# xet resource URI delivery milestones Date: 2026-10-24. Status: **scheduled scope; no implementation completed**. [ADR 0009](../../adr/0009-xet-resource-uris.md) accepts the name and endpoint boundary. [Product design ยง12](../specs/2026-10-23-openxet-design.md#12-milestones-v1--all-of-them) is the authoritative milestone schedule. This handoff records the work that the future M2 and M6 implementation plans must include; it is not a complete implementation plan for either milestone. No separate M2/M6 plan exists yet. ## M2-URI: define resource addressing after Hub naming **Dependency:** the M2 Hub work defines namespaces, repository kinds, paths, revisions, authorization and HTTPS resolution. Establish those contracts before finalizing URI syntax. The fixed choice is `xet://` with the real host and optional port in the authority; hosted and self-hosted use identical semantics. Deliver a reviewed URI specification, the legacy compatibility decision, and one shared Rust parser/canonical formatter for later client bindings. Write the implementation plan with dependency order and file ownership before coding. Do not make the parser depend on a running hosted service. Acceptance checks: - The specification defines resource kinds, mutable and immutable references, escaping, Unicode, ports/IPv6, HTTPS mapping, reverse-proxy prefixes and local development behavior. An exported address never resolves through a recipient's default server or a local alias. The name is settled; the remaining grammar is reviewed here rather than inferred from an illustrative example. - Audit pinned legacy Git-Xet and pyxet parsers and fsspec registration. Publish a matrix of accepted, translated and rejected forms, with actionable errors. Test ambiguous legacy inputs explicitly; never silently send them to a different deployment. Record coordination and IANA registration work without implying that either has already happened. - Golden vectors and parser/formatter round-trip properties cover the approved grammar and malformed inputs; fuzz all untrusted parsing. Include Unicode, percent-encoding, separator/ref ambiguity and endpoint normalization cases. - Two distinct endpoint fixtures contain the same resource names but different content. Resolution selects the URI's endpoint and preserves resource scope. Credential-isolation tests reject credentials embedded in URIs, prevent use of the default endpoint's token on another host and prevent redirect leakage. - Preserve the existing HTTPS/stock-client contracts and storage-only hash-based CLI behavior. Unsupported resource kinds fail clearly; this task does not bring M5's bucket primitive forward into M2. M2 completion supplies the reviewed contract and parser, not a claim that all third-party tools accept `xet://` or that public hosted accounts exist. ## M6-URI: deliver the same address through clients and UI **Dependencies:** M2-URI, the M6 client command/API shapes and the resource kinds implemented by the preceding milestones. Reuse the shared parser in the CLI, Rust SDK and Python bindings. Provide an explicit fsspec integration with a tested coexistence policy for legacy handlers; do not silently replace them. Acceptance checks: - CLI and SDK upload/download round trips use `xet://` against two independently addressed deployments of the released server. Identical names cannot cross endpoints. Test the same paths against the hosted staging deployment before enabling hosted URI copy actions; self-hosting gets no reduced capability. - Exercise the real Python/fsspec adapter and a supported consuming library, with pinned versions. List native DuckDB/polars and stock Hugging Face support separately. Run unchanged stock clients against the existing HTTP/Hub path; never claim that adding our parser changes their recognized schemes. - `sync`, `mount` and other resource-taking commands use the shared contract as they ship; write actions require the command's normal authorization. Merely opening a URI cannot upload, delete or execute anything. - Publish runnable CLI/SDK recipes, versioned JSON/error examples, retry and migration guidance, and the same canonical Markdown for agents. Errors expose the endpoint/resource safely without printing credentials. - UI copy actions distinguish **Copy resource URI** from **Copy web link**. HTTPS remains the canonical browser/share link. Both actions exclude secrets, work by keyboard and provide an accessible result/fallback. Show the resolved endpoint and revision when a human approves an agent's separate write action. OS/browser protocol-handler registration is a separate feature; it is not implied by CLI support and is not required to finish this work package. ## M7: publish the tested contract Ship the URI specification, support matrix and migration notes with the client distribution. Verify packaged CLI/SDK versions execute the published recipes. Record registration status accurately; a chosen name is not an IANA registration or a claim to own the Xet wire protocol. Until these paths ship, marketing and quickstarts retain released commands and HTTPS links.