diff --git a/actions/setup/js/checkout_pr_branch.cjs b/actions/setup/js/checkout_pr_branch.cjs
index 4506e3b837..0add419699 100644
--- a/actions/setup/js/checkout_pr_branch.cjs
+++ b/actions/setup/js/checkout_pr_branch.cjs
@@ -26,7 +26,7 @@
  */
 
 const { getErrorMessage } = require("./error_helpers.cjs");
-const { renderTemplateFromFile } = require("./messages_core.cjs");
+const { renderTemplateFromFile, getPromptPath } = require("./messages_core.cjs");
 const { detectForkPR } = require("./pr_helpers.cjs");
 const { ERR_API } = require("./error_codes.cjs");
 
@@ -323,7 +323,7 @@ Pull request #${pullRequest.number} was merged after this workflow was triggered
     core.setOutput("checkout_pr_success", "false");
 
     // Load and render step summary template
-    const templatePath = `${process.env.RUNNER_TEMP}/gh-aw/prompts/pr_checkout_failure.md`;
+    const templatePath = getPromptPath("pr_checkout_failure.md");
     const summaryContent = renderTemplateFromFile(templatePath, {
       error_message: errorMsg,
     });
diff --git a/actions/setup/js/checkout_pr_branch.test.cjs b/actions/setup/js/checkout_pr_branch.test.cjs
index 224f3b01cb..ddb937d729 100644
--- a/actions/setup/js/checkout_pr_branch.test.cjs
+++ b/actions/setup/js/checkout_pr_branch.test.cjs
@@ -121,6 +121,7 @@ describe("checkout_pr_branch.cjs", () => {
       }
       if (module === "./messages_core.cjs") {
         return {
+          getPromptPath: name => `/mock/prompts/${name}`,
           renderTemplateFromFile: (templatePath, context) => {
             const template = mockRequire("fs").readFileSync(templatePath, "utf8");
             return template.replace(/\{(\w+)\}/g, (match, key) => {
diff --git a/actions/setup/js/create_missing_data_issue.cjs b/actions/setup/js/create_missing_data_issue.cjs
index c5d1f3f34a..c08dfd6038 100644
--- a/actions/setup/js/create_missing_data_issue.cjs
+++ b/actions/setup/js/create_missing_data_issue.cjs
@@ -2,6 +2,7 @@
 /// <reference types="@actions/github-script" />
 
 const { buildMissingIssueHandler } = require("./missing_issue_helpers.cjs");
+const { getPromptPath } = require("./messages_core.cjs");
 
 /**
  * @typedef {import('./types/handler-factory').HandlerFactoryFunction} HandlerFactoryFunction
@@ -20,7 +21,7 @@ const main = buildMissingIssueHandler({
   defaultTitlePrefix: "[missing data]",
   defaultLabels: ["agentic-workflows"],
   itemsField: "missing_data",
-  templatePath: `${process.env.RUNNER_TEMP}/gh-aw/prompts/missing_data_issue.md`,
+  templatePath: getPromptPath("missing_data_issue.md"),
   templateListKey: "missing_data_list",
   buildCommentHeader: runUrl => [`## Missing Data Reported`, ``, `The following data was reported as missing during [workflow run](${runUrl}):`, ``],
   renderCommentItem: (item, index) => {
diff --git a/actions/setup/js/create_missing_tool_issue.cjs b/actions/setup/js/create_missing_tool_issue.cjs
index 14ce8af1bb..4df226438a 100644
--- a/actions/setup/js/create_missing_tool_issue.cjs
+++ b/actions/setup/js/create_missing_tool_issue.cjs
@@ -2,6 +2,7 @@
 /// <reference types="@actions/github-script" />
 
 const { buildMissingIssueHandler } = require("./missing_issue_helpers.cjs");
+const { getPromptPath } = require("./messages_core.cjs");
 
 /**
  * @typedef {import('./types/handler-factory').HandlerFactoryFunction} HandlerFactoryFunction
@@ -20,7 +21,7 @@ const main = buildMissingIssueHandler({
   defaultTitlePrefix: "[missing tool]",
   defaultLabels: ["agentic-workflows"],
   itemsField: "missing_tools",
-  templatePath: `${process.env.RUNNER_TEMP}/gh-aw/prompts/missing_tool_issue.md`,
+  templatePath: getPromptPath("missing_tool_issue.md"),
   templateListKey: "missing_tools_list",
   buildCommentHeader: runUrl => [`## Missing Tools Reported`, ``, `The following tools were reported as missing during [workflow run](${runUrl}):`, ``],
   renderCommentItem: (tool, index) => {
diff --git a/actions/setup/js/create_pull_request.cjs b/actions/setup/js/create_pull_request.cjs
index bbee0b6bbe..d90ac8d2d1 100644
--- a/actions/setup/js/create_pull_request.cjs
+++ b/actions/setup/js/create_pull_request.cjs
@@ -26,7 +26,7 @@ const { getBaseBranch } = require("./get_base_branch.cjs");
 const { createAuthenticatedGitHubClient } = require("./handler_auth.cjs");
 const { buildWorkflowRunUrl } = require("./workflow_metadata_helpers.cjs");
 const { checkFileProtection } = require("./manifest_file_helpers.cjs");
-const { renderTemplateFromFile, buildProtectedFileList, encodePathSegments } = require("./messages_core.cjs");
+const { renderTemplateFromFile, buildProtectedFileList, encodePathSegments, getPromptPath } = require("./messages_core.cjs");
 const { COPILOT_REVIEWER_BOT, FAQ_CREATE_PR_PERMISSIONS_URL, MAX_ASSIGNEES } = require("./constants.cjs");
 const { isStagedMode } = require("./safe_output_helpers.cjs");
 const { withRetry, isTransientError } = require("./error_recovery.cjs");
@@ -1617,7 +1617,7 @@ ${patchPreview}`;
         // Use the push-failed template with artifact download instructions.
         const runId = context.runId;
         const patchFileName = patchFilePath ? patchFilePath.replace("/tmp/gh-aw/", "") : "aw-unknown.patch";
-        const pushFailedTemplatePath = `${process.env.RUNNER_TEMP}/gh-aw/prompts/manifest_protection_push_failed_fallback.md`;
+        const pushFailedTemplatePath = getPromptPath("manifest_protection_push_failed_fallback.md");
         fallbackBody = renderTemplateFromFile(pushFailedTemplatePath, {
           main_body: mainBodyContent,
           footer: footerContent,
@@ -1634,7 +1634,7 @@ ${patchPreview}`;
         const encodedBase = encodePathSegments(baseBranch);
         const encodedHead = encodePathSegments(branchName);
         const createPrUrl = `${githubServer}/${repoParts.owner}/${repoParts.repo}/compare/${encodedBase}...${encodedHead}?expand=1&title=${encodeURIComponent(title)}`;
-        const templatePath = `${process.env.RUNNER_TEMP}/gh-aw/prompts/manifest_protection_create_pr_fallback.md`;
+        const templatePath = getPromptPath("manifest_protection_create_pr_fallback.md");
         fallbackBody = renderTemplateFromFile(templatePath, {
           main_body: mainBodyContent,
           footer: footerContent,
@@ -1834,7 +1834,7 @@ ${patchPreview}`;
           patchPreview = generatePatchPreview(patchContent);
         }
 
-        const fallbackTemplatePath = `${process.env.RUNNER_TEMP}/gh-aw/prompts/pr_permission_denied_fallback.md`;
+        const fallbackTemplatePath = getPromptPath("pr_permission_denied_fallback.md");
         const fallbackBody = renderTemplateFromFile(fallbackTemplatePath, {
           body,
           branch_name: branchName,
diff --git a/actions/setup/js/create_report_incomplete_issue.cjs b/actions/setup/js/create_report_incomplete_issue.cjs
index 63cca4ffc7..09001cbc78 100644
--- a/actions/setup/js/create_report_incomplete_issue.cjs
+++ b/actions/setup/js/create_report_incomplete_issue.cjs
@@ -2,6 +2,7 @@
 /// <reference types="@actions/github-script" />
 
 const { buildMissingIssueHandler } = require("./missing_issue_helpers.cjs");
+const { getPromptPath } = require("./messages_core.cjs");
 
 /**
  * @typedef {import('./types/handler-factory').HandlerFactoryFunction} HandlerFactoryFunction
@@ -22,7 +23,7 @@ const main = buildMissingIssueHandler({
   defaultTitlePrefix: "[incomplete]",
   defaultLabels: ["agentic-workflows"],
   itemsField: "incomplete_signals",
-  templatePath: `${process.env.RUNNER_TEMP}/gh-aw/prompts/missing_tool_issue.md`,
+  templatePath: getPromptPath("missing_tool_issue.md"),
   templateListKey: "incomplete_signals_list",
   buildCommentHeader: runUrl => [`## Incomplete Run Reported`, ``, `The agent reported that the task could not be completed during [workflow run](${runUrl}):`, ``],
   renderCommentItem: (item, index) => {
diff --git a/actions/setup/js/firewall_blocked_domains.cjs b/actions/setup/js/firewall_blocked_domains.cjs
index d9cd415042..eb5dbc07ca 100644
--- a/actions/setup/js/firewall_blocked_domains.cjs
+++ b/actions/setup/js/firewall_blocked_domains.cjs
@@ -11,7 +11,7 @@
 const fs = require("fs");
 const path = require("path");
 const { sanitizeDomainName } = require("./sanitize_content_core.cjs");
-const { renderTemplateFromFile } = require("./messages_core.cjs");
+const { renderTemplateFromFile, getPromptPath } = require("./messages_core.cjs");
 const { renderMarkdownTemplate } = require("./render_template.cjs");
 
 /**
@@ -207,10 +207,11 @@ function generateBlockedDomainsSection(blockedDomains, templatePath) {
 
   const hasGitHubApiBlocked = blockedDomains.includes("api.github.com");
 
-  // Resolve template path: explicit > RUNNER_TEMP (production) > source tree (local dev/test)
+  // Resolve template path: explicit > GH_AW_PROMPTS_DIR / RUNNER_TEMP (production) > source tree (local dev/test)
   let resolvedTemplatePath = templatePath;
   if (!resolvedTemplatePath) {
-    resolvedTemplatePath = process.env.RUNNER_TEMP ? `${process.env.RUNNER_TEMP}/gh-aw/prompts/firewall_blocked_domains.md` : path.join(__dirname, "../md/firewall_blocked_domains.md");
+    const hasRuntimePromptsDir = !!(process.env.RUNNER_TEMP || process.env.GH_AW_PROMPTS_DIR);
+    resolvedTemplatePath = hasRuntimePromptsDir ? getPromptPath("firewall_blocked_domains.md") : path.join(__dirname, "../md/firewall_blocked_domains.md");
   }
 
   // First pass: substitute {key} placeholders.
diff --git a/actions/setup/js/handle_agent_failure.cjs b/actions/setup/js/handle_agent_failure.cjs
index cc68ab0825..ef87832807 100644
--- a/actions/setup/js/handle_agent_failure.cjs
+++ b/actions/setup/js/handle_agent_failure.cjs
@@ -4,7 +4,7 @@
 const { getErrorMessage } = require("./error_helpers.cjs");
 const { sanitizeContent } = require("./sanitize_content.cjs");
 const { getDetectionCautionAlert, getFooterAgentFailureIssueMessage, getFooterAgentFailureCommentMessage, generateXMLMarker } = require("./messages.cjs");
-const { renderTemplate, renderTemplateFromFile } = require("./messages_core.cjs");
+const { renderTemplate, renderTemplateFromFile, getPromptPath } = require("./messages_core.cjs");
 const { getCurrentBranch } = require("./get_current_branch.cjs");
 const { createExpirationLine, generateFooterWithExpiration } = require("./ephemerals.cjs");
 const { MAX_SUB_ISSUES, getSubIssueCount } = require("./sub_issue_helpers.cjs");
@@ -618,7 +618,7 @@ function buildMissingDataContext(cacheMemoryEnabled) {
   const hasCacheMiss = missingDataMessages.some(m => m.reason === "cache_memory_miss");
   if (cacheMemoryEnabled && hasCacheMiss) {
     core.info("Cache-miss detected despite cache-memory being available — likely a configuration problem");
-    const templatePath = `${process.env.RUNNER_TEMP}/gh-aw/prompts/cache_memory_miss.md`;
+    const templatePath = getPromptPath("cache_memory_miss.md");
     context += "\n" + renderTemplateFromFile(templatePath, {}) + "\n";
   }
 
@@ -697,7 +697,7 @@ function buildTimeoutContext(isTimedOut, timeoutMinutes) {
   const currentMinutes = parseInt(timeoutMinutes || "20", 10);
   const suggestedMinutes = currentMinutes + 10;
 
-  const templatePath = `${process.env.RUNNER_TEMP}/gh-aw/prompts/agent_timeout.md`;
+  const templatePath = getPromptPath("agent_timeout.md");
   return "\n" + renderTemplateFromFile(templatePath, { current_minutes: currentMinutes, suggested_minutes: suggestedMinutes });
 }
 
@@ -711,7 +711,7 @@ function buildInferenceAccessErrorContext(hasInferenceAccessError) {
     return "";
   }
 
-  const templatePath = `${process.env.RUNNER_TEMP}/gh-aw/prompts/inference_access_error.md`;
+  const templatePath = getPromptPath("inference_access_error.md");
   const template = fs.readFileSync(templatePath, "utf8");
   return "\n" + template;
 }
@@ -727,7 +727,7 @@ function buildMCPPolicyErrorContext(hasMCPPolicyError) {
     return "";
   }
 
-  const templatePath = `${process.env.RUNNER_TEMP}/gh-aw/prompts/mcp_policy_error.md`;
+  const templatePath = getPromptPath("mcp_policy_error.md");
   try {
     const template = fs.readFileSync(templatePath, "utf8");
     return "\n" + template;
@@ -752,7 +752,7 @@ function buildModelNotSupportedErrorContext(hasModelNotSupportedError) {
     return "";
   }
 
-  const templatePath = `${process.env.RUNNER_TEMP}/gh-aw/prompts/model_not_supported_error.md`;
+  const templatePath = getPromptPath("model_not_supported_error.md");
   try {
     const template = fs.readFileSync(templatePath, "utf8");
     return "\n" + template;
@@ -790,7 +790,7 @@ function buildLockdownCheckFailedContext(hasLockdownCheckFailed) {
     return "";
   }
 
-  const templatePath = `${process.env.RUNNER_TEMP}/gh-aw/prompts/lockdown_check_failed.md`;
+  const templatePath = getPromptPath("lockdown_check_failed.md");
   const template = fs.readFileSync(templatePath, "utf8");
   return "\n" + template;
 }
@@ -807,7 +807,7 @@ function buildStaleLockFileFailedContext(hasStaleLockFileFailed) {
     return "";
   }
 
-  const templatePath = `${process.env.RUNNER_TEMP}/gh-aw/prompts/stale_lock_file_failed.md`;
+  const templatePath = getPromptPath("stale_lock_file_failed.md");
   const template = fs.readFileSync(templatePath, "utf8");
   return "\n" + template;
 }
@@ -837,7 +837,7 @@ function buildAssignCopilotFailureContext(hasAssignCopilotFailures, assignCopilo
     }
   }
 
-  const templatePath = `${process.env.RUNNER_TEMP}/gh-aw/prompts/assign_copilot_to_created_issues_failure.md`;
+  const templatePath = getPromptPath("assign_copilot_to_created_issues_failure.md");
   return "\n" + renderTemplateFromFile(templatePath, { issues: issueList });
 }
 
@@ -915,7 +915,7 @@ function buildEngineFailureContext() {
       const hasCyberPolicyViolation = Array.from(errorMessages).some(msg => msg.includes("cyber_policy_violation"));
       if (hasCyberPolicyViolation) {
         core.info("Detected cyber_policy_violation error — using dedicated context message");
-        const templatePath = `${process.env.RUNNER_TEMP}/gh-aw/prompts/cyber_policy_violation.md`;
+        const templatePath = getPromptPath("cyber_policy_violation.md");
         try {
           return "\n" + renderTemplateFromFile(templatePath, {});
         } catch {
@@ -1263,7 +1263,7 @@ async function main() {
         core.info(`Found existing issue #${existingIssue.number}: ${existingIssue.html_url}`);
 
         // Read comment template
-        const commentTemplatePath = `${process.env.RUNNER_TEMP}/gh-aw/prompts/agent_failure_comment.md`;
+        const commentTemplatePath = getPromptPath("agent_failure_comment.md");
         const commentTemplate = fs.readFileSync(commentTemplatePath, "utf8");
 
         // Extract run ID from URL (e.g., https://github.com/owner/repo/actions/runs/123 -> "123")
@@ -1428,7 +1428,7 @@ async function main() {
         core.info("No existing issue found, creating a new one");
 
         // Read issue template
-        const issueTemplatePath = `${process.env.RUNNER_TEMP}/gh-aw/prompts/agent_failure_issue.md`;
+        const issueTemplatePath = getPromptPath("agent_failure_issue.md");
         const issueTemplate = fs.readFileSync(issueTemplatePath, "utf8");
 
         // Get current branch information
diff --git a/actions/setup/js/handle_agent_failure.test.cjs b/actions/setup/js/handle_agent_failure.test.cjs
index 4934ffdd4a..acc08845cd 100644
--- a/actions/setup/js/handle_agent_failure.test.cjs
+++ b/actions/setup/js/handle_agent_failure.test.cjs
@@ -505,6 +505,7 @@ describe("handle_agent_failure", () => {
 
     beforeEach(() => {
       vi.resetModules();
+      process.env.RUNNER_TEMP = "/nonexistent";
       // Stub readFileSync so the runtime path resolves to the source-tree template
       fs.readFileSync = (filePath, encoding) => {
         if (typeof filePath === "string" && filePath.includes("lockdown_check_failed.md")) {
@@ -517,6 +518,7 @@ describe("handle_agent_failure", () => {
 
     afterEach(() => {
       fs.readFileSync = originalReadFileSync;
+      delete process.env.RUNNER_TEMP;
     });
 
     it("returns empty string when no failure", () => {
@@ -553,6 +555,7 @@ describe("handle_agent_failure", () => {
 
     beforeEach(() => {
       vi.resetModules();
+      process.env.RUNNER_TEMP = "/nonexistent";
       fs.readFileSync = (filePath, encoding) => {
         if (typeof filePath === "string" && filePath.includes("stale_lock_file_failed.md")) {
           return templateContent;
@@ -564,6 +567,7 @@ describe("handle_agent_failure", () => {
 
     afterEach(() => {
       fs.readFileSync = originalReadFileSync;
+      delete process.env.RUNNER_TEMP;
     });
 
     it("returns empty string when check did not fail", () => {
@@ -605,6 +609,7 @@ describe("handle_agent_failure", () => {
 
     beforeEach(() => {
       vi.resetModules();
+      process.env.RUNNER_TEMP = "/nonexistent";
       // Stub readFileSync so the runtime path resolves to the source-tree template
       fs.readFileSync = (filePath, encoding) => {
         if (typeof filePath === "string" && filePath.includes("agent_timeout.md")) {
@@ -617,6 +622,7 @@ describe("handle_agent_failure", () => {
 
     afterEach(() => {
       fs.readFileSync = originalReadFileSync;
+      delete process.env.RUNNER_TEMP;
     });
 
     it("returns empty string when not timed out", () => {
diff --git a/actions/setup/js/handle_detection_runs.cjs b/actions/setup/js/handle_detection_runs.cjs
index ff86d0e3de..91fe932988 100644
--- a/actions/setup/js/handle_detection_runs.cjs
+++ b/actions/setup/js/handle_detection_runs.cjs
@@ -6,7 +6,7 @@ const { getErrorMessage } = require("./error_helpers.cjs");
 const { ERR_API } = require("./error_codes.cjs");
 const { sanitizeContent } = require("./sanitize_content.cjs");
 const { generateFooterWithExpiration } = require("./ephemerals.cjs");
-const { renderTemplateFromFile } = require("./messages_core.cjs");
+const { renderTemplateFromFile, getPromptPath } = require("./messages_core.cjs");
 const { getEffectiveTokensSuffix } = require("./effective_tokens.cjs");
 
 /**
@@ -46,7 +46,7 @@ async function ensureDetectionRunsIssue() {
   core.info(`No detection runs issue found, creating one`);
 
   // Load template from file
-  const templatePath = `${process.env.RUNNER_TEMP}/gh-aw/prompts/detection_runs_issue.md`;
+  const templatePath = getPromptPath("detection_runs_issue.md");
   const parentBodyContent = fs.readFileSync(templatePath, "utf8");
 
   const parentBody = generateFooterWithExpiration({
@@ -107,7 +107,7 @@ async function main() {
     }
 
     // Load and render comment template from file
-    const commentTemplatePath = `${process.env.RUNNER_TEMP}/gh-aw/prompts/detection_runs_comment.md`;
+    const commentTemplatePath = getPromptPath("detection_runs_comment.md");
 
     // Compute effective tokens suffix from environment variable (set by parse_token_usage.cjs / parse_mcp_gateway_log.cjs)
     const effectiveTokensSuffix = getEffectiveTokensSuffix();
diff --git a/actions/setup/js/handle_noop_message.cjs b/actions/setup/js/handle_noop_message.cjs
index e583b6e310..bd522b7698 100644
--- a/actions/setup/js/handle_noop_message.cjs
+++ b/actions/setup/js/handle_noop_message.cjs
@@ -6,7 +6,7 @@ const { getErrorMessage } = require("./error_helpers.cjs");
 const { ERR_API } = require("./error_codes.cjs");
 const { sanitizeContent } = require("./sanitize_content.cjs");
 const { generateFooterWithExpiration } = require("./ephemerals.cjs");
-const { renderTemplateFromFile } = require("./messages_core.cjs");
+const { renderTemplateFromFile, getPromptPath } = require("./messages_core.cjs");
 const { loadAgentOutput } = require("./load_agent_output.cjs");
 const { isStagedMode } = require("./safe_output_helpers.cjs");
 const { getEffectiveTokensSuffix } = require("./effective_tokens.cjs");
@@ -48,7 +48,7 @@ async function ensureAgentRunsIssue() {
   core.info(`No no-op runs issue found, creating one`);
 
   // Load template from file
-  const templatePath = `${process.env.RUNNER_TEMP}/gh-aw/prompts/noop_runs_issue.md`;
+  const templatePath = getPromptPath("noop_runs_issue.md");
   const parentBodyContent = fs.readFileSync(templatePath, "utf8");
 
   const parentBody = generateFooterWithExpiration({
@@ -184,7 +184,7 @@ async function main() {
     }
 
     // Load and render comment template from file
-    const commentTemplatePath = `${process.env.RUNNER_TEMP}/gh-aw/prompts/noop_comment.md`;
+    const commentTemplatePath = getPromptPath("noop_comment.md");
 
     // Compute effective tokens suffix from environment variable (set by parse_token_usage.cjs / parse_mcp_gateway_log.cjs)
     const effectiveTokensSuffix = getEffectiveTokensSuffix();
diff --git a/actions/setup/js/messages_core.cjs b/actions/setup/js/messages_core.cjs
index ad1c3e8880..646f467f6f 100644
--- a/actions/setup/js/messages_core.cjs
+++ b/actions/setup/js/messages_core.cjs
@@ -84,6 +84,22 @@ function renderTemplate(template, context) {
   });
 }
 
+/**
+ * Resolve the absolute path to a prompt template file.
+ * Prefers GH_AW_PROMPTS_DIR when set, otherwise falls back to
+ * ${RUNNER_TEMP}/gh-aw/prompts (the runtime location used in production).
+ * Throws if neither GH_AW_PROMPTS_DIR nor RUNNER_TEMP is set.
+ * @param {string} name - Template filename (e.g. "agent_timeout.md")
+ * @returns {string} Absolute path to the prompt template file
+ */
+function getPromptPath(name) {
+  const promptsDir = process.env.GH_AW_PROMPTS_DIR || (process.env.RUNNER_TEMP ? `${process.env.RUNNER_TEMP}/gh-aw/prompts` : null);
+  if (!promptsDir) {
+    throw new Error("Cannot resolve prompt path: neither GH_AW_PROMPTS_DIR nor RUNNER_TEMP is set");
+  }
+  return `${promptsDir}/${name}`;
+}
+
 /**
  * Read a template file and render it with the given context.
  * Combines file loading and template rendering into a single helper.
@@ -169,6 +185,7 @@ function buildProtectedFileList(files, githubServer, owner, repo, branch) {
 
 module.exports = {
   getMessages,
+  getPromptPath,
   renderTemplate,
   renderTemplateFromFile,
   toSnakeCase,
diff --git a/actions/setup/js/messages_core.test.cjs b/actions/setup/js/messages_core.test.cjs
index 078dc273b0..69ca483d64 100644
--- a/actions/setup/js/messages_core.test.cjs
+++ b/actions/setup/js/messages_core.test.cjs
@@ -26,6 +26,8 @@ describe("messages_core.cjs", () => {
     vi.clearAllMocks();
     vi.resetModules();
     delete process.env.GH_AW_SAFE_OUTPUT_MESSAGES;
+    delete process.env.GH_AW_PROMPTS_DIR;
+    delete process.env.RUNNER_TEMP;
   });
 
   describe("renderTemplate", () => {
@@ -181,6 +183,42 @@ describe("messages_core.cjs", () => {
     });
   });
 
+  describe("getPromptPath", () => {
+    it("should use RUNNER_TEMP when no override is set", async () => {
+      process.env.RUNNER_TEMP = "/tmp/runner";
+      const { getPromptPath } = await import("./messages_core.cjs?" + Date.now());
+      const result = getPromptPath("agent_timeout.md");
+      expect(result).toBe("/tmp/runner/gh-aw/prompts/agent_timeout.md");
+    });
+
+    it("should prefer GH_AW_PROMPTS_DIR over RUNNER_TEMP", async () => {
+      process.env.RUNNER_TEMP = "/tmp/runner";
+      process.env.GH_AW_PROMPTS_DIR = "/custom/prompts";
+      const { getPromptPath } = await import("./messages_core.cjs?" + Date.now());
+      const result = getPromptPath("agent_timeout.md");
+      expect(result).toBe("/custom/prompts/agent_timeout.md");
+    });
+
+    it("should use GH_AW_PROMPTS_DIR when RUNNER_TEMP is not set", async () => {
+      process.env.GH_AW_PROMPTS_DIR = "/custom/prompts";
+      const { getPromptPath } = await import("./messages_core.cjs?" + Date.now());
+      const result = getPromptPath("cache_memory_miss.md");
+      expect(result).toBe("/custom/prompts/cache_memory_miss.md");
+    });
+
+    it("should include the template name in the path", async () => {
+      process.env.RUNNER_TEMP = "/tmp/runner";
+      const { getPromptPath } = await import("./messages_core.cjs?" + Date.now());
+      expect(getPromptPath("foo.md")).toBe("/tmp/runner/gh-aw/prompts/foo.md");
+      expect(getPromptPath("bar.md")).toBe("/tmp/runner/gh-aw/prompts/bar.md");
+    });
+
+    it("should throw when neither GH_AW_PROMPTS_DIR nor RUNNER_TEMP is set", async () => {
+      const { getPromptPath } = await import("./messages_core.cjs?" + Date.now());
+      expect(() => getPromptPath("any.md")).toThrow("Cannot resolve prompt path: neither GH_AW_PROMPTS_DIR nor RUNNER_TEMP is set");
+    });
+  });
+
   describe("getMessages", () => {
     it("should return null when env var is not set", async () => {
       const { getMessages } = await import("./messages_core.cjs?" + Date.now());
diff --git a/actions/setup/js/push_to_pull_request_branch.cjs b/actions/setup/js/push_to_pull_request_branch.cjs
index 70d9bf14ba..7742d6585f 100644
--- a/actions/setup/js/push_to_pull_request_branch.cjs
+++ b/actions/setup/js/push_to_pull_request_branch.cjs
@@ -15,7 +15,7 @@ const { resolveTargetRepoConfig, resolveAndValidateRepo } = require("./repo_help
 const { createAuthenticatedGitHubClient } = require("./handler_auth.cjs");
 const { checkFileProtection } = require("./manifest_file_helpers.cjs");
 const { buildWorkflowRunUrl } = require("./workflow_metadata_helpers.cjs");
-const { renderTemplateFromFile, buildProtectedFileList } = require("./messages_core.cjs");
+const { renderTemplateFromFile, buildProtectedFileList, getPromptPath } = require("./messages_core.cjs");
 const { getGitAuthEnv } = require("./git_helpers.cjs");
 const { findRepoCheckout } = require("./find_repo_checkout.cjs");
 
@@ -467,7 +467,7 @@ async function main(config = {}) {
       const prUrl = `${githubServer}/${repoParts.owner}/${repoParts.repo}/pull/${pullNumber}`;
       const issueTitle = `[gh-aw] Protected Files: ${prTitle || `PR #${pullNumber}`}`;
       const fileList = buildProtectedFileList(protectedFilesForFallback, githubServer, repoParts.owner, repoParts.repo, branchName);
-      const templatePath = `${process.env.RUNNER_TEMP}/gh-aw/prompts/manifest_protection_push_to_pr_fallback.md`;
+      const templatePath = getPromptPath("manifest_protection_push_to_pr_fallback.md");
       const issueBody = renderTemplateFromFile(templatePath, {
         files: fileList,
         pull_number: pullNumber,
diff --git a/actions/setup/js/setup_threat_detection.cjs b/actions/setup/js/setup_threat_detection.cjs
index 754f990171..febd94eb7b 100644
--- a/actions/setup/js/setup_threat_detection.cjs
+++ b/actions/setup/js/setup_threat_detection.cjs
@@ -17,6 +17,7 @@ const path = require("path");
 const { checkFileExists } = require("./file_helpers.cjs");
 const { AGENT_OUTPUT_FILENAME } = require("./constants.cjs");
 const { ERR_VALIDATION } = require("./error_codes.cjs");
+const { getPromptPath } = require("./messages_core.cjs");
 
 /**
  * Main entry point for setting up threat detection
@@ -24,8 +25,7 @@ const { ERR_VALIDATION } = require("./error_codes.cjs");
  */
 async function main() {
   // Read the threat detection template from file
-  // At runtime, markdown files are copied to ${RUNNER_TEMP}/gh-aw/prompts/ by the setup action
-  const templatePath = `${process.env.RUNNER_TEMP}/gh-aw/prompts/threat_detection.md`;
+  const templatePath = getPromptPath("threat_detection.md");
   if (!fs.existsSync(templatePath)) {
     core.setFailed(`${ERR_VALIDATION}: Threat detection template not found at: ${templatePath}`);
     return;