Anthropic is strict about replaying the latest assistant turn once it
contains signed or redacted reasoning. We were still mutating that turn
in a few Coder-owned places: dropping empty reasoning blocks on replay,
rewriting provider-tool history during sanitization, and in the worst
case sending a prompt we already knew Anthropic would reject.
This patch keeps the latest signed assistant immutable through Coder's
replay and sanitization paths, preserves empty signed or redacted
reasoning anywhere Coder owns the ledger, and fails before the provider
call if the prompt is still unsafe.
It also bumps the existing `coder/fantasy` `coder_2_33` fork that `main`
already uses to the commit containing coder/fantasy#35. These fixes have
also been upstreamed to charmbracelet/fantasy.
Closes CODAGT-409.
When OpenAI's Responses API returns `Previous response with id ... not
found` for a chained turn, classify it as a `ChainBroken` retry, clear
`previous_response_id`, exit chain mode, reload full history, and let
`chatretry` retry. Self-heals chats whose anchor was poisoned before
#25074 stopped truncated streams from being persisted as a successful
turn with a stored response id.
The new state is exposed via the existing
`coderd_chatd_stream_retries_total` counter as a
`chain_broken="true"|"false"` label. Aggregating queries (`sum`, `rate`
over `provider`/`model`/`kind`) keep working without changes; raw-series
matchers without aggregation will now see two series per `(provider,
model, kind)` where they previously saw one. The metric is internal-only
so the blast radius should be small, but if you have dashboards that
index by exact label matchers without aggregation they will need an
extra `sum` or an explicit `chain_broken` selector.
> 🤖 This PR was created with the help of Coder Agents, and was reviewed by a human 🧑💻
Ethan