docs: report SubWorker cwd attachment-root ambiguity

2026-10-05 18:10:01 +09:00
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+# SubWorker cwd attachment-root ambiguity during T-697
+
+## Observed barrier
+
+A delegated backend investigation was spawned with `cwd=crates/workspace-server`
+and explicit writable rules for both `crates/workspace-server` and
+`crates/server-api`, plus repository-root read access. The child reported that
+its available attachment exposed only the workspace-server crate; its observed
+file reads used `src/server.rs`/`src/lib.rs` and it could not access server-api.
+It also had no `ShowTicket` or parent-notification tool, despite the parent
+having typed Ticket authority. No implementation changes were made by that child.
+
+The parent inspected the committed child session, released the idle child, and
+respawned at the repository root with the same delegated write boundaries and
+an explicit summary of the authoritative Ticket requirements. That child could
+then implement the cross-crate API boundary. No filesystem capability rejection
+was worked around through another write path.
+
+## Suggested improvement
+
+The advertised SubWorker `cwd` contract says that it changes only the tool
+working directory, not attachment roots. Show the effective attachment aliases,
+logical roots and readable/writable scopes explicitly to the child and parent,
+and test cross-crate reads/writes for a non-root cwd. If cwd intentionally
+narrows or rebases an attachment, document that instead of presenting it as
+only a command default. A denied/inaccessible sibling diagnostic should identify
+the effective logical attachment root without disclosing unauthorized paths.
+
+Also expose which typed domain and parent-messaging tools will be available
+before spawning. Delegated implementation requires authoritative requirements;
+where Ticket reads are unavailable, the parent must deliberately provide the
+bounded contract rather than assume the child can recover it by ID. This report
+records tool ergonomics only; it is not a new T-697 product requirement.