CC Update — start from the canonical source, don't rediscover

Genesis's Claude Code update process is fully standardized. This skill exists so a session executes that process instead of re-deriving it (grep archaeology every time). If you find yourself hunting for where the pin lives or how the host updates, STOP and read the doc.

Authoritative source — read these FIRST

• docs/reference/cc-compatibility.md → §Updating Claude Code (host + container) (the exact steps) and §CC Update Evaluation Checklist (the 8-lens impact eval).
• The pin is the single source of truth: CC_VERSION (+ NODE_MAJOR) in scripts/lib/cc_version.sh.

The process in one breath — step numbers MATCH §Updating Claude Code in the doc

Deliberately the same numbering in both files: "step 4" means the same thing in each. The doc is authoritative for detail; this is the one-breath version. If a number here disagrees with the doc, the doc wins — and that disagreement is a bug worth fixing rather than working around.

Pick the target before anything else. npm view @anthropic-ai/claude-code version gives latest; use an explicit older version if you are deliberately not chasing latest. Every step below is defined over (pinned, target], so nothing can begin until target is fixed — and re-picking it later restarts the procedure (step 5).

⛔ GATE — FULL CHANGELOG READ. MANDATORY, NO EXCEPTIONS. (part of step 1, before any triage)

Read EVERY release entry in (pinned, target] IN FULL before step 1's triage. No pin bump proceeds without this.

Fetch it fresh — nothing in Genesis maintains a changelog cache: curl -fsSL https://raw.githubusercontent.com/anthropics/claude-code/main/CHANGELOG.md -o ~/tmp/cc_changelog.md (mkdir -p ~/tmp first — curl -f will not create it.) That path is a scratch copy, NOT a recon-pulled cache. Before reading, confirm the file CONTAINS a ## <target> heading (grep -c '^## <target>$') — a stale copy fails exactly that, which is how it would otherwise pass unnoticed while the whole new range goes unread. Do NOT also require the FIRST heading to equal the target: under the mid-soak rule you may deliberately finish on a target latest has already passed, and equality could never be satisfied by any re-fetch.

If the target released hours ago its heading may not be in main's CHANGELOG.md yet — the one case no re-fetch fixes. Cover the tail from the GitHub release bodies, but enumerate what is missing first: gh release view reads ONE release, so gh release view v<target> alone under-reads whenever more than one release in (pinned, target] is absent, and the gate closes over releases nobody read. gh release list --repo anthropics/claude-code --limit 60 --json tagName -q '.[].tagName', keep the tags in range with no ## <version> heading in the file, then gh release view <tag> for EACH. Say in the durable row which source covered which releases.

Scale: (2.1.218, 2.1.246] measured 25 releases / ~88KB. The load-bearing item can sit anywhere, including deep inside the newest release.

The analyzer is a TRIAGE SUMMARY, never a substitute. It prioritises; it does not discharge the gate.

Record it as a DURABLE row, not a chat line — opened BEFORE, closed AFTER. session_ledger_add always creates an open row, and its own return message says it "will re-inject into every post-compaction window until closed" (session_charter_tools.py::_impl_session_ledger_add). So a row added after declaring the gate done is a permanent false open item in charter counts, compaction injections and repo-pulse matching. Open it, do the read, then close it:

resp = session_ledger_add(session_id=<this session>,
                          text="CC changelog gate: reading (2.1.X, 2.1.Y] from <source>")
# resp is a DICT — the id is resp["id"], not resp itself.
# session_id is required, but a missing one returns {"error": …} rather than raising:
# CHECK the response, or you will proceed believing a row exists that does not.
…the read…
session_ledger_update(item_id=resp["id"], status="done",
                      evidence="read in full from <source>, <date>; <N> releases covered")

The row is session-scoped, so across a 2–3 day soak the session that opens the PR is not the one that ran the gate. What makes the gate checkable later is the carry-over: a CC-Gate-Changelog: trailer in the PR body plus the §Version History clause — see §Gate receipts in docs/reference/cc-compatibility.md for both receipts and what their absence means. The pin-receipt check blocks a pin-forward PR that is missing either — at MERGE time, where the body that actually merges is the one read. The cc-pin-receipts CI job runs the same checker advisorily and never fails a build. For rows added from 2026-08-26 onward, a Version-History row with no "changelog read" clause means the gate was not run — treat that as blocking at merge.

Delegation is allowed — with the SAME context and rigor, never a naive "summarize this." Brief the sub-agent with §Delegating the full changelog read below, then adversarially spot-check its load-bearing findings against ground truth. A delegated review is not a rubber-stamp.

Origin (2026-08-26). A session re-targeted 245→246 off the headline delta and let the changelog-reading analyzer stand in for actually reading the changelog. The cause was mechanical, not just human: on main the analyzer fetches only the newest 5 GitHub releases, keeps just the new version's body, and truncates it at 1000 chars — v2.1.246's body is ~9.3KB, so it saw the first ~8 of ~60 bullets and structurally could not surface the rest. The later full read found real Genesis-relevant 246 items the triage had missed: subagent maxTurns now returning partial output, -p --continue/--resume plan-mode resume, and a --strict-mcp-config startup-hang fix that lands directly on Guardian Diagnosis.

1. Evaluate — intake, the ⛔ GATE above, then triage. Intake, never from scratch: memory_recall + docs/reference/cc-compatibility.md §Known Issues / §Version History + npm view @anthropic-ai/claude-code@<target> engines.node + a quick community sweep (Reddit/forums) for regressions the changelog omits. Triage: recon_cc_update_check(old, new) MCP (backed by src/genesis/recon/cc_update_analyzer.py). Know its real coverage: today it fetches only the newest 5 GitHub releases, matches the target version's tag, and truncates that body at 1000 chars — so on a multi-release jump it sees a fraction of ONE release, or NOTHING at all once the TARGET's own tag ages out of the newest 5. That is likely mid-soak: step 5 holds a candidate for 2-3 days while CC ships ~daily. When that happens the LLM is never called at all — _fetch_changelog returns "", and analyze gates the LLM path on if self._router and changelog, so it falls through to a hand-built dict with details="Changelog not available". The confident-looking informational verdict in that case is a deterministic fallback, not a judgement — do not read it as "the analyzer looked and found nothing". Two traps in reading that verdict. (a) _fetch_changelog returns "" from five distinct paths — a non-zero gh exit, a timeout, a bare except, a non-list payload, and the tag-not-in-newest-5 case. An expired gh auth produces a byte-identical details="Changelog not available", so confirm gh auth status before concluding the tag aged out. (b) There is a SECOND non-judgement path: when the LLM was called and failed, the keyword heuristic also returns informational with real changelog text. Tell them apart by the " (LLM analysis unavailable)" suffix on summary — without that suffix and with a non-empty details, the verdict is a genuine LLM read. (A whole-(old, new] map-reduce rewrite exists on an unmerged branch — unmerged as of 2026-08-26; grep the file before relying on it. It would still omit the oldest chunks on a very large range, so the GATE does not retire either way.) Triage every hooks / MCP / CLI-flag / subagent / permissions delta. Rule: a changelog claim that "we depend on X" only gates the bump if verified against LIVE usage — the TodoWrite lesson: a removed feature Genesis measured 0 uses of is hygiene, not a blocker.

   • Take the PRE-align model-alias sample HERE, in step 1. It belongs to the first never skippable step, not to step 2 — step 2 has a legitimate skip condition, and a sample nested under it silently disappears exactly when that skip fires, leaving the step-4 "after" reading with nothing to compare against. It cannot move later either: step 3 replaces the CLI, so this is the last point at which the old binary is still installed. See §Model-alias drift below for the invocation; the post-align half is step 4.

2. Deploy current main FIRST — scripts/update.sh as a background task, BEFORE aligning the candidate, so the soak runs on current code. Otherwise step 8 lands accumulated Genesis change AND the CC bump together and you cannot attribute a regression to either. Checkable skip condition — three parts, all required: git fetch origin first (an unfetched origin/main is stale and produces a false "already current"); take the newest update_history_recent row whose status == "success" — the tool deliberately returns every attempt including failure and rolled_back (update_history.py:98-113), and a failed attempt's later timestamp otherwise reads as evidence of a deployment that never happened; then confirm that row's new_commit is an ancestor-or-equal of the fetched origin/main head — mechanically, git merge-base --is-ancestor "$(git rev-parse origin/main)" <new_commit> exits 0. Skip only if all three hold.

3. Align the CONTAINER ONLY to the candidate.

   source scripts/lib/cc_version.sh   # NOTE: this sets CC_VERSION to the repo PIN
   CC_VERSION=<candidate>             # standalone assignment, AFTER the source
   cc_ensure_local
   cc_shadow_scan
   

   ⚠️ Never write CC_VERSION=<candidate> cc_ensure_local and then a bare cc_shadow_scan. An assignment prefix on a function call does not persist past that call, so the scan would run on the OLD pin while the container is on the candidate — and if any copy sits at the old pin it crowns that one canonical and deletes the freshly-installed candidate (cc_version.sh:251). Full rationale: doc §Updating step 3. claude --version is NOT sufficient here: it spawns a fresh child, which reads the new on-disk binary and truthfully reports the candidate while the session asking the question is still executing the old one. Run scripts/check_cc_running_versions.sh instead — it compares each live process's actual mapped binary against the one on disk. Check the Node floor first — npm view @anthropic-ai/claude-code@<candidate> engines.node vs node -v. If it rises above the container's Node, STOP: no container-side Node transition tool exists today (install.sh:473-477 hardcodes >= 20 and never reads NODE_MAJOR), and a failed align is not a clean no-op — npm install -g has already replaced the working CC before the verify runs.

4. Validate the CANDIDATE against candidate-shaped expectations, not step 9's. During the soak the correct state is container == candidate, host == old pin — step 9 requires BOTH to equal the pin, which cannot hold yet. Run the critical paths, the doc's §Known Issues, and each behavior the impact eval flagged; any Guardian-path check exercises the host's old binary, so candidate-specific Guardian behavior needs a container-side exercise.

   • Run scripts/check_cc_running_versions.sh BEFORE validating, not just before the soak. Same trap as step 3 and step 5: validation performed inside a session still mapped to the replaced binary is evidence about the OLD release, and it is the evidence the whole changelog gate feeds into. The check belongs at every point that produces evidence about the candidate — steps 3, 4, 5 and 9 — not only at the soak boundary.
   • Take the POST-align model-alias sample here and compare it against the pre-align one from step 2 — nothing else in the system will catch an alias remap. See §Model-alias drift below for the invocation and for which modelUsage entry to read (it is not the first one).

5. Soak 2–3 days under real use — but the clock does not start until every interactive session is actually ON the candidate. A long-running CC process keeps its original binary mapping until it restarts; npm replaces the package underneath it. So relaunch the foreground sessions, then prove it rather than assuming it:

   scripts/check_cc_running_versions.sh    # exit 0 required before the clock starts
   

   Re-run it at soak END too — sessions started mid-soak are fine, but one that predates the align and was never relaunched has been contributing evidence about the OLD release the whole time. Origin (measured on a live install): a soak was declared started and ran its full length with a majority of live CC processes — and most interactive sessions — still executing the replaced predecessor. cc_shadow_scan was clean throughout (it scans on-disk copies, not running processes) and claude --version reported the candidate the whole time, because it spawns a fresh child. Nothing in the procedure would have caught it.

   Rollback is one command: source scripts/lib/cc_version.sh && CC_VERSION=<pin> cc_ensure_local. Do NOT run update.sh during the soak — it unsets any inherited CC_VERSION and re-aligns the container to the pin, reverting the candidate. Proceed to the public pin only after soak + explicit user sign-off.

   • Mid-soak drift (CC ships ~daily, so latest WILL move during the soak): re-target to a newer release mid-cycle ONLY if it fixes something touching our workflow / soak safety / a known issue (e.g. 2.1.245→246 fixed a background-retention sweep that reaped user-created .claude/worktrees/). Otherwise finish the soak on the pinned target and roll the delta into the next cycle — never silently chase-latest.
   • A re-target RESTARTS the procedure from step 1. New target ⇒ the durable changelog-gate row no longer covers the range, the candidate validation ran against a different binary, and the 2–3 day clock resets. Otherwise you publish a target with hours of real use — defeating the gate exactly for the workflow-affecting releases that justify re-targeting.

6. Bump the pin — CC_VERSION in scripts/lib/cc_version.sh; bump NODE_MAJOR in the same file only if the new CC raises its engines.node floor (the cc-node-lockstep CI job, scripts/check_cc_node_lockstep.py, fails the PR otherwise). In the same PR update docs/reference/cc-compatibility.md: §Current CC Version, a §Version History row carrying the changelog-gate clause from step 1, and any new caveats.

7. PR → CI green (incl. cc-node-lockstep) → privacy scan → explicit user approval → squash-merge. Then git pull --rebase origin main. Both gate receipts go in the PR body as trailers — the merge gate blocks a pin-forward PR without them (a pin that moves backward is exempt; rollback is the incident-recovery path):

   CC-Gate-Changelog: read (2.1.X, 2.1.Y] in full from <source>, <date>
   CC-Gate-Soak: <candidate> on container <start>..<end>, check_cc_running_versions.sh clean, sign-off recorded
   

8. Host-Deploy Gate — in the SAME session after merge, run scripts/update.sh from ~/genesis as a background task (deploys exceed the Bash tool timeout): it aligns the container (cc_ensure_local) AND the host VM (guardian update-cc op) to the pin, idempotently. Note the nightly genesis-cc-align.timer is host-only — cc_align_host.sh calls cc_align_host_sync and never cc_ensure_local, so it closes HOST drift between updates and (usefully) will not silently revert a container candidate mid-soak.

9. Post-deploy validation (SAME session) — critical paths AND known/tabled issues, not just a smoke. Container + host claude --version == pin (host via the gateway version op / a FRESH gateway version op — not ~/.genesis/host_gateway_state.json, which is written from the PRE-alignment probe and not refreshed after update-cc, so it reports the OLD version until the nightly timer runs); guardian tick healthy; a CCInvoker / headless claude -p smoke on a FRESH process (this foreground session keeps its OLD binary until relaunch); re-check the doc's §Known Issues + any tabled CC bugs against the new version; and verify each behavior the impact eval flagged (e.g. an MCP arg-typing or -p result-shape change) on the live path, not just that the flag still parses.

10. Leverage + capture — for each newly-available capability Genesis would want, file the detection→behavior follow-up (below). Store what was learned to memory + this doc + the KB so the next update stays execute-not-rediscover.

Delegating the full changelog read (the GATE — part of step 1)

You may hand the read to a sub-agent — but it must be done with the same context and scrutiny you would apply yourself. A generic "read this changelog and tell me what you think" is NOT the gate: the agent lacks the Genesis impact surfaces, so it returns feature summaries instead of consequences. Brief it with THIS (adapt the range/source):

FIRST confirm ~/tmp/cc_changelog.md CONTAINS a ## <target> heading; if it does not, re-fetch before reading (mkdir -p ~/tmp first): curl -fsSL https://raw.githubusercontent.com/anthropics/claude-code/main/CHANGELOG.md -o ~/tmp/cc_changelog.md (nothing maintains that file — a stale copy makes this whole review vacuous).

Read EVERY release entry in (<pinned>, <target>] IN FULL. Do NOT summarize generically, and do NOT treat the newest release as already-known — the load-bearing item can sit anywhere, including deep inside the newest release (that is exactly what the last miss looked like). For each release, judge every entry against these Genesis impact surfaces and report only entries with a concrete Genesis consequence, tagged RISK (could break us) / GAIN (fixes something we hit) / LEVERAGE (new capability we'd want):

• Hooks — PreToolUse approval gate, bash_safety_hook, review-enforcement hooks; exit-code-2 blocking semantics, additionalContext, matcher parsing (Genesis uses matcher only — no if conditions); and the hook INPUT PAYLOAD SHAPE — a renamed/removed field silently disables every guard (see tests/test_scripts/test_hook_input_contract.py).
• MCP — our servers under claude -p --mcp-config; arg typing (incl. empty-{} schemas), connect/reconnect, interrupted-call reporting, tool-search/deferred tools.
• claude -p / CCInvoker — output/result JSON shape, modelUsage, resume/continue, mid-stream error handling, stdin/stdout.
• Flags Genesis actually passes — -p, --output-format json, --model, --effort, --append-system-prompt, --mcp-config, --strict-mcp-config, --allowedTools, --disallowedTools, --bare, --max-turns, --resume, --dangerously-skip-permissions (full table: docs/reference/cc-compatibility.md §Integration Surface).
• Guardian host recovery — the host VM's diagnosis call: a DIFFERENT machine, and the highest-stakes CC call in the system. Actual shape (src/genesis/guardian/diagnosis.py:546-555): claude -p --model <cfg> --output-format json [--effort <cfg>] --max-turns <cfg> --dangerously-skip-permissions, plus --mcp-config <path> --strict-mcp-config only when config/no_mcp.json exists (otherwise it logs a warning and runs without them). Defaults: model opus, effort high, max-turns 50. So a change to --effort semantics, or to --mcp-config/--strict-mcp-config handling, lands squarely on this call.
• Subagents / workflows — spawn depth defaults, fork/background defaults, maxTurns behavior, concurrency caps.
• Skills / slash commands / plugins — auto-invocation changes, skill discovery + frontmatter, plugin loading (2.1.215 removed CC's proactive /code-review + /verify, making Genesis's own review-enforcement hooks the primary trigger rather than a backstop).
• Permissions / auto mode / Monitor — anything changing what is auto-approved.
• Worktrees — an active install can carry dozens; isolation, retention sweeps, --worktree.
• Cross-session — SendMessage/ListAgents, sockets in rootless containers.
• Security — credential handling, permission-bypass fixes, sandbox/redaction.
• Model / routing — alias→model drift, family step-down, pricing/limits. Include the release number for every finding. Flag anything you are unsure about rather than dropping it.

Coverage receipt (required, not optional). End your report with one line per release in the range, in order — 2.1.NNN: <finding tag(s)> or 2.1.NNN: nothing relevant — so every release is explicitly accounted for. Do not pad findings, but do not omit a release from this list either: a missing line reads as "never read", not as "nothing to say". If you run short on turns or budget, STOP and say exactly which releases you did not reach rather than returning a report that looks complete — partial output no longer fails on its own, so an unflagged early stop is invisible to the person reading you.

Then verify before you trust it: independently re-derive the load-bearing findings (the ones that would gate the bump or change our code) from the changelog text and the actual Genesis code — refute-by-default, per the "verify multi-agent output" rule. The delegation saves you reading time, not judgment.

And verify COVERAGE separately from accuracy — they fail differently. Re-deriving the findings the agent returned can only catch findings that are wrong; it cannot detect releases the agent never opened. From CC 2.1.246 onward — which the pin now is, though an install may be running something else, so check what the delegating session is ACTUALLY on rather than assuming the pin — a subagent that hits maxTurns returns partial output without failing, so a silent stop two-thirds through the range is indistinguishable from a genuinely short report. Close that by construction: enumerate every ## release heading in (pinned, target] yourself (grep -n '^## ' ~/tmp/cc_changelog.md), and require the agent to acknowledge each release explicitly — including the ones it judged irrelevant. Reconcile the two lists before marking the gate done. Any release without an acknowledgement means the gate is not done, no matter how good the returned findings look. Ask for the per-release acknowledgement in the brief, not afterwards — a re-ask cannot recover context the agent already dropped.

Model-alias drift — CHECK IT BY HAND, nothing watches it

--model opus (and every alias) silently re-points to a new full model id when Anthropic bumps the family — measured live: opus resolved claude-opus-4-8 → claude-opus-5 across a CC bump, with no warning anywhere. This is NOT a downgrade, so the tier-based downgrade detector is blind to it, and no drift detector exists on main today — there is nothing to alert you.