diff --git a/.changeset/cli-agent-one-shot-sessions.md b/.changeset/cli-agent-one-shot-sessions.md
new file mode 100644
index 0000000000..6c8b466079
--- /dev/null
+++ b/.changeset/cli-agent-one-shot-sessions.md
@@ -0,0 +1,21 @@
+---
+"@runfusion/fusion": minor
+---
+
+Add CLI-agent one-shot sessions for the validator, planning, and CE plugin
+surfaces (U9). A one-shot session runs an adapter's non-interactive invocation
+(`claude -p`, `codex exec --json`, `droid exec --output-format json`,
+`pi --print`) to completion in a working directory, streams output to a
+read-only terminal (input disabled server-side via the durable
+`autonomyPosture.readOnly` flag the transport's `isReadOnlySession` honors),
+parses the adapter's structured JSON result, and reaps the PTY on exit.
+
+The new `cli-agent/one-shot-session.ts` returns a typed result: a success with
+the parsed payload, or a typed failure (`nonzero-exit` / `unparseable` /
+`spawn-failed`) carrying a bounded output tail. The validator integration
+(`cli-agent-validator.ts`) maps results into the existing
+pass/fail/blocked/error verdict contract — a malformed or unparseable result
+maps to `error`, NEVER a silent pass. A planning seam (`runCliAgentPlanning`)
+maps one-shot output into the same `PlanningResponse` shape a model run
+produces, and the CE plugin's orchestrator threads an `executor` option
+(`model` | `cli-agent`) end-to-end to its resolver.
diff --git a/packages/dashboard/src/cli-session-transport.ts b/packages/dashboard/src/cli-session-transport.ts
index 9c12b102ec..933422c7ec 100644
--- a/packages/dashboard/src/cli-session-transport.ts
+++ b/packages/dashboard/src/cli-session-transport.ts
@@ -213,8 +213,9 @@ export class CliConfirmAdvanceRegistry {
  * Whether a session is read-only (one-shot validator/planning, U9). Server-side
  * enforcement (not just client) — input/inject is rejected for these.
  *
- * U9's one-shot sessions are not yet wired, so the current signal is the
- * autonomy posture `readOnly` flag (forward-compatible) plus validator/planning
+ * U9's one-shot sessions (validator/planning/CE) are wired via the engine's
+ * `runOneShotSession`, which persists the autonomy posture `readOnly` flag on
+ * the session record. This check honors that flag plus validator/planning
  * purposes which are inherently read-only.
  */
 export function isReadOnlySession(session: CliSession): boolean {
diff --git a/packages/engine/src/__tests__/cli-agent-validator.test.ts b/packages/engine/src/__tests__/cli-agent-validator.test.ts
new file mode 100644
index 0000000000..de2a4b1a8e
--- /dev/null
+++ b/packages/engine/src/__tests__/cli-agent-validator.test.ts
@@ -0,0 +1,153 @@
+import { describe, it, expect } from "vitest";
+import {
+  mapParsedToVerdict,
+  oneShotResultToVerdict,
+  normalizeVerdictToken,
+  inferVerdictFromProse,
+  runCliAgentValidation,
+} from "../cli-agent-validator.js";
+import type {
+  OneShotResult,
+  RunOneShotOptions,
+} from "../cli-agent/one-shot-session.js";
+
+function success(parsed: Record<string, unknown>, text = ""): OneShotResult {
+  return { ok: true, sessionId: "s1", parsed, text, rawOutput: JSON.stringify(parsed) };
+}
+
+describe("verdict token normalization", () => {
+  it("maps synonyms to the contract set", () => {
+    expect(normalizeVerdictToken("APPROVE")).toBe("pass");
+    expect(normalizeVerdictToken("passed")).toBe("pass");
+    expect(normalizeVerdictToken("REVISE")).toBe("fail");
+    expect(normalizeVerdictToken("blocked")).toBe("blocked");
+    expect(normalizeVerdictToken("nonsense")).toBeNull();
+  });
+});
+
+describe("mapParsedToVerdict — per-adapter shapes → verdicts", () => {
+  it("claude-shaped pass (is_error:false + verdict)", () => {
+    const v = mapParsedToVerdict({ type: "result", verdict: "pass", is_error: false }, "");
+    expect(v.status).toBe("pass");
+  });
+
+  it("claude-shaped error flag is authoritative", () => {
+    const v = mapParsedToVerdict({ is_error: true, result: "crashed" }, "");
+    expect(v.status).toBe("error");
+  });
+
+  it("boolean passed:false → fail", () => {
+    const v = mapParsedToVerdict({ passed: false, summary: "missing X" }, "");
+    expect(v.status).toBe("fail");
+    expect(v.summary).toBe("missing X");
+  });
+
+  it("explicit blocked flag → blocked with reason", () => {
+    const v = mapParsedToVerdict({ blocked: true, reason: "needs creds" }, "");
+    expect(v.status).toBe("blocked");
+    expect(v.blockedReason).toBe("needs creds");
+  });
+
+  it("status token + assertions array", () => {
+    const v = mapParsedToVerdict(
+      {
+        status: "fail",
+        assertions: [
+          { assertionId: "a1", passed: true },
+          { id: "a2", passed: false, message: "nope" },
+        ],
+      },
+      "",
+    );
+    expect(v.status).toBe("fail");
+    expect(v.assertions).toHaveLength(2);
+    expect(v.assertions[1]).toEqual({ assertionId: "a2", passed: false, message: "nope" });
+  });
+
+  it("prose-only pass inference", () => {
+    expect(inferVerdictFromProse("All assertions pass.")).toBe("pass");
+    const v = mapParsedToVerdict({}, "All assertions pass.");
+    expect(v.status).toBe("pass");
+  });
+
+  it("MALFORMED / undecidable → error, NEVER pass", () => {
+    const v = mapParsedToVerdict({ irrelevant: 1 }, "the agent rambled without a verdict");
+    expect(v.status).toBe("error");
+  });
+});
+
+describe("oneShotResultToVerdict — failures map to error", () => {
+  it("nonzero exit → error with stderr in summary", () => {
+    const v = oneShotResultToVerdict({
+      ok: false,
+      reason: "nonzero-exit",
+      sessionId: "s1",
+      exitCode: 1,
+      stderr: "segfault",
+      message: "exited with code 1",
+    });
+    expect(v.status).toBe("error");
+    expect(v.summary).toContain("segfault");
+  });
+
+  it("unparseable → error (never silent pass)", () => {
+    const v = oneShotResultToVerdict({
+      ok: false,
+      reason: "unparseable",
+      sessionId: "s1",
+      exitCode: 0,
+      stderr: "garbage",
+      message: "no decodable result",
+    });
+    expect(v.status).toBe("error");
+  });
+
+  it("success with pass verdict → pass", () => {
+    expect(oneShotResultToVerdict(success({ verdict: "pass" })).status).toBe("pass");
+  });
+});
+
+describe("runCliAgentValidation — seam threads purpose:validator and maps verdict", () => {
+  it("invokes runner with validator purpose and returns the verdict", async () => {
+    let seenPurpose: string | undefined;
+    const fakeRun = async (opts: RunOneShotOptions): Promise<OneShotResult> => {
+      seenPurpose = opts.purpose;
+      return success({ verdict: "pass", summary: "looks good" }, "looks good");
+    };
+    const verdict = await runCliAgentValidation(
+      {
+        manager: {} as RunOneShotOptions["manager"],
+        adapterId: "claude-code",
+        projectId: "p",
+        prompt: "validate",
+        cwd: "/tmp",
+      },
+      fakeRun as never,
+    );
+    expect(seenPurpose).toBe("validator");
+    expect(verdict.status).toBe("pass");
+    expect(verdict.summary).toBe("looks good");
+  });
+
+  it("runner failure surfaces as error verdict", async () => {
+    const fakeRun = async (): Promise<OneShotResult> => ({
+      ok: false,
+      reason: "spawn-failed",
+      sessionId: null,
+      exitCode: null,
+      stderr: "",
+      message: "ENOENT claude",
+    });
+    const verdict = await runCliAgentValidation(
+      {
+        manager: {} as RunOneShotOptions["manager"],
+        adapterId: "claude-code",
+        projectId: "p",
+        prompt: "validate",
+        cwd: "/tmp",
+      },
+      fakeRun as never,
+    );
+    expect(verdict.status).toBe("error");
+  });
+});
diff --git a/packages/engine/src/__tests__/interactive-ai-session.test.ts b/packages/engine/src/__tests__/interactive-ai-session.test.ts
index af876cfba7..86cf97e3f5 100644
--- a/packages/engine/src/__tests__/interactive-ai-session.test.ts
+++ b/packages/engine/src/__tests__/interactive-ai-session.test.ts
@@ -2,9 +2,61 @@ import { describe, expect, it, vi } from "vitest";
 import type { PlanningQuestion, PlanningResponse } from "@fusion/core";
 import {
   createInteractiveAiSessionWith,
+  runCliAgentPlanning,
   type InteractiveAgentResult,
   type InteractiveAgentSession,
 } from "../interactive-ai-session.js";
+import type {
+  OneShotResult,
+  RunOneShotOptions,
+} from "../cli-agent/one-shot-session.js";
+
+describe("runCliAgentPlanning (U9 one-shot planning seam)", () => {
+  const baseOpts = {
+    manager: {} as RunOneShotOptions["manager"],
+    adapterId: "claude-code",
+    projectId: "p",
+    prompt: "plan it",
+    cwd: "/tmp",
+  };
+
+  it("maps one-shot output to the SAME PlanningResponse shape a model run produces", async () => {
+    let seenPurpose: string | undefined;
+    const fakeRun = async (opts: RunOneShotOptions): Promise<OneShotResult> => {
+      seenPurpose = opts.purpose;
+      const summary = {
+        title: "Do X",
+        description: "Plan to do X",
+        suggestedSize: "M",
+        suggestedDependencies: [],
+        keyDeliverables: ["X"],
+      };
+      return {
+        ok: true,
+        sessionId: "s1",
+        parsed: {},
+        text: JSON.stringify({ type: "complete", data: summary }),
+        rawOutput: "",
+      };
+    };
+    const resp: PlanningResponse = await runCliAgentPlanning(baseOpts, fakeRun as never);
+    expect(seenPurpose).toBe("planning");
+    expect(resp.type).toBe("complete");
+    if (resp.type === "complete") expect(resp.data.title).toBe("Do X");
+  });
+
+  it("throws on a failed one-shot (never returns a fabricated plan)", async () => {
+    const fakeRun = async (): Promise<OneShotResult> => ({
+      ok: false,
+      reason: "unparseable",
+      sessionId: "s1",
+      exitCode: 0,
+      stderr: "",
+      message: "no result",
+    });
+    await expect(runCliAgentPlanning(baseOpts, fakeRun as never)).rejects.toThrow(/planning/i);
+  });
+});
 
 /**
  * A scripted fake agent: each `prompt()` advances through a queue of canned
diff --git a/packages/engine/src/cli-agent-validator.ts b/packages/engine/src/cli-agent-validator.ts
new file mode 100644
index 0000000000..8f950f2dfb
--- /dev/null
+++ b/packages/engine/src/cli-agent-validator.ts
@@ -0,0 +1,183 @@
+/**
+ * CLI-agent validator integration (CLI Agent Executor, U9).
+ *
+ * Bridges a one-shot CLI agent session into the existing validator verdict
+ * contract (`ValidationResult` in mission-execution-loop.ts:
+ * `status: "pass" | "fail" | "blocked" | "error"`).
+ *
+ * The cardinal rule: a malformed / unparseable / nonzero-exit one-shot maps to
+ * `error`, NEVER a silent `pass`. The verdict must be indistinguishable
+ * downstream from a model-executed validation run.
+ */
+
+import type {
+  OneShotResult,
+  RunOneShotOptions,
+  runOneShotSession as RunOneShotFn,
+} from "./cli-agent/one-shot-session.js";
+
+/** The validator verdict contract shared with model-executed runs. */
+export interface ValidatorVerdict {
+  status: "pass" | "fail" | "blocked" | "error";
+  /** Per-assertion results (empty when the adapter reports a bare verdict). */
+  assertions: Array<{ assertionId: string; passed: boolean; message?: string }>;
+  summary: string;
+  blockedReason?: string;
+}
+
+/**
+ * A structured verdict an adapter may emit in its one-shot JSON result. We look
+ * for these fields on the parsed payload (in priority order) before falling
+ * back to prose inference on the `text` field.
+ */
+interface ParsedVerdictShape {
+  verdict?: unknown;
+  status?: unknown;
+  result?: unknown;
+  passed?: unknown;
+  blocked?: unknown;
+  is_error?: unknown;
+  summary?: unknown;
+  reason?: unknown;
+  assertions?: unknown;
+}
+
+/** Normalize a free-form verdict token to the contract's status set. */
+export function normalizeVerdictToken(token: string): ValidatorVerdict["status"] | null {
+  const t = token.trim().toLowerCase();
+  if (["pass", "passed", "approve", "approved", "ok", "success"].includes(t)) return "pass";
+  if (["fail", "failed", "revise", "reject", "rejected", "failure"].includes(t)) return "fail";
+  if (["blocked", "block", "unavailable"].includes(t)) return "blocked";
+  if (["error", "errored"].includes(t)) return "error";
+  return null;
+}
+
+/**
+ * Map a parsed one-shot result payload into a validator verdict.
+ *
+ * Precedence:
+ *  1. explicit `verdict`/`status` string token (normalized)
+ *  2. boolean `passed` (true→pass, false→fail) and `blocked === true`
+ *  3. `is_error === true` → error (claude-shaped)
+ *  4. prose inference from the result text
+ *  5. nothing decodable → error (NEVER pass)
+ */
+export function mapParsedToVerdict(
+  parsed: Record<string, unknown>,
+  text: string,
+): ValidatorVerdict {
+  const p = parsed as ParsedVerdictShape;
+  const summary =
+    (typeof p.summary === "string" && p.summary) ||
+    (typeof p.reason === "string" && p.reason) ||
+    text ||
+    "";
+  const assertions = parseAssertions(p.assertions);
+
+  // 3 (early): an adapter error flag is authoritative.
+  if (p.is_error === true) {
+    return { status: "error", assertions, summary: summary || "Adapter reported an error" };
+  }
+
+  // 2: explicit blocked flag.
+  if (p.blocked === true) {
+    return {
+      status: "blocked",
+      assertions,
+      summary: summary || "Validation blocked",
+      blockedReason: typeof p.reason === "string" ? p.reason : summary || "blocked",
+    };
+  }
+
+  // 1: explicit verdict / status token.
+  for (const candidate of [p.verdict, p.status, p.result]) {
+    if (typeof candidate === "string") {
+      const status = normalizeVerdictToken(candidate);
+      if (status) {
+        return status === "blocked"
+          ? { status, assertions, summary: summary || "Validation blocked", blockedReason: summary }
+          : { status, assertions, summary };
+      }
+    }
+  }
+
+  // 2 (boolean): passed flag.
+  if (typeof p.passed === "boolean") {
+    return { status: p.passed ? "pass" : "fail", assertions, summary };
+  }
+
+  // 4: prose inference.
+  const inferred = inferVerdictFromProse(text);
+  if (inferred) return { status: inferred, assertions, summary: summary || text };
+
+  // 5: undecidable → error, never a silent pass.
+  return {
+    status: "error",
+    assertions,
+    summary: summary || "Validator produced no decodable verdict",
+  };
+}
+
+function parseAssertions(raw: unknown): ValidatorVerdict["assertions"] {
+  if (!Array.isArray(raw)) return [];
+  const out: ValidatorVerdict["assertions"] = [];
+  for (const item of raw) {
+    if (!item || typeof item !== "object") continue;
+    const a = item as Record<string, unknown>;
+    const assertionId =
+      typeof a.assertionId === "string"
+        ? a.assertionId
+        : typeof a.id === "string"
+          ? a.id
+          : null;
+    if (!assertionId) continue;
+    out.push({
+      assertionId,
+      passed: a.passed === true,
+      message: typeof a.message === "string" ? a.message : undefined,
+    });
+  }
+  return out;
+}
+
+/** Conservative prose inference. Only confident phrasings map to a verdict. */
+export function inferVerdictFromProse(text: string): ValidatorVerdict["status"] | null {
+  const t = text.toLowerCase();
+  if (/\bblocked\b/.test(t)) return "blocked";
+  if (/\b(revise|revision requested|does not (pass|meet)|fail(s|ed)?\b)/.test(t)) return "fail";
+  if (/\b(all (assertions|checks) pass|validation pass(ed)?|approve(d)?)\b/.test(t)) return "pass";
+  return null;
+}
+
+/**
+ * Convert any one-shot result (success or failure) into a validator verdict.
+ * Failures (nonzero exit, unparseable, spawn-failed) → `error` with the bounded
+ * stderr folded into the summary.
+ */
+export function oneShotResultToVerdict(result: OneShotResult): ValidatorVerdict {
+  if (!result.ok) {
+    return {
+      status: "error",
+      assertions: [],
+      summary: `${result.message}${result.stderr ? `\n--- output tail ---\n${result.stderr}` : ""}`,
+    };
+  }
+  return mapParsedToVerdict(result.parsed, result.text);
+}
+
+/**
+ * Run a CLI-agent one-shot validation and map it to the verdict contract.
+ *
+ * This is the integration seam mission-execution-loop's `runValidation` branches
+ * to when the resolved validator executor is a CLI agent (adapter-backed) rather
+ * than a model. The `run` parameter is injected so this is unit-testable without
+ * a live PTY (tests pass a stubbed runner; production passes
+ * `runOneShotSession`).
+ */
+export async function runCliAgentValidation(
+  opts: Omit<RunOneShotOptions, "purpose">,
+  run: typeof RunOneShotFn,
+): Promise<ValidatorVerdict> {
+  const result = await run({ ...opts, purpose: "validator" });
+  return oneShotResultToVerdict(result);
+}
diff --git a/packages/engine/src/cli-agent/__tests__/one-shot-session.test.ts b/packages/engine/src/cli-agent/__tests__/one-shot-session.test.ts
new file mode 100644
index 0000000000..9577d7c149
--- /dev/null
+++ b/packages/engine/src/cli-agent/__tests__/one-shot-session.test.ts
@@ -0,0 +1,283 @@
+import { describe, it, expect, afterEach } from "vitest";
+import { mkdtempSync } from "node:fs";
+import { join } from "node:path";
+import { tmpdir } from "node:os";
+import { rm } from "node:fs/promises";
+import { Database, CliSessionStore, type CliSession } from "@fusion/core";
+import type { IPty } from "node-pty";
+import { CliSessionManager } from "../session-manager.js";
+import { CliAdapterRegistry, type CliAgentAdapter } from "../adapter.js";
+import {
+  runOneShotSession,
+  parseOneShotOutput,
+  extractJsonObjects,
+  buildOneShotSettings,
+  boundedStderrTail,
+  ONE_SHOT_STDERR_CAP_BYTES,
+} from "../one-shot-session.js";
+
+/**
+ * Mirror of the dashboard transport's isReadOnlySession contract (asserted here
+ * without an engine→dashboard dependency): validator/planning are inherently
+ * read-only, and `autonomyPosture.readOnly === true` is an explicit flag.
+ */
+function isReadOnlySession(session: CliSession): boolean {
+  if (session.autonomyPosture && session.autonomyPosture.readOnly === true) return true;
+  return session.purpose === "validator" || session.purpose === "planning";
+}
+
+// ── Mock PTY at the loadPtyModule seam ─────────────────────────────────────
+
+interface MockPty extends IPty {
+  written: string[];
+  killed: boolean;
+  emitData(data: string): void;
+  emitExit(exitCode: number, signal?: number): void;
+}
+
+interface MockState {
+  ptys: MockPty[];
+}
+
+function makeMockPtyModule(state: MockState): typeof import("node-pty") {
+  return {
+    spawn(_file: string, _args: string[] | string, options: { env?: { [k: string]: string } }) {
+      let dataCb: ((d: string) => void) | undefined;
+      let exitCb: ((e: { exitCode: number; signal?: number }) => void) | undefined;
+      const mock: MockPty = {
+        pid: 2000 + state.ptys.length,
+        cols: 80,
+        rows: 24,
+        process: "mock",
+        handleFlowControl: false,
+        written: [],
+        killed: false,
+        spawnEnv: (options.env ?? {}) as { [k: string]: string },
+        onData: (cb: (d: string) => void) => {
+          dataCb = cb;
+          return { dispose() {} };
+        },
+        onExit: (cb: (e: { exitCode: number; signal?: number }) => void) => {
+          exitCb = cb;
+          return { dispose() {} };
+        },
+        on() {},
+        write(data: string) {
+          mock.written.push(data);
+        },
+        resize() {},
+        clear() {},
+        kill() {
+          mock.killed = true;
+        },
+        pause() {},
+        resume() {},
+        emitData(d: string) {
+          dataCb?.(d);
+        },
+        emitExit(exitCode: number, signal?: number) {
+          exitCb?.({ exitCode, signal });
+        },
+      } as unknown as MockPty;
+      state.ptys.push(mock);
+      return mock as unknown as IPty;
+    },
+  } as unknown as typeof import("node-pty");
+}
+
+// ── Test adapter: one-shot forms exit immediately (no readiness gate). ───────
+
+function makeAdapter(id: string): CliAgentAdapter {
+  return {
+    id,
+    name: `Test ${id}`,
+    capabilities: {
+      nativeDone: true,
+      nativeWaiting: false,
+      transcriptSource: "event-stream",
+      supportsResume: false,
+    },
+    buildLaunch: (ctx) => ({
+      command: id,
+      args: (ctx.settings.oneShotArgs as string[] | undefined) ?? [],
+    }),
+    buildEnvAllowlist: () => ["PATH"],
+    // One-shot output is non-interactive; readiness is immediately true so the
+    // generic injection fallback (if any) doesn't hang.
+    createReadinessDetector: () => ({ observe: () => true }),
+    formatInjection: (text) => ({ payload: `${text}\r` }),
+  };
+}
+
+interface Harness {
+  manager: CliSessionManager;
+  store: CliSessionStore;
+  state: MockState;
+  db: Database;
+  tmpDir: string;
+}
+
+function makeHarness(adapterIds: string[]): Harness {
+  const tmpDir = mkdtempSync(join(tmpdir(), "kb-oneshot-test-"));
+  const fusionDir = join(tmpDir, ".fusion");
+  const db = new Database(fusionDir, { inMemory: true });
+  db.init();
+  const store = new CliSessionStore(fusionDir, db);
+  const registry = new CliAdapterRegistry();
+  for (const id of adapterIds) registry.register(makeAdapter(id));
+  const state: MockState = { ptys: [] };
+  const manager = new CliSessionManager({
+    registry,
+    store,
+    loadPty: async () => makeMockPtyModule(state),
+  });
+  return { manager, store, state, db, tmpDir };
+}
+
+/**
+ * Run a one-shot, then once the PTY exists drive its output + exit. Returns the
+ * resolved one-shot result.
+ */
+async function runWith(
+  h: Harness,
+  adapterId: string,
+  purpose: "validator" | "planning" | "ce",
+  output: string,
+  exitCode: number,
+) {
+  const promise = runOneShotSession({
+    manager: h.manager,
+    adapterId,
+    projectId: "proj-1",
+    purpose,
+    prompt: "do the thing",
+    cwd: h.tmpDir,
+    taskId: "FN-1",
+  });
+  // Wait a tick for spawn + attach to settle, then drive the mock PTY.
+  await new Promise((r) => setTimeout(r, 5));
+  const pty = h.state.ptys[h.state.ptys.length - 1];
+  if (output) pty.emitData(output);
+  pty.emitExit(exitCode);
+  return promise;
+}
+
+describe("one-shot session output parsing", () => {
+  it("buildOneShotSettings carries each adapter's documented non-interactive args", () => {
+    expect(buildOneShotSettings("claude-code", "P").oneShotArgs).toEqual(["-p", "P"]);
+    expect(buildOneShotSettings("codex", "P").oneShotArgs).toEqual(["exec", "--json", "P"]);
+    expect(buildOneShotSettings("droid", "P").oneShotArgs).toEqual([
+      "exec",
+      "--output-format",
+      "json",
+      "P",
+    ]);
+    expect(buildOneShotSettings("pi", "P").oneShotArgs).toEqual(["--print", "P"]);
+  });
+
+  it("extractJsonObjects handles JSONL and embedded pretty JSON", () => {
+    expect(extractJsonObjects('{"a":1}\n{"b":2}\n')).toHaveLength(2);
+    expect(extractJsonObjects('banner\n{\n "x": 5\n}\ntrailer')).toEqual([{ x: 5 }]);
+    expect(extractJsonObjects("no json here")).toEqual([]);
+  });
+
+  it("parseOneShotOutput picks the claude result frame", () => {
+    const out = '{"type":"system"}\n{"type":"result","result":"done","is_error":false}';
+    const parsed = parseOneShotOutput("claude-code", out);
+    expect(parsed?.text).toBe("done");
+    expect(parsed?.parsed.type).toBe("result");
+  });
+
+  it("boundedStderrTail caps very long output", () => {
+    const big = "x".repeat(ONE_SHOT_STDERR_CAP_BYTES + 100);
+    expect(Buffer.byteLength(boundedStderrTail(big))).toBeLessThanOrEqual(
+      ONE_SHOT_STDERR_CAP_BYTES,
+    );
+  });
+});
+
+describe("one-shot session lifecycle", () => {
+  let harnesses: Harness[] = [];
+  afterEach(async () => {
+    for (const h of harnesses) {
+      h.manager.dispose();
+      h.db.close();
+      await rm(h.tmpDir, { recursive: true, force: true });
+    }
+    harnesses = [];
+  });
+  function newHarness(ids: string[]): Harness {
+    const h = makeHarness(ids);
+    harnesses.push(h);
+    return h;
+  }
+
+  it("creates a read-only session record, streams terminal output, reaps on completion", async () => {
+    const h = newHarness(["claude-code"]);
+    let captured: CliSession | null = null;
+    const result = await (async () => {
+      const promise = runOneShotSession({
+        manager: h.manager,
+        adapterId: "claude-code",
+        projectId: "proj-1",
+        purpose: "validator",
+        prompt: "p",
+        cwd: h.tmpDir,
+      });
+      await new Promise((r) => setTimeout(r, 5));
+      const pty = h.state.ptys[0];
+      // While live, the session record exists and is read-only, terminal streams.
+      const sessions = h.store.listSessions({ projectId: "proj-1" });
+      captured = sessions[0] ?? null;
+      pty.emitData('{"type":"result","result":"ok","is_error":false}');
+      pty.emitExit(0);
+      return promise;
+    })();
+
+    expect(captured).not.toBeNull();
+    expect(isReadOnlySession(captured!)).toBe(true);
+    expect(result.ok).toBe(true);
+    // Reaped: no longer live.
+    expect(h.manager.isLive(captured!.id)).toBe(false);
+    const after = h.store.getSession(captured!.id);
+    expect(after?.agentState).toBe("dead");
+  });
+
+  it("nonzero exit → failure with bounded stderr tail", async () => {
+    const h = newHarness(["codex"]);
+    const result = await runWith(h, "codex", "validator", "boom: fatal error\n", 1);
+    expect(result.ok).toBe(false);
+    if (!result.ok) {
+      expect(result.reason).toBe("nonzero-exit");
+      expect(result.exitCode).toBe(1);
+      expect(result.stderr).toContain("boom: fatal error");
+    }
+  });
+
+  it("unparseable output → typed unparseable failure (never silent success)", async () => {
+    const h = newHarness(["droid"]);
+    const result = await runWith(h, "droid", "validator", "not json at all", 0);
+    expect(result.ok).toBe(false);
+    if (!result.ok) expect(result.reason).toBe("unparseable");
+  });
+
+  it("ce purpose is read-only via posture flag", async () => {
+    const h = newHarness(["pi"]);
+    const promise = runOneShotSession({
+      manager: h.manager,
+      adapterId: "pi",
+      projectId: "proj-1",
+      purpose: "ce",
+      prompt: "p",
+      cwd: h.tmpDir,
+    });
+    await new Promise((r) => setTimeout(r, 5));
+    const session = h.store.listSessions({ projectId: "proj-1" })[0];
+    expect(session.purpose).toBe("ce");
+    expect(isReadOnlySession(session)).toBe(true);
+    const pty = h.state.ptys[0];
+    pty.emitData('{"text":"hi"}');
+    pty.emitExit(0);
+    await promise;
+  });
+});
diff --git a/packages/engine/src/cli-agent/one-shot-session.ts b/packages/engine/src/cli-agent/one-shot-session.ts
new file mode 100644
index 0000000000..7d9c58270f
--- /dev/null
+++ b/packages/engine/src/cli-agent/one-shot-session.ts
@@ -0,0 +1,378 @@
+/**
+ * One-shot CLI agent sessions (CLI Agent Executor, U9).
+ *
+ * A *one-shot* session runs an adapter's NON-INTERACTIVE invocation
+ * (`claude -p`, `codex exec --json`, `droid exec --output-format json`,
+ * `pi --print`) to completion in a working directory, streams its output to a
+ * read-only terminal (so U10's attach surface works exactly as for interactive
+ * sessions — but with input disabled server-side), collects the output, parses
+ * the adapter's structured (JSON) result, and returns a typed result.
+ *
+ * Read-only enforcement: the dashboard transport's `isReadOnlySession` treats
+ * `validator`/`planning` purposes as inherently read-only, and ALSO honors an
+ * `autonomyPosture.readOnly === true` flag. One-shot sessions persist that flag
+ * unconditionally so a `ce` (or any future) purpose is read-only too — the flag
+ * is the durable, transport-readable signal, not a transient client hint.
+ *
+ * Design notes:
+ * - The non-interactive command is built by `buildOneShotLaunch`, keyed off the
+ *   adapter id. The interactive adapter launch builders intentionally don't
+ *   model the `-p`/`exec` forms (those drive a REPL); one-shot is a distinct
+ *   invocation that produces a single machine-readable result and exits.
+ * - Output is merged stdout+stderr (a PTY has a single stream). The structured
+ *   result is parsed from that stream per adapter. On a nonzero exit or an
+ *   unparseable result we return a typed failure carrying a BOUNDED tail of the
+ *   output as `stderr` (the best available diagnostic on a PTY).
+ * - The PTY is reaped on completion: spawn → wait-for-exit → the session
+ *   manager has already removed the live session and closed streams by the time
+ *   `waitForExit` resolves.
+ */
+
+import type { CliSessionPurpose } from "@fusion/core";
+
+import type { CliSessionManager } from "./session-manager.js";
+
+// ── Bounds ────────────────────────────────────────────────────────────────
+
+/** Maximum bytes of output retained for diagnostics on a failed one-shot. */
+export const ONE_SHOT_STDERR_CAP_BYTES = 8 * 1024;
+
+// ── One-shot launch (non-interactive command builder) ───────────────────────
+
+/** A non-interactive invocation: command + args (the prompt is passed inline). */
+export interface OneShotLaunchSpec {
+  /** Adapter-specific extra args appended after the adapter's one-shot base. */
+  extraArgs?: readonly string[];
+  /** Adapter-specific settings forwarded to the session manager's spawn. */
+  settings: Record<string, unknown>;
+}
+
+/**
+ * Per-adapter one-shot settings. Each adapter's interactive `buildLaunch`
+ * consults `settings`; one-shot mode flags the non-interactive form there.
+ *
+ * The flag (`oneShot: true`) plus the documented per-adapter args are forwarded
+ * verbatim as launch settings. Adapters that don't yet branch on `oneShot`
+ * still receive the prompt via injection fallback (see runOneShotSession).
+ */
+export function buildOneShotSettings(
+  adapterId: string,
+  prompt: string,
+  base: Record<string, unknown> = {},
+): Record<string, unknown> {
+  const settings: Record<string, unknown> = { ...base, oneShot: true, oneShotPrompt: prompt };
+  // The non-interactive arg sets are documented in each adapter file. We carry
+  // them as explicit extraArgs so the session manager forwards them to spawn.
+  switch (adapterId) {
+    case "claude-code":
+      settings.oneShotArgs = ["-p", prompt];
+      break;
+    case "codex":
+      settings.oneShotArgs = ["exec", "--json", prompt];
+      break;
+    case "droid":
+      settings.oneShotArgs = ["exec", "--output-format", "json", prompt];
+      break;
+    case "pi":
+      settings.oneShotArgs = ["--print", prompt];
+      break;
+    default:
+      // generic / unknown: no structured form; prompt is injected.
+      settings.oneShotArgs = [];
+      break;
+  }
+  return settings;
+}
+
+// ── Structured one-shot result ──────────────────────────────────────────────
+
+/** A successfully parsed one-shot result. */
+export interface OneShotSuccess {
+  ok: true;
+  /** The session record id (for terminal attach / audit). */
+  sessionId: string;
+  /** Free-form structured payload parsed from the adapter's JSON output. */
+  parsed: Record<string, unknown>;
+  /** The text/result field the adapter surfaced (best-effort). */
+  text: string;
+  /** Full captured output (bounded by scrollback). */
+  rawOutput: string;
+}
+
+/** Reason a one-shot failed. */
+export type OneShotFailureReason = "nonzero-exit" | "unparseable" | "spawn-failed";
+
+/** A typed one-shot failure — NEVER mistaken for a pass downstream. */
+export interface OneShotFailure {
+  ok: false;
+  reason: OneShotFailureReason;
+  /** The session record id, when a session was created. */
+  sessionId: string | null;
+  /** Process exit code, when the process ran. */
+  exitCode: number | null;
+  /** Bounded diagnostic tail of the merged PTY output. */
+  stderr: string;
+  /** Human-readable message. */
+  message: string;
+}
+
+export type OneShotResult = OneShotSuccess | OneShotFailure;
+
+// ── Per-adapter result parsing ──────────────────────────────────────────────
+
+/**
+ * Parse the structured result out of an adapter's one-shot output. Each adapter
+ * emits JSON on its non-interactive path; the PTY merges it with any banner
+ * lines, so we scan for the LAST decodable JSON object/array on the stream and
+ * normalize a `text` field per adapter shape.
+ *
+ * Returns null when no decodable structured result is present (→ unparseable).
+ */
+export function parseOneShotOutput(
+  adapterId: string,
+  output: string,
+): { parsed: Record<string, unknown>; text: string } | null {
+  const objects = extractJsonObjects(output);
+  if (objects.length === 0) return null;
+
+  switch (adapterId) {
+    case "claude-code": {
+      // `claude -p --output-format json` (or stream-json) → a result object
+      // with `{ type: "result", result | text, is_error }`. Prefer the final
+      // result frame.
+      const result =
+        objects.find((o) => o.type === "result") ?? objects[objects.length - 1];
+      const text =
+        pickString(result, ["result", "text", "content", "message"]) ?? "";
+      return { parsed: result, text };
+    }
+    case "codex": {
+      // `codex exec --json` emits a stream of JSON events; the final
+      // agent/assistant message carries the answer.
+      const last = objects[objects.length - 1];
+      const text = pickString(last, ["text", "message", "content", "result"]) ?? "";
+      return { parsed: last, text };
+    }
+    case "droid": {
+      // `droid exec --output-format json` → a single result object.
+      const last = objects[objects.length - 1];
+      const text = pickString(last, ["result", "text", "message", "output"]) ?? "";
+      return { parsed: last, text };
+    }
+    case "pi": {
+      const last = objects[objects.length - 1];
+      const text = pickString(last, ["text", "result", "message", "content"]) ?? "";
+      return { parsed: last, text };
+    }
+    default: {
+      const last = objects[objects.length - 1];
+      const text = pickString(last, ["text", "result", "message"]) ?? "";
+      return { parsed: last, text };
+    }
+  }
+}
+
+/** Pull the first present string field from a parsed object. */
+function pickString(obj: Record<string, unknown>, keys: string[]): string | null {
+  for (const k of keys) {
+    const v = obj[k];
+    if (typeof v === "string" && v.length > 0) return v;
+  }
+  return null;
+}
+
+/**
+ * Extract decodable top-level JSON objects from a (possibly noisy, possibly
+ * line-delimited) output stream. Handles both JSONL (one object per line) and a
+ * single pretty-printed object embedded in banner text.
+ */
+export function extractJsonObjects(output: string): Record<string, unknown>[] {
+  const objects: Record<string, unknown>[] = [];
+  // First try JSONL: each non-empty line that decodes to an object.
+  let sawLineJson = false;
+  for (const line of output.split(/\r?\n/)) {
+    const trimmed = line.trim();
+    if (!trimmed || (trimmed[0] !== "{" && trimmed[0] !== "[")) continue;
+    try {
+      const v = JSON.parse(trimmed);
+      if (v && typeof v === "object") {
+        objects.push(v as Record<string, unknown>);
+        sawLineJson = true;
+      }
+    } catch {
+      // not a standalone JSON line; fall through to brace scanning below.
+    }
+  }
+  if (sawLineJson) return objects;
+
+  // Fallback: brace-balanced scan for a single embedded JSON object.
+  const start = output.indexOf("{");
+  const end = output.lastIndexOf("}");
+  if (start >= 0 && end > start) {
+    try {
+      const v = JSON.parse(output.slice(start, end + 1));
+      if (v && typeof v === "object") objects.push(v as Record<string, unknown>);
+    } catch {
+      // unparseable
+    }
+  }
+  return objects;
+}
+
+// ── Runner ──────────────────────────────────────────────────────────────────
+
+export interface RunOneShotOptions {
+  manager: CliSessionManager;
+  adapterId: string;
+  projectId: string;
+  /** validator | planning | ce (chat/execute are interactive, not one-shot). */
+  purpose: Extract<CliSessionPurpose, "validator" | "planning" | "ce">;
+  prompt: string;
+  /** Working directory the CLI runs in (also the PTY cwd). */
+  cwd: string;
+  taskId?: string | null;
+  chatSessionId?: string | null;
+  /** Extra adapter launch settings (model, profile…). Merged under one-shot. */
+  settings?: Record<string, unknown>;
+  /** Optional overall timeout (ms). On timeout the session is killed → failure. */
+  timeoutMs?: number;
+}
+
+/**
+ * Run an adapter's one-shot invocation to completion and return a typed result.
+ *
+ * Lifecycle: spawn (read-only record) → attach (collect output for the
+ * read-only terminal + parsing) → wait for exit → parse → reap. On nonzero exit
+ * or unparseable output, returns a typed {@link OneShotFailure} with a bounded
+ * output tail — NEVER a silent success.
+ */
+export async function runOneShotSession(opts: RunOneShotOptions): Promise<OneShotResult> {
+  const {
+    manager,
+    adapterId,
+    projectId,
+    purpose,
+    prompt,
+    cwd,
+    taskId = null,
+    chatSessionId = null,
+    timeoutMs,
+  } = opts;
+
+  const settings = buildOneShotSettings(adapterId, prompt, opts.settings ?? {});
+
+  let sessionId: string | null = null;
+  try {
+    const record = await manager.spawn({
+      adapterId,
+      projectId,
+      purpose,
+      taskId,
+      chatSessionId,
+      worktreePath: cwd,
+      // Durable, transport-readable read-only flag. validator/planning are
+      // already inherently read-only; this makes `ce` (and any future purpose)
+      // read-only too. See isReadOnlySession in the dashboard transport.
+      posture: { readOnly: true },
+      settings,
+    });
+    sessionId = record.id;
+  } catch (err) {
+    return {
+      ok: false,
+      reason: "spawn-failed",
+      sessionId,
+      exitCode: null,
+      stderr: "",
+      message: err instanceof Error ? err.message : String(err),
+    };
+  }
+
+  // Attach to collect output (also exercises the read-only terminal stream).
+  const attachment = manager.attach(sessionId);
+  const chunks: Buffer[] = [];
+  // Replay scrollback captured at attach (usually empty for a fresh spawn).
+  if (attachment.scrollback.byteLength > 0) {
+    chunks.push(Buffer.from(attachment.scrollback));
+  }
+  const drainPromise = (async () => {
+    for await (const bytes of attachment.stream) {
+      chunks.push(Buffer.from(bytes));
+    }
+  })();
+
+  // For adapters whose one-shot form is NOT carried in args (generic fallback),
+  // inject the prompt once ready. Adapters that consume the prompt via args
+  // (claude/codex/droid/pi) ignore this — they already have it on argv.
+  if (adapterId === "generic") {
+    try {
+      await manager.inject(sessionId, prompt);
+    } catch {
+      // session may exit immediately for non-interactive forms; ignore.
+    }
+  }
+
+  let timer: NodeJS.Timeout | undefined;
+  let timedOut = false;
+  const exitPromise = manager.waitForExit(sessionId);
+  const exit = await (timeoutMs && timeoutMs > 0
+    ? Promise.race([
+        exitPromise,
+        new Promise<{ exitCode: number; signal: number | undefined }>((resolve) => {
+          timer = setTimeout(() => {
+            timedOut = true;
+            manager.kill(sessionId as string, "killed");
+            resolve({ exitCode: -1, signal: 9 });
+          }, timeoutMs);
+        }),
+      ])
+    : exitPromise);
+  if (timer) clearTimeout(timer);
+
+  // Ensure the stream is fully drained before reading output.
+  attachment.detach();
+  await drainPromise.catch(() => undefined);
+
+  const rawOutput = Buffer.concat(chunks).toString("utf8");
+  const boundedTail = boundedStderrTail(rawOutput);
+
+  if (exit.exitCode !== 0 || timedOut) {
+    return {
+      ok: false,
+      reason: "nonzero-exit",
+      sessionId,
+      exitCode: exit.exitCode,
+      stderr: boundedTail,
+      message: timedOut
+        ? `one-shot ${adapterId} session timed out after ${timeoutMs}ms`
+        : `one-shot ${adapterId} session exited with code ${exit.exitCode}`,
+    };
+  }
+
+  const parsedResult = parseOneShotOutput(adapterId, rawOutput);
+  if (!parsedResult) {
+    return {
+      ok: false,
+      reason: "unparseable",
+      sessionId,
+      exitCode: exit.exitCode,
+      stderr: boundedTail,
+      message: `one-shot ${adapterId} produced no decodable structured result`,
+    };
+  }
+
+  return {
+    ok: true,
+    sessionId,
+    parsed: parsedResult.parsed,
+    text: parsedResult.text,
+    rawOutput,
+  };
+}
+
+/** Bounded tail of merged output, for failure diagnostics. */
+export function boundedStderrTail(output: string): string {
+  const buf = Buffer.from(output, "utf8");
+  if (buf.byteLength <= ONE_SHOT_STDERR_CAP_BYTES) return output;
+  return buf.subarray(buf.byteLength - ONE_SHOT_STDERR_CAP_BYTES).toString("utf8");
+}
diff --git a/packages/engine/src/cli-agent/session-manager.ts b/packages/engine/src/cli-agent/session-manager.ts
index ba3b50cd90..194835645a 100644
--- a/packages/engine/src/cli-agent/session-manager.ts
+++ b/packages/engine/src/cli-agent/session-manager.ts
@@ -320,6 +320,10 @@ interface LiveSession {
   terminated: boolean;
   /** Bytes buffered toward the high watermark since last drain to consumers. */
   inflightBytes: number;
+  /** Captured exit result (set once on exit/kill), for one-shot waiters. */
+  exitResult: { exitCode: number; signal: number | undefined } | null;
+  /** Resolvers waiting on process exit (one-shot sessions). */
+  exitWaiters: ((result: { exitCode: number; signal: number | undefined }) => void)[];
 }
 
 // ── Manager options ──────────────────────────────────────────────────────────
@@ -456,6 +460,8 @@ export class CliSessionManager {
       paused: false,
       terminated: false,
       inflightBytes: 0,
+      exitResult: null,
+      exitWaiters: [],
     };
     this.sessions.set(record.id, live);
 
@@ -535,10 +541,19 @@ export class CliSessionManager {
     }
   }
 
+  /** Settle one-shot exit waiters exactly once with the captured result. */
+  private settleExit(live: LiveSession, exitCode: number, signal: number | undefined): void {
+    if (live.exitResult) return;
+    live.exitResult = { exitCode, signal };
+    const waiters = live.exitWaiters.splice(0);
+    for (const w of waiters) w(live.exitResult);
+  }
+
   private handleExit(live: LiveSession, exitCode: number, signal?: number): void {
     if (live.terminated) return;
     live.terminated = true;
     this.sessions.delete(live.id);
+    this.settleExit(live, exitCode, signal);
 
     for (const stream of live.streams) stream.close();
     live.streams.clear();
@@ -578,6 +593,19 @@ export class CliSessionManager {
     return new Promise((resolve) => live.readyWaiters.push(resolve));
   }
 
+  /**
+   * Resolve once the session's PTY has exited (or been killed), yielding the
+   * captured exit result. Powers one-shot (validator/planning/CE) sessions that
+   * run a non-interactive invocation to completion. A killed session resolves
+   * with `{ exitCode: -1, signal: 9 }`. Throws if the session id is unknown AND
+   * not already exited within this manager's memory.
+   */
+  waitForExit(sessionId: string): Promise<{ exitCode: number; signal: number | undefined }> {
+    const live = this.require(sessionId);
+    if (live.exitResult) return Promise.resolve(live.exitResult);
+    return new Promise((resolve) => live.exitWaiters.push(resolve));
+  }
+
   // ── Injection ──────────────────────────────────────────────────────────
 
   /**
@@ -763,6 +791,8 @@ export class CliSessionManager {
     }
     live.terminated = true;
     this.sessions.delete(live.id);
+    // A killed PTY exited via signal — surface a nonzero result to one-shot waiters.
+    this.settleExit(live, -1, 9);
 
     for (const stream of live.streams) stream.close();
     live.streams.clear();
diff --git a/packages/engine/src/interactive-ai-session.ts b/packages/engine/src/interactive-ai-session.ts
index f175309b76..890c5b78da 100644
--- a/packages/engine/src/interactive-ai-session.ts
+++ b/packages/engine/src/interactive-ai-session.ts
@@ -187,6 +187,40 @@ export function parseAgentResponse(text: string): PlanningResponse {
   throw new Error("AI returned an invalid response structure.");
 }
 
+/**
+ * CLI-agent planning one-shot seam (U9).
+ *
+ * Runs a CLI-agent one-shot in `planning` purpose and maps its output into the
+ * SAME `PlanningResponse` shape a model-backed planning run produces — so the
+ * downstream planning flow cannot tell a CLI-backed run from a model run. The
+ * one-shot runner is injected (`run`) so this is testable without a live PTY.
+ *
+ * NOTE (deviation, see report): the full planning *loop* (multi-turn
+ * question/answer over a resumable interactive session) is interactive, not
+ * one-shot — a one-shot planning run produces a single terminal response. This
+ * seam covers the single-shot "produce a plan" case and proves output-shape
+ * compatibility (`parseAgentResponse`). Wiring it into the resumable planning
+ * loop's executor resolution remains TODO when planning gains a CLI executor
+ * selector.
+ */
+export async function runCliAgentPlanning(
+  opts: Omit<
+    import("./cli-agent/one-shot-session.js").RunOneShotOptions,
+    "purpose"
+  >,
+  run: typeof import("./cli-agent/one-shot-session.js").runOneShotSession,
+): Promise<PlanningResponse> {
+  const result = await run({ ...opts, purpose: "planning" });
+  if (!result.ok) {
+    throw new Error(
+      `CLI-agent planning one-shot failed (${result.reason}): ${result.message}`,
+    );
+  }
+  // Map to the planning flow's shape exactly as a model run would: parse the
+  // adapter's textual result through the canonical planning parser.
+  return parseAgentResponse(result.text || result.rawOutput);
+}
+
 /** Extract text from the last assistant message (string | text blocks | thinking fallback). */
 function extractLastAssistantText(session: InteractiveAgentSession): string {
   const lastMessage = session.state.messages.filter((m) => m.role === "assistant").pop();
diff --git a/plugins/fusion-plugin-compound-engineering/src/__tests__/orchestrator-executor-seam.test.ts b/plugins/fusion-plugin-compound-engineering/src/__tests__/orchestrator-executor-seam.test.ts
new file mode 100644
index 0000000000..fe5c7b98f2
--- /dev/null
+++ b/plugins/fusion-plugin-compound-engineering/src/__tests__/orchestrator-executor-seam.test.ts
@@ -0,0 +1,40 @@
+import { afterEach, beforeEach, describe, expect, it, vi } from "vitest";
+import { CeOrchestrator, type CeSessionExecutor } from "../session/orchestrator.js";
+import { makeHarness, type TestHarness } from "./_harness.js";
+
+/**
+ * U9 CE executor seam contract.
+ *
+ * Proves the `executor` option threads end-to-end on a REAL orchestrator (not a
+ * scripted fake): the option set on deps is what `resolveExecutor()` returns,
+ * and it defaults to the model backend. The cli-agent one-shot wiring itself is
+ * engine-side (`@fusion/engine` runOneShotSession); this asserts the plugin
+ * carries the choice through, per the plugin-skills option-threading learning.
+ */
+let h: TestHarness;
+beforeEach(() => {
+  h = makeHarness();
+});
+afterEach(() => {
+  h.close();
+});
+
+function makeOrch(executor?: CeSessionExecutor) {
+  return new CeOrchestrator({
+    ctx: h.ctx,
+    createInteractiveAiSession: vi.fn(async () => ({ session: {} as never })),
+    projectRoot: h.projectRoot,
+    executor,
+  });
+}
+
+describe("CE executor seam (U9)", () => {
+  it("defaults to the model backend when no executor option is supplied", () => {
+    expect(makeOrch().resolveExecutor()).toEqual({ kind: "model" });
+  });
+
+  it("threads a cli-agent executor selection through deps → resolver", () => {
+    const orch = makeOrch({ kind: "cli-agent", adapterId: "claude-code" });
+    expect(orch.resolveExecutor()).toEqual({ kind: "cli-agent", adapterId: "claude-code" });
+  });
+});
diff --git a/plugins/fusion-plugin-compound-engineering/src/session/orchestrator.ts b/plugins/fusion-plugin-compound-engineering/src/session/orchestrator.ts
index 7f943cbd02..05040c17ee 100644
--- a/plugins/fusion-plugin-compound-engineering/src/session/orchestrator.ts
+++ b/plugins/fusion-plugin-compound-engineering/src/session/orchestrator.ts
@@ -85,6 +85,20 @@ export class CeTurnTimeoutError extends Error {
   }
 }
 
+/**
+ * Which session backend a CE stage runs on (U9 seam).
+ *
+ * - `model` (default): the model-backed interactive AI session (existing path).
+ * - `cli-agent`: a CLI agent adapter, run as a read-only one-shot per stage.
+ *
+ * The CE plugin threads this choice end-to-end (deps → resolver) per the
+ * plugin-skills option-threading learning; the cli-agent one-shot wiring itself
+ * lives engine-side in `@fusion/engine` (`runOneShotSession`).
+ */
+export type CeSessionExecutor =
+  | { kind: "model" }
+  | { kind: "cli-agent"; adapterId: string };
+
 export interface OrchestratorDeps {
   ctx: PluginContext;
   /**
@@ -96,6 +110,19 @@ export interface OrchestratorDeps {
   projectRoot?: string;
   /** Override the per-turn timeout (ms). */
   turnTimeoutMs?: number;
+  /**
+   * Session backend selector (U9). Defaults to `{ kind: "model" }`. When set to
+   * `{ kind: "cli-agent", adapterId }`, CE sessions select the CLI-agent
+   * one-shot executor. Threaded through to `resolveExecutor()` so callers can
+   * route a CE stage onto a CLI adapter.
+   *
+   * DEVIATION (see U9 report): the cli-agent branch of the *live* CE stage loop
+   * (replacing the interactive factory with one-shot turns inside
+   * `startStage`/`continueStage`) is not yet wired — only the option seam and
+   * its resolver contract land here. The engine-side one-shot runner is ready;
+   * the remaining work is invoking it from the stage loop.
+   */
+  executor?: CeSessionExecutor;
 }
 
 /**
@@ -176,6 +203,7 @@ export class CeOrchestrator {
   private readonly factory: CreateInteractiveAiSessionFactory | undefined;
   private readonly projectRoot: string;
   private readonly turnTimeoutMs: number;
+  private readonly executor: CeSessionExecutor;
   /** Live in-memory session handles keyed by ce_session id. */
   private readonly live = new Map<string, InteractiveAiSession>();
   /** Mid-turn working output per session (transient; flushed to history on settle). */
@@ -194,6 +222,17 @@ export class CeOrchestrator {
     this.factory = deps.createInteractiveAiSession ?? deps.ctx.createInteractiveAiSession;
     this.projectRoot = deps.projectRoot ?? deps.ctx.taskStore.getRootDir();
     this.turnTimeoutMs = deps.turnTimeoutMs ?? DEFAULT_TURN_TIMEOUT_MS;
+    this.executor = deps.executor ?? { kind: "model" };
+  }
+
+  /**
+   * Resolve the session backend for a CE stage (U9 seam). Threaded from
+   * `OrchestratorDeps.executor`; defaults to the model-backed interactive
+   * session. Exposed so the seam contract is directly assertable in tests and so
+   * future stage-loop wiring has a single resolution point.
+   */
+  resolveExecutor(): CeSessionExecutor {
+    return this.executor;
   }
 
   /**