diff --git a/packages/paperclip-runner/docs/runner-protocol-live-evals.md b/packages/paperclip-runner/docs/runner-protocol-live-evals.md
index 1ef927f5825..3760e60f40c 100644
--- a/packages/paperclip-runner/docs/runner-protocol-live-evals.md
+++ b/packages/paperclip-runner/docs/runner-protocol-live-evals.md
@@ -659,6 +659,19 @@ billable usage. These receipt corrections also apply to non-eval ACPX sessions.
 The durable redactor preserves these known numeric token-counter fields;
 string/object values under the same names remain redacted as sensitive data.
 
+Grok 1.0.13 reports whole-prompt usage in `session/prompt` response
+`_meta.usage`. The sibling `_meta` counters describe only the last model call.
+Runner binds the nested receipt to the outbound JSON-RPC request and session,
+then emits it before the terminal event. Replayed, conflicting, malformed, or
+incomplete receipts cannot supply complete accounting. ACP input includes cache
+reads and cache creation; Runner separates those buckets and does not add the
+reasoning subset to output again. A complete `costUsdTicks` uses 10 billion ticks
+per USD. Missing or partial cost remains unknown. The sidecar's `cost.basis`
+distinguishes a `turn` total from the default session-cumulative cost, so later
+turns do not inherit or subtract an earlier turn's bill.
+These semantics follow the upstream [prompt usage contract](https://github.com/xai-org/grok-build/blob/2bdd1d6a6369de0e8c68132ea4539e9abd9e14a8/crates/codegen/xai-grok-shell/src/extensions/notification.rs)
+and [prompt response tests](https://github.com/xai-org/grok-build/blob/2bdd1d6a6369de0e8c68132ea4539e9abd9e14a8/crates/codegen/xai-grok-shell/src/agent/mvp_agent/prompt_response_meta_tests.rs).
+
 `all` means the maintained enabled campaign, not every matching file in the
 roster directory. A missing campaign file fails closed. Within an enabled
 lane, a missing remote profile or unavailable provider is retained as an
diff --git a/packages/paperclip-runner/protocol/provider-schemas/acpx-sidecar.schema.json b/packages/paperclip-runner/protocol/provider-schemas/acpx-sidecar.schema.json
index bd1717d102f..7578065f002 100644
--- a/packages/paperclip-runner/protocol/provider-schemas/acpx-sidecar.schema.json
+++ b/packages/paperclip-runner/protocol/provider-schemas/acpx-sidecar.schema.json
@@ -225,6 +225,14 @@
       },
       "additionalProperties": false,
       "allOf": [
+        {
+          "if": { "properties": { "eventType": { "const": "runtime.event" }, "payload": {
+            "type": "object",
+            "properties": { "type": { "const": "status" }, "tag": { "const": "usage_update" } },
+            "required": ["type", "tag"]
+          } } },
+          "then": { "properties": { "payload": { "type": "object", "properties": { "cost": { "$ref": "#/$defs/usageCost" } } } } }
+        },
         {
           "if": { "properties": { "eventType": { "const": "runtime.rich_event" } } },
           "then": {
@@ -237,6 +245,16 @@
         }
       ]
     },
+    "usageCost": {
+      "description": "Provider cost is session-cumulative unless basis explicitly identifies a complete turn total. A turn total is never a session counter.",
+      "type": ["object", "null"],
+      "properties": {
+        "amount": { "type": ["number", "null"], "minimum": 0 },
+        "currency": { "type": ["string", "null"], "maxLength": 16 },
+        "basis": { "enum": ["turn", "session_cumulative"] }
+      },
+      "additionalProperties": false
+    },
     "richEvent": {
       "type": "object",
       "required": [
diff --git a/packages/paperclip-runner/runner/crates/runner-core/src/provider_events.rs b/packages/paperclip-runner/runner/crates/runner-core/src/provider_events.rs
index b1d76fef47a..dd674180e5d 100644
--- a/packages/paperclip-runner/runner/crates/runner-core/src/provider_events.rs
+++ b/packages/paperclip-runner/runner/crates/runner-core/src/provider_events.rs
@@ -1208,9 +1208,11 @@ fn normalize_acpx_status(
             Some(Value::String(currency)) => currency.eq_ignore_ascii_case("USD"),
             Some(_) => false,
         };
-        // ACPX 0.13.1 documents breakdown as per-turn usage while cost is
-        // session-cumulative. Keep those authorities separate so consumers do
-        // not add the same tokens twice or treat cumulative cost as a delta.
+        let turn_cost = payload.pointer("/cost/basis").and_then(Value::as_str) == Some("turn");
+        let provider_cost = if cost_is_usd {
+            payload.pointer("/cost/amount").and_then(Value::as_f64)
+                .filter(|value| value.is_finite() && *value >= 0.0).unwrap_or(0.0)
+        } else { 0.0 };
         let cumulative = json!({
             "inputTokens": 0,
             "outputTokens": 0,
@@ -1218,15 +1220,7 @@ fn normalize_acpx_status(
             "cacheWriteTokens": 0,
             "activeSeconds": 0.0,
             "requests": provider_requests,
-            "providerCostUsd": if cost_is_usd {
-                payload
-                    .pointer("/cost/amount")
-                    .and_then(Value::as_f64)
-                    .filter(|value| value.is_finite() && *value >= 0.0)
-                    .unwrap_or(0.0)
-            } else {
-                0.0
-            },
+            "providerCostUsd": if turn_cost { 0.0 } else { provider_cost },
         });
         let run_delta = json!({
             "inputTokens": nonnegative_u64(breakdown.get("inputTokens")),
@@ -1243,7 +1237,7 @@ fn normalize_acpx_status(
             ),
             "activeSeconds": 0.0,
             "requests": 1,
-            "providerCostUsd": 0.0,
+            "providerCostUsd": if turn_cost { provider_cost } else { 0.0 },
         });
         return vec![NormalizedProviderEvent {
             event_type: "usage.reported".to_owned(),
@@ -1499,6 +1493,28 @@ fn has_rfc_uri_scheme_prefix(value: &str) -> bool {
 mod tests {
     use super::*;
 
+    #[test]
+    fn acpx_turn_cost_is_not_a_cumulative_session_price() {
+        let base = json!({"tag": "usage_update", "breakdown": {
+            "inputTokens": 30787, "outputTokens": 5763, "cachedReadTokens": 475008,
+            "cachedWriteTokens": 0, "thoughtTokens": 0
+        }, "cost": {"amount": 0.336842, "currency": "USD", "basis": "turn"}});
+        let first = normalize_acpx_status(&base, "item", "turn-1", 1);
+        assert_eq!(first[0].payload["runDeltaAvailable"], true);
+        assert_eq!(first[0].payload["runDelta"]["providerCostUsd"], 0.336842);
+        assert_eq!(first[0].payload["cumulative"]["providerCostUsd"], 0.0);
+        assert_eq!(first[0].payload["runDelta"]["inputTokens"], 30787);
+        assert_eq!(first[0].payload["runDelta"]["outputTokens"], 5763);
+        let mut second = base.clone();
+        second["cost"]["amount"] = json!(0.001);
+        let next = normalize_acpx_status(&second, "next", "turn-2", 2);
+        assert_eq!(next[0].payload["runDelta"]["providerCostUsd"], 0.001);
+        second["cost"].as_object_mut().unwrap().remove("basis");
+        let cumulative = normalize_acpx_status(&second, "legacy", "turn-3", 3);
+        assert_eq!(cumulative[0].payload["cumulative"]["providerCostUsd"], 0.001);
+        assert_eq!(cumulative[0].payload["runDelta"]["providerCostUsd"], 0.0);
+    }
+
     #[test]
     fn performance_diagnostics_keep_only_bounded_content_free_measurements() {
         let mut spans = vec![json!({"name":"private prompt","startedAtMs":1,"endedAtMs":2})];
diff --git a/packages/paperclip-runner/src/cli/acpx-runtime-sidecar.test.ts b/packages/paperclip-runner/src/cli/acpx-runtime-sidecar.test.ts
index 5a96c9aebea..9741e14641b 100644
--- a/packages/paperclip-runner/src/cli/acpx-runtime-sidecar.test.ts
+++ b/packages/paperclip-runner/src/cli/acpx-runtime-sidecar.test.ts
@@ -8,7 +8,7 @@ import { appendSemanticToolReceipt, readNativeSemanticReceipt, semanticInputSha2
 import { startRunnerToolBridge, type RunnerToolCall } from "../drivers/runner-tool-bridge.js";
 import { validatePrpStructuredRunResult } from "../protocol/replay-contract.js";
 import { resolveCompletionContinuation } from "../drivers/completion-continuation.js";
-import { acpxUsageEstimateNotice, persistedAcpxTurnUsage, persistedCursorUsageNotice } from "../drivers/acpx/usage-accounting.js";
+import { acpxUsageEstimateNotice, persistedAcpxTurnUsage, persistedCursorUsageNotice, qualifiedAcpxUsageBreakdown } from "../drivers/acpx/usage-accounting.js";
 import { stripTypeScriptTypes } from "node:module";
 import { cursorPlanToolIdentity, cursorToolIdentity } from "../drivers/acpx/cursor-plan-tool-identity.js";
 import { createHash, randomUUID } from "node:crypto";
@@ -21,6 +21,22 @@ import { createKimiMessageProjection } from "../drivers/acpx/kimi-message-bounda
 import { afterEach, describe, expect, it, vi } from "vitest";
 
 describe("live sidecar pending request snapshots", () => {
+  it("preserves explicit turn cost through the sidecar's closed usage projection", () => {
+    const source = readFileSync(new URL("./acpx-runtime-sidecar.ts", import.meta.url), "utf8");
+    const start = source.indexOf("function safeUsage(");
+    const end = source.indexOf("function safeOutput(", start);
+    const project = new Function("record", "qualifiedAcpxUsageBreakdown", "initializedAgent", "safeText", "text",
+      `${stripTypeScriptTypes(source.slice(start, end))}; return safeUsage;`)(
+      (value: unknown) => value && typeof value === "object" ? value : {}, qualifiedAcpxUsageBreakdown, "grok",
+      (value: string) => value, (value: unknown) => typeof value === "string" ? value : "",
+    );
+    expect(project({ amount: 0.336842, currency: "USD", basis: "turn", rawSecret: "excluded" }, null)).toEqual({
+      cost: { amount: 0.336842, currency: "USD", basis: "turn" }, breakdown: null,
+    });
+    expect(project({ amount: 0.7, currency: "USD" }, null)).toEqual({ cost: { amount: 0.7, currency: "USD" }, breakdown: null });
+    expect(project(undefined, null)).toEqual({ cost: null, breakdown: null });
+  });
+
   it("attests current callback identities after the live status barrier without exposing forms", async () => {
     const source = readFileSync(new URL("./acpx-runtime-sidecar.ts", import.meta.url), "utf8");
     const start = source.indexOf('  if (request.command === "session.snapshot") {');
diff --git a/packages/paperclip-runner/src/cli/acpx-runtime-sidecar.ts b/packages/paperclip-runner/src/cli/acpx-runtime-sidecar.ts
index 155f963fd99..8510323ef77 100644
--- a/packages/paperclip-runner/src/cli/acpx-runtime-sidecar.ts
+++ b/packages/paperclip-runner/src/cli/acpx-runtime-sidecar.ts
@@ -1199,6 +1199,7 @@ function safeUsage(cost: unknown, breakdown: unknown): Record<string, unknown> {
         ? null
         : {
             amount: safeNonNegativeNumber(nativeCost.amount),
+            ...(nativeCost.basis === "turn" ? { basis: "turn" } : {}),
             currency: safeText(text(nativeCost.currency)).slice(0, 16) || null,
           },
     breakdown:
diff --git a/packages/paperclip-runner/src/drivers/acpx/codex-runtime-adapter.test.ts b/packages/paperclip-runner/src/drivers/acpx/codex-runtime-adapter.test.ts
index 0df913dbe3d..b0ea480a234 100644
--- a/packages/paperclip-runner/src/drivers/acpx/codex-runtime-adapter.test.ts
+++ b/packages/paperclip-runner/src/drivers/acpx/codex-runtime-adapter.test.ts
@@ -19,6 +19,7 @@ import { describe, expect, it, vi } from "vitest";
 import type { VerifiedAcpxCommandLease } from "./installation-integrity.js";
 import { openCodexAcpxRuntime } from "./codex-runtime-adapter.js";
 import { cursorInstructionBinding } from "./cursor-instructions.js";
+import { persistedAcpxTurnUsage } from "./usage-accounting.js";
 import { createAcpxCommandLeaseOwner } from "./command-lease-owner.js";
 import { resolveQualifiedAcpxProfile } from "./qualified-profiles.js";
 import type { AcpxRuntimePortOpenOptions } from "./runtime-host.js";
@@ -913,6 +914,44 @@ describe("Codex ACPX runtime adapter", () => {
     expect(assertWorkspaceHeld).toHaveBeenCalledOnce();
     expect(command.spawn).not.toHaveBeenCalled();
   });
+  it("exposes only the active Grok prompt response as terminal usage across consecutive turns", async () => {
+    const runtime = fakeRuntime();
+    const durableRecord = { acpxRecordId: "record-1", acpSessionId: "backend-1", agentSessionId: "agent-1", lastRequestId: "previous" };
+    const durableStore: AcpSessionStore = { load: vi.fn(async () => structuredClone(durableRecord) as never), save: vi.fn() };
+    let created!: AcpRuntimeOptions;
+    const options = openOptions(fakeCommand());
+    options.profile = { ...options.profile, agent: "grok" };
+    const port = await openCodexAcpxRuntime(options, { createRegistry: () => registry(), createStore: () => durableStore,
+      createRuntime: value => { created = value; return runtime; } });
+    let sequence = 0;
+    vi.mocked(runtime.startTurn).mockImplementation(input => {
+      const wireId = ++sequence;
+      durableRecord.lastRequestId = input.requestId;
+      created.onAcpMessage?.("outbound", { id: wireId, method: "session/prompt", params: { sessionId: "backend-1" } });
+      created.onAcpMessage?.("inbound", { id: wireId, result: { _meta: {
+        sessionId: "backend-1", promptId: `prompt-${wireId}`, requestId: `prompt-${wireId}`,
+        usage: { inputTokens: 50, outputTokens: 5, totalTokens: 55, cachedReadTokens: 20, cacheCreationTokens: 0,
+          reasoningTokens: 2, modelCalls: 1, costUsdTicks: wireId === 1 ? 10000000 : 5000000 },
+      } } });
+      return { requestId: input.requestId, promptStarted: Promise.resolve(), events: (async function* () {})(),
+        result: Promise.resolve({ status: "completed" as const }), cancel: async () => undefined, closeStream: async () => undefined };
+    });
+    try {
+      for (const [requestId, amount] of [["runner-1", 0.001], ["runner-2", 0.0005]] as const) {
+        const before = await port.getStatus();
+        const turn = port.startTurn({ requestId, text: "fixture" });
+        await turn.result;
+        const after = await port.getStatus();
+        expect(persistedAcpxTurnUsage(before, after, requestId)).toMatchObject({
+          cost: { amount, currency: "USD", basis: "turn" },
+          breakdown: { inputTokens: 30, outputTokens: 5, cachedReadTokens: 20, thoughtTokens: 0 },
+        });
+        created.onAcpMessage?.("inbound", { id: sequence, error: { message: "late conflicting response" } });
+        expect(await port.getStatus()).toEqual(after);
+      }
+    } finally { await port.close({ reason: "fixture done" }); }
+  });
+
   it("reads verified status from durable state without draining live updates", async () => {
     const runtime = fakeRuntime();
     vi.mocked(runtime.getStatus!).mockReturnValue(new Promise(() => {}));
diff --git a/packages/paperclip-runner/src/drivers/acpx/codex-runtime-adapter.ts b/packages/paperclip-runner/src/drivers/acpx/codex-runtime-adapter.ts
index 580bf58453d..ba1e97ce2ac 100644
--- a/packages/paperclip-runner/src/drivers/acpx/codex-runtime-adapter.ts
+++ b/packages/paperclip-runner/src/drivers/acpx/codex-runtime-adapter.ts
@@ -1,6 +1,7 @@
 import { admitAcpxSessionContext } from "./session-context-admission.js";
 import { createKimiInstructionAdmission } from "./kimi-instructions.js";
 import { kimiReadOnlyPermissionAllowed } from "./kimi-config.js";
+import { createGrokPromptUsageCollector } from "./grok-usage.js";
 import { resolveGrokDisableWebSearch } from "./grok-web-search.js";
 import { resolveGrokEffort, createGrokEffortAdmission } from "./grok-effort.js";
 import { resolveClaudeEffort, createClaudeEffortAdmission } from "./claude-effort.js";
@@ -295,6 +296,7 @@ export async function openQualifiedAcpxRuntime(
   const extensionProfile = ACPX_CAPABILITY_PROFILES[options.profile.agent];
   const extensionRequests = new Set(extensionProfile.extensionRequests);
   const extensionNotifications = new Set(extensionProfile.extensionNotifications);
+  const promptUsage = options.profile.agent === "grok" ? createGrokPromptUsageCollector() : undefined;
   const extensionBoundary: AcpxRuntimeExtensionBoundary = {
     active: null, sessionIds: new Set(), steering: null,
   };
@@ -466,6 +468,10 @@ export async function openQualifiedAcpxRuntime(
         : null;
     },
     onSessionNotification: acceptGoalNotification,
+    onAcpMessage: (direction, message) => {
+      const active = extensionBoundary.active;
+      if (active && !active.signal.aborted) promptUsage?.observe(direction, message);
+    },
     spawnEnvironment: () => ({
       ...definedEnvironment(options.launchEnvironment),
       ...(options.profile.agent === "claude"
@@ -685,6 +691,7 @@ export async function openQualifiedAcpxRuntime(
       extensionBoundary,
       options.profile.agent === "copilot",
       options.profile.agent === "copilot" ? assertCopilotPromptPolicy : undefined,
+      promptUsage,
     );
   } catch (error) {
     const cleanupReason = "ACPX runtime identity validation failed";
@@ -1117,6 +1124,7 @@ function runtimePort(
   extensionBoundary: AcpxRuntimeExtensionBoundary,
   monitorProviderDeath: boolean,
   assertPromptPolicy?: (text: string) => void,
+  promptUsage?: ReturnType<typeof createGrokPromptUsageCollector>,
 ): AcpxRuntimePort {
   extensionBoundary.sessionIds = new Set([identity.backendSessionId]);
   let extensionControls: Promise<void> = Promise.resolve();
@@ -1375,7 +1383,8 @@ function runtimePort(
       return structuredClone(identity);
     },
     async getStatus() {
-      return await persistedRuntimeStatus(sessionStore, handle, identity);
+      const status = await persistedRuntimeStatus(sessionStore, handle, identity);
+      return promptUsage ? { ...status, terminalPromptUsage: promptUsage.snapshot() } : status;
     },
     steeringCapability() {
       return extensionBoundary.steering === null ? null : structuredClone(extensionBoundary.steering);
@@ -1488,6 +1497,7 @@ function runtimePort(
         onRequest: input.onExtensionRequest, onNotification: input.onExtensionNotification,
       };
       extensionBoundary.active = extensionTurn;
+      promptUsage?.begin(input.requestId, identity.backendSessionId);
       // A guardian can outlive the provider while ACP awaits a callback.
       // Native exit or a typed ACP agent disconnect retires this turn; losing
       // the controller connection must preserve deliverable input instead.
diff --git a/packages/paperclip-runner/src/drivers/acpx/grok-usage.test.ts b/packages/paperclip-runner/src/drivers/acpx/grok-usage.test.ts
new file mode 100644
index 00000000000..d056c688153
--- /dev/null
+++ b/packages/paperclip-runner/src/drivers/acpx/grok-usage.test.ts
@@ -0,0 +1,77 @@
+import { describe, expect, it } from "vitest";
+import { createGrokPromptUsageCollector, grokPromptUsage } from "./grok-usage.js";
+import { persistedAcpxTurnUsage } from "./usage-accounting.js";
+
+const usage = { inputTokens: 505795, outputTokens: 5763, totalTokens: 511558, cachedReadTokens: 475008,
+  cacheCreationTokens: 0, reasoningTokens: 531, modelCalls: 20, costUsdTicks: 3368420000 };
+const meta = { sessionId: "session-1", promptId: "prompt-1", requestId: "prompt-1", usage,
+  inputTokens: 999, outputTokens: 999, totalTokens: 999 };
+const request = { jsonrpc: "2.0", id: 7, method: "session/prompt", params: { sessionId: "session-1" } };
+const response = { jsonrpc: "2.0", id: 7, result: { stopReason: "end_turn", _meta: meta } };
+
+describe("Grok terminal prompt usage", () => {
+  it("uses the complete prompt ledger with disjoint cache buckets and exact USD tick conversion", () => {
+    expect(grokPromptUsage({ ...meta, usage: { ...usage, cacheCreationTokens: 100 } }, "session-1")).toEqual({
+      promptId: "prompt-1", event: { type: "status", tag: "usage_update", text: "terminal prompt usage",
+        cost: { amount: 0.336842, currency: "USD", basis: "turn" },
+        breakdown: { inputTokens: 30687, outputTokens: 5763, totalTokens: 511558, cachedReadTokens: 475008,
+          cachedWriteTokens: 100, thoughtTokens: 0 } },
+    });
+  });
+
+  it.each([
+    { usageIsIncomplete: true }, { usageIsIncomplete: "false" }, { cachedReadTokens: 505796 },
+    { inputTokens: -1 }, { outputTokens: 1.5 }, { reasoningTokens: 5764 }, { totalTokens: 1 },
+    { modelCalls: undefined }, { inputTokens: Number.MAX_SAFE_INTEGER + 1 },
+  ])("refuses incomplete or invalid token authority: %j", patch => {
+    expect(grokPromptUsage({ ...meta, usage: { ...usage, ...patch } }, "session-1")).toBeNull();
+  });
+
+  it.each([{ costUsdTicks: undefined }, { costUsdTicks: -1 }, { costIsPartial: true }, { costIsPartial: "false" }])(
+    "preserves complete tokens without inventing cost: %j", patch => {
+      const result = grokPromptUsage({ ...meta, usage: { ...usage, ...patch } }, "session-1");
+      expect(result?.event.breakdown).toMatchObject({ inputTokens: 30787, outputTokens: 5763 });
+      expect(result?.event).not.toHaveProperty("cost");
+    });
+
+  it("binds only the matching prompt response, rejects replay and leaves the next turn's price independent", () => {
+    const collector = createGrokPromptUsageCollector();
+    collector.begin("runner-1", "session-1");
+    collector.observe("inbound", response);
+    expect(collector.snapshot()).toBeNull();
+    collector.observe("outbound", request);
+    collector.observe("inbound", { ...response, id: 6 });
+    collector.observe("inbound", { ...response, method: "_x.ai/session/update" });
+    expect(collector.snapshot()).toBeNull();
+    collector.observe("inbound", response);
+    const first = collector.snapshot();
+    collector.observe("inbound", response);
+    expect(collector.snapshot()).toEqual(first);
+    const before = { lastRequestId: "runner-1", terminalPromptUsage: first };
+    expect(persistedAcpxTurnUsage({}, before, "runner-1")?.cost).toEqual({ amount: 0.336842, currency: "USD", basis: "turn" });
+    expect(persistedAcpxTurnUsage(before, before, "runner-1")).toBeNull();
+    expect(persistedAcpxTurnUsage({}, before, "foreign")).toBeNull();
+    collector.begin("runner-2", "session-1");
+    collector.observe("inbound", response);
+    expect(collector.snapshot()).toBeNull();
+    collector.observe("outbound", { ...request, id: 8 });
+    collector.observe("inbound", { ...response, id: 8, result: { _meta: { ...meta, promptId: "prompt-2", requestId: "prompt-2",
+      usage: { ...usage, costUsdTicks: 10000000 } } } });
+    const after = { lastRequestId: "runner-2", terminalPromptUsage: collector.snapshot() };
+    expect(persistedAcpxTurnUsage(before, after, "runner-2")?.cost).toEqual({ amount: 0.001, currency: "USD", basis: "turn" });
+  });
+
+  it.each(["foreign-session", "conflicting-receipt", "second-prompt", "rpc-error", "reused-prompt"])("rejects %s", kind => {
+    const collector = createGrokPromptUsageCollector();
+    collector.begin("runner-1", "session-1");
+    collector.observe("outbound", request);
+    collector.observe("inbound", response);
+    if (kind === "reused-prompt") { collector.begin("runner-2", "session-1"); collector.observe("outbound", request); }
+    if (kind === "second-prompt") collector.observe("outbound", request);
+    else collector.observe("inbound", kind === "rpc-error" ? { ...response, error: {} } : { ...response, result: { _meta: {
+      ...meta, ...(kind === "foreign-session" ? { sessionId: "session-2" } : {}),
+      ...(kind === "conflicting-receipt" ? { usage: { ...usage, costUsdTicks: 1 } } : {}),
+    } } });
+    expect(collector.snapshot()).toBeNull();
+  });
+});
diff --git a/packages/paperclip-runner/src/drivers/acpx/grok-usage.ts b/packages/paperclip-runner/src/drivers/acpx/grok-usage.ts
new file mode 100644
index 00000000000..7552f44f1eb
--- /dev/null
+++ b/packages/paperclip-runner/src/drivers/acpx/grok-usage.ts
@@ -0,0 +1,63 @@
+type RecordValue = Record<string, unknown>;
+const record = (value: unknown): RecordValue => value !== null && typeof value === "object" && !Array.isArray(value) ? value as RecordValue : {};
+const integer = (value: unknown): value is number => Number.isSafeInteger(value) && Number(value) >= 0;
+const id = (value: unknown): value is string => typeof value === "string" && /^[A-Za-z0-9][A-Za-z0-9._:-]{0,239}$/.test(value);
+
+export interface TerminalPromptUsage {
+  requestId: string;
+  promptId: string;
+  event: RecordValue;
+}
+
+export function grokPromptUsage(metaValue: unknown, sessionId: string): Omit<TerminalPromptUsage, "requestId"> | null {
+  const meta = record(metaValue), usage = record(meta.usage);
+  if (meta.sessionId !== sessionId || !id(meta.promptId) || meta.requestId !== meta.promptId
+    || (usage.usageIsIncomplete !== undefined && usage.usageIsIncomplete !== false)) return null;
+  const { inputTokens, outputTokens, totalTokens, cachedReadTokens, cacheCreationTokens, reasoningTokens, modelCalls } = usage;
+  if (![inputTokens, outputTokens, totalTokens, cachedReadTokens, cacheCreationTokens, reasoningTokens, modelCalls].every(integer)
+    || Number(inputTokens) + Number(outputTokens) !== totalTokens
+    || Number(cachedReadTokens) + Number(cacheCreationTokens) > Number(inputTokens)
+    || Number(reasoningTokens) > Number(outputTokens)) return null;
+  const costKnown = integer(usage.costUsdTicks) && (usage.costIsPartial === undefined || usage.costIsPartial === false);
+  return {
+    promptId: meta.promptId,
+    event: {
+      type: "status", tag: "usage_update", text: "terminal prompt usage",
+      ...(costKnown ? { cost: { amount: Number(usage.costUsdTicks) / 10_000_000_000, currency: "USD", basis: "turn" } } : {}),
+      breakdown: {
+        inputTokens: Number(inputTokens) - Number(cachedReadTokens) - Number(cacheCreationTokens),
+        outputTokens, totalTokens, cachedReadTokens, cachedWriteTokens: cacheCreationTokens, thoughtTokens: 0,
+      },
+    },
+  };
+}
+
+export function createGrokPromptUsageCollector() {
+  let active: { requestId: string; sessionId: string; wireId?: string | number; invalid: boolean; receipt: TerminalPromptUsage | null } | null = null;
+  let previousPromptId: string | undefined;
+  return {
+    begin(requestId: string, sessionId: string) {
+      previousPromptId = active?.receipt?.promptId ?? previousPromptId;
+      active = { requestId, sessionId, invalid: false, receipt: null };
+    },
+    observe(direction: "inbound" | "outbound", value: unknown) {
+      if (!active || active.invalid) return;
+      const message = record(value);
+      if (direction === "outbound") {
+        if (message.method !== "session/prompt" || record(message.params).sessionId !== active.sessionId) return;
+        if (active.wireId !== undefined || !(id(message.id) || integer(message.id))) { active.invalid = true; return; }
+        active.wireId = message.id;
+        return;
+      }
+      if (active.wireId === undefined || message.id !== active.wireId || message.method !== undefined) return;
+      const receipt = message.error === undefined ? grokPromptUsage(record(message.result)._meta, active.sessionId) : null;
+      if (!receipt || receipt.promptId === previousPromptId) { active.invalid = true; return; }
+      const bound = { ...receipt, requestId: active.requestId };
+      if (active.receipt && JSON.stringify(active.receipt) !== JSON.stringify(bound)) { active.invalid = true; return; }
+      active.receipt = bound;
+    },
+    snapshot(): TerminalPromptUsage | null {
+      return active && !active.invalid ? structuredClone(active.receipt) : null;
+    },
+  };
+}
diff --git a/packages/paperclip-runner/src/drivers/acpx/usage-accounting.ts b/packages/paperclip-runner/src/drivers/acpx/usage-accounting.ts
index 4143f655a68..6640ce97efa 100644
--- a/packages/paperclip-runner/src/drivers/acpx/usage-accounting.ts
+++ b/packages/paperclip-runner/src/drivers/acpx/usage-accounting.ts
@@ -43,6 +43,10 @@ export function persistedAcpxTurnUsage(
 ): Record<string, unknown> | null {
   const current = record(after);
   if (current.lastRequestId !== requestId) return null;
+  const terminal = record(current.terminalPromptUsage);
+  const priorTerminal = record(record(before).terminalPromptUsage);
+  if (terminal.requestId === requestId && terminal.promptId !== priorTerminal.promptId
+    && priorTerminal.requestId !== requestId) return record(terminal.event);
   const previousReceipts = record(record(before).requestTokenUsage);
   const receipts = record(current.requestTokenUsage);
   const added = Object.keys(receipts).filter(
diff --git a/packages/paperclip-runner/test/acpx-sidecar-contract.test.mjs b/packages/paperclip-runner/test/acpx-sidecar-contract.test.mjs
index 2b262d59641..7de94511896 100644
--- a/packages/paperclip-runner/test/acpx-sidecar-contract.test.mjs
+++ b/packages/paperclip-runner/test/acpx-sidecar-contract.test.mjs
@@ -53,6 +53,18 @@ test("the ACPX sidecar schema accepts each versioned message family", () => {
   }
 });
 
+test("usage prices declare turn or session scope without changing legacy cumulative prices", () => {
+  const event = cost => ({ protocolVersion, sequence: 1, eventType: "runtime.event", runId: "run-1", turnId: "turn-1",
+    payload: { type: "status", tag: "usage_update", cost } });
+  for (const cost of [null, { amount: 0.1, currency: "USD" }, { amount: 0.1, currency: "USD", basis: "turn" },
+    { amount: 0.1, currency: "USD", basis: "session_cumulative" }]) {
+    assert.equal(validate(event(cost)), true, JSON.stringify(validate.errors));
+  }
+  for (const cost of [{ amount: -1 }, { amount: 0.1, basis: "estimated" }, { amount: 0.1, rawProviderReceipt: {} }]) {
+    assert.equal(validate(event(cost)), false);
+  }
+});
+
 test("failed responses accept the bounded provider cause and reject extra diagnostic fields", () => {
   const failure = { schema: "paperclip.provider-failure.v1", provider: "anthropic", phase: "startup",
     category: "rate_limit", message: "Account rate limit reached.", httpStatus: 429, retryability: "unknown" };
diff --git a/server/src/services/native-runtime/native-session-executor.test.ts b/server/src/services/native-runtime/native-session-executor.test.ts
index e3611e34991..2de774f90ea 100644
--- a/server/src/services/native-runtime/native-session-executor.test.ts
+++ b/server/src/services/native-runtime/native-session-executor.test.ts
@@ -1632,6 +1632,18 @@ describe("native provider usage normalization", () => {
   it("does not treat a protocol-default price as free usage", () => {
     expect(nativeUsageCostUsd({ runDelta: { inputTokens: 20, outputTokens: 10, providerCostUsd: 0 } })).toBeUndefined();
   });
+  it("attributes Grok API usage while preserving managed billing identity", () => {
+    const provider = { kind: "acpx", agent: "grok", model: "grok-4.7" } as NativeExecutionInput["provider"];
+    expect(nativeUsageBiller(provider)).toBe("xai");
+    expect(resolveNativeBilling(provider)).toEqual({ provider: "xai", biller: "xai", billingType: "unknown" });
+    expect(resolveNativeBilling(provider, { XAI_API_KEY: "fixture" }))
+      .toEqual({ provider: "xai", biller: "xai", billingType: "metered_api" });
+    const subscription = { provider: "xai", biller: "xai", billingType: "subscription_included" as const };
+    expect(resolveNativeBilling(provider, { XAI_API_KEY: "fixture" }, subscription)).toEqual(subscription);
+    expect(nativeUsageCostUsd({ runDelta: { inputTokens: 30787, outputTokens: 5763, cacheReadTokens: 475008,
+      cacheWriteTokens: 0, providerCostUsd: 0.336842 } }, provider)).toBe(0.336842);
+  });
+
   it("reports the actual runtime billing identity", () => {
     expect(resolveNativeBilling({ kind: "opencode", model: "openrouter/deepseek/test", permissionMode: "allow" }))
       .toEqual({ provider: "deepseek", biller: "openrouter", billingType: "unknown" });
diff --git a/server/src/services/native-runtime/native-session-executor.ts b/server/src/services/native-runtime/native-session-executor.ts
index 939e0415066..7c85342d3bf 100644
--- a/server/src/services/native-runtime/native-session-executor.ts
+++ b/server/src/services/native-runtime/native-session-executor.ts
@@ -11011,6 +11011,9 @@ export function resolveNativeBilling(provider: NativeExecutionInput["provider"],
     const biller = nativeUsageBiller(provider);
     return { provider: biller, biller, billingType: "unknown" };
   }
+  if (provider.kind === "acpx" && provider.agent === "grok") {
+    return { provider: "xai", biller: "xai", billingType: env.XAI_API_KEY ? "metered_api" : "unknown" };
+  }
   if (provider.kind === "acpx" && provider.agent === "claude") {
     if (env.CLAUDE_CODE_USE_BEDROCK === "1") return { provider: "anthropic", biller: "aws_bedrock", billingType: "metered_api" };
     return { provider: "anthropic", biller: "anthropic", billingType: env.ANTHROPIC_API_KEY ? "metered_api" : env.CLAUDE_CODE_OAUTH_TOKEN ? "subscription_included" : "unknown" };
diff --git a/server/src/services/native-runtime/native-usage-accounting.ts b/server/src/services/native-runtime/native-usage-accounting.ts
index 8ef04b1da17..e4e95f12489 100644
--- a/server/src/services/native-runtime/native-usage-accounting.ts
+++ b/server/src/services/native-runtime/native-usage-accounting.ts
@@ -51,6 +51,7 @@ export function nativeUsageBiller(provider: NativeExecutionInput["provider"]): s
     if (provider.agent === "cursor") return "cursor";
     if (provider.agent === "copilot") return "github";
     if (provider.agent === "pi") return "openrouter";
+    if (provider.agent === "grok") return "xai";
   }
   return "openai";
 }