Changelog

/changelog

Usage

/changelog              # Summarize the last upgrade's changelog slice
/changelog --full       # Show the raw CHANGELOG slice without summarization
/changelog <version>    # Show a specific version's section (e.g. /changelog 2.1.99)

Description

Replays the Claude Code CHANGELOG entries captured the last time the CLI was upgraded, so the user can revisit "what's new" on demand. Complementary to the SessionStart version-check hook: the hook shows the greeting once at startup, this skill lets the user ask for it again at any point in the session.

Behavior

Default (/changelog)

1. Read the persisted slice at $HOME/.claude/cache/last_upgrade.md. This file is written by ~/.claude/session_start_version_check.sh whenever a real upgrade is detected. Format:

   ---
   from: <prev version>
   to: <current version>
   detected_at: <timestamp>
   ---
   
   ## <current version>
   ... raw CHANGELOG entries ...
   

2. If the file exists, parse the YAML header (from, to, detected_at) and the body (the raw changelog slice), then present:

   • A one-line header: Claude Code <from> → <to> (upgraded <detected_at>)
   • A themed summary: Features, Improvements, Fixes. 5–8 bullets total. Prioritize user-facing changes over internal fixes — match the style the session-start greeting uses.
   • A one-line footer: Reply '/changelog --full' to see the raw entries.

3. If the file does NOT exist, no upgrade has been observed on this machine since the hook was installed. Report that plainly. Do not fabricate entries. Offer: "Run claude --version and I can look up that version's changelog section directly if you'd like."

--full mode

Print the raw body of $HOME/.claude/cache/last_upgrade.md verbatim (strip the YAML header, keep the changelog markdown). No summarization. Useful when the user wants to see every bullet.

Specific version (/changelog 2.1.99)

1. Skip last_upgrade.md entirely.
2. Read the cached full changelog at $HOME/.claude/cache/claude-code-changelog.md (maintained by the hook).
3. Do not fetch. This skill is read-only with respect to the cache — the hook owns network I/O so TLS hardening, sanity checks, and error handling live in one place. If the cache file does not exist, tell the user: "The cached CHANGELOG is missing. Start a new Claude Code session to refresh it — the SessionStart hook will refetch — then re-run /changelog <version>." Do not run curl. The hook refreshes the cache on session start when the file is more than 24h old, so "start a new session" is the user-visible refresh mechanism. The skill itself has no way to inspect the cache's age (Read gives contents, not mtime), so it must not make freshness claims.
4. Extract the section for the requested version. Scan ## headings and pull the first semver found in each (so ## 2.1.99, ## [2.1.99], and ## 2.1.99 (2026-04-10) all match version 2.1.99 — matching the hook's own slicer). Take everything from the matching heading up to the next ## heading and summarize it with the same Features/Improvements/Fixes structure as the default mode.
5. If the requested version is not present in the CHANGELOG, say so — do not invent content.

Implementation notes for the model

• Use the Read tool for ~/.claude/cache/last_upgrade.md and ~/.claude/cache/claude-code-changelog.md. Both are plain text.
• Never run curl or any other network fetch from this skill. The SessionStart version-check hook owns the cache and all network I/O — TLS hardening, timeouts, content sanity checks, and error logging all live there. Duplicating fetch logic here would drift from the hook's hardening and split the attack surface across two places.
• Never write to ~/.claude/cache/last_upgrade.md or ~/.claude/cache/claude-code-changelog.md. This skill is strictly read-only with respect to hook state. The hook owns those files.
• When summarizing, group bullets by theme and cap at 8 bullets. If the slice contains many fixes, collapse similar ones into a single bullet (e.g. "Several /resume picker fixes" rather than listing each).
• Be faithful: only summarize entries that appear in the source. Do not extrapolate from version numbers.

Expected Output

Default mode — slice exists

User: /changelog

Claude Code 2.1.100 → 2.1.101 (upgraded 2026-04-10 09:14:22 -0700)

Features
  - /team-onboarding generates a teammate ramp-up guide from local usage
  - OS CA certificate store trusted by default for enterprise TLS proxies

Improvements
  - Tool-not-available, rate-limit, and refusal errors now explain what
    happened and how to proceed
  - /context free-space accounting now matches the header percentage

Fixes
  - --resume/--continue no longer loses context on large sessions
  - Hardcoded 5-minute request timeout removed; API_TIMEOUT_MS is honored
  - permissions.deny now overrides PreToolUse hook "ask" decisions (security)

Reply '/changelog --full' to see the raw entries.

Default mode — no upgrade recorded yet

User: /changelog

No upgrade has been recorded on this machine yet. The session-start
version-check hook writes ~/.claude/cache/last_upgrade.md the first time
it sees a version change after install.

If you want a specific version's changelog, try /changelog <version>
(e.g. /changelog 2.1.101).

Specific version mode

User: /changelog 2.1.99

Claude Code 2.1.99 (from cached CHANGELOG)

Features
  - ...

(summarized from anthropics/claude-code CHANGELOG.md)

Notes

• The cache and slice files live under ~/.claude/cache/ and are owned by session_start_version_check.sh.
• Slice is updated only when the hook detects a true upgrade (not on downgrades, not on equal-version boots).
• This skill does no network work on the default path — it is safe to run offline as long as an upgrade has been observed at least once.