diff --git a/cartridges/domains/ci-cd/cicd-squabbler-mcp/README.adoc b/cartridges/domains/ci-cd/cicd-squabbler-mcp/README.adoc
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+// SPDX-License-Identifier: CC-BY-SA-4.0
+= cicd-squabbler-mcp
+
+CI/CD gate-fighter cartridge — makes
+https://github.com/hyperpolymath/cicd-squabbler[cicd-squabbler] summonable
+through boj-server. Operationalises estate Doctrine #5: *squabble, don't
+bypass* — a gate is won only by legitimately satisfying its required checks,
+never by admin-override or dropping a context (SPARK-proved invariant in the
+upstream repo).
+
+== Tools
+
+|===
+|Tool |Purpose
+
+|`squabble_fight`
+|Plan a fight for a stuck gate: classify every unsatisfied required check as
+*self-win* (CI-config lane) / *escalate-to-expert* (hypatia / fleet / proof /
+security specialist groups) / *assign-owner* (upstream reusable or
+misconfigured gate), plus a structural scan (path-filter traps, missing
+well-known files, banned licence labels). Returns the `Outcome`/`Report`
+evidence manifest — fail-closed, no silent skip.
+
+|`squabble_diagnose`
+|Pure-engine diagnosis: gate state (`blocked`/`red`/`green`) plus one
+conservative legitimate move per unsatisfied check. No filesystem context,
+no mutation.
+|===
+
+== Backend
+
+Proxies to the `squabble-app` loopback HTTP backend
+(`SQUABBLE_BACKEND_URL`, default `http://127.0.0.1:7741`) — the same shared
+planner the `squabble` CLI uses. Start it with:
+
+[source,shell]
+----
+cargo run -p squabble-app   # in hyperpolymath/cicd-squabbler
+----
+
+No `ffi` block on purpose: this cartridge takes the `mod.js` (Deno gateway)
+dispatch path. The gateway only proxies; the sandbox has no subprocess
+capability, and the gate invariant lives in `squabble-core` upstream.
+
+== Example
+
+[source,shell]
+----
+curl -s -X POST http://localhost:7700/cartridge/cicd-squabbler-mcp/invoke \
+  -H 'Content-Type: application/json' \
+  -d '{"tool":"squabble_fight","arguments":{"slug":"hyperpolymath/ipv6-only","gate":{"checks":[{"required_context":"lint-shell","run":"failed"}]}}}'
+----
diff --git a/cartridges/domains/ci-cd/cicd-squabbler-mcp/cartridge.json b/cartridges/domains/ci-cd/cicd-squabbler-mcp/cartridge.json
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+++ b/cartridges/domains/ci-cd/cicd-squabbler-mcp/cartridge.json
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+{
+  "$schema": "https://hyperpolymath.dev/standards/cartridges/cartridge-v1.json",
+  "spdx": "MPL-2.0",
+  "copyright": "Copyright (c) 2026 Jonathan D.A. Jewell (hyperpolymath) <j.d.a.jewell@open.ac.uk>",
+  "name": "cicd-squabbler-mcp",
+  "version": "0.1.0",
+  "description": "cicd-squabbler — the CI/CD gate fighter (squabble != bypass). Diagnoses a stuck branch-protection gate and plans legitimate moves: self-win CI-config fixes, escalations to specialist experts, and owner assignments. Proxies to the squabble-app loopback backend.",
+  "domain": "ci",
+  "category": "domain",
+  "tier": "Ayo",
+  "protocols": [
+    "MCP",
+    "REST"
+  ],
+  "auth": {
+    "method": "none",
+    "env_var": null,
+    "credential_source": null
+  },
+  "api": {
+    "base_url": "local://cicd-squabbler-mcp",
+    "content_type": "application/json"
+  },
+  "tools": [
+    {
+      "name": "squabble_fight",
+      "description": "Plan a fight for a stuck gate: classify every unsatisfied required check as self-win (CI-config lane) | escalate-to-expert (hypatia/fleet/proof/security) | assign-owner (upstream or misconfigured), plus a structural scan (path-filter traps, missing well-known files, banned licence labels). Returns the Outcome/Report evidence manifest. Never bypasses: no admin-override, no dropped contexts.",
+      "inputSchema": {
+        "type": "object",
+        "properties": {
+          "slug": {
+            "type": "string",
+            "description": "Repository as owner/repo (used for upstream-owner attribution)"
+          },
+          "gate": {
+            "type": "object",
+            "description": "The gate: {checks:[{required_context, run: missing|pending|failed|passed}]} — from `squabble fetch` or the caller's own check-run data"
+          },
+          "repo_root": {
+            "type": "string",
+            "description": "Optional path to a local checkout; enables the a2ml ecosystem-context reader and workflow ground-truthing. Fail-safe when absent."
+          }
+        },
+        "required": [
+          "slug",
+          "gate"
+        ]
+      }
+    },
+    {
+      "name": "squabble_diagnose",
+      "description": "Pure-engine diagnosis of a gate: current state (blocked|red|green) plus one conservative legitimate move per unsatisfied required check. No filesystem context; no mutation.",
+      "inputSchema": {
+        "type": "object",
+        "properties": {
+          "checks": {
+            "type": "array",
+            "description": "Required checks with realised runs: [{required_context: string, run: missing|pending|failed|passed}]",
+            "items": {
+              "type": "object"
+            }
+          }
+        },
+        "required": [
+          "checks"
+        ]
+      }
+    }
+  ]
+}
diff --git a/cartridges/domains/ci-cd/cicd-squabbler-mcp/mod.js b/cartridges/domains/ci-cd/cicd-squabbler-mcp/mod.js
new file mode 100644
index 0000000..c959e79
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+++ b/cartridges/domains/ci-cd/cicd-squabbler-mcp/mod.js
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+// SPDX-License-Identifier: MPL-2.0
+// Copyright (c) 2026 Jonathan D.A. Jewell (hyperpolymath) <j.d.a.jewell@open.ac.uk>
+//
+// cicd-squabbler-mcp/mod.js — CI/CD gate fighter gateway (squabble != bypass)
+//
+// Delegates to the squabble-app loopback backend at http://127.0.0.1:7741
+// (override with SQUABBLE_BACKEND_URL). The backend is the same shared
+// planner the `squabble` CLI uses; this gateway only proxies — the cartridge
+// sandbox has no subprocess capability, and the squabbler's gate invariant
+// (green only by satisfying required checks, never by weakening them) lives
+// in squabble-core, not here.
+
+const BASE_URL = Deno.env.get("SQUABBLE_BACKEND_URL") ?? "http://127.0.0.1:7741";
+const TIMEOUT_MS = 15_000;
+
+async function post(path, payload) {
+  const ctrl = new AbortController();
+  const t = setTimeout(() => ctrl.abort(), TIMEOUT_MS);
+  try {
+    const r = await fetch(`${BASE_URL}${path}`, {
+      method: "POST",
+      headers: { "Content-Type": "application/json" },
+      body: JSON.stringify(payload),
+      signal: ctrl.signal,
+    });
+    const data = await r.json().catch(() => ({ success: false, error: "non-JSON response" }));
+    return { status: r.status, data };
+  } catch (e) {
+    if (e.name === "AbortError") return { status: 504, data: { success: false, error: "cicd-squabbler-mcp backend timed out" } };
+    return { status: 503, data: { success: false, error: `cicd-squabbler-mcp backend unavailable: ${e.message}` } };
+  } finally { clearTimeout(t); }
+}
+
+export async function handleTool(toolName, args) {
+  switch (toolName) {
+    case "squabble_fight": {
+      const { slug, gate } = args ?? {};
+      if (!slug || !gate) {
+        return { status: 400, data: { error: "slug and gate are required" } };
+      }
+      // Pass through exactly what the backend's FightRequest expects.
+      const payload = { slug, gate };
+      if (args.repo_root) payload.repo_root = args.repo_root;
+      return post("/api/v1/fight", payload);
+    }
+    case "squabble_diagnose": {
+      const { checks } = args ?? {};
+      if (!Array.isArray(checks)) {
+        return { status: 400, data: { error: "checks (array) is required" } };
+      }
+      // The backend takes the Gate object directly.
+      return post("/api/v1/diagnose", { checks });
+    }
+    default:
+      return { status: 404, data: { error: `Unknown tool: ${toolName}` } };
+  }
+}