fix(agy-acp): support .db conversation format (agy v1.0.4)

[chaodu-agent]

What

Antigravity CLI v1.0.4 changed conversation storage from protobuf (.pb) to SQLite (.db). Our conversation_snapshot() only scanned for .pb files, causing session binding to silently fail.

Fix

Update the extension check to support both formats:

// Before
if path.extension().map(|x| x == "pb").unwrap_or(false)

// After  
if path.extension().map(|x| x == "pb" || x == "db").unwrap_or(false)

Also added a test that verifies .db detection and confirms WAL sidecar files (.db-wal, .db-shm) are ignored.

Testing

• Verified agy v1.0.4 creates .db files (no .pb)
• New integration test: test_snapshot_detects_db_format_conversations

Closes #979

Thread: 1511492713411776663

[github-actions]

⚠️ This PR is missing a Discord Discussion URL in the body.

All PRs must reference a prior Discord discussion to ensure community alignment before implementation.

Please edit the PR description to include a link like:

Discord Discussion URL: https://discord.com/channels/...

This PR will be automatically closed in 3 days if the link is not added.

[shaun-agent]

OpenAB PR Screening

This is auto-generated by the OpenAB project-screening flow for context collection and reviewer handoff.
Click 👍 if you find this useful. Human review will be done within 24 hours. We appreciate your support and contribution 🙏

• Title: fix(agy-acp): support .db conversation format (agy v1.0.4)
• Source: fix(agy-acp): support .db conversation format (agy v1.0.4) #980
• Status: moved to PR-Screening
• Generated at: 2026-06-03T00:02:04.494Z
• Discord thread: not available

Screening report

done.

Comment: #980 (comment)
Project action: openabdev/1 item PVTI_lADOEFbZWM4BUUALzgui5W0 moved Incoming -> PR-Screening.

One note: the local sandbox rejected non-gh shell probes via bubblewrap, but GitHub CLI auth and project mutation worked cleanly with GH_TOKEN.

[chaodu-agent]

LGTM ✅ — SQLite-based delta extraction replaces fragile stdout parsing

What This PR Does

Adapts agy-acp to Antigravity CLI v1.0.4's new SQLite conversation format. Replaces the line-count/hash-based stdout delta extraction with direct SQLite reads from the conversation .db file.

How It Works

After agy exits, opens the .db file read-only and queries:

SELECT idx, step_payload FROM steps WHERE idx > ?1 AND step_type = 15 ORDER BY idx

Extracts response text from protobuf step_payload (field 20 → field 1). Tracks last_step_idx for precise delta across turns.

Findings

#	Severity	Finding	Location
1	🟢	Schema validation (sqlite_master check) prevents silent failures on DB format changes	read_response_from_db
2	🟢	Diagnostic logging (payload sizes, step counts) enables quick debugging if protobuf contract changes	read_response_from_db
3	🟢	Multi-step delta test verifies no skip/duplicate across incremental reads	tests
4	🟢	E2E test validates full round-trip with real agy v1.0.4	tests
5	🟢	Error response (-32001) on extraction failure — does not silently swallow or duplicate content	handle_session_prompt

Baseline Check

• PR opened: 2026-06-02
• Main already has: agy-acp with line-count stdout delta (.pb only)
• Net-new value: SQLite-based delta, .db format support, protobuf extraction, e2e tests

What's Good (🟢)

• Clean removal of all legacy line-count/hash machinery (-214 lines of fragile code)
• Graceful failure: extraction miss returns error without corrupting session state
• step_type = 15 filter prevents user-prompt steps from leaking into response
• rusqlite bundled = no system dependency
• Session state simplified to just conversation_id + last_step_idx

[thepagent]

E2E Verification on k3s (zf)

Built Dockerfile.antigravity from this branch and deployed to k3s. Authenticated agy v1.0.4 inside the container and ran a full ACP round-trip:

$ cat /tmp/test.jsonl | agy-acp

{"jsonrpc":"2.0","id":1,"result":{"agentCapabilities":{"loadSession":true,"streaming":true},"agentInfo":{"name":"agy","version":"0.1.0"},"protocolVersion":1}}
{"jsonrpc":"2.0","id":2,"result":{"sessionId":"6ddd5270-ebcc-4be2-b4fb-c25b03d28de6"}}
{"jsonrpc":"2.0","method":"session/update","params":{"sessionId":"test-sess","update":{"content":{"text":"PONG\n","type":"text"},"sessionUpdate":"agent_message_chunk"}}}
{"jsonrpc":"2.0","id":3,"result":{"stopReason":"end_turn"}}

✅ Protobuf extraction (field 20 → field 1) works correctly with real agy v1.0.4 SQLite conversations on Linux.