diff --git a/.changeset/quiet-moons-wait.md b/.changeset/quiet-moons-wait.md
new file mode 100644
index 0000000..09fe7f4
--- /dev/null
+++ b/.changeset/quiet-moons-wait.md
@@ -0,0 +1,5 @@
+---
+'@arcasilesgroup/ai-shell': patch
+---
+
+Pin @nexssp/os to exactly 2.0.36. The caret range let npm resolve 2.1.x for fresh installs, and those tarballs are missing legacy.mjs while their exports map points at it: every `ai` invocation died with ERR_MODULE_NOT_FOUND. Verified against the published 0.1.1 from the registry.
diff --git a/package-lock.json b/package-lock.json
index 64b5521..7015ce0 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -11,7 +11,7 @@
         "@clack/core": "1.4.3",
         "@clack/prompts": "1.7.0",
         "@dqbd/tiktoken": "^1.0.22",
-        "@nexssp/os": "^2.0.36",
+        "@nexssp/os": "2.0.36",
         "axios": "^1.3.5",
         "cleye": "^2.6.0",
         "clipboardy": "^2.3.0",
diff --git a/package.json b/package.json
index f8f79dd..e9f1d8f 100644
--- a/package.json
+++ b/package.json
@@ -10,7 +10,7 @@
     "@clack/core": "1.4.3",
     "@clack/prompts": "1.7.0",
     "@dqbd/tiktoken": "^1.0.22",
-    "@nexssp/os": "^2.0.36",
+    "@nexssp/os": "2.0.36",
     "axios": "^1.3.5",
     "cleye": "^2.6.0",
     "clipboardy": "^2.3.0",