diff --git a/src/agents/embedded-agent-runner/run/attempt-before-agent-run.ts b/src/agents/embedded-agent-runner/run/attempt-before-agent-run.ts
index 7967dd2eb7a4..9790b14a194f 100644
--- a/src/agents/embedded-agent-runner/run/attempt-before-agent-run.ts
+++ b/src/agents/embedded-agent-runner/run/attempt-before-agent-run.ts
@@ -5,7 +5,8 @@ import { resolveBlockMessage } from "../../../plugins/hook-decision-types.js";
 import type { getGlobalHookRunner } from "../../../plugins/hook-runner-global.js";
 import type { AgentMessage } from "../../runtime/index.js";
 import { log } from "../logger.js";
-import { cloneHookMessages, flushSessionManagerTranscript } from "./attempt-transcript-helpers.js";
+import { cloneHookMessages } from "./attempt-hook-messages.js";
+import { flushSessionManagerTranscript } from "./attempt-transcript-helpers.js";
 import { sessionMessagesContainIdempotencyKey } from "./pre-persisted-user-turn.js";
 import type { EmbeddedRunAttemptParams } from "./types.js";
 
diff --git a/src/agents/embedded-agent-runner/run/attempt-hook-messages.ts b/src/agents/embedded-agent-runner/run/attempt-hook-messages.ts
new file mode 100644
index 000000000000..494e4418ea03
--- /dev/null
+++ b/src/agents/embedded-agent-runner/run/attempt-hook-messages.ts
@@ -0,0 +1,6 @@
+import type { AgentMessage } from "../../runtime/index.js";
+
+/** Gives hooks an isolated message snapshot they cannot mutate in-session. */
+export function cloneHookMessages(messages: AgentMessage[]): AgentMessage[] {
+  return messages.map((message) => structuredClone(message));
+}
diff --git a/src/agents/embedded-agent-runner/run/attempt-prompt-observability.test.ts b/src/agents/embedded-agent-runner/run/attempt-prompt-observability.test.ts
new file mode 100644
index 000000000000..cd70bc7fe08d
--- /dev/null
+++ b/src/agents/embedded-agent-runner/run/attempt-prompt-observability.test.ts
@@ -0,0 +1,208 @@
+import { beforeEach, describe, expect, it, vi } from "vitest";
+import type { AgentMessage } from "../../runtime/index.js";
+
+const hoisted = vi.hoisted(() => ({
+  buildAgentHookContextChannelFields: vi.fn(() => ({ channel: "discord" })),
+  buildAgentHookContextIdentityFields: vi.fn(() => ({ senderId: "sender-1" })),
+  emitTrustedDiagnosticEvent: vi.fn(),
+  hasHooks: vi.fn(() => true),
+  log: {
+    debug: vi.fn(),
+    info: vi.fn(),
+    isEnabled: vi.fn(() => false),
+    warn: vi.fn(),
+  },
+  onExecutionPhase: vi.fn(),
+  recordStage: vi.fn(),
+  recordTrajectoryEvent: vi.fn(),
+  runLlmInput: vi.fn(
+    async (
+      _event: {
+        historyMessages?: unknown[];
+        imagesCount?: number;
+        prompt?: string;
+        tools?: unknown[];
+      },
+      _context: Record<string, unknown>,
+    ) => undefined,
+  ),
+  toTrajectoryToolDefinitions: vi.fn((tools: ReadonlyArray<{ name?: string }>) =>
+    tools.map((tool) => ({ name: tool.name })),
+  ),
+}));
+
+vi.mock("../../../infra/diagnostic-events.js", () => ({
+  emitTrustedDiagnosticEvent: hoisted.emitTrustedDiagnosticEvent,
+}));
+vi.mock("../../../plugins/hook-agent-context.js", () => ({
+  buildAgentHookContextChannelFields: hoisted.buildAgentHookContextChannelFields,
+  buildAgentHookContextIdentityFields: hoisted.buildAgentHookContextIdentityFields,
+}));
+vi.mock("../../../trajectory/runtime.js", () => ({
+  toTrajectoryToolDefinitions: hoisted.toTrajectoryToolDefinitions,
+}));
+vi.mock("../logger.js", () => ({ log: hoisted.log }));
+
+import { observeEmbeddedAttemptPrompt } from "./attempt-prompt-observability.js";
+
+type PromptObservabilityInput = Parameters<typeof observeEmbeddedAttemptPrompt>[0];
+
+function createInput(overrides: Partial<PromptObservabilityInput> = {}): PromptObservabilityInput {
+  const sessionMessages: AgentMessage[] = [
+    {
+      role: "user",
+      content: [{ type: "text", text: "history" }],
+      timestamp: 1,
+    },
+  ];
+  return {
+    attempt: {
+      messageChannel: "discord",
+      modelId: "model-1",
+      onExecutionPhase: hoisted.onExecutionPhase,
+      provider: "provider-1",
+      runId: "run-1",
+      senderId: "sender-1",
+      sessionFile: "/tmp/session.jsonl",
+      sessionId: "session-1",
+      sessionKey: "agent:main:discord:channel-1",
+      trigger: "user",
+      workspaceDir: "/tmp/workspace",
+    },
+    cacheTrace: { recordStage: hoisted.recordStage },
+    contextTokenBudget: 32_000,
+    diagnosticTrace: {
+      traceId: "1".repeat(32),
+      spanId: "2".repeat(16),
+    },
+    effectivePrompt: "effective prompt",
+    effectiveTools: [{ name: "visible-tool" }],
+    hookAgentId: "main",
+    hookMessagesForCurrentPrompt: sessionMessages,
+    hookRunner: {
+      hasHooks: hoisted.hasHooks,
+      runLlmInput: hoisted.runLlmInput,
+    },
+    imageCount: 2,
+    isRawModelRun: false,
+    llmBoundaryPromptForPrecheck: "[boundary] model prompt",
+    promptForModel: "model prompt",
+    promptSubmissionRuntimeOnly: false,
+    reserveTokens: 4_096,
+    runTrace: {
+      traceId: "1".repeat(32),
+      spanId: "3".repeat(16),
+    },
+    sessionMessages,
+    skipPromptSubmission: false,
+    streamStrategy: "provider-stream",
+    systemPromptForHook: "system prompt",
+    systemPromptText: "system prompt",
+    toolSearchCompacted: true,
+    tools: [{ name: "hook-tool" }],
+    trajectoryRecorder: { recordEvent: hoisted.recordTrajectoryEvent },
+    transcriptLeafId: "leaf-1",
+    transport: "sse",
+    uncompactedEffectiveTools: [{ name: "visible-tool" }, { name: "deferred-tool" }],
+    ...overrides,
+  } as PromptObservabilityInput;
+}
+
+describe("observeEmbeddedAttemptPrompt", () => {
+  beforeEach(() => {
+    vi.clearAllMocks();
+    hoisted.hasHooks.mockReturnValue(true);
+    hoisted.log.isEnabled.mockReturnValue(false);
+  });
+
+  it("records the assembled prompt boundary and dispatches a cloned llm_input snapshot", () => {
+    const input = createInput();
+
+    expect(observeEmbeddedAttemptPrompt(input)).toEqual({ skipPromptSubmission: false });
+
+    expect(hoisted.recordStage).toHaveBeenNthCalledWith(1, "prompt:before", {
+      prompt: "model prompt",
+      messages: input.sessionMessages,
+    });
+    expect(hoisted.recordStage).toHaveBeenNthCalledWith(2, "prompt:images", {
+      prompt: "model prompt",
+      messages: input.sessionMessages,
+      note: "images: prompt=2",
+    });
+    expect(hoisted.recordTrajectoryEvent).toHaveBeenCalledWith(
+      "context.compiled",
+      expect.objectContaining({
+        imagesCount: 2,
+        providerVisibleTools: [{ name: "visible-tool" }],
+        tools: [{ name: "visible-tool" }, { name: "deferred-tool" }],
+        transcriptLeafId: "leaf-1",
+      }),
+    );
+    expect(hoisted.emitTrustedDiagnosticEvent).toHaveBeenCalledWith(
+      expect.objectContaining({
+        type: "context.assembled",
+        contextTokenBudget: 32_000,
+        historyTextChars: 7,
+        messageCount: 1,
+        promptChars: 16,
+        reserveTokens: 4_096,
+      }),
+    );
+    expect(hoisted.onExecutionPhase).toHaveBeenCalledWith({
+      phase: "context_assembled",
+      provider: "provider-1",
+      model: "model-1",
+    });
+    expect(hoisted.runLlmInput).toHaveBeenCalledOnce();
+    const [event, context] = hoisted.runLlmInput.mock.calls[0] ?? [];
+    expect(event).toMatchObject({
+      prompt: "[boundary] model prompt",
+      imagesCount: 2,
+      tools: [{ name: "hook-tool" }],
+    });
+    expect(event?.historyMessages).toEqual(input.hookMessagesForCurrentPrompt);
+    expect(event?.historyMessages).not.toBe(input.hookMessagesForCurrentPrompt);
+    expect(context).toMatchObject({
+      agentId: "main",
+      channel: "discord",
+      senderId: "sender-1",
+    });
+  });
+
+  it("marks a blank current prompt as skipped while preserving its compiled trace", () => {
+    const input = createInput({
+      imageCount: 0,
+      llmBoundaryPromptForPrecheck: "   ",
+      promptForModel: "   ",
+    });
+
+    expect(observeEmbeddedAttemptPrompt(input)).toEqual({ skipPromptSubmission: true });
+
+    expect(hoisted.recordTrajectoryEvent).toHaveBeenNthCalledWith(
+      1,
+      "context.compiled",
+      expect.any(Object),
+    );
+    expect(hoisted.recordTrajectoryEvent).toHaveBeenNthCalledWith(2, "prompt.skipped", {
+      reason: "blank_user_prompt",
+      prompt: "   ",
+      messages: input.sessionMessages,
+      imagesCount: 0,
+    });
+    expect(hoisted.log.warn).toHaveBeenCalledWith(
+      expect.stringContaining("embedded run prompt skipped: blank user prompt"),
+    );
+    expect(hoisted.runLlmInput).not.toHaveBeenCalled();
+  });
+
+  it("keeps an already-blocked prompt out of cache, trajectory, and hook dispatch", () => {
+    const input = createInput({ skipPromptSubmission: true });
+
+    expect(observeEmbeddedAttemptPrompt(input)).toEqual({ skipPromptSubmission: true });
+
+    expect(hoisted.recordStage).not.toHaveBeenCalled();
+    expect(hoisted.recordTrajectoryEvent).not.toHaveBeenCalled();
+    expect(hoisted.runLlmInput).not.toHaveBeenCalled();
+    expect(hoisted.emitTrustedDiagnosticEvent).toHaveBeenCalledOnce();
+  });
+});
diff --git a/src/agents/embedded-agent-runner/run/attempt-prompt-observability.ts b/src/agents/embedded-agent-runner/run/attempt-prompt-observability.ts
new file mode 100644
index 000000000000..552d04ed12b5
--- /dev/null
+++ b/src/agents/embedded-agent-runner/run/attempt-prompt-observability.ts
@@ -0,0 +1,218 @@
+/** Records the fully assembled prompt boundary before preflight and submission. */
+import { emitTrustedDiagnosticEvent } from "../../../infra/diagnostic-events.js";
+import {
+  createChildDiagnosticTraceContext,
+  type DiagnosticTraceContext,
+  freezeDiagnosticTraceContext,
+} from "../../../infra/diagnostic-trace-context.js";
+import {
+  buildAgentHookContextChannelFields,
+  buildAgentHookContextIdentityFields,
+} from "../../../plugins/hook-agent-context.js";
+import type { PluginHookLlmInputEvent } from "../../../plugins/hook-types.js";
+import type { HookRunner } from "../../../plugins/hooks.js";
+import {
+  type createTrajectoryRuntimeRecorder,
+  toTrajectoryToolDefinitions,
+} from "../../../trajectory/runtime.js";
+import type { createCacheTrace } from "../../cache-trace.js";
+import type { AgentMessage } from "../../runtime/index.js";
+import type { AgentSession } from "../../sessions/index.js";
+import { log } from "../logger.js";
+import { summarizeSessionContext } from "./attempt-context-summary.js";
+import { cloneHookMessages } from "./attempt-hook-messages.js";
+import { resolvePromptSubmissionSkipReason } from "./attempt-prompt-skip.js";
+import type { EmbeddedRunAttemptParams } from "./types.js";
+
+type AttemptPromptObservabilityParams = Pick<
+  EmbeddedRunAttemptParams,
+  | "channelContext"
+  | "chatId"
+  | "currentChannelId"
+  | "messageChannel"
+  | "messageProvider"
+  | "messageTo"
+  | "modelId"
+  | "onExecutionPhase"
+  | "provider"
+  | "runId"
+  | "senderId"
+  | "sessionFile"
+  | "sessionId"
+  | "sessionKey"
+  | "trigger"
+  | "workspaceDir"
+>;
+type CacheTrace = Pick<NonNullable<ReturnType<typeof createCacheTrace>>, "recordStage"> | null;
+type PromptHookRunner = Pick<HookRunner, "hasHooks" | "runLlmInput"> | null;
+type TrajectoryRecorder = Pick<
+  NonNullable<ReturnType<typeof createTrajectoryRuntimeRecorder>>,
+  "recordEvent"
+> | null;
+type TrajectoryTool = Parameters<typeof toTrajectoryToolDefinitions>[0][number];
+
+export function observeEmbeddedAttemptPrompt(input: {
+  attempt: AttemptPromptObservabilityParams;
+  cacheTrace: CacheTrace;
+  contextTokenBudget: number;
+  diagnosticTrace: DiagnosticTraceContext;
+  effectivePrompt: string;
+  effectiveTools: readonly TrajectoryTool[];
+  hookAgentId: string;
+  hookMessagesForCurrentPrompt: AgentMessage[];
+  hookRunner: PromptHookRunner;
+  imageCount: number;
+  isRawModelRun: boolean;
+  llmBoundaryPromptForPrecheck: string;
+  promptForModel: string;
+  promptSubmissionRuntimeOnly?: boolean;
+  reserveTokens: number;
+  runTrace: DiagnosticTraceContext;
+  sessionMessages: AgentMessage[];
+  skipPromptSubmission: boolean;
+  streamStrategy: string;
+  systemPromptForHook: string;
+  systemPromptText?: string;
+  toolSearchCompacted: boolean;
+  tools: PluginHookLlmInputEvent["tools"];
+  trajectoryRecorder: TrajectoryRecorder;
+  transcriptLeafId: string | null;
+  transport: AgentSession["agent"]["transport"];
+  uncompactedEffectiveTools: readonly TrajectoryTool[];
+}): { skipPromptSubmission: boolean } {
+  const { attempt } = input;
+  let skipPromptSubmission = input.skipPromptSubmission;
+
+  if (!skipPromptSubmission) {
+    input.cacheTrace?.recordStage("prompt:before", {
+      prompt: input.promptForModel,
+      messages: input.sessionMessages,
+    });
+    input.cacheTrace?.recordStage("prompt:images", {
+      prompt: input.promptForModel,
+      messages: input.sessionMessages,
+      note: `images: prompt=${input.imageCount}`,
+    });
+    const providerVisibleTools = toTrajectoryToolDefinitions(input.effectiveTools);
+    input.trajectoryRecorder?.recordEvent("context.compiled", {
+      systemPrompt: input.systemPromptForHook,
+      prompt: input.promptForModel,
+      messages: input.sessionMessages,
+      tools: toTrajectoryToolDefinitions(
+        input.toolSearchCompacted ? input.uncompactedEffectiveTools : input.effectiveTools,
+      ),
+      ...(input.toolSearchCompacted ? { providerVisibleTools } : {}),
+      imagesCount: input.imageCount,
+      streamStrategy: input.streamStrategy,
+      transport: input.transport,
+      transcriptLeafId: input.transcriptLeafId,
+    });
+  }
+
+  const promptSkipReason = skipPromptSubmission
+    ? null
+    : resolvePromptSubmissionSkipReason({
+        prompt: input.promptForModel,
+        messages: input.sessionMessages,
+        runtimeOnly: input.promptSubmissionRuntimeOnly,
+        imageCount: input.imageCount,
+      });
+  if (promptSkipReason) {
+    skipPromptSubmission = true;
+    const skipContext =
+      `runId=${attempt.runId} sessionId=${attempt.sessionId} trigger=${attempt.trigger} ` +
+      `provider=${attempt.provider}/${attempt.modelId}`;
+    if (promptSkipReason === "blank_user_prompt") {
+      log.warn(`embedded run prompt skipped: blank user prompt ${skipContext}`);
+    } else {
+      log.info(`embedded run prompt skipped: empty prompt/history/images ${skipContext}`);
+    }
+    input.trajectoryRecorder?.recordEvent("prompt.skipped", {
+      reason: promptSkipReason,
+      prompt: input.promptForModel,
+      messages: input.sessionMessages,
+      imagesCount: input.imageCount,
+    });
+  }
+
+  const sessionSummary = summarizeSessionContext(input.sessionMessages);
+  emitTrustedDiagnosticEvent({
+    type: "context.assembled",
+    runId: attempt.runId,
+    ...(attempt.sessionKey && { sessionKey: attempt.sessionKey }),
+    ...(attempt.sessionId && { sessionId: attempt.sessionId }),
+    provider: attempt.provider,
+    model: attempt.modelId,
+    ...((attempt.messageChannel ?? attempt.messageProvider)
+      ? { channel: attempt.messageChannel ?? attempt.messageProvider }
+      : {}),
+    trigger: attempt.trigger,
+    messageCount: input.sessionMessages.length,
+    historyTextChars: sessionSummary.totalTextChars,
+    historyImageBlocks: sessionSummary.totalImageBlocks,
+    maxMessageTextChars: sessionSummary.maxMessageTextChars,
+    systemPromptChars: input.systemPromptText?.length ?? 0,
+    promptChars: input.effectivePrompt.length,
+    promptImages: input.imageCount,
+    contextTokenBudget: input.contextTokenBudget,
+    reserveTokens: input.reserveTokens,
+    trace: freezeDiagnosticTraceContext(createChildDiagnosticTraceContext(input.runTrace)),
+  });
+  attempt.onExecutionPhase?.({
+    phase: "context_assembled",
+    provider: attempt.provider,
+    model: attempt.modelId,
+  });
+
+  if (log.isEnabled("debug")) {
+    log.debug(
+      `[context-diag] pre-prompt: sessionKey=${attempt.sessionKey ?? attempt.sessionId} ` +
+        `messages=${input.sessionMessages.length} roleCounts=${sessionSummary.roleCounts} ` +
+        `historyTextChars=${sessionSummary.totalTextChars} ` +
+        `maxMessageTextChars=${sessionSummary.maxMessageTextChars} ` +
+        `historyImageBlocks=${sessionSummary.totalImageBlocks} ` +
+        `systemPromptChars=${input.systemPromptText?.length ?? 0} ` +
+        `promptChars=${input.effectivePrompt.length} ` +
+        `promptImages=${input.imageCount} ` +
+        `provider=${attempt.provider}/${attempt.modelId} sessionFile=${attempt.sessionFile}`,
+    );
+  }
+
+  if (!skipPromptSubmission && !input.isRawModelRun && input.hookRunner?.hasHooks("llm_input")) {
+    void input.hookRunner
+      .runLlmInput(
+        {
+          runId: attempt.runId,
+          sessionId: attempt.sessionId,
+          provider: attempt.provider,
+          model: attempt.modelId,
+          systemPrompt: input.systemPromptForHook,
+          prompt: input.llmBoundaryPromptForPrecheck,
+          historyMessages: cloneHookMessages(input.hookMessagesForCurrentPrompt),
+          imagesCount: input.imageCount,
+          tools: input.tools,
+        },
+        {
+          runId: attempt.runId,
+          trace: freezeDiagnosticTraceContext(input.diagnosticTrace),
+          agentId: input.hookAgentId,
+          sessionKey: attempt.sessionKey,
+          sessionId: attempt.sessionId,
+          workspaceDir: attempt.workspaceDir,
+          trigger: attempt.trigger,
+          ...buildAgentHookContextChannelFields(attempt),
+          ...buildAgentHookContextIdentityFields({
+            trigger: attempt.trigger,
+            senderId: attempt.senderId,
+            chatId: attempt.chatId,
+            channelContext: attempt.channelContext,
+          }),
+        },
+      )
+      .catch((err: unknown) => {
+        log.warn(`llm_input hook failed: ${String(err)}`);
+      });
+  }
+
+  return { skipPromptSubmission };
+}
diff --git a/src/agents/embedded-agent-runner/run/attempt-prompt-skip.ts b/src/agents/embedded-agent-runner/run/attempt-prompt-skip.ts
new file mode 100644
index 000000000000..4ee3a7ee9beb
--- /dev/null
+++ b/src/agents/embedded-agent-runner/run/attempt-prompt-skip.ts
@@ -0,0 +1,41 @@
+export type PromptSubmissionSkipReason = "blank_user_prompt" | "empty_prompt_history_images";
+
+/** Classifies prompt submissions that have no visible current-turn content. */
+export function resolvePromptSubmissionSkipReason(params: {
+  prompt: string;
+  messages: readonly unknown[];
+  imageCount: number;
+  runtimeOnly?: boolean;
+}): PromptSubmissionSkipReason | null {
+  if (params.prompt.trim().length > 0 || params.imageCount > 0) {
+    return null;
+  }
+  return params.messages.some(hasVisiblePromptHistory)
+    ? "blank_user_prompt"
+    : "empty_prompt_history_images";
+}
+
+function hasVisiblePromptHistory(message: unknown): boolean {
+  if (!message || typeof message !== "object") {
+    return false;
+  }
+  const record = message as { role?: unknown; content?: unknown };
+  if (record.role !== "user" && record.role !== "assistant") {
+    return false;
+  }
+  return hasNonEmptyContent(record.content);
+}
+
+function hasNonEmptyContent(content: unknown): boolean {
+  if (typeof content === "string") {
+    return content.trim().length > 0;
+  }
+  if (Array.isArray(content)) {
+    return content.some(hasNonEmptyContent);
+  }
+  if (!content || typeof content !== "object") {
+    return false;
+  }
+  const record = content as { text?: unknown; content?: unknown };
+  return hasNonEmptyContent(record.text) || hasNonEmptyContent(record.content);
+}
diff --git a/src/agents/embedded-agent-runner/run/attempt-transcript-helpers.ts b/src/agents/embedded-agent-runner/run/attempt-transcript-helpers.ts
index 228cb97d26fb..8bbc64d67221 100644
--- a/src/agents/embedded-agent-runner/run/attempt-transcript-helpers.ts
+++ b/src/agents/embedded-agent-runner/run/attempt-transcript-helpers.ts
@@ -21,10 +21,6 @@ import type { EmbeddedRunAttemptParams } from "./types.js";
 
 type AttemptSessionManager = ReturnType<typeof guardSessionManager>;
 
-export function cloneHookMessages(messages: AgentMessage[]): AgentMessage[] {
-  return messages.map((message) => structuredClone(message));
-}
-
 export function flushSessionManagerTranscript(sessionManager: AttemptSessionManager): void {
   (
     sessionManager as unknown as {
diff --git a/src/agents/embedded-agent-runner/run/attempt.prompt-helpers.test.ts b/src/agents/embedded-agent-runner/run/attempt.prompt-helpers.test.ts
index dfa61f5a177c..1c45f24453c8 100644
--- a/src/agents/embedded-agent-runner/run/attempt.prompt-helpers.test.ts
+++ b/src/agents/embedded-agent-runner/run/attempt.prompt-helpers.test.ts
@@ -36,10 +36,10 @@ vi.mock("../../music-generation-task-status.js", () => musicGenerationTaskStatus
 vi.mock("../../video-generation-task-status.js", () => videoGenerationTaskStatusMocks);
 vi.mock("../../../plugins/host-hook-state.js", () => hostHookStateMocks);
 
+import { resolvePromptSubmissionSkipReason } from "./attempt-prompt-skip.js";
 import {
   forgetPromptBuildDrainCacheForRun,
   mergeOrphanedTrailingUserPrompt,
-  resolvePromptSubmissionSkipReason,
   resolveAttemptMediaTaskSystemPromptAddition,
   resolvePromptBuildHookResult,
   shouldInjectHeartbeatPrompt,
diff --git a/src/agents/embedded-agent-runner/run/attempt.prompt-helpers.ts b/src/agents/embedded-agent-runner/run/attempt.prompt-helpers.ts
index 0200ff81beeb..7821d1559384 100644
--- a/src/agents/embedded-agent-runner/run/attempt.prompt-helpers.ts
+++ b/src/agents/embedded-agent-runner/run/attempt.prompt-helpers.ts
@@ -272,52 +272,6 @@ export function shouldWarnOnOrphanedUserRepair(
   return trigger === "user" || trigger === "manual";
 }
 
-type PromptSubmissionSkipReason = "blank_user_prompt" | "empty_prompt_history_images";
-
-/**
- * Distinguishes a truly empty prompt/history from a blank follow-up in a visible
- * conversation. This lets callers skip model submission while reporting the
- * reason accurately.
- */
-export function resolvePromptSubmissionSkipReason(params: {
-  prompt: string;
-  messages: readonly unknown[];
-  imageCount: number;
-  runtimeOnly?: boolean;
-}): PromptSubmissionSkipReason | null {
-  if (params.prompt.trim().length > 0 || params.imageCount > 0) {
-    return null;
-  }
-  return params.messages.some(hasVisiblePromptHistory)
-    ? "blank_user_prompt"
-    : "empty_prompt_history_images";
-}
-
-function hasVisiblePromptHistory(message: unknown): boolean {
-  if (!message || typeof message !== "object") {
-    return false;
-  }
-  const record = message as { role?: unknown; content?: unknown };
-  if (record.role !== "user" && record.role !== "assistant") {
-    return false;
-  }
-  return hasNonEmptyContent(record.content);
-}
-
-function hasNonEmptyContent(content: unknown): boolean {
-  if (typeof content === "string") {
-    return content.trim().length > 0;
-  }
-  if (Array.isArray(content)) {
-    return content.some(hasNonEmptyContent);
-  }
-  if (!content || typeof content !== "object") {
-    return false;
-  }
-  const record = content as { text?: unknown; content?: unknown };
-  return hasNonEmptyContent(record.text) || hasNonEmptyContent(record.content);
-}
-
 const QUEUED_USER_MESSAGE_MARKER =
   "[Queued user message from a previous active turn; preserved as context only. " +
   "Continue with the active prompt below.]";
diff --git a/src/agents/embedded-agent-runner/run/attempt.ts b/src/agents/embedded-agent-runner/run/attempt.ts
index 6f3d37f1b4d3..7bd00475fe2c 100644
--- a/src/agents/embedded-agent-runner/run/attempt.ts
+++ b/src/agents/embedded-agent-runner/run/attempt.ts
@@ -13,18 +13,8 @@ import {
   OPENCLAW_EMBEDDED_CONTEXT_ENGINE_HOST,
 } from "../../../context-engine/host-compat.js";
 import { resolveContextEngineOwnerPluginId } from "../../../context-engine/registry.js";
-import { emitTrustedDiagnosticEvent } from "../../../infra/diagnostic-events.js";
-import {
-  createChildDiagnosticTraceContext,
-  freezeDiagnosticTraceContext,
-} from "../../../infra/diagnostic-trace-context.js";
 import { formatErrorMessage } from "../../../infra/errors.js";
 import type { AssistantMessage } from "../../../llm/types.js";
-import {
-  buildAgentHookContextChannelFields,
-  buildAgentHookContextIdentityFields,
-} from "../../../plugins/hook-agent-context.js";
-import { toTrajectoryToolDefinitions } from "../../../trajectory/runtime.js";
 import { createBundleLspToolRuntime } from "../../agent-bundle-lsp-runtime.js";
 import { materializeBundleMcpToolsForRun } from "../../agent-bundle-mcp-tools.js";
 import { resolveAgentDir, resolveSessionAgentIds } from "../../agent-scope.js";
@@ -61,10 +51,10 @@ import { runEmbeddedAttemptBeforeAgentRun } from "./attempt-before-agent-run.js"
 import { prepareEmbeddedAttemptBootstrap } from "./attempt-bootstrap-prepare.js";
 import { prepareEmbeddedAttemptBundleTools } from "./attempt-bundle-tools.js";
 import { installEmbeddedAttemptContextGuards } from "./attempt-context-guards.js";
-import { summarizeSessionContext } from "./attempt-context-summary.js";
 import { prepareEmbeddedAttemptHistory } from "./attempt-history-prepare.js";
 import { prepareEmbeddedAttemptPromptAssembly } from "./attempt-prompt-assembly.js";
 import { prepareEmbeddedAttemptPromptContext } from "./attempt-prompt-context.js";
+import { observeEmbeddedAttemptPrompt } from "./attempt-prompt-observability.js";
 import {
   handleEmbeddedAttemptMidTurnPrecheck,
   prepareEmbeddedAttemptPromptPreflight,
@@ -92,11 +82,7 @@ import { prepareEmbeddedAttemptTimeout } from "./attempt-timeout-prepare.js";
 import { prepareEmbeddedAttemptToolBase } from "./attempt-tool-base-prepare.js";
 import { prepareEmbeddedAttemptToolCatalog } from "./attempt-tool-catalog.js";
 import { prepareEmbeddedAttemptTrajectory } from "./attempt-trajectory.js";
-import {
-  cloneHookMessages,
-  removeTrailingMidTurnPrecheckAssistantError,
-} from "./attempt-transcript-helpers.js";
-import { resolvePromptSubmissionSkipReason } from "./attempt.prompt-helpers.js";
+import { removeTrailingMidTurnPrecheckAssistantError } from "./attempt-transcript-helpers.js";
 import { resolveEmbeddedAttemptSessionWriteLockOptions } from "./attempt.run-decisions.js";
 import {
   acquireEmbeddedAttemptSessionFileOwner,
@@ -996,142 +982,36 @@ export async function runEmbeddedAttempt(
                     : undefined,
               });
 
-          if (!skipPromptSubmission) {
-            cacheTrace?.recordStage("prompt:before", {
-              prompt: promptForModel,
-              messages: activeSession.messages,
-            });
-            cacheTrace?.recordStage("prompt:images", {
-              prompt: promptForModel,
-              messages: activeSession.messages,
-              note: `images: prompt=${imageResult.images.length}`,
-            });
-            const trajectoryProviderVisibleTools = toTrajectoryToolDefinitions(effectiveTools);
-            trajectoryRecorder?.recordEvent("context.compiled", {
-              systemPrompt: systemPromptForHook,
-              prompt: promptForModel,
-              messages: activeSession.messages,
-              tools: toTrajectoryToolDefinitions(
-                toolSearch.compacted ? uncompactedEffectiveTools : effectiveTools,
-              ),
-              ...(toolSearch.compacted
-                ? { providerVisibleTools: trajectoryProviderVisibleTools }
-                : {}),
-              imagesCount: imageResult.images.length,
-              streamStrategy,
-              transport: effectiveAgentTransport,
-              transcriptLeafId,
-            });
-          }
-
-          const promptSkipReason = skipPromptSubmission
-            ? null
-            : resolvePromptSubmissionSkipReason({
-                prompt: promptForModel,
-                messages: activeSession.messages,
-                runtimeOnly: promptSubmission.runtimeOnly,
-                imageCount: imageResult.images.length,
-              });
-          if (promptSkipReason) {
-            skipPromptSubmission = true;
-            const skipContext =
-              `runId=${params.runId} sessionId=${params.sessionId} trigger=${params.trigger} ` +
-              `provider=${params.provider}/${params.modelId}`;
-            if (promptSkipReason === "blank_user_prompt") {
-              log.warn(`embedded run prompt skipped: blank user prompt ${skipContext}`);
-            } else {
-              log.info(`embedded run prompt skipped: empty prompt/history/images ${skipContext}`);
-            }
-            trajectoryRecorder?.recordEvent("prompt.skipped", {
-              reason: promptSkipReason,
-              prompt: promptForModel,
-              messages: activeSession.messages,
-              imagesCount: imageResult.images.length,
-            });
-          }
-
-          const msgCount = activeSession.messages.length;
-          const systemLen = systemPromptText?.length ?? 0;
-          const promptLen = effectivePrompt.length;
-          const sessionSummary = summarizeSessionContext(activeSession.messages);
           const reserveTokens = settingsManager.getCompactionReserveTokens();
-          emitTrustedDiagnosticEvent({
-            type: "context.assembled",
-            runId: params.runId,
-            ...(params.sessionKey && { sessionKey: params.sessionKey }),
-            ...(params.sessionId && { sessionId: params.sessionId }),
-            provider: params.provider,
-            model: params.modelId,
-            ...((params.messageChannel ?? params.messageProvider)
-              ? { channel: params.messageChannel ?? params.messageProvider }
-              : {}),
-            trigger: params.trigger,
-            messageCount: msgCount,
-            historyTextChars: sessionSummary.totalTextChars,
-            historyImageBlocks: sessionSummary.totalImageBlocks,
-            maxMessageTextChars: sessionSummary.maxMessageTextChars,
-            systemPromptChars: systemLen,
-            promptChars: promptLen,
-            promptImages: imageResult.images.length,
+          skipPromptSubmission = observeEmbeddedAttemptPrompt({
+            attempt: params,
+            cacheTrace,
             contextTokenBudget,
+            diagnosticTrace,
+            effectivePrompt,
+            effectiveTools,
+            hookAgentId,
+            hookMessagesForCurrentPrompt,
+            hookRunner,
+            imageCount: imageResult.images.length,
+            isRawModelRun,
+            llmBoundaryPromptForPrecheck,
+            promptForModel,
+            promptSubmissionRuntimeOnly: promptSubmission.runtimeOnly,
             reserveTokens,
-            trace: freezeDiagnosticTraceContext(createChildDiagnosticTraceContext(runTrace)),
-          });
-          params.onExecutionPhase?.({
-            phase: "context_assembled",
-            provider: params.provider,
-            model: params.modelId,
-          });
-
-          // Diagnostic: log context sizes before prompt to help debug early overflow errors.
-          if (log.isEnabled("debug")) {
-            log.debug(
-              `[context-diag] pre-prompt: sessionKey=${params.sessionKey ?? params.sessionId} ` +
-                `messages=${msgCount} roleCounts=${sessionSummary.roleCounts} ` +
-                `historyTextChars=${sessionSummary.totalTextChars} ` +
-                `maxMessageTextChars=${sessionSummary.maxMessageTextChars} ` +
-                `historyImageBlocks=${sessionSummary.totalImageBlocks} ` +
-                `systemPromptChars=${systemLen} promptChars=${promptLen} ` +
-                `promptImages=${imageResult.images.length} ` +
-                `provider=${params.provider}/${params.modelId} sessionFile=${params.sessionFile}`,
-            );
-          }
-
-          if (!skipPromptSubmission && !isRawModelRun && hookRunner?.hasHooks("llm_input")) {
-            hookRunner
-              .runLlmInput(
-                {
-                  runId: params.runId,
-                  sessionId: params.sessionId,
-                  provider: params.provider,
-                  model: params.modelId,
-                  systemPrompt: systemPromptForHook,
-                  prompt: llmBoundaryPromptForPrecheck,
-                  historyMessages: cloneHookMessages(hookMessagesForCurrentPrompt),
-                  imagesCount: imageResult.images.length,
-                  tools,
-                },
-                {
-                  runId: params.runId,
-                  trace: freezeDiagnosticTraceContext(diagnosticTrace),
-                  agentId: hookAgentId,
-                  sessionKey: params.sessionKey,
-                  sessionId: params.sessionId,
-                  workspaceDir: params.workspaceDir,
-                  trigger: params.trigger,
-                  ...buildAgentHookContextChannelFields(params),
-                  ...buildAgentHookContextIdentityFields({
-                    trigger: params.trigger,
-                    senderId: params.senderId,
-                    chatId: params.chatId,
-                    channelContext: params.channelContext,
-                  }),
-                },
-              )
-              .catch((err: unknown) => {
-                log.warn(`llm_input hook failed: ${String(err)}`);
-              });
-          }
+            runTrace,
+            sessionMessages: activeSession.messages,
+            skipPromptSubmission,
+            streamStrategy,
+            systemPromptForHook,
+            systemPromptText,
+            toolSearchCompacted: toolSearch.compacted,
+            tools,
+            trajectoryRecorder,
+            transcriptLeafId,
+            transport: effectiveAgentTransport,
+            uncompactedEffectiveTools,
+          }).skipPromptSubmission;
 
           const promptPreflight = await prepareEmbeddedAttemptPromptPreflight({
             attempt: params,