diff --git a/.changeset/15937-confirmed-blueprint-identity-protocol.md b/.changeset/15937-confirmed-blueprint-identity-protocol.md
new file mode 100644
index 00000000000..b429de1d117
--- /dev/null
+++ b/.changeset/15937-confirmed-blueprint-identity-protocol.md
@@ -0,0 +1,14 @@
+---
+"@objectstack/spec": minor
+---
+
+`ToolExecutionContext.confirmedBlueprintIdentity` — the consent digest a route-owning layer stamps on a confirm replay — is now declared in the protocol instead of in one consumer's augmented type (#15937).
+
+Clause-②: yes (widening) — one new OPTIONAL member on a published interface, so the shape a consumer writes against grows. Nothing previously admitted is refused, no member is renamed or retired, and no producer is required to write it. Contract-review tier.
+
+`packages/spec/src/contracts/ai-service.ts` declares the tool-execution context a tool handler may rely on. A published handler in `objectstack-ai/cloud` — the `apply_blueprint` authorization gate — already makes a matching blueprint-identity digest one clause of the decision to build a whole app (cloud#1954 / cloud PR #2005), but the member it reads was declared only on cloud's own augmented `ToolExecutionContext` and reached by a structural cast. The protocol is this project's baseline, so a field a handler authorizes on is declared here.
+
+- **The member is optional and fail-closed.** `undefined` means "no confirmed identity on this turn" and authorizes nothing — the same reading `actor` and `isSystem` already carry (#2991): absence is never a grant. The docblock states it, and the type enforces the handler-side half of it, because a read of `string | undefined` does not compile into a path that assumes a confirmation.
+- **Provenance is part of the declaration**, in the shape `userMessageText` already carries: populated by whichever layer owns the agent route (cloud, post-cloud ADR-0025), only ever by in-process server code on that route, and never derived from a request body, a tool argument or the transcript.
+- **Nothing in this repository reads it yet**, and nothing here changes behaviour: this is the declaration half. Deleting cloud's augmentation and replacing its cast with the typed read is a cloud follow-up, blocked on this field being published and pinned.
+- **The contract is now asserted.** `confirmed-blueprint-identity-contract.pin.test.ts` pins that the member lives on `ToolExecutionContext`, reaches a handler through `ChatWithToolsOptions.toolExecutionContext`, stays optional, and is typed `string` — each negative leg paired with a positive one on the same helper, so a leg that stops detecting anything turns the test-layer type-check red rather than passing quietly.
diff --git a/packages/spec/src/contracts/ai-service.ts b/packages/spec/src/contracts/ai-service.ts
index 09a8849ad6c..bf79a0cc3f6 100644
--- a/packages/spec/src/contracts/ai-service.ts
+++ b/packages/spec/src/contracts/ai-service.ts
@@ -627,6 +627,28 @@ export interface ToolExecutionContext {
      * Populated by whichever layer owns the agent route (cloud, post-ADR-0025).
      */
     userMessageText?: string;
+    /**
+     * Blueprint-identity digest stamped on a CONFIRM REPLAY of an already
+     * approved proposal — the consent record saying *this exact blueprint* is
+     * the one the user approved, carried onto the turn that replays it.
+     * Populated by whichever layer owns the agent route (cloud, post-cloud
+     * ADR-0025) — the same provenance {@link userMessageText} carries — and set
+     * only by in-process server code on that route. ⛔ NEVER derived from a
+     * request body, a tool argument or the transcript: anything the caller can
+     * write is not a confirmation.
+     *
+     * `undefined` means "no confirmed identity on this turn" and authorizes
+     * NOTHING — the same fail-closed reading as {@link actor} and
+     * {@link isSystem} (#2991). A handler MUST NOT read consent out of a
+     * missing field.
+     *
+     * Declared here because a published handler already AUTHORIZES on it:
+     * cloud's `apply_blueprint` gate makes a matching identity one clause of
+     * the decision to build a whole app (cloud#1954, cloud PR #2005). A field a
+     * handler authorizes on belongs in the declared contract, not in a
+     * consumer's structural cast.
+     */
+    confirmedBlueprintIdentity?: string;
     /** Distributed-trace id for cross-service correlation. */
     traceId?: string;
     /**
diff --git a/packages/spec/src/contracts/confirmed-blueprint-identity-contract.pin.test.ts b/packages/spec/src/contracts/confirmed-blueprint-identity-contract.pin.test.ts
new file mode 100644
index 00000000000..7d011893e94
--- /dev/null
+++ b/packages/spec/src/contracts/confirmed-blueprint-identity-contract.pin.test.ts
@@ -0,0 +1,124 @@
+// Copyright (c) 2026 ObjectStack. Licensed under the Apache-2.0 license.
+
+/**
+ * [#15937] `ToolExecutionContext.confirmedBlueprintIdentity`, pinned where a
+ * grep can find it.
+ *
+ * The field arrives in the protocol because a PUBLISHED handler already
+ * authorizes on it: cloud's `apply_blueprint` gate makes a matching
+ * blueprint-identity digest one clause of the decision to build a whole app
+ * (cloud#1954 / cloud PR #2005), and until this card it read the value off the
+ * execution context through a structural cast against a declaration that lived
+ * only in that one consumer's augmented type. A consent field a handler
+ * authorizes on belongs in the declared contract.
+ *
+ * ## What is pinned, and what is deliberately NOT
+ *
+ * Pinned: that the member lives on `ToolExecutionContext` itself (not on some
+ * neighbouring options bag), that it reaches a handler through the same
+ * `ChatWithToolsOptions.toolExecutionContext` thread every other field uses,
+ * that it is OPTIONAL and reads back `undefined` when absent, that its read
+ * type is `string | undefined` rather than `string` — so a handler cannot
+ * compile a path that assumes a confirmation is always present — and that it
+ * is typed `string` rather than `any`, which is what makes the two
+ * `@ts-expect-error` legs below detect anything at all.
+ *
+ * NOT pinned: any authorization behaviour. The gate that consumes this field
+ * lives in `objectstack-ai/cloud` and is not in this tree, so a behavioural
+ * assertion here would be a stub asserting itself. This file pins the
+ * DECLARATION half, which is the half this repository owns.
+ *
+ * ## Why every leg carries a control
+ *
+ * A `@ts-expect-error` is only a check while the line under it really is an
+ * error: an unused directive is itself a `tsc` error (TS2578) under
+ * `packages/spec`'s test-layer program, so each negative leg goes red — rather
+ * than quietly green — the day the type stops refusing what it names. The
+ * positive legs are the other half of the same pair: the near-miss spelling is
+ * refused only because the correct spelling on the line above is accepted.
+ */
+
+import { describe, it, expect } from 'vitest';
+
+import type { ChatWithToolsOptions, ToolExecutionContext } from './ai-service';
+
+/** Identity helper, so a rejected shape errors on the argument's own line. */
+const asCtx = (c: ToolExecutionContext) => c;
+const asOptions = (o: ChatWithToolsOptions) => o;
+
+/** A plausible digest — the shape cloud stamps, opaque to this contract. */
+const DIGEST = 'sha256:3f6a1c0e9b2d4a7f8c5e1b0d9a2f4c6e8b0d3a5f7c9e1b3d5a7f9c1e3b5d7a9f';
+
+describe('confirmedBlueprintIdentity contract (#15937)', () => {
+  it('is declared on `ToolExecutionContext` and round-trips the digest', () => {
+    const ctx = asCtx({
+      actor: { id: 'usr_1' },
+      conversationId: 'conv_1',
+      confirmedBlueprintIdentity: DIGEST,
+    });
+
+    expect(ctx.confirmedBlueprintIdentity).toBe(DIGEST);
+  });
+
+  it('reaches a handler through the same context thread as every other field', () => {
+    // Declaring the member is worthless if the only path a tool handler sees it
+    // on does not carry it. This is that path.
+    const options = asOptions({
+      toolExecutionContext: { confirmedBlueprintIdentity: DIGEST },
+    });
+
+    expect(options.toolExecutionContext?.confirmedBlueprintIdentity).toBe(DIGEST);
+  });
+
+  it('is OPTIONAL, and absence reads as `undefined` rather than anything truthy', () => {
+    // "No confirmed identity on this turn" is the resting state of every turn
+    // that is not a confirm replay, so a context without the member must still
+    // be a legal `ToolExecutionContext`.
+    const none = asCtx({ actor: { id: 'usr_1' } });
+
+    expect(none.confirmedBlueprintIdentity).toBeUndefined();
+    // Control: the same read is lit on a context that does carry it, so the
+    // `undefined` above is the ABSENT member and not a misspelled read.
+    expect(asCtx({ confirmedBlueprintIdentity: DIGEST }).confirmedBlueprintIdentity).toBe(DIGEST);
+  });
+
+  it('reads as `string | undefined`, so no handler can assume a confirmation', () => {
+    const ctx = asCtx({ actor: { id: 'usr_1' } });
+
+    // @ts-expect-error — the member is optional on purpose: absence authorizes
+    // nothing, and a consumer that narrows it to `string` without a check has
+    // written exactly the path this contract forbids. Were the member ever made
+    // required, this directive would stop detecting anything and TS2578 would
+    // fail the test-layer type-check.
+    const assumed: string = ctx.confirmedBlueprintIdentity;
+    expect(assumed).toBeUndefined();
+
+    // Control: the guarded read — the shape a handler is meant to write — does
+    // compile, so the leg above is refused for its missing check and not
+    // because the member is unreadable.
+    const guarded: string = ctx.confirmedBlueprintIdentity ?? '';
+    expect(guarded).toBe('');
+  });
+
+  it('is typed `string`, not `any` — a non-string is a compile error', () => {
+    const wrong = asCtx({
+      // @ts-expect-error — a digest is a string. Typed `any` or `unknown` this
+      // line would compile and the directive would go unused (TS2578), so this
+      // leg also pins that the member did not arrive untyped.
+      confirmedBlueprintIdentity: 42,
+    });
+
+    expect(String(wrong.confirmedBlueprintIdentity)).toBe('42');
+  });
+
+  it('is pinned by its SPELLING — a near-miss is not the confirmation field', () => {
+    const typo = asCtx({
+      // @ts-expect-error — the excess-property check refuses a member
+      // `ToolExecutionContext` does not declare. The lit control is the first
+      // leg above, where the correct spelling on the same helper is accepted.
+      confirmedBlueprintIdentify: DIGEST,
+    });
+
+    expect(typo.confirmedBlueprintIdentity).toBeUndefined();
+  });
+});