ref(core)!: Split browser/server-only exports out of the default entrypoint (#23762)

Splits the browser- and server-only exports out of `@sentry/core`'s
default entrypoint. `@sentry/core` now exposes **only isomorphic code**,
and the `@sentry/core/browser` and `@sentry/core/server` entrypoints now
contain **only** their platform-specific exports instead of also
re-exporting the shared surface on top.

Previously the default entrypoint re-exported everything (via
`shared-exports.ts`), and both `/browser` and `/server` re-exported that
shared surface plus their platform extras. That meant importing anything
from `@sentry/core` could drag server-only code (http server/client
instrumentation, ANR, postgres/sql helpers, …) into browser bundles, and
the platform entrypoints were never cleanly separable.

After this change:

- **`@sentry/core`** — isomorphic exports only (the former
`shared-exports.ts`, inlined into `index.ts`).
- **`@sentry/core/browser`** — browser-only exports, e.g. the guarded
`startSpan`/`startInactiveSpan` variants that install
`spanStreamingIntegration`.
- **`@sentry/core/server`** — server-only exports:
`ServerRuntimeClient`, `ServerRuntimeOptions`, `trpcMiddleware`,
`wrapMcpServerWithSentry`, the http client/server subscription APIs,
`flushIfServerless`, `loadModule`, node stack-trace helpers,
postgres/sql instrumentation, and more.

Consumer packages were updated to import platform-specific symbols from
the matching entrypoint rather than from `@sentry/core`.

_Root cause_ of the guarded-span split: the browser SDK's `init()`
deliberately omits `spanStreamingIntegration` — referencing it would
keep the whole span-streaming graph in every bundle, including
error-only ones. Because the plain and guarded span-start APIs share
their names, importing the plain variant in browser code compiles fine
but produces spans that are then never sent. The new
`no-unguarded-span-apis` lint rule is the only thing that catches this,
and enforces that browser-facing code imports the span-start APIs from
`@sentry/core/browser`.

### Decisions

- The three entrypoints are kept **disjoint** rather than having
`/browser` and `/server` re-export the isomorphic surface. Consumers
import isomorphic code from `@sentry/core` and platform code from the
matching subpath — this is what makes the separation meaningful for
tree-shaking and bundle size.
- Marked breaking (`!`): symbols previously reachable from
`@sentry/core` (e.g. `trpcMiddleware`, `wrapMcpServerWithSentry`) now
live under `@sentry/core/server`.

---------

Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: mydea

dev-packages/deno-integration-tests/suites/direct-client-acs/scenario.mjs

@@ -7,7 +7,8 @@
 // (it waits for the tracing-channel binding), so a nested db span here proves
 // `DenoClient.init()` installs that strategy on the direct-construction path.
 // Without it, the subscriber never binds and no span is produced.
-import { createStackParser, nodeStackLineParser } from '@sentry/core';
+import { createStackParser } from '@sentry/core';
+import { nodeStackLineParser } from '@sentry/core/server';
 import { DenoClient, getCurrentScope, getDefaultIntegrations, startSpan } from '@sentry/deno';
 import { tracingChannel } from 'node:diagnostics_channel';
 

dev-packages/e2e-tests/test-applications/nuxt-3/server/plugins/customNitroErrorHandler.ts

@@ -1,4 +1,5 @@
-import { Context, flushIfServerless } from '@sentry/core';
+import { Context } from '@sentry/core';
+import { flushIfServerless } from '@sentry/core/server';
 import * as SentryNode from '@sentry/node';
 import { H3Error } from 'h3';
 import type { CapturedErrorContext } from 'nitropack';

dev-packages/e2e-tests/test-applications/tsx-express/src/mcp.ts

@@ -4,7 +4,7 @@ import { McpServer, ResourceTemplate } from '@modelcontextprotocol/sdk/server/mc
 import { SSEServerTransport } from '@modelcontextprotocol/sdk/server/sse.js';
 import { StreamableHTTPServerTransport } from '@modelcontextprotocol/sdk/server/streamableHttp.js';
 import { z } from 'zod';
-import { wrapMcpServerWithSentry } from '@sentry/core';
+import { wrapMcpServerWithSentry } from '@sentry/node';
 
 // Helper to check if request is an initialize request (compatible with all MCP SDK versions)
 function isInitializeRequest(body: unknown): boolean {

dev-packages/node-integration-tests/suites/tracing/postgres-streamed/scenario-native.mjs

@@ -1,5 +1,5 @@
 import * as Sentry from '@sentry/node';
-import { uuid4 } from '@sentry/core/server';
+import { uuid4 } from '@sentry/core';
 import { waitForConnection } from '@sentry-internal/node-integration-tests';
 import pg from 'pg';
 

dev-packages/node-integration-tests/suites/tracing/postgres-streamed/scenario.mjs

@@ -1,5 +1,5 @@
 import * as Sentry from '@sentry/node';
-import { uuid4 } from '@sentry/core/server';
+import { uuid4 } from '@sentry/core';
 import { waitForConnection } from '@sentry-internal/node-integration-tests';
 import { Client } from 'pg';
 

dev-packages/node-integration-tests/suites/tracing/postgres/scenario-native.mjs

@@ -1,5 +1,5 @@
 import * as Sentry from '@sentry/node';
-import { uuid4 } from '@sentry/core/server';
+import { uuid4 } from '@sentry/core';
 import { waitForConnection } from '@sentry-internal/node-integration-tests';
 import pg from 'pg';
 

dev-packages/node-integration-tests/suites/tracing/postgres/scenario.mjs

@@ -1,5 +1,5 @@
 import * as Sentry from '@sentry/node';
-import { uuid4 } from '@sentry/core/server';
+import { uuid4 } from '@sentry/core';
 import { waitForConnection } from '@sentry-internal/node-integration-tests';
 import { Client } from 'pg';
 

dev-packages/node-integration-tests/suites/tracing/postgresjs-streamed/scenario-requestHook.mjs

@@ -1,5 +1,5 @@
 import * as Sentry from '@sentry/node';
-import { uuid4 } from '@sentry/core/server';
+import { uuid4 } from '@sentry/core';
 import postgres from 'postgres';
 import { waitForConnection } from '@sentry-internal/node-integration-tests';
 

dev-packages/node-integration-tests/suites/tracing/postgresjs-streamed/scenario-unsafe.mjs

@@ -1,5 +1,5 @@
 import * as Sentry from '@sentry/node';
-import { uuid4 } from '@sentry/core/server';
+import { uuid4 } from '@sentry/core';
 import postgres from 'postgres';
 import { waitForConnection } from '@sentry-internal/node-integration-tests';
 

dev-packages/node-integration-tests/suites/tracing/postgresjs-streamed/scenario-url.mjs

@@ -1,5 +1,5 @@
 import * as Sentry from '@sentry/node';
-import { uuid4 } from '@sentry/core/server';
+import { uuid4 } from '@sentry/core';
 import postgres from 'postgres';
 import { waitForConnection } from '@sentry-internal/node-integration-tests';