Agent stuck replaying the same user turn + “named a source file” gate, infinite Q&A loop

[justrach]

Symptom

The agent entered a dozens-of-turns loop answering the same user question.

Each replayed turn also injected a tool-use gate of the form: if a source path was named, the agent must read/edit that path before answering. Combined with turn replay, the agent kept read_file/codedb on the same docs and restating the same answer until the human interrupted.

Expected

After the question is answered from the named file, stop. Do not re-inject the same user question. The source-path gate should not fire on every subsequent turn when the prior turn already read (and, when needed, edited) that file.

Actual

The same user payload was replayed as a new turn many times (50+). Combined with the source-file gate, the agent kept:

1. calling read_file / codedb on the same spans
2. repeating the same short answer
3. getting the same question again

Why this is a harness bug

The user asked once. The session then replayed that turn plus a tool-use constraint that forced another read each time. That is session/prompt/turn scheduling, not the working repo.

Suggested fix

• Deduplicate consecutive identical user messages (or identical user+gate bundles) before injecting a new turn.
• The “named a source file → must read/edit” rule should be per unanswered mention, not re-applied after a successful read in the previous turn.
• If the gate must stay, fail closed after N identical loops and surface “stuck replay” to the user instead of burning the session.

Context

• Harness: Codegraff agent
• No secrets, credentials, or host details in this report (redacted from the original write-up)