docs(plan): Phase 9, Handover 4 and CLAUDE.md name rule A, with door lines

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

commands/trekplan.md

@@ -921,10 +921,34 @@ approval.
 
 Phase 9 is a loop of at most **3 critic rounds**. Each round reviews the plan
 as it stands, and a command — not this session's judgment — records the
-verdict and decides whether the plan may go on. The loop ends on a round with
-no BLOCKER; after round 3 with a BLOCKER still open it stops and asks the
+verdict and decides whether the plan may go on. A BLOCKER or an open MAJOR
+stops the plan: revise and run the next round. The loop is done on a round
+that leaves neither, or when the operator accepts the open MAJORs after the
+last round; after round 3 with a BLOCKER still open it stops and asks the
 operator. It never goes on silently.
 
+**From round 2.** Round 1 is unchanged: the reviewers read the whole plan.
+From round 2 on, first print what changed since the text the last round
+reviewed:
+
+```bash
+node ${CLAUDE_PLUGIN_ROOT}/lib/validators/plan-gate.mjs --diff "{plan_path}"
+```
+
+It prints `diff-base: <sha256> (round N)` and each changed hunk with the
+plan's full-file line numbers. Hand its output to both reviewers, with the
+round-2 sentence their prompts gain below. When it says `diff-base: none`,
+the round is a full review: the reviewers read the whole plan as in round 1,
+and rule A lowers nothing. The gate, not this
+session, counts the round by rule A:
+
+Rule A: from round 2 on, a new major finding that cites a plan line outside the diff since the last reviewed text counts as minor; a blocker, a security finding and a finding with no plan line count at full severity, and a previous finding stays counted until it is marked resolved.
+
+The reviewers state rule B, and the gate records each lowering they make
+from round 1 on:
+
+Rule B: a major that a named test, `Regression:` command or gate in the plan will fail on during execution is minor — never a blocker, never a security finding.
+
 **One round:**
 
 First take the hash of the plan the reviewers are about to read, and keep the
@@ -947,6 +971,8 @@ End your response with the REQUIRED machine-readable `json` findings block
 (schema in `agents/plan-critic.md`) so the orchestrator can pipe it to the
 dedup helper. You have no Write tool — return the block inline, do not write a file.
 Read local files only inside the repo under exploration, plus paths this prompt gives you (the brief, the plan, and templates it names)."
+From round 2 the prompt adds one sentence, followed by the `--diff` output:
+"Previous findings are in the plan's `## Critic Verdict`; the diff since the last reviewed text is below. Mark each previous finding by id in `previous`."
 
 **scope-guardian** — scope alignment check.
 Prompt: "Check this implementation plan against the brief.
@@ -958,6 +984,8 @@ plan's Verification section. End your response with the REQUIRED machine-readabl
 `json` findings block (schema in `agents/scope-guardian.md`). You have no Write
 tool — return the block inline, do not write a file.
 Read local files only inside the repo under exploration, plus paths this prompt gives you (the brief, the plan, and templates it names)."
+From round 2 the prompt adds one sentence, followed by the `--diff` output:
+"Previous findings are in the plan's `## Critic Verdict`; the diff since the last reviewed text is below. Mark each previous finding by id in `previous`."
 
 After both complete, **extract each reviewer's trailing `json` findings block**
 and pipe both into the dedup helper via **stdin** — the reviewers are read-only
@@ -974,6 +1002,15 @@ JSON
 
 `plan-gate.mjs --record` prints one JSON line: `round`, `verdict`
 (`BLOCK` = a blocker is open, `REVISE` = majors only, `PASS`) and `counts`.
+It also prints `diff_base` (the sha256 of the text this round was counted
+against by rule A, or null), `diff_note` (one line: why a round from round 2
+on was counted fully), `lowered` (how many findings count below what a
+reviewer rated) and `snapshot` (`kept: …` or `not kept: <reason>`). The
+snapshot is the operative text this round reviewed, kept under
+`<git dir>/voyage/plan-snapshots/` and never committed; the next round's
+`--diff` reads it. A plan outside any git repository (plan mode) keeps no
+snapshot (`not kept: no git repository`), so its next round counts fully.
+A failed snapshot write does not fail the round.
 Exit 1 means the round cap is spent (see "After round 3"). Exit 2 means the
 round cannot be recorded: broken input, a reviewer missing from it (an absent
 review is not a clean one), or a plan that changed after `--hash` — the