Tool calls execute successfully but are followed by a spurious "Your tool call was malformed and could not be parsed. Please retry."

Environment

• Claude Code, model: Opus 4.7 (1M context) — claude-opus-4-7[1m]
• Platform: macOS (darwin 25.5.0), shell: zsh
• Plugins / MCP active: oh-my-claudecode (OMC), context7, codex-cli, Notion MCP, plus a large set of deferred tools and project PreToolUse / PostToolUse hooks

Symptom

After most tool calls (Bash / Edit / Write), the assistant turn is immediately followed by a system message:

Your tool call was malformed and could not be parsed. Please retry.

However, the tool actually executed correctly — git commit/push/cherry-pick, gh queries, and file writes all produced normal output and took effect. The notice appears despite success.

Sometimes it is accompanied by [Request interrupted by user], and the conversation appears to stall, requiring me to type "continue" repeatedly to make progress.

Frequency

Persistent since ~2026-05-26 (yesterday), recurring on nearly every tool call.

Impact

The conversation looks like it disconnects / hangs, forcing repeated manual "continue". No data loss (work completes), but heavy friction.

Steps to reproduce (not fully isolated)

1. In a session with the above plugin/hook stack, run any Bash / Write / Edit tool call.
2. Observe the "malformed and could not be parsed" notice even though the call was valid and executed successfully.

Expected behavior

No spurious parse-failure notice when the tool call was valid and executed.

Suspected area (uncertain)

Tool-call parsing / streaming layer, or a hook/plugin interfering with tool-call serialization; possibly an interaction with the large deferred-tool / MCP set. Filing so others hitting the same can confirm.