{"type":"post","id":"open-sourced-mirror-cli-the-rust-core-agent-6deb32","slug":"open-sourced-mirror-cli-the-rust-core-agent-6deb32","title":"Open-sourced Mirror CLI , the Rust-core agent harness Beam was trained on.","description":"Thesis: Mirror CLI makes the coding-agent harness, rather than the model alone, the operational surface developers must understand.","retrieval_nugget":"Thesis: Mirror CLI makes the coding-agent harness, rather than the model alone, the operational surface developers must understand.","published_at":"2026-10-16","updated_at":"2026-10-16","record_date":"2026-10-16","date_kind":"published_at","topics":["agent-harness"],"source_urls":["https://developers.reflection.ai/mirror-overview"],"schema_version":"newruntime-agent-readable-v0.2","stable_id":"post:open-sourced-mirror-cli-the-rust-core-agent-6deb32","status":"published","visuals":[],"editorial_provenance":{"schema_version":"newruntime-editorial-copy-v1","content_status":"source_grounded_final","final_copy_sha256":"sha256:9de9d03efcc17b58f93f035db13d68f2165cfdf5140aed884843ed14ce03202b","reviewed_at":"2026-10-16T23:04:31.389Z","source_evidence_count":1,"verified_claim_count":4,"site_analysis_schema_version":"newruntime-site-analysis-v1","site_object_kind":"field_note","observed_fact_count":4,"implication_count":1,"watch_condition_count":1,"related_record_count":0},"analysis":{"schema_version":"newruntime-site-analysis-v1","object_kind":"field_note","thesis":"Mirror CLI makes the coding-agent harness, rather than the model alone, the operational surface developers must understand.","observed_facts":[{"text":"Reflection’s developer documentation identifies Mirror as a terminal coding agent in early beta.","source_urls":["https://developers.reflection.ai/mirror-overview"]},{"text":"The documentation says Mirror uses Reflection and Beam-1.0-501B-A23B by default.","source_urls":["https://developers.reflection.ai/mirror-overview"]},{"text":"Manual mode pauses before shell commands, file edits, connected-service tools, and most extension tools.","source_urls":["https://developers.reflection.ai/mirror-overview"]},{"text":"Reflection warns that approval mode is not a sandbox and approved tools run with the user’s account permissions.","source_urls":["https://developers.reflection.ai/mirror-overview"]}],"mechanism":"The approval setting governs when Mirror pauses for user review, while tools execute with the permissions of the user’s machine account.","why_now":"the public beta makes these operating boundaries concrete for teams deciding how to trial an agent in real project directories.","implications":["teams should treat permission design and review of agent changes as workflow decisions, not assume the approval toggle isolates execution."],"evidence_boundary":"this assessment relies on Reflection’s product documentation, which says commands and behavior may change during early beta.","watch_conditions":["whether later releases add a sandbox boundary or otherwise change how tools inherit local permissions would materially alter this assessment."],"related_records":[],"new_branch_reason":"No prior New Runtime record is supplied for this specific Reflection Mirror CLI beta release, so this begins a distinct analytical record."},"editor":{"role":"editor","name":"Andrey Reshetnikov","profile":"https://newruntime.com/owner-profile.md","profile_json":"https://newruntime.com/owner-profile.json","same_as":["https://www.linkedin.com/in/reshetnikov1/","https://t.me/lapetuse"]},"routes":{"html":"https://newruntime.com/posts/open-sourced-mirror-cli-the-rust-core-agent-6deb32/","markdown":"https://newruntime.com/posts/open-sourced-mirror-cli-the-rust-core-agent-6deb32.md","json":"https://newruntime.com/posts/open-sourced-mirror-cli-the-rust-core-agent-6deb32.json"},"related_patterns":["harness-architecture-outlives-model-choice"],"next_reads":[{"type":"topic","path":"/topics/agent-harness/","url":"https://newruntime.com/topics/agent-harness/","title":"Agent Harness","reason":"Explore the agent-harness topic hub.","media_type":"text/html","markdown_url":"https://newruntime.com/topics/agent-harness.md","json_url":"https://newruntime.com/topics/agent-harness.json"},{"type":"collection","path":"/posts/","url":"https://newruntime.com/posts/","title":"Field Notes","reason":"Open the latest editorial analysis.","media_type":"text/html","json_url":"https://newruntime.com/posts.json"},{"type":"collection","path":"/source-ledger.json","url":"https://newruntime.com/source-ledger.json","title":"Source Ledger","reason":"Inspect the public source evidence graph.","media_type":"application/json"}]}