[teamleaderleo]

Follow-up 1 of #35652, from the Codex review that gave SHIP on #34604.

What it fixes

When a machine's identify answer succeeds but its capabilities are missing or not a list, fetch_served read it as Some(false): "this machine serves no blob fetch". The push then skipped the fence, so an older blob.fetch job still running there could commit files over what this push writes. A missing list says nothing about what the machine serves, so it is now None, and the push takes fence_unknown (the path already used when identify does not answer at all). A machine whose list is present and lacks blob-fetch-v2 is still Some(false), unchanged.

The decision is pulled out of fetch_served into serves_fetch(&Value) so it can be tested without a socket.

Test

cargo test -p cmux-tui --lib an_identify_answer_without_capabilities (hosted, ./scripts/verify-cmux-tui-hosted.sh --filter):

• Red on the test-only commit b2e3c83 (run 41878360641): left: Some(false), right: None.
• Green on the head: the hosted run for link::sync_cli::store (result in a comment below).

Observed / Not run

• Observed: the red above, from the hosted run's log.
• Not run: the link_sync_store end-to-end test, which has no fixture for an identify answer without capabilities. This change only affects that case.

risk: low (one branch of a capability check, toward the cautious path).

Changelog

none

Agent session: agent session

🤖 Generated with Claude Code

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Summary by cubic

Fences a push when a machine's identify succeeds but its capabilities are missing or not a list, closing a window where an older blob.fetch job could still commit files over the push's writes.

Previously a missing or non-list capabilities field was read as Some(false) ("serves no blob fetch") and the push skipped the fence. It now reads as None and the push takes fence_unknown, the same path used when identify does not answer at all. A present list that lacks blob-fetch-v2 is still Some(false), unchanged.

The capability check is pulled out of fetch_served into serves_fetch(&Value) so it can be tested without a socket, with a new unit test covering the missing, malformed, and present-list cases.

^{Written for commit 05d95d5. Summary will update on new commits.}

[github-actions]

cmux status _{(one comment, edited in place; each line is updated by the job that owns it)}

Review 05d95d5: HQ feed card · gallery before/after runs · checks

App of this head (app.zip, kept 1 day)

gh workflow run reload-build.yml -R manaflow-ai/cmux --ref feat-cmux-next -f tag=pr35799 -f ref=blob-sync-fence-unknown-caps -f platform=macos -f backend_mode=local

Shipped in:

• cmux NEXT nightly 1.0.0-nightly.4190094575701 (036f8aa538)
• cmux NEXT nightly 1.0.0-nightly.4191131679101 (e01bbae5c9)

[teamleaderleo]

Owned by an agent session · session

[teamleaderleo]

Review (codex, router-review): SHIP at 05d95d5

Reviewer: codex gpt-6.1-sol xhigh, fast tier.

SHIP at 05d95d5

Visual verdict: unchanged by this diff

The capability parsing and fence dispatch match the stated behavior; no correctness findings.

Follow-ups: none

[blacksmith-sh]

Found 1 test failure on Blacksmith runners:

Failure

Test	View Logs
test_every_listed_hook_is_one_glaeda_released_with_the_check (main.SigningHooksInSt epWithGlaedaTests.test_every_listed_hook_is_one_glaeda_released_with_the_check)/ test_every_listed_hook_is_one_glaeda_released_with_the_check (main.SigningHooksInSt epWithGlaedaTests.test_every_listed_hook_is_one_glaeda_released_with_the_check)	View Logs

^{Need help on this PR? Tag @codesmith-bot with what you need.}

[cmux-bot]

cmux-bot approves 05d95d5: an independent review passed this exact head (router-review receipt by teamleaderleo). A push needs a new review; a later BLOCK at this head dismisses this approval.