chore(release/candidate): release 1.28.1

[Jacksunwei]

🤖 I have created a release beep boop

1.29.0 (2026-04-02)

Features

• Add support for model endpoints in Agent Registry (eb4674b)
• auth: Pass consent_nonce to Agent Frontend (9fec503)
• auth: Support additional HTTP headers in MCP tools (b3e9962)
• bigquery: Add ADK 1P Skills for ADK BQ Toolset (4030c0d)
• environment: Add EnvironmentToolset for file I/O and command execution (9082b9e)
• environment: Add LocalEnvironment for executing commands and file I/O locally (f973673)
• live: support live for gemini-3.1-flash-live-preview model (8082893)
• Option to use shallow-copy for session in InMemorySessionService (16a1a18)
• Remove use of raw_event field in vertex ai session service (642d337)
• Support AgentRegistry association (6754760)
• Support propagating grounding metadata from AgentTool (d689a04)
• Use raw_event field in vertex ai session service for append and list events (6ee0362)

Bug Fixes

• add httpx_client_factory support to SseConnectionParams (815ebb4)
• adk: redact credentials in BigQuery analytics plugin (a27ce47)
• api client initialization logic to be mutually exclusive between ExpressMode and GCP projects (4ffe8fb)
• Cache BaseToolset.get_tools() for calls within the same invocation (92cad99)
• Disallow args on /builder and Add warning about Web UI usage to CLI help (dcee290)
• Enhance ADK release analyzer with resume functionality and better session management (5f69e19)
• environment: fix package references (add8e86)
• Fix RemoteA2AAgent deepcopy errors (6f29775)
• Generate IDs for FunctionCalls when processing streaming LLM responses (fe41817), closes #4609
• Handle merging lists in deep_merge_dicts (cdb3ff4)
• In memory session service to evaluate dictionary keys and value into an isolated snapshot sequence before starting loop (f75de59)
• include intermediate subagent final response events in evaluation intermediate data (f8a6bd7)
• live: Buffer tool calls and emit them together upon turn completion (7fa13ed)
• Safer fix for UI widget merging in ADK (0e71985)
• sync callbacks with call_llm span (b2daf83)
• tools: handle toolset errors gracefully in canonical_tools (5df03f1), closes #3341
• update toolbox-adk and toolbox server versions (1486925)
• Update v2 release workflow to be dispatched from v2 branch (446575f)

Code Refactoring

• Move SecretManagerClient to google.adk.integrations.secret_manager package (1104523)
• Remove the session events dependency from A2aAgentExecutor (aaa03ac)

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