@@ -0,0 +1,22 @@
+---
+'@objectstack/metadata-core': patch
+---
+
+fix(metadata-core): an exclusive protocol comparator (`'>18'`, `'<18'`) names the major it admits in the `OS_PROTOCOL_INCOMPATIBLE` refusal
+
+Clause-②: no
+Metadata-protocol: none
+
+The refusal for a package whose `engines.protocol` excludes this runtime names a target major (`targetMajor` in the diagnostic and in `error.details`) and, for a package behind the runtime, `objectstack migrate meta --from N`. It used to find the target by peeling every leading operator off the range as if it were `^`, so on a protocol-18 runtime both `'>18'` (19 and up) and `'<18'` (17 and below) answered `migrate meta --from 18`, a migration from the runtime's own major.
+
+Now the target is read from the majors the range admits, with the same grammar that decides whether it admits the runtime:
+
+- **`'>18'` on an 18 runtime** targets 19. The package is ahead, so the answer is the upgrade remedy from the previous release: "Upgrade the runtime to protocol 19", and no `migrateCommand`. On a 17 runtime it now names protocol 19 too, where it used to name 18, which `'>18'` does not admit.
+- **`'<18'` and `'<18.0.0'`** target 17: `migrate meta --from 17`.
+- **A compound range** targets its floor in either order: `'<18 >=15'` targets 15 (it named 18), and `'>15 <18'` targets 16 (it named 15).
+- **A `||` union** still targets its lowest alternative, now read the same way: `'<17 || >19'` targets 16.
+- **A range that admits no major** (`'>=19 <15'`, `'<0'`) has `targetMajor: null` and the bare `objectstack migrate meta`.
+
+`^`, `~`, `>=`, `<=`, wildcards, exact versions, hyphen ranges and partial bounds (`'>18.1'`, `'<18.5'`) answer as before. No range changes between admitted and refused: only the refusal's target and prescription change.
+
+Two CLI readers of `targetMajor` follow: `objectstack migrate meta` now rewrites a `'<18'` range to `'^18'` when it migrates a stack to protocol 18 (it used to leave it for the load to refuse), and the protocol-version advisory now speaks for such a range.
@@ -455,3 +455,92 @@ describe('[#26480] a package AHEAD of this runtime is told to upgrade, never to
     expect(refuse('^10 || ^12').migrateCommand).toBe('objectstack migrate meta --from 10');
   });
 });
+
+describe('[#26546] the refusal reads the comparator direction, so an exclusive bound names the major it admits', () => {
+  // A bare `'>N'` admits N+1 and up, and `'<N'` admits N-1 and below. Peeling
+  // the operator off as if it were `^` named N for both, and on an N runtime
+  // that is `migrate meta --from N`, a migration from the runtime's own major.
+  const refuse = (range: string, runtime = '18.0.0') => {
+    const r = checkProtocolCompat({ id: 'com.acme.pkg', engines: { protocol: range } }, runtime);
+    expect(r.status).toBe('incompatible');
+    if (r.status !== 'incompatible') throw new Error(`'${range}' was not refused under ${runtime}`);
+    return r.diagnostic;
+  };
+  const expectAhead = (range: string, target: number, runtime = '18.0.0') => {
+    const d = refuse(range, runtime);
+    expect(d.targetMajor).toBe(target);
+    expect(d).not.toHaveProperty('migrateCommand');
+    expect(d.message).not.toContain('migrate meta');
+    expect(d.message).toContain(`Upgrade the runtime to protocol ${target}`);
+  };
+  const expectBehind = (range: string, target: number, runtime = '18.0.0') => {
+    const d = refuse(range, runtime);
+    expect(d.targetMajor).toBe(target);
+    expect(d.migrateCommand).toBe(`objectstack migrate meta --from ${target}`);
+    expect(d.message.endsWith(`Run: objectstack migrate meta --from ${target}`)).toBe(true);
+  };
+
+  it("'>18' on an 18 runtime is a package ahead of it: protocol 19, no migrateCommand", () => {
+    expectAhead('>18', 19);
+  });
+
+  it("'<18' on an 18 runtime is a package behind it: --from 17", () => {
+    expectBehind('<18', 17);
+  });
+
+  it("CONTROL: the inclusive '>=19' and '<=17' answer as before", () => {
+    expectAhead('>=19', 19);
+    expectBehind('<=17', 17);
+  });
+
+  it("names the right upgrade when the runtime is further behind: '>18' on 17 needs protocol 19, not 18", () => {
+    expectAhead('>18', 19, '17.0.0');
+  });
+
+  it('an explicit floor bound reads as the bare one, and a partial bound keeps its major', () => {
+    expectBehind('<18.0.0', 17);
+    expectBehind('<18.0', 17);
+    // `'<18.5'` admits 18.0 to 18.4, `'>18.1'` admits 18.2 and up: major 18 either way.
+    expectBehind('<18.5', 18, '19.0.0');
+    expectAhead('>18.1', 18, '17.0.0');
+  });
+
+  it('a bounded range targets its floor, whichever order its comparators are written in', () => {
+    expectBehind('>=15 <18', 15);
+    expectBehind('<18 >=15', 15);
+    expectBehind('>15 <18', 16);
+  });
+
+  it('a union still targets its lowest alternative', () => {
+    expectBehind('<17 || >19', 16);
+    expectBehind('^17 || ^16', 16);
+    expectAhead('>18 || ^20', 19);
+  });
+
+  it('a range that admits no major names none, so neither remedy points at a wrong one', () => {
+    for (const range of ['>=19 <15', '<0']) {
+      const d = refuse(range);
+      expect(d.targetMajor).toBeNull();
+      expect(d.migrateCommand).toBe('objectstack migrate meta');
+    }
+  });
+
+  it('the HTTP answer for the ahead case carries no migrateCommand', () => {
+    let thrown: unknown;
+    try {
+      assertProtocolCompat({ id: 'com.acme.pkg', engines: { protocol: '>18' } }, '18.0.0', () => {});
+    } catch (e) {
+      thrown = e;
+    }
+    expect(isProtocolIncompatibleError(thrown)).toBe(true);
+    const answer = protocolIncompatibleAnswer(thrown as ProtocolIncompatibleError);
+    expect(answer.status).toBe(422);
+    expect(answer.code).toBe('OS_PROTOCOL_INCOMPATIBLE');
+    expect(answer.details).toEqual({
+      requiredRange: '>18',
+      rangeSource: 'engines.protocol',
+      protocolVersion: '18.0.0',
+      targetMajor: 19,
+    });
+  });
+});
@@ -80,15 +80,18 @@ export interface ProtocolIncompatibleDiagnostic {
   runtimeMajor: number;
   /**
    * The declared major the package targets, when a single major is
-   * determinable: the range's leading version token, and for a `||` union the
-   * lowest of its alternatives', whatever order they are written in.
+   * determinable: the lowest major the range admits, or for a range open
+   * below (`'<18'`), the highest (#26546). An exclusive bound reads its
+   * direction: on an 18 runtime `'>18'` targets 19 and `'<18'` targets 17. For
+   * a `||` union it is the lowest of its alternatives', whatever order they
+   * are written in.
    */
   targetMajor: number | null;
   /**
    * The command that resolves the refusal (wired end-to-end by ADR-0087 P2),
-   * present only when there is metadata to move FORWARD: the declared floor
-   * major is at or below the runtime's, or is not determinable. A package
-   * whose floor major is ABOVE the runtime's is ahead of it, and
+   * present only when there is metadata to move FORWARD: `targetMajor` is at
+   * or below the runtime's, or is not determinable. A package whose
+   * `targetMajor` is ABOVE the runtime's is ahead of it, and
    * `migrate meta` cannot help (#26480): the member is absent and `message`
    * names the two remedies that apply, upgrading the runtime or installing a
    * build of the package for this runtime's protocol.
@@ -322,78 +325,112 @@ export function rangeAdmitsMajor(range: string, runtimeMajor: number): boolean |
   return verdict;
 }
 
-/** One `||` alternative: the single-range grammar {@link rangeAdmitsMajor} combines. */
+/** One `||` alternative: does its {@link alternativeMajorSpan} hold `runtimeMajor`? */
 function alternativeAdmitsMajor(r: string, runtimeMajor: number): boolean | null {
+  const span = alternativeMajorSpan(r);
+  if (span === null) return null;
+  return (span.lo === null || runtimeMajor >= span.lo) && (span.hi === null || runtimeMajor <= span.hi);
+}
+
+/**
+ * The majors one `||` alternative admits, as an inclusive interval; `null` at
+ * an end leaves that end open (`'<18'` is `{ lo: null, hi: 17 }`, `'*'` is
+ * open at both).
+ */
+interface MajorSpan {
+  lo: number | null;
+  hi: number | null;
+}
+
+/**
+ * The single-range grammar, read once: {@link alternativeAdmitsMajor} asks
+ * whether the span holds a major, and {@link declaredTargetMajor} names the
+ * major a refused range targets from the same span, so the verdict and the
+ * prescription cannot read one comparator two ways (#26546). `null` when the
+ * shape is not recognized.
+ */
+function alternativeMajorSpan(r: string): MajorSpan | null {
   if (r === '') return null;
-  if (r === '*' || r === 'x' || r === 'latest') return true;
+  if (r === '*' || r === 'x' || r === 'latest') return { lo: null, hi: null };
 
-  // Compound comparator range, e.g. ">=11.0.0 <13.0.0" (space- or comma-joined).
+  // Compound comparator range, e.g. ">=11.0.0 <13.0.0" (space- or comma-joined):
+  // the intersection of its comparators' spans.
   const parts = r.split(COMPARATOR_SEPARATOR).filter(Boolean);
   if (parts.length > 1 && parts.every((p) => /^[<>]=?/.test(p))) {
-    let ok = true;
+    let lo: number | null = null;
+    let hi: number | null = null;
     for (const p of parts) {
-      const admits = comparatorAdmitsMajor(p, runtimeMajor);
-      if (admits === null) return null;
-      ok = ok && admits;
+      const span = comparatorMajorSpan(p);
+      if (span === null) return null;
+      if (span.lo !== null) lo = lo === null ? span.lo : Math.max(lo, span.lo);
+      if (span.hi !== null) hi = hi === null ? span.hi : Math.min(hi, span.hi);
     }
-    return ok;
+    return { lo, hi };
   }
 
   // Hyphen range: "11.0.0 - 12.0.0".
   const hyphenParts = hyphenRangeEnds(r);
   if (hyphenParts) {
     const lo = leadingMajor(hyphenParts[0]);
     const hi = leadingMajor(hyphenParts[1]);
-    if (lo === null || hi === null) return null;
-    return runtimeMajor >= lo && runtimeMajor <= hi;
+    return lo === null || hi === null ? null : { lo, hi };
   }
 
   // Single comparator.
-  if (/^[<>]=?/.test(r)) return comparatorAdmitsMajor(r, runtimeMajor);
+  if (/^[<>]=?/.test(r)) return comparatorMajorSpan(r);
 
   // Caret: `^N` / `^N.x.y` pins the major (for N >= 1, which all protocol
   // majors are).
   if (r.startsWith('^')) {
     const maj = leadingMajor(r.slice(1));
-    return maj === null ? null : runtimeMajor === maj;
+    return maj === null ? null : { lo: maj, hi: maj };
   }
 
   // Tilde: `~N.x.y` also pins the major for the handshake's purposes.
   if (r.startsWith('~')) {
     const maj = leadingMajor(r.slice(1));
-    return maj === null ? null : runtimeMajor === maj;
+    return maj === null ? null : { lo: maj, hi: maj };
   }
 
   // `N.x` / `N.*` wildcard.
   const wildcard = r.match(/^(\d+)\.(?:x|\*)/i);
-  if (wildcard) return runtimeMajor === Number.parseInt(wildcard[1]!, 10);
+  if (wildcard) {
+    const maj = Number.parseInt(wildcard[1]!, 10);
+    return { lo: maj, hi: maj };
+  }
 
   // Bare exact version or bare major: `11`, `11.0.0`.
   const exact = leadingMajor(r);
-  if (exact !== null && /^\d+(\.\d+){0,2}$/.test(r)) return runtimeMajor === exact;
+  if (exact !== null && /^\d+(\.\d+){0,2}$/.test(r)) return { lo: exact, hi: exact };
 
   return null;
 }
 
 /**
- * The major a refused range targets: the major of its leading version token,
- * its floor as the upgrade guidance reads it (`'^10'` → 10, `'>=15 <18'` → 15).
- * A `||` union targets its LOWEST alternative's, in whatever order the
- * alternatives are written: `'^16 || ^17'` and `'^17 || ^16'` are one range and
- * get one `migrate meta --from`. A floor above the runtime's major means the
- * package is ahead of the runtime, and gets no `migrate meta` at all.
+ * The major a refused range targets, read from the majors it admits
+ * ({@link alternativeMajorSpan}): its floor (`'^10'` → 10, `'>=15 <18'` → 15,
+ * `'>18'` → 19), or, for a range open below, its ceiling (`'<18'` → 17,
+ * `'<=17'` → 17), the newest major it was written for. A `||` union targets its
+ * LOWEST alternative's, in whatever order the alternatives are written:
+ * `'^16 || ^17'` and `'^17 || ^16'` are one range and get one
+ * `migrate meta --from`. A target above the runtime's major means the package
+ * is ahead of the runtime, and gets no `migrate meta` at all.
  */
-function declaredFloorMajor(range: string): number | null {
+function declaredTargetMajor(range: string): number | null {
   let lowest: number | null = null;
   for (const alternative of rangeAlternatives(range)) {
-    const major = leadingMajor(alternative.replace(/^[\^~<>=\s]+/, ''));
-    if (major === null) return null;
+    const span = alternativeMajorSpan(alternative);
+    // A span that holds no major at all (`'<0'`, `'>=19 <15'`) has none to name.
+    const empty = span === null || (span.lo !== null && span.hi !== null && span.lo > span.hi);
+    const major = empty ? null : (span.lo ?? span.hi);
+    if (major === null || major < 0) return null;
     if (lowest === null || major < lowest) lowest = major;
   }
   return lowest;
 }
 
-function comparatorAdmitsMajor(comparator: string, runtimeMajor: number): boolean | null {
+/** The majors one comparator admits: an interval open at one end. */
+function comparatorMajorSpan(comparator: string): MajorSpan | null {
   const peeled = peelComparatorOperator(comparator);
   if (peeled === null) return null;
   const { op, rest } = peeled;
@@ -413,17 +450,17 @@ function comparatorAdmitsMajor(comparator: string, runtimeMajor: number): boolea
   switch (op) {
     case '>=':
       // `>=maj.*` admits major maj and up.
-      return runtimeMajor >= maj;
+      return { lo: maj, hi: null };
     case '>':
       // bare `>maj` → `>=maj+1` (excludes maj); `>maj.x.y` still admits maj.
-      return isBare ? runtimeMajor > maj : runtimeMajor >= maj;
+      return { lo: isBare ? maj + 1 : maj, hi: null };
     case '<=':
       // `<=maj.*` admits major maj and below.
-      return runtimeMajor <= maj;
+      return { lo: null, hi: maj };
     case '<':
       // `<maj.0.0` (bare or explicit floor) excludes all of major maj;
       // `<maj.5.0` still admits maj.
-      return atMajorFloor ? runtimeMajor < maj : runtimeMajor <= maj;
+      return { lo: null, hi: atMajorFloor ? maj - 1 : maj };
     default:
       return null;
   }
@@ -451,9 +488,9 @@ export function checkProtocolCompat(
   }
 
   const packageId = manifest.id ?? '<unknown>';
-  const targetMajor = declaredFloorMajor(declared.range);
+  const targetMajor = declaredTargetMajor(declared.range);
   // [#26480] `migrate meta` replays metadata forward from an OLDER major. A
-  // floor above this runtime's major is a package built for a newer protocol:
+  // target above this runtime's major is a package built for a newer protocol:
   // nothing here can migrate it, so the refusal names what can apply instead.
   const ahead = targetMajor !== null && targetMajor > runtimeMajor;
   const migrateCommand = ahead