improvement(copilot): stop persisting tool-call result outputs in transcripts

[waleedlatif1]

Problem

Opening a Mothership task (copilot chat) could take many seconds — sometimes effectively hang. Verified against prod: a single persisted assistant message in copilot_messages.content can reach hundreds of MB, almost entirely inside contentBlocks[].toolCall.result.output (e.g. a get_workflow_logs / run_workflow result). The DB query is ~2 ms; the cost is detoasting that payload, shipping ~200 MB to the browser, and parsing it. 449 prod rows exceed 1 MB, totaling ~2.2 GB.

Why dropping output is safe

These outputs are dead weight on the Sim side:

• Not rendered — the chat thread shows only tool name/title/status (tool-call-item.tsx); the only component that renders result.output (generic-resource-content.tsx) is unwired.
• Not replayed to the model — the outbound copilot request (payload.ts) sends only the new message + chatId + context, never the transcript. The upstream copilot service owns conversation memory and retains the full results.

Change

Drop toolCall.result.output before persisting, keeping result.success/error and the tool metadata (id/name/state/params/display).

• stripToolResultOutput() in persisted-message.ts
• applied in messages-store.ts toRow — the universal write choke point (assistant turns, update-messages, fork, import, inbox)
• applied in loadCopilotChatMessages (lifecycle.ts) — pre-backfill rows return a small GET payload, so existing tasks load fast on read

Follow-up (separate, not in this PR)

A one-off backfill strips output from the 449 existing oversized rows to also reclaim the server-side detoast cost. Transform validated via dry-run on the worst row (1316→1316 blocks, 0 residual outputs); pending a write-capable DB credential.

Tests

Unit tests for stripToolResultOutput; write-path strip in messages-store.test.ts; read-path strip in lifecycle.test.ts. Biome + check-api-validation pass.

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[cursor]

PR Summary

Medium Risk
Changes what is stored in chat transcripts (drops tool outputs permanently on write); behavior is intentional and outputs are unused in UI/model replay, but operators lose stored tool payloads until a separate DB backfill.

Overview
Copilot transcripts no longer store bulky toolCall.result.output payloads in copilot_messages.content, which were slowing Mothership task loads when tool results (e.g. workflow logs) reached hundreds of MB.

A new stripToolResultOutput() keeps tool metadata plus result.success / error and drops only output. It runs on write in messages-store (toRow, covering append/replace and related paths) and on read in loadCopilotChatMessages so pre-backfill rows still return small API payloads. Unit tests cover the helper, persist paths, and lifecycle reads.

^{Reviewed by Cursor Bugbot for commit 0ced63b. Configure here.}

[greptile-apps]

Greptile Summary

This PR strips toolCall.result.output before persisting copilot messages to the database, fixing a serious performance issue where a single persisted assistant message could contain hundreds of MB of tool-call output that was bloating DB rows, causing slow task loads, and shipping unnecessary payload to clients.

• Adds stripToolResultOutput() in persisted-message.ts that drops output from each PersistedContentBlock's tool-call result while keeping success and error, using an identity-return optimization when nothing needs stripping.
• Applies the strip on both the write path (messages-store.ts toRow) and the read path (lifecycle.ts loadCopilotChatMessages) to handle pre-backfill rows already in the DB, with full unit test coverage for both paths.

Confidence Score: 5/5

Safe to merge — the change is narrowly scoped to dropping a field that is confirmed unused by the display layer and never replayed to the model.

The strip logic is null-safe, the identity-return optimization correctly handles the no-op case, and stripping is applied symmetrically on both write and read paths. Test coverage is thorough across unit, write-path, and read-path scenarios.

No files require special attention.

Important Files Changed

Filename	Overview
apps/sim/lib/copilot/chat/persisted-message.ts	Adds stripToolResultOutput(); logic is correct, null-safe (checks !result before typeof), returns original reference when unchanged.
apps/sim/lib/copilot/chat/messages-store.ts	Applies stripToolResultOutput in toRow(), covering both appendCopilotChatMessages and replaceCopilotChatMessages write paths.
apps/sim/lib/copilot/chat/lifecycle.ts	Applies stripToolResultOutput on the read path in loadCopilotChatMessages to handle pre-backfill bloated rows.
apps/sim/lib/copilot/chat/persisted-message.test.ts	Adds comprehensive unit tests for stripToolResultOutput covering stripping, error preservation, identity return, and multi-block messages.
apps/sim/lib/copilot/chat/messages-store.test.ts	Adds write-path strip tests for both append and replace operations, verifying output is absent from persisted rows.
apps/sim/lib/copilot/chat/lifecycle.test.ts	Adds read-path strip test for getAccessibleCopilotChatWithMessages, confirming output is absent from returned messages.

Sequence Diagram

sequenceDiagram
    participant C as Copilot Stream
    participant PM as persisted-message.ts
    participant MS as messages-store.ts
    participant DB as copilot_messages (DB)
    participant LC as lifecycle.ts
    participant Client as Browser

    C->>PM: buildPersistedAssistantMessage(result)
    Note over PM: redactSensitiveContent + mapContentBlock<br/>(result.output still present)
    PM-->>MS: PersistedMessage (with output)

    MS->>PM: stripToolResultOutput(message)
    Note over PM: drops output, keeps success/error<br/>returns same ref if nothing to strip
    PM-->>MS: PersistedMessage (output stripped)

    MS->>DB: "INSERT content = stripped message"
    Note over DB: rows written before backfill<br/>still carry output

    Client->>LC: loadCopilotChatMessages(chatId)
    LC->>DB: SELECT content FROM copilot_messages
    DB-->>LC: rows (may have legacy output)
    LC->>PM: stripToolResultOutput(row.content)
    Note over PM: no-op for new rows (identity return)<br/>strips output for legacy rows
    PM-->>LC: PersistedMessage (output stripped)
    LC-->>Client: PersistedMessage[] (lean payload)

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[waleedlatif1]

@greptile

[waleedlatif1]

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^{Reviewed by Cursor Bugbot for commit 0ced63b. Configure here.}