diff --git a/desktop/src/features/providers/lib/providerAvailability.test.mjs b/desktop/src/features/providers/lib/providerAvailability.test.mjs
new file mode 100644
index 00000000000..c862a775cd5
--- /dev/null
+++ b/desktop/src/features/providers/lib/providerAvailability.test.mjs
@@ -0,0 +1,120 @@
+import assert from "node:assert/strict";
+import test from "node:test";
+
+import {
+  canQuoteJobs,
+  deriveProviderAvailability,
+  providerAvailabilityCaption,
+  refreshIntervalForLease,
+} from "./providerAvailability.ts";
+
+/**
+ * Covers buzz#84's freshness invariant (toon-meta#262 decision 12): never
+ * advertise a provider as available for longer than it stays routable on the
+ * connector, and a dropped session must cost reachability only — never the
+ * channel, balance, nonce position or reputation. Pure-function tests in the
+ * `huddleFeeQuote` mold — no DOM, no live connector.
+ */
+
+test("the refresh cadence mirrors the mesh's 45s/120s reference ratio", () => {
+  assert.equal(refreshIntervalForLease(120_000), 45_000);
+  assert.equal(refreshIntervalForLease(60_000), 22_500);
+});
+
+test("advertising off reads as unadvertised regardless of session state", () => {
+  const state = deriveProviderAvailability({
+    advertisingEnabled: false,
+    sessionConnected: true,
+    lastAdvertisedAtMs: 1_000,
+    nowMs: 1_000,
+    sessionLeaseTtlMs: 120_000,
+  });
+
+  assert.deepEqual(state, { kind: "unadvertised" });
+  assert.equal(canQuoteJobs(state), false);
+});
+
+test("advertising on with no publish yet is pending, not available", () => {
+  const state = deriveProviderAvailability({
+    advertisingEnabled: true,
+    sessionConnected: true,
+    lastAdvertisedAtMs: null,
+    nowMs: 1_000,
+    sessionLeaseTtlMs: 120_000,
+  });
+
+  assert.deepEqual(state, { kind: "pending" });
+  assert.equal(canQuoteJobs(state), false);
+});
+
+test("a live, fresh advertisement is available and reports its next refresh and expiry", () => {
+  const state = deriveProviderAvailability({
+    advertisingEnabled: true,
+    sessionConnected: true,
+    lastAdvertisedAtMs: 100_000,
+    nowMs: 110_000,
+    sessionLeaseTtlMs: 120_000,
+  });
+
+  assert.deepEqual(state, {
+    kind: "available",
+    refreshDueAtMs: 145_000,
+    expiresAtMs: 220_000,
+  });
+  assert.equal(canQuoteJobs(state), true);
+});
+
+test("a dropped session reads as stale immediately, mid-lease — offline costs reachability only", () => {
+  const state = deriveProviderAvailability({
+    advertisingEnabled: true,
+    sessionConnected: false,
+    lastAdvertisedAtMs: 100_000,
+    nowMs: 100_500,
+    sessionLeaseTtlMs: 120_000,
+  });
+
+  assert.deepEqual(state, { kind: "stale" });
+  assert.equal(canQuoteJobs(state), false);
+});
+
+test("a missed refresh past the lease reads as stale — never advertise longer than routable", () => {
+  const state = deriveProviderAvailability({
+    advertisingEnabled: true,
+    sessionConnected: true,
+    lastAdvertisedAtMs: 0,
+    nowMs: 120_000,
+    sessionLeaseTtlMs: 120_000,
+  });
+
+  assert.deepEqual(state, { kind: "stale" });
+  assert.equal(canQuoteJobs(state), false);
+});
+
+test("a lease boundary reads as fresh right up to, but not including, expiry", () => {
+  const state = deriveProviderAvailability({
+    advertisingEnabled: true,
+    sessionConnected: true,
+    lastAdvertisedAtMs: 0,
+    nowMs: 119_999,
+    sessionLeaseTtlMs: 120_000,
+  });
+
+  assert.equal(state.kind, "available");
+});
+
+test("caption text is honest and non-null only where there is something to say", () => {
+  assert.equal(providerAvailabilityCaption({ kind: "unadvertised" }), null);
+  assert.match(providerAvailabilityCaption({ kind: "pending" }), /Publishing/);
+  assert.match(
+    providerAvailabilityCaption({
+      kind: "available",
+      refreshDueAtMs: 0,
+      expiresAtMs: 0,
+    }),
+    /available/i,
+  );
+  assert.match(
+    providerAvailabilityCaption({ kind: "stale" }),
+    /not currently reachable/i,
+  );
+});
diff --git a/desktop/src/features/providers/lib/providerAvailability.ts b/desktop/src/features/providers/lib/providerAvailability.ts
new file mode 100644
index 00000000000..c0926df6b71
--- /dev/null
+++ b/desktop/src/features/providers/lib/providerAvailability.ts
@@ -0,0 +1,122 @@
+/**
+ * The provider-surface freshness invariant (buzz#84, toon-meta#262 decision
+ * 12): "the socket is the lease." A route exists exactly as long as the
+ * authenticated connector session, so an advertisement must never claim
+ * availability for longer than that session stays routable — or a buyer can
+ * pay for a job that cannot land.
+ *
+ * Two failure directions are asymmetric and the code below only ever errs
+ * toward the cheap one: reading a live provider as unavailable costs a
+ * little missed work; reading an unreachable one as available costs a buyer
+ * a rejected payment. A dropped session therefore reads as `stale`
+ * immediately, without waiting out the lease — and going offline costs
+ * reachability only, never the channel, balance, nonce position or
+ * reputation (nothing here touches any of those).
+ *
+ * `sessionLeaseTtlMs` is a caller-supplied parameter, not a constant defined
+ * here: connector#698 exports it as `SESSION_LEASE_BACKSTOP_TTL` and its own
+ * doc comment says this ticket should read it from there rather than
+ * duplicating the value. As of this writing that export is not yet present
+ * in any published `@toon-protocol/client`/`@toon-protocol/connector`
+ * release this repo can pin, so there is no live caller yet — this module is
+ * ready for one once the value is available, mirroring the
+ * `agentNetworkFlow.ts` precedent for shipping pure domain logic ahead of
+ * its data source.
+ */
+
+/** What the provider surface knows about its own current advertisement. */
+export type ProviderAvailability =
+  /** The owner has not turned provider advertising on for this agent. */
+  | { kind: "unadvertised" }
+  /** Advertising is on, but no publish has landed yet — nothing to quote from. */
+  | { kind: "pending" }
+  /** Advertised, session live, and inside the connector's lease window. */
+  | { kind: "available"; refreshDueAtMs: number; expiresAtMs: number }
+  /** Session dropped, or the lease lapsed without a refresh — do not quote. */
+  | { kind: "stale" };
+
+/**
+ * The mesh's own reference cadence: `mesh_llm/coordinator.rs`
+ * `STATUS_PUBLISH_INTERVAL` republishes every 45s within the 120s freshness
+ * window `mesh_llm/discovery.rs` `STATUS_FRESHNESS_SECS` allows.
+ */
+const MESH_REFRESH_INTERVAL_SECS = 45;
+const MESH_FRESHNESS_WINDOW_SECS = 120;
+
+/**
+ * How long after publishing an advertisement to refresh it, given the
+ * connector's session lease. Scaled at the mesh's own ratio so a refresh
+ * always lands well inside the lease rather than racing its edge.
+ */
+export function refreshIntervalForLease(sessionLeaseTtlMs: number): number {
+  return Math.floor(
+    (sessionLeaseTtlMs * MESH_REFRESH_INTERVAL_SECS) /
+      MESH_FRESHNESS_WINDOW_SECS,
+  );
+}
+
+/**
+ * Derive whether this agent's provider listing is currently honest to show
+ * as available, never throwing and never guessing in the buyer's favor.
+ */
+export function deriveProviderAvailability(input: {
+  /** Whether the owner has turned provider advertising on for this agent. */
+  advertisingEnabled: boolean;
+  /** Whether the connector session (the lease) is currently up. */
+  sessionConnected: boolean;
+  /** When the advertisement was last published, or null if never. */
+  lastAdvertisedAtMs: number | null;
+  nowMs: number;
+  /** The connector's session lease TTL — see the module doc for its source. */
+  sessionLeaseTtlMs: number;
+}): ProviderAvailability {
+  const {
+    advertisingEnabled,
+    sessionConnected,
+    lastAdvertisedAtMs,
+    nowMs,
+    sessionLeaseTtlMs,
+  } = input;
+
+  if (!advertisingEnabled) return { kind: "unadvertised" };
+  if (lastAdvertisedAtMs === null) return { kind: "pending" };
+  // Offline costs reachability only, and it costs it immediately — waiting
+  // out the lease on a dropped session would advertise a provider that
+  // cannot actually take the job.
+  if (!sessionConnected) return { kind: "stale" };
+
+  const expiresAtMs = lastAdvertisedAtMs + sessionLeaseTtlMs;
+  if (nowMs >= expiresAtMs) return { kind: "stale" };
+
+  return {
+    kind: "available",
+    refreshDueAtMs:
+      lastAdvertisedAtMs + refreshIntervalForLease(sessionLeaseTtlMs),
+    expiresAtMs,
+  };
+}
+
+/**
+ * Whether this agent may currently produce a paid quote (buzz#84 gotcha:
+ * quoting costs money, so nothing should auto-quote outside a state that is
+ * both advertised and honestly reachable right now).
+ */
+export function canQuoteJobs(availability: ProviderAvailability): boolean {
+  return availability.kind === "available";
+}
+
+/** The caption a provider settings surface shows for each state. */
+export function providerAvailabilityCaption(
+  availability: ProviderAvailability,
+): string | null {
+  switch (availability.kind) {
+    case "unadvertised":
+      return null;
+    case "pending":
+      return "Publishing this agent's provider listing…";
+    case "available":
+      return "Advertised as available to buyers on the open job market.";
+    case "stale":
+      return "Not currently reachable — this agent's provider listing will not accept new jobs until its connector session reconnects.";
+  }
+}