diff --git a/tanstack-migrator/server/db/catalog.ts b/tanstack-migrator/server/db/catalog.ts
index 7fb57eb0..1f67e976 100644
--- a/tanstack-migrator/server/db/catalog.ts
+++ b/tanstack-migrator/server/db/catalog.ts
@@ -1,11 +1,13 @@
 /**
- * Read-only client for the decocms platform `sites` catalog (a DIFFERENT
- * Supabase project than the MCP's own sitemig_* DB).
+ * Client for the decocms platform `sites` catalog (a DIFFERENT Supabase project
+ * than the MCP's own sitemig_* DB).
  *
- * Powers the register modal's repo autocomplete: search by site name and
- * pre-fill both the GitHub repo and the production URL — no GitHub API calls,
- * so no rate limit. Opt-in: only active when DECOCMS_SUPABASE_URL +
- * DECOCMS_SUPABASE_KEY are set. This module ONLY ever runs SELECTs.
+ * Mostly reads (register-modal repo autocomplete: search by site name to
+ * pre-fill the GitHub repo + production URL, no GitHub API calls / no rate
+ * limit). The ONE write is setSitePlatform — it flags the migrated -tanstack
+ * repo as a Cloudflare Workers Builds site so the Fresh/Deno k8s deployer stops
+ * watching it. Opt-in: active only when DECOCMS_SUPABASE_URL +
+ * DECOCMS_SUPABASE_KEY (a service-role key) are set.
  */
 
 import { createClient, type SupabaseClient } from "@supabase/supabase-js";
@@ -150,3 +152,58 @@ export async function catalogByNames(
   }
   return map;
 }
+
+export const CFWORKERS_BUILDS_PLATFORM = "cfworkers-builds";
+
+/**
+ * Flag a repo's catalog row with `metadata.platform` (default
+ * "cfworkers-builds") so the deco Fresh/Deno k8s deployer stops watching the
+ * migrated -tanstack repo (it keeps trying to deploy it and leaves a mess).
+ *
+ * Read-merge-write on the single row matched by github_repo_url — never clobbers
+ * other metadata keys. Fully guarded + best-effort: returns {ok:false, reason}
+ * instead of throwing (catalog not configured / row not indexed yet / RLS), so
+ * it can never block a migration. Idempotent.
+ */
+export async function setSitePlatform(
+  repoFull: string,
+  platform: string = CFWORKERS_BUILDS_PLATFORM,
+): Promise<{ ok: boolean; reason: string }> {
+  const client = getCatalogClient();
+  if (!client) return { ok: false, reason: "catalog not configured" };
+  const repo = repoFull.trim().replace(/\.git$/, "");
+  if (!repo.includes("/"))
+    return { ok: false, reason: `invalid repo ${repoFull}` };
+
+  try {
+    const { data, error } = await client
+      .from("sites")
+      .select("github_repo_url, metadata")
+      .ilike("github_repo_url", `%${repo}%`)
+      .limit(5);
+    if (error) return { ok: false, reason: error.message };
+    const rows = (data ?? []) as Array<{
+      github_repo_url: string | null;
+      metadata: Record<string, unknown> | null;
+    }>;
+    // exact owner/repo match (ilike is fuzzy — avoid touching a similarly-named repo)
+    const row = rows.find((r) => toOwnerRepo(r.github_repo_url) === repo);
+    if (!row) return { ok: false, reason: "repo not in catalog yet" };
+
+    const meta =
+      row.metadata && typeof row.metadata === "object" ? row.metadata : {};
+    if (meta.platform === platform) return { ok: true, reason: "already set" };
+
+    const { error: upErr } = await client
+      .from("sites")
+      .update({ metadata: { ...meta, platform } })
+      .eq("github_repo_url", row.github_repo_url);
+    if (upErr) return { ok: false, reason: upErr.message };
+    return { ok: true, reason: "updated" };
+  } catch (err) {
+    return {
+      ok: false,
+      reason: err instanceof Error ? err.message : String(err),
+    };
+  }
+}
diff --git a/tanstack-migrator/server/engine/phases/creating-repo.ts b/tanstack-migrator/server/engine/phases/creating-repo.ts
index cad82b80..aca4f0a7 100644
--- a/tanstack-migrator/server/engine/phases/creating-repo.ts
+++ b/tanstack-migrator/server/engine/phases/creating-repo.ts
@@ -3,6 +3,7 @@
  * durable GitHub grant used by the sandbox for pushes.
  */
 
+import { setSitePlatform } from "../../db/catalog.ts";
 import { addEvent } from "../../db/events.ts";
 import type { SiteRow } from "../../db/types.ts";
 import { updateSite } from "../../db/sites.ts";
@@ -59,6 +60,14 @@ export async function creatingRepo(
   }
   await addEvent(site.id, `Repo ${targetRepo} ensured on GitHub`);
 
+  // Flag it as a CF Workers Builds site so the Fresh/Deno k8s deployer ignores
+  // it. Best-effort + early — the catalog row often isn't indexed yet at this
+  // point (the deploy phase re-asserts it once it is).
+  const plat = await setSitePlatform(targetRepo);
+  if (plat.ok && plat.reason === "updated") {
+    await addEvent(site.id, `Catalog: ${targetRepo} marked cfworkers-builds`);
+  }
+
   // main must exist (repos are created empty) — it's the PR base — and the
   // work branch must exist BEFORE SANDBOX_START: sandbox clone + decopilot
   // threads are pinned to it.
diff --git a/tanstack-migrator/server/engine/phases/deploying-cf.ts b/tanstack-migrator/server/engine/phases/deploying-cf.ts
index 88b8e5bc..33c17a15 100644
--- a/tanstack-migrator/server/engine/phases/deploying-cf.ts
+++ b/tanstack-migrator/server/engine/phases/deploying-cf.ts
@@ -16,6 +16,7 @@ import { createRun, finishRun } from "../../db/runs.ts";
 import { getSite, updateSite } from "../../db/sites.ts";
 import type { SiteRow } from "../../db/types.ts";
 import { manualCfInstructions } from "../../lib/cloudflare.ts";
+import { setSitePlatform } from "../../db/catalog.ts";
 import { parseRepo } from "../../lib/github.ts";
 import type { WorkerCtx } from "../../lib/mesh.ts";
 import { previewRendersRealHtml } from "../../lib/preview.ts";
@@ -150,6 +151,27 @@ export async function deployingCf(
         );
       }
 
+      // Now that the repo is pushed + indexed, flag it as CF Workers Builds so
+      // the Fresh/Deno k8s deployer stops watching it (best-effort, never blocks).
+      const plat = await setSitePlatform(current.target_repo!);
+      if (plat.ok && plat.reason === "updated") {
+        await addEvent(
+          site.id,
+          `Catalog: ${current.target_repo} marked cfworkers-builds — Fresh/Deno bot will ignore it`,
+        );
+      } else if (
+        !plat.ok &&
+        !["catalog not configured", "repo not in catalog yet"].includes(
+          plat.reason,
+        )
+      ) {
+        await addEvent(
+          site.id,
+          `Catalog platform flag not set (${plat.reason.slice(0, 120)})`,
+          "warn",
+        );
+      }
+
       await advanceAfterDeploy(current, {
         cf_project_name: workerName,
         cf_deploy_url: deployUrl,
diff --git a/tanstack-migrator/server/tools/index.ts b/tanstack-migrator/server/tools/index.ts
index ed386067..34d0c5bf 100644
--- a/tanstack-migrator/server/tools/index.ts
+++ b/tanstack-migrator/server/tools/index.ts
@@ -25,6 +25,7 @@ import {
   createSiteResumeTool,
   createSiteResetTool,
   createSiteRetryTool,
+  createSiteSetPlatformTool,
   createSiteTerminalTool,
 } from "./sites.ts";
 import { createSyncDecofileInstallTool } from "./sync.ts";
@@ -41,6 +42,7 @@ export const tools = [
   createSiteResumeTool,
   createSiteRetryTool,
   createSiteResetTool,
+  createSiteSetPlatformTool,
   createSiteEnqueueTool,
   createSiteReorderTool,
   createSiteMarkDoneTool,
diff --git a/tanstack-migrator/server/tools/sites.ts b/tanstack-migrator/server/tools/sites.ts
index 948c804f..1c7a2b24 100644
--- a/tanstack-migrator/server/tools/sites.ts
+++ b/tanstack-migrator/server/tools/sites.ts
@@ -4,8 +4,10 @@ import { createTool } from "@decocms/runtime/tools";
 import { z } from "zod";
 import {
   catalogByNames,
+  CFWORKERS_BUILDS_PLATFORM,
   isCatalogConfigured,
   searchSiteCatalog,
+  setSitePlatform,
 } from "../db/catalog.ts";
 import { loadConnection, saveConnection } from "../db/connections.ts";
 import { getCostSnapshot, refreshCostSnapshotIfStale } from "../db/cost.ts";
@@ -438,6 +440,58 @@ export const createSiteResetTool = (env: Env) =>
     },
   });
 
+export const createSiteSetPlatformTool = (env: Env) =>
+  createTool({
+    id: "SITE_SET_PLATFORM",
+    description:
+      "Flag the migrated -tanstack repo in the decocms catalog with metadata.platform (default 'cfworkers-builds') so the deco Fresh/Deno k8s deployer stops watching it (it keeps trying to deploy the -tanstack repo and leaves a broken deployment). Use it on existing -tanstack sites that the bot is fighting. New migrations set this automatically at repo creation + deploy. Pass a siteId (uses its -tanstack repo) or repo (owner/name) directly.",
+    inputSchema: z.object({
+      siteId: z
+        .string()
+        .optional()
+        .describe("Migration site id (uses its -tanstack repo)."),
+      repo: z
+        .string()
+        .optional()
+        .describe('Target -tanstack repo "owner/name" (overrides the site).'),
+      platform: z
+        .string()
+        .optional()
+        .describe(`Platform value (default ${CFWORKERS_BUILDS_PLATFORM}).`),
+    }),
+    outputSchema: z.object({
+      ok: z.boolean(),
+      repo: z.string(),
+      platform: z.string(),
+      reason: z.string(),
+    }),
+    execute: async ({ context }) => {
+      requireConnectionId(env);
+      if (!isCatalogConfigured()) {
+        throw new Error(
+          "Catalog not configured (DECOCMS_SUPABASE_URL/KEY missing) — cannot set the platform flag.",
+        );
+      }
+      const site = context.siteId ? await getSite(context.siteId) : null;
+      if (context.siteId && !site) throw new Error("Site not found");
+      const repo = (context.repo ?? site?.target_repo ?? "")
+        .trim()
+        .replace(/^https?:\/\/github\.com\//, "")
+        .replace(/\.git$/, "");
+      if (!repo) {
+        throw new Error(
+          "No target repo — pass repo, or a siteId whose migration has a -tanstack repo.",
+        );
+      }
+      const platform = context.platform ?? CFWORKERS_BUILDS_PLATFORM;
+      const result = await setSitePlatform(repo, platform);
+      if (site && result.ok && result.reason === "updated") {
+        await addEvent(site.id, `Catalog: ${repo} marked ${platform}`);
+      }
+      return { ok: result.ok, repo, platform, reason: result.reason };
+    },
+  });
+
 export const createSiteMarkDoneTool = (env: Env) =>
   createTool({
     id: "SITE_MARK_DONE",