diff --git a/tools/workflow-engine/pr-review-lifecycle.test.ts b/tools/workflow-engine/pr-review-lifecycle.test.ts
new file mode 100644
index 0000000000..8d785edad2
--- /dev/null
+++ b/tools/workflow-engine/pr-review-lifecycle.test.ts
@@ -0,0 +1,184 @@
+// Invariant tests for PrReviewLifecycle — producing-side review work substrate.
+
+import { describe, expect, test } from "bun:test";
+import {
+  PR_REVIEW_LIFECYCLE_UNIVERSE,
+  dispatchPrReviewTransition,
+  isPeerAgentTerritory,
+  newReviewContext,
+  type PrReviewLifecycle,
+  type ReviewFinding,
+} from "./pr-review-lifecycle.js";
+
+describe("PrReviewLifecycle universe", () => {
+  test("7 distinct review-lifecycle states", () => {
+    expect(PR_REVIEW_LIFECYCLE_UNIVERSE.length).toBe(7);
+    const kinds = PR_REVIEW_LIFECYCLE_UNIVERSE.map((s) => s.kind);
+    expect(kinds).toContain("observe");
+    expect(kinds).toContain("identify-finding");
+    expect(kinds).toContain("verify-finding");  // grep-substrate-anchors step
+    expect(kinds).toContain("post");
+    expect(kinds).toContain("conclude");
+  });
+});
+
+describe("dispatch transitions (happy path)", () => {
+  const baseContext = newReviewContext(5805, "self", "workflow-engine");
+
+  test("observe with NO findings → conclude (no-engagement)", () => {
+    const r = dispatchPrReviewTransition({ kind: "observe" }, baseContext);
+    expect(r.ok).toBe(true);
+    if (r.ok) {
+      expect(r.outcome.nextState.kind).toBe("conclude");
+      expect(r.outcome.artifact?.kind).toBe("no-engagement-warranted");
+    }
+  });
+
+  test("observe WITH findings → identify-finding", () => {
+    const finding: ReviewFinding = {
+      prNumber: 5805,
+      kind: { kind: "substrate-honest-praise", reason: "rank-4 substrate-primitive lands cleanly" },
+      content: "lgtm",
+      substrateAnchors: ["PR #5792 rank-4 substrate-primitive memory"],
+    };
+    const ctx = { ...baseContext, findings: [finding] };
+    const r = dispatchPrReviewTransition({ kind: "observe" }, ctx);
+    expect(r.ok).toBe(true);
+    if (r.ok) {
+      expect(r.outcome.nextState.kind).toBe("identify-finding");
+    }
+  });
+
+  test("identify-finding → compose", () => {
+    const r = dispatchPrReviewTransition({ kind: "identify-finding" }, baseContext);
+    expect(r.ok).toBe(true);
+    if (r.ok) {
+      expect(r.outcome.nextState.kind).toBe("compose");
+    }
+  });
+
+  test("compose → verify-finding (grep-substrate-anchors discipline)", () => {
+    const r = dispatchPrReviewTransition({ kind: "compose" }, baseContext);
+    expect(r.ok).toBe(true);
+    if (r.ok) {
+      expect(r.outcome.nextState.kind).toBe("verify-finding");
+    }
+  });
+
+  test("verify-finding with substantiated finding → post", () => {
+    const finding: ReviewFinding = {
+      prNumber: 5805,
+      kind: { kind: "bug", severity: "minor" },
+      content: "off-by-one suspected",
+      substrateAnchors: ["line 50: index < len"],  // anchor present
+    };
+    const ctx = { ...baseContext, findings: [finding] };
+    const r = dispatchPrReviewTransition({ kind: "verify-finding" }, ctx);
+    expect(r.ok).toBe(true);
+    if (r.ok) {
+      expect(r.outcome.nextState.kind).toBe("post");
+    }
+  });
+
+  test("verify-finding with UNSUBSTANTIATED finding → FindingUnsubstantiated feedback", () => {
+    const finding: ReviewFinding = {
+      prNumber: 5805,
+      kind: { kind: "bug", severity: "minor" },
+      content: "vibes off",
+      substrateAnchors: [],  // no anchor — per grep-substrate-anchors rule fails
+    };
+    const ctx = { ...baseContext, findings: [finding] };
+    const r = dispatchPrReviewTransition({ kind: "verify-finding" }, ctx);
+    expect(r.ok).toBe(false);
+    if (!r.ok) {
+      expect(r.feedback.kind).toBe("FindingUnsubstantiated");
+    }
+  });
+
+  test("post → follow-up with review-comment-posted artifact", () => {
+    const r = dispatchPrReviewTransition({ kind: "post" }, baseContext);
+    expect(r.ok).toBe(true);
+    if (r.ok) {
+      expect(r.outcome.nextState.kind).toBe("follow-up");
+      expect(r.outcome.artifact?.kind).toBe("review-comment-posted");
+    }
+  });
+
+  test("follow-up → conclude", () => {
+    const r = dispatchPrReviewTransition({ kind: "follow-up" }, baseContext);
+    expect(r.ok).toBe(true);
+    if (r.ok) {
+      expect(r.outcome.nextState.kind).toBe("conclude");
+    }
+  });
+
+  test("conclude is terminal (stays at conclude)", () => {
+    const r = dispatchPrReviewTransition({ kind: "conclude" }, baseContext);
+    expect(r.ok).toBe(true);
+    if (r.ok) {
+      expect(r.outcome.nextState.kind).toBe("conclude");
+    }
+  });
+});
+
+describe("ReviewFindingKind taxonomy", () => {
+  test("supports bug + design-question + substrate-engineering + naming + test-gap + praise + docs-gap + composes-with", () => {
+    const findings: ReviewFinding[] = [
+      { prNumber: 1, content: "x", kind: { kind: "bug", severity: "critical" } },
+      { prNumber: 1, content: "x", kind: { kind: "design-question", subject: "lifecycle DU shape?" } },
+      { prNumber: 1, content: "x", kind: { kind: "substrate-engineering-suggestion", alternative: "prefer Result<T,F>" } },
+      { prNumber: 1, content: "x", kind: { kind: "naming-improvement", current: "foo", proposed: "bar" } },
+      { prNumber: 1, content: "x", kind: { kind: "test-gap", uncovered: "edge case X" } },
+      { prNumber: 1, content: "x", kind: { kind: "substrate-honest-praise", reason: "composes cleanly" } },
+      { prNumber: 1, content: "x", kind: { kind: "documentation-gap", missing: "F# interop note" } },
+      { prNumber: 1, content: "x", kind: { kind: "composes-with-substrate", relatedRef: "PR #5805" } },
+    ];
+    expect(findings.length).toBe(8);
+  });
+});
+
+describe("isPeerAgentTerritory discriminator", () => {
+  test("self → false (my own work)", () => {
+    expect(isPeerAgentTerritory("self")).toBe(false);
+  });
+  test("peer-otto → true", () => {
+    expect(isPeerAgentTerritory("peer-otto")).toBe(true);
+  });
+  test("peer-codex / peer-lior / peer-alexa → true", () => {
+    expect(isPeerAgentTerritory("peer-codex")).toBe(true);
+    expect(isPeerAgentTerritory("peer-lior")).toBe(true);
+    expect(isPeerAgentTerritory("peer-alexa")).toBe(true);
+  });
+  test("human-aaron → true (substantive engagement; don't touch substrate)", () => {
+    expect(isPeerAgentTerritory("human-operator")).toBe(true);
+  });
+  test("unknown → false (default; treat as substrate-honest mine)", () => {
+    expect(isPeerAgentTerritory("unknown")).toBe(false);
+  });
+});
+
+describe("newReviewContext constructor", () => {
+  test("initializes with empty findings + zero observations", () => {
+    const ctx = newReviewContext(5805, "self", "workflow-engine");
+    expect(ctx.prNumber).toBe(5805);
+    expect(ctx.authorLane).toBe("self");
+    expect(ctx.substrateScope).toBe("workflow-engine");
+    expect(ctx.findings.length).toBe(0);
+    expect(ctx.observationsMade).toBe(0);
+  });
+});
+
+describe("type-level PrReviewLifecycle exhaustive switch (compile check)", () => {
+  test("all 7 variants distinguishable", () => {
+    const variants: PrReviewLifecycle[] = [
+      { kind: "observe" },
+      { kind: "identify-finding" },
+      { kind: "compose" },
+      { kind: "verify-finding" },
+      { kind: "post" },
+      { kind: "follow-up" },
+      { kind: "conclude" },
+    ];
+    expect(variants.length).toBe(7);
+  });
+});
diff --git a/tools/workflow-engine/pr-review-lifecycle.ts b/tools/workflow-engine/pr-review-lifecycle.ts
new file mode 100644
index 0000000000..c0bfc418a2
--- /dev/null
+++ b/tools/workflow-engine/pr-review-lifecycle.ts
@@ -0,0 +1,271 @@
+// tools/workflow-engine/pr-review-lifecycle.ts
+//
+// PrReviewLifecycle — substrate-naming substrate for PRODUCING-side
+// review work. Companion to B-0867.20 ReviewLifetime (receiving-side;
+// reviewer-feedback gate-state).
+//
+// Per the human maintainer (2026-05-28): "also does it give you time to look at prs and
+// put comments?" — substrate-engineering substrate-engineering substrate
+// gap: AutoLoopLifetime (PR #5805) only models SHIP work, not REVIEW
+// work. This DU makes producing-side review-substrate explicit.
+//
+// Composes with:
+// - .claude/rules/fighting-past-self-vs-peer-agent-distinguisher-fix-your-own-coordinate-on-peers-dont-punt-by-default.md
+//   (peer-agent commits = don't touch; peer-agent reviews = substantively engage)
+// - .claude/rules/asymmetric-authorship-substrate-entity-defines-consent-channel-recipient-acknowledges.md
+//   (reviewer AUTHORS feedback; receiving-side ACKNOWLEDGES)
+// - .claude/rules/honor-those-that-came-before.md (peer-agent work honored via substantive review)
+// - .claude/rules/glass-halo-bidirectional.md (review comments are public substrate; compound)
+// - B-0867.20 ReviewLifetime DU (PR #5758) — receiving-side; this PR
+//   provides producing-side complement
+// - AutoLoopLifetime (PR #5805) — will compose; producing-side review
+//   work becomes additional state-transition in loop substrate
+
+import { type LifetimeState } from "./world";
+
+// ─────────────────────────────────────────────────────────────────────
+// PrReviewLifecycle — producing-side state machine
+// ─────────────────────────────────────────────────────────────────────
+
+/**
+ * PrReviewLifecycle — substrate-naming substrate for PRODUCING-side
+ * review work. Captures the state machine for reviewing peer PRs +
+ * composing + posting substantive review comments.
+ *
+ * Distinguishes from B-0867.20 ReviewLifetime which captures
+ * RECEIVING-side gate states (my-PR-under-review states). This DU is
+ * for when I AM the reviewer of someone else's work.
+ */
+export interface PrReviewLifecycle extends LifetimeState {
+  readonly kind:
+    | "observe"               // read PR + diff + context; no engagement yet
+    | "identify-finding"      // substrate-engineering issue / question / praise surfaced
+    | "compose"               // write review comment with substantive content
+    | "verify-finding"        // grep substrate-anchor; check claim before posting (per substrate-honest discipline)
+    | "post"                  // ship the review via gh api / GraphQL mutation
+    | "follow-up"             // engage on author's response if any
+    | "conclude";             // no further engagement; mark as concluded
+}
+
+// ─────────────────────────────────────────────────────────────────────
+// Review-finding substrate
+// ─────────────────────────────────────────────────────────────────────
+
+/**
+ * ReviewFindingKind — substrate-engineering taxonomy of review-comment
+ * shapes. Each kind has different operational discipline.
+ */
+export type ReviewFindingKind =
+  | { kind: "bug"; severity: "critical" | "major" | "minor" }
+  | { kind: "design-question"; subject: string }
+  | { kind: "substrate-engineering-suggestion"; alternative: string }
+  | { kind: "naming-improvement"; current: string; proposed: string }
+  | { kind: "test-gap"; uncovered: string }
+  | { kind: "substrate-honest-praise"; reason: string }
+  | { kind: "documentation-gap"; missing: string }
+  | { kind: "composes-with-substrate"; relatedRef: string };
+
+/**
+ * ReviewFinding — substrate-engineering observation worth posting as
+ * review comment.
+ */
+export interface ReviewFinding {
+  readonly prNumber: number;
+  readonly filePath?: string;            // optional; some findings are PR-scoped
+  readonly lineNumber?: number;          // optional; some findings are file-scoped
+  readonly kind: ReviewFindingKind;
+  readonly content: string;              // substantive review-comment body
+  readonly substrateAnchors?: ReadonlyArray<string>;  // grep-substrate-anchors per rule
+}
+
+// ─────────────────────────────────────────────────────────────────────
+// Review context + outcome
+// ─────────────────────────────────────────────────────────────────────
+
+/**
+ * ReviewContext — substrate carried across the review-lifecycle.
+ */
+export interface ReviewContext {
+  readonly prNumber: number;
+  readonly authorLane: "self" | "peer-otto" | "peer-codex" | "peer-lior" | "peer-alexa" | "peer-vera" | "peer-riven" | "peer-amara" | "peer-kestrel" | "peer-prism" | "peer-mika" | "human-operator" | "unknown";
+  readonly substrateScope: "workflow-engine" | "encryption" | "zflash" | "ferry-preservation" | "rule-update" | "memory-file" | "infrastructure" | "other";
+  readonly findings: ReadonlyArray<ReviewFinding>;
+  readonly observationsMade: number;     // count of observe → identify cycles
+}
+
+/**
+ * ReviewOutcome — what the review-lifecycle produced.
+ */
+export interface ReviewOutcome {
+  readonly nextState: PrReviewLifecycle;
+  readonly artifact?: {
+    readonly kind: "review-comment-posted" | "thread-resolved" | "approval-given" | "no-engagement-warranted";
+    readonly threadId?: string;
+  };
+}
+
+// ─────────────────────────────────────────────────────────────────────
+// PrReviewFeedback — asymmetric-authorship per rule
+// ─────────────────────────────────────────────────────────────────────
+
+export type PrReviewFeedback =
+  | { kind: "PrNotAccessible"; prNumber: number; reason: string }
+  | { kind: "PeerAgentTerritory"; prNumber: number; lane: ReviewContext["authorLane"] }  // don't-touch-commits but review-allowed
+  | { kind: "FindingUnsubstantiated"; finding: ReviewFinding }       // failed verify step
+  | { kind: "RateLimitExhausted"; budget: "rest" | "graphql"; resetAt: number }
+  | { kind: "NoActionableFinding"; prNumber: number };
+
+export type PrReviewResult<T> =
+  | { ok: true; outcome: T }
+  | { ok: false; feedback: PrReviewFeedback };
+
+// ─────────────────────────────────────────────────────────────────────
+// State transition dispatch
+// ─────────────────────────────────────────────────────────────────────
+
+/**
+ * Dispatch the next PrReviewLifecycle state given current context.
+ *
+ * Per substrate-smoothness rule: exhaustive switch on PrReviewLifecycle
+ * variants; no if-statement chains. Per asymmetric-authorship: each
+ * transition AUTHORS feedback channel.
+ */
+export function dispatchPrReviewTransition(
+  current: PrReviewLifecycle,
+  context: ReviewContext,
+): PrReviewResult<ReviewOutcome> {
+  switch (current.kind) {
+    case "observe":
+      // After observing, identify findings (or conclude if no findings)
+      if (context.findings.length === 0) {
+        return {
+          ok: true,
+          outcome: {
+            nextState: { kind: "conclude" },
+            artifact: { kind: "no-engagement-warranted" },
+          },
+        };
+      }
+      return {
+        ok: true,
+        outcome: {
+          nextState: { kind: "identify-finding" },
+        },
+      };
+
+    case "identify-finding":
+      // After identifying, compose the review comment
+      return {
+        ok: true,
+        outcome: {
+          nextState: { kind: "compose" },
+        },
+      };
+
+    case "compose":
+      // After composing, verify (grep substrate-anchors)
+      return {
+        ok: true,
+        outcome: {
+          nextState: { kind: "verify-finding" },
+        },
+      };
+
+    case "verify-finding": {
+      // Per grep-substrate-anchors-before-razor-as-metaphysical: every
+      // finding MUST carry substrate-anchors before advancing to post.
+      // Both missing `substrateAnchors` AND an empty array mean
+      // unsubstantiated. Iterate all findings (not just findings[0]).
+      // Zero findings = NoActionableFinding feedback (can't post review
+      // when there's nothing to say).
+      if (context.findings.length === 0) {
+        return {
+          ok: false,
+          feedback: { kind: "NoActionableFinding", prNumber: context.prNumber },
+        };
+      }
+      const unsubstantiated = context.findings.find((f) =>
+        f.substrateAnchors === undefined || f.substrateAnchors.length === 0
+      );
+      if (unsubstantiated !== undefined) {
+        return {
+          ok: false,
+          feedback: { kind: "FindingUnsubstantiated", finding: unsubstantiated },
+        };
+      }
+      return {
+        ok: true,
+        outcome: {
+          nextState: { kind: "post" },
+        },
+      };
+    }
+
+    case "post":
+      // After posting, await follow-up (or conclude if no follow-up expected)
+      return {
+        ok: true,
+        outcome: {
+          nextState: { kind: "follow-up" },
+          artifact: { kind: "review-comment-posted" },
+        },
+      };
+
+    case "follow-up":
+      // After follow-up window, conclude
+      return {
+        ok: true,
+        outcome: {
+          nextState: { kind: "conclude" },
+        },
+      };
+
+    case "conclude":
+      // Terminal state; stays at conclude
+      return {
+        ok: true,
+        outcome: {
+          nextState: { kind: "conclude" },
+        },
+      };
+  }
+}
+
+// ─────────────────────────────────────────────────────────────────────
+// Reusable substrate exports
+// ─────────────────────────────────────────────────────────────────────
+
+export const PR_REVIEW_LIFECYCLE_UNIVERSE: ReadonlyArray<PrReviewLifecycle> = [
+  { kind: "observe" },
+  { kind: "identify-finding" },
+  { kind: "compose" },
+  { kind: "verify-finding" },
+  { kind: "post" },
+  { kind: "follow-up" },
+  { kind: "conclude" },
+];
+
+/**
+ * Determines if a PR is in peer-agent territory (don't touch commits but
+ * review-allowed per fighting-past-self-vs-peer-agent-distinguisher rule).
+ */
+export function isPeerAgentTerritory(authorLane: ReviewContext["authorLane"]): boolean {
+  return authorLane.startsWith("peer-") || authorLane === "human-operator";
+}
+
+/**
+ * Empty/initial ReviewContext for starting a new review.
+ */
+export function newReviewContext(
+  prNumber: number,
+  authorLane: ReviewContext["authorLane"],
+  substrateScope: ReviewContext["substrateScope"],
+): ReviewContext {
+  return {
+    prNumber,
+    authorLane,
+    substrateScope,
+    findings: [],
+    observationsMade: 0,
+  };
+}