Follow-on to the session-stability fix. "Per source" already made the
prefix cache hit, but it puts every conversation into one upstream session.
Using the client's own session id is not possible: capturing real agent
traffic (tcpdump on 127.0.0.1:8081) shows generic OpenAI clients send NO
session identifier at all — no user / session_id / conversation_id /
metadata in the body, and no session header (only X-Stainless-* plus
User-Agent: pi). The x-opencode-session the Go endpoint asks for is an
OpenCode native-client concept that a generic client cannot forward.
Since history is replayed every turn, the FIRST user message is invariant
for the life of a conversation, so it is used as the conversation
fingerprint. The session becomes stable within a conversation and distinct
across conversations; requests with no user message fall back to per-source
stability.
Measured through the gateway (same 5.7k-token prompt): 2nd call
cached_tokens=5504, and an unrelated conversation gets its own session.
Test: TestOpenCodeSessionIsStableForCache covers same-conversation
stability, cross-conversation separation, per-request request ids and the
sessionless fallback.
The opencode adapters derived x-opencode-session from meta.timestamp, i.e. a
brand new session on every request. The upstream prefix cache is
session-scoped, so no request could ever hit it, and the cache fields the
endpoint does report (prompt_tokens_details.cached_tokens,
prompt_cache_hit_tokens/prompt_cache_miss_tokens) always came back 0/absent.
Measured against the live endpoint, same 6032-token prompt:
fixed session id -> 2nd call: hit 5888, miss 144
rotating session id -> every call: hit 0, miss 6032
Fix: derive the session from the source name (stable), matching how
x-opencode-project is already derived. x-opencode-request stays unique per
request — it is only a request identifier, not part of the cache key.
Applied to both opencodego and opencodezen.
Through the gateway the same prompt now reports, on the 2nd call:
details={'cached_tokens': 5888} hit=5888 miss=144 (non-streaming)
prompt_tokens_details={'cached_tokens': 5888} (streaming)
Test: TestOpenCodeSessionIsStableForCache asserts the session is stable
across requests for one source while the request id differs.
v1.5.4 stopped stripping reasoning_content, which fixes clients that send
it — but most agent clients (pi included) never store or replay their
reasoning, keeping only the tool call. OpenCode Go validates the field on
any assistant turn that carries tool_calls and rejects the whole request:
400 invalid_request_error: The `reasoning_content` in the thinking mode
must be passed back to the API.
Verified against the live endpoint that an EMPTY string satisfies the
check, so the adapter now fills in "" when a tool-calling assistant turn
has no reasoning_content. Nothing is fabricated: the reasoning shown to
the client is still exactly what the upstream returned for that turn.
Measured: with a tool_call + tool_result history and no reasoning_content,
all 25 configured Go models returned 400 before and all 25 answer
correctly now.
Test: TestOpenCodeGoVsZenReasoning also pins that a plain assistant turn
(no tool calls) must NOT gain the field.
Zen (https://opencode.ai/zen/v1) and Go (https://opencode.ai/zen/go/v1)
are different services with different requirements, and one shared adapter
could not satisfy both.
The decisive difference is reasoning_content:
* OpenCode Go runs thinking models and REQUIRES the assistant turn's
reasoning_content to be echoed back. The shared adapter stripped it
(msg.reasoning_content = nil), so every replay of a thinking turn
failed with:
400 invalid_request_error: The `reasoning_content` in the thinking
mode must be passed back to the API.
Reproduced directly: the same request with reasoning_content -> 200,
without -> 400. That is why the Go tier never worked in an agent loop.
* The Zen free pool must not receive it, so it keeps stripping.
Both adapters keep the earlier fixes they share (never drop an assistant
turn carrying tool_calls; send stream_options only when streaming; role
whitelist; multimodal strip) and the opencode client fingerprint headers —
the Go endpoint additionally REQUIRES x-opencode-session, which the
adapter already sends.
config: localzen -> opencodezen, gozen -> opencodego.
Verified: all 25 gozen models answer correctly through the gateway with a
thinking + tool_call + tool_result history (was 0/25 before), streaming
included; the Zen free models still pass.
Test: TestOpenCodeGoVsZenReasoning pins the Go-keeps / Zen-strips split.
OpenCode Go (and other strict OpenAI-compatible upstreams) reject a
non-streaming request that carries stream_options with
"stream_options should be set along with stream". The adapter attached it
unconditionally, so every non-stream call through the opencode adapter
failed on those upstreams.
Verified against OpenCode Go: 25/25 configured models now pass a real
completion through the gateway (they previously 400'd).
Test: TestOpenCodeStreamOptionsOnlyWhenStreaming (absent when
non-streaming, include_usage present when streaming).
Three related forwarding defects found by auditing every adapter with a
tool-calling replay (assistant turn with content:[] + tool_calls).
1) content:[] -> content:{} (all 12 openai-adapter sources, plus
deepseek/trae/sensenova/agentrouter/github/groq/kimicode/mistral)
Lua adapters json.decode the request and re-encode it, and an empty Lua
table is indistinguishable from an empty JSON array — the encoder emits
{} for both. Agent clients serialise a tool-calling assistant turn with
no text as content:[], so every pass-through adapter rewrote it to
content:{} — not valid OpenAI (content is string|array|null). Verified
against a live upstream: content:[] produced "400 invalid arguments"
while content:"" was accepted.
Fixed once at the decode boundary (types.ChatMessage.UnmarshalJSON):
empty-array content normalises to "" and an empty tool_calls array is
dropped, so every adapter — including future ones — sees a valid shape.
2) gemini dropped tool_calls and never emitted functionCall /
functionResponse; the tool role also stayed as an invalid role inside
contents and system was not moved to systemInstruction.
3) ollama copied only role/content, dropping tool_calls and the call
attribution entirely (it needs tool_name, not tool_call_id).
Test: TestAdaptersPreserveToolCalls asserts, for every adapter, that the
call id (or function name where the wire format has no id), the function
name, the tool result and the trailing user turn all survive, plus a
negative control for plain text.
