[code-yeongyu]

Part of #4329
Part of an error-guidance audit tracked internally

Summary

Three of the remaining failure texts from #4329 now name the cause class and one next step that works on every surface (TUI, RPC, desktop). No string that code matches on was changed.

1. Provider is not configured. agent_end.failure used to report the local auth-miss sentinel as unknown with a resend step, which cannot help because no request was sent. It now reports auth, with a reason naming the provider and an action to connect it (sign in or add an API key) or choose another model. httpStatus and code are absent. PROVIDER_NOT_CONFIGURED_PREFIX and providerNotConfiguredMessage are unchanged (packages/coding-agent/src/core/provider-failure.ts notConfiguredFailure).

2. No credential slots available. The due-back time is now local time with its zone, followed by the ISO instant in parentheses (the goal's providerRetryAt wake and turn-end liveness scan the text for it), then one step: wait until that time, or sign in again / add a new key when no slot comes back on its own (account_disabled, empty pool). The No credential slots available prefix and the typed CredentialFailoverError.retryAt are unchanged (credential-pool/failover.ts noSlotsMessage). AllSlotsBlockedError follows the same rule; soonestUnblockAt is unchanged.

3. Compaction failed / Auto-compaction failed / Context overflow recovery failed. core/compaction-failure-text.ts builds every compaction_end.errorMessage failure from the existing lead, a cause class with one step, and Cause: <raw>. The step is a typed CompactionFailureStep chosen by compactionFailureStep:

   • Provider causes go through describeProviderFailureForUser.
   • Overflow recovery that failed on a transient provider error (pi-ai isRetryableErrorMessage) says to send the message again; any other overflow-recovery failure says to start a new session or switch to a larger-context model.
   • "Nothing to compact" says no action is needed.
   • Rejections and cancellations that already name their step are passed through unchanged.

   No step names a slash command.

Item 4 (TUI-only slash commands in texts that also reach RPC/desktop) moved to a follow-up. Neutral wording would drop the working /login <provider> step for TUI users. The right fix is a typed action field that each client renders, which is a separate design.

Matched strings verified unchanged

• Provider is not configured:
• No credential slots available
• All credential slots are blocked until
• Compaction failed:
• Auto-compaction failed:
• Context overflow recovery failed:
• Nothing to compact
• OVERFLOW_RECOVERY_EXHAUSTED_MESSAGE

The resolver, credential classifier, overflow, retry and usage-account modules have no diff. One verdict changes on purpose: a compaction failure that wraps an account usage limit now names retry.fallbackChains, so isQuotaExhaustionMessage classifies it as quota (non-retryable) instead of retryable.

Tests

Tests pin machine values only: typed category and retryAt, the absence of httpStatus/code, the compactionFailureStep table, the leads, the raw-cause suffix, the overflow-retry signal, and that no compaction step names a slash command.