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Hi,
This headline is something we are genuinely excited about: native support for AWS Bedrock
AgentCore, making the
Serverless Framework
the fastest way to build and deploy production AI agents on AWS. Read on for the full picture.
V4 has come a long way. If your team is still on V3, now is a great time to make the move - the
gap in features, performance, and security has grown considerably, and everything in this
newsletter is V4-only. A Subscription includes 24/7 support from our team. If you want
to talk through what a Subscription looks like for your team,
schedule a few minutes with us
- we are happy to help.
-
Austen
AWS Bedrock AgentCore is Now Built-in
Docs:
AWS Bedrock AgentCore
Building a production AI agent is harder than it looks - not because of the AI part, but because
of everything around it.
If your instinct is to reach for Lambda, you will get surprisingly far. But the moment your agent
needs to hold a multi-turn conversation, run a complex tool chain that takes several minutes,
handle a 30 MB file, or stream tokens back to a user in real time, Lambda starts to crack. Its
15-minute execution limit kills long-running agentic loops mid-task. Its stateless design means
every invocation starts fresh, so you end up bolting on DynamoDB session storage, S3 round-trips
for larger payloads, custom streaming infrastructure, and your own auth middleware. That is weeks
of undifferentiated infrastructure work before you have written a single line of actual agent
logic.
AWS built AgentCore to solve exactly this. It is a purpose-built serverless compute platform for
AI agents - not a general-purpose function runner, but a runtime designed around how agents
actually behave. Under the hood, each user session runs in a dedicated Firecracker microVM:
hardware-level isolation (not just container isolation), 2 vCPU and 8 GB of RAM, with a session
lifetime of up to 8 hours. The container stays warm between turns in a conversation, so state
lives in memory - no serialization, no round-trips to a database. Streaming is built in. JWT
authentication is built in. Tool execution with MCP and Agent-to-Agent (A2A) protocol support is
built in. The 100 MB payload limit means you can send a large document directly without a
pre-signed S3 workaround.
Compared to Lambda, the tradeoffs are clear: Lambda remains the right choice for short, stateless,
high-volume function invocations. AgentCore is the right choice when your agent runs for minutes,
maintains conversational context, needs per-session isolation for security, or has to handle the
kinds of workloads real users generate. For teams moving AI agents from prototype to production,
it removes the infrastructure problem entirely so you can focus on the agent itself.
With v4.33 of the Serverless Framework, AgentCore support is now built in. Using a new top-level
ai
block in your
serverless.yml, you can define agents, tools, memory, browsers, and code interpreters. The Framework compiles
everything to CloudFormation with least-privilege IAM roles, builds and uploads Docker images to
ECR, and supports both JavaScript and Python runtimes. No manual orchestration, no boilerplate.
New CLI commands ship alongside this integration:
-
sls invoke -a <agentName>
- invoke an agent directly, with support for JSON and SSE streaming
-
sls logs -a <agentName>
- tail or query agent logs
-
sls dev
- live dev mode for agents with hot-reload
We have included
20+ example agents
covering LangGraph workflows, MCP servers, browser automation, code interpreters, and more.
functions:
calculatorFunction:
handler: handlers/calculator.handler
ai:
tools:
calculator:
function: calculatorFunction
toolSchema:
- name: calculate
inputSchema:
type: object
properties:
expression:
type: string
required:
- expression
agents:
assistant:
memory:
expiration: 30
# Deploy the agent
sls deploy
# Invoke with streaming
sls invoke -a assistant -d "What is 2+2?"
# Tail agent logs
sls logs -a assistant --tail
S3 Files Support for Lambda File System Mounts
Docs:
File System Configuration
Lambda functions can now mount Amazon S3 Files directly as a local file system path, in addition
to the existing EFS support. This opens up a straightforward way to give your functions access to
large datasets, model weights, or shared assets stored in S3 - without downloading them at
runtime.
The Framework auto-detects the file system type from literal ARNs. For CloudFormation references,
set
type: s3files
explicitly. IAM permissions (s3files:ClientMount
and
s3files:ClientWrite) are generated automatically, and VPC configuration is validated. Existing EFS setups are fully
backward compatible.
functions:
hello:
handler: handler.hello
fileSystemConfig:
localMountPath: /mnt/s3data
arn: arn:aws:s3files:us-east-1:111:fs/fs-abc/ap-abc
vpc:
securityGroupIds: [sg-xxx]
subnetIds: [subnet-xxx]
When using CloudFormation references, specify the type explicitly:
functions:
hello:
handler: handler.hello
fileSystemConfig:
localMountPath: /mnt/s3data
arn: !GetAtt MyS3FilesAccessPoint.AccessPointArn
type: s3files
vpc:
securityGroupIds: [sg-xxx]
subnetIds: [subnet-xxx]
Faster, Smaller Framework Installs
Starting with v4.36, the Serverless Framework installer no longer fetches dependencies from npm at
install time. Everything needed ships in a single download. This makes installs faster, more
reliable (no dependency on npm registry availability), and saves approximately 42 MB of disk space
per framework version.
Existing projects require no changes. If you are on an older installer, you will pick up the
faster install path automatically the next time you update or fetch a new version. To also get the
disk space savings, run
serverless update
or reinstall the
serverless
npm package.
Python Improvements
uv dependency groups and optional extras. Four new
custom.pythonRequirements
options give you precise control over which extras and groups are included in your deployment
package, mirroring the existing Poetry group support. Dev dependencies are always excluded by
default.
custom:
pythonRequirements:
uvOptionalDependencies: # → uv export --extra <name>
- heavy
uvWithGroups: # → uv export --group <name>
- prod
uvWithoutGroups: # → uv export --no-group <name>
- test
uvOnlyGroups: # → uv export --only-group <name>
- lambda
Layer-only services now work correctly. Services that declared
custom.pythonRequirements.layer
with no
functions:
block previously produced an empty CloudFormation stack. That is fixed.
Windows ZIP path fix. ZIP archive entries are now written with POSIX-style
/
separators on every platform, resolving import mismatches at runtime for Windows users.
Improvements & Bug Fixes
Recent releases include a number of usability and reliability fixes:
-
TypeScript config deadlock resolved. Multi-file TypeScript configurations
(serverless.ts
importing other
.ts
files via relative imports) could deadlock during command startup, most reproducible in AWS
CodeBuild. Fixed in v4.36.1.
-
esbuild plugin version conflicts resolved. Projects pinning a specific
esbuild
version no longer hit
Host version does not match binary version
errors when running
serverless invoke local. Both esbuild instances now resolve their own platform binaries independently.
-
esbuild deploy fix.
sls deploy --package
no longer fails with
MISSING_ARTIFACT_FILE
when using the esbuild builder.
-
Duplicate PATH entries from installer fixed. The installer no longer appends
a new PATH line to shell config on every run.
-
AppSync field directive fixes.
@canonical,
@hidden, and
@renamed
now work correctly on field definitions in AppSync Merged API configurations.
-
Dev mode Node.js runtime matching. Dev mode now matches the remote Lambda
shim runtime to your local Node.js version instead of always defaulting to
nodejs20.x.
-
Rich TypeScript type documentation. All configuration schema properties now
include JSDoc annotations (description,
@example,
@default,
@deprecated,
@since), enabling better hover tooltips and inline docs in IDEs.
Security
This release period included a number of proactive security fixes across the Framework and its
dependencies:
-
Hardened the installer against supply chain attacks: replaced
axios,
axios-proxy-builder, and
tunnel
with Node.js built-in
fetch()
and
undici.ProxyAgent. Remaining dependencies are pinned to exact versions. A 3-day minimum release age (min-release-age=3) is now enforced via
.npmrc
to prevent npm from resolving to freshly published packages.
-
Locked transitive dependencies in distributed packages via
npm-shrinkwrap.json, pinning the full dependency tree to exact versions.
-
Patched an infinite-loop CVE in the installer runtime (CVE-2026-33814).
-
Lodash upgraded to v4.18.1, resolving prototype pollution vulnerabilities.
-
Multiple additional dependency security patches applied across
hono,
fast-xml-parser,
minimatch,
uuid,
urllib3,
follow-redirects,
fastify, and others.
The Serverless Framework is free for individuals and organizations under $2M in annual revenue.
For larger teams,
learn about our Subscription plans
or
schedule a meeting with us.
Serverless Inc - 522 San Anselmo Ave. San Anselmo CA 94960
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