fix(md-exports): apply keyword placeholder defaults in generated markdown

___PUBLIC_DSN___ and related ___KEYWORD___ tokens are replaced client-side
by codeKeywords.tsx, so SSR HTML and the generated .md artifacts contain
them verbatim. Adds MD_KEYWORD_DEFAULTS (mirroring DEFAULTS.PROJECT[0] in
codeContext.tsx) and applies them via applyKeywordDefaults() after the
HTML→markdown cache step, so .md files ship with usable example values.

Applied outside the cache to avoid invalidating existing cache entries.

Fixes #18038

Co-authored-by: David Cramer <david@sentry.io>

Author: sentry-junior[bot]

scripts/generate-md-exports.mjs

@@ -29,6 +29,57 @@ import {remove} from 'unist-util-remove';
 
 import {rehypeExpandCodeTabs} from './rehype-expand-code-tabs.mjs';
 
+// Default values for code keyword placeholders (e.g. ___PUBLIC_DSN___) that are
+// normally replaced client-side by codeKeywords.tsx. These must stay in sync with
+// DEFAULTS.PROJECT[0] in src/components/codeContext.tsx.
+// Values must be clearly non-functional so agents and LLMs know they need
+// to be replaced with real project-specific values. Avoid realistic-looking
+// values (e.g. valid DSN shapes) — agents will use them as-is.
+const MD_KEYWORD_DEFAULTS = {
+  DSN: 'https://<key>@<org>.ingest.sentry.io/<project>',
+  PUBLIC_DSN: 'https://<key>@<org>.ingest.sentry.io/<project>',
+  PUBLIC_KEY: '<your-public-key>',
+  SECRET_KEY: '<your-secret-key>',
+  API_URL: 'https://sentry.io/api',
+  PROJECT_ID: '<your-project-id>',
+  PROJECT_SLUG: '<your-project-slug>',
+  ORG_ID: '<your-org-id>',
+  ORG_SLUG: '<your-org-slug>',
+  ORG_INGEST_DOMAIN: '<org>.ingest.sentry.io',
+  JS_SDK_LOADER_HOST: 'js.sentry-cdn.com',
+  MINIDUMP_URL:
+    'https://<org>.ingest.sentry.io/api/<project>/minidump/?sentry_key=<key>',
+  UNREAL_URL: 'https://<org>.ingest.sentry.io/api/<project>/unreal/<key>/',
+  OTLP_URL: 'https://<org>.ingest.sentry.io/api/<project>/integration/otlp',
+  OTLP_TRACES_URL:
+    'https://<org>.ingest.sentry.io/api/<project>/integration/otlp/v1/traces',
+  OTLP_LOGS_URL:
+    'https://<org>.ingest.sentry.io/api/<project>/integration/otlp/v1/logs',
+  VERCEL_LOG_DRAIN_URL:
+    'https://<org>.ingest.sentry.io/api/<project>/integration/vercel/logs/',
+};
+
+/**
+ * Replaces ___KEYWORD___ placeholders in generated markdown with clearly non-functional
+ * placeholder values (e.g. <your-org-slug>) so agents and LLMs know they must be
+ * substituted with real project-specific values before use.
+ *
+ * These tokens are replaced client-side by codeKeywords.tsx at runtime; the SSR HTML
+ * (and therefore the generated markdown) contains them verbatim. Using obviously-fake
+ * values — rather than realistic-looking defaults — prevents agents from silently
+ * treating them as valid configuration.
+ *
+ * Applied after HTML→markdown conversion, outside the cache, so existing cache entries
+ * remain valid.
+ */
+function applyKeywordDefaults(markdown) {
+  let result = markdown;
+  for (const [key, value] of Object.entries(MD_KEYWORD_DEFAULTS)) {
+    result = result.replaceAll(`___${key}___`, value);
+  }
+  return result;
+}
+
 const DOCS_ORIGIN = process.env.NEXT_PUBLIC_DEVELOPER_DOCS
   ? 'https://develop.sentry.dev'
   : 'https://docs.sentry.io';
@@ -1099,10 +1150,12 @@ async function processTaskList({id, tasks, cacheDir, noCache, usedCacheFiles}) {
         cacheMisses.push(relativePath);
       }
 
-      // Keep metadata outside the cache so description-only changes don't invalidate
-      // the expensive HTML → markdown conversion output.
-      // Prepend YAML frontmatter and write to target
-      const output = frontmatter ? formatYamlFrontmatter(frontmatter) + data : data;
+      // Keep these transformations outside the cache so they don't invalidate the
+      // expensive HTML → markdown conversion output:
+      //   - applyKeywordDefaults: replaces ___KEYWORD___ placeholders with defaults
+      //   - formatYamlFrontmatter: prepends YAML metadata
+      const resolved = applyKeywordDefaults(data);
+      const output = frontmatter ? formatYamlFrontmatter(frontmatter) + resolved : resolved;
       await writeFile(targetPath, output, {encoding: 'utf8'});
 
       if (r2Hash !== null && s3Client) {