diff --git a/packages/baoyu-codex-imagegen/src/main.ts b/packages/baoyu-codex-imagegen/src/main.ts
index ac66035..6827e11 100755
--- a/packages/baoyu-codex-imagegen/src/main.ts
+++ b/packages/baoyu-codex-imagegen/src/main.ts
@@ -6,7 +6,7 @@ import process from "node:process";
 import { setTimeout as delay } from "node:timers/promises";
 import { GenError, type CliOptions, type GenerateResult } from "./types.ts";
 import { runCodexExec } from "./spawn.ts";
-import { findCpToTarget, verifyImageGenWasInvoked, verifyOutput } from "./validator.ts";
+import { hasImageGenEvidence, verifyImageGenWasInvoked, verifyOutput } from "./validator.ts";
 import { cacheKey, lookupCache, storeCache, FileLock } from "./cache.ts";
 import { JsonLogger } from "./logger.ts";
 
@@ -125,7 +125,7 @@ function buildInstruction(prompt: string, opts: CliOptions): string {
   const refHint = opts.refImages.length > 0
     ? `\nREFERENCE IMAGES (attached above): ${opts.refImages.length} image(s) provided for style/composition guidance.\n`
     : "";
-  return `You have an internal tool called image_gen for image generation. Use it.
+  return `You have an internal tool called image_gen for image generation. You MUST call it before doing anything else.
 
 TASK: Generate an image with the spec below, then save to disk.
 
@@ -137,12 +137,15 @@ OUTPUT PATH: ${opts.outputPath}
 ${refHint}
 STEPS:
 1. Call image_gen with the prompt and aspect ratio above${opts.refImages.length > 0 ? " (using the attached reference images for guidance)" : ""}.
-2. Move or copy the resulting image from Codex default location ($CODEX_HOME/generated_images/...) to: ${opts.outputPath}
+2. Move or copy ONLY the image produced by that image_gen call from Codex default location ($CODEX_HOME/generated_images/...) to: ${opts.outputPath}
 3. Verify with: ls -la ${opts.outputPath}
 4. Reply with ONLY this JSON line (no markdown fences, no other text):
    {"status":"ok","path":"${opts.outputPath}","bytes":<file_size_in_bytes>}
 
 HARD CONSTRAINTS:
+- Do NOT search for, find, inspect, reuse, or copy any pre-existing files from $CODEX_HOME/generated_images/ or any other directory.
+- Do NOT run ls/find/rg/grep/glob over $CODEX_HOME/generated_images/ before image_gen has been called.
+- You MUST call image_gen first. Only after image_gen completes may you copy the newly created file from this turn.
 - Do NOT use curl, wget, Python, or any external API.
 - Do NOT use bash to fabricate an image; only image_gen produces real pixels.
 - Use ONLY the image_gen internal tool.`;
@@ -175,13 +178,16 @@ async function attemptGenerate(
     throw new GenError("agent_refused", "No thread id in event stream");
   }
 
-  // verify: image_gen was actually invoked (check $CODEX_HOME/generated_images/{threadId}/)
+  // verify image_gen ran in THIS thread. A PNG in this thread's
+  // generated_images dir is the real signal (image_gen does not surface as a
+  // stream item); the stream check is a forward-compatible fallback. The #185
+  // shortcut (copying an unrelated history image) yields neither.
   const ver = await verifyImageGenWasInvoked(run.threadId);
-  if (!ver.ok) {
-    // secondary verify: did tool_calls include cp/mv from generated_images to our target
-    if (!findCpToTarget(run.toolCalls, opts.outputPath)) {
-      throw new GenError("no_image_gen_tool_use", `image_gen was not invoked: ${ver.reason}`);
-    }
+  if (!hasImageGenEvidence(run.toolCalls, ver.ok)) {
+    throw new GenError(
+      "no_image_gen_tool_use",
+      `image_gen was not invoked (no image_gen event in stream; ${ver.reason})`,
+    );
   }
 
   // verify output
diff --git a/packages/baoyu-codex-imagegen/src/parser.test.ts b/packages/baoyu-codex-imagegen/src/parser.test.ts
index 2ce939f..1ce2996 100644
--- a/packages/baoyu-codex-imagegen/src/parser.test.ts
+++ b/packages/baoyu-codex-imagegen/src/parser.test.ts
@@ -33,17 +33,26 @@ test("parseEventStream tolerates malformed lines", () => {
   expect(r.usage?.input).toBe(1);
 });
 
-test("hasImageGenInvocation finds shell calls touching generated_images", () => {
+test("hasImageGenInvocation does not infer image_gen from shell copies", () => {
   const r = parseEventStream(REAL_PoC_STREAM);
-  // image_gen itself is not an event; inferred via generated_images cp path
-  // this test only verifies parser behavior; driver logic lives in validator
   const hasCp = r.toolCalls.some((tc) => tc.command?.includes("generated_images"));
   expect(hasCp).toBe(true);
+  expect(hasImageGenInvocation(r.toolCalls)).toBe(false);
 });
 
-test("hasImageGenInvocation (proper) returns false when no image_gen tool", () => {
+test("hasImageGenInvocation detects real image_gen tool calls only", () => {
   expect(hasImageGenInvocation([{ id: "1", tool: "shell", status: "completed" }])).toBe(false);
   expect(
     hasImageGenInvocation([{ id: "1", tool: "image_gen", status: "completed" }]),
   ).toBe(true);
 });
+
+test("parseEventStream normalizes an image_generation item to image_gen", () => {
+  const stream = `{"type":"thread.started","thread_id":"t1"}
+{"type":"item.started","item":{"id":"g0","type":"image_generation","status":"in_progress"}}
+{"type":"item.completed","item":{"id":"g0","type":"image_generation","status":"completed"}}
+{"type":"item.completed","item":{"id":"m0","type":"agent_message","text":"done"}}`;
+  const r = parseEventStream(stream);
+  expect(r.toolCalls.some((tc) => tc.tool === "image_gen")).toBe(true);
+  expect(hasImageGenInvocation(r.toolCalls)).toBe(true);
+});
diff --git a/packages/baoyu-codex-imagegen/src/validator.test.ts b/packages/baoyu-codex-imagegen/src/validator.test.ts
index 3e38656..8acd579 100644
--- a/packages/baoyu-codex-imagegen/src/validator.test.ts
+++ b/packages/baoyu-codex-imagegen/src/validator.test.ts
@@ -2,11 +2,52 @@ import { test, expect } from "bun:test";
 import { mkdtemp, writeFile, rm, mkdir } from "node:fs/promises";
 import { tmpdir } from "node:os";
 import path from "node:path";
-import { verifyOutput, verifyImageGenWasInvoked, findCpToTarget } from "./validator.ts";
+import { verifyOutput, verifyImageGenWasInvoked, hasImageGenEvidence } from "./validator.ts";
+import { parseEventStream } from "./parser.ts";
 import { GenError } from "./types.ts";
 
 const PNG_HEADER = Buffer.from([0x89, 0x50, 0x4e, 0x47, 0x0d, 0x0a, 0x1a, 0x0a]);
 
+// Condensed + sanitized capture of a REAL successful `codex exec --json` run
+// (thread 019edc1c…, 16:9 maple-tree image, single attempt). The image_gen
+// tool leaves NO stream item — success shows only reasoning / command_execution
+// / agent_message, and a `cp` from generated_images/<FULL-thread-id>/ig_*.png.
+const REAL_SUCCESS_STREAM = `{"type":"thread.started","thread_id":"019edc1c-e7a3-74f0-a276-13bea71d32d6"}
+{"type":"turn.started"}
+{"type":"item.completed","item":{"id":"r0","type":"reasoning"}}
+{"type":"item.completed","item":{"id":"r1","type":"reasoning"}}
+{"type":"item.completed","item":{"id":"m0","type":"agent_message","text":"Image generation is complete. Locating the newly produced image and copying it to the requested path."}}
+{"type":"item.started","item":{"id":"c0","type":"command_execution","command":"ls $CODEX_HOME/generated_images","status":"in_progress"}}
+{"type":"item.completed","item":{"id":"c0","type":"command_execution","command":"ls $CODEX_HOME/generated_images","exit_code":1,"status":"failed"}}
+{"type":"item.started","item":{"id":"c1","type":"command_execution","command":"cp $CODEX_HOME/generated_images/019edc1c-e7a3-74f0-a276-13bea71d32d6/ig_03eda661.png /Users/x/out/maple.png","status":"in_progress"}}
+{"type":"item.completed","item":{"id":"c1","type":"command_execution","command":"cp $CODEX_HOME/generated_images/019edc1c-e7a3-74f0-a276-13bea71d32d6/ig_03eda661.png /Users/x/out/maple.png","exit_code":0,"status":"completed"}}
+{"type":"item.completed","item":{"id":"m1","type":"agent_message","text":"{\\"status\\":\\"ok\\",\\"path\\":\\"/Users/x/out/maple.png\\",\\"bytes\\":1317377}"}}
+{"type":"turn.completed","usage":{"input_tokens":49489,"cached_input_tokens":34432,"output_tokens":2463,"reasoning_output_tokens":1990}}`;
+
+test("real success stream carries no image_gen item — gating on the stream alone would false-negative (#185)", () => {
+  const r = parseEventStream(REAL_SUCCESS_STREAM);
+  expect(r.threadId).toBe("019edc1c-e7a3-74f0-a276-13bea71d32d6");
+  // success path tools: reasoning / shell / agent_message — never image_gen
+  expect(r.toolCalls.map((tc) => tc.tool).sort()).toEqual([
+    "agent_message",
+    "agent_message",
+    "reasoning",
+    "reasoning",
+    "shell",
+    "shell",
+  ]);
+  expect(r.toolCalls.some((tc) => tc.tool === "image_gen")).toBe(false);
+  // filesystem evidence (PNG in this thread's dir) is what must let it through
+  expect(hasImageGenEvidence(r.toolCalls, true)).toBe(true);
+  // with no filesystem evidence and no stream item, it is rejected (the shortcut)
+  expect(hasImageGenEvidence(r.toolCalls, false)).toBe(false);
+});
+
+test("hasImageGenEvidence accepts a real image_gen stream item even without a dir PNG", () => {
+  expect(hasImageGenEvidence([{ id: "1", tool: "image_gen", status: "completed" }], false)).toBe(true);
+  expect(hasImageGenEvidence([{ id: "1", tool: "shell", status: "completed" }], false)).toBe(false);
+});
+
 test("verifyOutput passes for valid PNG", async () => {
   const dir = await mkdtemp(path.join(tmpdir(), "cig-val-"));
   try {
@@ -73,26 +114,3 @@ test("verifyImageGenWasInvoked true when PNG exists in thread dir", async () =>
     await rm(tempHome, { recursive: true, force: true });
   }
 });
-
-test("findCpToTarget detects cp from generated_images", () => {
-  expect(
-    findCpToTarget(
-      [
-        {
-          id: "1",
-          tool: "shell",
-          status: "completed",
-          command: "cp ~/.codex/generated_images/thread/ig_x.png /tmp/out.png",
-        },
-      ],
-      "/tmp/out.png",
-    ),
-  ).toBe(true);
-
-  expect(
-    findCpToTarget(
-      [{ id: "1", tool: "shell", status: "completed", command: "ls /tmp" }],
-      "/tmp/out.png",
-    ),
-  ).toBe(false);
-});
diff --git a/packages/baoyu-codex-imagegen/src/validator.ts b/packages/baoyu-codex-imagegen/src/validator.ts
index 487ad81..fe83752 100644
--- a/packages/baoyu-codex-imagegen/src/validator.ts
+++ b/packages/baoyu-codex-imagegen/src/validator.ts
@@ -3,6 +3,7 @@ import { homedir } from "node:os";
 import path from "node:path";
 import { GenError } from "./types.ts";
 import type { ToolCall } from "./types.ts";
+import { hasImageGenInvocation } from "./parser.ts";
 
 const PNG_MAGIC = Buffer.from([0x89, 0x50, 0x4e, 0x47, 0x0d, 0x0a, 0x1a, 0x0a]);
 
@@ -23,15 +24,15 @@ export async function verifyImageGenWasInvoked(threadId: string | null): Promise
   }
 }
 
-export function findCpToTarget(toolCalls: ToolCall[], target: string): boolean {
-  return toolCalls.some(
-    (tc) =>
-      tc.tool === "shell" &&
-      typeof tc.command === "string" &&
-      (tc.command.includes(target) || tc.command.includes(path.basename(target))) &&
-      /\b(cp|mv|cat)\b/.test(tc.command) &&
-      tc.command.includes("generated_images"),
-  );
+// Real evidence that image_gen ran in THIS thread. Codex's image_gen tool does
+// not surface as a stream item, so a successful run shows only reasoning/shell/
+// agent_message — `dirHasImage` (a PNG in this thread's generated_images dir) is
+// what proves it. The stream check is kept as a forward-compatible signal in
+// case a future Codex version emits the item. The #185 shortcut (copying an
+// unrelated history image, which lives under a different thread id) yields
+// neither, so it is correctly rejected.
+export function hasImageGenEvidence(toolCalls: ToolCall[], dirHasImage: boolean): boolean {
+  return dirHasImage || hasImageGenInvocation(toolCalls);
 }
 
 export async function verifyOutput(outputPath: string): Promise<{ bytes: number }> {
diff --git a/skills/baoyu-image-gen/scripts/codex-imagegen/main.ts b/skills/baoyu-image-gen/scripts/codex-imagegen/main.ts
index ac66035..6827e11 100755
--- a/skills/baoyu-image-gen/scripts/codex-imagegen/main.ts
+++ b/skills/baoyu-image-gen/scripts/codex-imagegen/main.ts
@@ -6,7 +6,7 @@ import process from "node:process";
 import { setTimeout as delay } from "node:timers/promises";
 import { GenError, type CliOptions, type GenerateResult } from "./types.ts";
 import { runCodexExec } from "./spawn.ts";
-import { findCpToTarget, verifyImageGenWasInvoked, verifyOutput } from "./validator.ts";
+import { hasImageGenEvidence, verifyImageGenWasInvoked, verifyOutput } from "./validator.ts";
 import { cacheKey, lookupCache, storeCache, FileLock } from "./cache.ts";
 import { JsonLogger } from "./logger.ts";
 
@@ -125,7 +125,7 @@ function buildInstruction(prompt: string, opts: CliOptions): string {
   const refHint = opts.refImages.length > 0
     ? `\nREFERENCE IMAGES (attached above): ${opts.refImages.length} image(s) provided for style/composition guidance.\n`
     : "";
-  return `You have an internal tool called image_gen for image generation. Use it.
+  return `You have an internal tool called image_gen for image generation. You MUST call it before doing anything else.
 
 TASK: Generate an image with the spec below, then save to disk.
 
@@ -137,12 +137,15 @@ OUTPUT PATH: ${opts.outputPath}
 ${refHint}
 STEPS:
 1. Call image_gen with the prompt and aspect ratio above${opts.refImages.length > 0 ? " (using the attached reference images for guidance)" : ""}.
-2. Move or copy the resulting image from Codex default location ($CODEX_HOME/generated_images/...) to: ${opts.outputPath}
+2. Move or copy ONLY the image produced by that image_gen call from Codex default location ($CODEX_HOME/generated_images/...) to: ${opts.outputPath}
 3. Verify with: ls -la ${opts.outputPath}
 4. Reply with ONLY this JSON line (no markdown fences, no other text):
    {"status":"ok","path":"${opts.outputPath}","bytes":<file_size_in_bytes>}
 
 HARD CONSTRAINTS:
+- Do NOT search for, find, inspect, reuse, or copy any pre-existing files from $CODEX_HOME/generated_images/ or any other directory.
+- Do NOT run ls/find/rg/grep/glob over $CODEX_HOME/generated_images/ before image_gen has been called.
+- You MUST call image_gen first. Only after image_gen completes may you copy the newly created file from this turn.
 - Do NOT use curl, wget, Python, or any external API.
 - Do NOT use bash to fabricate an image; only image_gen produces real pixels.
 - Use ONLY the image_gen internal tool.`;
@@ -175,13 +178,16 @@ async function attemptGenerate(
     throw new GenError("agent_refused", "No thread id in event stream");
   }
 
-  // verify: image_gen was actually invoked (check $CODEX_HOME/generated_images/{threadId}/)
+  // verify image_gen ran in THIS thread. A PNG in this thread's
+  // generated_images dir is the real signal (image_gen does not surface as a
+  // stream item); the stream check is a forward-compatible fallback. The #185
+  // shortcut (copying an unrelated history image) yields neither.
   const ver = await verifyImageGenWasInvoked(run.threadId);
-  if (!ver.ok) {
-    // secondary verify: did tool_calls include cp/mv from generated_images to our target
-    if (!findCpToTarget(run.toolCalls, opts.outputPath)) {
-      throw new GenError("no_image_gen_tool_use", `image_gen was not invoked: ${ver.reason}`);
-    }
+  if (!hasImageGenEvidence(run.toolCalls, ver.ok)) {
+    throw new GenError(
+      "no_image_gen_tool_use",
+      `image_gen was not invoked (no image_gen event in stream; ${ver.reason})`,
+    );
   }
 
   // verify output
diff --git a/skills/baoyu-image-gen/scripts/codex-imagegen/validator.ts b/skills/baoyu-image-gen/scripts/codex-imagegen/validator.ts
index 487ad81..fe83752 100644
--- a/skills/baoyu-image-gen/scripts/codex-imagegen/validator.ts
+++ b/skills/baoyu-image-gen/scripts/codex-imagegen/validator.ts
@@ -3,6 +3,7 @@ import { homedir } from "node:os";
 import path from "node:path";
 import { GenError } from "./types.ts";
 import type { ToolCall } from "./types.ts";
+import { hasImageGenInvocation } from "./parser.ts";
 
 const PNG_MAGIC = Buffer.from([0x89, 0x50, 0x4e, 0x47, 0x0d, 0x0a, 0x1a, 0x0a]);
 
@@ -23,15 +24,15 @@ export async function verifyImageGenWasInvoked(threadId: string | null): Promise
   }
 }
 
-export function findCpToTarget(toolCalls: ToolCall[], target: string): boolean {
-  return toolCalls.some(
-    (tc) =>
-      tc.tool === "shell" &&
-      typeof tc.command === "string" &&
-      (tc.command.includes(target) || tc.command.includes(path.basename(target))) &&
-      /\b(cp|mv|cat)\b/.test(tc.command) &&
-      tc.command.includes("generated_images"),
-  );
+// Real evidence that image_gen ran in THIS thread. Codex's image_gen tool does
+// not surface as a stream item, so a successful run shows only reasoning/shell/
+// agent_message — `dirHasImage` (a PNG in this thread's generated_images dir) is
+// what proves it. The stream check is kept as a forward-compatible signal in
+// case a future Codex version emits the item. The #185 shortcut (copying an
+// unrelated history image, which lives under a different thread id) yields
+// neither, so it is correctly rejected.
+export function hasImageGenEvidence(toolCalls: ToolCall[], dirHasImage: boolean): boolean {
+  return dirHasImage || hasImageGenInvocation(toolCalls);
 }
 
 export async function verifyOutput(outputPath: string): Promise<{ bytes: number }> {