[dotnet-port-fixes] fix: preserve null session state values

[microsoft-agent-framework-for-go]

Summary

Preserve explicit JSON null session values during Go Session round trips. The internal unmarshal path now decodes state entries as raw JSON before wrapping them, so a null entry remains a readable state key and can be overwritten instead of becoming a nil internal pointer.

Ported .NET PRs

Ported the fix intent from .NET commit d0ccaa62761ec36c59c139940797978623fb630a, verified as present at pinned upstream SHA 40763bed1a5e94a1698ba9ebf009e5622eb099aa: source change and regression tests. The complete upstream change was classified as fix-only: no exported API, option, default, or capability change.

The other deeply inspected candidate, .NET commit 763887452f371d8d03a67993ec7adcd95a0e18c2, was excluded because it targets .NET AI-context decorators owning IAsyncEnumerator instances; the Go counterpart uses iterator-based context-provider middleware and has no established corresponding enumerator-owning path.

Focused duplicate searches were repeated before publication with these exact queries: issue repo:microsoft/agent-framework-go session null state JSON roundtrip and PR repo:microsoft/agent-framework-go Session UnmarshalJSON stateValue null. Both returned no results.

Breaking Changes

No. This preserves existing public APIs and corrects deserialization of an existing serialized value.

Tests and Examples

gofmt -w agent/session.go agent/session_test.go

go test ./agent

git diff --check

Added TestSession_UnmarshalJSON_NullStateValueRoundtripsAndCanBeOverwritten, covering public Set → json.Marshal → json.Unmarshal behavior and subsequent overwrite.

Notes

The fix changes only agent/session.go and agent/session_test.go. Publication is queued from branch dotnet-port-fix-session-null-roundtrip; no binaries or build artifacts are included.

Warning

Firewall blocked 3 domains

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network:
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Generated by .NET to Go Fixes and Test Porting Agent · copilot · gpt56 · 3.45 AIC · ⌖ 0.82 AIC · ⊞ 24.8K · ◷

[github-actions]

API consistency review

Result	Scope
aligned	user-visible behavior

Changed Go contract

agent.Session.UnmarshalJSON (in agent/session.go) now decodes each session-state entry as json.RawMessage before wrapping it in *stateValue, instead of unmarshaling directly into map[string]*stateValue. No exported type, method signature, or field changed; Session.Get/Session.Set/MarshalJSON are unaffected.

Upstream evidence reviewed

Implementation	Source	Contract checked
.NET	AgentSessionStateBagValueJsonConverter.cs (fix commit d0ccaa6)	HandleNull => true ensures the converter's Read runs for a JSON null state entry instead of the deserializer short-circuiting to a null AgentSessionStateBagValue
.NET	AgentSessionStateBagTests.cs	SerializeDeserialize_WithNullValue_Roundtrips / _CanOverwrite assert the null key survives roundtrip and remains settable/overwritable afterward

Assessment

Before this fix, Go's map[string]*stateValue unmarshaled a JSON null entry as a nil *stateValue pointer (confirmed by reproduction: Session.Get on such a key panicked via nil-pointer dereference in stateValue.readInto), diverging from .NET's HandleNull-gated converter, which always constructs a valid AgentSessionStateBagValue wrapping a JSON null element. The PR's raw-message decoding path ensures every state entry — including explicit nulls — becomes a valid, non-nil *stateValue{raw: "null"}, matching .NET's roundtrip-and-overwrite semantics verified above. This is a pure bug fix with no public API or default change (verified by go build ./... and go test ./agent/... passing, plus manual reproduction of the pre-fix panic).

Warning

Firewall blocked 3 domains

The following domains were blocked by the firewall during workflow execution:

• proxy.golang.org
• storage.googleapis.com
• sum.golang.org

To allow these domains, add them to the network.allowed list in your workflow frontmatter:

network:
  allowed:
    - defaults
    - "proxy.golang.org"
    - "storage.googleapis.com"
    - "sum.golang.org"

See Network Configuration for more information.

Generated by Go API Consistency Review Agent for #1267 · copilot · auto · 62.1 AIC · ⌖ 6.33 AIC · ⊞ 13.9K · ◷

[Copilot]

🟢 Approval recommended

The focused implementation matches the intended behavior and includes adequate regression coverage.

0 open findings

What changed in this PR

Preserves explicit JSON null values in session state across serialization round trips.

Changes:

• Decode state entries as raw JSON before wrapping them.
• Add regression coverage for reading and overwriting null values.

File	Description
agent/​session.go	Preserves null state entries as non-nil wrappers.
agent/​session_test.go	Tests null round trips and replacement.

🧠 Review effort: Balanced

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