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lbliii 3 min read 531 words Updated 6 days ago

Milo 0.4.0

Truthful cross-surface dispatch, MCP Apps, downstream CLI adoption, and host-owned Context.

Feature release focused on making one typed function a truthful, composable contract for terminal users, Python hosts, and MCP clients.

Highlights

  • Truthful dispatch everywhere — Generated schemas are enforced across CLI, call, call_raw, and MCP. Unknown arguments and constraint failures now carry stable, repairable diagnostics instead of reaching handlers or being silently discarded.
  • MCP Apps end to end — Typedui://resources, tool links, capability negotiation, gateway-safe URI rewriting, resource transport, verifier checks, and a dependency-free interactive example now form one tested contract.
  • Downstream CLI adoption — Public positional and option presentation, command surface policy, lazy version reports, terminal renderers, shallow help, and selected-command parsing support established CLIs without private argparse mutation.
  • Headless Context — Web servers, workers, and tests can inject their own output sink, interaction policy, and approval strategy while terminal defaults remain unchanged.
  • Launch-ready onboarding — The README now leads with a clean-machine 60-second CLI-to-MCP proof, backed by stricter verifier coverage and honest Milo/FastMCP/Typer guidance.

Added

  • Publicvalidate_arguments()enforcement and complete lazy exports for runtime effect types.
  • Positional, Option, per-command surfaces, custom version reports, and terminal-only structured-result rendering.
  • MCP Apps resource/tool metadata types, negotiated discovery, security metadata, gateway routing, and stable structured errors.
  • mcp_apps_in_process, mcp_apps_gateway, and mcp_apps_transportverifier checks, including subprocess resource reads and clean-stdout validation.
  • OutputSink, ConfirmStrategy, NullOutputSink, and host ctx=injection for programmatic command calls.
  • MCPserver/discoverand explicit unsupported-version diagnostics for stateless negotiation preparation.

Changed

  • Root and group help use command registration metadata without resolving lazy leaf schemas. Selected command execution builds only that command path.
  • CLI.root_option_specs()is the shared immutable source for built-in and user-defined root option metadata.
  • The public docs, launch runbook, comparison guide, and framework-neutral examples now lead with verified dual CLI/MCP workflows.

Fixed

  • CLI, programmatic, and MCP dispatch now agree on schema constraints, unknown arguments, middleware repair, hidden commands, lazy-import failures, and protocol-safe hook errors.
  • Gateway failures preserve structured child repair data and MCP Apps links survive collision-safe namespacing and resource reads.
  • Bundled terminal components align by display-cell width and preserve wide Unicode; panel border styles render through the documented contract.
  • Testing helpers reject incomplete saga traces and expose structured MCP repair data; example reducers remain deterministic and replayable.
  • Onboarding, generated-project, help, form, platform-path, and version-check documentation now matches the executable public surfaces.

Compatibility Notes

  • Python 3.14+ and the pure-Pythonkida-templates>=0.9.0,<0.10.0runtime dependency are unchanged.
  • No public command flag was removed. Context fields were appended to the frozen dataclass, and default stderr, TTY, and terminal confirmation behavior is preserved.
  • Code that relied on silently ignored programmatic or MCP arguments must remove them or update the command signature. This is an intentional contract correction: agent calls now receiveM-INP-005repair data.
  • MCP clients cannot invoke hidden commands and cannot injectctx; both now fail with structured errors consistent with discovery.

Downstream Adoption

This is the first released version containing the generic contracts required by the versioned Chirp CLI canary. Downstream integrations should pinmilo-cli 0.4.x and advance the supported range only after their CLI, structured output, MCP, llms.txt, and lazy-startup parity lanes pass.