diff --git a/src/quant_platform_kit/data/research_input.py b/src/quant_platform_kit/data/research_input.py
new file mode 100644
index 0000000..ee513b2
--- /dev/null
+++ b/src/quant_platform_kit/data/research_input.py
@@ -0,0 +1,140 @@
+"""Pure validation for immutable research-input manifest metadata.
+
+This S0 contract deliberately does not acquire, read, materialize, replay, or
+otherwise act on the referenced inputs.  It only validates the metadata that
+binds a research consumer to already-produced immutable artifacts.
+"""
+
+from __future__ import annotations
+
+import json
+import re
+from collections.abc import Mapping
+from datetime import datetime
+from typing import Any
+
+
+RESEARCH_INPUT_MANIFEST_SCHEMA_VERSION = "research_input_manifest.v1"
+
+_INPUT_ID = re.compile(r"^[A-Za-z0-9][A-Za-z0-9._-]*$")
+_KIND = re.compile(r"^[a-z][a-z0-9_]*$")
+_SHA256 = re.compile(r"^[a-f0-9]{64}$")
+_RFC3339_DATETIME = re.compile(
+    r"^\d{4}-\d{2}-\d{2}T\d{2}:\d{2}:\d{2}(?:\.\d{1,6})?(?:Z|[+-]\d{2}:\d{2})$"
+)
+_REQUIRED_TOP_LEVEL = frozenset({"schema_version", "manifest_id", "created_at", "as_of", "inputs"})
+_REQUIRED_INPUT = frozenset({"input_id", "kind", "artifact_uri", "sha256", "as_of"})
+
+
+class ResearchInputManifestValidationError(ValueError):
+    """Raised when a research-input manifest violates the S0 contract."""
+
+    def __init__(self) -> None:
+        super().__init__("invalid research input manifest")
+
+
+def validate_research_input_manifest(payload: Mapping[str, Any]) -> dict[str, Any]:
+    """Validate and return immutable metadata without dereferencing input artifacts."""
+
+    if not isinstance(payload, Mapping) or set(payload) != _REQUIRED_TOP_LEVEL:
+        raise ResearchInputManifestValidationError()
+    if payload.get("schema_version") != RESEARCH_INPUT_MANIFEST_SCHEMA_VERSION:
+        raise ResearchInputManifestValidationError()
+
+    _require_identifier(payload.get("manifest_id"))
+    created_at = _parse_datetime(payload.get("created_at"))
+    manifest_as_of = _parse_datetime(payload.get("as_of"))
+    if created_at < manifest_as_of:
+        raise ResearchInputManifestValidationError()
+
+    inputs = payload.get("inputs")
+    if not isinstance(inputs, list) or not inputs:
+        raise ResearchInputManifestValidationError()
+
+    input_ids: set[str] = set()
+    for input_metadata in inputs:
+        _validate_input(input_metadata, manifest_as_of, input_ids)
+
+    return dict(payload)
+
+
+def parse_research_input_manifest(value: bytes) -> dict[str, Any]:
+    """Strictly read canonical manifest bytes without dereferencing artifacts."""
+
+    if not isinstance(value, bytes):
+        raise ResearchInputManifestValidationError()
+    try:
+        parsed = json.loads(
+            value.decode("utf-8"),
+            object_pairs_hook=_reject_duplicate_object_keys,
+            parse_constant=_reject_non_json_constant,
+        )
+    except (UnicodeDecodeError, ValueError, json.JSONDecodeError) as exc:
+        raise ResearchInputManifestValidationError() from exc
+    if type(parsed) is not dict:
+        raise ResearchInputManifestValidationError()
+
+    manifest = validate_research_input_manifest(parsed)
+    if _canonical_json(manifest) != value:
+        raise ResearchInputManifestValidationError()
+    return manifest
+
+
+def _validate_input(value: object, manifest_as_of: datetime, input_ids: set[str]) -> None:
+    if not isinstance(value, Mapping) or set(value) != _REQUIRED_INPUT:
+        raise ResearchInputManifestValidationError()
+
+    input_id = value.get("input_id")
+    _require_identifier(input_id)
+    if input_id in input_ids:
+        raise ResearchInputManifestValidationError()
+    input_ids.add(input_id)
+
+    kind = value.get("kind")
+    if not isinstance(kind, str) or not _KIND.fullmatch(kind):
+        raise ResearchInputManifestValidationError()
+
+    artifact_uri = value.get("artifact_uri")
+    if not isinstance(artifact_uri, str) or not artifact_uri or any(char.isspace() for char in artifact_uri):
+        raise ResearchInputManifestValidationError()
+
+    sha256 = value.get("sha256")
+    if not isinstance(sha256, str) or not _SHA256.fullmatch(sha256):
+        raise ResearchInputManifestValidationError()
+
+    if _parse_datetime(value.get("as_of")) > manifest_as_of:
+        raise ResearchInputManifestValidationError()
+
+
+def _require_identifier(value: object) -> None:
+    if not isinstance(value, str) or not _INPUT_ID.fullmatch(value):
+        raise ResearchInputManifestValidationError()
+
+
+def _parse_datetime(value: object) -> datetime:
+    if not isinstance(value, str) or not _RFC3339_DATETIME.fullmatch(value):
+        raise ResearchInputManifestValidationError()
+    try:
+        parsed = datetime.fromisoformat(value.replace("Z", "+00:00"))
+    except ValueError as exc:
+        raise ResearchInputManifestValidationError() from exc
+    if parsed.tzinfo is None or parsed.utcoffset() is None:
+        raise ResearchInputManifestValidationError()
+    return parsed
+
+
+def _canonical_json(value: Mapping[str, Any]) -> bytes:
+    return json.dumps(value, ensure_ascii=False, sort_keys=True, separators=(",", ":"), allow_nan=False).encode("utf-8")
+
+
+def _reject_duplicate_object_keys(pairs: list[tuple[str, Any]]) -> dict[str, Any]:
+    result: dict[str, Any] = {}
+    for key, value in pairs:
+        if key in result:
+            raise ValueError("duplicate JSON object key")
+        result[key] = value
+    return result
+
+
+def _reject_non_json_constant(value: str) -> None:
+    raise ValueError(f"non-JSON constant: {value}")
diff --git a/src/quant_platform_kit/schemas/research-input-manifest.v1.schema.json b/src/quant_platform_kit/schemas/research-input-manifest.v1.schema.json
new file mode 100644
index 0000000..22ee480
--- /dev/null
+++ b/src/quant_platform_kit/schemas/research-input-manifest.v1.schema.json
@@ -0,0 +1,46 @@
+{
+  "$schema": "https://json-schema.org/draft/2020-12/schema",
+  "$id": "https://quantplatformkit.local/schemas/research-input-manifest.v1.schema.json",
+  "title": "Research Input Manifest v1",
+  "type": "object",
+  "x-qpk-canonical-json": true,
+  "x-qpk-pit-cutoff": {
+    "allow_equal": true,
+    "cutoff": "/as_of",
+    "entries": "/inputs",
+    "timestamp_field": "as_of"
+  },
+  "required": ["schema_version", "manifest_id", "created_at", "as_of", "inputs"],
+  "properties": {
+    "schema_version": { "const": "research_input_manifest.v1" },
+    "manifest_id": { "type": "string", "pattern": "^[A-Za-z0-9][A-Za-z0-9._-]*$" },
+    "created_at": { "$ref": "#/$defs/date_time" },
+    "as_of": { "$ref": "#/$defs/date_time" },
+    "inputs": {
+      "type": "array",
+      "minItems": 1,
+      "x-qpk-unique-by": "input_id",
+      "items": { "$ref": "#/$defs/input" }
+    }
+  },
+  "$defs": {
+    "date_time": {
+      "type": "string",
+      "format": "date-time",
+      "pattern": "^[0-9]{4}-[0-9]{2}-[0-9]{2}T[0-9]{2}:[0-9]{2}:[0-9]{2}(\\.[0-9]{1,6})?(Z|[+-][0-9]{2}:[0-9]{2})$"
+    },
+    "input": {
+      "type": "object",
+      "required": ["input_id", "kind", "artifact_uri", "sha256", "as_of"],
+      "properties": {
+        "input_id": { "type": "string", "pattern": "^[A-Za-z0-9][A-Za-z0-9._-]*$" },
+        "kind": { "type": "string", "pattern": "^[a-z][a-z0-9_]*$" },
+        "artifact_uri": { "type": "string", "minLength": 1, "pattern": "^\\S+$" },
+        "sha256": { "type": "string", "pattern": "^[a-f0-9]{64}$" },
+        "as_of": { "$ref": "#/$defs/date_time" }
+      },
+      "additionalProperties": false
+    }
+  },
+  "additionalProperties": false
+}
diff --git a/tests/test_research_input_manifest_contract.py b/tests/test_research_input_manifest_contract.py
new file mode 100644
index 0000000..4e069ec
--- /dev/null
+++ b/tests/test_research_input_manifest_contract.py
@@ -0,0 +1,115 @@
+from __future__ import annotations
+
+import json
+from pathlib import Path
+
+import pytest
+
+from quant_platform_kit.data.research_input import (
+    RESEARCH_INPUT_MANIFEST_SCHEMA_VERSION,
+    ResearchInputManifestValidationError,
+    parse_research_input_manifest,
+    validate_research_input_manifest,
+)
+
+
+def _valid_manifest() -> dict[str, object]:
+    return {
+        "schema_version": RESEARCH_INPUT_MANIFEST_SCHEMA_VERSION,
+        "manifest_id": "tqqq-research-inputs-2026-07-30",
+        "created_at": "2026-07-30T00:00:00Z",
+        "as_of": "2026-07-29T20:00:00Z",
+        "inputs": [
+            {
+                "input_id": "daily-prices",
+                "kind": "market_data",
+                "artifact_uri": "s3://research-fixtures/tqqq/prices.csv",
+                "sha256": "a" * 64,
+                "as_of": "2026-07-29T20:00:00Z",
+            }
+        ],
+    }
+
+
+def test_manifest_contract_accepts_complete_immutable_input_metadata() -> None:
+    manifest = _valid_manifest()
+
+    assert validate_research_input_manifest(manifest) == manifest
+
+
+def test_manifest_contract_rejects_missing_or_mutable_input_identity() -> None:
+    manifest = _valid_manifest()
+    manifest["inputs"] = [
+        {
+            "input_id": "daily-prices",
+            "kind": "market_data",
+            "artifact_uri": "s3://research-fixtures/tqqq/prices.csv",
+            "sha256": "not-a-digest",
+            "as_of": "2026-07-29T20:00:00Z",
+        }
+    ]
+
+    with pytest.raises(ResearchInputManifestValidationError):
+        validate_research_input_manifest(manifest)
+
+
+def test_manifest_contract_rejects_duplicate_input_ids_and_future_implementation_fields() -> None:
+    manifest = _valid_manifest()
+    manifest["inputs"] = [*manifest["inputs"], dict(manifest["inputs"][0])]
+    manifest["provider"] = {"name": "must-not-be-added-in-s0"}
+
+    with pytest.raises(ResearchInputManifestValidationError):
+        validate_research_input_manifest(manifest)
+
+
+def test_schema_declares_the_same_closed_s0_contract() -> None:
+    root = Path(__file__).resolve().parents[1]
+    schema = json.loads(
+        (root / "src/quant_platform_kit/schemas/research-input-manifest.v1.schema.json").read_text(encoding="utf-8")
+    )
+
+    assert schema["properties"]["schema_version"]["const"] == RESEARCH_INPUT_MANIFEST_SCHEMA_VERSION
+    assert schema["additionalProperties"] is False
+    assert schema["required"] == ["schema_version", "manifest_id", "created_at", "as_of", "inputs"]
+    assert schema["$defs"]["input"]["additionalProperties"] is False
+
+
+def _canonical_json(value: object) -> bytes:
+    return json.dumps(value, ensure_ascii=False, sort_keys=True, separators=(",", ":"), allow_nan=False).encode("utf-8")
+
+
+def test_canonical_readback_rejects_noncanonical_and_duplicate_key_bytes() -> None:
+    expected = _valid_manifest()
+
+    assert parse_research_input_manifest(_canonical_json(expected)) == expected
+
+    with pytest.raises(ResearchInputManifestValidationError):
+        parse_research_input_manifest(json.dumps(expected).encode("utf-8"))
+    with pytest.raises(ResearchInputManifestValidationError):
+        parse_research_input_manifest(
+            b'{"as_of":"2026-07-29T20:00:00Z","as_of":"2026-07-29T20:00:00Z"}'
+        )
+
+
+def test_manifest_contract_rejects_submicrosecond_timestamps() -> None:
+    manifest = _valid_manifest()
+    manifest["as_of"] = "2026-07-29T20:00:00.0000001Z"
+
+    with pytest.raises(ResearchInputManifestValidationError):
+        validate_research_input_manifest(manifest)
+
+
+def test_schema_encodes_pit_cutoff_and_input_id_uniqueness() -> None:
+    root = Path(__file__).resolve().parents[1]
+    schema = json.loads(
+        (root / "src/quant_platform_kit/schemas/research-input-manifest.v1.schema.json").read_text(encoding="utf-8")
+    )
+
+    assert schema["x-qpk-pit-cutoff"] == {
+        "allow_equal": True,
+        "cutoff": "/as_of",
+        "entries": "/inputs",
+        "timestamp_field": "as_of",
+    }
+    assert schema["properties"]["inputs"]["x-qpk-unique-by"] == "input_id"
+    assert "{1,6}" in schema["$defs"]["date_time"]["pattern"]