diff --git a/packages/gittensory-engine/src/fleet-run-manifest.ts b/packages/gittensory-engine/src/fleet-run-manifest.ts
new file mode 100644
index 0000000000..04c2e78ec7
--- /dev/null
+++ b/packages/gittensory-engine/src/fleet-run-manifest.ts
@@ -0,0 +1,191 @@
+import { parse as parseYaml } from "yaml";
+
+// FleetRunManifest (#4299). The top-level config a *fleet operator* authors to run the miner across many repos:
+// which repos are in scope for a fleet run, and how a finite worktree/concurrency budget is split between them.
+// This is the OPERATOR-side analogue of, and deliberately NOT the same file as, `.gittensory-miner.yml` (see
+// miner-goal-spec.ts): that one is authored by a *target repo's maintainer* to say how their one repo wants to be
+// approached. Same tolerant-parser convention (every field optional, unknown keys ignored, malformed input
+// degrades to a documented default with a warning rather than throwing); opposite author and direction of intent.
+// See packages/gittensory-miner/docs/fleet-run-manifest.md for the full distinction.
+
+/** One target repo in a fleet run, with its own concurrent-worktree budget. */
+export type FleetRunManifestRepo = {
+  /** Canonical `owner/repo`. Compatible with opportunity-fanout's target normalization (a splittable pair). */
+  repoFullName: string;
+  /**
+   * Max concurrent worktrees (in-flight attempts) this repo may hold at once. A positive integer (`>= 1`); a
+   * non-integer is floored, a value below 1 falls back to the default. Default: 1.
+   */
+  maxConcurrentWorktrees: number;
+};
+
+/** Fleet run-manifest: the repos to work across and how to split the concurrency budget. See {@link DEFAULT_FLEET_RUN_MANIFEST}. */
+export type FleetRunManifest = {
+  /** Target repos, de-duplicated by `repoFullName` (first entry wins). Default: [] (no repos in scope). */
+  repos: readonly FleetRunManifestRepo[];
+  /**
+   * Total concurrent worktrees across the whole fleet, regardless of per-repo budgets. A positive integer
+   * (`>= 1`); floored, sub-1 falls back to the default. Default: 1.
+   */
+  totalConcurrentWorktrees: number;
+};
+
+/** Tolerant parser result: the normalized manifest plus warnings and whether the file expressed any non-default
+ *  field. Mirrors {@link ParsedMinerGoalSpec}'s present/warnings shape. */
+export type ParsedFleetRunManifest = {
+  present: boolean;
+  manifest: FleetRunManifest;
+  warnings: string[];
+};
+
+/** Safe defaults applied when a field is absent (or the file is missing): no repos in scope, one worktree total.
+ *  Deep-frozen shared singleton — clone before layering overrides. */
+export const DEFAULT_FLEET_RUN_MANIFEST: FleetRunManifest = Object.freeze({
+  repos: Object.freeze([]),
+  totalConcurrentWorktrees: 1,
+});
+
+const MAX_FLEET_RUN_MANIFEST_BYTES = 65_536;
+const MAX_MANIFEST_REPOS = 500;
+
+function cloneDefaultFleetRunManifest(): FleetRunManifest {
+  return { ...DEFAULT_FLEET_RUN_MANIFEST, repos: [...DEFAULT_FLEET_RUN_MANIFEST.repos] };
+}
+
+function emptyFleetRunManifest(warnings: string[] = []): ParsedFleetRunManifest {
+  return { present: false, manifest: cloneDefaultFleetRunManifest(), warnings };
+}
+
+/** `owner/repo` with exactly one slash and non-empty halves; anything else → null. Same shape the goal-spec /
+ *  portfolio-queue validators use, so a manifest repo is directly compatible with opportunity-fanout targets. */
+function normalizeRepoFullName(value: unknown): string | null {
+  if (typeof value !== "string") return null;
+  const [owner, repo, extra] = value.trim().split("/");
+  if (!owner || !repo || extra !== undefined) return null;
+  return `${owner}/${repo}`;
+}
+
+function normalizePositiveInteger(value: unknown, field: string, fallback: number, warnings: string[]): number {
+  if (value === undefined || value === null) return fallback;
+  if (typeof value !== "number" || !Number.isFinite(value)) {
+    warnings.push(`FleetRunManifest field "${field}" must be a positive whole number; falling back to ${fallback}.`);
+    return fallback;
+  }
+  const normalized = Math.floor(value);
+  if (normalized >= 1) return normalized;
+  warnings.push(`FleetRunManifest field "${field}" must be >= 1 after flooring; falling back to ${fallback}.`);
+  return fallback;
+}
+
+// A repo entry may be a bare `"owner/repo"` string (uses the default per-repo budget) or a `{ repoFullName,
+// maxConcurrentWorktrees? }` mapping. Anything else, or an unparseable repo name, is skipped with a warning.
+function normalizeRepoList(value: unknown, warnings: string[]): FleetRunManifestRepo[] {
+  if (value === undefined || value === null) return [];
+  if (!Array.isArray(value)) {
+    warnings.push(`FleetRunManifest field "repos" must be a list; ignoring a ${typeof value} value.`);
+    return [];
+  }
+  const result: FleetRunManifestRepo[] = [];
+  const seen = new Set<string>();
+  for (const [index, entry] of value.entries()) {
+    if (index >= MAX_MANIFEST_REPOS) {
+      warnings.push(`FleetRunManifest field "repos" exceeded ${MAX_MANIFEST_REPOS} entries; extra entries ignored.`);
+      break;
+    }
+    let repoFullName: string | null;
+    let maxConcurrentWorktrees = DEFAULT_FLEET_RUN_MANIFEST.totalConcurrentWorktrees;
+    if (typeof entry === "string") {
+      repoFullName = normalizeRepoFullName(entry);
+    } else if (entry && typeof entry === "object" && !Array.isArray(entry)) {
+      const record = entry as Record<string, unknown>;
+      repoFullName = normalizeRepoFullName(record.repoFullName);
+      maxConcurrentWorktrees = normalizePositiveInteger(record.maxConcurrentWorktrees, "maxConcurrentWorktrees", 1, warnings);
+    } else {
+      warnings.push(`FleetRunManifest "repos" skipped a non-string, non-mapping entry.`);
+      continue;
+    }
+    if (repoFullName === null) {
+      warnings.push(`FleetRunManifest "repos" skipped an entry with an invalid "owner/repo" name.`);
+      continue;
+    }
+    if (seen.has(repoFullName)) {
+      warnings.push(`FleetRunManifest "repos" skipped a duplicate entry for ${repoFullName}.`);
+      continue;
+    }
+    seen.add(repoFullName);
+    result.push({ repoFullName, maxConcurrentWorktrees });
+  }
+  return result;
+}
+
+function utf8ByteLength(value: string): number {
+  let bytes = 0;
+  for (const char of value) {
+    const codePoint = char.codePointAt(0) as number;
+    if (codePoint <= 0x7f) bytes += 1;
+    else if (codePoint <= 0x7ff) bytes += 2;
+    else if (codePoint <= 0xffff) bytes += 3;
+    else bytes += 4;
+  }
+  return bytes;
+}
+
+function hasConfiguredManifestFields(manifest: FleetRunManifest): boolean {
+  return manifest.repos.length > 0 || manifest.totalConcurrentWorktrees !== DEFAULT_FLEET_RUN_MANIFEST.totalConcurrentWorktrees;
+}
+
+/**
+ * Tolerantly normalize an already-parsed run-manifest object into a {@link ParsedFleetRunManifest}. Never throws:
+ * malformed shapes degrade to safe defaults and accumulate warnings so a fleet run can surface "your run-manifest
+ * had problems" without hard-failing. Mirrors {@link parseMinerGoalSpec}.
+ */
+export function parseFleetRunManifest(raw: unknown): ParsedFleetRunManifest {
+  if (raw === undefined || raw === null) return emptyFleetRunManifest();
+  if (typeof raw !== "object" || Array.isArray(raw)) {
+    return emptyFleetRunManifest([
+      "FleetRunManifest must be a mapping of fields; ignoring malformed config and falling back to safe defaults.",
+    ]);
+  }
+  const record = raw as Record<string, unknown>;
+  const warnings: string[] = [];
+  const manifest: FleetRunManifest = {
+    repos: normalizeRepoList(record.repos, warnings),
+    totalConcurrentWorktrees: normalizePositiveInteger(
+      record.totalConcurrentWorktrees,
+      "totalConcurrentWorktrees",
+      DEFAULT_FLEET_RUN_MANIFEST.totalConcurrentWorktrees,
+      warnings,
+    ),
+  };
+  if (!hasConfiguredManifestFields(manifest)) {
+    warnings.push("FleetRunManifest contained no recognized non-default fields; falling back to safe defaults.");
+    return { present: false, manifest: cloneDefaultFleetRunManifest(), warnings };
+  }
+  return { present: true, manifest, warnings };
+}
+
+/**
+ * Parse raw run-manifest file content (JSON or YAML). Malformed content degrades to an absent manifest with a
+ * warning rather than throwing, mirroring {@link parseMinerGoalSpecContent}.
+ */
+export function parseFleetRunManifestContent(content: string | null | undefined): ParsedFleetRunManifest {
+  if (content === undefined || content === null || content.trim() === "") return emptyFleetRunManifest();
+  if (utf8ByteLength(content) > MAX_FLEET_RUN_MANIFEST_BYTES) {
+    return emptyFleetRunManifest([
+      `FleetRunManifest content exceeded ${MAX_FLEET_RUN_MANIFEST_BYTES} bytes; ignoring it and falling back to safe defaults.`,
+    ]);
+  }
+  const trimmed = content.trim();
+  const looksLikeJson = trimmed.startsWith("{") || trimmed.startsWith("[");
+  let parsed: unknown;
+  try {
+    parsed = looksLikeJson ? JSON.parse(trimmed) : parseYaml(trimmed);
+  } catch {
+    return emptyFleetRunManifest([
+      looksLikeJson
+        ? "FleetRunManifest content was not valid JSON; ignoring it and falling back to safe defaults."
+        : "FleetRunManifest content was not valid YAML; ignoring it and falling back to safe defaults.",
+    ]);
+  }
+  return parseFleetRunManifest(parsed);
+}
diff --git a/packages/gittensory-engine/src/index.ts b/packages/gittensory-engine/src/index.ts
index 617d471a1c..28adfb66e1 100644
--- a/packages/gittensory-engine/src/index.ts
+++ b/packages/gittensory-engine/src/index.ts
@@ -197,6 +197,14 @@ export {
   type MinerIssueDiscoveryPolicy,
   type ParsedMinerGoalSpec,
 } from "./miner-goal-spec.js";
+export {
+  DEFAULT_FLEET_RUN_MANIFEST,
+  parseFleetRunManifest,
+  parseFleetRunManifestContent,
+  type FleetRunManifest,
+  type FleetRunManifestRepo,
+  type ParsedFleetRunManifest,
+} from "./fleet-run-manifest.js";
 export {
   computeMetadataLaneFit,
   computeMinerGoalLaneFit,
diff --git a/packages/gittensory-miner/docs/fleet-run-manifest.md b/packages/gittensory-miner/docs/fleet-run-manifest.md
new file mode 100644
index 0000000000..cf2b371a1a
--- /dev/null
+++ b/packages/gittensory-miner/docs/fleet-run-manifest.md
@@ -0,0 +1,50 @@
+# Fleet run-manifest
+
+The **fleet run-manifest** is the top-level config a *fleet operator* authors to run the miner across many repos
+at once: it declares which repos are in scope for a fleet run and how a finite worktree/concurrency budget is
+split between them. It is parsed by `parseFleetRunManifestContent` / `parseFleetRunManifest` in
+`@jsonbored/gittensory-engine` (`packages/gittensory-engine/src/fleet-run-manifest.ts`).
+
+It is **not** the same file as `.gittensory-miner.yml` (see [`miner-goal-spec.md`](./miner-goal-spec.md)) — the
+naming is easy to conflate. Same tolerant-parser convention (every field optional, unknown keys ignored, a
+malformed field degrades to a documented default with a warning rather than throwing), but the opposite author
+and the opposite direction of intent:
+
+| | `.gittensory-miner.yml` (goal spec) | fleet run-manifest |
+|---|---|---|
+| **Author** | a target repo's maintainer | the miner (fleet) operator |
+| **Lives in** | the target repo | the operator's fleet-run config |
+| **Direction** | how this one repo wants to be approached | which repos to work across, and how to split the budget |
+| **Scope** | one repo | many repos in one run |
+| **Key fields** | `minerEnabled`, `wantedPaths`, `blockedPaths`, `preferredLabels`, `blockedLabels`, `maxConcurrentClaims`, `issueDiscoveryPolicy` | `repos` (each `owner/repo` + `maxConcurrentWorktrees`), `totalConcurrentWorktrees` |
+
+## Schema
+
+Every field is optional; unknown keys are ignored; a malformed field falls back to a documented default with a
+warning rather than hard-failing the run.
+
+- **`repos`** — a list of target repos. Each entry is either a bare `"owner/repo"` string (uses the default
+  per-repo budget) or a `{ repoFullName, maxConcurrentWorktrees }` mapping. Invalid or duplicate entries are
+  skipped with a warning. `repoFullName` is a canonical `owner/repo`, compatible with `opportunity-fanout.js`'s
+  target list. Default: `[]`.
+- **`repos[].maxConcurrentWorktrees`** — max concurrent worktrees (in-flight attempts) for that repo. A positive
+  integer (floored; sub-1 falls back to the default). Default: `1`.
+- **`totalConcurrentWorktrees`** — total concurrent worktrees across the whole fleet, regardless of per-repo
+  budgets. A positive integer. Default: `1`.
+
+## Wiring
+
+This module produces only the parsed, typed manifest. Driving the fleet concurrency allocator from it is the
+allocator's concern (sibling `feat(miner-concurrency): add git-worktree-per-attempt allocator` issue), and the
+cross-repo `portfolio-queue.js` backlog reads the same repo list — both *consume* this manifest; neither wiring
+lives here.
+
+## Example (`fleet-run.yml`)
+
+```yaml
+totalConcurrentWorktrees: 4
+repos:
+  - owner/repo-a
+  - repoFullName: owner/repo-b
+    maxConcurrentWorktrees: 2
+```
diff --git a/test/unit/fleet-run-manifest-parser.test.ts b/test/unit/fleet-run-manifest-parser.test.ts
new file mode 100644
index 0000000000..667e1d68d0
--- /dev/null
+++ b/test/unit/fleet-run-manifest-parser.test.ts
@@ -0,0 +1,110 @@
+import { describe, expect, it } from "vitest";
+import {
+  DEFAULT_FLEET_RUN_MANIFEST,
+  parseFleetRunManifest,
+  parseFleetRunManifestContent,
+} from "../../packages/gittensory-engine/src/index";
+
+describe("FleetRunManifest parser (#4299)", () => {
+  it("re-exports the parser API from the engine barrel", () => {
+    expect(typeof parseFleetRunManifest).toBe("function");
+    expect(typeof parseFleetRunManifestContent).toBe("function");
+  });
+
+  it("treats missing raw input as an absent safe-default manifest", () => {
+    for (const raw of [undefined, null]) {
+      expect(parseFleetRunManifest(raw)).toEqual({ present: false, manifest: DEFAULT_FLEET_RUN_MANIFEST, warnings: [] });
+    }
+  });
+
+  it.each(["not a mapping", ["still", "not", "a", "mapping"]])("degrades a malformed top-level value to safe defaults: %j", (raw) => {
+    const parsed = parseFleetRunManifest(raw);
+    expect(parsed.present).toBe(false);
+    expect(parsed.manifest).toEqual(DEFAULT_FLEET_RUN_MANIFEST);
+    expect(parsed.warnings.join(" ")).toMatch(/must be a mapping/i);
+  });
+
+  it("treats an all-default mapping as absent (no non-default fields)", () => {
+    const parsed = parseFleetRunManifest({ repos: [], totalConcurrentWorktrees: 1 });
+    expect(parsed.present).toBe(false);
+    expect(parsed.warnings.join(" ")).toMatch(/no recognized non-default fields/i);
+  });
+
+  it("normalizes string + object repo entries, floors budgets, dedupes, and skips invalid entries", () => {
+    const parsed = parseFleetRunManifest({
+      repos: [
+        "owner/a", // string → default budget 1
+        { repoFullName: "owner/b", maxConcurrentWorktrees: 3.9 }, // object → floored to 3
+        { repoFullName: "owner/b", maxConcurrentWorktrees: 2 }, // duplicate → skipped
+        "owner/a", // duplicate → skipped
+        "not-a-repo", // invalid name (no slash) → skipped
+        "owner/repo/extra", // invalid name (too many slashes) → skipped
+        "/only-repo", // invalid name (empty owner) → skipped
+        { repoFullName: "no-slash" }, // invalid name → skipped
+        { repoFullName: 123 }, // non-string repoFullName → skipped
+        { repoFullName: "owner/c", maxConcurrentWorktrees: "x" }, // non-numeric budget → default 1 + warning
+        42, // non-string / non-mapping → skipped
+      ],
+      totalConcurrentWorktrees: 5,
+    });
+    expect(parsed.present).toBe(true);
+    expect(parsed.manifest.repos).toEqual([
+      { repoFullName: "owner/a", maxConcurrentWorktrees: 1 },
+      { repoFullName: "owner/b", maxConcurrentWorktrees: 3 },
+      { repoFullName: "owner/c", maxConcurrentWorktrees: 1 },
+    ]);
+    expect(parsed.manifest.totalConcurrentWorktrees).toBe(5);
+    const w = parsed.warnings.join(" ");
+    expect(w).toMatch(/duplicate entry for owner\/b/);
+    expect(w).toMatch(/invalid "owner\/repo" name/);
+    expect(w).toMatch(/non-string, non-mapping/);
+    expect(w).toMatch(/"maxConcurrentWorktrees" must be a positive whole number/);
+  });
+
+  it("falls a non-list repos field and a sub-1 total budget back to defaults with warnings", () => {
+    const parsed = parseFleetRunManifest({ repos: "owner/a", totalConcurrentWorktrees: 0 });
+    expect(parsed.manifest.repos).toEqual([]);
+    expect(parsed.manifest.totalConcurrentWorktrees).toBe(1);
+    const w = parsed.warnings.join(" ");
+    expect(w).toMatch(/"repos" must be a list/);
+    expect(w).toMatch(/"totalConcurrentWorktrees" must be >= 1/);
+  });
+
+  it("warns on a non-numeric total budget", () => {
+    const parsed = parseFleetRunManifest({ repos: ["owner/a"], totalConcurrentWorktrees: "lots" });
+    expect(parsed.present).toBe(true);
+    expect(parsed.manifest.totalConcurrentWorktrees).toBe(1);
+    expect(parsed.warnings.join(" ")).toMatch(/"totalConcurrentWorktrees" must be a positive whole number/);
+  });
+
+  it("caps the repo list and warns when it is exceeded", () => {
+    const many = Array.from({ length: 502 }, (_, i) => `owner/r${i}`);
+    const parsed = parseFleetRunManifest({ repos: many });
+    expect(parsed.manifest.repos).toHaveLength(500);
+    expect(parsed.warnings.join(" ")).toMatch(/exceeded 500 entries/);
+  });
+
+  it("parseFleetRunManifestContent: blank / missing content is an absent manifest", () => {
+    for (const content of [undefined, null, "", "   "]) {
+      expect(parseFleetRunManifestContent(content)).toEqual({ present: false, manifest: DEFAULT_FLEET_RUN_MANIFEST, warnings: [] });
+    }
+  });
+
+  it("parseFleetRunManifestContent: parses YAML and JSON, over-limit + malformed degrade with a warning", () => {
+    const yaml = parseFleetRunManifestContent("repos:\n  - owner/a\n  - repoFullName: owner/b\n    maxConcurrentWorktrees: 2\ntotalConcurrentWorktrees: 4\n");
+    expect(yaml.present).toBe(true);
+    expect(yaml.manifest.repos.map((r) => r.repoFullName)).toEqual(["owner/a", "owner/b"]);
+    expect(yaml.manifest.totalConcurrentWorktrees).toBe(4);
+
+    const json = parseFleetRunManifestContent('{"repos":["owner/a"],"totalConcurrentWorktrees":3}');
+    expect(json.present).toBe(true);
+    expect(json.manifest.totalConcurrentWorktrees).toBe(3);
+
+    // multi-byte content (still under the byte limit) exercises the byte-length accounting.
+    expect(parseFleetRunManifestContent("totalConcurrentWorktrees: 2 # é中\u{1F600}").manifest.totalConcurrentWorktrees).toBe(2);
+
+    expect(parseFleetRunManifestContent('{"repos": [invalid json}').warnings.join(" ")).toMatch(/not valid JSON/);
+    expect(parseFleetRunManifestContent("repos:\n  - : :\n :bad").warnings.join(" ")).toMatch(/not valid YAML/);
+    expect(parseFleetRunManifestContent("x".repeat(65_537)).warnings.join(" ")).toMatch(/exceeded 65536 bytes/);
+  });
+});