fix(replay): surface compressed observation content in replay detail

[xianfengpolo]

Problem

The Replay tab in the viewer steps through session events correctly, but the detail panel is empty for every event — only a label and timestamp are shown.

Root Cause

rawFromCompressed() in src/functions/replay.ts was the compatibility shim between the compressed storage format and the RawObservation shape expected by projectTimeline. It had two bugs:

1. Wrong hookType for all events — hardcoded "post_tool_use" regardless of observation type, so conversation events never rendered as prompts.
2. Tool fields discarded — toolName, toolInput, and toolOutput were all undefined. The compressed format does retain this data under different field names (title = tool name, subtitle = raw input, narrative = combined output), but the shim never mapped them.

Since the runtime compresses every observation (both live-capture and jsonl-import paths), every replay session was affected.

Fix

Branch on obs.type in rawFromCompressed:

• "conversation" → hookType: "prompt_submit", userPrompt ← narrative
• everything else (command_run, file_read, …) → hookType: "post_tool_use", toolName ← title, toolInput ← subtitle, toolOutput ← narrative

assistantResponse stays undefined — the compression pass doesn't preserve a separate assistant-response field.

The function is also exported (it was previously unexported) so it can be directly unit-tested. Precedent: src/cli/doctor-diagnostics.ts does the same for its pure helpers.

Tests

Four new test cases added to test/replay.test.ts in the new rawFromCompressed describe block:

Test	Verifies
command_run with subtitle	hookType, toolName, toolInput, toolOutput all populated
conversation	hookType:"prompt_submit", userPrompt populated, tool fields undefined
tool obs with no subtitle	gracefully maps toolInput to undefined without throwing
end-to-end via projectTimeline	TimelineEvent carries toolName/toolInput/toolOutput/body

Test Files  1 passed (1)
     Tests  17 passed (17)   ← 13 original + 4 new
  Duration  235ms

TypeScript typecheck (npx tsc --noEmit): zero errors in changed files (pre-existing errors in unrelated files are unchanged).

Checklist

• Reproduces the bug (empty detail panel for every event)
• All 17 replay tests pass
• No new TypeScript errors introduced
• Comments explain the why (compression-drops-raw regression context)

Summary by CodeRabbit

• Bug Fixes

  • Timeline and replay views now show the correct details for conversation and tool events.
  • Prompt submissions and tool runs are mapped to the right display fields, so event content is no longer missing.
  • Optional event details are handled more gracefully, avoiding blank or incomplete timeline entries.

• Tests

  • Added coverage for replay-to-timeline conversion to verify the expected event content appears end to end.

[vercel]

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[coderabbitai]

📝 Walkthrough

Walkthrough

The rawFromCompressed function in replay.ts is now exported and rewritten to correctly translate CompressedObservation into RawObservation, branching on observation type to produce prompt submission or tool events with proper field mapping. Corresponding tests were added.

Changes

rawFromCompressed Mapping Fix

Layer / File(s)	Summary
Type-aware observation mapping src/functions/replay.ts	rawFromCompressed is exported and now branches on obs.type: conversation observations map to hookType: "prompt_submit" with userPrompt from narrative; other observations map to hookType: "post_tool_use" with toolName/toolInput/toolOutput from title/subtitle/narrative.
Regression and integration tests test/replay.test.ts	Adds rawFromCompressed imports, a makeCompressed factory, and tests validating tool vs conversation mapping, missing subtitle handling, and timeline event integration via projectTimeline.

Estimated code review effort: 2 (Simple) | ~10 minutes

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly summarizes the main fix: exposing compressed observation content in replay detail.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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[coderabbitai]

🧹 Nitpick comments (1)

src/functions/replay.ts (1)

49-66: 📐 Maintainability & Code Quality | 🔵 Trivial | 💤 Low value

Trim the WHAT-explaining comment.

Lines 60-64 restate the mapping logic that's already self-evident from the code (isConversation ternaries). Per path instructions, prefer clear naming over comments explaining what the code does; keep only the rationale/history if useful.

As per path instructions: "In TypeScript source code, avoid code comments explaining WHAT — use clear naming instead."

🤖 Prompt for AI Agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

In `@src/functions/replay.ts` around lines 49 - 66, The block comment above
replayObservation is too detailed about WHAT the code does and duplicates the
branch logic already shown by the isConversation ternaries. Trim it down by
removing the step-by-step mapping bullets and keep only the brief
rationale/history for why the shim exists, so the function name and branching
remain the primary documentation.

Source: Path instructions

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Nitpick comments:
In `@src/functions/replay.ts`:
- Around line 49-66: The block comment above replayObservation is too detailed
about WHAT the code does and duplicates the branch logic already shown by the
isConversation ternaries. Trim it down by removing the step-by-step mapping
bullets and keep only the brief rationale/history for why the shim exists, so
the function name and branching remain the primary documentation.

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ℹ️ Review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: b2f35464-7af5-49b2-a76f-ebc186c1035e

📥 Commits

Reviewing files that changed from the base of the PR and between 93ae9bc and 2e6dfc6.

📒 Files selected for processing (2)

• src/functions/replay.ts
• test/replay.test.ts