[Benoît Cortier (CBenoit)]

An agent reports metadata such as its host name, and an authority shows it to administrators and evaluates the friendly name from it. A value holding bidirectional overrides or zero-width characters can reorder or hide that text, so a device can disguise itself.

The Agent Identity contract now excludes a closed list of invisible format characters from metadata values (U+00AD, U+061C, U+180E, U+200B–U+200F, U+202A–U+202E, U+2060–U+2064, U+2066–U+206F, U+FEFF, U+FFF9–U+FFFB, U+E0001, U+E0020–U+E007F), and the agent removes them before sending. The list is general category Cf minus the visible marks, fixed as code points so that the agent and every authority agree whatever Unicode version their runtimes ship.

• The agent strips the listed characters from every metadata value before truncating it.
• The authority library and the mock authority refuse a value holding one with invalid_request at enroll, renew, check-in and Hello.
• The conformance suite checks the refusal, the stripping, and that code points next to the list stay accepted.

DVLS gets the rule with the next authority library package; until it takes that package, its conformance run fails the new refusal checks.

Issue: DGW-478
Issue: DGW-479
Security: yes

🤖 Generated with Claude Code

[Benoît Cortier (CBenoit)]

Evidence at 14d52792c

Check	Result
cargo +nightly fmt --all -- --check	clean
cargo clippy -p agent-identity -p agent-identity-mock -p agent-identity-conformance --all-targets -- -D warnings	clean
cargo test -p agent-identity -p agent-identity-mock -p agent-identity-conformance	185, 509 + 10 and 51 passed (1 ignored)
build.ps1 (authority library)	0 warnings
dotnet test (authority library)	2111 passed
ci/check-oracle-markers.ps1 -Base origin/master	exit 0
Conformance, mock, file key backend (Windows)	190 PASS, 0 FAIL, 1 SKIP (a_key_non_exportable needs the Windows provider), 2 N/A
Conformance through testsuite, Windows, not elevated	136 PASS, 0 FAIL; agent tests SKIP without elevation, covered by the run above

The new conformance checks (p_metadata_invisible_format_characters, the U+E007F Hello case, a_metadata_invisible_format_characters_removed) failed against the mock and agent before their changes and pass after.
The suite changes were written and reviewed from the contract only, without reading the implementations.

Notes for the reviewer

• The package version is 2026.10.28, after fix(dotnet-agent-identity)!: harden issuance and nonce retention #2164's 2026.10.27; this PR should merge after fix(dotnet-agent-identity)!: harden issuance and nonce retention #2164.
• DVLS takes the rule with the next library package; until then, its conformance run fails p_metadata_invisible_format_characters and the U+E007F Hello case.
• The closed list leaves out other invisible code points outside Cf, such as the Hangul fillers (U+115F, U+1160, U+3164, U+FFA0), U+034F and variation selectors, so a name like "admin" followed by U+3164 still looks like "admin". Widening it would be a contract change.
• UNTESTED: properties added by this PR: none.

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This comment was drafted by Claude Code (Claude Opus 5.5).