diff --git a/docs/RECEIPTS.md b/docs/RECEIPTS.md
new file mode 100644
index 000000000..91e031b17
--- /dev/null
+++ b/docs/RECEIPTS.md
@@ -0,0 +1,139 @@
+# Runtime Receipts
+
+This document sketches a future read-only receipt export for completed runtime
+turns. It is a protocol note, not an implemented endpoint.
+
+The goal is to let a local supervisor audit one completed turn without
+screen-scraping the terminal transcript. A receipt should summarize the durable
+runtime records that CodeWhale already owns: thread metadata, turn status, turn
+items, event sequence lineage, usage when available, approval decisions, and
+side-effect boundaries.
+
+## Non-Goals
+
+A receipt is not a safety certification, provider compatibility certification,
+or hosted attestation. It must not call providers, execute tools, write memory,
+write project files, mutate runtime state, or expose API keys.
+
+Receipts should not export raw chain-of-thought or private reasoning by default.
+When reasoning custody is represented, use stable item ids, counts, hashes, or
+explicit `unavailable` fields rather than raw hidden content.
+
+## Candidate Surfaces
+
+Potential local-only surfaces:
+
+```text
+codewhale receipt export --thread <thread_id> --turn <turn_id> --format json
+GET /v1/threads/{thread_id}/turns/{turn_id}/receipt
+```
+
+Both surfaces should share the existing runtime API auth boundary. They should
+only read persisted runtime records and append-only events.
+
+## Current Data Sources
+
+The current runtime store already persists the core inputs a receipt builder
+would need:
+
+- `ThreadRecord`: model, workspace, mode, shell/trust/auto-approve flags,
+  title, task linkage, and latest turn metadata.
+- `TurnRecord`: turn status, input summary, timestamps, duration, usage, error,
+  steer count, and item ids.
+- `TurnItemRecord`: item kind, lifecycle status, summary, optional detail,
+  metadata, artifact refs, and item timestamps.
+- `RuntimeEventRecord`: thread id, turn id, item id, event name, JSON payload,
+  timestamp, and monotonic `seq` values per runtime store.
+
+Not every receipt field can be filled from those records today. If a provider or
+store does not persist a value, the receipt should say `available: false` or
+`unavailable`, not infer it from UI text.
+
+## Draft Schema Shape
+
+```json
+{
+  "schema_id": "codewhale.conformance-receipt/v0",
+  "thread": {
+    "id": "thr_...",
+    "model": "deepseek-v4-pro",
+    "mode": "agent",
+    "auto_approve": false,
+    "trust_mode": false,
+    "allow_shell": false
+  },
+  "turn": {
+    "id": "turn_...",
+    "status": "completed",
+    "started_at": "2026-06-02T01:00:00Z",
+    "ended_at": "2026-06-02T01:00:12Z",
+    "duration_ms": 12000
+  },
+  "reasoning_custody": {
+    "raw_reasoning_exported": false,
+    "available": false,
+    "reason": "reasoning blocks are not persisted as receipt-ready records"
+  },
+  "tool_lineage": {
+    "tool_call_count": 1,
+    "tool_result_count": 1,
+    "unmatched_tool_call_ids": [],
+    "unmatched_tool_result_ids": []
+  },
+  "usage_evidence": {
+    "available": true,
+    "usage": {
+      "prompt_tokens": 123,
+      "completion_tokens": 45
+    },
+    "provider_cache_breakdown_available": false
+  },
+  "source_event_lineage": {
+    "first_seq": 10,
+    "last_seq": 42,
+    "event_count": 33,
+    "missing_event_ranges": []
+  },
+  "side_effect_boundary": {
+    "approval_required_count": 1,
+    "approval_allowed_count": 0,
+    "approval_denied_count": 1,
+    "command_execution_count": 0,
+    "file_change_count": 0,
+    "sandbox_denied_count": 0
+  },
+  "claim_ceiling": [
+    "local_receipt_only",
+    "not_safety_certification",
+    "not_provider_compatibility_certification"
+  ]
+}
+```
+
+## Builder Rules
+
+A receipt builder should be deterministic and conservative:
+
+1. Load the thread and turn by id, then reject mismatched `thread_id` values.
+2. Load only item ids referenced by the turn.
+3. Read event records for the thread and filter by `turn_id`.
+4. Preserve event sequence boundaries with `first_seq`, `last_seq`, and any
+   detected gaps.
+5. Count approval, command, file, sandbox, and tool events from typed records or
+   known event names only.
+6. Mark unavailable evidence explicitly instead of deriving it from free-form
+   summaries.
+7. Emit no raw tool output beyond existing item summaries unless a later schema
+   adds a separate redaction policy.
+
+## Incremental Implementation Path
+
+The safest implementation path is:
+
+1. Land this protocol note and settle field names/non-goals.
+2. Add protocol structs and JSON snapshot fixtures for completed, failed, and
+   approval-denied turns.
+3. Add a pure builder over `ThreadRecord`, `TurnRecord`, `TurnItemRecord`, and
+   `RuntimeEventRecord`.
+4. Expose the local runtime API endpoint.
+5. Add the CLI export command and optional validation mode.
diff --git a/docs/RUNTIME_API.md b/docs/RUNTIME_API.md
index 9ebfada8c..a3582c82c 100644
--- a/docs/RUNTIME_API.md
+++ b/docs/RUNTIME_API.md
@@ -22,6 +22,10 @@ macOS workbench (or any local supervisor)
 The engine runs as a local-only process. All APIs bind to `localhost` by
 default. No hosted relay, no provider-token custody, no secret leakage.
 
+For a proposed read-only audit export over completed turns, see
+[`docs/RECEIPTS.md`](RECEIPTS.md). That document is a protocol note; the receipt
+CLI/API surfaces are not implemented yet.
+
 ## ACP stdio adapter: `codewhale serve --acp`
 
 `codewhale serve --acp` speaks JSON-RPC 2.0 over newline-delimited stdio for
@@ -215,6 +219,9 @@ accept an empty string to clear a previously-set value. Added in v0.8.10 (#562):
 **Events** (SSE replay + live stream)
 - `GET /v1/threads/{id}/events?since_seq=<u64>`
 
+**Receipts** (future read-only audit export)
+- Proposed only: `GET /v1/threads/{thread_id}/turns/{turn_id}/receipt`
+
 **Compatibility stream** (one-shot, backwards-compatible)
 - `POST /v1/stream`