diff --git a/.env.example b/.env.example
index 4f0db2ba22..0d8b6e7c99 100644
--- a/.env.example
+++ b/.env.example
@@ -69,27 +69,27 @@ GITTENSORY_REVIEW_ENRICHMENT=false
 # blameLink,approvalIntegrity,ciCheckSignals,undocumentedExport,staleBranch,commitHygiene
 # pendingReviewRequests,testRatio,migrationSafety,looseRange,terminology,todoMarker,magicNumber
 # conflictMarker,debugLeftover,sizeSmell,floatingPromise,deepNesting,errorSwallow,unsafeAny,a11y
-# i18n,unusedExport,exhaustiveness,flakyTest,commitLint
+# i18n,unusedExport,exhaustiveness,flakyTest,commitLint,apiBreak
 #
 # Profile defaults:
 # fast: dependency,dependencyDiff,lockfileDrift,secret,license,installScript,heavyDependency
 # hardcodedUrl,actionPin,eol,redos,provenance,secretLog,typosquat,iacMisconfig,nativeBuild
 # testRatio,migrationSafety,looseRange,terminology,todoMarker,magicNumber,conflictMarker
-# debugLeftover,sizeSmell,floatingPromise,deepNesting,errorSwallow,unsafeAny,a11y,i18n
+# debugLeftover,sizeSmell,floatingPromise,deepNesting,errorSwallow,unsafeAny,a11y,i18n,apiBreak
 # balanced (default): dependency,dependencyDiff,lockfileDrift,secret,license,installScript
 # heavyDependency,hardcodedUrl,actionPin,eol,redos,provenance,codeowners,secretLog,assetWeight
 # typosquat,commitSignature,iacMisconfig,nativeBuild,history,docCommentDrift,duplication
 # churnHotspot,blameLink,approvalIntegrity,ciCheckSignals,undocumentedExport,staleBranch
 # commitHygiene,pendingReviewRequests,testRatio,migrationSafety,looseRange,terminology
 # todoMarker,magicNumber,conflictMarker,debugLeftover,sizeSmell,floatingPromise,deepNesting
-# errorSwallow,unsafeAny,a11y,i18n,unusedExport,exhaustiveness,flakyTest,commitLint
+# errorSwallow,unsafeAny,a11y,i18n,unusedExport,exhaustiveness,flakyTest,commitLint,apiBreak
 # deep: dependency,dependencyDiff,lockfileDrift,secret,license,installScript,heavyDependency
 # hardcodedUrl,actionPin,eol,redos,provenance,codeowners,secretLog,assetWeight,typosquat
 # commitSignature,iacMisconfig,nativeBuild,history,docCommentDrift,duplication,churnHotspot
 # blameLink,approvalIntegrity,ciCheckSignals,undocumentedExport,staleBranch,commitHygiene
 # pendingReviewRequests,testRatio,migrationSafety,looseRange,terminology,todoMarker,magicNumber
 # conflictMarker,debugLeftover,sizeSmell,floatingPromise,deepNesting,errorSwallow,unsafeAny,a11y
-# i18n,unusedExport,exhaustiveness,flakyTest,commitLint
+# i18n,unusedExport,exhaustiveness,flakyTest,commitLint,apiBreak
 # END GENERATED REES ANALYZERS
 
 # Submitter-reputation spend control (internal-only): downgrades new/burst/low-rep
diff --git a/apps/gittensory-ui/src/lib/rees-analyzers.ts b/apps/gittensory-ui/src/lib/rees-analyzers.ts
index 977dd95a4d..901efeddf1 100644
--- a/apps/gittensory-ui/src/lib/rees-analyzers.ts
+++ b/apps/gittensory-ui/src/lib/rees-analyzers.ts
@@ -1219,6 +1219,30 @@ export const REES_ANALYZERS = [
         "Structured-fields-only: reads commit.message subjects, linted independently, never cross-line state. Fail-safe on missing token/fetch error.",
     },
   },
+  {
+    name: "apiBreak",
+    title: "Breaking API change (removed/renamed export)",
+    category: "quality",
+    cost: "local",
+    defaultEnabled: true,
+    profiles: ["fast", "balanced", "deep"],
+    requires: ["files"],
+    limits: {
+      maxEntrypoints: 25,
+      maxFindings: 25,
+    },
+    docs: {
+      summary:
+        "Flags an exported symbol a PR removes or renames in a package public entrypoint — a semver-major break for downstream consumers shipped without a major version bump.",
+      looksAt:
+        "Removed (-) top-level export declarations and re-exports in changed public-entrypoint files (index/mod/main/public-api) whose name is not re-added anywhere in the same file's patch.",
+      reports:
+        "Public entrypoint file, old-file line, and the removed or renamed exported symbol name — never surrounding code.",
+      network: "Pure local analyzer. No external network call.",
+      notes:
+        "Conservative: only a top-level export whose exact name disappears from the file's public surface is reported; a same-name edit (signature or value change) or a non-entrypoint file is never flagged. Bounded by entrypoint and finding caps; fail-safe on absent or malformed patches.",
+    },
+  },
 ] as const satisfies readonly ReesAnalyzerDoc[];
 
 export const REES_ANALYZER_NAMES = REES_ANALYZERS.map((analyzer) => analyzer.name);
diff --git a/review-enrichment/analyzer-metadata.json b/review-enrichment/analyzer-metadata.json
index 34fdbf9e7e..bf9eece876 100644
--- a/review-enrichment/analyzer-metadata.json
+++ b/review-enrichment/analyzer-metadata.json
@@ -1374,6 +1374,32 @@
         "network": "Calls the GitHub PR-commits API once, bounded to one page.",
         "notes": "Structured-fields-only: reads commit.message subjects, linted independently, never cross-line state. Fail-safe on missing token/fetch error."
       }
+    },
+    {
+      "name": "apiBreak",
+      "title": "Breaking API change (removed/renamed export)",
+      "category": "quality",
+      "cost": "local",
+      "defaultEnabled": true,
+      "profiles": [
+        "fast",
+        "balanced",
+        "deep"
+      ],
+      "requires": [
+        "files"
+      ],
+      "limits": {
+        "maxEntrypoints": 25,
+        "maxFindings": 25
+      },
+      "docs": {
+        "summary": "Flags an exported symbol a PR removes or renames in a package public entrypoint — a semver-major break for downstream consumers shipped without a major version bump.",
+        "looksAt": "Removed (-) top-level export declarations and re-exports in changed public-entrypoint files (index/mod/main/public-api) whose name is not re-added anywhere in the same file's patch.",
+        "reports": "Public entrypoint file, old-file line, and the removed or renamed exported symbol name — never surrounding code.",
+        "network": "Pure local analyzer. No external network call.",
+        "notes": "Conservative: only a top-level export whose exact name disappears from the file's public surface is reported; a same-name edit (signature or value change) or a non-entrypoint file is never flagged. Bounded by entrypoint and finding caps; fail-safe on absent or malformed patches."
+      }
     }
   ]
 }
diff --git a/review-enrichment/src/analyzers/api-break.ts b/review-enrichment/src/analyzers/api-break.ts
new file mode 100644
index 0000000000..676a32d304
--- /dev/null
+++ b/review-enrichment/src/analyzers/api-break.ts
@@ -0,0 +1,129 @@
+// Breaking-API-change analyzer (#1510, part of #1499). A no-checkout headless reviewer sees only the diff, so it
+// cannot tell that a PR DROPS or RENAMES a symbol a package's public entrypoint used to export — a semver-major
+// break that reaches DOWNSTREAM consumers, distinct from the in-repo caller-impact analyzer. This fills that gap
+// purely from the patch: for each changed PUBLIC-ENTRYPOINT file (index/mod/main/public-api barrels) it collects
+// the exported names on removed (`-`) lines and on added (`+`) lines, and reports a name present in the REMOVED
+// set but absent from the ADDED set — i.e. the public surface lost it (a removal or a rename). Deliberately
+// CONSERVATIVE and fail-safe: a same-name edit (a signature/value change re-adds the name) is never flagged, only
+// exact whole-name loss is; a non-entrypoint file is out of scope (that is the caller-impact analyzer's job).
+// Deterministic, no network, no token. Reports file, old-file line, and symbol only — never surrounding code.
+import type { ApiBreakFinding, EnrichRequest } from "../types.js";
+
+const MAX_ENTRYPOINTS = 25; // cap changed entrypoint files scanned per PR
+const MAX_FINDINGS = 25; // keep the brief bounded
+
+// Files whose top-level exports form a package's PUBLIC surface: barrel/entry modules only. Restricting to these
+// entrypoint basenames keeps the signal conservative — a removed export in an internal module is not a downstream
+// break. Declaration (`.d.ts`) and test/spec files are excluded: their exports are not a shipped public API.
+const SOURCE_RE = /\.(?:ts|tsx|mts|cts|js|jsx|mjs|cjs)$/;
+const SKIP_RE = /(?:\.d\.ts$|\.min\.|\.test\.|\.spec\.|__tests__\/|(?:^|\/)tests?\/)/;
+const ENTRYPOINT_BASENAME = /^(?:index|mod|main|public-api|public_api|api)$/;
+
+// A named top-level export DECLARATION at column 0 (an indented `export` inside a namespace/module block is
+// intentionally not matched). `const enum` precedes the bare `const` alternative so the enum name, not `enum`, is
+// captured.
+const EXPORT_DECL_RE =
+  /^export\s+(?:async\s+)?(?:abstract\s+)?(?:function\s*\*?|class|const\s+enum|const|let|var|interface|type|enum)\s+([A-Za-z_$][\w$]*)/;
+// `export * as ns from "..."` binds one namespace name; `export * from "..."` binds none and is not matched.
+const EXPORT_STAR_AS_RE = /^export\s+\*\s+as\s+([A-Za-z_$][\w$]*)\s+from\b/;
+// A single-line `export { a, b as c } [from "..."]` / `export type { T } from "..."` list. Aliases resolve to the
+// PUBLIC (right-hand) name. A brace list spanning multiple lines is intentionally not parsed (fail-safe).
+const EXPORT_NAMED_RE = /^export\s+(?:type\s+)?\{([^}]*)\}/;
+const IDENT_RE = /^[A-Za-z_$][\w$]*$/;
+
+/** True when a changed path is a package PUBLIC ENTRYPOINT (barrel/entry basename, source ext, not decl/test). Pure. */
+export function isPublicEntrypoint(path: string): boolean {
+  if (!SOURCE_RE.test(path) || SKIP_RE.test(path)) return false;
+  const base = path.split("/").pop() ?? path;
+  const stem = base.replace(SOURCE_RE, "");
+  return ENTRYPOINT_BASENAME.test(stem);
+}
+
+/** Every exported symbol name a single source line declares or re-exports at the top level. Handles declarations,
+ *  `export default`, single-line `export { … }`/`export type { … }` (aliases resolve to the PUBLIC name), and
+ *  `export * as ns from`. A bare `export * from "…"` binds no nameable symbol and yields none. Pure. */
+export function exportedNames(line: string): string[] {
+  const decl = EXPORT_DECL_RE.exec(line);
+  if (decl) return [decl[1]!];
+  if (/^export\s+default\b/.test(line)) return ["default"];
+  const starAs = EXPORT_STAR_AS_RE.exec(line);
+  if (starAs) return [starAs[1]!];
+  const named = EXPORT_NAMED_RE.exec(line);
+  if (named) {
+    const out: string[] = [];
+    for (const raw of named[1]!.split(",")) {
+      const spec = raw.trim();
+      if (!spec) continue;
+      const parts = spec.split(/\s+as\s+/);
+      const publicName = (parts[parts.length - 1] ?? "").trim();
+      if (IDENT_RE.test(publicName)) out.push(publicName);
+    }
+    return out;
+  }
+  return [];
+}
+
+interface RemovedExport {
+  symbol: string;
+  line: number;
+}
+
+/** Removed/renamed exports in one entrypoint file's patch: names exported on a removed (`-`) line whose name is NOT
+ *  re-exported on any added (`+`) line of the same file (a same-name edit re-adds it and is not a break). The
+ *  old-file line counter advances over removed + context lines (never added lines) so the reported line is the
+ *  symbol's pre-PR location. Pure. */
+export function removedExports(patch: string): RemovedExport[] {
+  const removed = new Map<string, number>();
+  const added = new Set<string>();
+  let oldLine = 0;
+  let inHunk = false;
+  for (const raw of patch.split("\n")) {
+    const hunk = /^@@ -(\d+)(?:,\d+)? \+\d+(?:,\d+)? @@/.exec(raw);
+    if (hunk) {
+      oldLine = Number(hunk[1]);
+      inHunk = true;
+      continue;
+    }
+    if (!inHunk) continue;
+    if (raw.startsWith("+")) {
+      if (raw.startsWith("+++")) continue;
+      for (const name of exportedNames(raw.slice(1))) added.add(name);
+    } else if (raw.startsWith("-")) {
+      if (raw.startsWith("---")) continue;
+      for (const name of exportedNames(raw.slice(1))) {
+        if (!removed.has(name)) removed.set(name, oldLine);
+      }
+      oldLine++;
+    } else if (!raw.startsWith("\\")) {
+      oldLine++;
+    }
+  }
+  const out: RemovedExport[] = [];
+  for (const [symbol, line] of removed) {
+    if (!added.has(symbol)) out.push({ symbol, line });
+  }
+  return out;
+}
+
+/** Analyzer entrypoint: flag exported symbols a PR drops or renames from a public entrypoint — a downstream
+ *  semver-major break. Deterministic and fail-safe: returns [] when no entrypoint file changed or on absent
+ *  patches; bounded by entrypoint and finding caps. */
+export async function scanApiBreak(
+  req: EnrichRequest,
+  signal?: AbortSignal,
+): Promise<ApiBreakFinding[]> {
+  if (signal?.aborted) return [];
+  const findings: ApiBreakFinding[] = [];
+  let entrypoints = 0;
+  for (const file of req.files ?? []) {
+    if (signal?.aborted) break;
+    if (!file.patch || !isPublicEntrypoint(file.path)) continue;
+    if (entrypoints >= MAX_ENTRYPOINTS) break;
+    entrypoints++;
+    for (const removed of removedExports(file.patch)) {
+      findings.push({ file: file.path, line: removed.line, symbol: removed.symbol });
+      if (findings.length >= MAX_FINDINGS) return findings;
+    }
+  }
+  return findings;
+}
diff --git a/review-enrichment/src/analyzers/registry.ts b/review-enrichment/src/analyzers/registry.ts
index a703f1db3d..4d7c059363 100644
--- a/review-enrichment/src/analyzers/registry.ts
+++ b/review-enrichment/src/analyzers/registry.ts
@@ -47,6 +47,7 @@ import { scanUndocumentedExport } from "./undocumented-export.js";
 import { scanUnusedExport } from "./unused-export.js";
 import { scanExhaustivenessDrift } from "./exhaustiveness-drift.js";
 import { scanFlakyTest } from "./flaky-test.js";
+import { scanApiBreak } from "./api-break.js";
 import type {
   AnalyzerDescriptor,
   AnalyzerFn,
@@ -1375,6 +1376,39 @@ export const ANALYZER_DESCRIPTORS = [
     run: (req, { signal, analysis, diagnostics }) =>
       scanCommitLint(req, fetch, { signal, analysis, diagnostics }),
   }),
+  descriptor({
+    name: "apiBreak",
+    title: "Breaking API change (removed/renamed export)",
+    category: "quality",
+    cost: "local",
+    defaultEnabled: true,
+    requires: ["files"],
+    limits: { maxEntrypoints: 25, maxFindings: 25 },
+    docs: {
+      summary:
+        "Flags an exported symbol a PR removes or renames in a package public entrypoint — a semver-major break for downstream consumers shipped without a major version bump.",
+      looksAt:
+        "Removed (-) top-level export declarations and re-exports in changed public-entrypoint files (index/mod/main/public-api) whose name is not re-added anywhere in the same file's patch.",
+      reports:
+        "Public entrypoint file, old-file line, and the removed or renamed exported symbol name — never surrounding code.",
+      network: "Pure local analyzer. No external network call.",
+      notes:
+        "Conservative: only a top-level export whose exact name disappears from the file's public surface is reported; a same-name edit (signature or value change) or a non-entrypoint file is never flagged. Bounded by entrypoint and finding caps; fail-safe on absent or malformed patches.",
+    },
+    render: (findings, helpers) => {
+      if (!findings.length) return [];
+      const lines = [
+        "### Breaking API changes (exported symbol removed or renamed in a public entrypoint)",
+      ];
+      for (const item of findings) {
+        lines.push(
+          `- ${helpers.safeCodeSpan(`${item.file}:${item.line}`)} — ${helpers.safeCodeSpan(item.symbol)} removed from the public surface`,
+        );
+      }
+      return lines;
+    },
+    run: (req, { signal }) => scanApiBreak(req, signal),
+  }),
 ] as const satisfies readonly AnyAnalyzerDescriptor[];
 
 export const ANALYZER_NAMES = ANALYZER_DESCRIPTORS.map(
diff --git a/review-enrichment/src/render.ts b/review-enrichment/src/render.ts
index f36d63ca1f..166470a0e4 100644
--- a/review-enrichment/src/render.ts
+++ b/review-enrichment/src/render.ts
@@ -498,6 +498,7 @@ export function renderBrief(
   lines.push(...renderDescriptorSection("flakyTest", findings.flakyTest));
   lines.push(...renderDescriptorSection("hardcodedUrl", findings.hardcodedUrl));
   lines.push(...renderDescriptorSection("commitLint", findings.commitLint));
+  lines.push(...renderDescriptorSection("apiBreak", findings.apiBreak));
 
   if (!lines.length) return { promptSection: "", systemSuffix: "" };
 
diff --git a/review-enrichment/src/types.ts b/review-enrichment/src/types.ts
index 3e462bb4b6..b8dd44b0b3 100644
--- a/review-enrichment/src/types.ts
+++ b/review-enrichment/src/types.ts
@@ -592,6 +592,15 @@ export interface CommitLintFinding {
 }
 
 /** Structured analyzer output. Each analyzer fills its own key; more land as analyzers ship (#1477/#1478). */
+/** An exported symbol a PR removes or renames in a package public entrypoint — a semver-major break for
+ *  downstream consumers shipped without a major version bump (#1510, part of #1499). Reports file, old-file line,
+ *  and the removed/renamed symbol name only — never code. */
+export interface ApiBreakFinding {
+  file: string;
+  line: number;
+  symbol: string;
+}
+
 export interface BriefFindings {
   dependency?: DependencyFinding[];
   dependencyDiff?: DependencyDiffFinding[];
@@ -642,6 +651,7 @@ export interface BriefFindings {
   flakyTest?: FlakyTestFinding[];
   hardcodedUrl?: HardcodedUrlFinding[];
   commitLint?: CommitLintFinding[];
+  apiBreak?: ApiBreakFinding[];
 }
 
 /** A JSDoc/TSDoc block whose `@param` tags name parameters the adjacent function no longer declares — a
diff --git a/review-enrichment/test/analyzer-registry.test.ts b/review-enrichment/test/analyzer-registry.test.ts
index 08061dbbc4..ceb52b9717 100644
--- a/review-enrichment/test/analyzer-registry.test.ts
+++ b/review-enrichment/test/analyzer-registry.test.ts
@@ -59,6 +59,7 @@ const EXPECTED_ANALYZERS = [
   "exhaustiveness",
   "flakyTest",
   "commitLint",
+  "apiBreak",
 ];
 
 test("analyzer descriptors cover the runtime registry in stable order", () => {
diff --git a/review-enrichment/test/api-break.test.ts b/review-enrichment/test/api-break.test.ts
new file mode 100644
index 0000000000..b34800711c
--- /dev/null
+++ b/review-enrichment/test/api-break.test.ts
@@ -0,0 +1,151 @@
+// Units for the breaking-API-change analyzer (#1510). Own file (not enrichment.test.ts) so concurrent analyzer PRs
+// do not collide. Runs against the compiled dist/.
+import { test } from "node:test";
+import assert from "node:assert/strict";
+import {
+  scanApiBreak,
+  isPublicEntrypoint,
+  exportedNames,
+  removedExports,
+} from "../dist/analyzers/api-break.js";
+import { renderBrief } from "../dist/render.js";
+
+// Build a one-hunk unified-diff patch. `oldStart` sets the -N old-file start in the header. Each entry is
+// [prefix, text] with prefix "-", "+", or " " (context).
+const hunk = (lines, oldStart = 1) =>
+  `@@ -${oldStart},0 +${oldStart},0 @@\n${lines.map(([p, t]) => `${p}${t}`).join("\n")}`;
+
+test("isPublicEntrypoint: recognizes barrel/entry source files; rejects internal, decl, and test files", () => {
+  assert.equal(isPublicEntrypoint("src/index.ts"), true);
+  assert.equal(isPublicEntrypoint("mod.ts"), true);
+  assert.equal(isPublicEntrypoint("packages/x/src/main.js"), true);
+  assert.equal(isPublicEntrypoint("src/public-api.ts"), true);
+  assert.equal(isPublicEntrypoint("api.mts"), true);
+  assert.equal(isPublicEntrypoint("src/util.ts"), false);
+  assert.equal(isPublicEntrypoint("src/index.d.ts"), false);
+  assert.equal(isPublicEntrypoint("src/index.test.ts"), false);
+  assert.equal(isPublicEntrypoint("README.md"), false);
+});
+
+test("exportedNames: extracts each top-level declaration form", () => {
+  assert.deepEqual(exportedNames("export function alpha() {}"), ["alpha"]);
+  assert.deepEqual(exportedNames("export async function beta() {}"), ["beta"]);
+  assert.deepEqual(exportedNames("export function* gen() {}"), ["gen"]);
+  assert.deepEqual(exportedNames("export const gamma = 1;"), ["gamma"]);
+  assert.deepEqual(exportedNames("export let delta = 1;"), ["delta"]);
+  assert.deepEqual(exportedNames("export var epsilon = 1;"), ["epsilon"]);
+  assert.deepEqual(exportedNames("export class Zeta {}"), ["Zeta"]);
+  assert.deepEqual(exportedNames("export abstract class Eta {}"), ["Eta"]);
+  assert.deepEqual(exportedNames("export interface Theta {}"), ["Theta"]);
+  assert.deepEqual(exportedNames("export type Iota = string;"), ["Iota"]);
+  assert.deepEqual(exportedNames("export enum Kappa { A }"), ["Kappa"]);
+  assert.deepEqual(exportedNames("export const enum Lambda { A }"), ["Lambda"]);
+});
+
+test("exportedNames: resolves re-exports, aliases, default, and star-as; ignores bare star and non-exports", () => {
+  assert.deepEqual(exportedNames('export { a, b } from "./x";'), ["a", "b"]);
+  assert.deepEqual(exportedNames('export { internal as publicName } from "./x";'), ["publicName"]);
+  assert.deepEqual(exportedNames("export { c };"), ["c"]);
+  assert.deepEqual(exportedNames('export type { T, U } from "./types";'), ["T", "U"]);
+  assert.deepEqual(exportedNames("export default function main() {}"), ["default"]);
+  assert.deepEqual(exportedNames("export default foo;"), ["default"]);
+  assert.deepEqual(exportedNames('export * as ns from "./x";'), ["ns"]);
+  assert.deepEqual(exportedNames('export * from "./x";'), []);
+  assert.deepEqual(exportedNames("const notExported = 1;"), []);
+  assert.deepEqual(exportedNames("  export const indented = 1;"), []);
+});
+
+test("removedExports: flags a removed declaration export not re-added, at its old-file line", () => {
+  const out = removedExports(
+    hunk([[" ", "line0"], ["-", "export function gone() {}"], [" ", "kept"]], 10),
+  );
+  assert.deepEqual(out, [{ symbol: "gone", line: 11 }]);
+});
+
+test("removedExports: does not flag a same-name edit (removed and re-added)", () => {
+  const out = removedExports(hunk([["-", "export const cfg = 1;"], ["+", "export const cfg = 2;"]]));
+  assert.deepEqual(out, []);
+});
+
+test("removedExports: flags a rename (old name dropped, new name added)", () => {
+  const out = removedExports(
+    hunk([["-", "export function oldName() {}"], ["+", "export function newName() {}"]]),
+  );
+  assert.deepEqual(out, [{ symbol: "oldName", line: 1 }]);
+});
+
+test("removedExports: flags a name dropped from a re-export list", () => {
+  const out = removedExports(
+    hunk([["-", 'export { a, b } from "./x";'], ["+", 'export { a } from "./x";']]),
+  );
+  assert.deepEqual(out, [{ symbol: "b", line: 1 }]);
+});
+
+test("scanApiBreak: flags a removed export in an entrypoint, ignores internal modules", async () => {
+  const findings = await scanApiBreak({
+    repoFullName: "owner/repo",
+    prNumber: 1,
+    files: [
+      { path: "src/index.ts", patch: hunk([["-", "export function removed() {}"]]) },
+      { path: "src/internal.ts", patch: hunk([["-", "export function alsoRemoved() {}"]]) },
+    ],
+  });
+  assert.deepEqual(findings, [{ file: "src/index.ts", line: 1, symbol: "removed" }]);
+});
+
+test("scanApiBreak: fail-safe with no files, a patch-less entrypoint, and an added-only entrypoint", async () => {
+  assert.deepEqual(await scanApiBreak({ repoFullName: "o/r", prNumber: 1 }), []);
+  assert.deepEqual(
+    await scanApiBreak({ repoFullName: "o/r", prNumber: 1, files: [{ path: "src/index.ts" }] }),
+    [],
+  );
+  assert.deepEqual(
+    await scanApiBreak({
+      repoFullName: "o/r",
+      prNumber: 1,
+      files: [{ path: "src/index.ts", patch: hunk([["+", "export const added = 1;"]]) }],
+    }),
+    [],
+  );
+});
+
+test("scanApiBreak: returns [] when the signal is already aborted", async () => {
+  const controller = new AbortController();
+  controller.abort();
+  const findings = await scanApiBreak(
+    {
+      repoFullName: "o/r",
+      prNumber: 1,
+      files: [{ path: "src/index.ts", patch: hunk([["-", "export const x = 1;"]]) }],
+    },
+    controller.signal,
+  );
+  assert.deepEqual(findings, []);
+});
+
+test("scanApiBreak: caps findings at 25", async () => {
+  const lines = Array.from({ length: 30 }, (_, i) => ["-", `export const sym${i} = ${i};`]);
+  const findings = await scanApiBreak({
+    repoFullName: "o/r",
+    prNumber: 1,
+    files: [{ path: "src/index.ts", patch: hunk(lines) }],
+  });
+  assert.equal(findings.length, 25);
+});
+
+test("scanApiBreak: stops after the entrypoint cap without throwing", async () => {
+  const files = Array.from({ length: 30 }, (_, i) => ({
+    path: `pkg${i}/index.ts`,
+    patch: hunk([[" ", "// no export removed"]]),
+  }));
+  assert.deepEqual(await scanApiBreak({ repoFullName: "o/r", prNumber: 1, files }), []);
+});
+
+test("renderBrief: includes apiBreak findings via the descriptor render", () => {
+  const { promptSection } = renderBrief({
+    apiBreak: [{ file: "src/index.ts", line: 7, symbol: "publicApi" }],
+  });
+  assert.match(promptSection, /Breaking API changes/);
+  assert.match(promptSection, /publicApi/);
+  assert.match(promptSection, /src\/index\.ts:7/);
+});
diff --git a/src/review/enrichment-analyzer-names.ts b/src/review/enrichment-analyzer-names.ts
index 2d8c30ed61..9df807c72f 100644
--- a/src/review/enrichment-analyzer-names.ts
+++ b/src/review/enrichment-analyzer-names.ts
@@ -53,6 +53,7 @@ export const REES_ANALYZER_NAMES = [
   "exhaustiveness",
   "flakyTest",
   "commitLint",
+  "apiBreak",
 ] as const;
 
 export type ReesAnalyzerName = (typeof REES_ANALYZER_NAMES)[number];