strands-agents/sdk-python v1.22.0 on GitHub

Major Features

MCP Resource Operations - PR#1117

The MCP client now supports resource operations, enabling agents to list, read, and work with resources provided by MCP servers. This includes static resources, binary resources, and parameterized resource templates.

from strands.tools.mcp import MCPClient

with MCPClient(server_transport) as client:
    # List available resources
    resources = client.list_resources_sync()
    for resource in resources.resources:
        print(f"Resource: {resource.name} at {resource.uri}")
    
    # Read a specific resource
    content = client.read_resource_sync("file://documents/report.txt")
    text = content.contents[0].text
    
    # List resource templates (parameterized resources)
    templates = client.list_resource_templates_sync()
    for template in templates.resourceTemplates:
        print(f"Template: {template.uriTemplate}")

Bedrock Guardrails Latest Message Option - PR#1224

Bedrock models now support the guardrail_latest_message parameter, which sends only the latest user message to AWS Bedrock Guardrails for evaluation instead of the entire conversation history. This reduces token usage and enables conversation recovery after guardrail interventions.

from strands.models.bedrock import BedrockModel

model = BedrockModel(
    model_id="us.anthropic.claude-sonnet-4-20250514-v1:0",
    guardrail_id="your-guardrail-id",
    guardrail_version="DRAFT",
    guardrail_latest_message=True  # Only evaluate the latest user message
)

See the Bedrock Guardrails documentation for more details.

LiteLLM Non-Streaming Support - PR#512

The LiteLLM model provider now correctly handles non-streaming responses, fixing an issue where stream=False would raise an error. Both streaming and non-streaming modes now work seamlessly.

from strands.models.litellm import LiteLLMModel

# Use non-streaming mode for simpler response handling
model = LiteLLMModel(
    model_id="gpt-3.5-turbo",
    params={"stream": False}
)

# Works correctly now - no more ValueError
agent = Agent(model=model)
result = agent("What is 2+2?")

Major Bug Fixes

Concurrent Agent Invocations - PR#1453
Fixed critical agent state corruption when multiple concurrent invocations occurred on the same agent instance. A new ConcurrencyException is now raised to prevent concurrent invocations and protect agent state integrity.
Gemini Empty Stream Handling - PR#1420
Fixed UnboundLocalError crash when Gemini returns an empty event stream by properly initializing variables before the stream loop.
Deprecation Warning on Import - PR#1380
Fixed unwanted deprecation warnings appearing when importing strands by using lazy __getattr__ to emit warnings only when deprecated aliases are actually accessed.

What's Changed

docs: update github agent action to reference S3_SESSION_BUCKET by @dbschmigelski in #1418
feat: provide extra command content as the the prompt to the agent by @zastrowm in #1419
[FEATURE] add MCP resource operations in MCP Tools by @xiehust in #1117
fix: import errors for models with optional imports by @mehtarac in #1384
add BidiGeminiLiveModel and BidiOpenAIRealtimeModel to the init by @mehtarac in #1383
bidi - async - remove cancelling call by @pgrayy in #1357
feat(bedrock): add guardrail_latest_message option by @aiancheruk in #1224
fix(gemini): UnboundLocal Exception Fix by @emattiza in #1420
fix! Litellm handle non streaming response fix for issue #477 by @schleidl in #512
feat(agent-interface): introduce AgentBase Protocol as the interface for agent classes to implement by @awsarron in #1126
ci: update pytest requirement from <9.0.0,>=8.0.0 to >=8.0.0,<10.0.0 in the dev-dependencies group by @dependabot[bot] in #1161
feat: pass invocation_state to model providers by @tirth14 in #1414
Add Security.md file by @yonib05 in #1454
chore: Update release notes sop by @zastrowm in #1456
fix(integ): make calculator tool more robust to LLM output variations by @cagataycali in #1445
fix: resolve string formatting error in MCP client error handling by @cagataycali in #1446
bidi - move 3.12 check to nova sonic module by @pgrayy in #1439
ci: update sphinx requirement from <9.0.0,>=5.0.0 to >=5.0.0,<10.0.0 by @dependabot[bot] in #1426
fix: add concurrency protection to prevent parallel invocations from corrupting agent state by @zastrowm in #1453
fix(mcp): propagate contextvars to background thread by @cagataycali in #1444
Update to opus 4.5 by @Unshure in #1471

New Contributors

@aiancheruk made their first contribution in #1224
@emattiza made their first contribution in #1420
@schleidl made their first contribution in #512
@tirth14 made their first contribution in #1414

Full Changelog: v1.21.0...v1.22.0