diff --git a/tools/github/poll-pr-gate.test.ts b/tools/github/poll-pr-gate.test.ts
new file mode 100644
index 000000000..2ff664ec8
--- /dev/null
+++ b/tools/github/poll-pr-gate.test.ts
@@ -0,0 +1,162 @@
+// poll-pr-gate.test.ts — fixture-driven DST coverage for the v1 single-PR
+// gate query. Closes the v1 gap: task #355 promised "with fixtures" but
+// the fixture set under tools/github/fixtures/ landed without a test
+// runner exercising it. This file makes each fixture's expected gate
+// classification a load-bearing assertion.
+//
+// Each fixture name encodes the scenario:
+//   - clean-armed-auto-merge.json  → CLEAN gate, autoMerge: armed
+//   - blocked-by-threads.json      → BLOCKED gate, unresolvedThreads > 0
+//   - dirty-auto-merge-armed.json  → DIRTY gate, nextAction: rebase
+//   - behind-needs-rebase.json     → DIRTY gate (BEHIND collapses to DIRTY)
+//   - non-required-failure-warning.json → required-vs-non-required hardening
+//   - status-context-error.json    → StatusContext ERROR maps to BLOCKED
+//   - unknown-mergeability-pending-recompute.json → UNKNOWN handling
+//
+// The test asserts the v1 hardening contracts (per peer-review 2026-04-30):
+//   1. Required-only check failures gate the merge; non-required failures
+//      surface as warnings and don't change nextAction.
+//   2. BEHIND mergeStateStatus collapses to DIRTY (rebase needed).
+//   3. CLOSED-without-merge is terminal (nextAction: none).
+//   4. unresolvedThreads count drives resolve-threads classification.
+//
+// Runs via `bun test tools/github/poll-pr-gate.test.ts`. Zero gh
+// spawns, zero network — all data comes from on-disk fixture JSON.
+
+import { describe, expect, test } from "bun:test";
+import { dirname, resolve } from "node:path";
+import { fileURLToPath } from "node:url";
+import { buildReport, loadFixture, type GateReport } from "./poll-pr-gate";
+
+const FIXTURES_DIR = resolve(
+  dirname(fileURLToPath(import.meta.url)),
+  "fixtures",
+);
+
+function classifyFixture(name: string): GateReport {
+  return buildReport(loadFixture(resolve(FIXTURES_DIR, name)));
+}
+
+describe("clean-armed-auto-merge fixture", () => {
+  // Canonical happy path — CI green, auto-merge armed, no threads.
+  // The loop's verify-merge target.
+  test("classifies as CLEAN with auto-merge armed", () => {
+    const report = classifyFixture("clean-armed-auto-merge.json");
+    expect(report.gate).toBe("CLEAN");
+    expect(report.autoMerge).toBe("armed");
+    expect(report.unresolvedThreads).toBe(0);
+    expect(report.requiredChecks.failed).toBe(0);
+    expect(report.nextAction).toBe("none");
+  });
+});
+
+describe("blocked-by-threads fixture", () => {
+  // The exact scenario the BLOCKED-with-green-CI wake-time bullet
+  // targets: CI green, auto-merge state, but unresolved threads
+  // gate the merge. The discriminating signal is unresolvedThreads > 0.
+  test("classifies as BLOCKED with resolve-threads next action", () => {
+    const report = classifyFixture("blocked-by-threads.json");
+    expect(report.gate).toBe("BLOCKED");
+    expect(report.unresolvedThreads).toBeGreaterThan(0);
+    expect(report.requiredChecks.failed).toBe(0);
+    expect(report.nextAction).toBe("resolve-threads");
+  });
+});
+
+describe("dirty-auto-merge-armed fixture", () => {
+  test("classifies as DIRTY with rebase next action", () => {
+    const report = classifyFixture("dirty-auto-merge-armed.json");
+    expect(report.gate).toBe("DIRTY");
+    expect(report.nextAction).toBe("rebase");
+  });
+});
+
+describe("behind-needs-rebase fixture", () => {
+  // BEHIND mergeStateStatus collapses to DIRTY per Copilot P0 from
+  // the v1 hardening — both states need a rebase before merge.
+  test("BEHIND collapses to DIRTY", () => {
+    const report = classifyFixture("behind-needs-rebase.json");
+    expect(report.gate).toBe("DIRTY");
+    expect(report.nextAction).toBe("rebase");
+  });
+});
+
+describe("non-required-failure-warning fixture", () => {
+  // The v1 hardening's load-bearing test case: a non-required check
+  // failed, but required checks all pass. The contract is that this
+  // does NOT fail the gate — it surfaces as a warning, and nextAction
+  // proceeds based on required-only state.
+  test("non-required failure produces warning, not gate failure", () => {
+    const report = classifyFixture("non-required-failure-warning.json");
+    expect(report.requiredChecks.failed).toBe(0);
+    expect(report.warnings.length).toBeGreaterThan(0);
+    // Warnings carry the "non-required check failed:" prefix for
+    // grep-friendly downstream filtering.
+    expect(report.warnings[0]).toMatch(/non-required check failed:/);
+    expect(report.nextAction).not.toBe("fix-failed-checks");
+  });
+});
+
+describe("status-context-error fixture", () => {
+  // StatusContext-class checks (not CheckRun) expose state instead
+  // of status/conclusion. ERROR + FAILURE both block; pending states
+  // (PENDING, EXPECTED) are still in-progress. Per Codex P1 review.
+  test("StatusContext ERROR is treated as a blocking failure", () => {
+    const report = classifyFixture("status-context-error.json");
+    // The fixture has at least one ERROR-state status context that
+    // should normalize to a blocking conclusion.
+    expect(report.requiredChecks.failed + report.checks.failed).toBeGreaterThan(0);
+  });
+});
+
+describe("unknown-mergeability-pending-recompute fixture", () => {
+  // GitHub computes mergeability asynchronously after a push;
+  // there's a window where mergeStateStatus is UNKNOWN. The script
+  // surfaces this honestly rather than guessing.
+  test("UNKNOWN mergeStateStatus surfaces as UNKNOWN gate", () => {
+    const report = classifyFixture("unknown-mergeability-pending-recompute.json");
+    expect(report.gate).toBe("UNKNOWN");
+  });
+});
+
+describe("buildReport contracts (cross-fixture invariants)", () => {
+  const fixtures = [
+    "clean-armed-auto-merge.json",
+    "blocked-by-threads.json",
+    "dirty-auto-merge-armed.json",
+    "behind-needs-rebase.json",
+    "non-required-failure-warning.json",
+    "status-context-error.json",
+    "unknown-mergeability-pending-recompute.json",
+  ];
+
+  test.each(fixtures)("%s — checks counts are non-negative integers", (name) => {
+    const report = classifyFixture(name);
+    for (const k of ["ok", "inProgress", "pending", "failed"] as const) {
+      expect(report.checks[k]).toBeGreaterThanOrEqual(0);
+      expect(Number.isInteger(report.checks[k])).toBe(true);
+      expect(report.requiredChecks[k]).toBeGreaterThanOrEqual(0);
+      expect(Number.isInteger(report.requiredChecks[k])).toBe(true);
+    }
+  });
+
+  test.each(fixtures)("%s — requiredChecks counts are bounded by total checks", (name) => {
+    const report = classifyFixture(name);
+    // Required checks are a subset of all checks. Each per-status
+    // count must be <= the total per-status count, since a required
+    // check is also a check.
+    for (const k of ["ok", "inProgress", "pending", "failed"] as const) {
+      expect(report.requiredChecks[k]).toBeLessThanOrEqual(report.checks[k]);
+    }
+  });
+
+  test.each(fixtures)("%s — nextAction is consistent with gate state", (name) => {
+    const report = classifyFixture(name);
+    if (report.gate === "DIRTY") expect(report.nextAction).toBe("rebase");
+    if (report.state === "MERGED") expect(report.nextAction).toBe("verify-merge");
+    if (report.state === "CLOSED") expect(report.nextAction).toBe("none");
+    if (report.requiredChecks.failed > 0) {
+      expect(report.nextAction).toBe("fix-failed-checks");
+    }
+  });
+});
diff --git a/tools/github/poll-pr-gate.ts b/tools/github/poll-pr-gate.ts
index bfd99d113..3c678fccf 100755
--- a/tools/github/poll-pr-gate.ts
+++ b/tools/github/poll-pr-gate.ts
@@ -76,7 +76,7 @@ interface ReviewThreadNode {
   isResolved: boolean;
 }
 
-interface PullRequestData {
+export interface PullRequestData {
   number: number;
   state: string;
   mergeStateStatus: string;
@@ -97,14 +97,14 @@ interface PullRequestData {
   requiredCheckNames?: string[];
 }
 
-interface CheckCounts {
+export interface CheckCounts {
   ok: number;
   inProgress: number;
   pending: number;
   failed: number;
 }
 
-interface GateReport {
+export interface GateReport {
   number: number;
   state: string;
   gate: GateState;
@@ -229,7 +229,7 @@ function nextAction(report: Omit<GateReport, "nextAction">): NextAction {
   return "none";
 }
 
-function buildReport(pr: PullRequestData): GateReport {
+export function buildReport(pr: PullRequestData): GateReport {
   const rollup = pr.statusCheckRollup ?? [];
   const checks = classifyChecks(rollup);
   // Tri-state on requiredCheckNames (v1 hardening per peer review):
@@ -464,7 +464,7 @@ function normalizeRollup(rollup: unknown[]): CheckRollupItem[] {
   });
 }
 
-function loadFixture(path: string): PullRequestData {
+export function loadFixture(path: string): PullRequestData {
   let raw: PullRequestData;
   try {
     raw = JSON.parse(readFileSync(path, "utf8")) as PullRequestData;