diff --git a/modules-ir/l1/l1-s3/README.md b/modules-ir/l1/l1-s3/README.md
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+# l1-s3 — S3 bucket primitive
+
+The first real L1 module for the v1.1 spike. Single-purpose,
+substrate-agnostic (the IR type is `aws:s3:bucket`, not a Terraform
+resource type).
+
+## Interface (the IR-typed contract)
+
+See `interface.json`: inputs `bucket_name` + `region` (strings), outputs
+`bucket_arn` (arn) + `bucket_name` (string), NFR `versioning` (bool,
+default true).
+
+## IR → Terraform mapping (performed by the adapter)
+
+The Terraform adapter (`adapters/terraform/adapter.py`) translates this
+L1's IR shape to Terraform:
+
+| IR | Terraform |
+|----|-----------|
+| `resource.type = aws:s3:bucket` | `resource "aws_s3_bucket" "<id>" { ... }` |
+| `resource.inputs.bucket_name` | `bucket = <value>` arg |
+| `resource.inputs.region` | `provider "aws" { region = <value> }` |
+| `resource.outputs.bucket_arn` | `output "bucket_arn" { value = aws_s3_bucket.<id>.arn }` |
+| `resource.outputs.bucket_name` | `output "bucket_name" { value = aws_s3_bucket.<id>.id }` |
+
+The adapter is a thin layer (ARCHITECTURE.md §12.2); it does not own L1
+content — it only translates.
+
+## Spike instance
+
+`spike_instance.json` is a concrete stack instance (with values
+`bucket_name=acdl-spike-bucket`, `region=us-east-1`) that validates
+against `schemas/ir.schema.json`. The adapter consumes this instance
+(not the interface contract) to emit Terraform.
+
+## Versioning (W3.D)
+
+`1.0.0` — interface MAJOR, behavior MINOR, lifecycle PATCH. MAJOR bumps
+require a new registry entry (immutable publication); old entries enter
+a 12-month deprecation window.
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diff --git a/modules-ir/l1/l1-s3/interface.json b/modules-ir/l1/l1-s3/interface.json
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+{
+  "name": "l1-s3",
+  "version": "1.0.0",
+  "kind": "l1",
+  "type": "aws:s3:bucket",
+  "description": "S3 bucket primitive (substrate-agnostic IR type aws:s3:bucket; the Terraform adapter translates to aws_s3_bucket).",
+  "inputs": {
+    "bucket_name": {
+      "type": "string",
+      "description": "Globally-unique S3 bucket name.",
+      "required": true
+    },
+    "region": {
+      "type": "string",
+      "description": "AWS region the bucket is created in.",
+      "required": true
+    }
+  },
+  "outputs": {
+    "bucket_arn": {
+      "type": "arn",
+      "description": "The S3 bucket ARN."
+    },
+    "bucket_name": {
+      "type": "string",
+      "description": "The bucket name (echoes the input)."
+    }
+  },
+  "nfrs": {
+    "versioning": {
+      "type": "boolean",
+      "description": "Enable S3 versioning (default true).",
+      "default": true
+    }
+  }
+}
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diff --git a/modules-ir/l1/l1-s3/spike_instance.json b/modules-ir/l1/l1-s3/spike_instance.json
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+{
+  "version": "1.0.0",
+  "stack": {
+    "name": "l1-s3",
+    "kind": "l1",
+    "depth": 1
+  },
+  "resources": [
+    {
+      "id": "s3",
+      "type": "aws:s3:bucket",
+      "module": "l1-s3@1.0.0",
+      "inputs": {
+        "bucket_name": "acdl-spike-bucket",
+        "region": "us-east-1"
+      },
+      "outputs": {
+        "bucket_arn": {"type": "arn", "description": "The S3 bucket ARN."},
+        "bucket_name": {"type": "string", "description": "The bucket name."}
+      }
+    }
+  ]
+}
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diff --git a/modules-ir/registry.json b/modules-ir/registry.json
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+++ b/modules-ir/registry.json
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+{
+  "l1-s3": {
+    "1.0.0": {
+      "interface": "modules-ir/l1/l1-s3/interface.json",
+      "published_at": "2026-07-21T19:00:00Z",
+      "deprecated": false
+    }
+  }
+}
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