[iFixRobots]

In some LINE groups and multi-person chats, every text sent from the bridge fails:

Failed to handle Matrix message  error="API error 400: {"code":10051,"message":"RESPONSE_ERROR","data":{"name":"TalkException","message":"TalkException","code":82,"reason":"specVersion does not match","parameterMap":null}}"

Code 82 is E2EE_RETRY_ENCRYPT. LINE keeps a Letter Sealing spec version on each chat's group key (specVersion in getLastE2EEGroupSharedKey). The LINE Chrome extension (3.7.2) reads it in unwrapGroupKey, encrypts with V1 when it is 1 and sends e2eeVersion set to that value. We already parse SpecVersion but never used it: group messages were always V2 with e2eeVersion: "2".

This stores the latest group key's spec version, encrypts V1 when it is 1, and sets e2eeVersion from the chunks we actually send. That also fixes the existing V2 → V1 fallback, which sent V1 chunks labelled as version 2. Fetched group shared key now logs spec_version.

Over the last 7 weeks, 14 chats for 13 users hit this, and no text was ever sent successfully in any of them. Reactions and plain-flow images in the same chats went through.

Before / after

Not run. It needs a chat whose group key is spec version 1, and I don't have one on a test account. Once deployed, spec_version in the logs and the next send in an affected chat will confirm it.

go build and go vet pass.

Tag @indent to continue the conversation here.

[indent]

Issues

No issues found.

CI Checks

All CI checks passed on e39baa8.

Review agents

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Passed (1)

• Indent Review Agent · No bugs found in the spec-version change.

Full results

Indent Review Agent

• Summary: No bugs found in the spec-version change.
• Last ran on commit: e39baa81
• Latest result

  {
    "summary": "No bugs found in the spec-version change.",
    "findings": []
  }