Standardize gateway JSONL records with event/_schema and millisecond timestamps

[Copilot]

MCP Gateway logs had mixed record semantics (type used for both direction and record kind), no schema discriminator, and inconsistent timestamp precision across JSONL vs text logs. This change aligns gateway logs to the AWF-style base contract so cross-log parsing and aggregation can use one shape.

• JSONL contract normalization (RPC + DIFC)

  • JSONLRPCMessage now emits:
    • timestamp (ISO 8601 UTC with milliseconds)
    • event (rpc_request / rpc_response)
    • _schema (rpc-message/v2)
  • JSONLFilteredItem now emits:
    • timestamp (same format)
    • event: "difc_filtered"
    • _schema: "difc-filtered/v2"
  • Removed overloaded type from JSONL records in favor of event.

• Timestamp consistency across logs

  • Unified text log formatter (mcp-gateway.log and {serverID}.log) now uses the same millisecond-precision UTC layout as JSONL.

• Parser/spec updates for downstream consumers

  • Updated in-repo workflow/spec docs that parse rpc-messages.jsonl to match the new discriminator (event == "difc_filtered"), including Repo Assist and DIFC audit/smoke workflows.
  • Updated top-level logging docs to explicitly document required JSONL fields and schema versions.

• Test updates for schema and format expectations

  • Adjusted logger/MCP tests to assert event, _schema, and millisecond timestamp parsing instead of legacy type values.

type JSONLRPCMessage struct {
    Timestamp string `json:"timestamp"` // 2006-01-02T15:04:05.000Z07:00
    Event     string `json:"event"`     // rpc_request | rpc_response
    Schema    string `json:"_schema"`   // rpc-message/v2
    Direction string `json:"direction"` // IN | OUT
    // ...
}

[Copilot]

Pull request overview

This PR standardizes the MCP Gateway’s machine-readable JSONL logging contract (RPC + DIFC) by introducing explicit event and _schema discriminators and aligning timestamps (JSONL + text logs) to a consistent UTC ISO-8601-with-milliseconds format, enabling downstream parsers/aggregators to rely on a single record shape.

Changes:

• Replaced overloaded JSONL type fields with event and added _schema versioning for RPC and DIFC-filter records.
• Unified timestamp formatting across JSONL and text logs to millisecond-precision UTC.
• Updated in-repo workflows/docs/tests to parse and assert the new JSONL fields (event, _schema) and timestamp layout.

Show a summary per file

File	Description
README.md	Documents the updated logging contract and timestamp format.
internal/server/difc_log.go	Updates DIFC log comment to reflect difc_filtered event naming.
internal/mcp/connection_logging_test.go	Updates MCP connection logging test assertions to event/_schema.
internal/logger/rpc_logger.go	Adds RPCMessageType.JSONLEvent() mapping to standardized event strings.
internal/logger/rpc_logger_test.go	Updates RPC logger tests to assert event/_schema.
internal/logger/jsonl_logger.go	Implements JSONL record shape changes and millisecond timestamp formatting.
internal/logger/jsonl_logger_test.go	Updates JSONL logger tests for new fields and timestamp parsing.
internal/logger/common.go	Updates text log timestamp formatting to millisecond layout.
internal/logger/common_test.go	Updates log line format tests for millisecond timestamps and parsing.
.github/workflows/smoke-proxy-github-script.md	Updates DIFC event counting to match event:"difc_filtered".
.github/workflows/smoke-proxy-github-script.lock.yml	Mirrors the smoke workflow update in the compiled/locked workflow.
.github/workflows/smoke-proxy-github-script.invalid.yml	Mirrors the smoke workflow update in the generated invalid fixture.
.github/workflows/repo-assist.md	Updates JSONL parsing logic to use event == difc_filtered.
.github/workflows/integrity-filtering-audit.md	Updates audit guidance/greps to match the new JSONL discriminator.

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• Files reviewed: 14/14 changed files
• Comments generated: 2

[lpcox]

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