diff --git a/apps/web/src/components/ComposerUsageIndicator.test.tsx b/apps/web/src/components/ComposerUsageIndicator.test.tsx
new file mode 100644
index 000000000..a0e0fe334
--- /dev/null
+++ b/apps/web/src/components/ComposerUsageIndicator.test.tsx
@@ -0,0 +1,155 @@
+import {
+  EnvironmentId,
+  ProviderDriverKind,
+  ProviderInstanceId,
+  type ServerProvider,
+} from "@t3tools/contracts";
+import { renderToStaticMarkup } from "react-dom/server";
+import { describe, expect, it } from "vite-plus/test";
+
+import { deriveComposerUsage, hasComposerUsageContent } from "../providerUsageAccounts";
+import { shouldShowComposerContextStrip } from "./BranchToolbar.logic";
+import { ComposerUsageIndicator } from "./ComposerUsageIndicator";
+
+const prime: ServerProvider = {
+  instanceId: ProviderInstanceId.make("primeAgent"),
+  driver: ProviderDriverKind.make("primeAgent"),
+  enabled: true,
+  installed: true,
+  version: null,
+  status: "ready",
+  auth: { status: "authenticated" },
+  checkedAt: "2026-09-10T12:00:00.000Z",
+  models: [
+    { slug: "default", name: "Prime Agent Default", isCustom: false, capabilities: null },
+    {
+      slug: "prime-inference/claude-haiku-4-5",
+      name: "Claude Haiku 4.5",
+      subProvider: "prime-inference",
+      isCustom: false,
+      capabilities: null,
+    },
+    {
+      slug: "openai/gpt-5.6",
+      name: "GPT-5.6",
+      subProvider: "openai",
+      isCustom: false,
+      capabilities: null,
+    },
+    {
+      slug: "openai-codex/gpt-5.6",
+      name: "GPT-5.6",
+      subProvider: "openai-codex",
+      isCustom: false,
+      capabilities: null,
+    },
+  ],
+  slashCommands: [],
+  skills: [],
+};
+const codex: ServerProvider = {
+  ...prime,
+  instanceId: ProviderInstanceId.make("codex"),
+  driver: ProviderDriverKind.make("codex"),
+  displayName: "Codex Work",
+  models: [],
+  auth: { status: "authenticated", accountId: "codex-account" },
+  usageLimits: {
+    source: "codex",
+    checkedAt: "2026-09-10T12:00:00.000Z",
+    windows: [{ label: "Session", usedPercent: 37, windowDurationMins: 300 }],
+  },
+};
+
+function renderUsage(
+  selectedModel: string | null,
+  options: { enabled?: boolean; backends?: ServerProvider["backends"] } = {},
+) {
+  const usage = deriveComposerUsage({
+    providerStatuses: [
+      codex,
+      { ...prime, ...(options.backends ? { backends: options.backends } : {}) },
+    ],
+    selectedInstanceId: prime.instanceId,
+    selectedModel,
+    enabled: options.enabled ?? true,
+  });
+  // Exercise the gate ChatView uses when there are no other reasons to show the strip.
+  const showStrip = shouldShowComposerContextStrip({
+    hasActiveProject: true,
+    isGitRepo: false,
+    showEnvironmentIndicator: false,
+    hostsRestingComposerControls: false,
+    hasCapacityReading: hasComposerUsageContent(usage),
+  });
+  const html = renderToStaticMarkup(
+    <ComposerUsageIndicator
+      environmentId={EnvironmentId.make("test-environment")}
+      usage={usage}
+      timestampFormat="24-hour"
+      staleAfterMs={300_000}
+    />,
+  );
+  return { html, showStrip, usage };
+}
+
+describe("ComposerUsageIndicator", () => {
+  it.each(["prime-inference/claude-haiku-4-5", "openai/gpt-5.6"])(
+    "keeps the strip visible and explains unreported capacity for %s",
+    (selectedModel) => {
+      const { html, showStrip } = renderUsage(selectedModel);
+
+      expect(showStrip).toBe(true);
+      expect(html).toContain(">Capacity not reported for this backend</span>");
+      expect(html).not.toContain("Codex Work");
+      expect(html).not.toContain("37%");
+      expect(html).not.toContain("<button");
+    },
+  );
+
+  it.each(["default", "prime-inference/unknown", null])(
+    "renders nothing and leaves the empty strip hidden for %s",
+    (selectedModel) => {
+      const { html, showStrip } = renderUsage(selectedModel);
+      expect(html).toBe("");
+      expect(showStrip).toBe(false);
+    },
+  );
+
+  it("hides unreported capacity when provider usage is disabled", () => {
+    const { html, showStrip } = renderUsage("prime-inference/claude-haiku-4-5", { enabled: false });
+    expect(html).toBe("");
+    expect(showStrip).toBe(false);
+  });
+
+  it.each([
+    { verification: "assumed", backends: [] },
+    {
+      verification: "matched",
+      backends: [{ backend: "openai-codex", accountId: "codex-account" }],
+    },
+    {
+      verification: "own",
+      backends: [{ backend: "openai-codex", usageLimits: codex.usageLimits }],
+    },
+  ])("preserves $verification capacity for a mapped backend", ({ verification, backends }) => {
+    const { html, showStrip, usage } = renderUsage("openai-codex/gpt-5.6", { backends });
+    expect(showStrip).toBe(true);
+    expect(usage.backend?.verification).toBe(verification);
+    expect(html).toContain(">37%</span>");
+    expect(html).toContain('aria-label="Subscription capacity for ');
+    expect(html).not.toContain("Capacity not reported for this backend");
+  });
+
+  it("preserves the distinct account mismatch message without borrowing capacity", () => {
+    const { html, showStrip, usage } = renderUsage("openai-codex/gpt-5.6", {
+      backends: [{ backend: "openai-codex", accountId: "different-account" }],
+    });
+    expect(showStrip).toBe(true);
+    expect(usage.backend?.verification).toBe("mismatch");
+    expect(html).toContain(">Capacity unavailable</span>");
+    expect(html).toContain('aria-label="Subscription capacity unavailable"');
+    expect(html).not.toContain("37%");
+    expect(html).not.toContain("Capacity not reported for this backend");
+  });
+});
diff --git a/apps/web/src/components/ComposerUsageIndicator.tsx b/apps/web/src/components/ComposerUsageIndicator.tsx
index 42bc36f63..2e5f56e8b 100644
--- a/apps/web/src/components/ComposerUsageIndicator.tsx
+++ b/apps/web/src/components/ComposerUsageIndicator.tsx
@@ -20,6 +20,8 @@ import { getComposerUsageView } from "./ComposerUsageIndicator.logic";
 function describeBackend(backend: ComposerUsageBackend, accountCount: number): string {
   const runs = `Prime Agent runs ${backend.model} on ${backend.label}.`;
   switch (backend.verification) {
+    case "unreported":
+      return "Capacity not reported for this backend";
     case "own":
       return `${runs} This is Prime Agent's own ${backend.label} capacity, read from its sign-in.`;
     case "matched":
@@ -96,6 +98,14 @@ export const ComposerUsageIndicator = memo(function ComposerUsageIndicator({
     })();
   }, [accounts, environmentId, isRefreshing, refreshProviders]);
 
+  if (usage.backend?.verification === "unreported") {
+    return (
+      <span className={cn("px-1 py-0.5 text-xs text-muted-foreground/50", className)}>
+        {describeBackend(usage.backend, accounts.length)}
+      </span>
+    );
+  }
+
   // Prime is signed in to an account that is not configured here: there is
   // no number to show, but silence would read as the gauge being broken.
   if (!view && usage.backend?.verification !== "mismatch") return null;
diff --git a/apps/web/src/components/chat/ModelListRow.test.tsx b/apps/web/src/components/chat/ModelListRow.test.tsx
new file mode 100644
index 000000000..a2ad5a8c5
--- /dev/null
+++ b/apps/web/src/components/chat/ModelListRow.test.tsx
@@ -0,0 +1,46 @@
+import { ProviderDriverKind, ProviderInstanceId } from "@t3tools/contracts";
+import { renderToStaticMarkup } from "react-dom/server";
+import { describe, expect, it } from "vite-plus/test";
+
+import { Combobox } from "../ui/combobox";
+import { ModelListRow } from "./ModelListRow";
+
+function renderRow(disabledReason?: string) {
+  return renderToStaticMarkup(
+    <Combobox open>
+      <ModelListRow
+        index={0}
+        model={{ slug: "default", name: "Prime Agent Default" }}
+        instanceId={ProviderInstanceId.make("primeAgent")}
+        driverKind={ProviderDriverKind.make("primeAgent")}
+        providerDisplayName="Prime Agent"
+        isFavorite={false}
+        isSelected={false}
+        showProvider
+        disabledReason={disabledReason ?? null}
+        onToggleFavorite={() => undefined}
+      />
+    </Combobox>,
+  );
+}
+
+describe("ModelListRow", () => {
+  it("puts the disabled reason on the actual option and preserves its disabled semantics", () => {
+    const reason = "Start a new thread to use Prime Agent Default.";
+    const html = renderRow(reason);
+    const option = html.match(/<[^>]+role="option"[^>]*>/)?.[0];
+
+    expect(option).toBeDefined();
+    expect(option).toContain('aria-disabled="true"');
+    expect(option).toContain(`title="${reason}"`);
+  });
+
+  it("leaves an available option enabled without a disabled title", () => {
+    const html = renderRow();
+    const option = html.match(/<[^>]+role="option"[^>]*>/)?.[0];
+
+    expect(option).toBeDefined();
+    expect(option).not.toContain('aria-disabled="true"');
+    expect(option).not.toContain("title=");
+  });
+});
diff --git a/apps/web/src/components/chat/ModelListRow.tsx b/apps/web/src/components/chat/ModelListRow.tsx
index caa595dff..5e1b43cf2 100644
--- a/apps/web/src/components/chat/ModelListRow.tsx
+++ b/apps/web/src/components/chat/ModelListRow.tsx
@@ -50,6 +50,7 @@ export const ModelListRow = memo(function ModelListRow(props: {
       hideIndicator
       index={props.index}
       value={modelPickerModelKey(props.instanceId, props.model.slug)}
+      title={props.disabledReason ?? undefined}
       disabled={Boolean(props.disabledReason)}
       contentClassName="flex w-full items-center gap-3"
       className={cn(
diff --git a/apps/web/src/providerUsageAccounts.test.ts b/apps/web/src/providerUsageAccounts.test.ts
index 1c1c82751..21d321902 100644
--- a/apps/web/src/providerUsageAccounts.test.ts
+++ b/apps/web/src/providerUsageAccounts.test.ts
@@ -83,6 +83,13 @@ const PRIME_MODELS: ServerProvider["models"] = [
     isCustom: false,
     capabilities: null,
   },
+  {
+    slug: "openai/gpt-5.6",
+    name: "GPT-5.6",
+    subProvider: "openai",
+    isCustom: false,
+    capabilities: null,
+  },
   {
     slug: "prime-inference/qwen",
     name: "Qwen",
@@ -232,9 +239,37 @@ describe("deriveComposerUsage", () => {
       expect(usage.backend?.verification).toBe("assumed");
     });
 
+    it.each(["prime-inference/qwen", "openai/gpt-5.6"])(
+      "explains unreported capacity for the known backend of %s",
+      (selectedModel) => {
+        const usage = deriveComposerUsage({
+          providerStatuses: ALL,
+          selectedInstanceId: "primeAgent",
+          selectedModel,
+          enabled: true,
+        });
+
+        expect(usage.accounts).toEqual([]);
+        expect(usage.primary).toBeNull();
+        expect(usage.backend?.driver).toBeNull();
+        expect(usage.backend?.verification).toBe("unreported");
+        expect(hasComposerUsageContent(usage)).toBe(true);
+      },
+    );
+
+    it("respects disabled usage for a known unmapped backend", () => {
+      expect(
+        deriveComposerUsage({
+          providerStatuses: ALL,
+          selectedInstanceId: "primeAgent",
+          selectedModel: "prime-inference/qwen",
+          enabled: false,
+        }),
+      ).toBe(EMPTY_COMPOSER_USAGE);
+    });
+
     it.each([
       ["Prime's own default", "default"],
-      ["a backend Pylon has no driver for", "prime-inference/qwen"],
       ["an unknown slug", "anthropic/not-listed"],
       ["no model", null],
     ])("shows nothing for %s", (_label, selectedModel) => {
diff --git a/apps/web/src/providerUsageAccounts.ts b/apps/web/src/providerUsageAccounts.ts
index 5fb76a897..86955cb1b 100644
--- a/apps/web/src/providerUsageAccounts.ts
+++ b/apps/web/src/providerUsageAccounts.ts
@@ -31,7 +31,7 @@ const PRIME_AGENT_DRIVER = ProviderDriverKind.make("primeAgent");
  * Prime's backend names, as its model discovery reports them, mapped to the
  * Pylon driver whose accounts hold that backend's subscription. Backends
  * without a Pylon driver (Prime Inference, plain OpenAI keys) have no
- * capacity to show and are left out.
+ * capacity to show; the composer explains that reporting is unavailable.
  */
 const PRIME_AGENT_BACKEND_DRIVERS: Readonly<Record<string, ProviderDriverKind>> = {
   anthropic: ProviderDriverKind.make("claudeAgent"),
@@ -48,21 +48,22 @@ export type ComposerUsageVerification =
   /** Prime is signed in to a different account than any configured here. */
   | "mismatch";
 
-export interface ComposerUsageBackend {
-  readonly driver: ProviderDriverKind;
-  /** Brand label for the driver, e.g. "Claude". */
+export type ComposerUsageBackend = {
+  /** Brand label for the driver, or the unmapped backend name. */
   readonly label: string;
   /** Display name of the Prime model the capacity is being shown for. */
   readonly model: string;
-  readonly verification: ComposerUsageVerification;
-}
+} & (
+  | { readonly driver: ProviderDriverKind; readonly verification: ComposerUsageVerification }
+  | { readonly driver: null; readonly verification: "unreported" }
+);
 
 export interface ComposerUsage {
   /** Accounts the popover compares. Empty when nothing reports capacity. */
   readonly accounts: ReadonlyArray<ProviderUsageAccount>;
   /** The account the strip shows, or null when there is nothing to show. */
   readonly primary: ProviderUsageAccount | null;
-  /** Set when the composer targets Prime Agent and capacity comes from its backend. */
+  /** The selected Prime backend and whether its capacity can be attributed or reported. */
   readonly backend: ComposerUsageBackend | null;
 }
 
@@ -77,9 +78,11 @@ export const EMPTY_COMPOSER_USAGE: ComposerUsage = { accounts: [], primary: null
  * there is one, so any instant answers this question.
  */
 export function hasComposerUsageContent(usage: ComposerUsage): boolean {
-  // Prime signed in elsewhere still reports that, and saying so is content.
+  // Explanations of unavailable capacity keep the strip visible too.
   return (
-    usage.backend?.verification === "mismatch" || getComposerUsageView(usage.primary, 0) !== null
+    usage.backend?.verification === "mismatch" ||
+    usage.backend?.verification === "unreported" ||
+    getComposerUsageView(usage.primary, 0) !== null
   );
 }
 
@@ -106,15 +109,21 @@ function accountsForDriver(
   });
 }
 
-/** The Prime model the composer has selected, when its backend has a Pylon driver. */
+/** The selected Prime model with a known backend, including unmapped backends. */
 function primeAgentBackend(
   prime: ServerProvider,
   selectedModel: string | null | undefined,
-): { readonly driver: ProviderDriverKind; readonly model: ServerProviderModel } | null {
+): {
+  readonly driver: ProviderDriverKind | null;
+  readonly model: ServerProviderModel & { readonly subProvider: string };
+} | null {
   if (!selectedModel) return null;
   const model = prime.models.find((candidate) => candidate.slug === selectedModel);
-  const driver = model?.subProvider ? PRIME_AGENT_BACKEND_DRIVERS[model.subProvider] : undefined;
-  return model && driver ? { driver, model } : null;
+  if (!model?.subProvider) return null;
+  return {
+    driver: PRIME_AGENT_BACKEND_DRIVERS[model.subProvider] ?? null,
+    model: { ...model, subProvider: model.subProvider },
+  };
 }
 
 /**
@@ -194,7 +203,22 @@ export function deriveComposerUsage(input: {
   if (selected.driver === PRIME_AGENT_DRIVER) {
     const backend = primeAgentBackend(selected, input.selectedModel);
     if (!backend) return EMPTY_COMPOSER_USAGE;
-    return primeAgentUsage(input.providerStatuses, selected, backend);
+    if (!backend.driver) {
+      return {
+        accounts: [],
+        primary: null,
+        backend: {
+          driver: null,
+          label: backend.model.subProvider,
+          model: backend.model.shortName ?? backend.model.name,
+          verification: "unreported",
+        },
+      };
+    }
+    return primeAgentUsage(input.providerStatuses, selected, {
+      driver: backend.driver,
+      model: backend.model,
+    });
   }
 
   const accounts = accountsForDriver(input.providerStatuses, selected.driver, selected.instanceId);