deepseek-ai/deepseek-harness · error · Error

seed event at index ${index} has seq ${snapshot.seq} (expect

Error message

seed event at index ${index} has seq ${snapshot.seq} (expected ${index}); seed must be contiguous from 0

What it means

Error "seed event at index ${index} has seq ${snapshot.seq} (expected ${index}); seed must be contiguous from 0" thrown in deepseek-ai/deepseek-harness.

Source

Thrown at packages/core/session/src/index.ts:526

    if (seed !== undefined) {
      // Validate the seed to the SAME invariants `append` enforces, so a
      // replay/fork (`ctx.sessions.create(id, { seed })`) cannot construct a
      // live log that no persistence backend could store: each event's `data`
      // must be JSON-serializable, and `seq` must be contiguous from 0 (the
      // `seq = log.length` contract the whole system relies on). Without this,
      // a bad seed would surface only later as a backend rejection or a silent
      // divergence between the live log and disk.
      for (const [index, source] of seed.entries()) {
        // The seed is a persistence/replay boundary: validate and detach the
        // complete event in one lossless-JSON pass.
        const snapshot = mode === 'restore' ? source : snapshotJsonValue(source)
        if (snapshot === undefined) {
          throw new Error(`seed event at index ${index} is not losslessly JSON-serializable`)
        }
        assertSessionEventEnvelope(snapshot, index)
        assertSupportedRequestHeader(snapshot.type, snapshot.data, `seed event at index ${index}`)
        if (snapshot.seq !== index) {
          throw new Error(`seed event at index ${index} has seq ${snapshot.seq} (expected ${index}); seed must be contiguous from 0`)
        }
        // A seed is accepted incrementally through the same transition as a
        // live append and a full-log fold. The candidate is planned before it
        // enters `log`, so a failure cannot partially mutate the surface.
        try {
          this.surfaceManager.validateNext(snapshot)
        } catch (error: unknown) {
          throw new Error(`invalid seed event at index ${index}: ${error instanceof Error ? error.message : 'invalid surface metadata'}`)
        }
        this.log.push(mode === 'restore' ? freezeRestoredObject(snapshot) : deepFreeze(snapshot))
      }
    }
    this.firstLiveSeq = this.log.length
    this.header = restoredHeader ?? snapshotSessionHeader(id, header)
    // Appended here so the marker is already in `events` when a backend
    // captures the creation seed: no load-time write. Re-marking is skipped
    // because a cold session is resumed on first touch, so repeatedly opening
    // one must not grow its log per open.

View on GitHub (pinned to b150a551b8)

Solutions

1. Renumber the seed events to contiguous seq values starting at 0.

When it happens

Trigger: Thrown at packages/core/session/src/index.ts:526 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of deepseek-ai/deepseek-harness@b150a551b8 (2026-08-24). Data as JSON: /api/errors/4eaf47a6b3e57ca9. Report an issue: GitHub.