diff --git a/src/queue/processors.ts b/src/queue/processors.ts
index 54059580aa..5dc8b93840 100644
--- a/src/queue/processors.ts
+++ b/src/queue/processors.ts
@@ -3301,6 +3301,11 @@ export function gateCheckPolicy(
   confirmedContributor?: boolean,
   slopRisk?: number | null,
   authorHistory?: { mergedPrCount: number; closedUnmergedPrCount: number },
+  sizeContext?: {
+    changedFileCount: number;
+    changedLineCount: number;
+    guardrailHit: boolean;
+  },
 ) {
   // `settings` is already the EFFECTIVE config (`.gittensory.yml` > DB > defaults), resolved upstream by
   // resolveRepositorySettings, so the blocker modes here reflect the repo's config file directly.
@@ -3326,6 +3331,13 @@ export function gateCheckPolicy(
     slopGateMinScore: settings.slopGateMinScore ?? null,
     slopRisk: slopRisk ?? null,
     confirmedContributor: confirmedContributorForPack,
+    // PR-size + guardrail manual-review HOLD (#gate-size / #gate-guardrail): the MODE comes from config; the
+    // thresholds default to 10 files / 500 lines (advisory.ts constants); the live counts + guardrail-hit come from
+    // the per-PR sizeContext threaded by the caller.
+    sizeGateMode: settings.sizeGateMode,
+    changedFileCount: sizeContext?.changedFileCount ?? null,
+    changedLineCount: sizeContext?.changedLineCount ?? null,
+    guardrailHit: sizeContext?.guardrailHit ?? false,
   };
 }
 
@@ -4546,12 +4558,28 @@ async function maybePublishPrPublicSurface(
       pr.number,
     );
 
+    // PR-size + guardrail manual-review HOLD (#gate-size / #gate-guardrail): compute the live change size + the
+    // guardrail-hit from the resolved files (getReviewFiles is memoized — no extra fetch) so the gate can HOLD an
+    // oversized or guardrail-touching PR (neutral → "manual" verdict), visible even in advisory/dry-run.
+    const sizeGateFiles = await getReviewFiles();
+    const gateSizeContext = {
+      changedFileCount: sizeGateFiles.length,
+      changedLineCount: sizeGateFiles.reduce(
+        (n, f) => n + f.additions + f.deletions,
+        0,
+      ),
+      guardrailHit: isGuardrailHit(
+        changedPathsForGuardrail(sizeGateFiles),
+        await loadHardGuardrailGlobs(env, repoFullName),
+      ),
+    };
     const gatePolicy = gateCheckPolicy(
       settings,
       readiness.total,
       confirmedContributor,
       slopRisk,
       authorHistory,
+      gateSizeContext,
     );
     gateEvaluation = gateEnabled
       ? evaluateGateCheck(advisory, gatePolicy)
diff --git a/src/rules/advisory.ts b/src/rules/advisory.ts
index 14359007b1..47e6ba65f3 100644
--- a/src/rules/advisory.ts
+++ b/src/rules/advisory.ts
@@ -55,6 +55,18 @@ export type GateCheckPolicy = {
    *  regardless of confirmed status, which now affects only on-chain scoring). `undefined` = unresolved.
    *  (#gate-nonconfirmed) */
   confirmedContributor?: boolean | undefined;
+  /** PR-size HOLD (#gate-size). When set (advisory/block), a PR with >= sizeGateMaxFiles changed files OR
+   *  >= sizeGateMaxLines changed (added+deleted) lines that would OTHERWISE pass is HELD for manual review — a
+   *  neutral gate → "manual" verdict, never auto-merged and never a hard failure. Defaults off; thresholds default
+   *  to 10 files / 500 lines. This is a HOLD (advisory dry-run friendly), not a close. */
+  sizeGateMode?: GateRuleMode | undefined;
+  /** Aggregate change size, threaded from the resolved file list (changedLineCount = additions + deletions). */
+  changedFileCount?: number | null | undefined;
+  changedLineCount?: number | null | undefined;
+  /** True when the PR's diff trips a hard guardrail path (caller computes via loadHardGuardrailGlobs + isGuardrailHit).
+   *  A guardrail hit HOLDS an otherwise-passing gate for manual review (neutral → "manual"), never auto-merged.
+   *  Always-on (the guardrail globs default to the crucial/config-as-code/engine paths). (#gate-guardrail) */
+  guardrailHit?: boolean | undefined;
 };
 
 export type GateCheckEvaluation = {
@@ -378,6 +390,40 @@ export function formatCheckRunOutput(
   return annotations.length > 0 ? { title, summary, text, annotations } : { title, summary, text };
 }
 
+const SIZE_HOLD_DEFAULT_MAX_FILES = 10;
+const SIZE_HOLD_DEFAULT_MAX_LINES = 500;
+
+/** Oversized-PR manual-review HOLD finding (#gate-size), or null when the size gate is off or the PR is within both
+ *  thresholds. A HOLD (→ neutral gate → "manual" verdict), never a hard blocker, so it is dry-run/advisory friendly. */
+function buildSizeHoldFinding(policy: GateCheckPolicy): AdvisoryFinding | null {
+  if (!policy.sizeGateMode || policy.sizeGateMode === "off") return null;
+  const files = policy.changedFileCount ?? 0;
+  const lines = policy.changedLineCount ?? 0;
+  if (
+    files < SIZE_HOLD_DEFAULT_MAX_FILES &&
+    lines < SIZE_HOLD_DEFAULT_MAX_LINES
+  )
+    return null;
+  return {
+    code: "oversized_pr",
+    severity: "warning",
+    title: "Large change — held for manual review",
+    detail: `This PR changes ${files} file(s) / ${lines} line(s) (hold threshold: ${SIZE_HOLD_DEFAULT_MAX_FILES} files or ${SIZE_HOLD_DEFAULT_MAX_LINES} lines).`,
+    action: "Split this into smaller, focused PRs, or a maintainer reviews and merges it manually.",
+  };
+}
+
+/** Guardrail-path manual-review HOLD finding (#gate-guardrail). A HOLD (neutral gate), never a hard blocker. */
+function buildGuardrailHoldFinding(): AdvisoryFinding {
+  return {
+    code: "guardrail_hold",
+    severity: "warning",
+    title: "Touches a guarded path — held for manual review",
+    detail: "This PR changes a guardrail-protected path, so it is held for a maintainer to review and merge manually.",
+    action: "A maintainer must review and merge this change.",
+  };
+}
+
 export function evaluateGateCheck(advisoryResult: Advisory, policy: GateCheckPolicy = {}): GateCheckEvaluation {
   const warnings = advisoryResult.findings.filter((finding) => finding.severity === "warning");
   // App/infra state (repo not synced yet, PR not cached): gittensory cannot evaluate this PR yet, so the
@@ -440,6 +486,24 @@ export function evaluateGateCheck(advisoryResult: Advisory, policy: GateCheckPol
         warnings,
       };
     }
+    // Manual-review HOLD (#gate-size / #gate-guardrail): a PR that would otherwise PASS but is oversized or touches
+    // a guarded path is HELD for a human (neutral → "manual" verdict) rather than auto-approved — never a failure,
+    // so neutral never blocks the merge (dry-run/advisory friendly) and a contributor PR is never auto-closed for size.
+    const sizeHold = buildSizeHoldFinding(effective);
+    const guardrailHold = effective.guardrailHit ? buildGuardrailHoldFinding() : null;
+    const holds = [sizeHold, guardrailHold].filter(
+      (f): f is AdvisoryFinding => f !== null,
+    );
+    if (holds.length > 0) {
+      return {
+        enabled: true,
+        conclusion: "neutral",
+        title: "Gittensory Gate — held for manual review",
+        summary: holds.map((h) => sanitizeForCheckRun(h.title)).join("; "),
+        blockers: [],
+        warnings: [...warnings, ...holds],
+      };
+    }
     return {
       enabled: true,
       conclusion: "success",
diff --git a/src/signals/focus-manifest.ts b/src/signals/focus-manifest.ts
index 8fc4b4a3e8..fa11eefa27 100644
--- a/src/signals/focus-manifest.ts
+++ b/src/signals/focus-manifest.ts
@@ -27,6 +27,7 @@ export type FocusManifestGateConfig = {
   slopMode: GateRuleMode | null;
   slopMinScore: number | null;
   slopAiAdvisory: boolean | null;
+  sizeMode: GateRuleMode | null;
   aiReviewMode: GateRuleMode | null;
   aiReviewByok: boolean | null;
   aiReviewProvider: "anthropic" | "openai" | null;
@@ -239,6 +240,7 @@ const EMPTY_GATE_CONFIG: FocusManifestGateConfig = {
   slopMode: null,
   slopMinScore: null,
   slopAiAdvisory: null,
+  sizeMode: null,
   aiReviewMode: null,
   aiReviewByok: null,
   aiReviewProvider: null,
@@ -382,6 +384,11 @@ function parseGateConfig(value: JsonValue | undefined, warnings: string[]): Focu
   if (slop !== undefined && slop !== null && slopRecord === undefined) {
     warnings.push(`Manifest gate field "gate.slop" must be a mapping; ignoring it.`);
   }
+  const size = record.size;
+  const sizeRecord = size !== null && typeof size === "object" && !Array.isArray(size) ? (size as Record<string, JsonValue>) : undefined;
+  if (size !== undefined && size !== null && sizeRecord === undefined) {
+    warnings.push(`Manifest gate field "gate.size" must be a mapping; ignoring it.`);
+  }
   const gate: FocusManifestGateConfig = {
     present: false,
     enabled: normalizeOptionalBoolean(record.enabled, "gate.enabled", warnings),
@@ -393,6 +400,7 @@ function parseGateConfig(value: JsonValue | undefined, warnings: string[]): Focu
     slopMode: normalizeOptionalGateMode(slopRecord?.mode, "gate.slop.mode", warnings),
     slopMinScore: normalizeOptionalScore(slopRecord?.minScore, "gate.slop.minScore", warnings),
     slopAiAdvisory: normalizeOptionalBoolean(slopRecord?.aiAdvisory, "gate.slop.aiAdvisory", warnings),
+    sizeMode: normalizeOptionalGateMode(sizeRecord?.mode, "gate.size.mode", warnings),
     aiReviewMode: normalizeOptionalGateMode(aiReviewRecord?.mode, "gate.aiReview.mode", warnings),
     aiReviewByok: normalizeOptionalBoolean(aiReviewRecord?.byok, "gate.aiReview.byok", warnings),
     aiReviewProvider: normalizeOptionalEnum(aiReviewRecord?.provider, "gate.aiReview.provider", ["anthropic", "openai"] as const, warnings),
@@ -413,6 +421,7 @@ function parseGateConfig(value: JsonValue | undefined, warnings: string[]): Focu
     gate.slopMode !== null ||
     gate.slopMinScore !== null ||
     gate.slopAiAdvisory !== null ||
+    gate.sizeMode !== null ||
     gate.aiReviewMode !== null ||
     gate.aiReviewByok !== null ||
     gate.aiReviewProvider !== null ||
@@ -442,6 +451,7 @@ export function gateConfigToJson(gate: FocusManifestGateConfig): JsonValue {
     if (gate.readinessMinScore !== null) readiness.minScore = gate.readinessMinScore;
     out.readiness = readiness;
   }
+  if (gate.sizeMode !== null) out.size = { mode: gate.sizeMode };
   if (gate.slopMode !== null || gate.slopMinScore !== null || gate.slopAiAdvisory !== null) {
     const slop: Record<string, JsonValue> = {};
     if (gate.slopMode !== null) slop.mode = gate.slopMode;
@@ -915,6 +925,7 @@ export function resolveEffectiveSettings(dbSettings: RepositorySettings, manifes
   if (gate.duplicates !== null) effective.duplicatePrGateMode = gate.duplicates;
   if (gate.readinessMode !== null) effective.qualityGateMode = gate.readinessMode;
   if (gate.readinessMinScore !== null) effective.qualityGateMinScore = gate.readinessMinScore;
+  if (gate.sizeMode !== null) effective.sizeGateMode = gate.sizeMode;
   if (gate.slopMode !== null) effective.slopGateMode = gate.slopMode;
   if (gate.slopMinScore !== null) effective.slopGateMinScore = gate.slopMinScore;
   if (gate.slopAiAdvisory !== null) effective.slopAiAdvisory = gate.slopAiAdvisory;
diff --git a/src/types.ts b/src/types.ts
index 8352cd5cf2..64dc108ea7 100644
--- a/src/types.ts
+++ b/src/types.ts
@@ -505,6 +505,10 @@ export type RepositorySettings = {
    *  score + warnings in context; `block` = ALSO hard-block when slopRisk >= slopGateMinScore (deterministic
    *  only, applies to every author like every blocker). Default `off` — opt-in via .gittensory.yml. */
   slopGateMode: GateRuleMode;
+  /** PR-size manual-review HOLD (#gate-size). `off` (default/absent) = no size hold; `advisory`/`block` = a PR with
+   *  >= 10 changed files OR >= 500 changed (added+deleted) lines that would otherwise pass is HELD for manual review
+   *  (neutral gate → "manual" verdict), never auto-merged and never a hard failure. Opt-in via `gate.size.mode`. */
+  sizeGateMode?: GateRuleMode | undefined;
   /** Merge-readiness gate (#merge-readiness). `off`/`advisory`/`block`. No min-score. Default `off`. */
   mergeReadinessGateMode: GateRuleMode;
   /** Focus-manifest policy gate (#555). When `block`, the focus manifest's declared policy (blocked paths,
diff --git a/test/unit/focus-manifest.test.ts b/test/unit/focus-manifest.test.ts
index 3d79fa3255..bac19015aa 100644
--- a/test/unit/focus-manifest.test.ts
+++ b/test/unit/focus-manifest.test.ts
@@ -477,7 +477,7 @@ describe("compileFocusManifestPolicy", () => {
       issueDiscoveryPolicy: "neutral",
       maintainerNotes: [],
       publicNotes: ["Keep PRs focused.", "Maximize your reward payout"],
-      gate: { present: false, enabled: null, pack: null, linkedIssue: null, duplicates: null, readinessMode: null, readinessMinScore: null, slopMode: null, slopMinScore: null, slopAiAdvisory: null, aiReviewMode: null, aiReviewByok: null, aiReviewProvider: null, aiReviewModel: null, aiReviewAllAuthors: null, mergeReadiness: null, selfAuthoredLinkedIssue: null, manifestPolicy: null, firstTimeContributorGrace: null },
+      gate: { present: false, enabled: null, pack: null, linkedIssue: null, duplicates: null, readinessMode: null, readinessMinScore: null, slopMode: null, slopMinScore: null, slopAiAdvisory: null, sizeMode: null, aiReviewMode: null, aiReviewByok: null, aiReviewProvider: null, aiReviewModel: null, aiReviewAllAuthors: null, mergeReadiness: null, selfAuthoredLinkedIssue: null, manifestPolicy: null, firstTimeContributorGrace: null },
       settings: {},
       review: { present: false, footerText: null, note: null, fields: {}, profile: null, inlineComments: null, pathInstructions: [], instructions: null, excludePaths: [], preMergeChecks: [] },
       features: { present: false, rag: null, reputation: null, unifiedComment: null, safety: null },
@@ -766,7 +766,7 @@ describe("parseFocusManifest gate config", () => {
   it("parses a full gate section including the readiness block", () => {
     const m = parseFocusManifest({ gate: { linkedIssue: "block", duplicates: "advisory", readiness: { mode: "block", minScore: 70 } } });
     expect(m.present).toBe(true);
-    expect(m.gate).toEqual({ present: true, enabled: null, pack: null, linkedIssue: "block", duplicates: "advisory", readinessMode: "block", readinessMinScore: 70, slopMode: null, slopMinScore: null, slopAiAdvisory: null, aiReviewMode: null, aiReviewByok: null, aiReviewProvider: null, aiReviewModel: null, aiReviewAllAuthors: null, mergeReadiness: null, selfAuthoredLinkedIssue: null, manifestPolicy: null, firstTimeContributorGrace: null });
+    expect(m.gate).toEqual({ present: true, enabled: null, pack: null, linkedIssue: "block", duplicates: "advisory", readinessMode: "block", readinessMinScore: 70, slopMode: null, slopMinScore: null, slopAiAdvisory: null, sizeMode: null, aiReviewMode: null, aiReviewByok: null, aiReviewProvider: null, aiReviewModel: null, aiReviewAllAuthors: null, mergeReadiness: null, selfAuthoredLinkedIssue: null, manifestPolicy: null, firstTimeContributorGrace: null });
   });
 
   it("parses gate.mergeReadiness + gate.firstTimeContributorGrace, round-trips them, and warns on bad values (#822)", () => {
@@ -1408,3 +1408,16 @@ describe("composeRepoReviewContext (#review-skills)", () => {
     expect(out.length).toBeLessThanOrEqual(16_000);
   });
 });
+
+describe("gate.size manual-review hold config (#gate-size)", () => {
+  it("parses gate.size.mode, warns on a non-mapping size, and round-trips via gateConfigToJson", () => {
+    const m = parseFocusManifest({ gate: { size: { mode: "advisory" } } });
+    expect(m.gate.sizeMode).toBe("advisory");
+    expect(m.gate.present).toBe(true);
+    const bad = parseFocusManifest({ gate: { size: "nope" } });
+    expect(bad.gate.sizeMode).toBeNull();
+    expect(bad.warnings.some((w) => w.includes("gate.size"))).toBe(true);
+    const round = parseFocusManifest({ gate: gateConfigToJson(m.gate) });
+    expect(round.gate.sizeMode).toBe("advisory");
+  });
+});
diff --git a/test/unit/gate-check-policy.test.ts b/test/unit/gate-check-policy.test.ts
index 84aaceb3be..44c450617c 100644
--- a/test/unit/gate-check-policy.test.ts
+++ b/test/unit/gate-check-policy.test.ts
@@ -577,3 +577,28 @@ describe("buildAuthorizedPrActionAdvisory self-authored parity (#self-authored-p
     expect(advisory.findings.some((finding) => finding.code === "self_authored_linked_issue")).toBe(false);
   });
 });
+
+describe("size + guardrail manual-review HOLD (#gate-size / #gate-guardrail)", () => {
+  const clean = (): Advisory => ({ ...missingIssueAdvisory(), findings: [] });
+  it("holds (neutral) an oversized PR; passes under thresholds; off/unset = no hold", () => {
+    expect(evaluateGateCheck(clean(), { sizeGateMode: "advisory", changedFileCount: 12, changedLineCount: 10 }).conclusion).toBe("neutral"); // > 10 files
+    expect(evaluateGateCheck(clean(), { sizeGateMode: "advisory", changedFileCount: 2, changedLineCount: 600 }).conclusion).toBe("neutral"); // > 500 lines
+    expect(evaluateGateCheck(clean(), { sizeGateMode: "advisory", changedFileCount: 9, changedLineCount: 499 }).conclusion).toBe("success"); // under both thresholds
+    expect(evaluateGateCheck(clean(), { sizeGateMode: "off", changedFileCount: 50, changedLineCount: 9000 }).conclusion).toBe("success"); // gate off ⇒ no hold
+    expect(evaluateGateCheck(clean(), { changedFileCount: 50, changedLineCount: 9000 }).conclusion).toBe("success"); // mode unset ⇒ no hold
+    expect(evaluateGateCheck(clean(), { sizeGateMode: "advisory" }).conclusion).toBe("success"); // no counts ⇒ 0 ⇒ no hold
+  });
+  it("holds (neutral) on a guardrail hit, surfacing the hold finding in warnings", () => {
+    const out = evaluateGateCheck(clean(), { guardrailHit: true });
+    expect(out.conclusion).toBe("neutral");
+    expect(out.warnings.map((w) => w.code)).toContain("guardrail_hold");
+  });
+  it("a real hard blocker WINS over a size/guardrail hold (failure, not neutral)", () => {
+    const out = evaluateGateCheck(missingIssueAdvisory(), { linkedIssueGateMode: "block", sizeGateMode: "advisory", changedFileCount: 50, changedLineCount: 9000, guardrailHit: true });
+    expect(out.conclusion).toBe("failure");
+  });
+  it("resolveEffectiveSettings maps gate.size.mode → sizeGateMode", () => {
+    const eff = resolveEffectiveSettings(settings({}), parseFocusManifest({ gate: { size: { mode: "advisory" } } }));
+    expect(eff.sizeGateMode).toBe("advisory");
+  });
+});