Pattern: on-disk agent session logs have become the de facto telemetry format, and four tools in six days read them

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tokentab (2026-09-07, 481 stars) computes cost from Claude Code, Codex and Gemini CLI logs; tracecrate (2026-09-10, 105 stars) is a local-first workbench that inspects Claude Code, Codex and OTLP traces and compares runs with no backend or API keys; ai-data-extractor (2026-09-11, 90 stars) extracts chat history across Claude Code, Cursor, Windsurf, Aider and Cline; Geiger (2026-09-06) inventories agents, MCP servers and plugins. None of them asks a vendor for anything. The leverage point for anyone building agent observability is the JSONL already on the machine, not a hosted API.