Keep inline prompts out of the action helper argv

action.yml

@@ -366,8 +366,9 @@ runs:
       shell: bash
       run: |
         exec env -u NODE_OPTIONS NODE_OPTIONS=--disable-sigusr1 node --disable-sigusr1 "$ACTION_PATH/dist/main.js" run-codex-exec \
-            --prompt "${CODEX_PROMPT}" \
+            --prompt "" \
             --prompt-file "${CODEX_PROMPT_FILE}" \
+            --prompt-environment-variable "${CODEX_PROMPT:+CODEX_PROMPT}" \
             --output-file "$CODEX_OUTPUT_FILE" \
             --codex-home "$CODEX_HOME" \
             --cd "$CODEX_WORKING_DIRECTORY" \

src/main.ts

@@ -131,6 +131,11 @@ export async function main() {
       "--prompt-file <FILE>",
       "File containing the prompt to pass to `codex exec`."
     )
+    .option(
+      "--prompt-environment-variable <NAME>",
+      "Environment variable containing the prompt to pass to `codex exec`.",
+      ""
+    )
     .requiredOption(
       "--codex-home <DIRECTORY>",
       "Path to the Codex CLI home directory (where config files are stored)."
@@ -176,6 +181,7 @@ export async function main() {
       async (options: {
         prompt: string;
         promptFile: string;
+        promptEnvironmentVariable: string;
         codexHome: string;
         cd: string;
         extraArgs: Array<string>;
@@ -192,6 +198,7 @@ export async function main() {
         const {
           prompt,
           promptFile,
+          promptEnvironmentVariable,
           outputFile,
           codexHome,
           cd,
@@ -208,21 +215,35 @@ export async function main() {
 
         const normalizedPrompt = emptyAsNull(prompt);
         const normalizedPromptFile = emptyAsNull(promptFile);
-        if (normalizedPrompt != null && normalizedPromptFile != null) {
-          throw new Error(
-            "Only one of `prompt` or `prompt-file` may be specified."
-          );
+        const normalizedPromptEnvironmentVariable = emptyAsNull(
+          promptEnvironmentVariable
+        );
+        const promptSourceCount = [
+          normalizedPrompt,
+          normalizedPromptFile,
+          normalizedPromptEnvironmentVariable,
+        ].filter((value) => value != null).length;
+        if (promptSourceCount > 1) {
+          throw new Error("Only one prompt source may be specified.");
         }
 
         let promptSource: PromptSource;
         if (normalizedPrompt != null) {
           promptSource = { type: "inline", content: normalizedPrompt };
         } else if (normalizedPromptFile != null) {
           promptSource = { type: "file", path: normalizedPromptFile };
-        } else {
-          throw new Error(
-            "Either `prompt` or `prompt-file` must be specified."
+        } else if (normalizedPromptEnvironmentVariable != null) {
+          const environmentPrompt = emptyAsNull(
+            process.env[normalizedPromptEnvironmentVariable] ?? ""
           );
+          if (environmentPrompt == null) {
+            throw new Error(
+              `Prompt environment variable \`${normalizedPromptEnvironmentVariable}\` is not set or empty.`
+            );
+          }
+          promptSource = { type: "inline", content: environmentPrompt };
+        } else {
+          throw new Error("A prompt source must be specified.");
         }
 
         // Custom option processing to coerces to null does not work with

test/promptSource.test.mjs

@@ -0,0 +1,122 @@
+import assert from "node:assert/strict";
+import { spawnSync } from "node:child_process";
+import {
+  chmodSync,
+  mkdtempSync,
+  readFileSync,
+  rmSync,
+  writeFileSync,
+} from "node:fs";
+import { tmpdir } from "node:os";
+import path from "node:path";
+import { test } from "node:test";
+import { fileURLToPath } from "node:url";
+
+const actionPath = fileURLToPath(new URL("../action.yml", import.meta.url));
+const mainPath = fileURLToPath(new URL("../dist/main.js", import.meta.url));
+
+function runWithEnvironmentPrompt({ directPrompt = "" } = {}) {
+  const tempDir = mkdtempSync(path.join(tmpdir(), "codex-action-prompt-"));
+  const capturePath = path.join(tempDir, "prompt.txt");
+  const outputPath = path.join(tempDir, "output.txt");
+  const fakeCodexPath = path.join(tempDir, "codex.mjs");
+  writeFileSync(
+    fakeCodexPath,
+    `import { readFileSync, writeFileSync } from "node:fs";
+const args = process.argv.slice(2);
+writeFileSync(process.env.CODEX_CAPTURE_PROMPT, readFileSync(0, "utf8"));
+const outputIndex = args.indexOf("--output-last-message");
+writeFileSync(args[outputIndex + 1], "fake final message\\n");
+`
+  );
+  const launcherPath = path.join(tempDir, "codex");
+  writeFileSync(
+    launcherPath,
+    `#!/bin/sh\nexec node "${fakeCodexPath}" "$@"\n`
+  );
+  chmodSync(launcherPath, 0o755);
+  writeFileSync(
+    path.join(tempDir, "codex.cmd"),
+    `@node "${fakeCodexPath}" %*\r\n`
+  );
+
+  const prompt = "first line\nsecond line with spaces";
+  const result = spawnSync(
+    process.execPath,
+    [
+      mainPath,
+      "run-codex-exec",
+      "--prompt",
+      directPrompt,
+      "--prompt-file",
+      "",
+      "--prompt-environment-variable",
+      "CODEX_PROMPT",
+      "--codex-home",
+      "",
+      "--cd",
+      tempDir,
+      "--extra-args",
+      "",
+      "--output-file",
+      outputPath,
+      "--output-schema-file",
+      "",
+      "--output-schema",
+      "",
+      "--sandbox",
+      "",
+      "--permission-profile",
+      "",
+      "--model",
+      "",
+      "--effort",
+      "",
+      "--safety-strategy",
+      "unsafe",
+      "--codex-user",
+      "",
+    ],
+    {
+      encoding: "utf8",
+      env: {
+        ...process.env,
+        PATH: `${tempDir}${path.delimiter}${process.env.PATH ?? ""}`,
+        CODEX_CAPTURE_PROMPT: capturePath,
+        CODEX_PROMPT: prompt,
+      },
+    }
+  );
+
+  let capturedPrompt = null;
+  try {
+    capturedPrompt = readFileSync(capturePath, "utf8");
+  } catch {
+    // Expected when prompt validation rejects the invocation.
+  }
+  rmSync(tempDir, { recursive: true, force: true });
+  return { result, capturedPrompt, prompt };
+}
+
+test("keeps the action inline prompt out of the helper argv", () => {
+  const action = readFileSync(actionPath, "utf8");
+  assert.match(
+    action,
+    /--prompt-environment-variable "\$\{CODEX_PROMPT:\+CODEX_PROMPT\}"/
+  );
+  assert.doesNotMatch(action, /--prompt "\$\{CODEX_PROMPT\}"/);
+
+  const { result, capturedPrompt, prompt } = runWithEnvironmentPrompt();
+  assert.equal(result.status, 0, result.stderr);
+  assert.equal(capturedPrompt, prompt);
+});
+
+test("rejects direct and environment-backed prompts together", () => {
+  const { result, capturedPrompt } = runWithEnvironmentPrompt({
+    directPrompt: "direct prompt",
+  });
+
+  assert.notEqual(result.status, 0);
+  assert.equal(capturedPrompt, null);
+  assert.match(result.stderr, /Only one prompt source may be specified/);
+});