diff --git a/actions/setup/js/check_command_position.cjs b/actions/setup/js/check_command_position.cjs
index 5c8b6ef04a1..349ccf1f114 100644
--- a/actions/setup/js/check_command_position.cjs
+++ b/actions/setup/js/check_command_position.cjs
@@ -2,6 +2,7 @@
 /// <reference types="@actions/github-script" />
 
 const { ERR_API, ERR_CONFIG, ERR_VALIDATION } = require("./error_codes.cjs");
+const { writeDenialSummary } = require("./pre_activation_summary.cjs");
 
 /**
  * Check if command is the first word in the triggering text
@@ -100,6 +101,10 @@ async function main() {
       core.warning(`⚠️ None of the commands [${expectedCommands}] matched the first word (found: '${firstWord}'). Workflow will be skipped.`);
       core.setOutput("command_position_ok", "false");
       core.setOutput("matched_command", "");
+      await writeDenialSummary(
+        `The trigger comment did not start with a required command. Expected one of: ${expectedCommands}. Found: \`${firstWord}\`.`,
+        "Make sure the trigger comment starts with the required command defined in `on.command:` in the workflow frontmatter."
+      );
     }
   } catch (error) {
     core.setFailed(`${ERR_API}: ${getErrorMessage(error)}`);
diff --git a/actions/setup/js/check_membership.cjs b/actions/setup/js/check_membership.cjs
index 85427cf7082..712f3606c04 100644
--- a/actions/setup/js/check_membership.cjs
+++ b/actions/setup/js/check_membership.cjs
@@ -2,6 +2,7 @@
 /// <reference types="@actions/github-script" />
 
 const { parseRequiredPermissions, parseAllowedBots, checkRepositoryPermission, checkBotStatus, isAllowedBot } = require("./check_permissions_utils.cjs");
+const { writeDenialSummary } = require("./pre_activation_summary.cjs");
 
 async function main() {
   const { eventName } = context;
@@ -46,6 +47,7 @@ async function main() {
     core.setOutput("is_team_member", "false");
     core.setOutput("result", "config_error");
     core.setOutput("error_message", "Configuration error: Required permissions not specified");
+    await writeDenialSummary("Configuration error: Required permissions not specified.", "Contact the repository administrator to fix the workflow frontmatter configuration.");
     return;
   }
 
@@ -76,11 +78,13 @@ async function main() {
           core.setOutput("user_permission", "bot");
           return;
         } else if (botStatus.isBot && !botStatus.isActive) {
+          const errorMessage = `Access denied: Bot '${actor}' is not active/installed on this repository`;
           core.warning(`Bot '${actor}' is in the allowed list but not active/installed on ${owner}/${repo}`);
           core.setOutput("is_team_member", "false");
           core.setOutput("result", "bot_not_active");
           core.setOutput("user_permission", result.permission ?? "bot");
-          core.setOutput("error_message", `Access denied: Bot '${actor}' is not active/installed on this repository`);
+          core.setOutput("error_message", errorMessage);
+          await writeDenialSummary(errorMessage, "The bot is in the allowed list but is not installed or active on this repository. Install the GitHub App and try again.");
           return;
         } else {
           core.info(`Actor '${actor}' is in allowed bots list but bot status check failed`);
@@ -90,18 +94,20 @@ async function main() {
 
     // Not authorized by role or bot
     if (result.error) {
+      const errorMessage = `Repository permission check failed: ${result.error}`;
       core.setOutput("is_team_member", "false");
       core.setOutput("result", "api_error");
-      core.setOutput("error_message", `Repository permission check failed: ${result.error}`);
+      core.setOutput("error_message", errorMessage);
+      await writeDenialSummary(errorMessage, "The permission check failed with a GitHub API error. Check the `pre_activation` job log for details.");
     } else {
+      const errorMessage =
+        `Access denied: User '${actor}' is not authorized. Required permissions: ${requiredPermissions.join(", ")}. ` +
+        `To allow this user to run the workflow, add their role to the frontmatter. Example: roles: [${requiredPermissions.join(", ")}, ${result.permission}]`;
       core.setOutput("is_team_member", "false");
       core.setOutput("result", "insufficient_permissions");
       core.setOutput("user_permission", result.permission);
-      core.setOutput(
-        "error_message",
-        `Access denied: User '${actor}' is not authorized. Required permissions: ${requiredPermissions.join(", ")}. ` +
-          `To allow this user to run the workflow, add their role to the frontmatter. Example: roles: [${requiredPermissions.join(", ")}, ${result.permission}]`
-      );
+      core.setOutput("error_message", errorMessage);
+      await writeDenialSummary(errorMessage, `To allow a bot or GitHub App actor, add it to \`on.bots:\` in the workflow frontmatter. ` + `To change the required roles for human actors, update \`on.roles:\` in the workflow frontmatter.`);
     }
   }
 }
diff --git a/actions/setup/js/check_membership.test.cjs b/actions/setup/js/check_membership.test.cjs
index adb04b06098..3432f24162a 100644
--- a/actions/setup/js/check_membership.test.cjs
+++ b/actions/setup/js/check_membership.test.cjs
@@ -86,6 +86,13 @@ describe("check_membership.cjs", () => {
         utilsFunction(mockCore, mockGithub, mockContext, process, mockModule, moduleExports, mockRequire);
         return mockModule.exports;
       }
+      if (modulePath === "./pre_activation_summary.cjs") {
+        return {
+          writeDenialSummary: async (reason, remediation) => {
+            await mockCore.summary.addRaw(`${reason}\n${remediation}`).write();
+          },
+        };
+      }
       throw new Error(`Module not found: ${modulePath}`);
     };
 
diff --git a/actions/setup/js/check_skip_bots.cjs b/actions/setup/js/check_skip_bots.cjs
index 3dc528beb5c..78c53294c59 100644
--- a/actions/setup/js/check_skip_bots.cjs
+++ b/actions/setup/js/check_skip_bots.cjs
@@ -1,6 +1,8 @@
 // @ts-check
 /// <reference types="@actions/github-script" />
 
+const { writeDenialSummary } = require("./pre_activation_summary.cjs");
+
 /**
  * Check if the workflow should be skipped based on bot/user identity
  * Reads skip-bots from GH_AW_SKIP_BOTS environment variable
@@ -48,10 +50,12 @@ async function main() {
 
   if (isSkipped) {
     // User is in skip-bots, skip the workflow
+    const errorMessage = `Workflow skipped: User '${actor}' is in skip-bots: [${skipBots.join(", ")}]`;
     core.info(`❌ User '${actor}' is in skip-bots [${skipBots.join(", ")}]. Workflow will be skipped.`);
     core.setOutput("skip_bots_ok", "false");
     core.setOutput("result", "skipped");
-    core.setOutput("error_message", `Workflow skipped: User '${actor}' is in skip-bots: [${skipBots.join(", ")}]`);
+    core.setOutput("error_message", errorMessage);
+    await writeDenialSummary(errorMessage, "Update `on.skip-bots:` in the workflow frontmatter to change which bots are excluded.");
   } else {
     // User is NOT in skip-bots, allow workflow to proceed
     core.info(`✅ User '${actor}' is NOT in skip-bots [${skipBots.join(", ")}]. Workflow will proceed.`);
diff --git a/actions/setup/js/check_skip_bots.test.cjs b/actions/setup/js/check_skip_bots.test.cjs
index 765e07279f1..151392f5bd3 100644
--- a/actions/setup/js/check_skip_bots.test.cjs
+++ b/actions/setup/js/check_skip_bots.test.cjs
@@ -12,6 +12,10 @@ describe("check_skip_bots.cjs", () => {
       error: vi.fn(),
       setFailed: vi.fn(),
       setOutput: vi.fn(),
+      summary: {
+        addRaw: vi.fn().mockReturnThis(),
+        write: vi.fn().mockResolvedValue(undefined),
+      },
     };
 
     mockContext = {
diff --git a/actions/setup/js/check_skip_if_check_failing.cjs b/actions/setup/js/check_skip_if_check_failing.cjs
index fff1ebd93b7..97d0ff5475c 100644
--- a/actions/setup/js/check_skip_if_check_failing.cjs
+++ b/actions/setup/js/check_skip_if_check_failing.cjs
@@ -4,6 +4,7 @@
 const { getErrorMessage, isRateLimitError } = require("./error_helpers.cjs");
 const { ERR_API } = require("./error_codes.cjs");
 const { getBaseBranch } = require("./get_base_branch.cjs");
+const { writeDenialSummary } = require("./pre_activation_summary.cjs");
 
 /**
  * Determines the ref to check for CI status.
@@ -206,6 +207,7 @@ async function main() {
       const names = failingChecks.map(r => (r.status === "completed" ? `${r.name} (${r.conclusion})` : `${r.name} (${r.status})`)).join(", ");
       core.warning(`⚠️ Failing CI checks detected on "${ref}": ${names}. Workflow execution will be prevented by activation job.`);
       core.setOutput("skip_if_check_failing_ok", "false");
+      await writeDenialSummary(`Failing CI checks detected on \`${ref}\`: ${names}.`, "Fix the failing check(s) referenced in `on.skip-if-check-failing:`, or update the frontmatter configuration.");
       return;
     }
 
diff --git a/actions/setup/js/check_skip_if_check_failing.test.cjs b/actions/setup/js/check_skip_if_check_failing.test.cjs
index a1e8e303115..e60ca5fe0e7 100644
--- a/actions/setup/js/check_skip_if_check_failing.test.cjs
+++ b/actions/setup/js/check_skip_if_check_failing.test.cjs
@@ -12,6 +12,10 @@ describe("check_skip_if_check_failing.cjs", () => {
       error: vi.fn(),
       setFailed: vi.fn(),
       setOutput: vi.fn(),
+      summary: {
+        addRaw: vi.fn().mockReturnThis(),
+        write: vi.fn().mockResolvedValue(undefined),
+      },
     };
 
     mockGithub = {
diff --git a/actions/setup/js/check_skip_if_match.cjs b/actions/setup/js/check_skip_if_match.cjs
index 074605cfca7..fc379c91e7a 100644
--- a/actions/setup/js/check_skip_if_match.cjs
+++ b/actions/setup/js/check_skip_if_match.cjs
@@ -4,6 +4,7 @@
 const { getErrorMessage } = require("./error_helpers.cjs");
 const { ERR_API, ERR_CONFIG } = require("./error_codes.cjs");
 const { buildSearchQuery } = require("./check_skip_if_helpers.cjs");
+const { writeDenialSummary } = require("./pre_activation_summary.cjs");
 
 async function main() {
   const { GH_AW_SKIP_QUERY: skipQuery, GH_AW_WORKFLOW_NAME: workflowName, GH_AW_SKIP_MAX_MATCHES: maxMatchesStr = "1", GH_AW_SKIP_SCOPE: skipScope } = process.env;
@@ -42,6 +43,7 @@ async function main() {
     if (totalCount >= maxMatches) {
       core.warning(`🔍 Skip condition matched (${totalCount} items found, threshold: ${maxMatches}). Workflow execution will be prevented by activation job.`);
       core.setOutput("skip_check_ok", "false");
+      await writeDenialSummary(`Skip-if-match query matched: ${totalCount} item(s) found (threshold: ${maxMatches}).`, "Update `on.skip-if-match:` in the workflow frontmatter if this skip was unexpected.");
       return;
     }
 
diff --git a/actions/setup/js/check_skip_if_no_match.cjs b/actions/setup/js/check_skip_if_no_match.cjs
index 8d089068322..b3edfef7803 100644
--- a/actions/setup/js/check_skip_if_no_match.cjs
+++ b/actions/setup/js/check_skip_if_no_match.cjs
@@ -4,6 +4,7 @@
 const { getErrorMessage } = require("./error_helpers.cjs");
 const { ERR_API, ERR_CONFIG } = require("./error_codes.cjs");
 const { buildSearchQuery } = require("./check_skip_if_helpers.cjs");
+const { writeDenialSummary } = require("./pre_activation_summary.cjs");
 
 async function main() {
   const { GH_AW_SKIP_QUERY: skipQuery, GH_AW_WORKFLOW_NAME: workflowName, GH_AW_SKIP_MIN_MATCHES: minMatchesStr = "1", GH_AW_SKIP_SCOPE: skipScope } = process.env;
@@ -42,6 +43,7 @@ async function main() {
     if (totalCount < minMatches) {
       core.warning(`🔍 Skip condition matched (${totalCount} items found, minimum required: ${minMatches}). Workflow execution will be prevented by activation job.`);
       core.setOutput("skip_no_match_check_ok", "false");
+      await writeDenialSummary(`Skip-if-no-match query returned too few results: ${totalCount} item(s) found (minimum required: ${minMatches}).`, "Update `on.skip-if-no-match:` in the workflow frontmatter if this skip was unexpected.");
       return;
     }
 
diff --git a/actions/setup/js/check_skip_if_no_match.test.cjs b/actions/setup/js/check_skip_if_no_match.test.cjs
index 8d89d7bfbe6..5642a48f17a 100644
--- a/actions/setup/js/check_skip_if_no_match.test.cjs
+++ b/actions/setup/js/check_skip_if_no_match.test.cjs
@@ -19,6 +19,10 @@ describe("check_skip_if_no_match", () => {
       warnings: [],
       errors: [],
       outputs: {},
+      summary: {
+        addRaw: () => mockCore.summary,
+        write: async () => {},
+      },
     };
 
     mockCore.info = msg => {
diff --git a/actions/setup/js/check_skip_roles.cjs b/actions/setup/js/check_skip_roles.cjs
index d62c8b2377a..78256087b27 100644
--- a/actions/setup/js/check_skip_roles.cjs
+++ b/actions/setup/js/check_skip_roles.cjs
@@ -2,6 +2,7 @@
 /// <reference types="@actions/github-script" />
 
 const { checkRepositoryPermission } = require("./check_permissions_utils.cjs");
+const { writeDenialSummary } = require("./pre_activation_summary.cjs");
 
 /**
  * Check if the workflow should be skipped based on user's role
@@ -44,11 +45,13 @@ async function main() {
 
   if (result.authorized) {
     // User has one of the skip-roles, skip the workflow
+    const errorMessage = `Workflow skipped: User '${actor}' has role '${result.permission}' which is in skip-roles: [${skipRoles.join(", ")}]`;
     core.info(`❌ User '${actor}' has role '${result.permission}' which is in skip-roles [${skipRoles.join(", ")}]. Workflow will be skipped.`);
     core.setOutput("skip_roles_ok", "false");
     core.setOutput("result", "skipped");
     core.setOutput("user_permission", result.permission);
-    core.setOutput("error_message", `Workflow skipped: User '${actor}' has role '${result.permission}' which is in skip-roles: [${skipRoles.join(", ")}]`);
+    core.setOutput("error_message", errorMessage);
+    await writeDenialSummary(errorMessage, "Update `on.skip-roles:` in the workflow frontmatter to change which roles are excluded.");
   } else {
     // User does NOT have any of the skip-roles, allow workflow to proceed
     core.info(`✅ User '${actor}' has role '${result.permission}' which is NOT in skip-roles [${skipRoles.join(", ")}]. Workflow will proceed.`);
diff --git a/actions/setup/js/check_skip_roles.test.cjs b/actions/setup/js/check_skip_roles.test.cjs
index d7911e67239..4453890f499 100644
--- a/actions/setup/js/check_skip_roles.test.cjs
+++ b/actions/setup/js/check_skip_roles.test.cjs
@@ -84,6 +84,13 @@ describe("check_skip_roles.cjs", () => {
         utilsFunction(mockCore, mockGithub, mockContext, process, mockModule, moduleExports, mockRequire);
         return mockModule.exports;
       }
+      if (modulePath === "./pre_activation_summary.cjs") {
+        return {
+          writeDenialSummary: async (reason, remediation) => {
+            await mockCore.summary.addRaw(`${reason}\n${remediation}`).write();
+          },
+        };
+      }
       throw new Error(`Module not found: ${modulePath}`);
     };
 
diff --git a/actions/setup/js/check_stop_time.cjs b/actions/setup/js/check_stop_time.cjs
index 6addb4c2162..fc3ca7304ba 100644
--- a/actions/setup/js/check_stop_time.cjs
+++ b/actions/setup/js/check_stop_time.cjs
@@ -2,6 +2,7 @@
 /// <reference types="@actions/github-script" />
 
 const { ERR_CONFIG, ERR_VALIDATION } = require("./error_codes.cjs");
+const { writeDenialSummary } = require("./pre_activation_summary.cjs");
 async function main() {
   const stopTime = process.env.GH_AW_STOP_TIME;
   const workflowName = process.env.GH_AW_WORKFLOW_NAME;
@@ -33,6 +34,7 @@ async function main() {
   if (currentTime >= stopTimeDate) {
     core.warning(`⏰ Stop time reached. Workflow execution will be prevented by activation job.`);
     core.setOutput("stop_time_ok", "false");
+    await writeDenialSummary(`Workflow '${workflowName}' has passed its configured stop-time (${stopTimeDate.toISOString()}).`, "Update or remove `on.stop-after:` in the workflow frontmatter to extend the active window.");
     return;
   }
 
diff --git a/actions/setup/js/pre_activation_summary.cjs b/actions/setup/js/pre_activation_summary.cjs
new file mode 100644
index 00000000000..951940b2b56
--- /dev/null
+++ b/actions/setup/js/pre_activation_summary.cjs
@@ -0,0 +1,38 @@
+// @ts-check
+/// <reference types="@actions/github-script" />
+
+const path = require("path");
+const { renderTemplateFromFile } = require("./messages_core.cjs");
+
+/**
+ * Writes a pre-activation skip denial summary to the GitHub Actions job summary.
+ * Uses the pre_activation_skip.md template from the prompts directory when available,
+ * falling back to a hardcoded format when the template cannot be loaded (e.g. in tests).
+ *
+ * @param {string} reason - The denial reason message
+ * @param {string} remediation - Remediation hint for the operator
+ */
+async function writeDenialSummary(reason, remediation) {
+  let content;
+
+  const runnerTemp = process.env.RUNNER_TEMP;
+  if (runnerTemp) {
+    const templatePath = path.join(runnerTemp, "gh-aw", "prompts", "pre_activation_skip.md");
+    try {
+      content = renderTemplateFromFile(templatePath, { reason, remediation });
+    } catch (err) {
+      // Log unexpected errors but still fall through to the hardcoded fallback
+      if (err && typeof err === "object" && "code" in err && err.code !== "ENOENT") {
+        core.warning(`pre_activation_summary: could not read template ${templatePath}: ${err instanceof Error ? err.message : String(err)}`);
+      }
+    }
+  }
+
+  if (!content) {
+    content = `## ⏭️ Workflow Activation Skipped\n\n> ${reason}\n\n**Remediation:** ${remediation}\n\n---\n_See the \`pre_activation\` job log for full details._`;
+  }
+
+  await core.summary.addRaw(content).write();
+}
+
+module.exports = { writeDenialSummary };
diff --git a/actions/setup/js/pre_activation_summary.test.cjs b/actions/setup/js/pre_activation_summary.test.cjs
new file mode 100644
index 00000000000..f751fc329a9
--- /dev/null
+++ b/actions/setup/js/pre_activation_summary.test.cjs
@@ -0,0 +1,85 @@
+// @ts-check
+import { describe, it, expect, beforeEach, afterEach, vi } from "vitest";
+import fs from "fs";
+import os from "os";
+import path from "path";
+
+describe("pre_activation_summary.cjs", () => {
+  let mockCore;
+  let originalRunnerTemp;
+
+  beforeEach(() => {
+    mockCore = {
+      info: vi.fn(),
+      warning: vi.fn(),
+      summary: {
+        addRaw: vi.fn().mockReturnThis(),
+        write: vi.fn().mockResolvedValue(undefined),
+      },
+    };
+    global.core = mockCore;
+    originalRunnerTemp = process.env.RUNNER_TEMP;
+    vi.resetModules();
+  });
+
+  afterEach(() => {
+    if (originalRunnerTemp !== undefined) {
+      process.env.RUNNER_TEMP = originalRunnerTemp;
+    } else {
+      delete process.env.RUNNER_TEMP;
+    }
+    delete global.core;
+    vi.clearAllMocks();
+  });
+
+  describe("writeDenialSummary", () => {
+    it("uses the markdown template when template file exists", async () => {
+      const tmpDir = fs.mkdtempSync(path.join(os.tmpdir(), "gh-aw-test-"));
+      const promptsDir = path.join(tmpDir, "gh-aw", "prompts");
+      fs.mkdirSync(promptsDir, { recursive: true });
+      fs.writeFileSync(path.join(promptsDir, "pre_activation_skip.md"), "## Skipped\n\n> {reason}\n\n**Fix:** {remediation}\n", "utf8");
+
+      process.env.RUNNER_TEMP = tmpDir;
+
+      try {
+        const { writeDenialSummary } = await import("./pre_activation_summary.cjs");
+        await writeDenialSummary("Denied: insufficient perms", "Update frontmatter roles");
+
+        expect(mockCore.summary.addRaw).toHaveBeenCalledWith("## Skipped\n\n> Denied: insufficient perms\n\n**Fix:** Update frontmatter roles\n");
+        expect(mockCore.summary.write).toHaveBeenCalled();
+      } finally {
+        fs.rmSync(tmpDir, { recursive: true, force: true });
+      }
+    });
+
+    it("falls back to hardcoded format when RUNNER_TEMP is not set", async () => {
+      delete process.env.RUNNER_TEMP;
+
+      const { writeDenialSummary } = await import("./pre_activation_summary.cjs");
+      await writeDenialSummary("Bot not authorized", "Add bot to on.bots:");
+
+      const rawCall = mockCore.summary.addRaw.mock.calls[0][0];
+      expect(rawCall).toContain("Bot not authorized");
+      expect(rawCall).toContain("Add bot to on.bots:");
+      expect(mockCore.summary.write).toHaveBeenCalled();
+    });
+
+    it("falls back to hardcoded format when template file does not exist", async () => {
+      const tmpDir = fs.mkdtempSync(path.join(os.tmpdir(), "gh-aw-test-"));
+      process.env.RUNNER_TEMP = tmpDir;
+      // No template file created
+
+      try {
+        const { writeDenialSummary } = await import("./pre_activation_summary.cjs");
+        await writeDenialSummary("Stop time exceeded", "Update on.stop-after:");
+
+        const rawCall = mockCore.summary.addRaw.mock.calls[0][0];
+        expect(rawCall).toContain("Stop time exceeded");
+        expect(rawCall).toContain("Update on.stop-after:");
+        expect(mockCore.summary.write).toHaveBeenCalled();
+      } finally {
+        fs.rmSync(tmpDir, { recursive: true, force: true });
+      }
+    });
+  });
+});
diff --git a/actions/setup/md/pre_activation_skip.md b/actions/setup/md/pre_activation_skip.md
new file mode 100644
index 00000000000..7a7e4a1c863
--- /dev/null
+++ b/actions/setup/md/pre_activation_skip.md
@@ -0,0 +1,9 @@
+## ⏭️ Workflow Activation Skipped
+
+> {reason}
+
+**Remediation:** {remediation}
+
+---
+
+_See the `pre_activation` job log for full details._
diff --git a/pkg/workflow/compiler_pre_activation_job.go b/pkg/workflow/compiler_pre_activation_job.go
index 80d1cf8fce9..51069ef63bb 100644
--- a/pkg/workflow/compiler_pre_activation_job.go
+++ b/pkg/workflow/compiler_pre_activation_job.go
@@ -439,6 +439,8 @@ func (c *Compiler) buildPreActivationJob(data *WorkflowData, needsPermissionChec
 	return job, nil
 }
 
+// generateReportSkipStep generates the "Report skip reason" step for the pre-activation job.
+// The step runs with if: always() and writes skip reasons to the GitHub Actions job summary
 // extractPreActivationCustomFields extracts custom steps and outputs from jobs.pre-activation field in frontmatter.
 // It validates that only steps and outputs fields are present, and errors on any other fields.
 // If both jobs.pre-activation and jobs.pre_activation are defined, imports from both.