fix: post-compaction stuck "working" status

[aterrylu]

Problem

Sessions that auto-compact on server-restart-resume get stuck at "working" / spinning forever in the dashboard. Terry hit this today after deploying a new server version: sessions restarted, several auto-compacted on resume, and even after compaction completed cleanly, the UI showed them as still working indefinitely.

Root cause

deriveStatus() for PostCompact unconditionally returned { status: "working" }:

case "PostCompact":
  return { status: "working", ...CLEAR_TOOL };

That assumed compaction only happens mid-turn (user-triggered /compact while agent is working), where the turn continues and Stop eventually fires → idle. But on auto-compaction during session resume, there is no active user turn — so no subsequent Stop event fires, leaving the status stuck at "working" forever.

The existing sticky-idle guard (#149) didn't catch it: before PostCompact, prev.status is "compacting" or "unknown" (fresh restart) — neither is sticky, so the bad transition passes through.

sequenceDiagram
    participant Server
    participant CC as Claude Code
    participant Hooks as hooks.ts

    Note over Server,Hooks: BEFORE (buggy)
    Server->>CC: spawn --resume <id>
    CC->>Hooks: SessionStart source=compact
    Hooks-->>Hooks: status = compacting
    CC->>CC: compact JSONL
    CC->>Hooks: PostCompact
    Hooks-->>Hooks: status = working ❌
    Note over Hooks: No turn → no Stop → stuck spinning

    Note over Server,Hooks: AFTER (fix)
    Server->>CC: spawn --resume <id>
    CC->>Hooks: SessionStart source=compact
    Hooks-->>Hooks: status = compacting, preCompactStatus = undefined
    CC->>CC: compact JSONL
    CC->>Hooks: PostCompact
    Hooks-->>Hooks: no baseline → fall back to "ready" ✓

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Solution

Track the pre-compact status on AgentState. Restore it on PostCompact. Fall back to "ready" when there's no baseline.

State machine changes:

• Save prev.status → preCompactStatus on entering "compacting" (skip when prev is "unknown" or already "compacting")
• On PostCompact, restore preCompactStatus — coerce tool_running / needs_input / error to "working" since those transient conditions don't survive the JSONL collapse
• Invariant: preCompactStatus is only set while status === "compacting". Cleared on any non-compacting exit (SessionEnd mid-compact, duplicate PostCompact, user-cancel via Stop) so the baseline can't leak across cycles
• Always clear currentTool / toolDetail on PostCompact defensively, independent of deriveStatus

Why "ready" fallback instead of "idle" or keeping "working":

• "idle" would trip the sticky guard and block subsequent tool events from transitioning → breaks mid-turn flows
• "working" is the original bug
• "ready" is non-sticky and represents "alive, awaiting input" accurately

Scenario	Before	After
Resume auto-compact (Terry's bug)	stuck "working"	→ "ready" ✓
Mid-turn /compact while working	"working" (lucky)	"working" (restored) ✓
Mid-tool /compact	"working" with stale tool	"working", tool cleared ✓
/compact during permission prompt	restored "needs_input" (stale prompt)	coerced to "working" ✓
/compact while idle	"idle" (sticky guard)	"idle" (unchanged) ✓
Mid-compact cancel (Stop)	baseline leaks to next cycle	baseline cleared ✓

Changes

• packages/server/src/routes/hooks.ts — add preCompactStatus field, save/restore logic in handler, staleness coercion, defensive tool-clear (+49/-7)
• packages/server/src/__tests__/hooks.test.ts — 6 new tests covering regression + invariants (+67/-6)

Testing

• 35/35 hook tests pass (6 new)
• Full server test suite: 252/252 pass
• biome check clean
• tsc --build clean
• /polish run: 3 review agents — all findings addressed (invariant tightening, staleness coercion, explicit CLEAR_TOOL, stronger test assertions)

Test plan

• Deploy to dashboard
• Verify no regression on mid-turn /compact (session continues working after compact)
• Simulate resume auto-compact: force a session near context limit, restart server, verify status shows "ready" (not spinning) after compaction

Risks

Low. All changes are internal to hooks.ts state derivation. Sticky-idle guard from #149 is untouched and remains the primary safety net. Rollback is trivial (single commit).

Related

• fix: sticky idle state prevents stale working status #149 (sticky idle) — adjacent fix, solves a different variant (late events overriding settled idle); this PR solves the mirror image (PostCompact transitioning to wrong state)

🤖 Generated with Claude Code

[nox-0x]

Clean fix. The preCompactStatus tracking is correct and the invariant (only set while status === "compacting") holds across all exit paths. Stale coercion for tool_running/needs_input/error is the right call — those states dont survive JSONL compaction. 6 new tests cover the surface well. LGTM.