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fix: strip orphaned tool_calls from preserved assistant message during compaction

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After context compaction, the preserved last assistant message retained
its structured tool_calls field, but the corresponding tool_result was
summarized away. This created orphaned tool_use blocks that violated
the Anthropic API constraint: 'Each tool_use block must have a
corresponding tool_result block in the next message', causing 400 errors.

Primary fix: clear tool_calls from the preserved assistant message in
extract_preserved_messages(). The tool call was already executed and
its result is captured in the summary.

Defense-in-depth: added strip_orphaned_tool_use() post-processing in
Anthropic convert_messages() to detect and strip any orphaned tool_use
blocks before they reach the API.

Added 7 tests: 3 unit tests for compaction stripping, 3 unit tests for
Anthropic orphan detection, 1 integration test reproducing the exact
bug scenario from the h3 session.
This commit is contained in:
Dhanji R. Prasanna
2026-02-11 15:22:03 +11:00
parent d3f0112f46
commit d61be719c2
4 changed files with 506 additions and 4 deletions
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analysis/memory.md
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@@ -1,5 +1,5 @@
# Workspace Memory
> Updated: 2026-02-10T21:08:38Z | Size: 27.8k chars
> Updated: 2026-02-11T03:39:03Z | Size: 29.0k chars
### Remember Tool Wiring
- `crates/g3-core/src/tools/memory.rs` [0..5000] - `execute_remember()`, `get_memory_path()`, `merge_memory()`
@@ -442,4 +442,14 @@ Makes tool output responsive to terminal width - no line wrapping, with 4-char r
- `crates/g3-core/src/context_window.rs` [107..109] - `add_message_with_tokens()` preserves messages with `tool_calls` even if content is empty
- `crates/g3-core/src/streaming_parser.rs` [339] - `process_chunk()` preserves tool call `id` from provider
**Bug fixed**: Agent would stop mid-task because native tool calls were stored as inline JSON text in `Message.content`. When sent back to Anthropic API via `convert_messages()`, they went as plain text instead of structured `tool_use`/`tool_result` blocks. The model would occasionally get confused and emit text describing what it wanted to do instead of invoking the tool mechanism.
**Bug fixed**: Agent would stop mid-task because native tool calls were stored as inline JSON text in `Message.content`. When sent back to Anthropic API via `convert_messages()`, they went as plain text instead of structured `tool_use`/`tool_result` blocks. The model would occasionally get confused and emit text describing what it wanted to do instead of invoking the tool mechanism.
### Compaction Tool Call Stripping Fix (2026-02-11)
- `crates/g3-core/src/context_window.rs` [339..355] - `extract_preserved_messages()` now strips `tool_calls` from preserved last assistant message
- **Root cause**: After compaction, preserved assistant message retained structured `tool_calls` but the corresponding `tool_result` was summarized away → orphaned `tool_use` blocks → Anthropic 400 error
- **Fix**: Clear `msg.tool_calls` in `extract_preserved_messages()` before returning
- Messages with only tool_calls and empty content are dropped by `add_message_with_tokens()` empty check
- `crates/g3-providers/src/anthropic.rs` [369..435] - `strip_orphaned_tool_use()` defense-in-depth
- Post-processing pass in `convert_messages()` detects orphaned `tool_use` blocks (no matching `tool_result` in next message)
- Strips orphaned blocks with warning, adds placeholder text if message becomes empty
- Tests: `test_compaction_strips_tool_calls_from_last_assistant`, `test_compaction_drops_assistant_with_only_tool_calls_no_text`, `test_compaction_preserves_normal_assistant_message` (unit), `test_strip_orphaned_tool_use_*` (anthropic), `test_compaction_strips_structured_tool_calls` (integration)