The ACP spec defines session/update content as a ContentBlock object
({type, text}) but we decoded it as a string. This dropped every
agent_message_chunk and left prompt responses empty. E2E against the
real opencode acp binary surfaced the bug.
- internal/acp/messages.go: add ContentBlock struct; Update.Content is
now ContentBlock.
- internal/acp/client.go: handleNotification extracts Text when
Content.Type == "text"; other types are logged at debug and dropped.
- internal/acp/client_test.go: NDJSON framing test sends content as a
ContentBlock object and reads .Text.
- README.md: document /acp/* routes + CODESPACE_OPENCODE_ARGS env.
Verified end-to-end: POST /acp/prompt returns text="Hi there!", 4
messages in history (1 user + 3 agent chunks), 0 invalid session/update
log entries.
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tao.chen