diff --git a/CHANGELOG.md b/CHANGELOG.md
index 58e2e26cf..bfd4a2491 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -28,6 +28,8 @@ parallel copies under `docs/` or `scripts/notes/`. At cut time: rename
   labels. Overlay rows bind by an ask id minted at emit, not render-order
   index. A stale or empty accept fail-closes as unavailable rather than
   impersonating Reject; Escape still denies.
+- After context compaction, ChatGPT Codex requests keep the operating prompt as
+  instructions.
 
 ## [0.3.18] - 2026-09-08
 
diff --git a/src/agent/director.ts b/src/agent/director.ts
index 5c2f21ee8..f5f2b4aae 100644
--- a/src/agent/director.ts
+++ b/src/agent/director.ts
@@ -526,6 +526,7 @@ class ChatDirectorImpl extends DefaultDirector {
         ...action.options,
         tools,
         retryPolicy: action.options?.retryPolicy ?? this.retryPolicy,
+        systemPrompt: action.options?.systemPrompt ?? this._systemPrompt,
       };
       if (this.inactivityTimeoutMs !== undefined)
         options.inactivityTimeoutMs = this.inactivityTimeoutMs;
diff --git a/src/director.test.ts b/src/director.test.ts
index 9ba4072e9..54557d18c 100644
--- a/src/director.test.ts
+++ b/src/director.test.ts
@@ -510,15 +510,15 @@ describe("chatDirector compaction", () => {
     } as unknown as ReactorInboundEvent;
   }
 
-  function chatDirectorWithContinuation(onContinuation?: () => void) {
-    return createChatDirector("", [], {
+  function chatDirectorWithContinuation(systemPrompt: string, onContinuation?: () => void) {
+    return createChatDirector(systemPrompt, [], {
       onTasksChange: () => {},
       requestContinuation: onContinuation ?? (() => {}),
     });
   }
 
   test("compacts at the tool.done pause once over threshold", async () => {
-    const director = chatDirectorWithContinuation();
+    const director = chatDirectorWithContinuation("Corbits operating prompt");
     await director.decide(overThresholdToolTurn(), longState, mockCapabilities);
     const actions = actionsArray(
       await director.decide(makeToolDoneEvent("t1"), longState, mockCapabilities),
@@ -535,6 +535,10 @@ describe("chatDirector compaction", () => {
       await director.decide(messageReceived(""), longState, mockCapabilities),
     );
     expect(resumed.some((a) => a.type === "infer")).toBe(true);
+    const infer = resumed.find((a) => a.type === "infer");
+    const options: ExtendedInferenceOptions | undefined =
+      infer?.type === "infer" ? infer.options : undefined;
+    expect(options?.systemPrompt).toBe("Corbits operating prompt");
   });
 
   // CL-6910: `timeout`/`retryable` are owned entirely by the harness's own
@@ -545,7 +549,7 @@ describe("chatDirector compaction", () => {
   // turn); it now falls through to the base director's terminal
   // checkpoint + reply instead of recovering.
   test("does not re-issue inference for a timeout already exhausted by the harness", async () => {
-    const director = chatDirectorWithContinuation();
+    const director = chatDirectorWithContinuation("");
     const timeout = {
       type: "inference.error",
       error: { category: "timeout", message: "request timed out" },
@@ -557,7 +561,7 @@ describe("chatDirector compaction", () => {
   });
 
   test("recovers an internally aborted inference but keeps explicit abort terminal", async () => {
-    const director = chatDirectorWithContinuation();
+    const director = chatDirectorWithContinuation("Corbits operating prompt");
     const internalAbort = {
       type: "inference.error",
       error: {
@@ -570,6 +574,10 @@ describe("chatDirector compaction", () => {
       await director.decide(internalAbort, longState, mockCapabilities),
     );
     expect(recovered.some((action) => action.type === "infer")).toBe(true);
+    const infer = recovered.find((action) => action.type === "infer");
+    const options: ExtendedInferenceOptions | undefined =
+      infer?.type === "infer" ? infer.options : undefined;
+    expect(options?.systemPrompt).toBe("Corbits operating prompt");
 
     const explicitAbort = {
       type: "abort",
@@ -581,7 +589,7 @@ describe("chatDirector compaction", () => {
   });
 
   test("does not auto-recover user-stop aborted inference errors", async () => {
-    const director = chatDirectorWithContinuation();
+    const director = chatDirectorWithContinuation("");
     const userStopAbort = {
       type: "inference.error",
       error: {
@@ -602,7 +610,10 @@ describe("chatDirector compaction", () => {
 
   test("a context_overflow inference error triggers compact-and-retry, not a terminal reply", async () => {
     let continuations = 0;
-    const director = chatDirectorWithContinuation(() => continuations++);
+    const director = chatDirectorWithContinuation(
+      "Corbits operating prompt",
+      () => continuations++,
+    );
     const actions = actionsArray(
       await director.decide(overflowError(), longState, mockCapabilities),
     );
@@ -615,10 +626,14 @@ describe("chatDirector compaction", () => {
       await director.decide(messageReceived(""), longState, mockCapabilities),
     );
     expect(resumed.some((a) => a.type === "infer")).toBe(true);
+    const infer = resumed.find((a) => a.type === "infer");
+    const options: ExtendedInferenceOptions | undefined =
+      infer?.type === "infer" ? infer.options : undefined;
+    expect(options?.systemPrompt).toBe("Corbits operating prompt");
   });
 
   test("overflow recovery is bounded so an incompressible history cannot loop forever", async () => {
-    const director = chatDirectorWithContinuation();
+    const director = chatDirectorWithContinuation("");
     for (let i = 0; i < 2; i++) {
       const actions = actionsArray(
         await director.decide(overflowError(), longState, mockCapabilities),
@@ -633,7 +648,7 @@ describe("chatDirector compaction", () => {
   });
 
   test("chat posture is preserved: an idle turn never terminates the session", async () => {
-    const director = chatDirectorWithContinuation();
+    const director = chatDirectorWithContinuation("");
     const idle = actionsArray(
       await director.decide(textInferenceDone(10), longState, mockCapabilities),
     );
@@ -1038,7 +1053,7 @@ describe("transient nudges", () => {
       source: "test",
     }) as unknown as ReactorInboundEvent;
 
-  test("open-task nudge uses ephemeralTurns, not systemPrompt", async () => {
+  test("open-task nudge uses ephemeralTurns and keeps the stable system prompt", async () => {
     const director = createChatDirector("stable-base", [], { onTasksChange: () => {} });
     await director.decide(manageTasksEvent("doing"), mockState, mockCapabilities);
     const actions = actionsArray(await director.decide(textTurn(), mockState, mockCapabilities));
@@ -1050,6 +1065,6 @@ describe("transient nudges", () => {
     expect(options?.ephemeralTurns?.length ?? 0).toBeGreaterThan(0);
     const nudgeText = options?.ephemeralTurns?.[0]?.content?.find((b) => b.type === "text");
     expect(nudgeText?.type === "text" ? nudgeText.text : "").toContain("tasks are still open");
-    expect(options?.systemPrompt).toBeUndefined();
+    expect(options?.systemPrompt).toBe("stable-base");
   });
 });
diff --git a/src/subagent/nudge-director.test.ts b/src/subagent/nudge-director.test.ts
index ef166e19d..f7963d8ea 100644
--- a/src/subagent/nudge-director.test.ts
+++ b/src/subagent/nudge-director.test.ts
@@ -194,6 +194,7 @@ describe("SubAgentDirector tool failure recovery", () => {
 
     const resumed = inferAction(await director.decide(messageReceived(""), longState, caps));
     const resumedTexts = ephemeralTexts(resumed);
+    expect(resumed.options?.systemPrompt).toBe("system");
     expect(resumedTexts).toHaveLength(1);
     expect(resumedTexts?.[0]).toContain("A tool call failed");
 
@@ -260,6 +261,7 @@ describe("SubAgentDirector tool failure recovery", () => {
 
     const resumed = inferAction(await director.decide(messageReceived(""), state, caps));
     const resumedTexts = ephemeralTexts(resumed);
+    expect(resumed.options?.systemPrompt).toBe("system");
     expect(resumedTexts).toHaveLength(1);
     expect(resumedTexts?.[0]).toContain("A tool call failed");
 
@@ -298,6 +300,7 @@ describe("SubAgentDirector tool failure recovery", () => {
     expect(continuations).toBe(1);
 
     const resumed = inferAction(await director.decide(messageReceived(""), state, caps));
+    expect(resumed.options?.systemPrompt).toBe("system");
     expect(ephemeralTexts(resumed)).toBeUndefined();
   });
 });
diff --git a/src/subagent/nudge-director.ts b/src/subagent/nudge-director.ts
index b9b9810cd..a0eabec19 100644
--- a/src/subagent/nudge-director.ts
+++ b/src/subagent/nudge-director.ts
@@ -86,6 +86,7 @@ function isNonEmptyParentMessage(event: ReactorInboundEvent): boolean {
 export class SubAgentDirector extends DefaultDirector {
   private readonly compaction: CompactionGovernor;
   private readonly retryPolicy: RetryPolicy;
+  private readonly _systemPrompt: string;
   /** When true (CritiqueDirector), empty readCounts is not a successful complete. */
   private readonly requireEvidence: boolean;
   private turnsCompleted = 0;
@@ -177,6 +178,7 @@ export class SubAgentDirector extends DefaultDirector {
     retryPolicy: RetryPolicy = createCorbitsRetryPolicy(),
   ) {
     super(systemPrompt, toolDefinitions, {});
+    this._systemPrompt = systemPrompt;
     this.compaction = createCompactionGovernor(requestContinuation, systemPrompt, toolDefinitions);
     this.stallTimeoutMs = stallTimeoutMs;
     this.now = now;
@@ -197,6 +199,7 @@ export class SubAgentDirector extends DefaultDirector {
         infer({
           ...(options ?? {}),
           retryPolicy: options?.retryPolicy ?? this.retryPolicy,
+          systemPrompt: options?.systemPrompt ?? this._systemPrompt,
         }),
     };
     // A real parent follow-up re-opens the brief; empty continuations do not.
diff --git a/tests/unit/codex-responses-adapter.test.ts b/tests/unit/codex-responses-adapter.test.ts
index 4faebfbcf..0f16c16c4 100644
--- a/tests/unit/codex-responses-adapter.test.ts
+++ b/tests/unit/codex-responses-adapter.test.ts
@@ -8,6 +8,7 @@ import {
   CODEX_RESPONSES_PROVIDER,
 } from "../../src/provider/codex-responses-adapter.js";
 import { GROK_RESPONSES_PROVIDER } from "../../src/provider/grok-responses-adapter.js";
+import { COMPACTED_PREFIX } from "../../src/session/compactor.js";
 import { BEARER_CREDENTIAL_SENTINEL } from "@intx/inference";
 import type { ConversationTurn, InferenceOptions, LastCycleSource } from "@intx/types/runtime";
 
@@ -87,6 +88,35 @@ describe("codex-responses buildRequest", () => {
     expect(body["tool_choice"]).toBe("auto");
   });
 
+  // Adapter mapping only: compacted history still uses instructions, not a
+  // developer item. ChatDirector tests own the lock that infer carries the
+  // constructor systemPrompt after compaction or recovery.
+  test("sends compacted history with the system prompt as instructions and no developer item", () => {
+    const systemPrompt = "Corbits operating prompt";
+    const turns: ConversationTurn[] = [
+      userTurn(`${COMPACTED_PREFIX}\nPrior work summarized.`),
+      { role: "assistant", timestamp: 0, content: [{ type: "text", text: "ok" }] },
+      userTurn("continue"),
+    ];
+    const body = JSON.parse(
+      adapter().buildRequest(turns, "gpt-5-codex", { ...baseOptions, systemPrompt }).body,
+    ) as Record<string, unknown>;
+    expect(body["instructions"]).toBe(systemPrompt);
+    const input = body["input"] as {
+      role?: string;
+      content?: { text?: string }[];
+    }[];
+    expect(input).toHaveLength(3);
+    expect(input[0]?.role).toBe("user");
+    expect(input[1]?.role).toBe("assistant");
+    expect(input[2]?.role).toBe("user");
+    expect(input[0]?.content?.[0]?.text?.startsWith(COMPACTED_PREFIX)).toBe(true);
+    expect(input.every((item) => item.role !== "developer")).toBe(true);
+    expect(input.some((item) => item.content?.some((block) => block.text === systemPrompt))).toBe(
+      false,
+    );
+  });
+
   test.each([undefined, "", "Corbits operating prompt"])(
     "preserves conversation order and system turns with systemPrompt %j",
     (systemPrompt) => {