diff --git a/packages/gittensory-miner/lib/claim-adjudication.d.ts b/packages/gittensory-miner/lib/claim-adjudication.d.ts
new file mode 100644
index 0000000000..e195bc19aa
--- /dev/null
+++ b/packages/gittensory-miner/lib/claim-adjudication.d.ts
@@ -0,0 +1,21 @@
+/** An observed claim on an issue: a PR/claimant number plus when it claimed the linked issue (if known). */
+export type ObservedClaim = {
+  number: number;
+  claimedAt?: string | null | undefined;
+};
+
+/** The engine `DuplicateClaimMember` shape this module bridges an {@link ObservedClaim} to. */
+export type ClaimMember = {
+  number: number;
+  linkedIssueClaimedAt: string | null;
+};
+
+/** The adjudication result: the go/no-go `isWinner`, plus a DISPLAY-only `winnerNumber` (null when not determinable). */
+export type ClaimAdjudication = {
+  isWinner: boolean;
+  winnerNumber: number | null;
+};
+
+export function toClaimMember(claim: ObservedClaim): ClaimMember;
+
+export function adjudicateSoftClaim(self: ObservedClaim, competing?: readonly ObservedClaim[]): ClaimAdjudication;
diff --git a/packages/gittensory-miner/lib/claim-adjudication.js b/packages/gittensory-miner/lib/claim-adjudication.js
new file mode 100644
index 0000000000..fe99581bd8
--- /dev/null
+++ b/packages/gittensory-miner/lib/claim-adjudication.js
@@ -0,0 +1,36 @@
+// Soft-claim adjudication (#4291). Decides which of several miners claiming the same issue proceeds, by REUSING the
+// maintainer-side duplicate-cluster election (`isDuplicateClusterWinnerByClaim` from @jsonbored/gittensory-engine)
+// rather than reimplementing it — so the miner and the maintainer gate agree on exactly one winner by construction.
+//
+// The local claim ledger is 100% client-side and cannot see other miners' claims, so the competing-claim signal
+// must come from something publicly observable: the OPEN PRs that link the same issue (an issue with several open
+// PRs linking it IS the public signal of a contested claim). The caller assembles that set — exactly like the
+// maintainer-side callers in src/ do — and passes it here.
+import { isDuplicateClusterWinnerByClaim, resolveDuplicateClusterWinnerNumber } from "@jsonbored/gittensory-engine";
+
+/**
+ * Map an observed claim record to the engine's `DuplicateClaimMember`. The field names deliberately DIFFER — the
+ * local ledger / observed data expose `claimedAt`, the engine election reads `linkedIssueClaimedAt` — so the bridge
+ * is explicit (they are not interchangeable by accident of naming). `createdAt` is intentionally omitted: the
+ * election ignores it (an older PR can claim a linked issue later by editing its body). Pure.
+ */
+export function toClaimMember(claim) {
+  return { number: claim.number, linkedIssueClaimedAt: claim.claimedAt ?? null };
+}
+
+/**
+ * Adjudicate whether THIS miner's soft-claim wins a contested issue. `self` is this miner's claim and `competing`
+ * is the publicly-observable set of OTHER open PRs linking the same issue; each entry is `{ number, claimedAt }`.
+ * Returns the go/no-go `isWinner` (driven ONLY by `isDuplicateClusterWinnerByClaim`) plus a DISPLAY-only
+ * `winnerNumber` (from `resolveDuplicateClusterWinnerNumber`, for surfacing "you lost this claim to PR #N" to the
+ * operator — never for the decision). Pure — no IO. Fail-closed: a missing/sparse claim time loses; the winner is
+ * `null` when the ordering is too sparse to be sure (it never guesses). An empty `competing` list ⇒ trivial winner.
+ */
+export function adjudicateSoftClaim(self, competing = []) {
+  const selfMember = toClaimMember(self);
+  const siblings = competing.map(toClaimMember);
+  return {
+    isWinner: isDuplicateClusterWinnerByClaim(selfMember, siblings),
+    winnerNumber: resolveDuplicateClusterWinnerNumber(selfMember, siblings),
+  };
+}
diff --git a/packages/gittensory-miner/package.json b/packages/gittensory-miner/package.json
index 7aba5d88d3..a810c4cc3a 100644
--- a/packages/gittensory-miner/package.json
+++ b/packages/gittensory-miner/package.json
@@ -31,7 +31,7 @@
     "lib"
   ],
   "scripts": {
-    "build": "node --check bin/gittensory-miner.js && node --check lib/version.js && node --check lib/cli.js && node --check lib/deny-check.js && node --check lib/run-state-cli.js && node --check lib/update-check.js && node --check lib/opportunity-fanout.js && node --check lib/ci-poller.js && node --check lib/run-state.js && node --check lib/deny-hooks.js && node --check lib/event-ledger.js && node --check lib/event-ledger-cli.js && node --check lib/claim-ledger.js && node --check lib/claim-ledger-expiry.js && node --check lib/claim-ledger-cli.js && node --check lib/portfolio-queue.js && node --check lib/portfolio-queue-cli.js && node --check lib/portfolio-discovery.js && node --check lib/opportunity-ranker.js && node --check lib/plan-store.js && node --check lib/plan-store-cli.js && node --check lib/rejection-templates.js && node --check lib/governor-ledger.js && node --check lib/governor-ledger-cli.js && node --check lib/manage-status.js && node --check lib/manage-poll.js && node --check lib/status.js && node --check lib/laptop-init.js && node --check lib/replay-objective-anchor.js && node --check lib/replay-task-generation.js && node --check lib/calibration-types.js && node --check lib/calibration.js"
+    "build": "node --check bin/gittensory-miner.js && node --check lib/version.js && node --check lib/cli.js && node --check lib/deny-check.js && node --check lib/run-state-cli.js && node --check lib/update-check.js && node --check lib/opportunity-fanout.js && node --check lib/ci-poller.js && node --check lib/run-state.js && node --check lib/deny-hooks.js && node --check lib/event-ledger.js && node --check lib/event-ledger-cli.js && node --check lib/claim-ledger.js && node --check lib/claim-ledger-expiry.js && node --check lib/claim-ledger-cli.js && node --check lib/claim-adjudication.js && node --check lib/portfolio-queue.js && node --check lib/portfolio-queue-cli.js && node --check lib/portfolio-discovery.js && node --check lib/opportunity-ranker.js && node --check lib/plan-store.js && node --check lib/plan-store-cli.js && node --check lib/rejection-templates.js && node --check lib/governor-ledger.js && node --check lib/governor-ledger-cli.js && node --check lib/manage-status.js && node --check lib/manage-poll.js && node --check lib/status.js && node --check lib/laptop-init.js && node --check lib/replay-objective-anchor.js && node --check lib/replay-task-generation.js && node --check lib/calibration-types.js && node --check lib/calibration.js"
   },
   "dependencies": {
     "@jsonbored/gittensory-engine": ">=0.1.0 <1.0.0"
diff --git a/test/unit/miner-claim-adjudication.test.ts b/test/unit/miner-claim-adjudication.test.ts
new file mode 100644
index 0000000000..8d062f5dcf
--- /dev/null
+++ b/test/unit/miner-claim-adjudication.test.ts
@@ -0,0 +1,48 @@
+import { describe, expect, it } from "vitest";
+import { adjudicateSoftClaim, toClaimMember } from "../../packages/gittensory-miner/lib/claim-adjudication.js";
+
+describe("miner soft-claim adjudication (#4291)", () => {
+  it("toClaimMember maps claimedAt → linkedIssueClaimedAt (the field names deliberately differ)", () => {
+    expect(toClaimMember({ number: 7, claimedAt: "2026-01-01T00:00:00Z" })).toEqual({
+      number: 7,
+      linkedIssueClaimedAt: "2026-01-01T00:00:00Z",
+    });
+    // a missing claim time maps to null (fail-closed input), not undefined
+    expect(toClaimMember({ number: 7 })).toEqual({ number: 7, linkedIssueClaimedAt: null });
+  });
+
+  it("this miner WINS when it claimed earliest", () => {
+    const result = adjudicateSoftClaim(
+      { number: 5, claimedAt: "2026-01-01T00:00:00Z" },
+      [{ number: 6, claimedAt: "2026-01-02T00:00:00Z" }],
+    );
+    expect(result).toEqual({ isWinner: true, winnerNumber: 5 });
+  });
+
+  it("this miner LOSES to an earlier competing claim, and the winner is surfaced (display only)", () => {
+    const result = adjudicateSoftClaim(
+      { number: 6, claimedAt: "2026-01-02T00:00:00Z" },
+      [{ number: 5, claimedAt: "2026-01-01T00:00:00Z" }],
+    );
+    expect(result).toEqual({ isWinner: false, winnerNumber: 5 });
+  });
+
+  it("no competing claim ⇒ trivial winner (even with an unknown claim time)", () => {
+    expect(adjudicateSoftClaim({ number: 9, claimedAt: "2026-03-01T00:00:00Z" }, [])).toEqual({
+      isWinner: true,
+      winnerNumber: 9,
+    });
+    expect(adjudicateSoftClaim({ number: 9 }, [])).toEqual({ isWinner: true, winnerNumber: 9 });
+  });
+
+  it("fail-closed: a missing/sparse claim time loses AND yields no guessed winner", () => {
+    // this miner has no observed claim time → cannot be elected, and (because the election needs BOTH members'
+    // times to order them) no winner is determinable either — the engine never guesses when data is too sparse.
+    expect(adjudicateSoftClaim({ number: 6 }, [{ number: 5, claimedAt: "2026-01-01T00:00:00Z" }])).toEqual({
+      isWinner: false,
+      winnerNumber: null,
+    });
+    // BOTH sides sparse → still no determinable winner
+    expect(adjudicateSoftClaim({ number: 6 }, [{ number: 5 }])).toEqual({ isWinner: false, winnerNumber: null });
+  });
+});