.4.1 post-release audit identified is closed in one release.

What's new

Governance verbs (MAJOR 9 + 10)

Four new agent-callable verbs under myco <verb>:

• myco craft --topic "<phrase>" — scaffold a dated three-round primordia doc (docs/primordia/<slug>_craft_<date>.md) with YAML frontmatter + Round 1 — 主张 / Round 2 — 修正 / Round 3 — 反思 skeleton.
• myco bump --contract v0.5.1 — atomic contract-version bump. Regex-patches _canon.yaml, re-validates via load_canon, prepends a new section to docs/contract_changelog.md. --dry-run previews. Restores canon on any post-write parse error.
• myco evolve --proposal <path> — shape validator for craft/proposal docs (five gates: frontmatter type, title, body size, round-marker count, per-round floor).
• myco scaffold --verb <name> — auto-generate a handler stub for any verb already in the manifest. Derives path from the manifest's handler: string. Stub is a well-formed Result handler that emits DeprecationWarning on invocation so unfinished verbs are neither silent successes nor crashes.

Plug-in dimensions (MAJOR 6)

Lint dimensions now register via [project.entry-points."myco.dimensions"] in pyproject.toml. Third-party substrates can ship their own dimensions without forking Myco — just declare the entry-points group in their own pyproject.toml. The _BUILT_IN tuple is now only a dev-checkout fallback.

• myco immune --list enumerates every registered dimension (id, category, default severity, summary).
• myco immune --explain <dim> prints the dimension's full prose description.

Forward-compatible canon (MAJOR 8)

An unknown _canon.yaml::schema_version now emits UserWarning and proceeds best-effort instead of raising CanonSchemaError. A new myco.core.canon.schema_upgraders: dict[str, Callable] registry is the forward-compat seam — empty at v0.5, populated when schema v2 lands. This is the single code-level change that makes "you never migrate again" tenable rather than marketing copy.

New MF1 dimension + meta/ package (MAJOR 7 + 10)

• MF1 (mechanical / HIGH): every canon.subsystems.<name>.package path must resolve to an existing directory under substrate root.
• src/myco/meta.py → src/myco/meta/ package with submodules for every governance verb. from myco.meta import session_end_run still works (backward-compat re-export).

Inventory counts

• Sixteen verbs (was twelve): added craft, bump, evolve, scaffold.
• Nine lint dimensions (was eight): added MF1.
• 465 tests pass on the full suite.

Upgrade path

• From v0.4.x — no action required for existing substrates. _canon.yaml files emitted by v0.4.x kernels parse under v0.5 unchanged. The one user-visible move: session-end's manifest handler string changed (the re-export in meta/__init__.py handles any code that pinned the old path).

pip install --upgrade 'myco[mcp]'

Doctrine records

• Governing three-round craft: docs/primordia/v0_5_0_major_6_10_craft_2026-04-17.md
• Contract change record: docs/contract_changelog.md v0.5.1 section
• Updated L1/L2/L3 doctrine: canon_schema.md rule 4, homeostasis.md entry-points/MF1/--list, command_manifest.md governance-verbs section, package_map.md meta/ as a package

Full details in CHANGELOG.md.