Python SDK cannot resume a persisted session after restart — session/prompt always creates and hits "id collision", existing conversations error on the next turn

[zl5747]

Summary

Python SDK (0.1.1rc1) + --profile sdk: after a harness restart, a turn on an existing session id fails with finish_reason: error and no output:
session "" already has a persisted log on disk that does not match this live session (id collision)
Root cause: the SDK JSON-RPC server always calls agents.create() (getOrCreateSession) and never resumes. The persistence layer's createCore rejects ids with an existing log ("load/resume it instead of creating"), and the SDK protocol (session/prompt) exposes no resume path. So any programmatic client loses all conversations on restart.

Reproduction

Run turn 1 with session_id="test-001", close the harness, start a new one (same dsh_home), run turn 2 with the same id:

• turn 1 → works, final_response '记住了'
• turn 2 → final_response '', finish_reason 'error' (turn/end: id collision, code UNKNOWN)
  In-process continuation (same harness + same id) works; only cross-restart resume fails.

Expected

session/prompt should resume the persisted session when a log exists (the persistence layer already implements resume; the SDK just never calls it), or expose an explicit resume/open method, or at least return a recoverable error code.

Workaround

Client-side history replay: on first turn after restart, clear the stale log and feed the conversation history as content blocks. Restores context but loses harness-internal state (tool results, summaries).

Related: #466, #483, #387 (session persistence across restarts, web-host perspective). Reproduced 2026-08-29, SDK 0.1.1rc1 / dsh 0.1.1-rc.2.

[denial123789]

I documented the restart boundary as an Agent-first runbook: same-ID in-process continuation vs cross-restart id collision, evidence capture, lossy history replay in a copied profile, and acceptance checks that preserve the original log. Guide: https://github.com/sandbaseai/deepseek-harness-handbook/blob/main/docs/en/getting-started/python-sdk.md#restart-recovery-sessionprompt-is-not-a-resume-operation

[173787247]

上下文 / Compact（「Python SDK cannot resume a persisted session after restart — session/prompt always creates and hits "id collision", existing conversations error on the next turn」）

一上来就 compact，多半是 窗口读错 或压缩模型 maxTokens 太小。

1. 把 compaction 输出上限加大，重启并用新会话。
2. 大段工具输出落地成文件，prompt 里只留路径。
3. 先关优化/直通一次，确认是不是压缩器在空转。

error on the next turn