diff --git a/src/core/operations.ts b/src/core/operations.ts
index 2d763ef9b..ad1a14e64 100644
--- a/src/core/operations.ts
+++ b/src/core/operations.ts
@@ -451,6 +451,7 @@ const get_page: Operation = {
     slug: { type: 'string', required: true, description: 'Page slug' },
     fuzzy: { type: 'boolean', description: 'Enable fuzzy slug resolution (default: false)' },
     include_deleted: { type: 'boolean', description: 'v0.26.5: surface soft-deleted pages with deleted_at populated (default: false). Used by restore workflows.' },
+    source_id: { type: 'string', description: "Scope to a single source (overrides OperationContext.sourceId, consistent with query-tool's --source-id flag)." },
   },
   handler: async (ctx, p) => {
     const slug = p.slug as string;
@@ -461,7 +462,15 @@ const get_page: Operation = {
     // resolves to no source), the engine two-branch query falls through to
     // the cross-source view, preserving pre-v0.31.8 behavior. MCP callers
     // (stdio + HTTP) populate ctx.sourceId via the transport layer.
-    const sourceOpts = ctx.sourceId ? { sourceId: ctx.sourceId } : {};
+    //
+    // Per-call source_id parameter overrides ctx.sourceId, consistent with
+    // how query-tool resolves source (--source-id flag). Without this, MCP
+    // clients with a default-source bearer (e.g. a write-scoped client with
+    // source_id=default) could never get_page against pages in non-default
+    // sources, even with federated_read access. Symmetry with query-tool.
+    const explicitSourceId = p.source_id as string | undefined;
+    const effectiveSourceId = explicitSourceId ?? ctx.sourceId;
+    const sourceOpts = effectiveSourceId ? { sourceId: effectiveSourceId } : {};
 
     let page = await ctx.engine.getPage(slug, { includeDeleted, ...sourceOpts });
     let resolved_slug: string | undefined;
diff --git a/test/get-page-source-id-param.test.ts b/test/get-page-source-id-param.test.ts
new file mode 100644
index 000000000..b97fdbae7
--- /dev/null
+++ b/test/get-page-source-id-param.test.ts
@@ -0,0 +1,151 @@
+/**
+ * Regression guard for get_page source_id parameter handling.
+ *
+ * Background: prior to this PR, get_page ignored the per-call source_id
+ * parameter entirely — only OperationContext.sourceId was respected.
+ * MCP clients with a default-source bearer (e.g. a write-scoped client
+ * with source_id=default) could not get_page pages in non-default
+ * sources, even when federated_read access was granted. The query-tool already
+ * supported per-call source_id via the --source-id flag; this PR brings
+ * get_page into symmetry with that.
+ *
+ * Covers:
+ *   - get_page with explicit p.source_id overrides ctx.sourceId
+ *   - get_page without p.source_id falls back to ctx.sourceId (backwards compat)
+ *   - get_page with neither falls back to cross-source view (v0.31.8 behavior)
+ *   - fuzzy resolution honors the explicit source_id (not just first call)
+ */
+
+import { describe, test, expect } from 'bun:test';
+import { operations, type OperationContext } from '../src/core/operations.ts';
+
+const STUB_LOGGER = {
+  info: () => {},
+  warn: () => {},
+  error: () => {},
+};
+
+const STUB_CONFIG = {} as unknown as Parameters<typeof operations[number]['handler']>[0]['config'];
+
+function findOp(name: string) {
+  const op = operations.find(o => o.name === name);
+  if (!op) throw new Error(`operation ${name} not found`);
+  return op;
+}
+
+/**
+ * Engine stub that records every getPage call's sourceId option,
+ * so tests can assert which source the handler dispatched to.
+ *
+ * Returns a fake page only when the requested source matches the
+ * configured `pagesBySource` map, so we can verify that the right
+ * lookup is happening (not just that the option is threaded).
+ */
+function recordingEngine(pagesBySource: Record<string, string[]>) {
+  const calls: Array<{ slug: string; sourceId?: string; includeDeleted?: boolean }> = [];
+  return {
+    calls,
+    engine: {
+      getPage: async (slug: string, opts: { sourceId?: string; includeDeleted?: boolean }) => {
+        calls.push({ slug, sourceId: opts.sourceId, includeDeleted: opts.includeDeleted });
+        const sourceKey = opts.sourceId ?? '__cross__';
+        const slugs = pagesBySource[sourceKey] ?? [];
+        if (slugs.includes(slug)) {
+          return { slug, source_id: opts.sourceId ?? 'default', body: 'stub body', deleted_at: null };
+        }
+        return null;
+      },
+      resolveSlugs: async () => [],
+      getTags: async () => [],
+      // remaining engine methods unused for this op; default to throwing.
+    },
+  };
+}
+
+function ctx(sourceId: string | undefined, engineStub: any): OperationContext {
+  return {
+    engine: engineStub.engine,
+    sourceId,
+    logger: STUB_LOGGER,
+    config: STUB_CONFIG,
+  } as unknown as OperationContext;
+}
+
+describe('get_page source_id parameter handling', () => {
+  const get_page = findOp('get_page');
+
+  test('explicit p.source_id overrides ctx.sourceId', async () => {
+    // Page lives in non-default source. Bearer's ctx.sourceId is 'default'.
+    // Pre-PR: would fail page_not_found. Post-PR: succeeds.
+    const engine = recordingEngine({
+      'priv-karriere-entities': ['claim/15-end-to-end-produkt-ownership'],
+    });
+    const result = await get_page.handler(
+      ctx('default', engine),
+      { slug: 'claim/15-end-to-end-produkt-ownership', source_id: 'priv-karriere-entities' }
+    );
+    expect(result).toBeTruthy();
+    expect(engine.calls[0].sourceId).toBe('priv-karriere-entities');
+  });
+
+  test('without p.source_id falls back to ctx.sourceId (backwards compat)', async () => {
+    const engine = recordingEngine({
+      'default': ['some-page'],
+    });
+    const result = await get_page.handler(
+      ctx('default', engine),
+      { slug: 'some-page' }
+    );
+    expect(result).toBeTruthy();
+    expect(engine.calls[0].sourceId).toBe('default');
+  });
+
+  test('with neither p.source_id nor ctx.sourceId, sourceOpts is empty (cross-source view)', async () => {
+    const engine = recordingEngine({
+      '__cross__': ['some-page'],
+    });
+    const result = await get_page.handler(
+      ctx(undefined, engine),
+      { slug: 'some-page' }
+    );
+    expect(result).toBeTruthy();
+    expect(engine.calls[0].sourceId).toBeUndefined();
+  });
+
+  test('fuzzy resolution honors explicit source_id', async () => {
+    // When fuzzy is used, both the initial getPage and the fuzzy
+    // getPage(candidate) must use the same effective source.
+    const engine = {
+      calls: [] as Array<{ slug: string; sourceId?: string }>,
+      engine: {
+        getPage: async function (this: any, slug: string, opts: { sourceId?: string }) {
+          this.calls.push({ slug, sourceId: opts.sourceId });
+          if (slug === 'fuzzy-target-resolved') {
+            return { slug, source_id: opts.sourceId ?? 'default', body: 'stub', deleted_at: null };
+          }
+          return null;
+        },
+        resolveSlugs: async (_slug: string) => ['fuzzy-target-resolved'],
+        getTags: async () => [],
+      },
+    } as any;
+    engine.engine.getPage = engine.engine.getPage.bind(engine);
+    const result = await get_page.handler(
+      ctx('default', engine),
+      { slug: 'fuzzy-target', fuzzy: true, source_id: 'priv-karriere-entities' }
+    );
+    expect(result).toBeTruthy();
+    // Both lookups (initial + fuzzy-resolved) must use the override.
+    expect(engine.calls.every((c: { sourceId?: string }) => c.sourceId === 'priv-karriere-entities')).toBe(true);
+    expect(engine.calls.length).toBe(2);
+  });
+
+  test('source_id is declared in params schema', () => {
+    const p = get_page.params.source_id;
+    expect(p).toBeDefined();
+    expect(p.type).toBe('string');
+    // Description should mention the override behavior so MCP clients
+    // discover the capability.
+    expect(p.description?.toLowerCase() ?? '').toContain('override');
+  });
+});