diff --git a/src/agents/embedded-agent-runner/compact-reasons.ts b/src/agents/embedded-agent-runner/compact-reasons.ts
index 2ed42218aa84..da6486514d51 100644
--- a/src/agents/embedded-agent-runner/compact-reasons.ts
+++ b/src/agents/embedded-agent-runner/compact-reasons.ts
@@ -26,7 +26,7 @@ export function classifyCompactionReason(reason?: string): string {
   if (!text) {
     return "unknown";
   }
-  if (text.includes("nothing to compact")) {
+  if (text.includes("nothing to compact") || text.includes("no real conversation messages")) {
     return "no_compactable_entries";
   }
   // Backends use both phrases for the same harmless state: the transcript is
diff --git a/src/agents/embedded-agent-runner/compact.hooks.test.ts b/src/agents/embedded-agent-runner/compact.hooks.test.ts
index cc8cc5493717..746cc6e32171 100644
--- a/src/agents/embedded-agent-runner/compact.hooks.test.ts
+++ b/src/agents/embedded-agent-runner/compact.hooks.test.ts
@@ -2164,6 +2164,46 @@ describe("compactEmbeddedAgentSession hooks (ownsCompaction engine)", () => {
     expect(hookRunner.runAfterCompaction).not.toHaveBeenCalled();
   });
 
+  it("forces engine-owned compaction for preflight-required budget compaction", async () => {
+    const result = await compactEmbeddedAgentSession(
+      wrappedCompactionArgs({
+        trigger: "budget",
+        forcePreflight: true,
+        preflightRequired: true,
+        preflightCompactionTrigger: "transcript_bytes",
+      }),
+    );
+
+    expect(result.ok).toBe(true);
+    const compactArg = mockCallArg(contextEngineCompactMock) as {
+      runtimeContext?: Record<string, unknown>;
+    };
+    expectRecordFields(compactArg, {
+      compactionTarget: "budget",
+      force: true,
+    });
+    expectRecordFields(compactArg.runtimeContext, {
+      forceReason: "preflight_required",
+      preflightCompactionTrigger: "transcript_bytes",
+    });
+  });
+
+  it("continues forcing engine-owned manual compaction with manual force reason", async () => {
+    const result = await compactEmbeddedAgentSession(wrappedCompactionArgs({ trigger: "manual" }));
+
+    expect(result.ok).toBe(true);
+    const compactArg = mockCallArg(contextEngineCompactMock) as {
+      runtimeContext?: Record<string, unknown>;
+    };
+    expectRecordFields(compactArg, {
+      compactionTarget: "threshold",
+      force: true,
+    });
+    expectRecordFields(compactArg.runtimeContext, {
+      forceReason: "manual",
+    });
+  });
+
   it("threads the caller abort signal into the engine compact() call", async () => {
     const controller = new AbortController();
 
diff --git a/src/agents/embedded-agent-runner/compact.queued.ts b/src/agents/embedded-agent-runner/compact.queued.ts
index 025f5b8cffc3..467db144cb79 100644
--- a/src/agents/embedded-agent-runner/compact.queued.ts
+++ b/src/agents/embedded-agent-runner/compact.queued.ts
@@ -363,8 +363,21 @@ export async function compactEmbeddedAgentSession(
               currentTokenCount: params.currentTokenCount,
               compactionTarget: params.trigger === "manual" ? "threshold" : "budget",
               customInstructions: params.customInstructions,
-              force: params.trigger === "manual",
-              runtimeContext,
+              force:
+                params.force === true ||
+                params.forcePreflight === true ||
+                params.preflightRequired === true ||
+                params.trigger === "manual",
+              runtimeContext: {
+                ...runtimeContext,
+                forceReason:
+                  params.forcePreflight === true || params.preflightRequired === true
+                    ? "preflight_required"
+                    : params.trigger === "manual"
+                      ? "manual"
+                      : undefined,
+                preflightCompactionTrigger: params.preflightCompactionTrigger,
+              },
             },
             resolveCompactionTimeoutMs(params.config),
             params.abortSignal,
diff --git a/src/agents/embedded-agent-runner/compact.types.ts b/src/agents/embedded-agent-runner/compact.types.ts
index eb6df209b026..f161cd8ad908 100644
--- a/src/agents/embedded-agent-runner/compact.types.ts
+++ b/src/agents/embedded-agent-runner/compact.types.ts
@@ -66,6 +66,12 @@ export type CompactEmbeddedAgentSessionParams = {
   customInstructions?: string;
   tokenBudget?: number;
   force?: boolean;
+  /** Force compaction because the caller already determined this turn must compact before prompt submission. */
+  forcePreflight?: boolean;
+  /** Alias for forcePreflight used by preflight budget gates. */
+  preflightRequired?: boolean;
+  /** Diagnostic trigger that made preflight compaction mandatory. */
+  preflightCompactionTrigger?: "tokens" | "transcript_bytes";
   trigger?: "budget" | "overflow" | "manual";
   /**
    * Preflight callers can allow native/current-session harness compaction but
diff --git a/src/auto-reply/reply/agent-runner-direct-runtime-config.test.ts b/src/auto-reply/reply/agent-runner-direct-runtime-config.test.ts
index ad6b5e7af9fb..79c912bef881 100644
--- a/src/auto-reply/reply/agent-runner-direct-runtime-config.test.ts
+++ b/src/auto-reply/reply/agent-runner-direct-runtime-config.test.ts
@@ -306,6 +306,29 @@ describe("runReplyAgent runtime config", () => {
     expect(metadata?.deliverDespiteSourceReplySuppression).toBe(true);
   });
 
+  it("surfaces preflight compaction failures before the agent starts", async () => {
+    const { replyParams } = createDirectRuntimeReplyParams({
+      shouldFollowup: false,
+      isActive: false,
+    });
+    runPreflightCompactionIfNeededMock.mockRejectedValue(
+      new Error("Preflight compaction required but failed: auth profile mismatch"),
+    );
+    runMemoryFlushIfNeededMock.mockResolvedValue(undefined);
+
+    const result = await runReplyAgent(replyParams);
+
+    if (!result || Array.isArray(result)) {
+      throw new Error("expected a single preflight compaction failure reply payload");
+    }
+    expect(result.text).toContain("Context is too large");
+    expect(result.text).toContain("auto-compaction could not recover");
+    expect(result.text).toContain("/compact");
+    expect(result.text).toContain("/new");
+    const metadata = getReplyPayloadMetadata(result);
+    expect(metadata?.deliverDespiteSourceReplySuppression).toBe(true);
+  });
+
   it("does not resolve secrets before the enqueue-followup queue path", async () => {
     const { followupRun, resolvedQueue, replyParams } = createDirectRuntimeReplyParams({
       shouldFollowup: true,
diff --git a/src/auto-reply/reply/agent-runner-execution.ts b/src/auto-reply/reply/agent-runner-execution.ts
index 1f0290a88bb6..1735ff333037 100644
--- a/src/auto-reply/reply/agent-runner-execution.ts
+++ b/src/auto-reply/reply/agent-runner-execution.ts
@@ -625,6 +625,7 @@ function collapseRepeatedFailureDetail(message: string): string {
 const SAFE_MISSING_API_KEY_PROVIDERS = new Set(["anthropic", "google", "openai"]);
 const EXTERNAL_RUN_FAILURE_DETAIL_MAX_CHARS = 900;
 const AGENT_FAILED_BEFORE_REPLY_TEXT = "Agent failed before reply:";
+const PREFLIGHT_COMPACTION_FAILURE_PREFIX = "Preflight compaction required but failed:";
 
 type ExternalRunFailureReply = {
   text: string;
@@ -692,6 +693,27 @@ function buildCodexAppServerFailureText(message: string): string | null {
   return null;
 }
 
+export function buildPreflightCompactionFailureText(
+  message: string,
+  options?: { includeDetails?: boolean },
+): string | null {
+  const normalizedMessage = collapseRepeatedFailureDetail(message);
+  if (!normalizedMessage.startsWith(PREFLIGHT_COMPACTION_FAILURE_PREFIX)) {
+    return null;
+  }
+  const reason = sanitizeUserFacingText(
+    normalizedMessage.slice(PREFLIGHT_COMPACTION_FAILURE_PREFIX.length),
+    { errorContext: true },
+  )
+    .trim()
+    .replace(/\s+/gu, " ");
+  const reasonSuffix = options?.includeDetails && reason ? ` Reason: ${reason}.` : "";
+  return (
+    "⚠️ Context is too large and auto-compaction could not recover this turn." +
+    `${reasonSuffix} Try again, use /compact, or use /new to start a fresh session.`
+  );
+}
+
 function buildCliBackendTimeoutFailureText(message: string): string | null {
   const normalizedMessage = collapseRepeatedFailureDetail(message);
   const stall = normalizedMessage.match(CLI_BACKEND_NO_OUTPUT_STALL_RE);
@@ -820,6 +842,20 @@ export function buildKnownAgentRunFailureReplyPayload(params: {
     });
   }
 
+  const preflightCompactionFailureText = buildPreflightCompactionFailureText(message, {
+    includeDetails: isVerboseFailureDetailEnabled(params.resolvedVerboseLevel),
+  });
+  if (preflightCompactionFailureText) {
+    return markAgentRunFailureReplyPayload({
+      text: resolveExternalRunFailureTextForConversation({
+        text: preflightCompactionFailureText,
+        sessionCtx: params.sessionCtx,
+        isGenericRunnerFailure: false,
+        cfg: params.cfg,
+      }),
+    });
+  }
+
   const isPureTransientSummary = isFallbackSummary
     ? isPureTransientRateLimitSummary(params.err)
     : false;
diff --git a/src/auto-reply/reply/agent-runner-memory.test.ts b/src/auto-reply/reply/agent-runner-memory.test.ts
index f1794b422858..82c105c27a03 100644
--- a/src/auto-reply/reply/agent-runner-memory.test.ts
+++ b/src/auto-reply/reply/agent-runner-memory.test.ts
@@ -106,6 +106,10 @@ type CompactEmbeddedAgentSessionParams = {
   sandboxSessionKey?: string;
   currentTokenCount?: number;
   cwd?: string;
+  force?: boolean;
+  forcePreflight?: boolean;
+  preflightRequired?: boolean;
+  preflightCompactionTrigger?: string;
   sessionFile?: string;
   sessionId?: string;
   trigger?: string;
@@ -999,6 +1003,10 @@ describe("runMemoryFlushIfNeeded", () => {
     expect(compactEmbeddedAgentSessionMock).toHaveBeenCalledTimes(1);
     expect(requireCompactEmbeddedAgentSessionCall()).toMatchObject({
       trigger: "budget",
+      force: true,
+      forcePreflight: true,
+      preflightRequired: true,
+      preflightCompactionTrigger: "tokens",
       deferOwningContextEngineCompaction: false,
       contextTokenBudget: 100,
     });
@@ -1112,7 +1120,7 @@ describe("runMemoryFlushIfNeeded", () => {
     ["stale_thread_binding", "thread not found: <codex-thread-id>"],
     ["missing_thread_binding", "no thread binding for session"],
   ])(
-    "continues after recoverable native harness %s failure during preflight compaction",
+    "fails required preflight compaction after native harness %s failure",
     async (failureReason, reason) => {
       const sessionFile = path.join(rootDir, "session.jsonl");
       await fs.writeFile(
@@ -1143,30 +1151,31 @@ describe("runMemoryFlushIfNeeded", () => {
       };
       const sessionStore = { "agent:main:telegram:group:redacted": sessionEntry };
 
-      const entry = await runPreflightCompactionIfNeeded({
-        cfg: { agents: { defaults: { compaction: { memoryFlush: {} } } } },
-        followupRun: createTestFollowupRun({
-          sessionId: "session",
-          sessionFile,
+      await expect(
+        runPreflightCompactionIfNeeded({
+          cfg: { agents: { defaults: { compaction: { memoryFlush: {} } } } },
+          followupRun: createTestFollowupRun({
+            sessionId: "session",
+            sessionFile,
+            sessionKey: "agent:main:telegram:group:redacted",
+          }),
+          defaultModel: "anthropic/claude-opus-4-6",
+          agentCfgContextTokens: 100,
+          sessionEntry,
+          sessionStore,
           sessionKey: "agent:main:telegram:group:redacted",
+          storePath: path.join(rootDir, "sessions.json"),
+          isHeartbeat: false,
+          replyOperation: createReplyOperation(),
         }),
-        defaultModel: "anthropic/claude-opus-4-6",
-        agentCfgContextTokens: 100,
-        sessionEntry,
-        sessionStore,
-        sessionKey: "agent:main:telegram:group:redacted",
-        storePath: path.join(rootDir, "sessions.json"),
-        isHeartbeat: false,
-        replyOperation: createReplyOperation(),
-      });
+      ).rejects.toThrow(`Preflight compaction required but failed: ${reason}`);
 
-      expect(entry).toBe(sessionEntry);
       expect(compactEmbeddedAgentSessionMock).toHaveBeenCalledTimes(1);
       expect(incrementCompactionCountMock).not.toHaveBeenCalled();
     },
   );
 
-  it("continues after an unstructured thread-not-found preflight compaction failure", async () => {
+  it("fails required preflight compaction after an unstructured thread-not-found failure", async () => {
     const sessionFile = path.join(rootDir, "session.jsonl");
     await fs.writeFile(
       sessionFile,
@@ -1195,24 +1204,27 @@ describe("runMemoryFlushIfNeeded", () => {
     };
     const sessionStore = { "agent:main:telegram:group:redacted": sessionEntry };
 
-    const entry = await runPreflightCompactionIfNeeded({
-      cfg: { agents: { defaults: { compaction: { memoryFlush: {} } } } },
-      followupRun: createTestFollowupRun({
-        sessionId: "session",
-        sessionFile,
+    await expect(
+      runPreflightCompactionIfNeeded({
+        cfg: { agents: { defaults: { compaction: { memoryFlush: {} } } } },
+        followupRun: createTestFollowupRun({
+          sessionId: "session",
+          sessionFile,
+          sessionKey: "agent:main:telegram:group:redacted",
+        }),
+        defaultModel: "anthropic/claude-opus-4-6",
+        agentCfgContextTokens: 100,
+        sessionEntry,
+        sessionStore,
         sessionKey: "agent:main:telegram:group:redacted",
+        storePath: path.join(rootDir, "sessions.json"),
+        isHeartbeat: false,
+        replyOperation: createReplyOperation(),
       }),
-      defaultModel: "anthropic/claude-opus-4-6",
-      agentCfgContextTokens: 100,
-      sessionEntry,
-      sessionStore,
-      sessionKey: "agent:main:telegram:group:redacted",
-      storePath: path.join(rootDir, "sessions.json"),
-      isHeartbeat: false,
-      replyOperation: createReplyOperation(),
-    });
+    ).rejects.toThrow(
+      "Preflight compaction required but failed: thread not found: <codex-thread-id>",
+    );
 
-    expect(entry).toBe(sessionEntry);
     expect(compactEmbeddedAgentSessionMock).toHaveBeenCalledTimes(1);
     expect(incrementCompactionCountMock).not.toHaveBeenCalled();
   });
@@ -1469,7 +1481,7 @@ describe("runMemoryFlushIfNeeded", () => {
     expect(runEmbeddedAgentMock).toHaveBeenCalledTimes(1);
   });
 
-  it("continues when preflight compaction returns a successful no-op", async () => {
+  it("fails when required preflight compaction returns an unknown successful no-op", async () => {
     compactEmbeddedAgentSessionMock.mockResolvedValueOnce({
       ok: true,
       compacted: false,
@@ -1485,23 +1497,24 @@ describe("runMemoryFlushIfNeeded", () => {
     const sessionStore = { main: sessionEntry };
     const replyOperation = createReplyOperation();
 
-    const entry = await runPreflightCompactionIfNeeded({
-      cfg: { agents: { defaults: { compaction: { memoryFlush: {} } } } },
-      followupRun: createTestFollowupRun({
-        sessionId: "session",
+    await expect(
+      runPreflightCompactionIfNeeded({
+        cfg: { agents: { defaults: { compaction: { memoryFlush: {} } } } },
+        followupRun: createTestFollowupRun({
+          sessionId: "session",
+          sessionKey: "main",
+        }),
+        defaultModel: "anthropic/claude-opus-4-6",
+        agentCfgContextTokens: 200_000,
+        sessionEntry,
+        sessionStore,
         sessionKey: "main",
+        storePath: path.join(rootDir, "sessions.json"),
+        isHeartbeat: false,
+        replyOperation,
       }),
-      defaultModel: "anthropic/claude-opus-4-6",
-      agentCfgContextTokens: 200_000,
-      sessionEntry,
-      sessionStore,
-      sessionKey: "main",
-      storePath: path.join(rootDir, "sessions.json"),
-      isHeartbeat: false,
-      replyOperation,
-    });
+    ).rejects.toThrow("Preflight compaction required but failed: plugin already stored this turn");
 
-    expect(entry).toBe(sessionEntry);
     expect(compactEmbeddedAgentSessionMock).toHaveBeenCalledTimes(1);
     const compactCall = requireCompactEmbeddedAgentSessionCall();
     expect(compactCall.contextTokenBudget).toBe(200_000);
diff --git a/src/auto-reply/reply/agent-runner-memory.ts b/src/auto-reply/reply/agent-runner-memory.ts
index a04b783e8a07..f9dfd4c146d7 100644
--- a/src/auto-reply/reply/agent-runner-memory.ts
+++ b/src/auto-reply/reply/agent-runner-memory.ts
@@ -7,11 +7,7 @@ import {
 } from "@openclaw/normalization-core/string-coerce";
 import { resolveBootstrapWarningSignaturesSeen } from "../../agents/bootstrap-budget.js";
 import { estimateMessagesTokens } from "../../agents/compaction.js";
-import {
-  classifyCompactionReason,
-  DEFERRED_CONTEXT_ENGINE_COMPACTION_REASON,
-} from "../../agents/embedded-agent-runner/compact-reasons.js";
-import { isRecoverableNativeHarnessBindingFailure } from "../../agents/harness/compaction-recovery.js";
+import { classifyCompactionReason } from "../../agents/embedded-agent-runner/compact-reasons.js";
 import { resolveAgentHarnessPolicy } from "../../agents/harness/policy.js";
 import { ensureSelectedAgentHarnessPlugin } from "../../agents/harness/runtime-plugin.js";
 import { runWithModelFallback } from "../../agents/model-fallback.js";
@@ -189,10 +185,6 @@ function isPreflightCompactionSkipReason(reason?: string): boolean {
   );
 }
 
-function isDeferredPreflightCompactionReason(reason?: string): boolean {
-  return normalizeOptionalString(reason) === DEFERRED_CONTEXT_ENGINE_COMPACTION_REASON;
-}
-
 function resolveMemoryFlushModelFallbackOptions(
   run: FollowupRun["run"],
   model?: string,
@@ -893,6 +885,10 @@ export async function runPreflightCompactionIfNeeded(params: {
     thinkLevel: params.followupRun.run.thinkLevel,
     bashElevated: params.followupRun.run.bashElevated,
     trigger: "budget",
+    force: true,
+    forcePreflight: true,
+    preflightRequired: true,
+    preflightCompactionTrigger: compactionTrigger,
     deferOwningContextEngineCompaction: false,
     contextTokenBudget: contextWindowTokens,
     currentTokenCount: tokenCountForCompaction ?? freshPersistedTokens,
@@ -907,25 +903,17 @@ export async function runPreflightCompactionIfNeeded(params: {
       return entry ?? params.sessionEntry;
     }
     logVerbose(`preflightCompaction failed: sessionKey=${params.sessionKey} reason=${reason}`);
-    if (isRecoverableNativeHarnessBindingFailure(result)) {
-      logVerbose(
-        `preflightCompaction continuing after recoverable native harness binding failure: sessionKey=${params.sessionKey} reason=${reason}`,
-      );
-      return entry ?? params.sessionEntry;
-    }
     throw new Error(`Preflight compaction required but failed: ${reason}`);
   }
 
   if (!result.compacted) {
-    const reason = normalizeOptionalString(result.reason);
-    if (isDeferredPreflightCompactionReason(reason)) {
-      logVerbose(`preflightCompaction failed: sessionKey=${params.sessionKey} reason=${reason}`);
-      throw new Error(`Preflight compaction required but failed: ${reason}`);
+    const reason = normalizeOptionalString(result.reason) ?? "not_compacted";
+    if (isPreflightCompactionSkipReason(reason)) {
+      logVerbose(`preflightCompaction skipped: sessionKey=${params.sessionKey} reason=${reason}`);
+      return entry ?? params.sessionEntry;
     }
-    logVerbose(
-      `preflightCompaction skipped: sessionKey=${params.sessionKey} reason=${reason ?? "not_compacted"}`,
-    );
-    return entry ?? params.sessionEntry;
+    logVerbose(`preflightCompaction failed: sessionKey=${params.sessionKey} reason=${reason}`);
+    throw new Error(`Preflight compaction required but failed: ${reason}`);
   }
 
   await deps.incrementCompactionCount({
diff --git a/src/auto-reply/reply/followup-runner.test.ts b/src/auto-reply/reply/followup-runner.test.ts
index 19eac81eb462..7fddff99c539 100644
--- a/src/auto-reply/reply/followup-runner.test.ts
+++ b/src/auto-reply/reply/followup-runner.test.ts
@@ -744,6 +744,77 @@ describe("createFollowupRunner reply-lane admission", () => {
     );
     realAgentEvents.resetAgentRunContextForTest();
   });
+
+  it("routes preflight compaction failures before starting queued followup runs", async () => {
+    runPreflightCompactionIfNeededMock.mockRejectedValueOnce(
+      new Error("Preflight compaction required but failed: auth profile mismatch"),
+    );
+    const runner = createFollowupRunner({
+      typing: createMockTypingController(),
+      typingMode: "instant",
+      sessionKey: "main",
+      defaultModel: "anthropic/claude",
+    });
+
+    await runner(
+      createQueuedRun({
+        originatingChannel: "discord",
+        originatingTo: "channel:C1",
+        originatingAccountId: "acct-1",
+        originatingThreadId: "thread-1",
+        originatingChatType: "group",
+        run: {
+          messageProvider: "discord",
+          provider: "anthropic",
+          model: "claude",
+          verboseLevel: "off",
+          sessionKey: "main",
+        },
+      }),
+    );
+
+    expect(runEmbeddedAgentMock).not.toHaveBeenCalled();
+    expect(routeReplyMock).toHaveBeenCalledOnce();
+    expect(routeReplyMock).toHaveBeenCalledWith(
+      expect.objectContaining({
+        channel: "discord",
+        to: "channel:C1",
+        accountId: "acct-1",
+        threadId: "thread-1",
+        payload: expect.objectContaining({
+          text: expect.stringContaining("auto-compaction could not recover"),
+        }),
+      }),
+    );
+  });
+
+  it("preserves non-compaction preflight failures for queued followup runs", async () => {
+    runPreflightCompactionIfNeededMock.mockRejectedValueOnce(new Error("session load failed"));
+    const runner = createFollowupRunner({
+      typing: createMockTypingController(),
+      typingMode: "instant",
+      sessionKey: "main",
+      defaultModel: "anthropic/claude",
+    });
+
+    await expect(
+      runner(
+        createQueuedRun({
+          originatingChannel: "discord",
+          originatingTo: "channel:C1",
+          run: {
+            messageProvider: "discord",
+            provider: "anthropic",
+            model: "claude",
+            sessionKey: "main",
+          },
+        }),
+      ),
+    ).rejects.toThrow("session load failed");
+
+    expect(runEmbeddedAgentMock).not.toHaveBeenCalled();
+    expect(routeReplyMock).not.toHaveBeenCalled();
+  });
 });
 
 async function normalizeComparablePath(filePath: string): Promise<string> {
diff --git a/src/auto-reply/reply/followup-runner.ts b/src/auto-reply/reply/followup-runner.ts
index 1d527bcd66c4..e6197d160054 100644
--- a/src/auto-reply/reply/followup-runner.ts
+++ b/src/auto-reply/reply/followup-runner.ts
@@ -28,6 +28,7 @@ import { formatErrorMessage } from "../../infra/errors.js";
 import { defaultRuntime } from "../../runtime.js";
 import { shouldPreserveUserFacingSessionStateForInputProvenance } from "../../sessions/input-provenance.js";
 import { isInternalMessageChannel } from "../../utils/message-channel.js";
+import { markReplyPayloadForSourceSuppressionDelivery } from "../reply-payload.js";
 import type { GetReplyOptions, ReplyPayload } from "../types.js";
 import {
   clearDroppedCliSessionBinding,
@@ -35,6 +36,7 @@ import {
   runCliAgentWithLifecycle,
 } from "./agent-runner-cli-dispatch.js";
 import {
+  buildPreflightCompactionFailureText,
   resolveRunAfterAutoFallbackPrimaryProbeRecheck,
   resolveSessionRuntimeOverrideForProvider,
 } from "./agent-runner-execution.js";
@@ -546,19 +548,40 @@ export function createFollowupRunner(params: {
       let runResult: Awaited<ReturnType<typeof runEmbeddedAgent>>;
       let fallbackProvider = run.provider;
       let fallbackModel = run.model;
-      activeSessionEntry = await runPreflightCompactionIfNeeded({
-        cfg: runtimeConfig,
-        followupRun: effectiveQueued,
-        promptForEstimate: queued.prompt,
-        defaultModel,
-        agentCfgContextTokens,
-        sessionEntry: activeSessionEntry,
-        sessionStore,
-        sessionKey: replySessionKey,
-        storePath,
-        isHeartbeat: opts?.isHeartbeat === true,
-        replyOperation,
-      });
+      try {
+        activeSessionEntry = await runPreflightCompactionIfNeeded({
+          cfg: runtimeConfig,
+          followupRun: effectiveQueued,
+          promptForEstimate: queued.prompt,
+          defaultModel,
+          agentCfgContextTokens,
+          sessionEntry: activeSessionEntry,
+          sessionStore,
+          sessionKey: replySessionKey,
+          storePath,
+          isHeartbeat: opts?.isHeartbeat === true,
+          replyOperation,
+        });
+      } catch (err) {
+        const message = formatErrorMessage(err);
+        replyOperation.fail("run_failed", err);
+        const preflightCompactionFailureText = buildPreflightCompactionFailureText(message, {
+          includeDetails: run.verboseLevel === "on" || run.verboseLevel === "full",
+        });
+        if (preflightCompactionFailureText) {
+          await sendFollowupPayloads(
+            [
+              markReplyPayloadForSourceSuppressionDelivery({
+                text: preflightCompactionFailureText,
+              }),
+            ],
+            effectiveQueued,
+            { provider: fallbackProvider, modelId: fallbackModel },
+          );
+          return;
+        }
+        throw err;
+      }
       if (run.sessionKey) {
         const owningSessionId =
           activeSessionEntry?.sessionId === run.sessionId