fix(session): accept legacy agentName JSON key when unmarshaling Message#3483
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Adds a compatibility UnmarshalJSON so session/eval JSON exported before the agent_name tag rename (PR docker#3471) still loads the agent name. Assisted-By: Claude
…haller Decode through a pointer alias so null and partial decodes preserve stock encoding/json merge semantics. Document the empty-vs-absent precedence trade-off. Add null, empty-current-key, and end-to-end legacy session tests. Update the evaluation docs example to the canonical agent_name key. Assisted-By: Claude
docker-agent
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Jul 6, 2026
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Assessment: 🟢 APPROVE
The UnmarshalJSON implementation is correct and well-structured. The pointer-aliased type alias technique (type message Message + embedded *message) properly avoids infinite recursion while populating all Message fields in-place during unmarshal. The fallback logic (if m.AgentName == "") correctly handles both absent and explicitly-empty agent_name values. No nil-pointer risks are introduced — the *message pointer is always initialized before unmarshal. The design decision to treat empty and absent agent_name equivalently is intentional and clearly documented in the comment.
No bugs found in the introduced code.
Sayt-0
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Jul 6, 2026
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PR #3471 renamed the JSON tag on
session.Message.AgentNamefromagentNametoagent_name. However, contrary to that PR's description, Go'sencoding/jsondoes not perform case-insensitive matching betweenagentNameand a field taggedagent_name— the two differ by more than case. As a result, any previously exported session files or evaluation JSON documents that used the old key silently dropped the agent name on load.This PR adds a compatibility
UnmarshalJSONonsession.Messagethat accepts bothagentNameandagent_name. The new canonicalagent_namekey wins when both are present; decoding is done through a pointer-aliased struct to preserve the stock null-handling and field-merging semantics without recursion. Marshaling is unchanged and still emits onlyagent_name. Unit tests cover the legacy key, the new key, both keys present at once, and a realistic end-to-end legacy session document. The evaluation docs example is updated to the canonical key.No breaking changes. Existing sessions written with
agent_nameare unaffected; sessions written with the oldagentNamekey now round-trip correctly.