diff --git a/bundle/.gnkit/lib/hook-helpers.mjs b/bundle/.gnkit/lib/hook-helpers.mjs
index 55cf18a..9230b12 100644
--- a/bundle/.gnkit/lib/hook-helpers.mjs
+++ b/bundle/.gnkit/lib/hook-helpers.mjs
@@ -93,16 +93,17 @@ export function loadHookConfig(root) {
     // graph query tools require a fast incremental refresh. 0 disables the drift gate.
     driftRefreshThreshold: 3,
     // TASK-CORE compaction migration: nudge the agent to refresh its task-core once context
-    // reaches contextPressureThreshold of contextWindowTokens. Set contextWindowTokens to your
-    // model's window (200k default; 1M-context sessions → 1000000). 0 threshold disables.
+    // reaches contextPressureThreshold of contextWindowTokens. The window is model-specific, so
+    // prefer the per-machine env var GITNEXUS_CONTEXT_WINDOW=1000000 (wins over this file) rather
+    // than committing 1000000 to a shared repo where teammates run a 200k model. 0 threshold disables.
     contextWindowTokens: 200000,
     contextPressureThreshold: 0.9,
   };
 
   const cfgPath = path.join(root, CONFIG_FILE);
-  if (!fs.existsSync(cfgPath)) return cfg;
 
   try {
+    // Missing file → readFileSync throws → caught below → defaults kept, then env override runs.
     const file = JSON.parse(fs.readFileSync(cfgPath, "utf8"));
     if (file.mode) cfg.mode = file.mode === "guide" ? "guide" : "enforce";
     if (typeof file.readLineThreshold === "number")
@@ -125,6 +126,12 @@ export function loadHookConfig(root) {
     /* keep defaults */
   }
 
+  // Per-machine env override wins over the (team-shared) config file. The context window is
+  // model-specific — a 1M-context session and a teammate's 200k model can't share one committed
+  // value — so set GITNEXUS_CONTEXT_WINDOW=1000000 in your shell rather than in gitnexus-hooks.json.
+  const envWindow = Number(process.env.GITNEXUS_CONTEXT_WINDOW);
+  if (Number.isFinite(envWindow) && envWindow > 0) cfg.contextWindowTokens = envWindow;
+
   return cfg;
 }
 
diff --git a/lib/kit.test.mjs b/lib/kit.test.mjs
index 8227c3f..cd632f4 100644
--- a/lib/kit.test.mjs
+++ b/lib/kit.test.mjs
@@ -1033,6 +1033,47 @@ describe("gitnexus-agent-kit", () => {
     fs.rmSync(tmp, { recursive: true, force: true });
   });
 
+  it("GITNEXUS_CONTEXT_WINDOW env overrides the shared config file (per-machine window)", async () => {
+    const helpers = await import(
+      new URL("../bundle/.gnkit/lib/hook-helpers.mjs", import.meta.url).href
+    );
+    const prev = process.env.GITNEXUS_CONTEXT_WINDOW;
+    try {
+      const empty = fs.mkdtempSync(path.join(os.tmpdir(), "gn-win-"));
+
+      // No file + no env → default window.
+      delete process.env.GITNEXUS_CONTEXT_WINDOW;
+      assert.equal(helpers.loadHookConfig(empty).contextWindowTokens, 200000);
+
+      // No file + env → env applies (guards against the no-config early-return path).
+      process.env.GITNEXUS_CONTEXT_WINDOW = "1000000";
+      assert.equal(helpers.loadHookConfig(empty).contextWindowTokens, 1000000);
+
+      // File says 200k, env says 1M → env wins (model-specific, not committed to a shared repo).
+      const repo = fs.mkdtempSync(path.join(os.tmpdir(), "gn-win2-"));
+      fs.mkdirSync(path.join(repo, ".gnkit"), { recursive: true });
+      fs.writeFileSync(
+        path.join(repo, ".gnkit/gitnexus-hooks.json"),
+        JSON.stringify({ contextWindowTokens: 200000 }),
+      );
+      assert.equal(helpers.loadHookConfig(repo).contextWindowTokens, 1000000);
+
+      // No env → the file value stands.
+      delete process.env.GITNEXUS_CONTEXT_WINDOW;
+      assert.equal(helpers.loadHookConfig(repo).contextWindowTokens, 200000);
+
+      // Garbage env is ignored (no NaN/0 window).
+      process.env.GITNEXUS_CONTEXT_WINDOW = "banana";
+      assert.equal(helpers.loadHookConfig(repo).contextWindowTokens, 200000);
+
+      fs.rmSync(empty, { recursive: true, force: true });
+      fs.rmSync(repo, { recursive: true, force: true });
+    } finally {
+      if (prev === undefined) delete process.env.GITNEXUS_CONTEXT_WINDOW;
+      else process.env.GITNEXUS_CONTEXT_WINDOW = prev;
+    }
+  });
+
   it("cypher field access matches Methods (untyped source node)", async () => {
     const cypher = await import(
       new URL("../bundle/.gnkit/lib/cypher-helpers.mjs", import.meta.url)