[Silthus]

Problem

PostHog/context-mill#433 adds a send-transactional-email skill. Every consumer overlays context-mill on top of this repo's skills, so a posthog skill or a store skill with that name would be silently overwritten or would shadow it. The skills store list had also drifted: it never reserved instrument-metrics, which the build list already holds.

Tracking: Silthus/posthog#476.

Note

🔵 Merge risk: low · two-way door (merge-risk rubric)

• The skills store now refuses send-transactional-email and instrument-metrics as store skill names, and hogli lint:skills refuses the first under products/*/skills/. No skill in the tree uses either name.
• A revert restores the old lists.

Changes

• hogli lint:skills fails on a product skill named send-transactional-email (reserved_names.py).
• The skills store refuses send-transactional-email and instrument-metrics (bundled_skills.py).
• The writing-skills skill, its handbook page, and the feature flags skills README list the new context-mill skill.

How did you test this code?

A scratch product skill named send-transactional-email, asked of both guards, before and after:

Check	upstream/master	This branch
hogli lint:skills	OK: 164 product skill(s) ... passed	ERROR: 'send-transactional-email' is owned by PostHog/context-mill ...
'send-transactional-email' in bundled_skill_names()	False	True
'instrument-metrics' in bundled_skill_names()	False	True

products/posthog_ai/scripts/test/test_build_skills.py and products/skills/backend/test_bundled_skills.py pass. The pre-push hogli ci:preflight --strict passed with 0 failures.

Test rationale: no new test. A membership assertion would restate the constant. The guards themselves are covered by test_lint_all_catches_reserved_name_in_frontmatter and test_bundled_skill_names_holds_the_tree_and_the_omnibus_names. A test that the two lists match would catch the next drift, but it would import across the isolated products.skills boundary.

Release status

• No feature flag controls this change

Docs update

The writing-skills handbook page and skill list the new name.

🤖 Agent context

Autonomy: Human-driven (agent-assisted)

Agent: Claude Code, Claude Opus 5.5

• Part of the code-managed email templates work tracked in Silthus/posthog#461. Skills used: /writing-skills, /writing-pr-descriptions.
• Reviewed together with context-mill#433 by a fresh Opus 5.5 reviewer at high effort: one finding here (a stale README count), fixed, and one rejected (the list-equality test, for the product boundary above).
• No duplicate: no open PR reserves this name.
• Public artifact: nothing in this PR comes from outside this repository and the linked public issues.

🤖 Generated with Claude Code

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