fix: Gate unsupported-slash-command on SDK command list

[charlesvien]

Problem

Plugin/skill slash commands like /skills-store can race with the SDK's idle event during plugin load, getting mis-flagged as "Unsupported slash command".

Changes

1. Cache SDK's command list from initializationResult().commands on the session
2. Gate "Unsupported" emission on missing-from-list, not just on no-echo
3. Helper to collect command names from SDK init response
4. Test for known-skill early-idle race
5. Document divergence in UPSTREAM.md

How did you test this?

Manually

Automatic notifications

• Publish to changelog?
• Alert Sales and Marketing teams?

[charlesvien]

• feat: update defautls #2431
• feat: add enthropic packages to exlude list #2430
• feat: Upgrade Claude adapter to SDK 0.3 with native binary #2385
• fix: Gate unsupported-slash-command on SDK command list #2425 👈 (View in Graphite)
• refactor(auto-title): Untangle auto-title generator #2428
• refactor(auto-updater): Introduce state machine and guard staged updates #2427
• main

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[greptile-apps]

T-Rex Logs

What T-Rex did

• Ran a focused vitest harness to exercise the early-idle slash-command gate with a mocked Claude query.
• Verified that the MCP command name shape used by the SDK matches the command name sent by ACP clients.
• Reproduced a real MCP command scenario that produced an 'Unsupported slash command: /mcp:github-search' and ended the turn.
• Added a sanity case for leading-slash command entries to confirm the bare-name contract.
• Read gating changes in claude-agent.ts (early-idle branch + collectKnownSlashCommands) and the MCP rename in session/commands.ts, then wrote a focused vitest test to drive the real prompt() loop with a mocked Query and emit only session_state_changed{state:idle}.
• Installed dependencies and built @posthog/enricher so vitest could resolve its dist.
• Ran the vitest test with verbose output; one case failed as designed, producing the spurious 'Unsupported slash command: /mcp:github-search' chunk.
• Validated a second test case where a set containing /help with a leading slash confirms that command names must be bare.
• Attached the automated repro as validation for manual review.

Artifacts

Verbose vitest output for the failing MCP-prefix repro

• Shows the verbose vitest run used to reproduce the MCP-prefix failure for review.

Generated focused repro test

• The focused repro test file that exercises the MCP command shape regression.

Verbose vitest output with stack trace for the failing MCP-prefix case

• Contains the stack-trace rich run of the failing case from the automated repro.

Focused repro TypeScript test file

• The focused TypeScript test source file created for the MCP path.

_{Ran code and verified through T-Rex}

Comments Outside Diff (1)

1. packages/agent/src/adapters/claude/claude-agent.ts, line 992-1001 (link)

   Refresh command cache

   refreshSession() waits for the new query's initializationResult(), but it never copies result.value.commands into session.knownSlashCommands. After MCP or skill servers are refreshed, the available-command update can show newly available commands while the early-idle gate still uses the old Set. A newly added command can still be reported as unsupported, and a removed command can remain treated as known and fall through to the failure path instead of producing the intended unsupported-command message.

   Prompt To Fix With AI

   This is a comment left during a code review.
   Path: packages/agent/src/adapters/claude/claude-agent.ts
   Line: 992-1001
   
   Comment:
   **Refresh command cache**
   
   `refreshSession()` waits for the new query's `initializationResult()`, but it never copies `result.value.commands` into `session.knownSlashCommands`. After MCP or skill servers are refreshed, the available-command update can show newly available commands while the early-idle gate still uses the old Set. A newly added command can still be reported as unsupported, and a removed command can remain treated as known and fall through to the failure path instead of producing the intended unsupported-command message.
   
   How can I resolve this? If you propose a fix, please make it concise.

Prompt To Fix All With AI

Fix the following 2 code review issues. Work through them one at a time, proposing concise fixes.

---

### Issue 1 of 2
packages/agent/src/adapters/claude/claude-agent.ts:147-155
**Normalize MCP command names**

`collectKnownSlashCommands` stores the SDK command name verbatim, but MCP commands are exposed to ACP clients with a different name shape. `getAvailableSlashCommands` turns an SDK name like `github:search (MCP)` into `mcp:github:search`, and `promptToClaude` later transforms `/mcp:github:search ...` back before sending it to the SDK. During an early idle, this lookup compares the captured command name against the raw SDK name in the Set, so a real MCP command can miss the gate and emit `Unsupported slash command` even though the SDK supports it. Store the same user-facing alias used by `getAvailableSlashCommands`, or store both forms.

### Issue 2 of 2
packages/agent/src/adapters/claude/claude-agent.ts:992-1001
**Refresh command cache**

`refreshSession()` waits for the new query's `initializationResult()`, but it never copies `result.value.commands` into `session.knownSlashCommands`. After MCP or skill servers are refreshed, the available-command update can show newly available commands while the early-idle gate still uses the old Set. A newly added command can still be reported as unsupported, and a removed command can remain treated as known and fall through to the failure path instead of producing the intended unsupported-command message.

_{Reviews (1): Last reviewed commit: "Gate unsupported-slash-command on SDK co..." | Re-trigger Greptile}

[k11kirky]

bit of a trust you bro stamp on this one

[k11kirky]

Merge activity

• May 29, 10:26 AM UTC: A user started a stack merge that includes this pull request via Graphite.
• May 29, 10:37 AM UTC: Graphite rebased this pull request as part of a merge.
• May 29, 10:44 AM UTC: @k11kirky merged this pull request with Graphite.