redact encrypted_content in traffic captures

[rikbrown]

Problem

Codex server-side compaction returns an opaque encrypted_content blob, which the proxy replays as a compaction input item on every later turn. With CCP_TRAFFIC_LOG=1 that blob is written to disk verbatim.

To be clear about severity: the blob is ciphertext we cannot read locally, so this is not a plaintext leak. But it is a large, replayable handle to a whole conversation's context, and because it is re-sent every turn it accumulates across a session's captures.

image_url and Anthropic source.data already have explicit arms in redact_traffic for the same reason — bulk conversation payload does not belong in a debug capture. This applies the existing precedent to encrypted_content.

Fix

A new arm in redact_traffic_with_depth, next to the source.data case, routing the value through the existing redact_traffic_value so it becomes [redacted len=N]. Blob size stays visible, since that is genuinely useful diagnostic information.

Not added to REDACT_KEYS, for two reasons:

1. REDACT_KEYS is shared with the structured logger via logging::redact_value, which is only ever called on the fields map in Logger::emit. No body, input item, or event value reaches the logger, so adding the key there would be a no-op for logging.
2. REDACT_KEYS is a credential list. This is bulk payload, which belongs with the image_url / source.data arms.

Reasoning items carry the same key and are covered by the same arm.

Scope — what this does not cover

This covers 020-upstream-request (write_json) and the 040/050 per-event JSON captures (write_json_event).

It does not cover the raw 032-upstream-response-body.sse capture on the Codex HTTP and WebSocket paths (client.rs, websocket.rs), which is written with write_bytes and bypasses redaction entirely. The blob still persists there. Fixing that means either re-serialising parsed events or a text-level scrub of the SSE, which felt like a separate change — happy to follow up if you'd prefer it in one go.

Providers that assemble upstream_sse from StreamTrafficCapture::upstream_event (grok, opencode) are already redacted, since those frames go through write_json_event. Codex is the one path that dumps raw bytes.

Verification

• redact_traffic_strips_compaction_encrypted_content — a compaction item in a request body; asserts the blob is replaced by [redacted len=N], the gAAAAA prefix is gone, and type, message text and model survive
• redact_traffic_strips_reasoning_encrypted_content_in_events — same for a reasoning item inside response.output_item.done
• cargo clippy --all-targets -- -D warnings clean, cargo fmt --check clean, full suite green

🤖 Generated with Claude Code

[raine]

Thanks for the redaction fix! Merged, including the reasoning-signature capture case.