@@ -0,0 +1,16 @@
+// Callback-style handler — (event, context, callback) instead of async —
+// manually wrapped with datadog(). The migration spike broke exactly this
+// seam: the new host's tracePromise wrapper replaced promisifiedHandler's
+// call site, so callback handlers returned null to API Gateway. handler.spec
+// pins the unit behavior; this case pins the same path end to end through
+// the RIE invoke. The setTimeout makes the completion genuinely asynchronous
+// so the wrapper cannot mistake it for a sync return.
+const { datadog } = require("datadog-lambda-js");
+
+function handle(event, context, callback) {
+  setTimeout(() => {
+    callback(null, { message: "hello, dog!" });
+  }, 10);
+}
+
+module.exports.handle = datadog(handle);
@@ -0,0 +1,35 @@
+// fetch variant of http-requests.js. On Node 18+ the global fetch is
+// undici, which dd-trace instruments through its undici plugin — a different
+// injection path than the http/https plugin that patches axios in
+// http-requests.js. Both paths must keep injecting the x-datadog-* trace
+// context; this case pins the fetch one.
+//
+// Like http-requests.js this entry point is UNWRAPPED and runs through the
+// npm redirect entry (dist/handler.handler) in the cjs-fetch-requests case,
+// so dd-trace initializes before the user handler loads and the tracer's
+// undici plugin does the injection. The mock echoes the request headers and
+// this handler logs them, so the golden shows the injected downstream trace
+// context (x-datadog-trace-id / x-datadog-parent-id, normalized to XXXX).
+const { sendDistributionMetric } = require("datadog-lambda-js");
+
+const urls = (process.env.MOCK_HTTP_URLS ||
+  "https://ip-ranges.datadoghq.com,https://ip-ranges.datadoghq.eu"
+).split(",");
+
+async function handle(event, context) {
+  const responsePayload = { message: "hello, dog!" };
+
+  sendDistributionMetric("serverless.integration_test.execution", 1, "function:fetch-request");
+
+  for (let index = 0; index < urls.length; index++) {
+    const response = await fetch(urls[index]);
+    const body = await response.json();
+    console.log(`mock-http saw headers for ${urls[index]}: ${JSON.stringify(body.headers)}`);
+  }
+
+  console.log(`Snapshot test fetch requests successfully made to URLs: ${urls}`);
+
+  return responsePayload;
+}
+
+module.exports.handle = handle;
@@ -61,8 +61,12 @@ The case names are:
 | `manual-status-500` | manual wrap with userland `dd-trace` init returning a 500 API Gateway response (`DD_TRACE_ENABLED=true`); error span tag + enhanced error metrics |
 | `manual-send-metrics` | manual wrap calling `sendDistributionMetric` inside and outside the handler; per-event return values |
 | `manual-process-input` | manual wrap with userland `dd-trace` init reading the active span; per-event return values |
+| `manual-callback` | manual wrap of a callback-style `(event, context, callback)` handler; pins the `promisifiedHandler` seam end to end (the migration spike broke exactly this) |
+| `manual-metrics-only` | `DD_TRACE_ENABLED=false` (metrics-only customers): enhanced + custom metrics still flush, no `aws.lambda` span, no trace JSON, no `dd.trace_id` log correlation |
+| `cjs-capture-payload` | `DD_CAPTURE_LAMBDA_PAYLOAD=true` in redirect mode; span meta gains `function.request` / `function.response` with the captured payloads |
 | `cjs-http-requests` | downstream HTTP calls against a hermetic mock server in redirect mode; asserts injected `x-datadog-*`/`traceparent` headers and log injection via dd-trace's http plugin |
 | `manual-http-requests` | same handler, manual wrap without userland dd-trace init; exercises the library's own `patchHttp` fallback (request wrapping + per-request logging + exact header set via mock echo) |
+| `cjs-fetch-requests` | fetch variant of `cjs-http-requests`: the global fetch (undici) is instrumented by a different dd-trace plugin than http/https; mock echo pins the injected headers on that path |
 | `cjs-custom-extractor` | `DD_TRACE_EXTRACTOR=extractor.extract`; asserts `_dd.parent_source: event` on the inferred span |
 | `cjs-proactive-init` | eager-init managed-instances RIE path with a 15 s init→invoke gap; asserts proactive-initialization markers on the raw logs |
 
@@ -281,3 +285,16 @@ endpoints). Do not diff one suite's output against the other's snapshots.
 - The layer fixture installs into a plain `/opt/nodejs/node_modules`
   directory rather than a real published layer zip, so layer-version
   metadata (e.g. an exact layer ARN in tags) cannot be reproduced locally.
+
+Deliberately not covered locally (each has an assigned owner — do not re-add
+here without closing that owner first):
+
+- response streaming and `time_to_first_byte` — RIE cannot stream
+  invocations; owned by the `serverless-e2e-tests` lambda-features suite.
+- direct-API and KMS/Secrets Manager metric key paths — need real AWS;
+  unit specs plus an L3 spot-check.
+- aws-sdk v2/v3 client spans in the lambda context (parenting under
+  `aws.lambda`, flush before invocation end) — need real AWS services;
+  owned by L3.
+- durable-execution checkpoint extraction — owned by
+  `serverless-e2e-tests/durable-functions`.
@@ -22,10 +22,14 @@
 # manual-status-500        | cjs   | status-code-500s.handle                  | manual wrap; API GW 500 -> span error + enhanced error metric
 # manual-send-metrics      | cjs   | send-metrics.handle                      | manual wrap; sendDistributionMetric via DD_FLUSH_TO_LOG
 # manual-process-input     | cjs   | process-input.handle                     | manual wrap; dd-trace child spans via tracer.wrap
+# manual-callback          | cjs   | callback.handle                          | manual wrap; callback-style (event, context, callback) handler — the spike's proven break seam
 # cjs-http-requests       | cjs   | node_modules/datadog-lambda-js/dist/handler.handler | npm redirect; downstream HTTP header injection via dd-trace's http plugin (hermetic mock server)
 # manual-http-requests    | cjs   | http-requests-manual.handle              | manual wrap; patchHttp fallback wrapping + per-request logging (hermetic mock)
+# cjs-fetch-requests      | cjs   | node_modules/datadog-lambda-js/dist/handler.handler | npm redirect; header injection on global fetch via dd-trace's undici plugin (hermetic mock)
 # cjs-custom-extractor     | cjs   | node_modules/datadog-lambda-js/dist/handler.handler | DD_TRACE_EXTRACTOR custom extractor + _dd.parent_source
 # cjs-proactive-init       | cjs   | node_modules/datadog-lambda-js/dist/handler.handler | proactive-initialization markers (raw-log assertions)
+# manual-metrics-only      | cjs   | send-metrics.handle                      | DD_TRACE_ENABLED=false: metrics flush, no spans, no log correlation
+# cjs-capture-payload      | cjs   | node_modules/datadog-lambda-js/dist/handler.handler | DD_CAPTURE_LAMBDA_PAYLOAD=true: function.request/response span tags
 #
 # Usage (from repo root or this directory):
 #   ./integration_tests_local/run.sh                 # all runtimes, all cases
@@ -111,10 +115,14 @@ ALL_CASES=(
     "manual-status-500"
     "manual-send-metrics"
     "manual-process-input"
+    "manual-callback"
     "cjs-http-requests"
     "manual-http-requests"
+    "cjs-fetch-requests"
     "cjs-custom-extractor"
     "cjs-proactive-init"
+    "manual-metrics-only"
+    "cjs-capture-payload"
 )
 
 function configure_case() {
@@ -184,6 +192,37 @@ function configure_case() {
             case_entry_handler="process-input.handle"
             case_return_mode=per-event
             ;;
+        manual-callback)
+            # Callback-style (event, context, callback) handler under manual
+            # wrap — the seam the migration spike broke (the tracePromise
+            # wrapper replaced promisifiedHandler's call site, so callback
+            # handlers returned null to API Gateway). handler.spec.ts pins
+            # the unit behavior; this case pins the same path end to end
+            # through the RIE invoke.
+            case_image=cjs
+            case_entry_handler="callback.handle"
+            ;;
+        manual-metrics-only)
+            # DD_TRACE_ENABLED=false — metrics-only customers. The golden pins
+            # that enhanced + custom metrics still flush (via DD_FLUSH_TO_LOG)
+            # while no aws.lambda span, no trace JSON and no dd.trace_id log
+            # correlation appear. Same handler and per-event payloads as
+            # manual-send-metrics; the diff between the two goldens is exactly
+            # the tracing surface.
+            case_image=cjs
+            case_entry_handler="send-metrics.handle"
+            case_extra_env=(-e DD_TRACE_ENABLED=false)
+            case_return_mode=per-event
+            ;;
+        cjs-capture-payload)
+            # DD_CAPTURE_LAMBDA_PAYLOAD=true — the aws.lambda span meta gains
+            # function.request / function.response holding the captured
+            # payloads (event JSON is static, so the captured tags are
+            # deterministic).
+            case_image=cjs
+            case_entry_handler="node_modules/datadog-lambda-js/dist/handler.handler"
+            case_extra_env=(-e DD_LAMBDA_HANDLER=handler.handle -e DD_CAPTURE_LAMBDA_PAYLOAD=true)
+            ;;
         cjs-http-requests)
             # Redirect mode, not manual wrap: redirect mode initializes
             # dd-trace before the user handler loads, so the tracer's http
@@ -219,6 +258,18 @@ function configure_case() {
             case_needs_mock=true
             case_extra_env=(-e "MOCK_HTTP_URLS=http://mock-http:8080/ip-ranges-us,http://mock-http:8080/ip-ranges-eu")
             ;;
+        cjs-fetch-requests)
+            # fetch/undici variant of cjs-http-requests: on Node 18+ the
+            # global fetch is undici, instrumented by dd-trace's undici
+            # plugin — a different injection path than the http/https plugin
+            # that patches axios. Redirect mode, so dd-trace initializes
+            # before the user handler loads and the plugin does the
+            # injection; the mock echo pins the injected headers.
+            case_image=cjs
+            case_entry_handler="node_modules/datadog-lambda-js/dist/handler.handler"
+            case_needs_mock=true
+            case_extra_env=(-e DD_LAMBDA_HANDLER=fetch-requests.handle -e "MOCK_HTTP_URLS=http://mock-http:8080/ip-ranges-us,http://mock-http:8080/ip-ranges-eu")
+            ;;
         cjs-custom-extractor)
             case_image=cjs
             case_entry_handler="node_modules/datadog-lambda-js/dist/handler.handler"